CN110672995B - Power cable oscillatory wave partial discharge detection circuit and detection method thereof - Google Patents
Power cable oscillatory wave partial discharge detection circuit and detection method thereof Download PDFInfo
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
- G01R31/1263—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation
- G01R31/1272—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials of solid or fluid materials, e.g. insulation films, bulk material; of semiconductors or LV electronic components or parts; of cable, line or wire insulation of cable, line or wire insulation, e.g. using partial discharge measurements
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Abstract
The invention provides a power cable oscillatory wave partial discharge detection circuit and a detection method thereof, wherein the detection circuit comprises a pulse generation circuit, a pulse transformer, a plurality of IGBT trigger circuits, IGBTs, a voltage equalizing circuit, a detection circuit and a cable to be detected, wherein the output end of the pulse generation circuit is electrically connected with the primary side of the pulse transformer, the secondary side of the pulse transformer is respectively electrically connected with the input end of each IGBT trigger circuit, the output end of the IGBT trigger circuit is electrically connected with the gate electrode of each IGBT, and the voltage equalizing circuit is connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrode and the source electrode of the adjacent IGBT 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 pulse generating circuit generates a pulse signal to drive the pulse transformer to transfer energy, and the IGBT applies test voltage to the cable to be tested; measurement circuit measurement after IGBT (insulated Gate Bipolar transistor) turn-off and a signal of the cable to be tested for discharging.
Description
Technical Field
The invention relates to the field of power equipment, in particular to a power cable oscillatory wave partial discharge detection circuit and a detection method thereof.
Background
The power industry is the basic industry, and faults of power cables can bring huge losses to power enterprises and power consumers. Along with the continuous reformation of urban power grids in China, XLPE power cables are widely used due to high corrosion resistance and strength. However, after a period of operation, operation faults are easy to occur, and the main reasons are that the cable body is subject to insulation dendritic ageing breakdown and accessories enter moisture to generate discharge.
The local discharge source inside the power cable insulation system can be seen as a point pulse signal source, and electromagnetic waves are generated by the discharge, and propagate along the cable and can be detected. In general, nondestructive detection of a power cable adopts direct-current excitation oscillating wave voltage withstand voltage test (OWTS), a cable to be detected is charged through a series inductor and reaches preset voltage, and then a switch is quickly turned on to perform alternating-current discharge, so that the cable to be detected and the inductor are subjected to series resonance, and a partial discharge signal at a cable defect is excited, so that detection is performed, and damage to the cable by a traditional detection method can be avoided. However, the conventional switch is not suitable for the high-speed operation requirement of the oscillating switch, and the IGBT (insulated gate bipolar transistor) becomes a preferred device of the high-voltage switch because of the advantages of high turn-on speed, small driving power and the like.
Disclosure of Invention
In view of the above, the invention provides a power cable oscillatory wave partial discharge detection circuit with balanced series voltage and consistent trigger signal of a multi-stage IGBT and a detection method thereof.
The technical scheme of the invention is realized as follows:
On one hand, the invention provides a power cable oscillatory wave partial discharge detection circuit, which comprises a pulse generation circuit (1), a pulse transformer (2), a plurality of IGBT trigger circuits (3), an IGBT, a voltage-equalizing circuit (4), a detection circuit (5) and a cable (6) to be detected, wherein the output end of the pulse generation 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 circuits (3) is electrically connected with the gate electrode of the IGBT, and the voltage-equalizing circuit (4) is connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrode and the source electrode of the adjacent IGBT 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 pulse generating circuit (1) outputs a pulse signal with an adjustable duty ratio, and the pulse signal is boosted by the pulse transformer (2) and then is 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 the gate electrode of the IGBT, maintains the on-state of the IGBT or turns off 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 voltage change rate of the IGBTs and synchronizes the driving signals of the IGBTs;
After the IGBT is turned off, the detection circuit (5) and the cable (6) to be detected and the detection circuit (5) are in series resonance, and the detection circuit (5) detects a discharge signal of the cable (6) to be detected.
On the basis of the above technical scheme, preferably, 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, a pulse signal output by the pulse high-voltage power supply is input into the gate electrode of the first triode Q1, the collector electrode of the first triode Q1 is electrically connected with the base electrode of the second triode Q2, the collector electrode of the second triode Q2 is electrically connected with the gate electrode of the third triode Q3, and the emitter electrode and the collector electrode of the third triode Q3 are electrically connected with the primary side of the pulse transformer (2) respectively.
Further preferably, 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 electrode 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 end of the first operational amplifier U1 is electrically connected with +2V excitation voltage, and the non-inverting input end of the first operational amplifier U1 is electrically connected with +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 with the inverting input end of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected with the first input end of the NAND gate, the second input end of the NAND gate is grounded, and the output end of the NAND gate is electrically connected with the CP port of the D trigger and the first input end of the AND gate respectively.
On the basis of the technical scheme, preferably, the IGBT trigger circuit (3) comprises a rectifier bridge and an RC parallel discharge unit, wherein 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 sources and drains of adjacent IGBTs are connected in series with each other.
Further preferably, the RC parallel discharging unit includes a capacitor C5, a resistor R15 and a resistor R16, where 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; the 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 equalizing circuit (4) comprises a voltage stabilizing diode D1, a resistor R17, a resistor R18 and a capacitor C6, wherein the resistor R17 is connected between the source electrode and the drain electrode of the IGBT respectively, 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 reversely connected between the first output end and the second output end of the rectifier bridge in parallel, the gate electrode of the IGBT is also connected with the cathode of the voltage stabilizing diode D1 in parallel, and the source electrode of the IGBT is connected with the anode of the voltage stabilizing diode D1 in parallel.
On the basis of the above technical scheme, 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 with the drain electrode of the head-end IGBT 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 (6) to be detected are all electrically connected with the other end of the inductor L1, and the high-voltage divider is electrically connected with the source electrode of the tail-end IGBT 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 (6) to be tested is grounded.
Further preferably, 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 connected in parallel to the drain electrode of the head end IGBT and the source electrode 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.
On the other hand, the invention also provides a detection method of the power cable oscillatory wave partial discharge detection circuit, which comprises the following steps:
s1: separating two ends of a cable (6) to be tested from a power grid, and arranging a power cable oscillating wave partial discharge detection circuit, a partial discharge positioning instrument and an industrial personal computer on a detection site;
S2: pulse signals are sent out by a pulse high-voltage power supply, the pulse signals are subjected to signal conditioning by a pulse generating circuit (1), the pulse signals are 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 the 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, the new pulse signal is input into a third triode Q3, and after the new pulse signal is amplified by the third triode Q3, a high-frequency square wave signal is formed at 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 the RC parallel discharge unit stores energy; triggering the gate electrode of the IGBT by the shaped square wave signal, and after the square wave signal disappears, discharging by the RC parallel discharging unit to maintain continuous conduction and delay turn-off of the IGBT; a voltage stabilizing diode D1 in the voltage equalizing circuit (4) limits gate trigger voltage so that each IGBT is triggered synchronously; the resistor R17 realizes a voltage equalizing function, so that the voltage between the source electrode and the drain electrode of the IGBT changes steadily to realize dynamic voltage equalizing; detecting under the no-load condition, and measuring a background signal;
S5: the method comprises the steps of connecting a cable (6) to be tested, charging the cable (6) to be tested after the voltage is divided by an inductor L1 and a high-voltage divider when each IGBT connected in series is conducted, discharging the cable (6) to be tested outwards when the charging is finished and the IGBT is turned off, coupling a partial discharge of the cable (6) to be tested to the capacitor by a coupling capacitor C8, forming a detection loop with a resistor R21, forming a pulse current in the loop, leading out the pulse current from a measuring point between the capacitor C8 and the resistor R21, and connecting the measuring point with a partial discharge positioning instrument and an industrial personal computer for measuring;
S6: and after the measurement result is obtained, recovering the normal connection between the cable (6) to be measured and the power grid.
Compared with the prior art, the power cable oscillatory wave partial discharge detection circuit and the detection method thereof have the following beneficial effects:
(1) The pulse generating circuit generates a pulse signal to drive the pulse transformer to transfer energy, and intermittently triggers and turns off the IGBT so that the IGBT applies a test voltage to the cable to be tested; the measuring circuit measures the signal of the cable discharge to be measured after the IGBT is turned off, so that the detection of the partial discharge of the cable to be measured is realized;
(2) The pulse generating circuit sends out an adjustable pulse signal; the frequency of the pulse signal can be changed under the assistance of the D trigger and the PMW signal generating circuit, so that the oscillation process is better realized;
(3) The IGBT trigger circuit provides gate trigger voltage of the IGBT on one hand, stores energy on the other hand, and prolongs the starting time of the IGBT trigger circuit;
(4) The voltage equalizing circuit can limit the gate voltage of the IGBT, prevent the IGBT from being improperly started, and also can equalize the voltage between the source electrode and the drain electrode of each level of the IGBT which are connected in series, so as to prevent the IGBT from being damaged by overvoltage;
(5) The detection circuit detects an instantaneous pulse signal generated when the cable to be tested is partially discharged so as to carry out further analysis.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a block diagram of a system structure of a power cable oscillatory wave partial discharge detection circuit and a detection method thereof according to the present invention;
FIG. 2 is a wiring diagram of a pulse generation circuit of a power cable oscillatory wave partial discharge detection circuit and a detection method thereof according to the present invention;
FIG. 3 is a wiring diagram of a PMW signal generating circuit in a pulse generating circuit of a power cable oscillatory wave partial discharge detection circuit and a detection method thereof according to the present invention;
FIG. 4 is a wiring diagram of an IGBT trigger circuit, an IGBT and a voltage equalizing circuit of the power cable oscillation wave partial discharge detection circuit and the detection method thereof;
fig. 5 is a wiring diagram of a power cable oscillatory wave partial discharge detection circuit and a detection circuit of the detection method thereof according to the present invention.
Detailed Description
The following description of the embodiments of the present invention will clearly and fully describe the technical aspects of the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
As shown in fig. 1, the invention provides a power cable oscillatory wave partial discharge detection circuit, which comprises a pulse generation circuit 1, a pulse transformer 2, a plurality of IGBT trigger circuits 3, an IGBT, a voltage equalizing circuit 4, a detection circuit 5 and a cable 6 to be detected, wherein the output end of the pulse generation 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 electrode of the IGBT, and the voltage equalizing circuit 4 is connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrode and the source electrode of the adjacent IGBT 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 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 is 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 the gate electrode of the IGBT, maintains the on state of the IGBT or turns off the IGBT, and performs direct current charging on the cable 6 to be tested by each IGBT in the on state;
the voltage equalizing circuit 4 reduces the gate voltage change rate of the IGBTs and synchronizes the driving signals of the IGBTs;
after the IGBT is turned off, the detection circuit 5 generates series resonance between the cable under test 6 and the detection circuit 5, and the detection circuit 5 detects a discharge signal of the cable under test 6.
The pulse generating circuit 1 of the invention is used as an excitation source of signals to send out pulse signals, and the capability of the signals is amplified and output to each IGBT trigger circuit 3 through the pulse transformer 2, so that the IGBT is continuously turned on and off. The pulse signal emitted by the pulse generating circuit 1 can be realized by a pulse high-voltage power supply product which is common in the market.
As shown in fig. 2, the pulse generating circuit 1 of the present invention includes 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 to 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 the pulse transformer 2. The first triode Q1 and the second triode Q2 can condition pulse signals sent by a pulse high-voltage power supply, and then the pulse signals are 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 2, 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 electrode of the third triode Q3. The PMW signal generating circuit sends out high-frequency square wave signals which are respectively input into the D trigger and the AND gate, so that the 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 respectively electrically connected with one end of a resistor R2, one end of a resistor R3 and the base electrode of a first triode Q1; the emitter 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 the resistor R4 after being connected with the collector of the first triode Q1 in parallel; the other end of the resistor R4 is electrically connected with the base electrode of the second triode Q2; the emitter of the second triode Q2 is electrically connected with a +12V power supply, and the collector of the second triode Q2 is electrically connected with one end of a resistor R5 and a D port of a 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 respectively and electrically connected with the CP port of the D trigger and the first input end of the AND gate; 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 electrode of a third triode Q3; the collector and 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 triode Q3 is also electrically connected with a +12V power supply through a resistor R7.
As shown in fig. 3, the PMW signal generation 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 end of the first operational amplifier U1 is electrically connected with +2V excitation voltage, and the non-inverting input end of the first operational amplifier U1 is electrically connected with +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 with the inverting input end of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected with the first input end of the NAND gate, the second input end of the NAND gate is grounded, and the output end of the NAND gate is electrically connected with the CP port of the D trigger and the first input end of the AND gate respectively.
The non-inverting input end of the first operational amplifier U1 is provided with a filter circuit formed by parallel connection of a resistor R9 and a capacitor C2, and the non-inverting input end of the first operational amplifier U1 is electrically connected with a +3.3V power supply through a capacitor R8; the inverting input end of the first operational amplifier U1 is respectively and electrically connected with one end of the resistor R10, one end of the capacitor C3 and one end of the resistor R11; the other end of the resistor R10 is electrically connected with a +2V power supply; the other end of the capacitor C3 is electrically connected with the output end of the first operational amplifier U1; the other end of the resistor R11 is electrically connected with the output end of the second operational amplifier U2; 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 first operational amplifier U1 and its peripheral components together form an error amplifier, with +2V power being used as the excitation signal input by the first operational amplifier U1, and +3.3V power being used as the reference voltage input by the first operational amplifier U1. The non-inverting input end of the third operational amplifier U3 is electrically connected with a +3.3V power supply; the inverting input end of the third operational amplifier U3 is respectively and electrically connected with one end of a resistor R12 and one end of a capacitor C4, and the other end of the resistor R12 is respectively and electrically connected with the output end of the fourth operational amplifier U4 and one end of a resistor R13; the non-inverting input end of the fourth operational amplifier U4 is electrically connected with a +3.3V power supply; the inverting input end of the fourth operational amplifier U4 is electrically connected with the other end of the resistor R13, and a resistor R14 is also connected in parallel between the output end of the third operational amplifier U3 and the inverting input end of the fourth operational amplifier U4. The output end of the third operational amplifier U3 is electrically connected with the inverting input end of the second operational amplifier U2. The output end of the second operational amplifier U2 is electrically connected with the first input end of the NAND gate, and the second input end of the NAND gate is grounded. The third operational amplifier U3 and the fourth operational amplifier U4 form a triangular wave generator, the second operational amplifier U2 outputs square wave signals with adjustable duty ratio, and the adjustment of the duty ratio is controlled by the input of the inverting input end of the first operational amplifier U1. In the invention, the first operational amplifier U1 and the third operational amplifier U3 are OPA2365, which are single power operational amplifiers and use +5V single power. The first operational amplifier U1 and the third operational amplifier U3 may be integrated in one chip, and the size of the chip may be reduced. The second operational amplifier U2 and the third operational amplifier U3 can be selected from TLV3502 comparators, and are powered by a +5V single power supply, and the second operational amplifier U2 and the third operational amplifier U3 can be integrated in the same TLV3502, so that the size of a chip is further reduced.
As shown in fig. 4, the IGBT triggering circuit 3 includes a rectifier bridge and an RC parallel discharge unit, where a first input end and a second input end of the rectifier bridge are respectively electrically connected with the secondary side of the pulse transformer 2, 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 sources and drains 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 discharging unit and IGBT. The elements of each IGBT trigger circuit 3 are preferably identical products of the same manufacturer and the same batch, and the performance of the same products is relatively close.
The RC parallel discharging unit comprises a capacitor C5, a resistor R15 and a resistor R16, wherein two ends of the capacitor C5 and the resistor R16 are respectively connected in parallel between a first output end and a second output end of the rectifier bridge; the 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 discharging unit can continue discharging after the pulse transformer 2 is powered off, and the conduction of the IGBT is maintained. Because the gate of the IGBT needs a certain energy source when being started, but the energy source needed for keeping the IGBT on is smaller, a discharge loop can be formed by RC parallel discharge units, and continuous on of the IGBT 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, where the resistor R17 is connected between the source and the drain of the IGBT respectively, 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 reversely connected between the first output end and the second output end of the rectifier bridge in parallel, the gate electrode of the IGBT is also connected with the cathode of the voltage stabilizing diode D1 in parallel, and the source electrode of the IGBT is connected with the anode of the voltage stabilizing diode D1 in parallel. The voltage equalizing circuit 4 can buffer the change of the circuit voltage, thereby achieving the effect of voltage equalizing 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 resistor R21, wherein one end of the inductor L1 is electrically connected with the drain electrode of the head end 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 tested are all electrically connected with the other end of the inductor L1, and the high voltage divider is electrically connected with the source electrode of the tail end IGBT connected in series; 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 6 to be tested 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 connected to the drain electrode of the head IGBT and the source electrode of the tail IGBT which are connected in series, and the capacitor C7 is connected to the two ends of the resistor R20 in parallel.
The invention discloses a detection method for a power cable oscillatory wave partial discharge detection circuit, which comprises the following steps:
s1: separating two ends of a cable 6 to be tested from a power grid, and arranging a power cable oscillating wave partial discharge detection circuit, a partial discharge positioning instrument and an industrial personal computer on a detection site;
S2: pulse signals are sent out by a pulse high-voltage power supply, the pulse generating circuit 1 carries out signal conditioning on the pulse signals, the pulse signals are 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 the 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, the new pulse signal is input into a third triode Q3, and after the new pulse signal is amplified by the third triode Q3, a high-frequency square wave signal is formed on the primary side of the 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 the RC parallel discharge unit stores energy; triggering the gate electrode of the IGBT by the shaped square wave signal, and after the square wave signal disappears, discharging by the RC parallel discharging unit to maintain continuous conduction and delay turn-off of the IGBT; the voltage stabilizing diode D1 in the voltage equalizing circuit 4 limits the gate trigger voltage so that each IGBT is triggered synchronously; the resistor R17 realizes a voltage equalizing function, so that the voltage between the source electrode and the drain electrode of the IGBT changes steadily to realize dynamic voltage equalizing; detecting under the no-load condition, and measuring a background signal;
S5: the method comprises the steps of accessing a cable 6 to be tested, charging the cable 6 to be tested after the voltage is divided by an inductor L1 and a high-voltage divider when each IGBT connected in series is conducted, discharging the cable 6 to be tested outwards when the charging is finished and the IGBT is turned off, coupling a 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 out the pulse current from a measuring point between the capacitor C8 and the resistor R21, and connecting the measuring point with a partial discharge positioning instrument and an industrial personal computer for measuring;
s6: after the measurement result is obtained, the normal connection between the cable 6 to be measured and the power grid is restored.
In the above detection method, the local discharge locator may be a 560 type local discharge locator of the company HAEFELY in swiss. The industrial personal computer can adopt a PC. When partial discharge occurs, a partial discharge pulse signal propagates along the cable 6 to be tested from two opposite directions by the partial discharge positioner according to an off-line method of a time domain reflection method commonly used in the art, and a time difference exists when the two pulses reach a test end of the partial discharge positioner.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (5)
1. The utility model provides a power cable oscillatory wave partial discharge detection circuit which 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 equalizing circuit (4), a detection circuit (5) and a cable (6) to be tested, 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 each IGBT trigger circuit (3) is electrically connected with the gate electrode of each IGBT, and the voltage equalizing circuit (4) is connected in parallel between the drain electrode and the source electrode of each IGBT; the drain electrode and the source electrode of the adjacent IGBT 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 pulse generating circuit (1) outputs a pulse signal with an adjustable duty ratio, and the pulse signal is boosted by the pulse transformer (2) and then is 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 the gate electrode of the IGBT, maintains the on-state of the IGBT or turns off 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 voltage change rate of the IGBTs and synchronizes the driving signals of the IGBTs;
After the IGBT is turned off, the detection circuit (5) and the cable (6) to be detected and the detection circuit (5) are in series resonance, and the detection circuit (5) detects a discharge signal applied to the cable (6) to be detected;
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, a pulse signal output by the pulse high-voltage power supply is input into the gate electrode of the first triode Q1, the collector electrode of the first triode Q1 is electrically connected with the base electrode of the second triode Q2, the collector electrode of the second triode Q2 is electrically connected with the gate electrode of the third triode Q3, and the emitter electrode and the collector electrode of the third triode Q3 are respectively electrically connected with the primary side of the pulse transformer (2);
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 electrode of the third triode Q3;
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 end of the first operational amplifier U1 is electrically connected with +2V excitation voltage, and the non-inverting input end of the first operational amplifier U1 is electrically connected with +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 with the inverting input end of the second operational amplifier U2; the output end of the second operational amplifier U2 is electrically connected with the first input end of the NAND gate, the second input end of the NAND gate is grounded, and the output end of the NAND gate is electrically connected with the CP port of the D trigger and the first input end of the AND gate respectively;
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 electrode of the head-end IGBT which is mutually 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 with the other end of the inductor L1, and the high-voltage divider is electrically connected with the source electrode of the tail-end IGBT which is mutually connected in series; 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 (6) to be tested 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 connected to the drain electrode of the head IGBT and the source electrode of the tail IGBT which are connected in series, and the capacitor C7 is connected to the two ends of the resistor R20 in parallel.
2. A power cable oscillatory wave partial discharge detection circuit as claimed in claim 1, wherein: the IGBT trigger circuit (3) comprises a rectifier bridge and an RC parallel discharge unit, wherein 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 sources and drains of adjacent IGBTs are connected in series with each other.
3. A power cable oscillatory wave partial discharge detection circuit as claimed in claim 2, wherein: the RC parallel discharging unit comprises a capacitor C5, a resistor R15 and a resistor R16, wherein two ends of the capacitor C5 and the resistor R16 are respectively connected in parallel between a first output end and a second output end of the rectifier bridge; the 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.
4. A power cable oscillatory wave partial discharge detection circuit as claimed in claim 2, wherein: the voltage equalizing circuit (4) comprises a voltage stabilizing diode D1, a resistor R17, a resistor R18 and a capacitor C6, wherein the resistor R17 is connected between the source electrode and the drain electrode of the IGBT respectively, 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 reversely connected between the first output end and the second output end of the rectifier bridge in parallel, the gate electrode of the IGBT is also connected with the cathode of the voltage stabilizing diode D1 in parallel, and the source electrode of the IGBT is connected with the anode of the voltage stabilizing diode D1 in parallel.
5. The detection method of the power cable oscillatory wave partial discharge detection circuit as claimed in claim 4, wherein: the method comprises the following steps:
S1: separating two ends of a cable (6) to be tested from a power grid, and arranging a power cable oscillating wave partial discharge detection circuit, a partial discharge positioning instrument and an industrial personal computer on a detection site;
S2: pulse signals are sent out by a pulse high-voltage power supply, the pulse signals are subjected to signal conditioning by a pulse generating circuit (1), the pulse signals are 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 the 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, the new pulse signal is input into a third triode Q3, and after the new pulse signal is amplified by the third triode Q3, a high-frequency square wave signal is formed at 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 the RC parallel discharge unit stores energy; triggering the gate electrode of the IGBT by the shaped square wave signal, and after the square wave signal disappears, discharging by the RC parallel discharging unit to maintain continuous conduction and delay turn-off of the IGBT; a voltage stabilizing diode D1 in the voltage equalizing circuit (4) limits gate trigger voltage so that each IGBT is triggered synchronously; the resistor R17 realizes a voltage equalizing function, so that the voltage between the source electrode and the drain electrode of the IGBT changes steadily to realize dynamic voltage equalizing; detecting under the no-load condition, and measuring a background signal;
S5: the method comprises the steps of connecting a cable (6) to be tested, charging the cable (6) to be tested after the voltage is divided by an inductor L1 and a high-voltage divider when each IGBT connected in series is conducted, discharging the cable (6) to be tested outwards when the charging is finished and the IGBT is turned off, coupling a partial discharge of the cable (6) to be tested to the capacitor C8 by a coupling capacitor C8, forming a detection loop with a resistor R21, forming a pulse current in the loop, leading out the pulse current from a measuring point between the capacitor C8 and the resistor R21, and connecting the measuring point with a partial discharge positioning instrument and an industrial personal computer for measuring;
s6: and after the measurement result is obtained, recovering the normal connection between the cable (6) to be measured and the power grid.
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| CN114900157B (en) * | 2022-07-12 | 2022-09-20 | 深圳迈微医疗科技有限公司 | Pulse generating circuit, pulse generator and medical equipment |
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