阅读说明：本技术 超低频余弦方波发生装置及其驱动方法 (Ultralow frequency cosine square wave generating device and driving method thereof ) 是由 吕启深 张�林 李艳 伍国兴 于 2021-07-01 设计创作，主要内容包括：本发明涉及一种超低频余弦方波发生装置及其驱动方法。该超低频余弦方波发生装置包括：高压电源模块,用于分时输出正向高压和负向高压；电抗器,一端与高压电源模块连接,另一端用于连接电缆,电抗器用于根据接收到的正向高压和负向高压,使得电缆产生超低频余弦方波信号；控制模块,一端与高压电源模块和电抗器之间的控制节点连接,另一端用于接地,控制模块用于在高压电源模块不输出正向高压且不输出负向高压时,对控制节点的电平状态进行翻转,以完成电缆上的正向高压或负向高压的换向。有利于对高压输电电缆的局部放电检测。(The invention relates to an ultralow-frequency cosine square wave generating device and a driving method thereof. The ultra-low frequency cosine square wave generating device comprises: the high-voltage power supply module is used for outputting positive high voltage and negative high voltage in a time-sharing manner; one end of the reactor is connected with the high-voltage power supply module, the other end of the reactor is used for connecting a cable, and the reactor is used for enabling the cable to generate an ultralow-frequency cosine square-wave signal according to the received positive high voltage and negative high voltage; and one end of the control module is connected with a control node between the high-voltage power supply module and the reactor, the other end of the control module is grounded, and the control module is used for overturning the level state of the control node when the high-voltage power supply module does not output positive high voltage and negative high voltage so as to complete the reversing of the positive high voltage or the negative high voltage on the cable. The partial discharge detection of the high-voltage transmission cable is facilitated.)

1. An ultra-low frequency cosine square wave generating device is characterized by comprising:

the high-voltage power supply module is used for outputting positive high-voltage and negative high-voltage in a time-sharing manner;

one end of the reactor is connected with the high-voltage power supply module, the other end of the reactor is used for connecting a cable, and the reactor is used for generating an ultralow-frequency cosine square-wave signal on the cable according to the received positive high voltage and the negative high voltage;

and one end of the control module is connected with a control node between the high-voltage power supply module and the reactor, the other end of the control module is grounded, and the control module is used for overturning the level state of the control node when the high-voltage power supply module does not output positive high voltage and negative high voltage so as to complete the reversing of the positive high voltage and the negative high voltage on the cable.

2. The apparatus of claim 1, wherein the control module comprises:

the first high-voltage semiconductor switch is used for controlling the conduction of a current path of the control node flowing to the direction of the grounding end so as to control the control node to be turned from a negative level state to a positive level state;

and one end of the second high-voltage semiconductor switch is connected with the control node, the other end of the second high-voltage semiconductor switch is connected with a grounding end, and the second high-voltage semiconductor switch is used for controlling the conduction of a current path flowing to the direction of the control node from the grounding end so as to control the control node to be turned from a positive level state to a negative level state.

3. The apparatus of claim 2, wherein the first high voltage semiconductor switch comprises:

the collector of the first transistor is connected to ground, the collector of the mth first transistor is connected to the emitter of the (m-1) th first transistor, the emitter of the nth first transistor is connected to the control node, where m is greater than 1 and less than or equal to n, m and n are positive integers, the gate of each first transistor is respectively used for receiving a first control signal, and the first control signal is respectively used for controlling the on-off of each first transistor.

4. The apparatus of claim 3, wherein the second high voltage semiconductor switch comprises:

p second transistors which are connected in series, wherein the collector of the first second transistor is connected with the control node, the collector of the qth second transistor is connected with the emitter of the (m-1) th second transistor, the emitter of the pth second transistor is grounded, q is greater than 1 and is less than or equal to p, q and p are positive integers, the gate of each second transistor is respectively used for receiving a second control signal, and the second control signal is respectively used for controlling the on-off of each second transistor.

5. The apparatus of claim 4, wherein a maximum withstand voltage of each of the first transistors and each of the second transistors is the same.

6. The apparatus of claim 1, wherein the high voltage power supply module comprises:

a direct current power supply configured with a first output terminal for outputting the positive high voltage and a second output terminal for outputting the negative high voltage;

the high-voltage relay unit is configured with a first input end, a second input end and a high-voltage output end, the first input end of the high-voltage relay unit is connected with the first output end of the direct-current power supply, the second input end of the high-voltage relay unit is connected with the second output end of the direct-current power supply, the output end of the high-voltage relay unit is connected with the reactor, and the high-voltage relay unit is used for controlling the output path of the positive high voltage and the output path of the negative high voltage to be conducted in a time-sharing mode.

7. The apparatus of claim 6, wherein the high voltage relay unit comprises two high voltage relay subunits, an input terminal of each of the high voltage relay subunits is connected to a respective output terminal of the dc power source in a one-to-one correspondence, an output terminal of each of the high voltage relay subunits is connected as a node as an output terminal of the high voltage relay unit, and the high voltage relay subunit comprises:

the input end of the first relay circuit is connected with one input end of the high-voltage power supply module, the input end of the second relay circuit is connected with the output end of the (b-1) th relay circuit, the output end of the (a) th relay circuit is connected with the reactor, wherein b is more than 1 and less than or equal to a, and a and b are positive integers.

8. The apparatus of claim 7, wherein the maximum withstand voltage of a plurality of the relay circuits is the same.

9. The device according to claim 1, characterized in that the reactor wire is wound in a bottom-up entanglement manner.

10. A driving method of an ultra low frequency cosine square wave generating device for driving an ultra low frequency cosine square wave generating device according to any one of claims 1 to 9, comprising:

outputting positive high voltage and negative high voltage in a time-sharing manner;

when the positive high voltage is not output and the negative high voltage is not output, the level state of the control node of the ultralow frequency cosine square wave generating device is reversed so as to complete the reversing of the positive high voltage and the negative high voltage on the cable;

and outputting an ultralow-frequency cosine square wave signal to the cable according to the received positive high voltage and the negative high voltage.

Technical Field

The invention relates to the technical field of detection of insulation states of transmission cables, in particular to an ultralow-frequency cosine square wave generating device and a driving method thereof.

Background

With the continuous promotion of China's cabling process, the distribution cable is used as a main artery for the operation of a power grid, and the safety and reliability of the distribution cable are closely related to the life of people. Because the cable is buried underground, once a fault is found, the fault is difficult to find, the time consumption is long, great economic loss is caused, and great inconvenience is caused to daily life of residents, daily production of production departments and normal operation of other social non-production departments.

Partial discharge is the most prominent manifestation form of the early insulation fault of the power cable, and is not only the main cause of insulation aging, but also the main characteristic parameter for representing the insulation condition, therefore, researchers at home and abroad propose a power cable partial discharge detection test with a diagnostic function, and the method is a typical method for detecting latent defects of power equipment.

A relatively mature cable insulation status monitoring strategy has been developed for distribution cables of 35kV and below. However, for the high-voltage transmission cable with the voltage of 110kV and above, the insulation state detection is still in the starting stage, and the development level of insulation state detection equipment for relevant voltage classes at home and abroad has great defects.

Disclosure of Invention

In view of the above, it is desirable to provide an ultra-low frequency cosine square wave generator and a driving method thereof suitable for detecting partial discharge of a high-voltage power transmission cable.

An ultra-low frequency cosine square wave generating device, comprising:

the high-voltage power supply module is used for outputting positive high-voltage and negative high-voltage in a time-sharing manner;

one end of the reactor is connected with the high-voltage power supply module, the other end of the reactor is used for connecting a cable, and the reactor is used for generating an ultralow-frequency cosine square-wave signal on the cable according to the received positive high voltage and negative high voltage;

and one end of the control module is connected with a control node between the high-voltage power supply module and the reactor, the other end of the control module is grounded, and the control module is used for overturning the level state of the control node when the high-voltage power supply module does not output positive high voltage and negative high voltage so as to complete the reversing of the positive high voltage and the negative high voltage on the cable.

In one embodiment, a control module comprises:

the first high-voltage semiconductor switch is used for controlling the conduction of a current path of the control node flowing to the direction of the grounding end so as to control the control node to be turned from a negative level state to a positive level state;

and one end of the second high-voltage semiconductor switch is connected with the control node, the other end of the second high-voltage semiconductor switch is connected with the grounding end, and the second high-voltage semiconductor switch is used for controlling the conduction of a current path flowing from the grounding end to the direction of the control node so as to control the control node to be turned from the positive level state to the negative level state.

In one embodiment, the first high voltage semiconductor switch comprises:

the collector electrode of the first transistor is used for grounding, the collector electrode of the mth first transistor is connected with the emitter electrode of the (m-1) th first transistor, the emitter electrode of the nth first transistor is connected with the control node, wherein m is larger than 1 and smaller than or equal to n, m and n are positive integers, the gate electrode of each first transistor is respectively used for receiving a first control signal, and the first control signal is respectively used for controlling the on-off of each first transistor.

In one embodiment, the second high voltage semiconductor switch comprises:

the p second transistors are connected in series, the collector of the first second transistor is connected with the control node, the collector of the q second transistor is connected with the emitter of the (m-1) th second transistor, the emitter of the p second transistor is grounded, q is more than 1 and less than or equal to p, q and p are positive integers, the gate poles of the second transistors are respectively used for receiving second control signals, and the second control signals are respectively used for controlling the on-off of the second transistors.

In one embodiment, the maximum withstand voltage of each of the first transistors and each of the second transistors is the same.

In one embodiment, a high voltage power supply module includes:

a direct current power supply configured with a first output terminal for outputting a positive high voltage and a second output terminal for outputting a negative high voltage;

the high-voltage relay unit is configured with a first input end, a second input end and a high-voltage output end, the first input end of the high-voltage relay unit is connected with the first output end of the direct-current power supply, the second input end of the high-voltage relay unit is connected with the second output end of the direct-current power supply, the output end of the high-voltage relay unit is connected with the reactor, and the high-voltage relay unit is used for controlling the output path of the positive high voltage and the output path of the negative high voltage to be conducted in a time-sharing mode.

In one embodiment, the high voltage relay unit includes two high voltage relay subunits, the input terminal of each high voltage relay subunit is connected with each output terminal one-to-one of dc power supply respectively, the output terminal of each high voltage relay subunit is connected as the output terminal of node as the high voltage relay unit, and the high voltage relay subunit includes:

the input end of the first relay circuit is connected with one input end of the high-voltage power supply module, the input end of the second relay circuit is connected with the output end of the (b-1) th relay circuit, the output end of the (a) th relay circuit is connected with the reactor, wherein b is more than 1 and less than or equal to a, and a and b are positive integers.

In one embodiment, the maximum withstand voltages of the plurality of relay circuits are the same.

In one embodiment, the wire winding form of the reactor is a bottom-up entanglement type.

A driving method of an ultralow frequency cosine square wave generating device is used for driving the ultralow frequency cosine square wave generating device, and comprises the following steps:

outputting positive high voltage and negative high voltage in a time-sharing manner;

when the positive high voltage and the negative high voltage are not output, the level state of a control node of the ultralow frequency cosine square wave generating device is reversed so as to complete the reversing of the positive high voltage and the negative high voltage on the cable;

and outputting an ultralow-frequency cosine square wave signal to the cable according to the received positive high voltage and negative high voltage.

The ultralow frequency cosine square wave generating device comprises a high-voltage power supply module, a first voltage generating module and a second voltage generating module, wherein the high-voltage power supply module is used for outputting positive high voltage and negative high voltage in a time-sharing manner; one end of the reactor is connected with the high-voltage power supply module, the other end of the reactor is used for connecting a cable, and the reactor is used for outputting an ultralow-frequency cosine square-wave signal to the cable according to the received positive high voltage and negative high voltage; and one end of the control module is connected with a control node between the high-voltage power supply module and the reactor, the other end of the control module is grounded, and the control module is used for overturning the level state of the control node when the high-voltage power supply module does not output positive high voltage and negative high voltage so as to finish steering of the cable for outputting the positive high voltage and the negative high voltage. The cable is charged through the reactor when the forward high voltage is output, the control module conducts the circuit when no voltage is output, the cable is discharged, the level state on a control node between the high-voltage power supply module and the reactor is turned over, at the moment, the forward high voltage on the cable is turned, the high-voltage power supply module outputs reverse voltage to charge the cable in a reverse high voltage mode, and the control module finishes turning after the reverse charging, so that the steps are repeated continuously, the ultralow-frequency cosine square wave is generated, and the partial discharge detection of the cable is finished in the turning process.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of an apparatus for generating an ultra-low frequency cosine square wave according to an embodiment;

FIG. 2 is a circuit diagram of a control module according to an embodiment;

FIG. 3 is a circuit diagram of a high voltage power supply module according to an embodiment;

FIG. 4 is a circuit diagram of a high voltage relay subunit of an embodiment;

FIG. 5 is a circuit diagram of an embodiment of an ultra-low frequency cosine square wave generator;

fig. 6 is a flowchart illustrating a driving method of an ultra-low frequency cosine square wave generator according to an embodiment.

Detailed Description

To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first transistor can be referred to as a second transistor, and similarly, a second transistor can be referred to as a first transistor, without departing from the scope of the present application. The first transistor and the second transistor are both transistors, but they are not the same transistor.

It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.

As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.

As shown in fig. 1, a schematic diagram of an ultra-low frequency cosine square wave generator is provided, and the ultra-low frequency cosine square wave generator 100 includes a high-voltage power module 110, a reactor 130 and a control module 150. The high-voltage power supply module 110 is used for outputting positive high voltage and negative high voltage in a time-sharing manner; one end of the reactor 130 is connected with the high-voltage power supply module, the other end of the reactor 130 is used for connecting a cable, and the reactor 130 is used for enabling the cable to generate an ultralow-frequency cosine square-wave signal according to the received positive high voltage and negative high voltage; one end of the control module 150 is connected to a control node between the high-voltage power supply module and the reactor, and the other end of the control module is grounded, and the control module 150 is configured to turn over a level state of the control node when the high-voltage power supply module does not output a positive high voltage and does not output a negative high voltage, so as to complete steering of outputting the positive high voltage or the negative high voltage to the cable.

Wherein, the inversion of the level state of the control node means that the state at the control node is changed from high level to low level or from low level to high level.

In this embodiment, the high-voltage power module 110 outputs a positive high voltage and a negative high voltage for a certain period of time, the positive high-voltage path and the negative high-voltage path are respectively conducted in a circuit connected with the reactor 130 and the cable, and positive and negative voltages in the circuit are reversed through the control module 150, which is specifically indicated that the level state of a control node connected between the high-voltage power module and the reactor is reversed, so that the voltage on the cable can be reversed in positive and negative directions, and the ultralow frequency cosine square wave signal is obtained by controlling the time of outputting the positive and negative high voltages.

In one embodiment, a circuit diagram of a control module is provided, as shown in FIG. 2. The control module 150 includes a first high voltage semiconductor switch 151 and a second high voltage semiconductor module 153. One end of the first high-voltage semiconductor switch 151 is connected with a control node between the high-voltage power supply module and the reactor, the other end of the first high-voltage semiconductor switch 151 is connected with a ground terminal, and the first high-voltage semiconductor switch 151 is used for controlling the conduction of a current path of the control node flowing to the direction of the ground terminal so as to control the inversion of the control node from a negative level state to a positive level state; one end of the second high-voltage semiconductor module 153 is connected to a control node between the high-voltage power supply module and the reactor, the other end of the second high-voltage semiconductor module 153 is used for connecting to a ground terminal, and the second high-voltage semiconductor module 153 is used for controlling the conduction of a current path flowing from the ground terminal to the direction of the control node, so as to control the inversion of the control node from a positive level state to a negative level state.

In this embodiment, the control module 150 is configured to commutate positive and negative voltages in the circuit through a line connection relationship between one end of the first high-voltage semiconductor switch 151 and one end of the second semiconductor switch 153, which are connected to the ground terminal, when the high-voltage power supply module does not output any voltage to the circuit, so that a series resonance is generated between the reactor 130 and the cable, and the control module can be used for partial discharge detection.

In one embodiment, with continued reference to fig. 2, the first semiconductor switch 151 includes n first transistors T1 connected in series, a collector of the first transistor T1 is used for grounding, a collector of the mth first transistor T1 is connected to an emitter of the m-1 st first transistor T1, and an emitter of the nth first transistor T1 is connected to a control node, where 1 < m ≦ n, m and n are positive integers, gates of the first transistors T1 are respectively used for receiving a first control signal, and the first control signal is respectively used for controlling on/off of the first transistors T1. Specifically, in the embodiment of fig. 2, two first transistors T1 are included.

In this embodiment, the series connection of the plurality of first transistors can reduce the requirement on the withstand voltage limit of a single transistor in a high-voltage circuit.

In one embodiment, with continued reference to fig. 2, the second semiconductor switch 153 includes p second transistors T2 connected in series, the collector of the first second transistor T2 is connected to the control node, the collector of the qth second transistor T2 is connected to the emitter of the m-1 th second transistor T2, the emitter of the pthh second transistor T2 is connected to ground, wherein 1 < q ≦ p, q and p are positive integers, the gates of the second transistors T2 are respectively configured to receive a second control signal, and the second control signals are respectively configured to control the on/off of the second transistors T2. Specifically, in the embodiment of fig. 2, two second transistors T2 are included.

In this embodiment, the series connection of the plurality of second transistors can reduce the requirement on the withstand voltage limit of a single transistor in the high-voltage circuit.

In one embodiment, the maximum withstand voltage of each of the first transistors T1 and the second transistors T2 is the same.

In one embodiment, the first semiconductor switch and the second semiconductor switch further include a first control signal module and a second control signal module, respectively, for outputting a first control signal and a second control signal, respectively, where the first control signal and the second control signal are both transmitted through an optical fiber to control on/off of each of the first transistor and the second transistor, respectively.

In one embodiment, the first semiconductor switch and the second semiconductor switch respectively comprise 24 serially connected optical trigger transistors, each of which has a maximum withstand voltage of 7.5kV and a maximum operating current of 200A.

In one embodiment, to ensure that the local electric field is not too large, two ends of each photo-trigger transistor further include a grading ring for grading certain voltage at two ends of each stage of transistor.

In one embodiment, a circuit diagram of a high voltage power supply module is provided, as shown in fig. 3. The high voltage power supply module 110 includes a direct current power supply 111 and a high voltage relay 113. The direct-current power supply 111 is configured with a first output terminal for outputting a positive high voltage and a second output terminal for outputting a negative high voltage; the high-voltage relay unit 113 is configured with a first input terminal, a second input terminal, and a high-voltage output terminal, the first input terminal of the high-voltage relay unit 113 is connected with the first output terminal of the dc power supply, the second input terminal of the high-voltage relay unit 113 is connected with the second output terminal of the dc power supply 111, the output terminal of the high-voltage relay unit 113 is connected with the reactor 130, and the high-voltage relay unit 113 is configured to control an output path of the positive high voltage and an output path of the negative high voltage to be turned on in a time-sharing manner.

In this embodiment, the high-voltage power supply module 110 can isolate the dc power supply 111 with high voltage from a circuit connected to a subsequent stage through the high-voltage relay unit 113 connected to the dc power supply 111, so as to ensure time-sharing output of positive high voltage and negative high voltage of the dc power supply 111.

In one embodiment, with continued reference to fig. 3, the high voltage relay 113 unit includes two high voltage relay subunits, one of which is connected in series with the input of resistor R1 and the other of which is connected in series with the input of resistor R2. The input ends of the high-voltage relay subunits are correspondingly connected with the output ends of the direct-current power supplies, and the output end connection node of the resistor R1 and the resistor R2 connected to the high-voltage relay subunits is used as the output end of the whole high-voltage relay unit. As shown in fig. 4, a circuit diagram of a high-voltage relay subunit is provided. The high-voltage relay subunit comprises a relay circuits 113A which are connected in series, the input end of the first relay circuit is connected with one input end of the high-voltage power supply module, the input end of the b-th relay circuit is connected with the output end of the b-1-th relay circuit, the output end of the a-th relay circuit is connected with the reactor, wherein b is more than 1 and less than or equal to a, and a and b are positive integers. Specifically, the fig. 4 embodiment includes two relay circuits.

In this embodiment, because the positive high voltage and the negative high voltage in the circuit are in the commutation process, the charge in the dc power supply cannot be released in time, for example, in the process of commutating from the 180kV positive high voltage to the negative high voltage, the 180kV residual charge connected to the dc power supply output positive high voltage output terminal of the first high voltage relay subunit at the front end is not released in time, the output voltage still remains about 180kV in a short time, the cable voltage at the rear end can complete commutation within no more than 20ms to-180 kV, and the voltage difference between the two ends of the first high voltage relay subunit at this time may reach 360kV at most. Therefore, the invention adopts a plurality of relay circuits connected in series to realize the effect of high voltage resistance, thereby playing the role of isolating the direct current power supply from the post-stage circuit and achieving the purpose of protecting the direct current power supply.

In one embodiment, the maximum withstand voltages of the relay circuits are the same.

In one embodiment, the number of the high-voltage relay subunits is 6, the withstand voltage value of each relay circuit is 70kV, and the maximum on-current is 10A. In this embodiment, 6 withstand voltage 70kV relay circuits can ensure that the high-voltage relay subunit can bear the highest voltage difference of 420kV, thereby achieving the purpose of protecting the dc power supply.

In one embodiment, with continued reference to FIG. 4, a relay switch 113A is included in the relay circuit 113A₁Voltage equalizing circuit 113A₂And a drive circuit 113A₃And a driving power source 113A₄。

Specifically, the drive circuit 113A₃Includes a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), a MOSFET drive circuit and a photodiode D₀. The voltage-sharing circuit comprises a voltage-sharing capacitor C connected in parallel₀And voltage-sharing resistor R₀. Wherein, the voltage-sharing capacitor C₀Has a capacitance value of 1nF, is used for dynamic voltage sharing and voltage sharing resistance R₀Is 10 MOmega for static voltage sharing.

Wherein, the positive and negative poles of the driving power supply are connected to the MOSFET driving circuit for supplying power thereto; the metal-oxide semiconductor field effect transistor driving circuit is connected with a gate pole and an emitting pole of the metal-oxide semiconductor field effect transistor and is used for driving the metal-oxide semiconductor field effect transistor; the photodiode is connected in the metal-oxide-semiconductor field effect transistor driving circuit and used for switching on and off the metal-oxide-semiconductor field effect transistor by using an optical signal; the collector of the metal-oxide-semiconductor field effect transistor is connected with one end of the relay switch and is used for switching on and off the relay; the other end of the relay switch is connected with the positive electrode of the driving power supply; two ends of the voltage-sharing circuit are respectively connected with two ends of the relay switch in parallel, and parallel nodes at two ends of the voltage-sharing circuit and the relay switch are respectively used as an input end and an output end of the relay circuit.

The driving power supply can be a battery, and the driving circuit can continuously work for not less than 5 hours after one-time charging according to the design standard.

In one embodiment, as shown in fig. 5, a circuit diagram of an ultra-low frequency cosine square wave generator is provided, and the dc power supply 111 comprises a positive high voltage power supply HVDC-a and a negative high voltage power supply HVDC-b. The forward high-voltage power supply HVDC-a is used for forward charging of the cable, the highest output direct-current voltage is +180kV, and the maximum output power is 4 kV. The negative high-voltage power supply HVDC-b is used for reversely charging the cable, the highest output direct-current voltage is-180 kV, the maximum output power is 4kV, and the charging current under the peak voltage exceeds 20 mA.

In one embodiment, the positive high-voltage power supply and the negative high-voltage power supply of the dc power supply are further connected to an output voltage control port and a switch enable port. The output voltage control port linearly controls the high-voltage output of 0 kV- +180kV or-180 kV-0 kV through a low-voltage signal of 0V-5V; the switch enabling port controls the switch of the positive and negative high-voltage power supply through the change of high and low levels, and when the positive and negative high-voltage power supply is turned off, all switch-based devices in the device are turned off.

The embodiment can regulate and control the magnitude of the output voltage value of the direct-current power supply through the output voltage control port and the switch enabling port, and meanwhile, the safety of the whole device is guaranteed.

In one embodiment, the axial winding form of the reactor is a bottom-up entanglement form, and the longitudinal voltage of the reactor can be equalized as much as possible unlike the winding form from inside to outside adopted in the conventional method. The parameters of the reactor are withstand voltage of 180kV, inductance value of 6H and resistance value of 90 omega, the weight of the reactor is about 110kg, and the size of a single reactor is about 600mm multiplied by 800 mm.

In one embodiment, the ultralow frequency cosine square wave generating device further comprises a high-voltage relay supporting column for supporting the high-voltage relay switch. Because the whole switch is in a high-voltage state for a long time in the working process of the high-voltage relay switch, the high-voltage relay switch needs to be supported, and the high-voltage relay switch is supported by the high-voltage relay switch for a distance of about 1.5 meters, so that ground breakdown and surface flashover are prevented.

In one embodiment, a driving method of an ultra-low frequency cosine square wave generator is provided for driving the ultra-low frequency cosine square wave generator, and referring to fig. 6, the driving method includes steps S100 to S300.

And step S100, outputting positive high voltage and negative high voltage in a time-sharing manner.

The whole output voltage process in one period comprises four stages. The first stage is a forward high-voltage stage 0-t outputting a certain time length₁(ii) a The second stage is a stage t in which no positive high voltage is output and no negative high voltage is output₁～t₂(ii) a The third stage is a negative high-voltage stage t outputting a certain time length₂～t₃(ii) a The fourth stage is a stage t in which no positive high voltage is output and no negative high voltage is output₃～t₄。

Specifically, the four phases within a cycle are equal in duration, all 5 s.

And step S200, when the positive high voltage and the negative high voltage are not output, the level state of the control node of the ultralow frequency cosine square wave generating device is reversed, so that the reversing of the positive high voltage or the negative high voltage on the cable is completed.

Wherein, in the first stage, 0 to t₁The output forward high voltage is used to charge the cable forward, and in a second phase t₁～t₂When the cable is controlled to discharge, the positive high voltage on the cable is reversed to negative high voltage, and the expression form of the cable is that the level state of a control node in the ultralow frequency cosine square wave generating device is reversed, and the high level is reversed to the low level; in a similar manner, in the third stage t₂～t₃The negative high voltage of the output is used to charge the cable in the reverse direction, and in the fourth phase t₃～t₄During the process, the discharge of the control cable is controlled, the negative high voltage on the cable is reversed to positive high voltage, and the reverse high voltage is expressed in the form that the level state of a control node in the ultralow frequency cosine square wave generating device is reversed and is reversed from low level to high levelA level.

And step S300, generating an ultralow-frequency cosine square wave signal on the cable according to the received positive high voltage and negative high voltage.

The cable generates a periodic ultralow-frequency cosine square wave signal through forward charging, reverse reversing, reverse charging and forward reversing of the cable.

In this embodiment, the operations from the first stage to the fourth stage can be continuously performed on the ultra-low frequency cosine square wave generator in a circulating manner to generate cosine square waves with a plurality of periods. Because the maintaining time of each stage is 5s, the whole cosine square wave is in an ultralow frequency state, and the time of the commutation process of the second stage is longer than that of the conventional technology, so that the partial discharge detection of the cable, namely the cable, is facilitated.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.