CN112964968B - Test system and method for long-distance submarine high-voltage cable withstand voltage with high-voltage bushing - Google Patents

Abstract

The invention discloses a test system and method for carrying out long-distance submarine high-voltage cables with high-voltage bushings, including a test equipment unit, an onshore GIS equipment unit and an offshore GIS equipment unit; the onshore GIS equipment unit includes a high-voltage bushing, a land Upper GIS high voltage reactor, the first onshore GIS isolation switch, the second onshore GIS isolation switch, the third onshore GIS isolation switch, the first onshore GIS grounding switch, the second onshore GIS grounding switch , the third onshore GIS grounding switch, the onshore GIS high-voltage reactor, the onshore GIS voltage transformer and the onshore GIS arrester; the offshore GIS equipment unit includes the first offshore GIS isolation switch, the second offshore GIS isolation switch, The third offshore GIS isolation switch, the fourth offshore GIS isolation switch, the first offshore GIS ground switch, the second offshore GIS ground switch, the third offshore GIS ground switch, offshore GIS high voltage reactor, offshore GIS voltage mutual inductance The system and method can shorten the test time and save manpower.

Description

Test system and method for long-distance submarine high-voltage cable withstand voltage with high-voltage bushing

technical field

The invention belongs to the field of high-voltage test of electric power equipment, and relates to a test system and method for a long-distance submarine high-voltage cable with a high-voltage bushing.

Background technique

my country's offshore wind power is becoming a new driving force for the development of global offshore wind power, and the supporting role of offshore wind power in my country's energy transformation will become more and more significant. Submarine cables are an indispensable part of offshore wind power construction. At present, offshore wind power is developing from shallow seas to deep seas, which means that the length of submarine cables will become longer and longer. As a key part of the cable handover test, the research It becomes very meaningful to discuss these long-distance cable withstand voltage test schemes and specific test methods.

At present, submarine high-voltage cables are mainly XLPE insulated composite cables. The voltage-resistant mode needs to be subjected to AC voltage-resistant tests according to the requirements of the "GB50150-2016 Electrical Equipment Handover Test Standard". Because the high-voltage, long-distance XLPE submarine cable has a large capacitance to ground, it has high requirements on the power supply equipment for the withstand voltage test, and the field test is difficult. Usually, the series-parallel resonance test method is used to test the submarine cable. Carry out an AC withstand voltage test.

As the length of the submarine high-voltage cable increases, the line loss will also increase, and the capacitive effect will become more and more obvious. Therefore, high-voltage compensation reactors will be connected in parallel on both sides of the submarine high-voltage cable to reduce the capacitive effect and reduce power frequency overvoltage. , and improve the voltage distribution of long-distance submarine high-voltage cables.

In the past, it was necessary to install a special high-voltage test sleeve in the handover test of the submarine cable. Before the withstand voltage test, the SF6 gas in the GIS spaced air chamber of the submarine cable was recovered, the air chamber was opened, and then the connecting rod between the submarine cable and the GIS bus was connected. Release, after installing the special high-voltage test sleeve, connect the submarine cable joint with the special high-voltage test sleeve, and finally re-inject SF6 gas. After the gas pressure is normal and the micro-water test is qualified, the pressure test is carried out. After the pressure test is completed Then the special high-voltage test casing is removed and the subsea cable GIS spaced air chamber is restored. The special high-voltage test bushing of 110kV voltage level is generally three-phase integrated, while the special high-voltage test bushing of 220kV voltage level is single-phase. The above installation process needs to be repeated three times, and each test requires a lot of time and manpower, and The submarine high-voltage cable needs to open the gas chamber for recovery after it is under pressure, and there are certain hidden dangers in operation and poor safety.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and to provide a test system and method for carrying out long-distance submarine high-voltage cable withstand voltage by high-voltage bushing, which can shorten the test time, save manpower, and at the same time, the safety is relatively high. high.

In order to achieve the above object, the high-voltage bushing of the present invention performs a long-distance submarine high-voltage cable withstand voltage test system including a submarine high-voltage cable, a test equipment unit, a land GIS equipment unit and an offshore GIS equipment unit;

The onshore GIS equipment unit includes high-voltage bushing, onshore GIS high-voltage reactor, the first onshore GIS isolation switch, the second onshore GIS isolation switch, the third onshore GIS isolation switch, and the first onshore GIS grounding Switches, the second onshore GIS ground switch, the third onshore GIS ground switch, onshore GIS high-voltage reactors, onshore GIS voltage transformers and onshore GIS arresters;

The offshore GIS equipment unit includes the first offshore GIS isolation switch, the second offshore GIS isolation switch, the third offshore GIS isolation switch, the fourth offshore GIS isolation switch, the first offshore GIS grounding switch, and the second offshore GIS grounding switch Knife switch, the third offshore GIS grounding switch, offshore GIS high-voltage reactor, offshore GIS voltage transformer and offshore GIS lightning arrester;

The test equipment unit is connected to one end of the onshore GIS high-voltage reactor, one end of the first onshore GIS isolation switch, and one end of the first onshore GIS grounding switch via the high-voltage bushing, and is grounded; the first onshore GIS isolation switch The other end of the gate is connected to one end of the third onshore GIS isolation gate, one end of the second onshore GIS isolation gate, one end of the third onshore GIS grounding gate, one end of the fourth onshore GIS isolation gate and the seabed One end of the high-voltage cable is connected;

The other end of the fourth onshore GIS isolation switch is grounded after the onshore GIS voltage transformer, the other end of the second onshore GIS isolation switch is grounded after the second onshore GIS grounding switch, and the onshore GIS high-voltage reactor The other end of the first onshore GIS grounding switch and the other end of the third onshore GIS grounding switch are all grounded, and the other end of the third onshore GIS isolation switch is grounded after the onshore GIS arrester;

The other end of the submarine high-voltage cable is connected to one end of the third offshore GIS isolation switch, one end of the fourth offshore GIS isolation switch, one end of the first offshore GIS isolation switch, one end of the second offshore GIS isolation switch and the third offshore GIS isolation switch One end of the GIS grounding switch is connected, the other end of the fourth offshore GIS isolation switch is grounded after passing through the marine GIS arrester, the other end of the second offshore GIS isolation switch is grounded after passing through the second offshore GIS grounding switch, and the third offshore GIS grounding switch is grounded. The other end of the GIS isolation switch is grounded after passing through the offshore GIS voltage transformer. The other end of the first offshore GIS isolation switch is divided into two paths, one of which is grounded after the first offshore GIS grounding switch, and the other is grounded through the offshore GIS high voltage Ground after the reactor.

The test equipment unit includes a frequency converter, a test transformer, a resonance reactor and a voltage divider, wherein the frequency converter is connected to the high-voltage bushing after the test transformer, the resonance reactor and the voltage divider.

It also includes an onshore GIS live display, wherein the onshore GIS live display is connected to the connection node of the third onshore GIS isolation switch and the fourth onshore GIS isolation switch.

It also includes an offshore GIS live display, wherein the offshore GIS live display is connected to the connection node of the fourth offshore GIS isolation switch and the third offshore GIS isolation switch.

A test method for long-distance submarine high-voltage cables with high-voltage bushings includes the following steps:

1) Connect and lay the equipment;

2) Carry out the nuclear phase and insulation test of the submarine high-voltage cable, and record the insulation resistance value of each phase of the submarine high-voltage cable;

3) Disconnect the connection between the high-voltage side of the resonant reactor and the high-voltage bushing, and ground the high-voltage side of the resonant reactor;

4) Close the first onshore GIS isolation switch, disconnect the second onshore GIS isolation switch, the third onshore GIS isolation switch and the fourth onshore GIS isolation switch; disconnect the third onshore GIS grounding switch gate, short-circuit the onshore GIS live display;

5) Close the first offshore GIS grounding switch and the second offshore GIS grounding switch, disconnect the first offshore GIS isolation switch, the second offshore GIS isolation switch, the third offshore GIS isolation switch and the fourth offshore GIS isolation switch Knife switch; disconnect the third offshore GIS grounding switch, and short-circuit the offshore GIS live display;

6) Calculate the ground capacitance of the submarine high-voltage cable according to the cable parameters and length of the submarine high-voltage cable, select a resonant reactor, connect the frequency converter, the test transformer and the resonant reactor in combination, and connect the high-voltage test wire to phase A of the high-voltage bushing , the phase B of the high-voltage bushing and the phase C of the high-voltage bushing are grounded;

7) After boosting the inverter to the initial voltage, keep the voltage unchanged, adjust the frequency to find the resonant frequency and continue to boost, stop boosting when it reaches 1.7U, and keep it for another 60min. When no discharge occurs, slowly reduce the voltage , disconnect the power supply of the inverter after the voltage drops to zero;

8) Fully discharge the A-phase of the submarine high-voltage cable, measure the insulation resistance value of the A-phase in the submarine high-voltage cable, and compare the current measured insulation resistance value of the A-phase in the submarine high-voltage cable with the submarine high-voltage obtained in step 2). The insulation resistance value of phase A in the cable is compared. When the difference between the insulation resistance value of phase A in the submarine high-voltage cable obtained by the current measurement and the insulation resistance value of phase A in the submarine high-voltage cable obtained in step 2) is in the preset value. When it is within the set range, it means that the A-phase withstand voltage in the submarine high-voltage cable is qualified; then go to step 9), otherwise, it means that the A-phase in the submarine high-voltage cable has a withstand voltage fault;

9) Repeat step 7) and step 8) for phase B in the submarine high-voltage cable and phase C in the submarine high-voltage cable, and complete the high-voltage bushing 6 to carry out the long-distance submarine high-voltage cable withstand voltage test.

The specific operations of step 1) are:

The onshore GIS equipment unit and the offshore GIS equipment unit are installed, SF6 gas is injected to normal pressure, the micro-water monitoring is qualified, and the submarine high-voltage cable is laid and connected.

The present invention has the following beneficial effects:

The test system and method for the long-distance submarine high-voltage cable withstand voltage test system and method for the high-voltage bushing of the present invention use the high-voltage bushing connected with the onshore GIS and the resonant reactor to replace the proprietary test bushing for the high-voltage submarine cable. The withstand voltage test of long-distance submarine high-voltage cables can be completed only by operating part of the isolation switch and grounding switch, which can greatly reduce the test preparation time and avoid the removal of the proprietary high-voltage test casing after the test. It will save time for offshore wind farms to receive electricity, save manpower, and have high safety.

Description of drawings

Fig. 1 is the structural representation of the present invention;

Figure 2 is a flow chart of the present invention.

Among them, 1 is a frequency converter, 2 is a test transformer, 3 is a resonant reactor, 4 is a voltage divider, 5 is an onshore GIS high-voltage reactor, 6 is a high-voltage bushing, 7 is an onshore GIS live display, and 8 is an onshore GIS live display. The upper GIS arrester, 9 is the onshore GIS voltage transformer, 10 is the offshore GIS live display, 11 is the offshore GIS arrester, 12 is the offshore GIS voltage transformer, 13 is the offshore GIS high-voltage reactor, and 14 is the submarine high-voltage cable.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

With reference to Fig. 1, the test system that the high-voltage bushing of the present invention carries out long-distance submarine high-voltage cable withstand voltage includes submarine high-voltage cable 14, test equipment unit, onshore GIS equipment unit and offshore GIS equipment unit; Onshore GIS equipment unit includes High-voltage bushing 6, onshore GIS high-voltage reactor 5, first onshore GIS isolation switch G1, second onshore GIS isolation switch G2, third onshore GIS isolation switch G3, first onshore GIS grounding switch Gate G11, the second onshore GIS grounding switch G21, the third onshore GIS grounding switch G22, the onshore GIS high-voltage reactor 5, the onshore GIS voltage transformer 9 and the onshore GIS arrester 8; the offshore GIS equipment unit includes The first offshore GIS isolation switch G5, the second offshore GIS isolation switch G6, the third offshore GIS isolation switch G7, the fourth offshore GIS isolation switch G8, the first offshore GIS grounding switch G51, the second offshore GIS grounding switch Knife switch G61, third offshore GIS grounding switch G62, offshore GIS high voltage reactor 13, offshore GIS voltage transformer 12 and offshore GIS arrester 11;

The test equipment unit is connected to one end of the onshore GIS high-voltage reactor 5, one end of the first onshore GIS isolation switch G1 and one end of the first onshore GIS grounding switch G11 through the high-voltage bushing 6, and is grounded; The other end of the upper GIS isolation switch G1 is connected to one end of the third onshore GIS isolation switch G3, one end of the second onshore GIS isolation switch G2, one end of the third onshore GIS grounding switch G22, and the fourth onshore GIS isolation switch G22. One end of the GIS isolation knife gate G4 is connected with one end of the submarine high-voltage cable 17;

The other end of the fourth onshore GIS isolation switch G4 is grounded after passing through the onshore GIS voltage transformer 9, and the other end of the second onshore GIS isolation switch G2 is grounded after passing through the second onshore GIS grounding switch G21. The other end of the GIS high-voltage reactor 5, the other end of the first onshore GIS grounding switch G11 and the other end of the third onshore GIS grounding switch G22 are all grounded, and the other end of the third onshore GIS isolation switch G3 is grounded. Ground GIS arrester 8 on land;

The other end of the submarine high-voltage cable 14 is connected to one end of the third offshore GIS isolation switch G7, one end of the fourth offshore GIS isolation switch G8, one end of the first offshore GIS isolation switch G5, and one end of the second offshore GIS isolation switch G6. One end is connected with one end of the third offshore GIS grounding switch G62, the other end of the fourth offshore GIS isolation switch G8 is grounded after passing through the offshore GIS arrester 11, and the other end of the second offshore GIS isolation switch G6 is grounded through the second offshore GIS The grounding switch G61 is grounded, the other end of the third offshore GIS isolation switch G7 is grounded after passing through the offshore GIS voltage transformer 12, and the other end of the first offshore GIS isolation switch G5 is divided into two paths, one of which passes through the first offshore GIS The GIS grounding switch G51 is then grounded, and the other route is grounded after the offshore GIS high-voltage reactor 13.

The test equipment unit includes a frequency converter 1, a test transformer 2, a resonant reactor 3 and a voltage divider 4, wherein the frequency converter 1 is in phase with the high-voltage bushing 6 after the test transformer 2, the resonance reactor 3 and the voltage divider 4. connect.

The present invention also includes the onshore GIS live display 7, wherein the onshore GIS live display 7 is connected to the connection node of the third onshore GIS isolation switch G3 and the fourth onshore GIS isolation switch G4.

The present invention also includes the marine GIS live display 10, wherein the marine GIS live display 10 is connected to the connection node of the fourth offshore GIS isolation switch G8 and the third offshore GIS isolation switch G7.

Referring to Fig. 2, the test method for the long-distance submarine high-voltage cable withstand voltage of the high-voltage bushing of the present invention comprises the following steps:

1) The installation of the onshore GIS equipment unit and the offshore GIS equipment unit is completed, the SF6 gas is injected to the normal pressure, the micro-water monitoring is qualified, and the submarine high-voltage cable 14 is laid and connected;

2) carry out the nuclear phase and insulation test of the submarine high-voltage cable 14, and record the insulation resistance value of each phase of the submarine high-voltage cable 14;

3) Disconnect the connection between the high-voltage side of the resonant reactor 3 and the high-voltage bushing 6, and ground the high-voltage side of the resonant reactor 3;

4) Close the first onshore GIS isolation gate G1, disconnect the second onshore GIS isolation gate G2, the third onshore GIS isolation gate G3 and the fourth onshore GIS isolation gate G4; disconnect the third onshore GIS isolation gate G4; Connect the GIS grounding switch G22, and short-circuit the onshore GIS live display 7;

5) Close the first offshore GIS grounding switch G51 and the second offshore GIS grounding switch G61, disconnect the first offshore GIS isolation switch G5, the second offshore GIS isolation switch G6, the third offshore GIS isolation switch G7 and The fourth offshore GIS isolation switch G8; disconnect the third offshore GIS grounding switch G62, and short-circuit the offshore GIS live display 10;

6) Calculate the ground capacitance of the submarine high-voltage cable 14 according to the cable parameters and length of the submarine high-voltage cable 14, select the resonant reactor 3, connect the frequency converter 1, the test transformer 2 and the resonant reactor 3 in combination, and connect the high-voltage test to the Phase A of the high-voltage bushing 6, phase B of the high-voltage bushing 6 and phase C of the high-voltage bushing 6 are grounded;

7) After boosting the inverter 1 to the initial voltage, keep the voltage unchanged, adjust the frequency to find the resonant frequency and continue to boost, stop boosting when it reaches 1.7U, and keep it for another 60min. When no discharge occurs, it will slowly decrease. After the voltage drops to zero, disconnect the power supply of inverter 1;

8) Fully discharge the A-phase of the submarine high-voltage cable 14, measure the insulation resistance value of the A-phase in the submarine high-voltage cable 14, and obtain the insulation resistance value of the A-phase in the submarine high-voltage cable 14 currently measured and obtained in step 2). The insulation resistance value of phase A in the submarine high-voltage cable 14 is compared, and when the insulation resistance value of phase A in the currently measured submarine high-voltage cable 14 and the insulation resistance value of phase A in the submarine high-voltage cable 14 obtained in step 2) are obtained. When the difference between the two is within the preset range, it means that the A-phase withstand voltage in the submarine high-voltage cable 14 is qualified; then go to step 9), otherwise, the A-phase in the submarine high-voltage cable 14 has a withstand voltage fault;

9) Repeat steps 7) and 8) for phase B in the submarine high-voltage cable 14 and phase C in the submarine high-voltage cable 14, and complete the high-voltage bushing 6 to carry out the long-distance submarine high-voltage cable withstand voltage test.

When power generation occurs during the pressurization process, it is necessary to test the insulation resistance of the discharge submarine high-voltage cable 14, and judge whether the submarine high-voltage cable 14 is qualified according to the insulation resistance value. All steps above.

The difference between the present invention and the prior art is that the high-voltage bushing 6 connecting the onshore GIS and the resonant reactor 3 , the first onshore GIS isolation switch G1 and some busbars all need to withstand voltage together with the submarine high-voltage cable 14 . According to the requirements in "DL/T 555 On-site Withstand Voltage and Insulation Test Guidelines for Gas-insulated Enclosed Switchgear", the test voltage value of high-voltage bushing 6 and the first onshore GIS isolation switch G1 and some busbars should be the factory test voltage 80%, which is much higher than the withstand voltage test value of 1.7 times the rated voltage of the submarine high-voltage cable 14. Therefore, the high-voltage bushing 6 connected with the onshore GIS and the resonant reactor 3 is fully equipped with the test conditions to replace the proprietary high-voltage test bushing. .

To sum up, in the present invention, the high-voltage bushing 6 connected with the onshore GIS and the high-voltage reactor can be used to replace the dedicated test bushing, and the test can be completed only by operating the isolation switch and ground switch of the onshore GIS. It is necessary to install a special test casing, which greatly reduces the test preparation time and cost, and can avoid the operation risk of removing the special test casing, which has strong operability.

The above are only preferred embodiments of the present invention and do not limit the present invention. Any simple modifications, changes and equivalent structural changes made to the above embodiments according to the technical essence of the present invention still belong to the technology of the present invention. within the scope of the program.

Claims (6)

1. a high-voltage bushing carries out the test system of long-distance submarine high-voltage cable pressure, it is characterized in that, comprise submarine high-voltage cable (14), test equipment unit, land GIS equipment unit and marine GIS equipment unit; The onshore GIS equipment unit includes a high-voltage bushing (6), an onshore GIS high-voltage reactor (5), a first onshore GIS isolation switch (G1), a second onshore GIS isolation switch (G2), and a third onshore GIS isolation switch (G2). Upper GIS isolation switch (G3), first onshore GIS grounding switch (G11), second onshore GIS grounding switch (G21), third onshore GIS grounding switch (G22), onshore GIS high voltage reactance (5), onshore GIS voltage transformer (9) and onshore GIS arrester (8); The offshore GIS equipment unit includes the first offshore GIS isolation gate (G5), the second offshore GIS isolation gate (G6), the third offshore GIS isolation gate (G7), the fourth offshore GIS isolation gate (G8), and the third offshore GIS isolation gate (G8). One Offshore GIS Grounding Switch (G51), Second Offshore GIS Grounding Switch (G61), Third Offshore GIS Grounding Switch (G62), Offshore GIS High Voltage Reactor (13), Offshore GIS Voltage Transformer (12) and Offshore GIS arrester (11); The test equipment unit passes through the high-voltage bushing (6) and one end of the onshore GIS high-voltage reactor (5), one end of the first onshore GIS isolation switch (G1), and one end of the first onshore GIS grounding switch (G11) The other end of the first onshore GIS isolation switch (G1) is connected to one end of the third onshore GIS isolation switch (G3), one end of the second onshore GIS isolation switch (G2), the third One end of the onshore GIS grounding switch (G22), one end of the fourth onshore GIS isolation switch (G4) and one end of the submarine high-voltage cable (14) are connected; The other end of the fourth onshore GIS isolation switch (G4) is grounded through the onshore GIS voltage transformer (9), and the other end of the second onshore GIS isolation switch (G2) is grounded through the second onshore GIS grounding switch (G21) after grounding, the other end of the onshore GIS high-voltage reactor (5), the other end of the first onshore GIS grounding switch (G11) and the other end of the third onshore GIS grounding switch (G22) are all grounded , the other end of the third onshore GIS isolation knife gate (G3) is grounded after the onshore GIS arrester (8); The other end of the submarine high-voltage cable (14) is connected to one end of the third offshore GIS isolation switch (G7), one end of the fourth offshore GIS isolation switch (G8), one end of the first offshore GIS isolation switch (G5), and one end of the first offshore GIS isolation switch (G5). One end of the second offshore GIS isolation switch (G6) is connected to one end of the third offshore GIS grounding switch (G62), and the other end of the fourth offshore GIS isolation switch (G8) is grounded after the offshore GIS arrester (11). The other end of the second offshore GIS isolation switch (G6) is grounded through the second offshore GIS grounding switch (G61), and the other end of the third offshore GIS isolation switch (G7) is connected to the offshore GIS voltage transformer (12). Grounding, the other end of the first offshore GIS isolation switch (G5) is divided into two paths, one of which is grounded after the first offshore GIS grounding switch (G51), and the other is grounded after the offshore GIS high-voltage reactor (13). 2. high-voltage bushing according to claim 1 carries out the test system of long-distance submarine high-voltage cable withstand voltage, it is characterized in that, described test equipment unit comprises frequency converter (1), test transformer (2), resonant reactor ( 3) and a voltage divider (4), wherein the frequency converter (1) is connected to the high-voltage bushing (6) after the test transformer (2), the resonant reactor (3) and the voltage divider (4). 3. high-voltage bushing according to claim 2 carries out the test system of long-distance submarine high-voltage cable withstand voltage, it is characterized in that, also comprise onshore GIS live display (7), wherein, onshore GIS live display (7) and The third onshore GIS isolation gate (G3) and the connection node of the fourth onshore GIS isolation gate (G4) are connected. 4. the high-voltage bushing according to claim 3 carries out the test system of long-distance submarine high-voltage cable withstand voltage, it is characterized in that, also comprises marine GIS live display (10), wherein, marine GIS live display (10) and the fourth The connection node of the offshore GIS isolation switch (G8) and the third offshore GIS isolation switch (G7) is connected. 5. a high-voltage bushing carries out the test method of long-distance submarine high-voltage cable pressure resistance, it is characterized in that, based on the high-voltage bushing described in claim 4, the test system of long-distance submarine high-voltage cable pressure resistance is carried out, comprises the following steps: 1) Connect and lay the equipment; 2) carry out the nuclear phase and insulation test of the submarine high-voltage cable (14), and record the insulation resistance value of each phase of the submarine high-voltage cable (14); 3) Disconnect the connection between the high-voltage side of the resonant reactor (3) and the high-voltage bushing (6), and ground the high-voltage side of the resonant reactor (3); 4) Close the first onshore GIS isolation switch (G1), disconnect the second onshore GIS isolation switch (G2), the third onshore GIS isolation switch (G3) and the fourth onshore GIS isolation switch ( G4); disconnect the third onshore GIS grounding switch (G22), and short-circuit the onshore GIS live display (7); 5) Close the first offshore GIS grounding switch (G51) and the second offshore GIS grounding switch (G61), disconnect the first offshore GIS isolation switch (G5), the second offshore GIS isolation switch (G6), The third offshore GIS isolation switch (G7) and the fourth offshore GIS isolation switch (G8); disconnect the third offshore GIS grounding switch (G62), and short-circuit the offshore GIS live display (10); 6) Calculate the ground capacitance of the submarine high-voltage cable (14) according to the cable parameters and length of the submarine high-voltage cable (14), select the resonant reactor (3), and connect the frequency converter (1), the test transformer (2) and the resonant reactance. The high voltage test wire is connected to phase A of the high voltage bushing (6), the phase B of the high voltage bushing (6) and the phase C of the high voltage bushing (6) are grounded; 7) After boosting the inverter (1) to the initial voltage, keep the voltage unchanged, adjust the frequency to find the resonant frequency and continue boosting. When it reaches 1.7U, stop boosting and keep it for another 60min. When no discharge occurs, then Slowly reduce the voltage, and disconnect the power supply of the inverter (1) after the voltage drops to zero; 8) Fully discharge the A-phase of the submarine high-voltage cable (14), measure the insulation resistance value of the A-phase in the submarine high-voltage cable (14), and compare the currently measured insulation resistance value of the A-phase in the submarine high-voltage cable (14). Compare with the insulation resistance value of phase A in the submarine high-voltage cable (14) obtained in step 2). When the difference between the insulation resistance values of phase A in the cable (14) is within the preset range, it means that the withstand voltage of phase A in the submarine high-voltage cable (14) is qualified; then go to step 9), otherwise, it means that There is a withstand voltage fault in phase A in the submarine high-voltage cable (14); 9) Repeat steps 7) and 8) for phase B in the submarine high-voltage cable (14) and phase C in the submarine high-voltage cable (14), and complete the high-voltage bushing (6) for the long-distance submarine high-voltage cable withstand voltage test. 6. high-voltage bushing according to claim 5 carries out the test method of long-distance submarine high-voltage cable withstand voltage, it is characterized in that, the concrete operation of step 1) is: The installation of the onshore GIS equipment unit and the offshore GIS equipment unit is completed, the SF6 gas is injected to the normal pressure, the micro-water monitoring is qualified, and the submarine high-voltage cable (14) is laid and connected.

Images