CN211123124U - Power cable oscillatory wave partial discharge detection circuit - Google Patents

Abstract

The utility model provides a power cable oscillatory wave partial discharge detection circuit, including pulse generation circuit, pulse transformer, a plurality of IGBT trigger circuits, IGBT, equalizer circuit, detection circuitry, cable and the local discharge locator of awaiting measuring, pulse generation circuit's output and pulse transformer's once side electric connection, pulse transformer's secondary side respectively with each IGBT trigger circuit's input electric connection, IGBT trigger circuit's output and IGBT's gate pole electric connection, the equalizer circuit that has parallelly connected between each IGBT's drain electrode and the source electrode; the drain electrodes and the source electrodes of the adjacent IGBTs are connected in series; and a detection circuit and a cable to be detected are connected in parallel between the drain electrode of the head end IGBT and the source electrode of the tail end IGBT which are connected in series. The utility model discloses a pulse generation circuit produces pulse signal drive pulse transformer and carries out energy transfer, and IGBT applys test voltage to the cable that awaits measuring; and the measurement circuit measures the discharging signal of the cable to be measured after the IGBT is switched off.

Description

Power cable oscillatory wave partial discharge detection circuit

Technical Field

The utility model relates to a power equipment field especially relates to a power cable oscillatory wave partial discharge detection circuitry.

Background

With the continuous improvement of urban power grids in China, X L PE power cables are widely used due to corrosion resistance and high strength, but after a period of operation, operation faults are easy to occur, and the main reasons are that the insulation tree-shaped insulation branch of the cable body is aged and punctured and accessories are affected by tide to cause discharge.

The source of the partial discharge inside the insulation system of the power cable can be seen as a source of a point pulse signal, and the discharge generates electromagnetic waves which propagate along the cable and can be detected. Generally, a direct current excitation oscillatory wave voltage withstand voltage test (OWTS) is adopted for nondestructive testing of a power cable, the cable to be tested is charged through a series inductor and reaches a preset voltage, then a switch is quickly turned on to carry out alternating current discharge, so that series resonance occurs between the cable to be tested and the inductor, a partial discharge signal at a cable defect is excited, the detection is convenient, and the damage of a traditional detection method to the cable can be avoided. However, a common switch is not suitable for the requirement of high-speed action of an oscillating switch, an IGBT (insulated gate bipolar transistor) becomes a preferred device of a high-voltage switch because of the advantages of high conduction speed, small driving power and the like, the IGBT has limited withstand voltage, the IGBT needs to be used in series under a high-voltage condition, and if trigger signals of the IGBTs are inconsistent, the turn-on and turn-off time of the devices is asynchronous, so that each stage of series-connected IGBTs suffers unbalanced voltage, and the IGBT is easily damaged.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model provides a multistage IGBT series voltage is balanced, each IGBT synchronization trigger's power cable oscillatory wave partial discharge detection circuit.

The technical scheme of the utility model is realized like this: the utility model provides a power cable oscillatory wave partial discharge detection circuit, including pulse generation circuit (1), pulse transformer (2), a plurality of IGBT trigger circuit (3), IGBT, equalizer circuit (4), detection circuitry (5), cable (6) and the local discharge positioning appearance of awaiting measuring, the output of pulse generation circuit (1) and the primary side electric connection of pulse transformer (2), the secondary side of pulse transformer (2) respectively with the input electric connection of each IGBT trigger circuit (3), the output of IGBT trigger circuit (3) and the gate pole electric connection of IGBT, equalizer circuit (4) are connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrodes and the source electrodes of the adjacent IGBTs are connected in series; a detection circuit (5) and a cable (6) to be detected are connected in parallel between the drain electrode of the head end IGBT and the source electrode of the tail end IGBT which are connected in series; the output end of the detection circuit (5) is electrically connected with the input end of the partial discharge locator;

the pulse generating circuit (1) outputs a pulse signal with adjustable duty ratio, and the pulse signal is boosted by the pulse transformer (2) and then input into the IGBT trigger circuit (3) on the secondary side of the pulse transformer (2);

the IGBT trigger circuit (3) receives the boosted pulse signal, inputs the pulse signal into a gate pole of the IGBT, maintains the on or off of the IGBT, and each IGBT in the on state carries out direct current charging on the cable (6) to be tested;

the voltage equalizing circuit (4) reduces the change rate of the grid voltage of the IGBT and enables the driving signals of the IGBTs to be synchronous;

after the IGBT of the detection circuit (5) is turned off, the cable (6) to be detected and the detection circuit (5) generate series resonance, and the detection voltage (5) detects a discharge signal of the cable (6) to be detected.

Based on the above technical solution, preferably, the pulse generating circuit (1) includes a pulse high voltage power supply, a first transistor Q1, a second transistor Q2 and a third transistor Q3, wherein a pulse signal output by the pulse high voltage power supply is input to a gate of the first transistor Q1, a collector of the first transistor Q1 is electrically connected to a base of the second transistor Q2, a collector of the second transistor Q2 is electrically connected to a gate of the third transistor Q3, and an emitter and a collector of the third transistor Q3 are respectively electrically connected to a primary side of the pulse transformer (2).

Further preferably, a D flip-flop, an and gate and a PMW signal generating circuit are arranged between the second triode Q2 and the third triode Q3; the collector of the second triode Q2 is electrically connected with the D port of the D trigger, the input end of the PMW signal generating circuit is respectively electrically connected with the CP port of the D trigger and the first input end of the AND gate, and the output end of the D trigger is electrically connected with the second input end of the AND gate; the output end of the AND gate is electrically connected with the gate of the third triode Q3.

Still further preferably, the PMW signal generating circuit includes a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, and a nand gate; the inverting input terminal of the first operational amplifier U1 is electrically connected to the +2V driving voltage, and the non-inverting input terminal of the first operational amplifier U1 is electrically connected to the +3.3V voltage; the output end of the first operational amplifier U1 is electrically connected with the non-inverting input end of the second operational amplifier U2, the non-inverting input ends of the third operational amplifier U3 and the fourth operational amplifier U4 are electrically connected with +3.3V voltage, and the inverting input end of the fourth operational amplifier U4 is electrically connected with the output end of the third operational amplifier U3 and the output end of the fourth operational amplifier U4 respectively; the output end of the fourth operational amplifier U4 is also electrically connected with the inverting input end of the third operational amplifier U3; the third operational amplifier U3 is electrically connected to the inverting input terminal of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected to the first input end of the nand gate, the second input end of the nand gate is grounded, and the output ends of the nand gate are respectively electrically connected to the CP port of the D flip-flop and the first input end of the and gate.

On the basis of the technical scheme, preferably, the IGBT trigger circuit (3) includes a rectifier bridge and an RC parallel discharge unit, a first input end and a second input end of the rectifier bridge are electrically connected with the secondary side of the pulse transformer (2), respectively, and the RC parallel discharge unit is connected in parallel with a first output end and a second output end of the rectifier bridge; the source and drain of adjacent IGBTs are connected in series with each other.

Further preferably, the RC parallel discharge unit includes a capacitor C5, a resistor R15 and a resistor R16, and two ends of the capacitor C5 and the resistor R16 are respectively connected in parallel between the first output end and the second output end of the rectifier bridge; two ends of the resistor R15 are connected in parallel between the capacitor C5 and the connection point of the resistor R16 and the first output end of the rectifier bridge.

Further preferably, the voltage-sharing circuit (4) comprises a zener diode D1, a resistor R17, a resistor R18 and a capacitor C6, wherein the resistor R17 is connected between the source and the drain of the IGBT, and the resistor R18 and the capacitor C6 are connected in series and then connected in parallel with two ends of the resistor R17; the voltage stabilizing diode D1 is connected in reverse parallel between the first output end and the second output end of the rectifier bridge, the gate of the IGBT is also connected in parallel with the cathode of the voltage stabilizing diode D1, and the source of the IGBT is connected in parallel with the anode of the voltage stabilizing diode D1.

On the basis of the above technical solution, preferably, the detection circuit (5) includes an inductor L1, a high voltage divider, a coupling capacitor C8 and a detection impedance R21, one end of the inductor L1 is electrically connected to the drain of the first-end IGBT connected in series, one end of the high voltage divider, one end of the resistor R21 and one end of the cable to be tested (6) are electrically connected to the other end of the inductor L1, the high voltage divider is electrically connected to the source of the last IGBT connected in series, the coupling capacitor C8 is connected in series with the other end of the resistor R21 and then grounded, and the other end of the cable to be tested (6) is grounded.

Further preferably, the high voltage divider includes a resistor R19, a resistor R20 and a capacitor C7, the resistor R19 and the resistor R20 are connected in series and then connected in parallel to the drain of the head end IGBT and the source of the tail end IGBT which are connected in series, and the capacitor C7 is connected in parallel to both ends of the resistor R20.

Preferably, one end of the coupling capacitor C8 connected in series with the resistor R21 is electrically connected to an input end of the partial discharge locator.

The utility model provides a pair of power cable oscillatory wave partial discharge detection circuitry for prior art, has following beneficial effect:

(1) the utility model discloses a pulse generation circuit produces pulse signal drive pulse transformer and carries out energy transfer, intermittent type trigger and turn off IGBT, make IGBT exert test voltage to the cable that awaits measuring; after the IGBT is switched off, the measuring circuit measures a discharging signal of the cable to be measured, and partial discharging detection of the cable to be measured is achieved;

(2) the pulse generating circuit sends out an adjustable pulse signal; under the assistance of a D trigger and a PMW signal generating circuit, the frequency of the pulse signal can be changed, and the oscillation process is better realized;

(3) the IGBT trigger circuit provides gate trigger voltage of the IGBT on one hand, and stores energy on the other hand to prolong the opening time of the IGBT;

(4) the voltage equalizing circuit can limit the gate voltage of the IGBT, prevent the IGBT from being improperly opened, and can equalize the voltage between the source and the drain of each series IGBT so as to prevent the IGBT from being damaged due to overvoltage;

(5) the detection circuit detects a transient pulse signal generated when the cable to be detected is partially discharged so as to carry out further analysis;

(6) the partial discharge locator can further judge the position of partial discharge according to the transient pulse signal sent by the cable to be tested.

Drawings

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

Fig. 1 is a block diagram of a system structure of a power cable oscillatory wave partial discharge detection circuit according to the present invention;

fig. 2 is a wiring diagram of a pulse generating circuit of the oscillating wave partial discharge detection circuit of the power cable of the present invention;

FIG. 3 is a wiring diagram of a PMW signal generating circuit in the pulse generating circuit of the power cable oscillatory wave partial discharge detection circuit of the present invention;

fig. 4 is a wiring diagram of the IGBT trigger circuit, the IGBT and the voltage equalizing circuit of the power cable oscillatory wave partial discharge detection circuit of the present invention;

fig. 5 is a wiring diagram of the detection circuit of the power cable oscillatory wave partial discharge detection circuit of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work all belong to the protection scope of the present invention.

As shown in fig. 1, the utility model provides a power cable oscillatory wave partial discharge detection circuitry, including pulse generation circuit 1, pulse transformer 2, a plurality of IGBT trigger circuit 3, IGBT, equalizer circuit 4, detection circuitry 5, cable 6 and the local discharge positioning appearance of awaiting measuring, wherein pulse generation circuit 1's output and pulse transformer 2's primary side electric connection, pulse transformer 2's secondary side respectively with each IGBT trigger circuit 3's input electric connection, IGBT trigger circuit 3's output and IGBT's gate pole electric connection, the parallel connection has equalizer circuit 4 between each IGBT's drain electrode and the source electrode; the drain electrodes and the source electrodes of the adjacent IGBTs are connected in series; a detection circuit 5 and a cable 6 to be detected are connected in parallel between the drain electrode of the head end IGBT and the source electrode of the tail end IGBT which are connected in series; the output end of the detection circuit 5 is electrically connected with the input end of the partial discharge locator.

The pulse generating circuit 1 outputs a pulse signal with adjustable duty ratio, and the pulse signal is boosted by the pulse transformer 2 and then input into the IGBT trigger circuit 3 on the secondary side of the pulse transformer 2;

the IGBT trigger circuit 3 receives the boosted pulse signal, inputs the pulse signal into a gate pole of the IGBT, maintains the on or off of the IGBT, and each IGBT in the on state carries out direct current charging on the cable 6 to be tested;

the voltage equalizing circuit 4 reduces the gate pole voltage change rate of the IGBT to synchronize the driving signals of the IGBTs;

after the IGBT of the detection circuit 5 is turned off, the cable 6 to be detected and the detection circuit 5 generate series resonance, and the detection voltage 5 detects a discharge signal of the cable 6 to be detected.

The utility model discloses a pulse generation circuit 1 sends pulse signal as the excitation source of signal, and the ability of this signal is through pulse transformer 2 enlargies output to each IGBT trigger circuit 3 in for IGBT is continuous to switch on and turn-off. The pulse signal generated by the pulse generating circuit 1 can be realized by a pulse high-voltage power supply product commonly available in the market.

As shown in fig. 1, the utility model discloses a pulse generation circuit 1 includes pulse high voltage power supply, first triode Q1, second triode Q2 and third triode Q3, the gate pole of the first triode Q1 of pulse signal input of pulse high voltage power supply output, the collecting electrode of first triode Q1 and second triode Q2's base electric connection, the collecting electrode of second triode Q2 and third triode Q3's gate pole electric connection, the projecting pole and the collecting electrode of third triode Q3 respectively with pulse transformer 2's the once side electric connection. The first triode Q1 and the second triode Q2 can condition the pulse signal sent by the pulse high-voltage power supply, and then the pulse signal is amplified by the third triode Q3 and then input to the primary side of the pulse transformer 2, and the pulse transformer 2 performs boosting output.

As shown in fig. 1 and fig. 2, a D flip-flop, an and gate and a PMW signal generating circuit are disposed between the second transistor Q2 and the third transistor Q3; the collector of the second triode Q2 is electrically connected with the D port of the D trigger, the input end of the PMW signal generating circuit is respectively electrically connected with the CP port of the D trigger and the first input end of the AND gate, and the output end of the D trigger is electrically connected with the second input end of the AND gate; the output end of the AND gate is electrically connected with the gate of the third triode Q3. The PMW signal generating circuit sends out high-frequency square wave signals, the high-frequency square wave signals are respectively input into the D trigger and the AND gate, so that pulse signals output by the pulse high-voltage power supply are further mixed with the high-frequency square wave signals, the PMW signal generating circuit can adjust the duty ratio of the high-frequency square wave signals, and the frequency of the pulse signals can be further changed.

Specifically, the output end of the pulse high-voltage power supply is electrically connected with one end of a resistor R1, and the other end of the resistor R1 is electrically connected with one end of a resistor R2, one end of a resistor R3 and the base of a first triode Q1 respectively; an emitting electrode of the first triode Q1 is connected with the other end of the resistor R3 in parallel and then grounded; the other end of the resistor R2 is electrically connected with one end of a resistor R4 after being connected in parallel with the collector of the first triode Q1; the other end of the resistor R4 is electrically connected with the base of the second triode Q2; an emitter of the second triode Q2 is electrically connected with a +12V power supply, and a collector of the second triode Q2 is electrically connected with one end of the resistor R5 and a D port of the D trigger; the other end of the resistor R5 is grounded; the output end of the D trigger is electrically connected with the second input end of the AND gate; the input end of the PMW signal generating circuit is electrically connected with the CP port of the D trigger and the first input end of the AND gate respectively; the output end of the AND gate is electrically connected with one end of a resistor R6, and the other end of the resistor R6 is electrically connected with the base of a third triode Q3; the collector and the emitter of the third triode Q3 are connected in parallel with the two ends of the capacitor C1 and the primary side of the pulse transformer 2; the collector of the third transistor Q3 is also electrically connected to the +12V power supply through a resistor R7.

As shown in fig. 3, the PMW signal generating circuit includes a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4, and a nand gate; the inverting input terminal of the first operational amplifier U1 is electrically connected to the +2V driving voltage, and the non-inverting input terminal of the first operational amplifier U1 is electrically connected to the +3.3V voltage; the output end of the first operational amplifier U1 is electrically connected with the non-inverting input end of the second operational amplifier U2, the non-inverting input ends of the third operational amplifier U3 and the fourth operational amplifier U4 are electrically connected with +3.3V voltage, and the inverting input end of the fourth operational amplifier U4 is electrically connected with the output end of the third operational amplifier U3 and the output end of the fourth operational amplifier U4 respectively; the output end of the fourth operational amplifier U4 is also electrically connected with the inverting input end of the third operational amplifier U3; the third operational amplifier U3 is electrically connected to the inverting input terminal of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected to the first input end of the nand gate, the second input end of the nand gate is grounded, and the output ends of the nand gate are respectively electrically connected to the CP port of the D flip-flop and the first input end of the and gate.

The operational amplifier circuit comprises a first operational amplifier U1, a non-inverting input terminal of the first operational amplifier U1, a filter circuit formed by a resistor R9 and a capacitor C2 connected in parallel, a non-inverting input terminal of the first operational amplifier U1 is electrically connected with a +3.3V power supply through a capacitor R1, an inverting input terminal of the first operational amplifier U1 is electrically connected with one end of the resistor R1, one end of the capacitor C1 and one end of the resistor R1, the other end of the resistor R1 is electrically connected with a +2V power supply, the other end of the capacitor C1 is electrically connected with an output terminal of the first operational amplifier U1, the other end of the resistor R1 is electrically connected with an output terminal of the second operational amplifier U1, an output terminal of the first operational amplifier U1 is electrically connected with a non-inverting input terminal of the second operational amplifier U1, an error amplifier is formed by a first operational amplifier U1 and a fourth operational amplifier U1, the third operational amplifier U1 is electrically connected with a non-inverting input terminal of a third operational amplifier U1, a fourth operational amplifier U1, a third operational amplifier U1 is electrically connected with a fourth operational amplifier 1, a third operational amplifier 1, a fourth operational amplifier 1, a third operational amplifier is electrically connected with a third operational amplifier 1, a fourth operational amplifier 1, a third operational amplifier 1 is electrically connected with a fourth operational amplifier 1, a third operational amplifier is electrically connected with a fourth operational amplifier 1, a third operational amplifier 363 +3 operational amplifier is electrically connected with a third operational amplifier 1, a third operational amplifier 363 operational amplifier 365, a third operational amplifier 1, a fourth operational amplifier is electrically connected with a third operational amplifier, a fourth operational amplifier 1, a third operational amplifier is electrically connected with a third operational amplifier 1, a third operational amplifier 363 + operational amplifier 1, a third operational amplifier is electrically connected with a third operational amplifier, a third operational amplifier 363 operational amplifier, a third operational amplifier 365 and a fourth operational amplifier 1, a third operational amplifier is electrically connected with a fourth operational amplifier, a fourth operational amplifier 363 input terminal of a third operational amplifier 1, a fourth operational amplifier 1 is electrically connected with a third operational amplifier, a third operational amplifier is electrically connected with a fourth operational amplifier, a third operational amplifier 1, a third operational amplifier, a fourth operational amplifier is electrically connected with.

As shown in fig. 4, the IGBT trigger circuit 3 includes a rectifier bridge and an RC parallel discharge unit, a first input end and a second input end of the rectifier bridge are electrically connected to the secondary side of the pulse transformer 2, respectively, and the RC parallel discharge unit is connected in parallel to a first output end and a second output end of the rectifier bridge; the source and drain of adjacent IGBTs are connected in series with each other. The rectifier bridge can process the boosted pulse signals to obtain pulsating direct-current voltage, and the pulsating direct-current voltage is sent to the subsequent RC parallel discharge unit and the IGBT. The components of each IGBT trigger circuit 3 are preferably the same type products of the same manufacturer and the same batch, and the performances of the components are closer.

The RC parallel discharge unit comprises a capacitor C5, a resistor R15 and a resistor R16, and two ends of the capacitor C5 and two ends of the resistor R16 are respectively connected between a first output end and a second output end of the rectifier bridge in parallel; two ends of the resistor R15 are connected in parallel between the capacitor C5 and the connection point of the resistor R16 and the first output end of the rectifier bridge. The RC parallel discharge unit can continue to discharge after the pulse transformer 2 is powered off, and the IGBT is kept conducted. Because the IGBT gate opening needs certain energy, but the energy needed for maintaining the IGBT conduction is small, a discharge loop can be formed by RC parallel discharge units, and the IGBT continuous conduction is realized until the discharge process is finished.

As shown in fig. 4, the voltage equalizing circuit 4 includes a zener diode D1, a resistor R17, a resistor R18, and a capacitor C6, wherein the resistor R17 is connected between the source and the drain of the IGBT, and the resistor R18 and the capacitor C6 are connected in series and then connected in parallel with two ends of the resistor R17; the voltage stabilizing diode D1 is connected in reverse parallel between the first output end and the second output end of the rectifier bridge, the gate of the IGBT is also connected in parallel with the cathode of the voltage stabilizing diode D1, and the source of the IGBT is connected in parallel with the anode of the voltage stabilizing diode D1. The voltage equalizing circuit 4 can buffer the voltage change of the circuit, thereby achieving the effect of voltage equalization change.

As shown in fig. 5, the detection circuit 5 includes an inductor L1, a high voltage divider, a coupling capacitor C8 and a detection impedance R21, one end of the inductor L1 is electrically connected to the drain of the first IGBT connected in series, one end of the high voltage divider, one end of the resistor R21 and one end of the cable 6 to be detected are electrically connected to the other end of the inductor L1, the high voltage divider is electrically connected to the source of the last IGBT connected in series, the coupling capacitor C8 is connected in series with the other end of the resistor R21 and then grounded, and the other end of the cable 6 to be detected is grounded.

The high-voltage divider comprises a resistor R19, a resistor R20 and a capacitor C7, wherein the resistor R19 and the resistor R20 are connected in series and then are connected in parallel to the drain of the head-end IGBT and the source of the tail-end IGBT which are connected in series, and the capacitor C7 is connected in parallel to two ends of the resistor R20.

Specifically, the utility model discloses to power cable oscillatory wave partial discharge detection circuitry's testing process as follows:

s1: two ends of a cable 6 to be tested are separated from a power grid, and a power cable oscillation wave partial discharge detection circuit, a partial discharge locator, an industrial personal computer and other external equipment are arranged on a detection site;

s2: a pulse high-voltage power supply sends out a pulse signal, a pulse generating circuit 1 carries out signal conditioning on the pulse signal, the pulse signal is input into a second input end of an AND gate through a D port of a D trigger, a PMW square wave signal output by a PMW signal generating circuit is input into a CP port of the D trigger and a first input end of the AND gate, a new pulse signal which is the same as the rising edge of the PMW square wave is generated and input into a third triode Q3, and a third triode Q3 amplifies the new pulse signal and then forms a high-frequency square wave signal on the primary side of a pulse transformer 2;

s3: the pulse transformer 2 forms a high-frequency square wave signal on the primary side and transmits the high-frequency square wave signal to the secondary side;

s4: each IGBT trigger circuit 3 on the secondary side of the pulse transformer 2 shapes the high-frequency square wave signal and stores energy by an RC parallel discharge unit; triggering the gate pole of the IGBT by the shaped square wave signal, and discharging by an RC parallel discharge unit to maintain the continuous conduction of the IGBT and delay the turn-off when the square wave signal disappears; a voltage stabilizing diode D1 in the voltage equalizing circuit 4 limits the gate trigger voltage to ensure that each IGBT is synchronously triggered; the resistor R17 realizes a voltage-sharing function, so that the voltage between the source electrode and the drain electrode of the IGBT can be changed smoothly to realize dynamic voltage sharing; detecting under the condition of no load, and measuring a background signal;

s5, connecting a cable 6 to be tested, charging the cable 6 to be tested after voltage division by an inductor L1 and a high-voltage divider when the series-connected IGBTs are switched on, discharging the cable 6 to be tested outwards when the charging is finished and the IGBTs are switched off, coupling the partial discharge of the cable 6 to be tested to a capacitor by a coupling capacitor C8, forming a detection loop with a resistor R21, forming a pulse current in the loop, leading the pulse current out from a measurement point between the capacitor C8 and the resistor R21, and connecting the measurement point with a partial discharge locator and an industrial personal computer for measurement;

s6: and after the measurement result is obtained, the normal connection between the cable 6 to be measured and the power grid is recovered.

In the detection method, the partial discharge locator can adopt 560 type partial discharge locator of HAEFE L Y company of Switzerland, the industrial personal computer can adopt a PC, when partial discharge occurs, a partial discharge pulse signal is transmitted along the cable 6 to be detected from two opposite directions, time difference exists when two pulses reach a test end of the partial discharge locator, and the position of the partial discharge can be calculated according to the time difference because the material and the length of the cable are basically determined, so that the position of a partial discharge part is determined.

According to an off-line method of a time domain reflection method commonly used in the field, when partial discharge occurs, a partial discharge pulse signal is transmitted along a cable 6 to be tested from two opposite directions, time difference exists when the two pulses reach a testing end of the partial discharge locator, and the position of the partial discharge can be calculated according to the time difference due to the fact that the material and the length of the cable are basically determined, so that the position of a partial discharge part is determined.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A power cable oscillatory wave partial discharge detection circuit is characterized in that: the device comprises a pulse generating circuit (1), a pulse transformer (2), a plurality of IGBT trigger circuits (3), IGBTs, a voltage-sharing circuit (4), a detection circuit (5), a cable (6) to be detected and a local discharge locator, wherein the output end of the pulse generating circuit (1) is electrically connected with the primary side of the pulse transformer (2), the secondary side of the pulse transformer (2) is respectively electrically connected with the input end of each IGBT trigger circuit (3), the output end of the IGBT trigger circuit (3) is electrically connected with the gate pole of the IGBT, and the voltage-sharing circuit (4) is connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrodes and the source electrodes of the adjacent IGBTs are connected in series; a detection circuit (5) and a cable (6) to be detected are connected in parallel between the drain electrode of the head end IGBT and the source electrode of the tail end IGBT which are connected in series; the output end of the detection circuit (5) is electrically connected with the input end of the partial discharge locator.

2. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 1, wherein: the pulse generating circuit (1) comprises a pulse high-voltage power supply, a first triode Q1, a second triode Q2 and a third triode Q3, wherein a pulse signal output by the pulse high-voltage power supply is input into a gate electrode of the first triode Q1, a collector electrode of the first triode Q1 is electrically connected with a base electrode of the second triode Q2, a collector electrode of the second triode Q2 is electrically connected with a gate electrode of the third triode Q3, and an emitter electrode and a collector electrode of the third triode Q3 are respectively electrically connected with a primary side of a pulse transformer (2).

3. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 2, wherein: a D trigger, an AND gate and a PMW signal generating circuit are arranged between the second triode Q2 and the third triode Q3; the collector of the second triode Q2 is electrically connected with the D port of the D trigger, the input end of the PMW signal generating circuit is respectively electrically connected with the CP port of the D trigger and the first input end of the AND gate, and the output end of the D trigger is electrically connected with the second input end of the AND gate; the output end of the AND gate is electrically connected with the gate of the third triode Q3.

4. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 3, wherein: the PMW signal generating circuit comprises a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a fourth operational amplifier U4 and a NAND gate; the inverting input terminal of the first operational amplifier U1 is electrically connected to the +2V driving voltage, and the non-inverting input terminal of the first operational amplifier U1 is electrically connected to the +3.3V voltage; the output end of the first operational amplifier U1 is electrically connected with the non-inverting input end of the second operational amplifier U2, the non-inverting input ends of the third operational amplifier U3 and the fourth operational amplifier U4 are electrically connected with +3.3V voltage, and the inverting input end of the fourth operational amplifier U4 is electrically connected with the output end of the third operational amplifier U3 and the output end of the fourth operational amplifier U4 respectively; the output end of the fourth operational amplifier U4 is also electrically connected with the inverting input end of the third operational amplifier U3; the third operational amplifier U3 is electrically connected to the inverting input terminal of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected to the first input end of the nand gate, the second input end of the nand gate is grounded, and the output ends of the nand gate are respectively electrically connected to the CP port of the D flip-flop and the first input end of the and gate.

5. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 1, wherein: the IGBT trigger circuit (3) comprises a rectifier bridge and an RC parallel discharge unit, a first input end and a second input end of the rectifier bridge are respectively and electrically connected with the secondary side of the pulse transformer (2), and the RC parallel discharge unit is connected with a first output end and a second output end of the rectifier bridge in parallel; the source and drain of adjacent IGBTs are connected in series with each other.

6. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 5, wherein: the RC parallel discharge unit comprises a capacitor C5, a resistor R15 and a resistor R16, and two ends of the capacitor C5 and two ends of the resistor R16 are respectively connected between a first output end and a second output end of the rectifier bridge in parallel; two ends of the resistor R15 are connected in parallel between the capacitor C5 and the connection point of the resistor R16 and the first output end of the rectifier bridge.

7. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 5, wherein: the voltage-sharing circuit (4) comprises a voltage-stabilizing diode D1, a resistor R17, a resistor R18 and a capacitor C6, wherein the resistor R17 is respectively connected between the source and the drain of the IGBT, and the resistor R18 and the capacitor C6 are connected in series and then connected with two ends of the resistor R17 in parallel; the voltage stabilizing diode D1 is connected in reverse parallel between the first output end and the second output end of the rectifier bridge, the gate of the IGBT is also connected in parallel with the cathode of the voltage stabilizing diode D1, and the source of the IGBT is connected in parallel with the anode of the voltage stabilizing diode D1.

8. The power cable oscillatory wave partial discharge detection circuit as claimed in claim 1, wherein the detection circuit (5) comprises an inductor L1, a high voltage divider, a coupling capacitor C8 and a detection impedance R21, one end of the inductor L1 is electrically connected with the drain of the head IGBT which are connected in series with each other, one end of the high voltage divider, one end of the resistor R21 and one end of the cable to be detected (6) are electrically connected with the other end of the inductor L1, the high voltage divider is electrically connected with the source of the tail IGBT which are connected in series with each other, the coupling capacitor C8 is connected with the other end of the resistor R21 in series and then grounded, and the other end of the cable to be detected (6) is grounded.

9. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 8, wherein: the high-voltage divider comprises a resistor R19, a resistor R20 and a capacitor C7, wherein the resistor R19 and the resistor R20 are connected in series and then are connected in parallel to the drain electrode of the head end IGBT and the source electrode of the tail end IGBT which are mutually connected in series, and the capacitor C7 is connected in parallel to two ends of the resistor R20.

10. A power cable oscillatory wave partial discharge detection circuit in accordance with claim 8, wherein: one end of the coupling capacitor C8, which is connected with the resistor R21 in series, is electrically connected with the input end of the partial discharge locator.

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