阅读说明：本技术 具备输出电容电流信号功能的电容式电压互感器 (Capacitance voltage transformer with function of outputting capacitance current signal ) 是由 张小庆 王冲 刘坤雄 段建东 李丰仪 赵铭 于 2021-09-29 设计创作，主要内容包括：本发明公开了一种具备电容电流输出功能的电容式电压互感器,该互感器主要包括电容分压器、电磁单元、二次接线箱、内置电流传感器、载波附件、防干扰传输线以及监测装置；其连接结构为：电容式电压互感器的低压端子和载波端子与电磁单元相应的端子相连；电磁单元的输出端子由二次接线箱引出；内置电流传感器的输入端子为二次接线箱中的三个输出端子；载波附件串联接在电容分压器的低压端与接地端之间；防干扰传输线与内置电流传感器的四个输出端子和监测装置的电流采集输入口相连,将电容电流信号送入监测装置中。本发明主要解决了利用CVT测量谐波电压的各种方法存在诸如无法离线测量、运行成本高、忽略电磁单元及等值电阻影响等问题。(The invention discloses a capacitive voltage transformer with a capacitive current output function, which mainly comprises a capacitive voltage divider, an electromagnetic unit, a secondary junction box, a built-in current sensor, a carrier accessory, an anti-interference transmission line and a monitoring device, wherein the capacitive voltage divider is arranged on the capacitive voltage transformer; the connection structure is as follows: a low-voltage terminal and a carrier terminal of the capacitor voltage transformer are connected with corresponding terminals of the electromagnetic unit; the output terminal of the electromagnetic unit is led out from the secondary junction box; the input terminals of the built-in current sensor are three output terminals in the secondary junction box; the carrier accessory is connected in series between the low-voltage end and the grounding end of the capacitive voltage divider; the anti-interference transmission line is connected with four output terminals of the built-in current sensor and a current acquisition input port of the monitoring device, and sends a capacitance current signal into the monitoring device. The invention mainly solves the problems that various methods for measuring harmonic voltage by using the CVT cannot perform off-line measurement, have high operation cost, neglect the influence of an electromagnetic unit and equivalent resistance and the like.)

1. The capacitive voltage transformer with the capacitive current output function is characterized by comprising a capacitive voltage divider (1), an electromagnetic unit (2), a secondary junction box (3) and a built-in current sensor (4), wherein the built-in current sensor (4) is arranged in the secondary junction box (3), the capacitive voltage divider (1) comprises a high-voltage capacitor C1 and a low-voltage capacitor C2 which are electrically connected, one end of the low-voltage capacitor C2 connected with the high-voltage capacitor C1 is a low-voltage terminal A ', the other end of the low-voltage capacitor C2 connected with the high-voltage capacitor C1 is connected with a carrier communication terminal N, the low-voltage terminal A ' is led to the secondary junction box (3) to be connected with a terminal A ' of the electromagnetic unit (2), a low-voltage terminal XL, the carrier communication terminal N and a grounding end of the electromagnetic unit (2) are respectively connected with a terminal X, a terminal and a terminal G of an input port of the built-in current sensor (4), and a primary input port NI-X formed by the terminal of the built-in current sensor (4) corresponds to a secondary sub-X The side output ports P3-P4, and the input ports X-G formed by the terminal X of the primary side and the terminal G correspond to the secondary side output ports P1-P2.

2. The capacitive voltage transformer with capacitive current output function according to claim 1, characterized in that a carrier accessory (5) is arranged in the secondary junction box (3).

3. The capacitive voltage transformer with the capacitance current output function according to claim 1, wherein the output port of the built-in current sensor (4) is connected to a monitoring device (7) through a transmission line, and the monitoring device (7) is configured to receive a current signal output from the output port of the built-in current sensor (4) and calculate the low-voltage capacitance current and the CVT primary side total voltage according to the received current signal.

4. The capacitive voltage transformer with capacitive current output function of claim 3, wherein said transmission line is an anti-interference transmission line.

5. The capacitive voltage transformer with capacitive current output function of claim 1, wherein the medium of the high voltage capacitor C1 and the low voltage capacitor C2 is a polypropylene film and capacitor paper composite material.

6. The capacitive voltage transformer with the function of outputting capacitance and current according to claim 1, characterized in that the electromagnetic unit (2) comprises a medium voltage transformer T, a compensation reactor L, a protection device P and a damping device D, wherein the compensation reactor L is connected with the protection device P in parallel and is connected with a primary winding of the intermediate transformer T in series, the damping device D is connected in parallel in a secondary winding of the intermediate transformer T, and the medium voltage transformer T adopts an outer yoke inner iron type three-column iron core.

7. The capacitive voltage transformer with the capacitance-current output function according to claim 6, wherein the compensation reactor L is a C-shaped iron core.

8. The capacitive voltage transformer with the capacitance current output function according to claim 6, wherein a protection device zinc oxide valve plate lightning arrester is arranged at two ends of the compensation reactor L.

9. The capacitive voltage transformer with capacitive current output function according to claim 6, wherein said damping device D is a fast saturation type damper.

10. The capacitive voltage transformer with capacitive current output function according to claim 1, wherein the built-in current sensor (4) is of a straight-through structure.

Technical Field

The invention belongs to the field of transformers, and particularly relates to a capacitor voltage transformer with a capacitance current output function.

Background

At present, in a high-voltage grade power grid of 110kV and above, the number of Capacitor Voltage Transformers (CVT) and electromagnetic voltage transformers (IVT) used for a national grid harmonic monitoring and analyzing module is 2710 and 1155 respectively, so that it can be seen that the CVT occupies an absolute position in terms of providing a data source for power quality monitoring. Therefore, how to accurately measure the harmonic wave by using the CVT becomes a key problem in the field of power quality measurement, and the aim of high-quality, low-cost and high-efficiency online operation is achieved, so that the operation condition of the CVT can be monitored.

To solve the above problems, there are three common solutions: a frequency characteristic correction method, a newly added C3 method, and a capacitance current method. The frequency characteristic correction method corrects the secondary voltage according to the frequency characteristic curve, can obtain more accurate primary side voltage, but has the defects that the method cannot realize online monitoring, is influenced by the model of the CVT, and has large experimental data volume and long experimental period; the newly-added C3 capacitance method is that a capacitance C3 is added at a low-voltage terminal of a capacitance voltage divider, voltages at two ends of a C3 capacitance are obtained according to a voltage dividing principle, and then a primary side voltage is obtained through derivation, online monitoring can be achieved, but the influence of an electromagnetic unit on a measurement result is ignored, an existing CVT needs to be modified, and the cost is high; the capacitance current method is to calculate and obtain voltage by adopting capacitance current flowing through a capacitance voltage divider and combining the capacitance value of the capacitance, the method does not need to modify the internal structure of the CVT and can carry out on-line monitoring of the on-line network, but the capacitance in the current voltage calculation method is regarded as an ideal capacitance, the capacitance in the capacitance voltage divider does not meet the ideal capacitance condition when in actual operation, the actual model is the series-parallel connection mode of the capacitance and the resistance, so the influence of the equivalent resistance of the capacitance needs to be considered, a real-time reliable capacitance current signal needs to be obtained for the purpose, and the more accurate primary side voltage can be calculated and obtained by analyzing the capacitance current signal.

In summary, the conventional capacitance-current method has the problem of neglecting the equivalent resistance of the capacitor, and the key for solving the problem is how to obtain a real-time and reliable capacitance-current signal, and by analyzing the capacitance-current signal, a calculation formula can be corrected to obtain more accurate primary side voltage.

Disclosure of Invention

The invention mainly solves the problems that various methods for measuring harmonic voltage by using the CVT at present cannot perform off-line measurement, have high operation cost and neglect the influence of an electromagnetic unit and an equivalent resistor, and obtains accurate capacitance current signals through measurement.

In order to achieve the above object, the capacitive voltage transformer with capacitive current output function according to the present invention comprises a capacitive voltage divider, an electromagnetic unit, a secondary junction box and a built-in current sensor, wherein the built-in current sensor is disposed in the secondary junction box, the capacitive voltage divider comprises a high-voltage capacitor C1 and a low-voltage capacitor C2 which are electrically connected, one end of the low-voltage capacitor C2 and the high-voltage capacitor C1 which are connected is a low-voltage terminal a', the other end of the low-voltage capacitor C2 and the high-voltage capacitor C1 which are connected is connected to a carrier communication terminal N, the low-voltage terminal XL, the carrier communication terminal N and a ground terminal of the electromagnetic unit are respectively connected to a terminal X, a terminal NI and a terminal G of an input port of the built-in current sensor, a primary input port NI-X formed by the terminal NI and the terminal X corresponds to a secondary output port P3-P4, the input ports X-G formed by the terminal X and the terminal G on the primary side correspond to the output ports P1-P2 on the secondary side.

Furthermore, a carrier accessory is arranged in the secondary junction box.

Furthermore, the output port of the built-in current sensor is connected with a monitoring device through a transmission line, and the monitoring device is used for receiving a current signal output by the output port of the built-in current sensor and calculating the low-voltage capacitance current and the total voltage of the primary side of the CVT according to the received current signal.

Further, the transmission line is an interference-proof transmission line.

Furthermore, the medium of the high-voltage capacitor C1 and the low-voltage capacitor C2 is a polypropylene film and capacitor paper composite material.

Further, the electromagnetic unit comprises a medium-voltage transformer T, a compensation reactor L, a protection device P and a damping device D, wherein the compensation reactor L is connected with the protection device P in parallel and is connected with a primary side winding of the intermediate transformer T in series, the damping device D is connected in parallel in a secondary winding of the intermediate transformer T, and the medium-voltage transformer T adopts an outer yoke inner iron type three-column iron core.

Further, the compensation reactor L is a C-shaped iron core.

Furthermore, two ends of the compensation reactor L are provided with a lightning arrester with zinc oxide valve plates as protection devices.

Further, the damping device D is a fast saturation type damper.

Furthermore, the built-in current sensor adopts a through structure.

Compared with the prior art, the invention has at least the following beneficial technical effects:

(1) the input terminal with built-in current sensor replaces the binding post of CVT secondary junction box, conveniently acquire the electric capacity current signal on the basis of not reforming transform CVT own structure, practice thrift the transformation cost, realize CVT electric capacity current signal's online acquisition and processing, direct at the direct mount current sensor of CVT secondary junction box's terminal department, do not receive electromagnetic interference's influence, the operational environment is comparatively stable, reduce the error that the collection in-process produced, and be applicable to on-the-spot operation and measurement.

(2) The influence of the equivalent resistance of the capacitor in actual operation is considered, the dielectric loss angle of the corresponding capacitor is obtained by analyzing the collected current signal, the resistance value of the equivalent resistance of the capacitor is further calculated, a calculation formula for reducing the primary side voltage by a capacitance-current method is corrected, and the calculated primary side voltage is more accurate.

(3) According to the micro-current sensor capable of being arranged in the secondary junction box, the output terminal of the CVT can be directly butted with the input terminal of the CVT, so that the CVT has capacitance current signal output capacity, the CVT is conveyed through the anti-interference transmission line, the influence caused by electromagnetic interference can be avoided, the obtained accurate capacitance current signal can monitor the operation state of the capacitor unit, and the primary side reduction voltage result is corrected.

Furthermore, the built-in current sensor adopts a through structure, the structure can not change the original wiring mode of the tested equipment, the safety in measurement is higher, and the anti-interference capability is strong.

Drawings

FIG. 1 is a schematic diagram of the operation of a capacitive voltage transformer with capacitive current output function according to the present invention;

FIG. 2 is a schematic diagram of a capacitive voltage transformer with a capacitive current output function according to the present invention;

FIG. 3 is a diagram of the structural wiring within the secondary junction box of the present invention;

fig. 4 is a schematic diagram of the built-in current sensor of the present invention.

In the drawings: 1-a capacitive voltage divider; 2-an electromagnetic unit; 3-a secondary junction box; 4-built-in current sensor; 5-a carrier accessory; 6-anti-interference transmission line; 7-monitoring device.

Detailed Description

In order to make the objects and technical solutions of the present invention clearer and easier to understand. The present invention will be described in further detail with reference to the following drawings and examples, wherein the specific examples are provided for illustrative purposes only and are not intended to limit the present invention.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, and are used only for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The concrete connection mode of each part of the invention is as follows: referring to fig. 1 and 2, a capacitive voltage transformer with a capacitive current output function is composed of a capacitive voltage divider 1, an electromagnetic unit 2, a secondary connection box 3, a built-in current sensor 4, a carrier attachment 5, an anti-interference transmission line 6 and a monitoring device 7.

The connection structure is as follows: a high-voltage terminal A of the capacitive voltage divider 1 is connected with a power grid, and a low-voltage terminal A 'and a carrier terminal N of the capacitive voltage divider 1 are led out from a small porcelain bushing on a bottom cover of the capacitive voltage divider 1 to be connected with corresponding terminals A' and N in the electromagnetic unit 2; the medium-voltage terminal of the electromagnetic unit 2 and the low-voltage terminal A' of the capacitive voltage divider 1 are the same terminal, and the low-voltage terminal XL of the electromagnetic unit is led out from the secondary junction box 3; three inputs of secondary junction box 3A low-voltage terminal XL, a carrier communication terminal N and a grounding terminal of the terminal electromagnetic unit 2 are respectively butted with input ports X, NI and G of the built-in current sensor 4; the carrier accessory 5 comprises a drainage coil and a voltage limiting device which are connected in series between a low-voltage terminal A' of the capacitive voltage divider 1 and a ground terminal and are used for injecting carrier signals, so that the CVT signal output is more stable; the interference prevention transmission line 6 is connected to four output terminals P1, P2, P3 and P4 of the built-in current sensor 4, and outputs a measured current signal i flowing through the high-voltage capacitor C1_C1(t) and the current i flowing through the electromagnetic unit 2_e(t); the anti-interference transmission line 6 is connected with a current acquisition input port of the monitoring device 7 and sends a current signal into the monitoring device 7.

The capacitor voltage transformer comprises a capacitive voltage divider 1, an electromagnetic unit 2 and a secondary junction box 3, wherein a built-in current sensor 4 and a carrier accessory 5 are arranged in the secondary junction box 3, and an output pin of the built-in current sensor 4 is connected with a monitoring device 7 through an anti-interference transmission line 6. The capacitive voltage divider 1 is formed by connecting one or more capacitors in series and is divided into a high-voltage capacitor C1 and a low-voltage capacitor C2, the medium of the capacitor is compounded and impregnated with a polypropylene film and capacitor paper, a high-voltage terminal A is arranged at the top end of the capacitive voltage divider 1, and the high-voltage terminal A of the capacitive voltage divider 1 is connected with a power grid, so that the capacitive voltage transformer is connected to the power grid. A low-voltage terminal A 'of the capacitor voltage transformer is led out from a small porcelain bushing on the bottom cover of the capacitive voltage divider 1 to the electromagnetic unit 2 to be connected with the corresponding terminal A', and a grounding terminal is led out from a secondary junction box 3.

The electromagnetic unit 2 is composed of a medium voltage transformer T, a compensation reactor L, a protection device P, a damping device D for inhibiting ferromagnetic resonance and an oil tank. The compensation reactor L is connected in parallel with the protection device P and is connected in series with the primary side winding of the intermediate transformer T, the damping device D is connected in parallel with the secondary winding of the intermediate transformer T, and the secondary winding of the intermediate transformer T has four windings which are respectively 1a1n, 2a2n, 3a3n and dadn. The terminals 1a, 1n, 2a, 2n, 3a, 3n, da, dn are led out from the secondary connection box 3.

The medium-voltage transformer, the compensation reactor and the damping device are all arranged in the oil tank, the medium-voltage transformer adopts an outer yoke inner iron type three-column iron core, the iron core adopts a high-quality cold-rolled silicon steel sheet, and the winding arrangement sequence is a core column, an auxiliary winding, a secondary winding and a high-voltage winding; the compensation reactor is connected in series with the grounding end of the primary winding of the intermediate transformer, a C-shaped iron core is adopted, the inductive reactance value of the compensation reactor is equal to the capacitive reactance value of a high-voltage capacitor C1 and a low-voltage capacitor C2 in the capacitive voltage divider 1 in parallel, and two ends of the compensation reactor are provided with a zinc oxide valve plate lightning arrester of a protection device; the damping device is a fast saturation type damper, and a permalloy iron core is applied to be connected to a residual voltage winding of the intermediate transformer.

The medium-voltage terminal of the electromagnetic unit 2 is the same as the low-voltage terminal A 'of the capacitive voltage divider, the current flowing through the high-voltage capacitor C1 flows into the electromagnetic unit 2 from the low-voltage terminal A' of the capacitive voltage divider 1, and the current share the carrier communication terminal N; the secondary winding terminal and the carrier communication terminal of the electromagnetic unit 2 are led out from a secondary junction box 3 on the front surface of the oil tank; the secondary junction box 3 comprises an electromagnetic unit 2, a secondary winding wiring terminal, a connecting wire, a grounding bolt, a cable inlet and a built-in micro-current transformer 4, and low-voltage capacitance current i flowing through three output terminals XL, N and a grounding terminal of the secondary junction box 3 can be collected_C2(t) and electromagnetic unit current i_e(t) wherein the low voltage capacitance current i_C2(t) and electromagnetic unit current i_eAnd (t) is collected by the built-in current sensor 4 and is transmitted to the monitoring device 7.

Referring to fig. 4, the built-in current sensor 4 adopts a through structure, and the structure can not change the original wiring mode of the tested device, has higher safety in measurement and strong anti-interference capability. The sensor utilizes the principle of a traditional ferromagnetic current transformer and comprises a primary side and two secondary sides, wherein input ports of the primary side are X, NI and G, and output ports of the secondary sides are P1, P2, P3 and P4. The primary input port NI-X corresponds to the secondary output ports P3-P4, and the primary input port X-G corresponds to the secondary output ports P1-P2.

The primary side of the CVT secondary connection box is provided with 3 input ports, namely NI, X and G, which are respectively connected with a carrier communication terminal N, an electromagnetic unit low-voltage end XL and a grounding end in the CVT secondary connection box 3; the capacitive voltage transformer has the function of sensing the current of the capacitive voltage transformer in real time, the secondary side of the capacitive voltage transformer is provided with 4 output pins which are P1, P2, P3 and P4 respectively, and the current flowing through the input port X-G is the current of an electromagnetic uniti_e(t), the corresponding secondary output pins are P1-P2; the current flowing through the input port NI-X in the original side is high-voltage capacitance current i_C1(t), the corresponding secondary output pins are P3-P4.

Under the normal condition, the currents of the high-voltage capacitor C1 and the low-voltage capacitor C2 in the 35 kV-750 kV CVT are in the range of 60 mA-700 mA, and the small signal used for measurement in engineering is 1mA, so that the primary current of the micro-current sensor is transmitted to the secondary side according to the transformation ratio of 1000:1, and the measuring range is 0-1A. The built-in current sensor 4 has a small overall size, the external dimension is only 64mm multiplied by 58mm multiplied by 35mm (width multiplied by height multiplied by depth), so that the built-in current sensor can be completely built in a CVT secondary terminal box, and a connecting wire between CVT primary secondary terminals is replaced, thereby not only realizing the interconnection effect of the CVT secondary terminals, but also realizing the current measurement function;

the carrier accessory 5 comprises a drain coil and a voltage-limiting device, and is connected between the low-voltage terminal and the ground terminal of the voltage divider 1.

The anti-interference transmission line 6 is connected with the output port of the built-in current sensor 4 and the input port of the monitoring device 7, and transmits the current signal into the monitoring device 7 for processing.

The monitoring device 7 comprises a current acquisition module, a data processing module and a monitoring module, wherein the current acquisition module is connected with the data processing module, the current acquisition module receives a current signal transmitted by the anti-interference transmission line 6, the data processing module analyzes and calculates the current signal to obtain a dielectric loss angle of a capacitor in the capacitive voltage divider, a series equivalent resistance of the capacitor is calculated and corrected according to a primary side voltage reduction formula, and the monitoring module is connected with the current acquisition module and the data processing module to monitor data. The results after correction are shown in formulas (1) to (4):

i_C2(t)＝i_C1(t)-i_e(t) (2)

u₁(t)＝u_C1(t)+u_C2(t) (4)

wherein i_C2(t) is the capacitance current flowing through the low-voltage capacitor C2, i_C1(t) is a capacitance current flowing through the high-voltage capacitor C1, i_e(t) is the current flowing through the electromagnetic unit, u_C2(t) is the voltage across the low-voltage capacitor, u_C1(t) is the voltage across the high-voltage capacitor, u₁(t) is the total primary side voltage of the CVT, R_C1Is the equivalent resistance of the high-voltage capacitor, R_C2Is the equivalent resistance, delta, of the low-voltage capacitor_C1Is the dielectric loss angle, delta, of the high-voltage capacitor C1_C2The dielectric loss angle of the low-voltage capacitor is shown, and f is the measuring frequency.

Theory of operation analysis

The invention is composed of a capacitive voltage divider 1, an electromagnetic unit 2, a secondary junction box 3, a built-in micro-current transformer 4, a carrier accessory 5, an anti-interference transmission line 6 and a monitoring device 7. The high-voltage terminal A of the capacitive voltage divider 1 is connected with a power grid, so that the mutual inductor is connected to the power grid, harmonic current in the power grid flows through the high-voltage capacitor C1 in the capacitive voltage divider 1, part of the high-voltage capacitor C1 current flows into the electromagnetic unit 2 through the low-voltage terminal A', and part of the high-voltage capacitor C1 current flows into the grounding terminal and respectively corresponds to the electromagnetic unit current i_e(t) and high voltage capacitance C1 current i_C1(t) of (d). Three input ports NI, X and G of a built-in current sensor 4 respectively correspond to a carrier communication terminal N, an electromagnetic unit low-voltage end XL and a grounding end G in a CVT secondary junction box 3, the sensor is small in size and can be directly installed in the secondary junction box, and the pair of output pins P1-P2 outputs electromagnetic unit current i_e(t), the output pin of P3-P4 outputs high-voltage capacitance current i_C1(t) of (d). Carry current signal to monitoring devices by the jam-proof transmission line according to IEC61850 communication protocol, monitoring devices carries out the analysis and calculation to the current signal who receives, can revise primary side voltage reduction formula. The invention designs a capacitor voltage transformer with a function of outputting a capacitance current signal, which can realize the on-line acquisition and monitoring of the current signal of the capacitor voltage transformer and directly realize the on-line acquisition and monitoring of the current signal of the capacitor voltage transformer in a CVT secondary connection boxThe terminal of (2) is provided with a micro-current sensor, so that the error generated in the acquisition process is reduced, and the terminal is suitable for field operation and measurement.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.