阅读说明：本技术 高压阻抗组件 (High-voltage impedance component ) 是由 迈克尔·H·斯塔尔德 塞巴斯蒂安·埃格特-黎克特 雷纳·方拉特 马克·格雷弗曼 延斯·魏克霍 于 2018-06-13 设计创作，主要内容包括：本发明公开了用于分压器中的阻抗组件(2),所述阻抗组件用于感测在电网中分配电能的电力承载导体的至少1kV对地的AC电压。所述阻抗组件包括a)印刷电路板(131),所述印刷电路板包括一个或多个电介质板层(210,215,220),b)外部可触及的高压触点(100),c)外部可触及的低压触点(110),所述低压触点与所述高压触点间隔开至少30mm,以及d)至少两个分压电容器(91),所述至少两个分压电容器串联连接在所述高压触点和所述低压触点之间,并且能够作为所述分压器的高压侧操作。每个分压电容器具有：由导电区域(301,302,303,304,305,306)形成的两个电极,所述导电区域布置在特定电介质板层的相对表面部分上；以及电介质,其包括其上布置有所述电极的所述特定电介质板层的一部分。所述阻抗组件可包括电阻器层,而不是所述分压电容器。(An impedance assembly (2) for use in a voltage divider for sensing an AC voltage of at least 1kV to ground of a power carrying conductor that distributes power in an electrical network is disclosed. The impedance assembly includes a) a printed circuit board (131) including one or more dielectric board layers (210,215,220), b) an externally accessible high voltage contact (100), c) an externally accessible low voltage contact (110) spaced apart from the high voltage contact by at least 30mm, and d) at least two voltage dividing capacitors (91) connected in series between the high voltage contact and the low voltage contact and operable as the high voltage side of the voltage divider. Each voltage dividing capacitor has: two electrodes formed of conductive regions (301,302,303,304,305,306) disposed on opposing surface portions of a particular dielectric slab layer; and a dielectric comprising a portion of the particular dielectric slab layer on which the electrode is disposed. The impedance component may include a resistor layer instead of the voltage dividing capacitor.)

1. Impedance assembly (1,2,3,4,5) for use in a voltage divider (50) for sensing an AC voltage of at least 1kV to ground of a power carrying conductor (10) distributing power in a national electrical network, wherein the impedance assembly comprises

a) A printed circuit board (130,131) comprising one or more dielectric slab layers (209,210,215,220),

b) an externally accessible high voltage contact (100),

c) an externally accessible low voltage contact (110), wherein any externally accessible portion of the low voltage contact is spaced from any externally accessible portion of the high voltage contact by a geometric distance (D) of at least 30mm, and

d) at least two voltage dividing capacitors (90,91) electrically connected in series between the high voltage contact and the low voltage contact and operable as a high voltage side (60) of the voltage divider,

wherein each voltage dividing capacitor has

-two electrodes formed by opposing conductive areas (201,202,205,301,302,303,304,305,306) arranged on opposing surface portions of a particular dielectric slab layer of the one or more dielectric slab layers,

-a dielectric arranged between the electrodes and comprising a portion of the particular dielectric slab on which the electrodes are arranged.

2. The impedance assembly according to claim 1, wherein the at least two voltage dividing capacitors (90,91) are electrically connected in series between the high voltage contact (100) and the low voltage contact (110), such as to provide a combined capacitance of at least 10 picofarads.

3. The impedance assembly according to any one of the preceding claims, comprising a total of six voltage dividing capacitors (90,91) electrically connected in series between the high voltage contact (100) and the low voltage contact (110), such as to provide a combined capacitance of at least 10 picofarads, and operable as the high voltage side (60) of the voltage divider (50) between the low voltage and the high voltage of the power carrying conductor (10),

wherein each voltage dividing capacitor has: two electrodes formed from opposing conductive regions (201,202,205,301,302,303,304,305,306) disposed on opposing surface portions of a particular dielectric slab layer of the one or more dielectric slab layers; and a dielectric disposed between the electrodes and comprising a portion of the particular dielectric slab on which the electrodes are disposed.

4. The impedance assembly according to any of the preceding claims, wherein the at least two voltage dividing capacitors (90,91) are electrically connected in series between the high voltage contact (100) and the low voltage contact (110), such as to provide a combined capacitance of at least 50 picofarads.

5. The impedance assembly of any one of the preceding claims, wherein the printed circuit board (131) is a multilayer printed circuit board, and wherein at least two of the conductive areas (302,303,306) are arranged inside the printed circuit board.

6. An impedance assembly according to any of the preceding claims, wherein the printed circuit board (130,131) is a ceramic PCB.

7. The impedance assembly of any one of the preceding claims wherein at least one of the dielectric slab layers (209,210,215,220) comprises a ceramic material.

8. An impedance assembly according to any preceding claim, wherein each dielectric slab layer (209,210,215,220) comprises a ceramic material.

9. The impedance assembly of any of the preceding claims, wherein the impedance assembly has an elongated shape and a length of 30 centimeters or less.

10. Impedance assembly (3,5) according to any of the preceding claims, wherein at least a part of the impedance assembly is embedded in a non-conductive encapsulation material (230).

11. The impedance assembly (5) of claim 10 wherein an outer surface of the encapsulation material (230) comprises

-a first surface area (350) covered with a conductive layer (400) for connection to a high voltage;

-a second surface area (360) covered with an electrically conductive layer (410) for connection to an electrical ground; and

-a third surface area (370), electrically insulating and free of an electrically conductive layer, arranged between the first surface area (350) and the second surface area (360) for insulating the first surface area from the second surface area.

12. An impedance assembly (6) for use in a voltage divider (50) for sensing an AC voltage of between 6kV and 175kV of an inner conductor (10) of a power cable (20) distributing power in an electrical grid,

wherein the impedance assembly has an elongated shape defining a first end portion (180) and an opposite second end portion (190) for being received in a longitudinal cavity (280) of an elastic sleeve (260) for insulating the power cable, and wherein the impedance assembly comprises

a) A substrate (130) on which the substrate is mounted,

b) a high voltage contact (100) arranged at the first end portion for current connection to the inner conductor,

c) a low voltage contact (110,111) arranged at the second end portion at a distance of at least 12cm from the high voltage contact for electrical connection to a low voltage of 10 volts or less, an

d) A resistor layer (240) disposed on an inner or outer surface of the substrate and extending between the first and second end portions, electrically connected in series between the high and low voltage contacts, such as to provide a resistance of at least 50M Ω,

wherein the resistor layer is operable as a high voltage side (60) of the voltage divider between the low voltage and a high voltage of the inner conductor.

13. The impedance assembly (6) of claim 12, wherein the resistor layer (240) extends longitudinally at least 100 mm.

14. The impedance assembly (6) according to claim 12 or 13, further comprising a second resistor layer (250) electrically connected in series with the first resistor layer (240), operable as a low voltage side (70) of the voltage divider (50), for sensing a voltage of the inner conductor (10).

15. An impedance assembly (6) for use in a voltage divider (50) for sensing an AC voltage of between 6kV and 175kV of an inner conductor (10) of a power cable (20) distributing power in an electrical grid,

wherein the impedance assembly has an elongated shape defining a first end portion (180) and an opposite second end portion (190) for being received in a longitudinal cavity (280) of an elastic sleeve (260) for insulating the power cable, and wherein the impedance assembly comprises

a) A substrate (130) on which the substrate is mounted,

b) a high voltage contact (100) arranged at the first end portion for current connection to the inner conductor,

c) a low voltage contact (110,111) arranged at the second end portion at a distance of at least 12cm from the high voltage contact for electrical connection to a low voltage of 10 volts or less, an

d) A plurality of impedance elements disposed on an inner or outer surface of the substrate and extending between the first and second end portions, electrically connected in series between the high and low voltage contacts, such as to provide a resistance of at least 50M Ω, wherein the voltage divider is mixed such that one divider impedance element is of one type and the other divider impedance element is of a different type,

one of the voltage dividing impedances is operable as a high voltage side (60) of the voltage divider between the low voltage and high voltage of the inner conductor.

16. Sensing a cable accessory (500), comprising

a) Cable termination comprising an elastic sleeve (260) for electrically insulating a power carrying conductor (10) of an electrical power cable (20), the sleeve having a longitudinal cavity (280) for accommodating an impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 15, and

b) the impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 14, arranged in the cavity (280) of the sleeve.

17. Sensing a cable accessory (500), comprising

a) Cable plug comprising an elastic sleeve (260) for electrically insulating a power carrying conductor (10) of an electric power cable (20), the sleeve having a longitudinal cavity (280) for accommodating an impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 15, and

b) the impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 14, arranged in the cavity (280) of the sleeve.

18. Kit of parts for assembling a sensing cable accessory (500) according to claim 15 or claim 16, the kit comprising

a) An elastic sleeve (260) for electrically insulating a power carrying conductor (10) of an electrical power cable (20), the sleeve having a longitudinal cavity (280) for accommodating an impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 15, and

b) impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 14.

19. Power network for distributing energy in an electrical network, comprising a power carrying conductor (10) and a voltage divider (50) connected to the power carrying conductor for sensing an AC high voltage of the power carrying conductor, the voltage divider comprising an impedance assembly (1,2,3,4,5,6) according to any one of claims 1 to 15.

Background

Medium voltage power cables transmit power at elevated voltages, typically alternating current ("AC") voltages of 1 kilovolt ("kV") or more, to ground. The voltage of the high voltage power cable is even higher. In both types of cables, the peak voltage may occur at a voltage of about 75kV or up to 175kV or even 194 kV. In the case of voltage dividers being used as elements of voltage sensors to sense the voltage of such cables, these voltage dividers must be able to accommodate such peak voltages without being destroyed.

Voltage dividers for sensing the voltage of the inner conductor of HV/MV power cables are known, for example from german patent application DT 2439080 a1 or DE 3702735 a 1. The voltage divider may be formed by a plurality of resistors, capacitors or inductors. In this disclosure, resistors, capacitors, and inductors are collectively referred to as impedance elements or impedances.

The voltage sensor may advantageously be accommodated in a cable termination or a detachable connector such as a cable plug. Some of these terminals and plugs include an expandable or collapsible tubular sleeve of insulating material having a passage in which an end of the cable can be received. A portion of the voltage sensor (e.g., a voltage divider) may be placed into the cavity of the insulative sleeve adjacent to the channel. Such an arrangement provides the following advantages: the insulating material of the sleeve may also serve to insulate the voltage divider and allow shorter wires connecting the voltage divider to the inner connector of the cable.

The withstand voltage of a single capacitor or a single resistor is usually lower than the above-mentioned 1 kV. Thus, conventionally, a larger number of discrete impedances or impedance elements are electrically connected in series to form a voltage divider between the high voltage and ground, such that the voltage drop across each impedance is sufficiently low to avoid discharge. A large number of impedance elements may have an impact on the manufacturing cost of such a voltage divider chain.

In the case of a voltage divider of a voltage sensor accommodated in an insulating sleeve of a terminal or cable plug, the geometric length of the sleeve constitutes a limitation on the geometric length of the voltage divider. Typical MV cable terminations have a length of 30 centimeters (cm) to 50cm, as measured along the cable. Therefore, if the voltage divider is to be accommodated in a terminal, the length of the voltage divider should not exceed this length. One end of the voltage divider is arranged close to the high voltage of the inner conductor, while the opposite end is close to the low voltage, mostly grounded. Therefore, the voltage of the inner conductor, i.e. at least 1kV and at most 175kV, needs to be divided to zero volts (electrical ground) or almost zero volts over this geometrical length. In order to reduce the risk of discharges between the high voltage end of the voltage divider and its low voltage end, the exposed contact of the first impedance element of the medium or high voltage divider connected to the inner conductor is advantageously arranged geometrically as far as possible from the exposed contact of the last impedance element of the voltage divider, which is connected to ground.

In the case where high-precision measurement of the voltage of the inner conductor is required, it is considered that commercially available capacitors and resistors exhibit some variation in their capacitance and resistance with temperature and ambient humidity. Their capacitance and resistance also vary with their service life. These factors lead to unpredictable changes in the electrical characteristics of the impedance elements forming the voltage divider chain over time, which is reflected in unpredictable changes in the voltage division ratio of the voltage divider in which the voltage is divided using the impedance elements. Because of these variations, some conventional voltage sensors are less accurate at sensing the voltage of the inner conductor.

Disclosure of Invention

The voltage divider for an AC voltage sensor on a MV/HV power cable according to the present disclosure should withstand peak voltages of at most 175kV, preferably at most 200kV, without being destroyed. In the normal state of the power network, it should be able to measure a voltage that is at least twice the "normal" voltage of the inner conductor to ground. In medium voltage power networks, this normal voltage is usually considered to be 20.8kV, and thus the sensors are designed to measure voltages of at least about 42 kV. The voltage divider of the sensor should advantageously provide an electrical output signal that can be processed by standard electronic circuitry, such as an output signal between 1 millivolt (mV) and 10 volts. This target output voltage and the voltage range of 1kV to 42kV of the inner conductor require a voltage divider with a voltage division ratio, i.e. the voltage division ratio of the MV cable is in the range of about 1:100 up to about 1:4200, and the voltage division ratio of the HV cable is correspondingly higher. To enable the sensor to be used with a variety of different cables, a suitable target voltage division ratio may be about 1: 10000. Therefore, the impedance of the high voltage side of the voltage divider needs to be about 10000 times the impedance of the low voltage side of the voltage divider. For a capacitive divider, this requires the capacitance on the high side to be about 1:10000 of the capacitance on the low side.

It is desirable to provide components of an AC voltage divider for accommodation in an MV/HV cable termination or cable plug to reduce the risk of electrical discharge. These components should also provide a voltage division ratio that allows connection to a common electronic circuit. It is also desirable that such components be more cost effective. It is also desirable to provide such components that are less susceptible to aging effects and environmental effects.

The present disclosure seeks to address these needs. According to a basic aspect of the present disclosure, there is provided an impedance assembly for a voltage divider for sensing an AC voltage of at least 1kV to ground of a power carrying conductor distributing electrical energy in a national electrical network, wherein the impedance assembly comprises

a) A printed circuit board comprising one or more dielectric board layers,

b) a high-voltage contact that is accessible from the outside,

c) an externally accessible low-voltage contact, wherein any externally accessible portion of the low-voltage contact is spaced from any externally accessible portion of the high-voltage contact by a geometric distance of at least 30mm, an

d) At least two voltage dividing capacitors electrically connected in series between the high voltage contact and the low voltage contact and operable as a high voltage side of the voltage divider,

wherein each voltage dividing capacitor has: two electrodes formed from opposing conductive regions disposed on opposing surface portions of a particular dielectric slab layer of the one or more dielectric slab layers; and a dielectric disposed between the electrodes and comprising a portion of the particular dielectric slab on which the electrodes are disposed.

The impedance component according to this first basic aspect of the present disclosure comprises at least two voltage dividing capacitors. Accordingly, it is also referred to herein as a "capacitor assembly". Which may form part of a voltage divider. A printed circuit board ("PCB") provides particularly robust and reliable support for the relatively conductive regions of the capacitor electrodes on its dielectric board layers. The arrangement of the high voltage contacts and the low voltage contacts at a distance of at least 30mm from each other reduces the risk of electrical discharges between these contacts.

Generally, the impedance component may have an elongated shape. The elongated shape may define a length direction and opposing end portions. In particular, the impedance assembly may be suitably shaped to be housed in a longitudinal cavity of an elongated elastic sleeve for insulating the power cable. This shape facilitates the placement of the impedance assembly in a cable termination, a cable plug or a similar cable accessory comprising an elastic sleeve. The advantage of being placed in the sleeve is that the existing insulating material of the sleeve can also be used to insulate the impedance component, thereby reducing the risk of electrical discharges over the impedance component and eliminating the need to provide a separate dedicated insulator for the impedance component.

The voltage drop from high to low across the impedance component is achieved by at least two voltage dividing capacitors. This minimum number of voltage dividing capacitors ensures that the voltage drop over each voltage dividing capacitor is moderate and thus ensures that the risk of discharge over each voltage dividing capacitor is low.

The at least two voltage dividing capacitors may be electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a combined capacitance of at least 10 picofarads (pF). This combined capacitance allows the low side capacitor of the voltage divider to have a capacitance of about 100 nano farads (nF) at a given voltage division ratio of about 1:10' 000. Such capacitors of about 100nF are available at reasonable cost with 1% accuracy and acceptable capacitance varies with temperature and service life, for example, according to NP 0.

The construction of a voltage dividing capacitor from the conductive areas forming its electrodes and a portion of the PCB dielectric plate layer forming its dielectric is advantageous over the use of a prefabricated discrete capacitor because it allows the accuracy and withstand voltage to be adjusted to the desired level. For example, proper selection of the material of the PCB of the impedance assembly may result in an acceptable degree of change in capacitance with changes in ambient temperature or humidity. In addition, proper selection of proper spacing between opposing conductive regions can help achieve a desired capacitance.

The impedance component according to the first basic aspect of the present disclosure may be a voltage divider for sensing a voltage of at least 1kV to ground of an inner conductor of a power carrying conductor distributing electrical energy in a national electrical grid. Alternatively, the impedance component according to the first basic aspect of the present disclosure may be or comprise a component of such a voltage divider. In some embodiments, the impedance component comprises a high voltage portion of a voltage divider for sensing an AC voltage of at least 1kV to ground of a power carrying inner conductor of a power cable distributing power in a national power grid.

A voltage divider, such as a capacitive or resistive divider, may be used to measure voltages of 1kV to ground or higher. In the voltage divider, at least two impedance elements ("divider impedances") are electrically connected in series between the high voltage to be measured and electrical ground. The term "impedance" or impedance element as used for a physical element refers herein to a resistor, capacitor, or inductor. In some cases, the term "impedance" is also used herein for the electrical characteristic of the physical element, i.e. the resistance of a resistor, the capacitance of a capacitor or the inductance of an inductor. Between at least two divider impedances forming a voltage divider, a voltage proportional to the high voltage ("sensing voltage") can be picked up, wherein the scaling factor or "divider ratio" is the ratio of the value of the high voltage impedance (i.e. the impedance element directly connected to the high voltage) to the value of the low voltage impedance (i.e. the impedance element directly connected to ground).

A voltage divider in which all of the divided impedance elements are resistors is generally referred to herein as a resistive voltage divider, while a voltage divider in which all of the divided impedance elements are capacitors is referred to herein as a capacitive voltage divider. Alternatively, a voltage divider may be mixed, i.e. one divider impedance being of one type (resistor, capacitor or inductor) and the other divider impedance being of a different type, thereby forming combinations such as resistor-capacitor, inductor-resistor, etc.

The voltage-dividing impedance is not necessarily a single resistor, capacitor or inductor, but may alternatively be constituted by two or more impedance elements. Thus, the voltage divider may comprise a single divider impedance element or a chain of divider impedance elements electrically connected in series. Between two of the chain's voltage dividing impedance elements, at a midpoint or touch location or "pick-up point", a sensing voltage may be picked up. The electrical connections of the voltage divider form the "high side" of the voltage divider for all impedance elements between the pick-up point and the high voltage, and the electrical connections of the voltage divider form the "low side" of the voltage divider for all impedance elements between the pick-up point and ground.

The term "power carrying conductor" refers herein to an element through which electrical power may flow at voltages above 1kV and high currents of tens or hundreds of amperes. Examples of power carrying conductors are e.g. busbars in one or more inner conductors of a switchgear, bushing or power cable, in particular a power cable. The power carrying conductor with which the impedance assembly of the present invention may be used is, for example, a power cable that transmits power over large geographical distances in a national power grid. Medium Voltage (MV) and High Voltage (HV) power cables operate at voltages of 1kV to ground or higher and are designed for currents of tens or hundreds of amperes.

Such power cables essentially comprise a central inner conductor with a diameter of 8 mm or more, which carries power and current. The inner conductor is coaxially surrounded by a layer of insulating material forming the main insulation of the cable, which in turn carries the semiconducting layer on its outer surface. Other layers may be present including, for example, a shielding mesh. The insulating cable jacket forms the outermost layer of the cable.

The impedance assembly according to the present disclosure may be designed to be accommodated in a longitudinal cavity of an elastic sleeve for insulating an electrical power cable. Such sleeves are typically included in cable terminations, cable plugs or cable joints, but may also be used alone. The sleeve has a channel in which a longitudinal portion of a cable, stripped cable or separate inner conductor can be received. These sleeves are elastic in that they are designed to be elastically expandable to receive a cable, or elastically contractible around a cable. Typical elastically expandable sleeves can be pushed coaxially against the main insulation at the end of the cable, expanding and creating friction by their elastic contraction to maintain their position on the cable. The elastically shrinkable sleeve may be applied over a portion of the cable while remaining in the expanded state and then shrunk onto the cable, for example by applying heat, by removing the support, or otherwise.

In addition to the channel, some sleeves have a longitudinal cavity in their insulating material that extends parallel to the channel. A component of a voltage divider, such as an impedance assembly according to the present disclosure, may be housed in the cavity. Since the cavity is formed in the sleeve, it is close to the inner conductor of the cable, so that any connecting wires can be shorter. In addition, this arrangement utilizes existing insulation in the sleeve. The cavity may be insulated with an insulating material disposed around the channel. In addition to the cable, the sleeve that is to house the components of the potentiometer may be appropriately sized to properly insulate both the cable and the components of the potentiometer. Typically, no or little additional insulation is required as compared to a sleeve used only to insulate a cable.

Such an elastic sleeve may have the shape of an elongated tube, extending longitudinally in the direction of the channel. The cavity may be elongate and extend longitudinally in the direction of the channel. The cavity and the channel may be separated by an insulating material. The cavity may have a length of between 20cm and 50 cm. Correspondingly, the impedance component may have a length of between 10cm and 100cm, in particular between 20cm and 50 cm. However, the length of the cavity is generally independent of the length of the channel or the length of the sleeve. The cavity may be shorter than the channel or sleeve.

The elastic sleeve as described above may be included in a cable joint, a separable connector (such as a cable plug) or a cable termination. Such elastomeric sleeves may be equipped with skirts to provide a longer creep current path along the outer surface of the sleeve. They may be equipped with stress control portions for shaping the electric field.

The PCB in the impedance assembly according to the present disclosure includes one or more dielectric slab layers. Where the PCB comprises two or more dielectric board layers, it is also referred to as a multilayer PCB.

Typically, the PCB of the impedance assembly of the present invention is non-conductive and one or more dielectric slab layers of the PCB are non-conductive. At least a portion of the dielectric plate layer of the PCB is capable of operating as a dielectric of the voltage divider capacitor.

In certain embodiments, the PCB is a multilayer PCB. The multi-layer PCB may include at least two conductive regions disposed within the PCB. The two conductive regions may form electrodes of one voltage dividing capacitor of the at least two voltage dividing capacitors. Thus, in certain embodiments, the printed circuit board is a multilayer printed circuit board and at least two of the conductive regions are disposed inside the printed circuit board.

The conductive areas inside the PCB are conductive areas within or embedded in the PCB, opposite the conductive areas on the outer surface of the PCB. The conductive areas inside the PCB may still be exposed at the edge of the PCB and/or externally accessible. For example, the conductive areas inside the PCB and any non-conductive dielectric layer between these conductive areas may be better protected from certain environmental effects caused by corrosion, temperature or humidity.

In certain embodiments, the PCB is a multilayer PCB that includes two conductive regions on the interior of the PCB and two additional conductive regions on the exterior surface of the PCB. Thus, the PCB may comprise four conductive areas, two of which are located inside the PCB and two of which are located on the PCB.

Typically, a dielectric slab in a PCB may carry conductive regions on opposing portions of its surface. This may help to obtain a larger capacitance of the voltage dividing capacitor. The number of dielectric board layers of a PCB is generally not limited. One or more of the dielectric slab layers must be thick enough to reduce the risk of discharge between the conductive areas on opposite parts of its surface, and thus can be used as a dielectric to divide the voltage of the capacitor at voltages of 1kV or higher. The availability of a dielectric slab layer as a dielectric also depends on its electrical properties, such as its dielectric strength or electrical strength.

The impedance component may have an elongated shape, such as a flat rectangular shape. The rectangular shape defines a length and a width. The impedance component may have a rectangular shape having a length of between 10cm and 50cm, in particular between 15cm and 35 cm. It may have a rectangular shape with a width of between 1cm and 5cm, in particular between 2cm and 3 cm.

Where the impedance component has an elongated shape, the elongated shape defines a first end portion and an opposing second end portion. The end portions may be spaced apart from each other along the length of the impedance assembly.

The elongated shape of the impedance component may be defined by the shape of the PCB.

The expression "externally accessible contact" refers herein to a contact suitably arranged to allow access from outside the PCB for fixing a wire to the contact and/or establishing surface contact therewith in order to determine the voltage thereof. For example, the contacts on the outer surface of the PCB are externally accessible contacts.

An impedance assembly according to the present disclosure includes externally accessible high voltage contacts. In case the impedance assembly has an elongated shape, the high voltage contact may be arranged at the first end portion of the impedance assembly. The high voltage contact is adapted for wired connection to a power carrying conductor, e.g. to an inner conductor of a power cable. The high voltage contact may comprise, for example, a solder point to which a wire connected to the power carrying conductor may be fixed. Alternatively, the high voltage contact may be included in, for example, a connector with which a mating connector may mate to establish a connection with the inner conductor. In a specific embodiment, the high voltage contact is an exposed solder joint on the outer surface of the printed circuit board.

The impedance assembly also includes externally accessible low voltage contacts. In case the impedance assembly has an elongated shape, the high voltage contact may be arranged at the second end portion of the impedance assembly, in case the high voltage contact is arranged at the first end portion of the impedance assembly. The low voltage contact is adapted to be grounded or connected to a low voltage of 10V or less. The low voltage contact may comprise, for example, a pad to which a wire for connection to a ground element may be secured. Alternatively, the low voltage contact may be included in, for example, a connector with which a mating connector may mate to establish an electrical connection with the ground element. In a specific embodiment, the low voltage contact is an exposed solder joint on the outer surface of the printed circuit board.

In some embodiments, the low voltage contact may be a ground contact of a voltage divider, the ground contact being for sensing the voltage of the power carrying conductor. In these embodiments, all of the electrical components of the voltage divider (including its high voltage side and its low voltage side) may be housed on the PCB. The low voltage side may comprise a capacitor forming a total capacitance between 20nF and 500nF, in particular between 40nF and 100 nF.

In other alternative embodiments, the low voltage contact may be a midpoint contact or a pickup contact of the voltage divider. In these embodiments, the electrical components (e.g., impedance components) forming the voltage divider on the high voltage side thereof may be housed on the PCB. Electrical components, such as impedance components, forming the low voltage side of the voltage divider may be housed on or off (i.e., away from) the PCB.

Any externally accessible portion of the low voltage contact is spaced apart from any externally accessible portion of the high voltage contact by a geometric distance of at least 30 millimeters (mm). This distance helps to reduce the risk of electrical discharge between the high voltage contact and the low voltage contact. In case the high voltage contact is arranged at a first end portion of the impedance assembly, the low voltage contact may be arranged at an opposite second end portion. However, in certain embodiments, there may be a higher risk of discharge. In such embodiments, the externally accessible portion of the low voltage contact may be spaced apart from the externally accessible portion of the high voltage contact by a distance of at least 50mm, or at least 100 mm. This distance will be measured purely geometrically as the length of a straight line between the respective externally accessible portions of the high and low voltage contacts that are closest to each other. Conductive traces or exposed wire portions leading to high voltage contacts or leading to low voltage contacts should not be considered part of the respective contacts as they are not suitable for connection (e.g., mechanical connection) to a wire or connector.

A capacitor assembly according to the present disclosure includes at least two voltage dividing capacitors electrically connected in series between a high voltage contact and a low voltage contact of an impedance assembly. These voltage dividing capacitors may form the high voltage side or a part of the high voltage side of the voltage divider for sensing the voltage of the inner conductor.

The inventors of the present disclosure have found that a smaller number of voltage dividing capacitors may result in an excessively high electric field strength on each voltage dividing capacitor and thus a higher risk of discharge on one of the voltage dividing capacitors.

A larger number of voltage dividing capacitors, e.g. three, four, five, six, seven, eight, nine, ten or even more, will reduce the electric field strength over each individual capacitor, but the resulting cumulative capacitance of the voltage dividing capacitors will become smaller and smaller. To achieve a combined capacitance of at least 10pF at the available division ratio of the voltage divider, each individual capacitor would have to have a larger capacitance but a smaller geometric footprint. The inventors of the present disclosure contemplate a maximum number of twenty voltage dividing capacitors. Thus, in certain implementations, the impedance component may include four, five, six, seven, or eight voltage dividing capacitors. In certain other embodiments, it may comprise between two and twelve voltage dividing capacitors, and in certain other embodiments, it may comprise between two and twenty voltage dividing capacitors.

In a particular embodiment, the impedance assembly includes a total of six voltage dividing capacitors electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a combined capacitance of at least 10 picofarads, and operable as the high voltage side of the voltage divider between the low voltage and the high voltage of the power carrying conductor, wherein each voltage dividing capacitor has: two electrodes formed from opposing conductive regions disposed on opposing surface portions of a particular dielectric slab layer of the one or more dielectric slab layers; and a dielectric disposed between the electrodes and comprising a portion of the particular dielectric slab on which the electrodes are disposed.

This number of six voltage dividing capacitors seems to provide a good balance between the risk of discharge on the voltage dividing capacitors and the achievable combined capacitance of the voltage dividing capacitors for many common geometries of the impedance component and many material properties of the dielectric of the impedance component.

In all of these embodiments, the voltage divider capacitor is electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a combined capacitance of at least 10pF, and may be capable of operating as the high voltage side of the voltage divider between the low voltage and the high voltage of the power carrying conductor.

A voltage divider in which the impedance component according to the present disclosure may be used preferably provides an output voltage picked up at the midpoint that can be handled in standard electronic circuits, for example an output voltage between 1 millivolt and 10 volts, advantageously with a voltage division ratio of about 1: 10000. For a given voltage division ratio, a lower overall capacitance on the high voltage side of the voltage divider requires a lower overall capacitance on the low voltage side. Due to the high voltage division ratio, it is generally desirable for the high voltage side to have a larger overall capacitance and a corresponding lower impedance. The larger capacitance on the high voltage side of the voltage divider makes the voltage divider less sensitive to the effects of parasitic capacitance and improves the accuracy of voltage sensing. However, building larger capacitors in places where space is limited is more difficult and costly.

Which voltage divider ratio is desired may depend, inter alia, on the desired voltage of the inner conductor and/or on the desired sensor output voltage at the midpoint of the voltage divider. Thus, in certain embodiments of the present disclosure, at least two voltage dividing capacitors provide a combined (i.e., overall) capacitance of at least 10 pF. In certain of those embodiments, at least two voltage dividing capacitors are electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a combined capacitance of at least 20pF, or at least 50pF, or at least 100 pF. In certain embodiments, at least two voltage dividing capacitors are electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a combined (i.e., overall) capacitance between 10pF and 100pF or between 20pF and 60 pF.

Each of the at least two voltage dividing capacitors has two electrodes and one dielectric. The electrodes of each of the at least two voltage dividing capacitors are formed by opposing conductive areas on opposing surface portions of a particular dielectric plate layer of the one or more dielectric plate layers of the PCB. Therefore, the voltage dividing capacitor is not a discrete surface mount component, also known in the art as an SMD. Instead, they are made of conductive areas on or in the PCB opposite each other, so that they form capacitor plates. The opposing conductive regions may be parallel to each other. In the case where two conductive regions form electrodes of a voltage dividing capacitor, only a part of one conductive region may be opposed to the other conductive region.

The conductive region may comprise, for example, a conductive metal layer, such as copper, silver, or gold. Such a conductive metal layer may be disposed (e.g., coated) on a surface portion of the dielectric slab layer. The conductive region may have a thickness of, for example, between 1 μm and 100 μm.

The conductive areas may be arranged on or in the PCB. The conductive areas may for example be arranged on an outer surface of the PCB. Such an arrangement is advantageous for establishing electrical contact with the electrically conductive areas, for example by soldering or surface contact, since the electrically conductive areas on the outer surface of the PCB are particularly easy to access.

The conductive region may be disposed in the PCB. Where the PCB is a multi-layer PCB, the conductive regions may be formed by conductive patches or conductive coatings on the inner dielectric slab layers of the PCB. The electrically conductive region arranged in the PCB (e.g. on a surface portion of the inner dielectric slab layer) may comprise a portion that is accessible from the outside, e.g. at an edge of the PCB.

The conductive region may be coextensive with the PCB. Alternatively, the conductive region may extend over only a portion of the PCB. For example, where the PCB is a flat rectangular body of 20mm by 250mm dimensions (and say about 1mm thickness), the conductive areas in or on the PCB may have dimensions of 20mm by 50 mm.

In the case where the electrodes of the voltage dividing capacitor are formed of two opposite conductive regions, the two conductive regions may be disposed on the outer surface of the PCB. In case the PCB is a single layer PCB, i.e. it has only one dielectric plate layer, the conductive areas of all at least two voltage dividing capacitors may be arranged on opposite outer surfaces of the PCB. Alternatively, in case the PCB has two or more dielectric plate layers, the conductive areas of all at least two voltage dividing capacitors may be arranged in the PCB. Alternatively, one of the conductive regions may be disposed on the PCB, and the other conductive regions may be disposed in the PCB.

Each of the at least two voltage dividing capacitors includes a dielectric including a portion of an electrode of a particular dielectric plate layer on which the respective voltage dividing capacitor is formed. The dielectric properties of the PCB and its dielectric plate layers may have an effect on the capacitance of the at least two voltage dividing capacitors. Accordingly, one or more PCB substrate materials may be suitably selected, for example, to minimize the effect of temperature changes on the capacitance of the partial piezoelectric capacitor. Ceramic materials are known to have certain dielectric properties that vary relatively little with temperature at the temperatures at which power cables are typically used. Thus, in certain preferred embodiments, the printed circuit board is a ceramic PCB. In some of these embodiments, the printed circuit board is a ceramic multilayer PCB. At least one of the dielectric plate layers may comprise a ceramic material, independent of the PCB being a single layer PCB or a multi-layer PCB. In certain preferred embodiments of the impedance assembly according to the present disclosure, each dielectric slab layer of the PCB comprises a ceramic material.

The material forming the dielectric plate layer may be suitably selected, for example, to minimize the effect of humidity changes on the capacitance of the at least two voltage dividing capacitors. Also, ceramic materials are known to have dielectric properties that vary relatively little with changes in ambient humidity, and thus may be suitable materials for the dielectric board layer of a PCB or the entire PCB.

The PCB is typically non-conductive. The portion of the dielectric plate layer that forms the dielectric of the voltage divider capacitor is non-conductive. The PCB of the impedance assembly according to the present disclosure may be a mechanical support for other elements of the impedance assembly. The high voltage contact may be supported by the PCB. The low voltage contacts may be supported by the PCB.

The individual dielectric board layers of the PCB may be formed of or contain ceramic materials such as hydrocarbon ceramic materials, or a combination of woven glass fibers and epoxy resins such as those in the materials known as FR3, FR4 or FR 5. The dielectric slab layer may be or comprise a PTFE (polytetrafluoroethylene) material, a PEEK (polyetheretherketone) material, a LCP (liquid crystal polymer) material, a polyimide material or an epoxy material. The dielectric slab layer may comprise a mixture or combination of these materials, such as, for example, in a ceramic filled PTFE PCB.

In certain embodiments, the PCB is a ceramic body, i.e. the PCB has only one dielectric slab of ceramic material. The ceramic body may be a solid body without internal structures (e.g., without internal layer structures). The ceramic body may support on its outer surface conductive areas forming electrodes of a voltage dividing capacitor. The ceramic body may be particularly cost-effective to manufacture and may be reinforced to withstand mechanical forces.

Examples of ceramic materials that may be used for the dielectric plate layer of the PCB in the impedance assembly as described herein are silicon nitride, alumina such as Al₂O₃Aluminum nitride such as AlN and low temperature co-fired ceramic.

In order to reduce the risk of electrical discharges between the elements of the impedance component, the impedance component or parts thereof may be embedded in a non-conductive encapsulation material. For example, the encapsulating material may be a hardening resin. In case the impedance component has an elongated shape, the middle portion of the impedance component may be embedded in the encapsulation material, while the end portions may be free of encapsulation material. In some embodiments, at least a portion of the impedance component is embedded in the non-conductive encapsulation material. In some embodiments, the impedance component has an elongated shape and at least 50% of the geometric length of the impedance component is embedded in the non-conductive encapsulation material. In some embodiments, at least 50% or at least 70% of the geometric length of the impedance component is embedded in the encapsulation material. In another embodiment, 100% of the geometrical length of the impedance component, i.e. the entire impedance component, is embedded in the encapsulation material.

In case the impedance component is partially or completely embedded in an electrically insulating encapsulation material, an electrically conductive layer may be applied on the outer surface of the encapsulation material to form a shielding of the impedance component. Conventionally, the shield or barrier is held to an electrical ground. However, a barrier on an electrical ground may generate parasitic currents between the element of the impedance assembly and the barrier at higher voltages through the encapsulation material. Parasitic currents are undesirable because they can reduce the accuracy of the voltage sensing mechanism, particularly because their magnitude can vary uncontrollably with the temperature and/or humidity of the packaging material.

Conventionally, the barrier is held at an electrical potential, such as ground. Since the voltage of the voltage dividing capacitor near the high voltage portion (i.e., the portion including the high voltage contact) of the impedance component is higher than the voltage of the voltage dividing capacitor near the relatively low voltage portion (i.e., the portion including the low voltage contact) of the impedance component, the voltage difference with the barrier varies along the extension of the impedance component and from one voltage dividing capacitor to the adjacent voltage dividing capacitor, and thus varies the generated parasitic current. Higher voltage differences generally result in higher parasitic currents.

In an attempt to reduce these parasitic currents, it has been found to be advantageous to divide the barrier into two conductive parts separated by an intermediate insulating gap: the low voltage barrier portion is applied to an outer surface of the potting material encapsulating the low voltage portion of the impedance assembly and is maintained at an electrical ground or low voltage, while the high voltage barrier portion is applied to an outer surface of the potting material encapsulating the high voltage portion of the impedance assembly and is maintained at a high voltage.

Therefore, the voltage dividing capacitor in the low voltage part is shielded by the electrical ground or a barrier on the low voltage, which reduces the voltage difference and the parasitic current. Similarly, the voltage dividing capacitor in the high voltage part is shielded by the barrier on the high voltage, which reduces the voltage difference and the parasitic current in the high voltage part of the impedance component.

The intermediate portion of the outer surface of the encapsulation material encapsulating the impedance component, i.e. the portion encapsulating the intermediate portion of the impedance component between the high voltage portion and the low voltage portion of the impedance component, is not provided with a barrier. Such an unshielded gap is necessary to avoid discharges between the high voltage barrier and the low voltage barrier.

Thus, in general, in certain embodiments of the impedance component according to the present disclosure in which at least a portion of the impedance component is embedded in a non-conductive encapsulation material, an outer surface of the encapsulation material comprises

-a first surface area covered with a conductive layer for connection to a high voltage;

-a second surface area covered with an electrically conductive layer for connection to an electrical ground; and

a third surface area, electrically insulating and free of an electrically conductive layer, arranged between the first surface area and the second surface area for insulating the first surface area from the second surface area.

The first surface area may be arranged and dimensioned to form a conductive envelope around the low voltage portion of the impedance component. The second surface area may be arranged and dimensioned to form a conductive envelope around the high voltage portion of the impedance component.

In a specific embodiment, wherein the impedance component has an elongated shape and is completely embedded in a non-conductive encapsulation material and wherein the low voltage portion and the high voltage portion are arranged at opposite end portions of the impedance component, a first surface area of the encapsulation material is covered with a conductive layer for connection to the high voltage, which conductive layer encapsulates the high voltage portion. The second surface area of the encapsulation material is covered with a conductive layer for connection to a low voltage or electrical ground, which encapsulates the low voltage portion. In a central surface area of the encapsulation material encapsulating the intermediate portion of the impedance component, there is no electrically conductive layer between the first surface area and the second surface area, and the electrically insulating gap separates the first surface area and the second surface area from each other.

Certain impedance components according to the present disclosure may be shaped to be adapted for receipt in a longitudinal cavity of an elastomeric sleeve for insulating an electrical power cable. Such sleeves are used in particular for cable terminations, cable plugs and cable joints. The length of such terminals, plugs, fittings and sleeves is typically 30 centimeters or less. To facilitate accommodation in such plugs, fittings and sleeves, in certain embodiments of the present disclosure, the impedance component has an elongated shape and a length of 30 centimeters or less. In certain of these embodiments, the impedance component has a length of 20cm or less, or 10cm or less, or even 5cm or less. The length will be measured geometrically along the length of the cable on which the termination, splice, plug or sleeve will be placed in use. For very short impedance components, additional insulation may be required in order to reduce the risk of discharge.

In one aspect, the present disclosure provides a sensing cable accessory comprising a) a cable termination comprising an elastomeric sleeve for electrically insulating a power carrying conductor of an electrical power cable, the sleeve having a longitudinal cavity for receiving an impedance component as described herein, and b) an impedance component as described herein, the impedance component being disposed in the cavity of the sleeve.

In another aspect, the present disclosure provides a sensing cable accessory comprising a) a cable plug comprising an elastomeric sleeve for electrically insulating a power carrying conductor of an electrical power cable, the sleeve having a longitudinal cavity for receiving an impedance component as described herein, and b) an impedance component as described herein, the impedance component being disposed in the cavity of the sleeve.

The sleeve may be formed in a molding process in which a hollow mold defining the shape of the sleeve is filled with a liquid molding material, which is then cured and formed into the sleeve. In some embodiments according to the present disclosure, the impedance component, whether embedded or not embedded in the non-conductive encapsulation material, is placed in the mold just prior to molding the sleeve. Thereby molding the impedance assembly into the sleeve. In this case, the cavity of the sleeve takes the exact shape of the impedance component. This reduces the occurrence of air pockets, which otherwise could lead to a higher risk of discharge.

An impedance component according to the present disclosure may include a resistor layer connected between a high voltage contact and a low voltage contact to be able to operate as the high voltage side of a voltage divider, rather than a voltage dividing capacitor connected between the high voltage contact and the low voltage contact.

Accordingly, in a second general aspect of the present disclosure, there is provided an impedance assembly for use in a voltage divider for sensing an AC (i.e. alternating current) voltage of between 6kV and 175kV of an inner conductor of a power cable for distributing power in an electrical network, wherein the impedance assembly has an elongate shape defining a first end portion and an opposite second end portion for accommodation in a longitudinal cavity of an elastic sleeve for insulating the power cable, and wherein the impedance assembly comprises

a) A substrate, a first electrode and a second electrode,

b) a high voltage contact arranged at the first end portion for current connection to the inner conductor,

c) a low-voltage contact arranged at a second end portion at a distance of at least 10cm from the high-voltage contact for electrical connection to a low voltage of 10 volts or less, an

d) A resistor layer disposed on an inner or outer surface of the substrate and extending between the first and second end portions, electrically connected in series between the high voltage contact and the low voltage contact, such as to provide a resistance of at least 50M Ω (mega ohms), wherein the resistor layer is operable as a high voltage side of a voltage divider between the low voltage and the high voltage of the inner conductor.

The impedance assembly (also referred to herein as "resistor assembly") according to this second basic aspect provides a resistor in the form of a resistor layer for the high voltage side of the voltage divider for sensing the voltage of the inner conductor, which is the power carrying conductor of the power cable. The resistor layer forms a resistance in the voltage divider. The voltage divider may be a resistive voltage divider or a hybrid voltage divider.

According to the first basic aspect of the above disclosure, several components of the resistor assembly, such as the substrate, the high voltage contact or the low voltage contact, are also included in the capacitor assembly. These components perform the same function in both impedance components and will therefore not be explained again.

The resistor assembly may form part of a voltage divider. The elongate shape of the resistor assembly facilitates its accommodation in the sleeve of a cable termination or cable plug. The arrangement of the high voltage contacts and the low voltage contacts at opposite ends of the resistor assembly at a distance of at least 10cm from each other reduces the risk of electrical discharges between these contacts.

The resistor assembly is suitably shaped to be received in a longitudinal cavity of an elongated elastic sleeve for insulating the power cable. This shape facilitates the placement of the resistor assembly in a cable termination, cable plug or similar cable accessory comprising an elastic sleeve. The advantage of being placed in the sleeve is that the existing insulation of the sleeve can also be used to insulate the resistor assembly, thereby reducing the risk of electrical discharge over the resistor assembly and eliminating the need to provide a dedicated insulation for the resistor assembly.

The voltage drop from high to low across the voltage divider is realized across a resistor layer that provides a resistance of at least 50M omega. The resistance of the resistor layer in combination with its geometrical extension between the first end portion and the second end portion of the resistor assembly ensures a moderate voltage drop per unit length over the resistor layer and thus a low risk of discharge over the resistor layer.

Constructing the resistor via a resistor layer is advantageous over the use of pre-fabricated discrete resistors because it allows the accuracy of the resistance and the accuracy of the breakdown voltage to be tuned to a desired degree. In addition, it may be difficult to obtain discrete resistors with suitable geometrical extensions.

The resistor assembly according to the second basic aspect of the present disclosure may be a voltage divider for sensing a voltage of at least 6kV of an inner conductor of a power cable distributing power in a national power grid. Alternatively, such a resistor component may be or comprise a component of such a voltage divider. In some embodiments, the resistor assembly includes a high voltage portion of a voltage divider for sensing a voltage of at least 6kV to ground of an inner conductor of a power cable that distributes power in a power grid.

The substrate of a resistor assembly according to the present disclosure may be a mechanical support for other elements of the resistor assembly. The high voltage contact may be supported by the substrate. The low voltage contact may be supported by the substrate. The substrate may be, for example, a printed circuit board ("PCB"), such as a single layer PCB or a multilayer PCB, or include a PCB. The multi-layer PCB may include one or more dielectric board layers. The substrate may comprise a fibre reinforced polymer material such as FR 4. The substrate may be or include a single or multilayer ceramic PCB.

Alternatively, the substrate may be a ceramic body, such as a single layer ceramic body or a multilayer ceramic body.

The substrate of the resistor assembly is non-conductive. The substrate may be or comprise a ceramic hydrocarbon material, such as Rogers4000 series PCB material. Alternatively, the substrate may be or comprise a PTFE (polytetrafluoroethylene) material or an epoxy material.

The resistor assembly may have an elongated shape, such as a flat rectangular shape. The rectangular shape defines a length and a width. The resistor assembly may have a rectangular shape having a length of between 10cm and 50cm, in particular between 15cm and 35 cm. It may have a rectangular shape with a width of between 1cm and 5cm, in particular between 2cm and 3 cm.

The elongated shape defines a first end portion and an opposing second end portion. The end portions may be spaced apart from each other along the length of the resistor assembly. The elongated shape of the resistor assembly may be defined by the shape of the substrate.

The resistor assembly includes a high voltage contact disposed at a first end portion of the resistor assembly. The high voltage contact is adapted for galvanic connection to the inner conductor. The high voltage contact may be adapted to be galvanically connected to the inner conductor, for example by being externally accessible on an outer surface of the resistor assembly. The high voltage contact may comprise, for example, a solder point to which a wire connected to the inner conductor may be fixed. Alternatively, the high voltage contact may be included in, for example, a connector with which a mating connector may mate to establish a galvanic connection with the inner conductor. In a specific embodiment, the high voltage contact is an exposed solder joint on an outer surface of a printed circuit board forming the substrate.

The resistor assembly also includes a low voltage contact disposed at a second end portion of the resistor assembly. The low voltage contact is adapted to be grounded or connected to a low voltage of 10V or less. The low voltage contact may be adapted to be electrically (e.g., galvanic) connected to electrical ground, for example, by being externally accessible on an outer surface of the resistor assembly. The low voltage contact may comprise, for example, a pad to which a wire for connection to a ground element may be secured. Alternatively, the low voltage contact may be included in, for example, a connector with which a mating connector may mate to establish an electrical connection with the ground element. In a specific embodiment, the low voltage contact is an exposed solder joint on the outer surface of a printed circuit board forming the substrate.

In some embodiments, the low voltage contact may be a ground contact of a voltage divider, which is used to sense the voltage of the inner conductor. In these embodiments, all of the electrical components of the voltage divider (including its high side and its low side) may be housed on the substrate.

In other alternative embodiments, the low voltage contact may be a midpoint contact or a pickup contact of the voltage divider. In these embodiments, the electrical components (e.g., impedance elements or impedances) forming the voltage divider on the high voltage side thereof may be housed on the substrate. The electrical components forming the low voltage side of the voltage divider may be housed on or off (i.e., away from) the substrate.

In case the high voltage contact is arranged at a first end portion of the resistor assembly, the low voltage contact is arranged at an opposite second end portion. It is arranged at a distance of at least 10cm from the high voltage contact. This distance helps to reduce the risk of electrical discharge between the high voltage contact and the low voltage contact. However, in certain embodiments, the low voltage contact is disposed at a distance of at least 15 centimeters or at least 20 centimeters from the high voltage contact. This distance will be measured purely geometrically as the length of a straight line between the closest parts of the high voltage contact and the low voltage contact. Conductive traces or exposed wire portions leading to high voltage contacts or leading to low voltage contacts should not be considered part of the respective contacts as they are not suitable for connection (e.g., mechanical connection) to a wire or connector.

The distance between the high voltage contact and the low voltage contact of the impedance assembly according to the second basic aspect is at least 10 cm. The resistor layer extends between a first end portion and a second end portion of the resistor assembly. In order to promote a moderate voltage drop over the resistor layer and thus reduce the risk of discharges between the elements on low voltage and the elements on high voltage, the resistor layer should have an elongated shape. In other words, the resistor layer should extend longitudinally. The length direction thereof may be a direction between the first end portion and the second end portion of the impedance component. The greater the length of the resistor layer, the less the risk of discharge between its two ends. Thus, in certain embodiments of the present disclosure, the resistor layer extends longitudinally at least 100 mm. In some of these embodiments, the resistor layer extends longitudinally at least 120 mm. In some embodiments, the resistor layer has a longitudinal extension between 100mm and 200 mm.

An impedance component according to the second basic aspect of the present disclosure may comprise both a high voltage side and a low voltage side of a voltage divider for sensing the voltage of the inner conductor. The low voltage side of the voltage divider may also include a resistor layer. Thus, in certain embodiments, a resistive component comprising a (first) resistor layer as described herein further comprises a second resistor layer electrically connected in series with the first resistor layer. The second resistor layer is operable as a low side of the voltage divider for sensing the voltage of the inner conductor. A pickup or midpoint may be electrically provided between the first resistor layer and the second resistor layer on the substrate.

A sensing cable accessory as disclosed herein may form part of a voltage sensor for sensing the voltage of an inner conductor of a power carrying conductor, such as a power cable, in an electrical network, such as a national electrical network. If the sleeve with the impedance component is self-contained according to the first or second basic aspect of the present disclosure, it may be ready to be applied around the power carrying conductor.

In another aspect, the present disclosure also provides a kit of parts for assembling a sensing cable accessory as described above, the kit comprising a) an elastic sleeve for electrically insulating a power carrying conductor of an electrical power cable, the sleeve having a longitudinal cavity for accommodating an impedance assembly as described herein, and b) an impedance assembly as described herein.

In particular, the impedance component in such a kit may be fully or partially embedded in a non-conductive encapsulation material.

Such a kit may be adapted to be assembled to form part of a voltage sensor for sensing the high voltage of the inner conductor of an MV/HV power cable. For assembly, the impedance assembly may be pushed into the cavity of the sleeve.

In another aspect, the present disclosure provides an electrical power network for distributing energy in a national electrical grid, the electrical power network comprising an electrical power carrying conductor and a voltage divider electrically connected to the electrical power carrying conductor for sensing an AC (i.e. alternating current) high voltage of the electrical power carrying conductor, the voltage divider comprising an impedance component as described herein.

Drawings

The invention will now be described in more detail with reference to the following drawings, which illustrate specific embodiments of the invention. Some of the figures may not be drawn to scale and certain dimensions (e.g., thicknesses) may be exaggerated for clarity.

FIG. 1 is a circuit diagram of a voltage divider connected to a power cable;

fig. 2 is a longitudinal sectional view of a first impedance component according to the present disclosure;

fig. 3 is a longitudinal sectional view of a second impedance component according to the present disclosure, wherein the printed circuit board is a multilayer PCB;

FIG. 4 is a longitudinal sectional view of a third impedance component embedded in an encapsulation material;

FIG. 5 is a perspective view of a fourth impedance assembly according to the present disclosure received in a cavity of an elastomeric sleeve;

FIG. 6 is a longitudinal cross-sectional view of a fifth impedance component according to the present disclosure, the component being embedded in an encapsulant material provided with a split screen; and is

Fig. 7 is a top view of a sixth impedance component according to the present disclosure, the component including a resistor layer.

Detailed Description

The circuit diagram of fig. 1 shows a voltage divider for sensing the voltage of the inner conductor 10 of the power carrying conductor, i.e. the high voltage power cable 20. The end portion of the cable 20 is shown in plan view. It is peeled off so that the main insulating layer 30 and the semiconductor layer 40 surrounding the inner conductor 10 are visible. When the cable 20 is used, the inner conductor 10 is typically at a voltage between 1kV and 175kV to electrical ground and conducts alternating current of tens to hundreds of amperes.

To sense the voltage of the inner conductor 10, the voltage divider 50 is electrically connected to the inner conductor 10 and to electrical ground 75. The voltage divider 50 includes a high voltage side 60 and a low voltage side 70. The divided voltage may be picked up at an access point 80 of the voltage divider 50. The divided voltage is proportional to the voltage of the inner conductor 10, where the scaling factor is the division ratio of the voltage divider 50.

The high side 60 of the voltage divider 50 is comprised of two voltage dividing capacitors 90 electrically connected in series between a high voltage contact 100 and a low voltage contact 110 of the voltage divider 50. The low voltage contact 110 allows the divided voltage at the access point 80 to be obtained. In some voltage dividers available in the context of the present disclosure, each of the two voltage dividing capacitors 90 has a capacitance of 40pF, such that they provide a combined capacitance of 20 pF.

The low voltage side 70 of the voltage divider 50 includes a single capacitor, referred to as a low voltage capacitor 120. The low voltage capacitor is connected between the midpoint 80 and the electrical ground 75. In some voltage dividers available in the context of the present disclosure, the low voltage capacitor 120 has a capacitance of 200nF and an NP0 rating for temperature stability.

The voltage divider 50 has a division ratio of about 1: 10000. If the inner conductor 10 is at 50kV, the output voltage of the voltage divider 50 at the low voltage contact 110 is about 5V. This magnitude of voltage can be handled by standard electronic circuitry.

On the high voltage side 60 of the voltage divider 50, a large voltage drop from 50kV to 5V over the two voltage dividing capacitors 90 requires a specific mechanical and electrical design, as will be explained below.

Fig. 2 is a longitudinal sectional view of the first impedance component 1 according to the present disclosure. The first impedance assembly 1 comprises a PCB 130 made of FR4 material. In this example, the PCB 130 has two major surfaces, an upper major surface 140 and an opposing lower major surface 150, and is about 1mm thick. The PCB 130 is a single layer PCB 130, i.e. the base of the PCB 130 is formed by one single dielectric slab layer 209.

The impedance assembly 1 has an elongated shape. The impedance assembly extends lengthwise between a first end portion 180 and an opposing second end portion 190. The length (x-) direction of the impedance component 1 is indicated by arrow 160 and its thickness (z-) direction is indicated by arrow 170. The width direction is orthogonal to the length direction 160 and the thickness direction 170.

The impedance assembly 1 has on its first end portion 180 a high voltage contact 100 for physical connection to the inner conductor 10 of the power cable 20 and on its second end portion 190 a low voltage contact 110 for connection to a low voltage of 10 volts or less. Both the high voltage contact 100 and the low voltage contact 110 include corresponding pads to facilitate wire connection. Two voltage dividing capacitors 90 are electrically connected in series between the high voltage contact 100 and the low voltage contact 110. These voltage dividing capacitors 90 are operable as the high voltage side 60 of the voltage divider 50 for sensing the voltage of the inner conductor 10 of the power cable 20, as shown in fig. 1.

Physically, the electrodes of each of the two voltage dividing capacitors 90 are formed by opposing conductive regions coated with a 12 μm thick copper layer on the major surfaces 140, 150 of the PCB 130. Alternatively, a thicker copper layer may be used, such as a 35 μm or 70 μm thick copper layer. A first conductive region 201 arranged on the upper surface 140 of the PCB 130 and an opposing second conductive region 202 arranged on the lower surface 150 form the electrodes of the first (leftmost in fig. 2) voltage dividing capacitor 90. The second conductive region 202 and the third conductive region 205 form a second voltage dividing capacitor 90. Each of the two voltage dividing capacitors 90 has a capacitance of about 24pF, resulting in a combined capacitance of the two voltage dividing capacitors 90 of about 12 pF.

The dielectric of each of the two voltage dividing capacitors 90 is formed by a respective portion of the substrate of the PCB 130, which is located between those portions of the opposing conductive areas 201,202,205 that are arranged directly opposite each other.

The first conductive region 201 is connected to the high voltage contact 100 and the third conductive region 205 is connected to the low voltage contact 110.

The geometric distance D between the externally accessible portion of the high voltage contact 100 and the externally accessible portion of the low voltage contact 110 is about 35 mm. This distance helps to ensure that the risk of discharge between any two electrodes 201,202,205 remains low and the risk of discharge between the high voltage contact 100 and the low voltage contact 110 is low.

The geometrical length L of the impedance assembly 1 is about 50mm, so that the impedance assembly 1 can be accommodated in the cavity of even a relatively short elastic sleeve for insulating the power cable 20.

Fig. 3 is a longitudinal sectional view of the second impedance component 2 according to the present disclosure. The second impedance component 2 comprises a multilayer ceramic PCB 131. The PCB 131 has two major surfaces: an upper major surface 140 and an opposite lower major surface 150, and has a thickness of about 2 mm.

The impedance assembly 2 has an elongated shape. The impedance assembly extends lengthwise between a first end portion 180 and an opposing second end portion 190. The length (x) direction of the impedance component 1 is indicated by arrow 160 and its thickness (z) direction is indicated by arrow 170. Some dimensions along the z-direction are drawn exaggerated for greater clarity. The width direction is orthogonal to the length direction 160 and the thickness direction 170.

Similar to the first impedance assembly 1 of fig. 2, the second impedance assembly 2 has on its first end portion 180 a high voltage contact 100 for connection to the inner conductor 10 of the power cable 20 and on the lower surface 150 of the second end portion 190 a low voltage contact 110 for connection to a low voltage of 10 volts or less. Both the high voltage contact 100 and the low voltage contact 110 include corresponding pads to facilitate wire connection. Their geometrical distance D between the high-voltage contact and the low-voltage contact is about 30cm, wherein the length of the entire impedance assembly 2 is about 32 cm.

Unlike the single-layer PCB 130 of the first impedance component 1, the PCB 131 of the second impedance component 2 is a multi-layer PCB. It includes three flat parallel dielectric slab layers 210,215,220 in the PCB substrate, an upper dielectric slab layer 210, a center dielectric slab layer 215, and a lower dielectric slab layer 220. Dielectric slab layers 210,215,220 are comprised of a non-conductive ceramic material.

Five voltage dividing capacitors 91 are electrically connected in series between the high voltage contact 100 and the low voltage contact 110. These voltage dividing capacitors 91 are operable as the high voltage side 60 of the voltage divider 50 for sensing the voltage of the inner conductor 10 of the power cable 20, as shown in fig. 1.

Each of the voltage dividing capacitors 91 is formed of four opposing conductive regions. This will be described with respect to the leftmost voltage dividing capacitor 91 a. All other voltage dividing capacitors 91 are formed in a similar manner.

The leftmost voltage dividing capacitor 91a (in fig. 3) has two electrodes. The first electrode includes a portion of a first conductive region 301 on the upper surface 140 of the upper dielectric slab layer 210 of the PCB 131 and an opposing portion of a second conductive region 302 between the lower dielectric slab layer 220 and the center dielectric slab layer 215. The first conductive region 301 and the second conductive region 302 are electrically connected to each other by a via 310 connecting the conductive regions along the thickness (z-) direction 170.

The second electrode of voltage divider capacitor 91a includes a portion of third conductive region 303 disposed between upper dielectric plate layer 210 and center dielectric plate layer 215, and a portion of fourth conductive region 304 on outer surface 150 of lower dielectric plate layer 220 of PCB 131. The third conductive region 303 and the fourth conductive region 304 are not conductively connected to each other or to another element, but rather are at a floating potential. Only this portion of each respective conductive region 301,302,303,304 forms a voltage dividing capacitor 91a that overlaps the other three conductive regions 301,302,303, 304. The size of the overlapping area of the four conductive regions 301,302,303,304 forming the voltage dividing capacitor 91a is about 30mm in the length direction 160 (indicated by the bracket 320), and about 20mm in the width direction. Each of the voltage dividing capacitors 91 has a capacitance of about 100pF, so that the combined capacitance of five voltage dividing capacitors 91 connected in series between the high-voltage contact 100 and the low-voltage contact 110 is about 20 pF.

The portions of dielectric plate layers 210,215,220 of PCB 131 between first conductive region 301 and third conductive region 303, between third conductive region 303 and second conductive region 302, and between second conductive region 302 and fourth conductive region 304 form the dielectric of the leftmost voltage-dividing capacitor 91 a. The dielectrics of the other voltage dividing capacitors 91 are formed in the same way by other parts of the respective dielectric slab layer 210,215,220 on which the electrodes of the respective voltage dividing capacitors 91 are arranged.

The ceramic material of dielectric slab layers 210,215,220 has a relative permittivity epsilon of about 4.0_r. Since this material is a ceramic material, its coefficient of thermal expansion is relatively low, which results in less change in the distance between the opposing conductive areas with temperature change, resulting in less change in the capacitance of the voltage dividing capacitor 91. In addition, the electrical characteristics of the ceramic substrate typically change less at ambient humidity than, for example, the electrical characteristics of a polymer substrate, which reduces the change in the relative permittivity of the dielectric of the voltage dividing capacitor 91 and thus reduces the corresponding change in capacitance of the voltage dividing capacitor 91 with changes in humidity.

The adjacent voltage dividing capacitor 91b (second from the left in fig. 3) is formed by a similar arrangement of conductive areas as the leftmost voltage dividing capacitor 91 a: a first electrode is formed on a portion of the fifth conductive region 305 and a portion of the sixth conductive region 306 on the top surface 140 of the upper dielectric slab 210 (disposed between the central dielectric slab 215 and the lower dielectric slab 220). A portion of the third conductive region 303 and an opposite portion of the fourth conductive region 304 form a second electrode of the adjacent voltage dividing capacitor 91 b.

The leftmost voltage-dividing capacitor 91a and the adjacent voltage-dividing capacitor 91b are electrically connected in series with each other through the third conductive region 303 and the fourth conductive region 304 extending between the voltage-dividing capacitors, and their respective portions form an electrode of the leftmost voltage-dividing capacitor 91a and an electrode of the adjacent voltage-dividing capacitor 91 b. The same applies to the other pairs of adjacent voltage dividing capacitors 91. Thus, the resulting chain of voltage dividing capacitors 91 of the second impedance component 2 (i.e., including the leftmost voltage dividing capacitors 91a and 91b) is formed of five voltage dividing capacitors 91 electrically connected in series with each other.

The additional conductive areas 302,303,306 inside the PCB 131 of the second impedance component 2 contribute to increasing the capacitance of the respective voltage dividing capacitor 91 compared to the first impedance component 1. However, the distance in the z (thickness) direction between two opposite conductive areas in the second impedance component 2 is smaller than the corresponding distance between opposite conductive areas in the first impedance component 1. A smaller distance results in a higher risk of discharge between opposing conductive regions, such as between the first conductive region 301 and the third conductive region 303. Thus, in order to obtain a suitable voltage division ratio of the voltage divider and at the same time limit the risk of discharges, a suitable number of conductive areas (such as conductive areas 302, 303) inside the PCB 131 can be determined by calculation and standard experiments.

To further reduce the risk of electrical discharges between the elements of the impedance assembly according to the present disclosure, the impedance assembly may be embedded in a non-conductive encapsulation material. Such an embodiment is shown in a longitudinal sectional view in fig. 4. It shows a third impedance component 3 embedded in a body 230 of encapsulation material, similar to the first impedance component 1 of fig. 2.

The third impedance component 3 differs from the first impedance component 1 in that it has four voltage dividing capacitors 90, indicated by capacitor symbols in dashed lines, which are connected in series with each other to form the high voltage side 60 of the voltage divider 50. The four voltage dividing capacitors 90 are formed by opposing conductive areas 201,202, 203, 204, 205 disposed on the outer surface of a single dielectric plate layer 209 of the PCB 130. For example, a portion of the third conductive region 203 overlapping with an opposite portion of the fourth conductive region 204 forms one electrode of the voltage dividing capacitor 90, wherein the overlapping portion of the fourth conductive region 204 forms the other electrode of the voltage dividing capacitor 90. The portion of (only) dielectric plate layer 209 of PCB 130 located between these two overlapping portions of conductive areas 203, 204 forms the dielectric of the voltage dividing capacitor 90.

The encapsulating material is an electrically insulating hardened casting resin. While the casting resin is still liquid, it is applied in a suitably shaped mold around the impedance component 3 and then allowed to harden to become the solid body 230. The mold is shaped such that body 230 leaves first end portion 180 and second end portion 190 free. In case the impedance component 3 is designed to be received in a longitudinal cavity of the elastic sleeve, the main body 230 is shaped such that its outer shape corresponds to the shape of the cavity of the elastic sleeve in which the impedance component 3 and its enclosing main body 230 are to be received.

The dielectric strength of the package body 230 is higher than that of air, so that the possibility of discharge between elements (e.g., the voltage dividing capacitor 90) within the package body 230 is less than that in air.

In order to keep the high voltage contact 100 and the low voltage contact 110 accessible (e.g. for connection of wires), only about 85% of the length L of the impedance assembly 3 is embedded in the encapsulation material. The end portions 180, 190 of the impedance assembly 3 remain free of encapsulation material.

Fig. 5 shows in perspective view how an impedance assembly according to the present disclosure may be accommodated in a cavity of an elastic sleeve, thereby forming a sensing cable accessory 500. The elongate tubular resilient sleeve 260 forms a longitudinal channel 270 in which the inner conductor 10 of the cable 20 can be received. The sleeve 260 is made of EPDM and electrically insulates the inner conductor 10. The sleeve 260 also forms a longitudinal cavity 280 that extends parallel to the length direction 160 of the channel 270 in the length direction 160 of the sleeve 260. An impedance component 4, such as the impedance components shown in fig. 2,3 and 4, is received in the cavity 280. The second end portion 190 of the impedance assembly 4 protrudes from the cavity 280 such that the low voltage contact 110 is accessible from outside the sleeve 260 for connection to the low voltage side 70 of the voltage divider 50. The wire 330 is connected to the high voltage contact 100 of the impedance assembly 4. The other end of the wire protrudes from the cavity 280 and may be connected to the inner conductor 10 of the power cable 20 or to a cable lug at the end of the power cable 20 to sense the AC high voltage of the inner conductor 10 of the power cable 20 to ground.

Fig. 6 is a diagram showing a longitudinal sectional view of the fifth impedance component 5 embedded in the encapsulating material 230 provided with the divided screen. The fifth impedance component 5 is identical to the third impedance component 3 of fig. 4. The encapsulation material 230 is the same as the encapsulation material 230 of fig. 4, except that the outer surface 340 of the encapsulation material 230 is provided with a split screen to reduce parasitic currents.

In the length (x-) direction 160 of the elongated impedance component 5, the outer surface 340 of the encapsulation material 230 is subdivided into three regions: a first surface area 350 covered with a first conductive layer 400 made of copper. The first conductive layer 400 extends circumferentially around and thereby encapsulates the high voltage portion, i.e., the left side portion (in fig. 6), of the impedance component 5.

The first conductive layer 400 may be connected to the high voltage of the power carrying conductor via a high voltage contact 100 and a first spring contact 420 attached to the high voltage contact 100 and establishing surface contact with the first conductive layer 400. In use, when the high voltage contact 100 is electrically connected to a power carrying conductor, the high voltage of the power carrying conductor is present on the first conductive layer 400.

A second surface area 360 of the encapsulation material 230 spaced apart from the first surface area 350 in the length direction 160 is covered with a second conductive copper layer 410. The second conductive layer 410 extends circumferentially around and thereby encapsulates the low voltage portion, i.e. the right side portion (in fig. 6), of the impedance component 5.

The second conductive layer 410 may be connected to electrical ground via the low voltage contact 110 and a second spring contact 430 that is attached to the low voltage contact 110 and establishes surface contact with the second conductive layer 410. In use, when the low voltage contact 110 is electrically connected to ground, a ground potential is present on the second conductive layer 410.

The third surface area 370 is longitudinally arranged between the first surface area 350 and the second surface area 360 of the encapsulating material 230. There is no conductive layer in the third surface area 370, such that the third surface area 370 is electrically insulating. This third surface area forms a non-conductive gap between the first surface area 350 and the second surface area 360 and thereby electrically insulates the first surface area 350 and the second surface area 360 from each other. In fig. 6, the third surface area 370 is shown uncovered. Alternatively, the third surface area may be covered with an electrically insulating layer.

The extension of the third surface area 370 in the length direction 160, i.e. the width of the insulation gap, may be selected as practical and is suitably used to avoid discharges between the first surface area 350 and the second surface area 360 across the insulation gap 370. In case the high voltage contact 100 is at a high voltage of about 20kV and the impedance component 5 and its encapsulation material 230 are accommodated in a tight fitting of a non-conductive silicone rubber, the width of the insulation gap 370 may be, for example, about 50 mm. The insulation gap 370 may be narrower for lower voltages and preferably wider for higher voltages. Without a tight fit silicone rubber around the potting material 230, the insulation gap 370 should generally be wider to reduce the risk of discharge.

The conductive layers 400, 410 may be formed, for example, by thin layers of copper vapor deposited on the respective surface portions 350, 360 of the outer surface 340 of the encapsulation material 230.

Another embodiment of an impedance assembly according to the present disclosure is shown in a top view in fig. 7. The sixth impedance component 6 may be used as part of a resistive voltage divider for sensing the high voltage of an inner conductor of the power cable 20, such as the inner conductor shown in fig. 1. The sixth impedance component 6 has an elongated shape and extends lengthwise between a first end portion 180 and an opposite second end portion 190. The length (x) direction of the impedance component 3 is indicated by arrow 160 and its width (y) direction is indicated by arrow 175. The thickness direction is orthogonal to the length direction 160 and the width direction 175. The sixth impedance component 6 is a resistor component. This sixth resistor assembly is designed to be received in a longitudinal cavity 280 of the elastic sleeve 260 for insulating the power cable.

The sixth impedance component 6 comprises a resistor layer 240 arranged on an outer surface of the substrate 130 (i.e. the PCB 130) and extending between the first end portion 180 and the second end portion 190. A high-voltage contact 100 formed as a solder joint 100 is arranged on the first end portion 180 and is designed to be galvanically connected to the inner conductor 10. The sixth impedance assembly 6 comprises two low voltage contacts on the second end portion 190: a first low voltage contact 110 and a second low voltage contact 111. The two low voltage contacts 110,111 are solder points designed to connect to a low voltage of about 10 volts or less. The two low voltage contacts 110,111 are arranged at a distance of about 12cm from the high voltage contact 100. The entire impedance component 6 has a length L of about 14 cm.

Resistor layer 240 provides a resistance of about 200M omega over its length. The resistor layer is electrically connected in series between the high voltage contact 100 and the first low voltage contact 110. Resistor layer 240 is made of a high resistance coating (such as nichrome) on PCB 130. The resistor layer can operate as the high voltage side of a voltage divider, such as voltage divider 50 shown in fig. 1, between the low voltage (or ground) and the high voltage of the inner conductor 10 of the cable 20. The high voltage at the high voltage contact 100 is split to about 10 volts at the first low voltage contact 110. The large surface of the resistor layer 240 efficiently dissipates heat.

The sixth impedance component 6 comprises a further resistor, i.e. a low voltage resistor 250, which is also formed as a surface resistor on the outer surface of the PCB 130. The low voltage resistor 250 has a resistance of about 20k omega. The low voltage resistor is connected in series between the high voltage contact 100 and the second low voltage contact 111. The low voltage resistor is capable of operating as the low voltage side of a voltage divider between high voltage and ground. The second low-voltage contact 111 is a pad adapted to be connected to an electrical ground. Thus, the sixth impedance component 6 comprises the entire resistor divider, i.e. the high side 60 and the low side 70. The first low voltage contact 110 may be an access point of the resistive divider and the output voltage measured with respect to electrical ground picked up from the first low voltage contact 110 is proportional to the high voltage of the inner conductor 10 by a scaling factor which is the division ratio between the resistance of the low voltage resistor 250 and the resistance of the resistor layer 240, so that 20k Ω/200M Ω is 1: 10000.