High-voltage transformer sudden short circuit network direct test main loop

Abstract

The utility model discloses a high-voltage transformer sudden short circuit network direct test main loop which comprises a single-phase test system main loop and a three-phase test system main loop. A test power supply of the main loop comprises three short-circuit transformers TM connected with a 330kV substation power system, a primary side winding of each short-circuit transformer TM is connected with a power supply of the power system through an isolating switch QS, and a secondary side winding of each short-circuit transformer TM is connected with a high-voltage line of the test main loop through the isolating switch QS. Through Y / delta conversion of the primary side winding and the secondary side winding of the short-circuit transformer and various combinations of switching-on and switching-off of the disconnecting switch connected with the short-circuit transformer, a main loop can provide current and voltage which are large enough, the test loop is simple, the number of programs is small, the number of control devices is small, transformer sudden short-circuit tests of 45kV-330kV voltage classes of single-phase and three-phase transformers can be carried out respectively, and the test efficiency is high. The test cost and the equipment investment cost are greatly reduced, and dangers and hidden dangers possibly existing in the test process are also reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of high-voltage electrical appliance detection, in particular to a main circuit for a sudden short-circuit network direct test of a high-voltage transformer. Background Art

[0002] Power systems inevitably encounter short-circuit events during operation. As installed capacity increases, the capacity of high-voltage, high-capacity transformers also increases, significantly increasing the current amplitude during short-circuit events. Therefore, examining the dynamic thermal stability of transformers when subjected to short-circuit currents is crucial.

[0003] The sudden short-circuit test of a transformer is a crucial testing method. It uses the electrodynamic forces generated by a strong short-circuit current to test the mechanical strength of the transformer and its conductive components, assessing their dynamic stability. It also serves as a comprehensive examination of the transformer's manufacturing technology and process capabilities. Under the impact of a short-circuit current, the transformer experiences enormous instantaneous electrodynamic forces, which directly impact the stability of the transformer windings. Furthermore, the heat generated by the short-circuit is a key factor in testing the transformer's insulation resistance and thermal stability.

[0004] Sudden short-circuit tests on power transformers are conducted in a laboratory environment to simulate the short-circuit conditions that the transformer may encounter in actual operation. This ensures the transformer's safe operation under short-circuit shocks, prevents damage or failure, and thus safeguards the stability and safety of the entire power system. The large-capacity power supply required for actual implementation is typically a short-circuit generator, which is not only costly but also difficult to simulate actual grid short-circuit fault conditions. When designing the main circuit for a transformer's sudden short-circuit test, it is important to consider that the test circuit must be able to withstand the high currents and mechanical stresses generated during the test. Flexible and diverse wiring designs are also required to meet the requirements of different test voltages and test methods. Utility Model Content

[0005] The purpose of the utility model is to provide a main circuit for a high-voltage transformer sudden short-circuit network direct test. Through reasonable circuit design and configuration, the main circuit can provide sufficiently large current and voltage to meet the requirements of the ultra-high voltage transformer sudden short-circuit test.

[0006] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0007] A high-voltage transformer sudden short-circuit network direct test main circuit, including a single-phase test system main circuit and a three-phase test system main circuit;

[0008] The main circuit of the three-phase test system includes the first high-voltage line, the second high-voltage line and the third high-voltage line connected between the three-phase test power supply A, B, and C and the test transformer. The three high-voltage lines are connected in series with the disconnector QS, the operating circuit breaker QF, the closing switch HK, the reactor L and the front shunt RS. After entering the test room, the three high-voltage lines are respectively connected to the incoming line of the three-phase test transformer. The outgoing line of the three-phase test transformer is respectively connected in series with the rear shunt RS and the closing switch HK and then grounded. The three-phase test power supply includes a short-circuit transformer TM1 connected to the 330kV substation power system. , short-circuit transformer TM2 and short-circuit transformer TM3. Each short-circuit transformer TM is provided with four parallel windings on its primary side. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the isolating switch QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the isolating switch QS. The three-phase voltages of the primary and secondary windings are subjected to Y / Δ transformation. The secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 are connected in series and parallel in 12 ways. The three-phase secondary side of the short-circuit transformer has 12 output voltage values ranging from 45kV to 270kV.

[0009] The main circuit of the single-phase test system includes the first high-voltage line and the fourth high-voltage line connected between the single-phase test power supply and the test transformer. The first high-voltage line is connected in series with the isolating switch QS1, the operating circuit breaker QF1, the closing switch HK1, the reactor L1 and the front shunt RS1. The fourth high-voltage line is connected in series with the isolating switch QS4, the closing switch HK4, the test system isolating switch QS5 and the reactor L4. After entering the test room, the two high-voltage lines are respectively connected to the incoming line terminals of the single-phase test transformer. The first outgoing line terminal of the single-phase test transformer is connected in series with the rear shunt RS4 and the closing switch HK4 and then grounded. The second outgoing line terminal of the single-phase test transformer is connected in series with the closing switch The HK7 phase is connected in series and then grounded; the single-phase test power supply includes short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 connected to the 330kV substation power system. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the disconnector QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the disconnector QS; each short-circuit transformer TM is provided with four windings in parallel on the primary side, and there are 22 connection methods for the series-parallel combination of the 3×4 secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3. The secondary side of the short-circuit transformer has 13 output voltage values of 78kV-468kV.

[0010] Preferably, the second high-voltage line in the main circuit of the three-phase test system is further connected in series with an isolating switch QS6 between the reactor L2 and the pre-shunt RS2, and the third high-voltage line is further connected in series with a second isolating switch QS7 between the reactor L3 and the pre-shunt RS3.

[0011] Preferably, the operating circuit breaker QF and the closing switch HK in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV1, and the operating circuit breaker QF and the test system isolating switch QS5 in the fourth high-voltage line are connected to the other phase of the resistor-capacitor voltage divider MTV1.

[0012] Preferably, the pre-shunt RS in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer, and the reactor L4 in the fourth high-voltage line is connected to the other phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer.

[0013] Preferably, the voltage of the secondary winding of the short-circuit transformer TM is 26kV or 52kV, and the secondary three-phase output voltage values of the short-circuit transformer TM in the main circuit of the three-phase test system include 12 output voltage values including 78kV, 104kV, 130kV, 156kV, 45kV, 60kV, 75kV, 90kV, 135kV, 180kV, 225kV and 270kV.

[0014] Preferably, the voltage of the secondary winding of the short-circuit transformer TM is 26kV or 52kV, and the secondary side of the short-circuit transformer in the main circuit of the single-phase test system has 13 output voltage values, including 78kV, 104kV, 130kV, 156kV, 180kV, 208kV, 260kV, 312kV, 234kV, 390kV, 468kV, 286kV, and 338kV.

[0015] When the utility model is in use, the operator selects different secondary side output voltage values of the short-circuit transformer according to test needs, and at the same time adjusts the impedance parameters of the reactor L1, the reactor L2, and the reactor L3, controls the actions of the closing switch HK4, the closing switch HK5, and the closing switch HK6, and the resistor-capacitor voltage divider MTV1, the resistor-capacitor voltage divider MTV2, the rear shunt RS4, the rear shunt RS5, and the rear shunt RS6 transmit the collected voltage and current data to the data acquisition system, and performs a sudden short-circuit test of the high-voltage transformer in accordance with the requirements of the standard.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) In the present invention, through the Y / Δ transformation of the primary winding and the secondary winding of the short-circuit transformer, and the various combinations of opening and closing of the connected disconnector, the main circuit can provide sufficiently large current and voltage, so that the test capacity and voltage level are improved; the present invention can replace the large-capacity short-circuit generator, the power system network system has a large short-circuit capacity, and the test circuit is simple, the test procedure is small, and the control equipment is small. It can carry out transformer sudden short-circuit tests of single-phase and three-phase transformers with voltage levels of 45kV-330kV, which greatly reduces the test cost and equipment investment cost, and also reduces the dangers and hidden dangers that may exist during the test process;

[0018] (2) The main circuit of the present invention can simulate the actual short-circuit fault conditions of the power grid, including the magnitude, waveform and duration of the short-circuit current, by performing Y / Δ transformation of the primary and secondary windings of the short-circuit transformer and various combinations of opening and closing of the connected disconnector, thereby more accurately evaluating the performance and tolerance of the transformer;

[0019] (3) Compared with the traditional large-capacity short-circuit generator method, the main circuit of the utility model uses low-cost components and is easy to replace and maintain, which reduces the cost of the main circuit and is easy to implement and promote;

[0020] (4) The design of the main circuit described in the utility model takes into account the test requirements of ultra-high voltage transformers of different voltage levels and capacities, has high flexibility and scalability, and can carry out short-circuit tests on single-phase transformers or three-phase transformers. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the short-circuit principle diagram of the utility model;

[0022] Figure 2 This is the flow chart of transformer sudden short circuit test. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 A high-voltage transformer sudden short-circuit network direct test main circuit shown includes a single-phase test system main circuit and a three-phase test system main circuit;

[0025] The main circuit of the three-phase test system includes the first high-voltage line, the second high-voltage line and the third high-voltage line connected between the three-phase test power supply A, B, and C and the test transformer. The three high-voltage lines are connected in series with the disconnector QS, the operating circuit breaker QF, the closing switch HK, the reactor L and the front shunt RS. After entering the test room, the three high-voltage lines are respectively connected to the incoming line of the three-phase test transformer. The outgoing line of the three-phase test transformer is respectively connected in series with the rear shunt RS and the closing switch HK and then grounded. The three-phase test power supply includes a short-circuit transformer TM1 connected to the 330kV substation power system. , short-circuit transformer TM2 and short-circuit transformer TM3. Each short-circuit transformer TM is provided with four parallel windings on its primary side. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the isolating switch QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the isolating switch QS. The three-phase voltages of the primary and secondary windings are subjected to Y / Δ transformation. The secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 are connected in series and parallel in 12 ways. The three-phase secondary side of the short-circuit transformer has 12 output voltage values ranging from 45kV to 270kV.

[0026] The main circuit of the single-phase test system includes the first high-voltage line and the fourth high-voltage line connected between the single-phase test power supply and the test transformer. The first high-voltage line is connected in series with the isolating switch QS1, the operating circuit breaker QF1, the closing switch HK1, the reactor L1 and the front shunt RS1. The fourth high-voltage line is connected in series with the isolating switch QS4, the closing switch HK4, the test system isolating switch QS5 and the reactor L4. After entering the test room, the two high-voltage lines are respectively connected to the incoming line terminals of the single-phase test transformer. The first outgoing line terminal of the single-phase test transformer is connected in series with the rear shunt RS4 and the closing switch HK4 and then grounded. The second outgoing line terminal of the single-phase test transformer is connected in series with the closing switch The HK7 phase is connected in series and then grounded; the single-phase test power supply includes short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 connected to the 330kV substation power system. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the disconnector QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the disconnector QS; each short-circuit transformer TM is provided with four windings in parallel on the primary side, and there are 22 connection methods for the series-parallel combination of the 3×4 secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3. The secondary side of the short-circuit transformer has 13 output voltage values of 78kV-468kV.

[0027] The second high-voltage line in the main circuit of the three-phase test system is further connected in series with an isolating switch QS6 between the reactor L2 and the pre-shunt RS2, and the third high-voltage line is further connected in series with a second isolating switch QS7 between the reactor L3 and the pre-shunt RS3.

[0028] The operating circuit breaker QF and the closing switch HK in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV1, and the operating circuit breaker QF and the test system isolating switch QS5 in the fourth high-voltage line are connected to the other phase of the resistor-capacitor voltage divider MTV1.

[0029] The pre-shunt RS in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer, and the reactor L4 in the fourth high-voltage line is connected to the other phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer.

[0030] During the sudden short-circuit test of three-phase transformer, the connection method of short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 is as follows: Figure 1 As shown, the primary side has four windings connected in parallel, the voltage of the secondary winding x1, secondary winding x2, secondary winding y1, secondary winding y2, secondary winding z1, and secondary winding z2 is 52kV, and the voltage of the secondary winding x3, secondary winding x4, secondary winding y3, secondary winding y4, secondary winding z3, and secondary winding z4 is 26kV. Through the Y / Δ transformation of the primary and secondary windings, the short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM4 are connected in parallel. There are 12 connection methods for the series-parallel combination of the secondary windings of short-circuit transformer TM3. The secondary output voltages are 78kV, 104kV, 130kV, 156kV, 45kV, 60kV, 75kV, 90kV, 135kV, 180kV, 225kV, and 270kV. The following lists the specific connection methods for the secondary three-phase output voltages of 45kV, 75kV, and 60kV for short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM3:

[0031] (1) The secondary side output voltage is 45kV: the disconnectors QS34, QS35, QS38, QS41, QS42 and QS43 connected to the primary windings of the short-circuit transformer TM1, the short-circuit transformer TM2 and the short-circuit transformer TM3 are closed; the disconnectors QS8, QS11, QS10 and Q13 connected to the secondary windings are closed; the disconnectors QS16, QS18, QS19 and QS21 inside the short-circuit transformer TM1 are closed; the disconnectors QS22, QS24, QS25 and QS27 inside the short-circuit transformer TM2 are closed; the disconnectors QS28, QS30, QS31 and QS33 inside the short-circuit transformer TM3 are closed; and the remaining disconnectors are opened;

[0032] (2) The secondary side output voltage is 75kV: the disconnectors QS34, QS35, QS38, QS41, QS42 and QS43 connected to the primary windings of the short-circuit transformer TM1, the short-circuit transformer TM2 and the short-circuit transformer TM3 are closed; the disconnectors QS8, QS11, QS10 and Q13 connected to the secondary windings are closed; the disconnectors QS16, QS18 and QS20 inside the short-circuit transformer TM1 are closed; the disconnectors QS26, QS24 and QS22 inside the short-circuit transformer TM2 are closed; the disconnectors QS28, QS30 and QS32 inside the short-circuit transformer TM3 are closed; and the remaining disconnectors are opened;

[0033] (3) The secondary side output voltage is 60 kV: the disconnectors QS34, QS35, QS38, QS41, QS42 and QS43 connected to the primary windings of the short-circuit transformer TM1, the short-circuit transformer TM2 and the short-circuit transformer TM3 are closed; the disconnectors QS8, QS11, QS10 and Q13 connected to the secondary windings are closed; the disconnectors QS19, QS17 and QS21 inside the short-circuit transformer TM1 are closed; the disconnectors QS27, QS25 and QS23 inside the short-circuit transformer TM2 are closed; the disconnectors QS33, QS31 and QS29 inside the short-circuit transformer TM3 are closed; and the remaining disconnectors are opened.

[0034] During the single-phase transformer sudden short-circuit test, the connection method of short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM3 is as follows: Figure 1 As shown in the figure, the primary sides of the three short-circuit transformers all have four windings connected in parallel. The voltage of the secondary winding x1, secondary winding x2, secondary winding y1, secondary winding y2, secondary winding z1, and secondary winding z2 is 52 kV, and the voltage of the secondary winding x3, secondary winding x4, secondary winding y3, secondary winding y4, secondary winding z3, and secondary winding z4 is 26 kV. There are 22 connection methods for the series-parallel combination of the 3×4 secondary windings of the short-circuit transformer TM. When the primary winding voltage is 330 kV, the secondary winding output voltages are 13 different output voltage values, namely 78 kV, 104 kV, 130 kV, 156 kV, 180 kV, 208 kV, 260 kV, 312 kV, 234 kV, 390 kV, 468 kV, 286 kV, and 338 kV. The following lists the specific connection methods for the short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM3 with secondary-side single-phase output voltages of 78kV, 130kV, and 180kV:

[0035] (1) Secondary side output voltage 78kV: Close the disconnectors QS34, QS36, QS39, QS40, QS42, and QS44 connected to the primary windings of short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM3, and connect them to the power supply lines A and C respectively. Close the disconnectors QS14, QS9, QS11, and QS8 connected to the secondary windings of short-circuit transformer TM1, short-circuit transformer TM2, and short-circuit transformer TM3, so that the secondary windings ax and b are connected. y, and the secondary winding cz are connected in parallel to the power output line phase A and the power output line phase C; the isolating switches QS16, QS18, QS19, and QS21 inside the short-circuit transformer TM1 are closed; the isolating switches QS22, QS24, QS25, and QS27 inside the short-circuit transformer TM2 are closed; the isolating switches QS28, QS30, QS31, and QS33 inside the short-circuit transformer TM3 are closed; and the remaining isolating switches are open;

[0036] (2) Secondary side output voltage 130kV: Close the disconnectors QS34, QS36, QS39, QS40, QS42 and QS44 connected to the primary windings of short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3, and connect them to the power supply line A phase and power supply line C phase respectively; and close the disconnectors QS14, QS9 and QS1 connected to the secondary windings of short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3. 1. Close the disconnector QS8, connecting the secondary windings ax, by, and cz in parallel and then connecting them to the power output lines A and C. Close the disconnectors QS16, QS18, and QS20 inside the short-circuit transformer TM1. Close the disconnectors QS22, QS24, and QS26 inside the short-circuit transformer TM2. Close the disconnectors QS28, QS30, and QS32 inside the short-circuit transformer TM3. Open the remaining disconnectors.

[0037] (3) Secondary side output voltage 180kV: Close the disconnectors QS34, QS35, QS39, QS41, QS42 and QS43 connected to the primary windings of short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3, connect the power supply line A phase and power supply line C phase, and disconnectors QS9, QS12 and QS15 connected to the secondary windings of short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3. , the isolating switch QS7 is closed, so that the secondary winding ax and the secondary winding by are connected in parallel and then connected to the power output line phase A and the power output line phase C; the isolating switches QS19, QS21, and QS17 inside the short-circuit transformer TM1 are closed, the isolating switches QS25, QS27, and QS23 inside the short-circuit transformer TM2 are closed, the isolating switches QS31, QS33, QS28, and QS30 inside the short-circuit transformer TM3 are closed, and the remaining isolating switches are all opened.

[0038] When the utility model is in use, the operator selects different secondary side output voltage values of the short-circuit transformer according to test needs, and at the same time adjusts the impedance parameters of the reactor L1, the reactor L2, and the reactor L3, controls the actions of the closing switch HK4, the closing switch HK5, and the closing switch HK6, and the resistor-capacitor voltage divider MTV1, the resistor-capacitor voltage divider MTV2, the rear shunt RS4, the rear shunt RS5, and the rear shunt RS6 transmit the collected voltage and current data to the data acquisition system, and performs a sudden short-circuit test of the high-voltage transformer in accordance with the requirements of the standard.

[0039] In the utility model, through the Y / Δ transformation of the primary and secondary windings of the short-circuit transformer and the various combinations of opening and closing of the connected disconnector, the main circuit can provide sufficiently large current and voltage, so that the test capacity and voltage level are improved; the utility model can replace the large-capacity short-circuit generator, the power system network system has a large short-circuit capacity, and the test circuit is simple, the test procedure is small, and the control equipment is small. It can carry out sudden short-circuit tests of single-phase and three-phase transformers with a voltage level of 45kV-330kV, greatly reducing the test cost and equipment investment cost, and also reducing the dangers and hidden dangers that may exist during the test process.

[0040] The above are only preferred embodiments of the present invention. It should be noted that those skilled in the art can make other equivalent variations and improvements based on the technical enlightenment provided by the present invention, which should also be considered as the scope of protection of the present invention.

Claims

1. A high-voltage transformer sudden short-circuit network direct test main circuit, characterized by: Including single-phase test system main circuit and three-phase test system main circuit; The main circuit of the three-phase test system includes the first high-voltage line, the second high-voltage line and the third high-voltage line connected between the three-phase test power supply A, B, and C and the test transformer. The three high-voltage lines are connected in series with the disconnector QS, the operating circuit breaker QF, the closing switch HK, the reactor L and the front shunt RS. After entering the test room, the three high-voltage lines are respectively connected to the incoming line of the three-phase test transformer. The outgoing line of the three-phase test transformer is respectively connected in series with the rear shunt RS and the closing switch HK and then grounded. The three-phase test power supply includes a short-circuit transformer TM1 connected to the 330kV substation power system. , short-circuit transformer TM2 and short-circuit transformer TM3. Each short-circuit transformer TM is provided with four parallel windings on its primary side. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the isolating switch QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the isolating switch QS. The three-phase voltages of the primary and secondary windings are subjected to Y / Δ transformation. The secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 are connected in series and parallel in 12 ways. The three-phase secondary side of the short-circuit transformer has 12 output voltage values ranging from 45kV to 270kV. The main circuit of the single-phase test system includes the first high-voltage line and the fourth high-voltage line connected between the single-phase test power supply and the test transformer. The first high-voltage line is connected in series with the isolating switch QS1, the operating circuit breaker QF1, the closing switch HK1, the reactor L1 and the front shunt RS1. The fourth high-voltage line is connected in series with the isolating switch QS4, the closing switch HK4, the test system isolating switch QS5 and the reactor L4. After entering the test room, the two high-voltage lines are respectively connected to the incoming line terminals of the single-phase test transformer. The first outgoing line terminal of the single-phase test transformer is connected in series with the rear shunt RS4 and the closing switch HK4 and then grounded. The second outgoing line terminal of the single-phase test transformer is connected in series with the closing switch The HK7 phase is connected in series and then grounded; the single-phase test power supply includes short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3 connected to the 330kV substation power system. The primary winding of the short-circuit transformer TM is connected to the power system power supply through the disconnector QS, and the secondary winding is connected to the high-voltage line of the test main circuit through the disconnector QS; each short-circuit transformer TM is provided with four windings in parallel on the primary side, and there are 22 connection methods for the series-parallel combination of the 3×4 secondary windings of the short-circuit transformer TM1, short-circuit transformer TM2 and short-circuit transformer TM3. The secondary side of the short-circuit transformer has 13 output voltage values of 78kV-468kV.

2. A high-voltage transformer sudden short-circuit network direct test main circuit according to claim 1, characterized in that: The second high-voltage line in the main circuit of the three-phase test system is further connected in series with an isolating switch QS6 between the reactor L2 and the pre-shunt RS2, and the third high-voltage line is further connected in series with a second isolating switch QS7 between the reactor L3 and the pre-shunt RS3.

3. A high-voltage transformer sudden short-circuit network direct test main circuit according to claim 1 or 2, characterized in that: The operating circuit breaker QF and the closing switch HK in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV1, and the operating circuit breaker QF and the test system isolating switch QS5 in the fourth high-voltage line are connected to the other phase of the resistor-capacitor voltage divider MTV1.

4. A high-voltage transformer sudden short-circuit network direct test main circuit according to claim 1 or 2, characterized in that: The pre-shunt RS in the first high-voltage line, the second high-voltage line and the third high-voltage line are respectively connected to one phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer, and the reactor L4 in the fourth high-voltage line is connected to the other phase of the resistor-capacitor voltage divider MTV2 between the incoming line terminal of the test transformer.

5. The high-voltage transformer sudden short-circuit network direct test main circuit according to claim 1, characterized in that: The voltage of the secondary winding of the short-circuit transformer TM is 26kV or 52kV. The three-phase output voltage values of the secondary side of the short-circuit transformer TM in the main circuit of the three-phase test system include 12 output voltage values including 78kV, 104kV, 130kV, 156kV, 45kV, 60kV, 75kV, 90kV, 135kV, 180kV, 225kV, and 270kV.

6. The high-voltage transformer sudden short-circuit network direct test main circuit according to claim 1, characterized in that: The voltage of the secondary winding of the short-circuit transformer TM is 26kV or 52kV. The secondary side of the short-circuit transformer in the main circuit of the single-phase test system has 13 output voltage values: 78kV, 104kV, 130kV, 156kV, 180kV, 208kV, 260kV, 312kV, 234kV, 390kV, 468kV, 286kV, and 338kV.

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