A protection method for the incoming line of a traction substation

Abstract

A protection method for the incoming line of a traction substation, including the step of determining the fault type after a fault occurs: calculating the number of phases n1 of all phases on the high voltage side of the traction transformer that satisfy |u Hsub (t)|≥U set1 ; calculating the number of phases n2 of all phases on the low voltage side of the traction transformer that satisfy |u Lsub (t)|≥U set2 ; if n1≥1 and n2≥1, it is determined as an incoming line fault; if n1 = 1 and n2 = 0, the phase that satisfies |u Hsub (t)|≥U set1 is determined as a voltage transformer disconnection fault; if n1 = 0 and n2 = 1, the phase that satisfies |u Lsub (t)|≥U set2 is determined as a voltage transformer disconnection fault. Among them, |u Hsub (t)| is the voltage increment on the high voltage side of the traction transformer, and |u Lsub (t)| is the voltage increment on the low voltage side of the traction transformer. The present invention can accurately determine the fault type, enabling the protection device to operate reliably in the case of full-phase voltage loss fault and open-phase fault of the incoming line; not affected by the voltage transformer disconnection fault, it can reliably identify the disconnection voltage transformer and will not malfunction; by updating the step of determining the fault type after a fault occurs in the existing protection device, the protection of the incoming line of the substation can be realized, which has the advantages of low cost and simple implementation.

Description

Technical Field

[0001] The present invention relates to the technical field of electrified railway power supply, and particularly to a protection method for the incoming line of a traction substation. Background Art

[0002] The traction substation adopts two incoming lines and has an automatic switching function. When a permanent fault occurs in the incoming line that is currently powered, after the reclosing attempt of the incoming line power supply side fails, the circuit breaker of the faulty power supply line is disconnected, resulting in a complete-phase power outage of the incoming line of the traction substation. Currently, the under-voltage protection of the incoming line of the traction substation operates after a complete-phase under-voltage of the incoming line, and cuts off the faulty incoming line. And through the automatic switching function, the standby incoming line is put into operation to restore the normal power supply to the traction power supply system.

[0003] With the rapid development of electrified railways, the under-voltage protection of the incoming line of the traction substation has the following problems: First, when a single-phase grounding fault occurs in the incoming line and the single-phase tripping technology is adopted on the power supply side, or when an incomplete-phase disconnection and non-grounding fault occurs in the incoming line, the incoming line of the traction substation operates with a phase missing, and no longer has a complete-phase under-voltage, which does not meet the complete-phase under-voltage operation condition of the existing under-voltage protection of the incoming line, resulting in the refusal of the existing under-voltage protection of the incoming line to operate; Second, the existing under-voltage protection of the incoming line of the traction substation has a weak fault tolerance for the voltage transformer disconnection fault, and it is difficult to accurately discriminate the incoming line fault after the voltage transformer disconnection fault occurs; Third, the current voltage transformer disconnection criterion is affected by the large residual voltage in the case of incomplete fusing of the fuse and the maximum load current of the heavy-load line being greater than the short-circuit current at the end of the line. When the voltage transformer disconnection fault occurs in the case of incomplete fusing of the voltage transformer or the heavy-load state of the line, the voltage transformer disconnection criterion refuses to operate, resulting in the misoperation of the under-voltage protection of the incoming line of the traction substation.

[0004] The refusal of the under-voltage protection of the incoming line of the traction substation will cause the voltage of the catenary in some power supply sections to drop or even power off, resulting in a significant decrease in the operating speed of the traction load or even stopping; the misoperation of the incoming line protection due to the disconnection fault of the bus voltage transformer of the traction substation will trigger the automatic switching function, resulting in a power outage of the traction substation for dozens of seconds to several minutes, seriously affecting the normal power supply of the traction power supply system and the safe operation of the traction load.

[0005] Currently, for the protection of the incoming line of the traction substation, mainly by improving the operation logic of the existing under-voltage protection of the incoming line of the traction substation, and using the sequence component characteristics of the high-voltage side incoming line of the traction substation to discriminate the incoming line fault. However, this type of solution has never been able to solve the problems of weak fault tolerance of the under-voltage protection of the incoming line to the voltage transformer disconnection fault and refusal to operate for the disconnection and non-grounding fault. Summary of the Invention

[0006] The present invention provides a protection method for the incoming line of a traction substation. Based on voltage increment for fault analysis, it can accurately determine the fault type and solve the problems existing in the current engineering applications, such as the refusal to operate in the case of incoming line open-phase operation and open-circuit fault, the low fault tolerance rate of the incoming line protection for voltage transformers, and the refusal to operate of the voltage transformer open-circuit criterion in the case of incomplete fuse open-circuit and heavy load operation state.

[0007] The technical solution for achieving the object of the present invention is as follows:

[0008] A protection method for the incoming line of a traction substation includes the step of determining the fault type after a fault occurs:

[0009] Calculate the number of phases n1 of all phases on the high voltage side of the traction transformer that satisfy |u Hsub (t)|≥U set1 ; calculate the number of phases n2 of all phases on the low voltage side of the traction transformer that satisfy |u Lsub (t)|≥U set2 ;

[0010] If n1≥1 and n2≥1, it is determined as an incoming line fault;

[0011] If n1 = 1 and n2 = 0, the phase that satisfies |u Hsub (t)|≥U set1 on the high voltage side is determined as a voltage transformer open-circuit fault;

[0012] If n1 = 0 and n2 = 1, the phase that satisfies |u Lsub (t)|≥U set2 on the low voltage side is determined as a voltage transformer open-circuit fault;

[0013] Among them, |u Hsub (t)| is the voltage increment on the high voltage side of the traction transformer, and |u Lsub (t)| is the voltage increment on the low voltage side of the traction transformer; U set1 is the setting value of the voltage increment criterion on the high voltage side, and U set2 is the setting value of the voltage increment criterion on the low voltage side.

[0014] A further technical solution

[0015] The voltage increment |u Hsub (t)| on the high voltage side of the traction transformer ∈ {u Asub (t)|, |u Bsub (t)|, |u Csub (t)|}; |u Asub (t)|, |u Bsub (t)| and |u Csub (t)| respectively represent the voltage increments of phase A, phase B and phase C on the high voltage side of the traction transformer;

[0016] The voltage increment |u Lsub (t)| on the low-voltage side of the traction transformer is specifically as follows:

[0017] If the traction transformer is a Yy-connected transformer, then |u Lsub (t)| ∈ {|u L1sub (t)|, |u L2sub (t)|}; |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the main and standby voltage transformers on the low-voltage side busbar;

[0018] If the traction transformer is a Yy-connected transformer, then |u Lsub (t)| ∈ {|u L1sub (t)|, |u L2sub (t)|}; |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the voltage transformers on the T-line busbar and the F-line busbar of the low-voltage side;

[0019] If the traction transformer is a Vv-connected transformer, then |u Lsub (t)| ∈ {|u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)|}; |u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)| respectively represent the voltage increments calculated using the main and standby voltage transformers on the α-phase and β-phase supply arm busbars of the low-voltage side;

[0020] If the traction transformer is a VX-connected transformer, then |u Lsub (t)| ∈ {|u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)|}; |u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)| respectively represent the voltage increments calculated using the voltage transformers on the T-line busbar and the F-line busbar of the α-phase and β-phase of the transformer low-voltage side;

[0021] If the traction transformer is a YNd11-connected transformer, then |uLsub (t) | ∈ { | u αsub (t) |, | u βsub (t) |} ; | u αsub (t) | 、 | u βsub (t) respectively represent the voltage increments calculated by the potential transformers on the α-phase and β-phase buses of the low-voltage side of the transformer;

[0022] If the traction transformer is a YNv-connected transformer, then | u Lsub (t) | ∈ { | u αsub (t) |, | u βsub (t) |} ; | u αsub (t) | 、 | u βsub (t) respectively represent the voltage increments calculated by the potential transformers on the α-phase and β-phase buses of the low-voltage side of the transformer;

[0023] If the traction transformer is a Scott-connected transformer, then | u Lsub (t) | ∈ { | u T1sub (t) |, | u T2sub (t) |, | u Msub (t) |} ; | u T1sub (t) | 、 | u T2sub (t) | 、 | u Msub (t) respectively represent the voltage increments calculated by the main potential transformer, standby potential transformer on the T-section bus of the low-voltage side of the transformer, and the potential transformer on the M-section bus.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) It can accurately determine the fault type, enabling the protection device to operate reliably in the case of full-phase loss of voltage fault and open-phase fault of the incoming line;

[0026] (2) It is not affected by the potential transformer disconnection fault, can reliably identify the disconnected potential transformer and will not malfunction;

[0027] (3) By updating the steps for determining the fault type after the existing protection device fails, the incoming line protection of the substation can be realized, which has the advantages of low cost and simple implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the equivalent circuit diagram of the high-voltage side of the traction power supply system.

[0029] Figure 2 It is the equivalent circuit diagram of the low-voltage side of the traction power supply system.

[0030] Figure 3 It is the equivalent circuit diagram of the incoming line fault. DETAILED DESCRIPTION OF THE INVENTION

[0031] Different traction power supply systems have different specific structures, and their equivalent circuits on the high- and low-voltage sides can be represented by Figure 1 and Figure 2 .

[0032] Figure 1 and Figure 2 In, Z' Tl and Z Tl are the equivalent impedances of the traction network on the high- and low-voltage sides of the traction transformer, and Z' LD and Z LD are the equivalent resistances of the traction load on the high- and low-voltage sides of the traction transformer; is the measured voltage value on the high-voltage side of the traction substation, is the measured line voltage value on the low-voltage side of the traction substation. is the measured current value on the incoming line side of the traction substation, is the measured current value on the low-voltage side of the traction transformer; is the equivalent voltage of the incoming line power supply of the traction substation on the high-voltage side, is the equivalent voltage of the incoming line power supply of the traction substation reduced to the low-voltage side. Z Tk and Z' Tk are the equivalent leakage impedances of the traction transformer on the high- and low-voltage sides, and their leakage reactance inductance L Tk and leakage resistance R Tk can be calculated from the rated voltage U N , rated capacity S N , short-circuit loss P k , short-circuit voltage percentage U k %, as shown in equations (1) and (2):

[0033]

[0034]

[0035] For Figure 1 and Figure 2 shown in the equivalent circuit of the traction power supply system, write the instantaneous state KVL equations for the measured voltage values u H_m (t), u L_m (t) and the incoming line power supplies E' S (t), E S (t):

[0036]

[0037] In equation (3), R' Tk and L' Tk are the equivalent leakage resistance and equivalent leakage inductance of the traction transformer on the low-voltage side, and L Sand L' S are the equivalent values of the incoming line equivalent power supply inductance on the high-voltage side and the low-voltage side respectively, and R s and R' s are the equivalent values of the incoming line equivalent power supply resistance on the high-voltage side and the low-voltage side respectively.

[0038] It can be seen from Equation (3) that the instantaneous state KVL equation one power frequency cycle ago is:

[0039]

[0040] In Equation (4), T is one power frequency cycle.

[0041] Here, let

[0042]

[0043] Subtract Equation (3) at the current moment from Equation (4) one power frequency cycle ago respectively:

[0044]

[0045] In Equation (6), ΔE' S (t) and ΔE S (t) are the increments of the incoming line power supply E S (t) within one power frequency cycle.

[0046] Since the incoming line power supply voltage does not change much in a short time, ΔE' S (t) = ΔE S (t) ≡ 0 holds; and the expressions on the right side of the equation in Equation (6) are all independent of the traction network impedance Z Tl and the load impedance Z LD , so it will not be affected by the load change and only depends on the accuracy of the low-voltage side current measurement value i(t) of the substation and the traction substation voltage measurement values u L_m (t), u H_m (t). Replace the incoming line voltage increments ΔE' S (t), ΔE S (t) in Equation (6) with the variables u Hsub (t) and u Lsub (t) respectively to obtain:

[0047]

[0048] When the incoming line of the traction substation is operating normally and a voltage transformer at a certain place fails with a broken wire, taking the broken wire fault of the high-voltage side voltage transformer as an example, within one cycle after the voltage transformer breaks, u Hsub (t) in (7) is not 0, but u LsubEquation (t)=0 still holds, as shown in Equation (8). That is, when a voltage transformer at one location has a disconnection fault, only the incoming line voltage increment corresponding to the voltage transformer with the disconnection fault in Equation (7) is not zero, and the incoming line voltage increments calculated from the voltage measurements of the other phases in the traction substation remain zero.

[0049]

[0050] When a fault occurs in the incoming line of the traction substation, if the fault type is incoming line short-circuit to ground, as Figure 3 shown.

[0051] At this time, write the KVL equation for the equivalent circuit of the traction power supply system:

[0052]

[0053] In Equation (9), R' S1 and R' S2 are the equivalent resistances of the incoming line power supply before and after the incoming line fault point, L' S1 and L' S2 are the equivalent reactances of the incoming line power supply before and after the incoming line fault point, R' S and Z' S are the equivalent resistance and reactance of the incoming line power supply, and i k (t) is the fault current component flowing into the ground through the fault point. Since the current measurement value of the traction substation does not include the fault current component i k (t), within one power frequency cycle after the fault, u Hsub (t)=0 and u Lsub (t)=0 in Equation (9) both do not hold, as shown in Equation (10).

[0054]

[0055] When a fault occurs in the incoming line of the traction substation, if the fault type is incoming line disconnection, it can be considered that Figure 1 and Figure 2 the incoming line power supply voltages E S (t) and E' S (t) suddenly become 0. Therefore, within one power frequency cycle after the fault occurs, u Hsub (t)=0 and u Lsub (t)=0 on both sides of the traction substation both do not hold:

[0056]

[0057] By calculating the voltage increments corresponding to the voltage measurement values on the high-voltage and low-voltage sides of the traction substation and comparing the magnitudes of the voltage increments within one power frequency cycle after the incoming line fault and the potential transformer disconnection fault, it can be found that when the potential transformer has a disconnection fault, only the voltage increment of the phase corresponding to the faulty potential transformer is not zero; when an incoming line fault occurs, the voltage increments on both the high-voltage and low-voltage sides of the traction substation corresponding to the faulty incoming line are not zero. Based on this, accurate discrimination of the incoming line fault and the potential transformer disconnection fault can be achieved.

[0058] Utilizing the above differences, the following incoming line protection method for the traction substation is proposed:

[0059] (1) Calculate the number of phases n1 of all phases on the high-voltage side of the traction transformer that satisfy |u Hsub (t)|≥U set1 ;

[0060] (2) Calculate the number of phases n2 of all phases on the low-voltage side of the traction transformer that satisfy |u Lsub (t)|≥U set2 ;

[0061] (3) If n1≥1 and n2≥1, it is judged as an incoming line fault;

[0062] (4) If n1 = 1 and n2 = 0, the phase that satisfies |u Hsub (t)|≥U set1 on the high-voltage side is judged as PT disconnection (potential transformer disconnection fault);

[0063] (5) If n1 = 0 and n2 = 1, the phase that satisfies |u Lsub (t)|≥U set2 on the low-voltage side is judged as PT disconnection.

[0064] Among them, U set1 and U set2 are the setting values of the voltage increment criteria for the high-voltage and low-voltage sides respectively, and are calculated by multiplying the rated voltages of the high-voltage and low-voltage sides of the traction transformer by a coefficient k (which can take values from 0.1 to 0.5).

[0065] After the fault is determined, the protection device performs corresponding operations according to the fault type, and the incoming line protection of the traction substation can be achieved. For example, when it is judged as an incoming line fault, if the incoming line voltage does not recover within the setting time Tset, the incoming line circuit breaker is tripped.

[0066] When implementing the incoming line protection method proposed in the present invention for various traction transformers, the voltage increment on the high-voltage side is calculated using Equation (12).

[0067]

[0068] In the formula, i A(t), i b (t), i C (t) respectively represent the measured values of the currents of the A, B, and C phases on the high-voltage side of the substation, and u A_m (t), u B_m (t), u C_m (t) respectively represent the measured values of the voltages of the A, B, and C phases on the high-voltage side of the substation.

[0069] The calculation formulas for the voltage increment on the low-voltage side of transformers with different wiring are slightly different. The following lists the common calculation formulas for the voltage increment on the low-voltage side of 7 types of transformers:

[0070] (1) For the low-voltage side of the Ii-connected transformer, |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the main and standby voltage transformers on the low-voltage side bus:

[0071]

[0072] In the formula, i L (t) is the measured value of the current on the low-voltage side of the substation; R' s and L' S are the equivalent resistance and inductance of the power system on the low-voltage side of the transformer, R' Tk and L' Tk are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the low-voltage side, u L1_m (t) and u L2_m (t) are the measured values of the voltages of the main and standby voltage transformers on the low-voltage side of the substation;

[0073] (2) For the Iii-connected transformer, |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the voltage transformer on the T-line bus and the voltage transformer on the F-line bus on the low-voltage side:

[0074]

[0075] In the formula, i T (t) and i F (t) are the measured values of the currents on the T-line and F-line on the low-voltage side of the substation, R' s and L' S are the equivalent resistance and inductance of the power system on the low-voltage side of the transformer, R' THk and L' THk are the equivalent resistance and inductance of the high-voltage side of the traction transformer on the low-voltage side, R TTk , L TTk , R TFk and L TFk$R_T$ and $X_T$ are the equivalent resistance and equivalent leakage reactance of the T line and F line on the low-voltage side of the traction transformer, and $u$ T_m $(t)$, $u$ F_m $(t)$ are the measured values of the low-voltage side voltage of the substation.

[0076] (3) For the Vv-connected transformer, $|u$ α1sub (t)|, $|u$ α2sub (t)|, $|u$ β1sub (t)|, $|u$ β2sub (t)| respectively represent the voltage increments calculated by the main and standby voltage transformers on the busbars of the supply arms of the α-phase and β-phase on the low-voltage side:

[0077]

[0078] In the formula, $R'$ s and $L'$ S are the equivalent resistance and inductance of the power system on the low-voltage side of the transformer, $R'$ Tk and $L'$ Tk are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the low-voltage side, $i$ α (t) and $i$ β (t) are the measured values of the α-phase and β-phase currents on the low-voltage side of the substation; $u$ α1_m (t) and $u$ α2_m (t) are the measured values of the voltages of the main and standby voltage transformers of the α-phase busbar on the low-voltage side of the substation; $u$ β1_m (t) and $u$ β2_m (t) are the measured values of the voltages of the main and standby voltage transformers of the β-phase busbar on the low-voltage side of the substation.

[0079] (4) For the VX-connected transformer, $|u$ α1sub (t)|, $|u$ α2sub (t)|, $|u$ β1sub (t)|, $|u$ β2sub (t)| respectively represent the voltage increments calculated by the voltage transformers of the T-line busbar and F-line busbar of the α-phase and β-phase on the low-voltage side of the transformer:

[0080]

[0081] In formula (16), $R'$ THk and $L'$ THk are the equivalent resistance and inductance of the leakage reactance of the high-voltage winding of the VX traction transformer on the low-voltage side, $R$ TTk and $R$ TFk are the leakage resistances of the low-voltage T-line winding and F winding of the VX traction transformer on the low-voltage side respectively, $L$ TTk and $L$ TFk are the leakage inductances of the low-voltage T-line winding and F winding of the VX traction transformer on the low-voltage side respectively, $i$α1 (t) and i α2 (t) are the measured values of the currents of the T-line and F-line of phase α on the low-voltage side of the substation; i β1 (t) and i β2 (t) are the measured values of the currents of the T-line and F-line of phase α and phase β on the low-voltage side of the substation, respectively; i α (t) and i β (t) are the differences between the measured values of the currents of the T-line and F-line of phase α and phase β on the low-voltage side of the substation; u T1_m (t), u T2_m (t), u F1_m (t) and u F2_m (t) are the measured values of the voltages of the voltage transformers of the T-line and F-line buses of phase α and phase β on the low-voltage side of the substation;

[0082] (5) For a YNd11-connected transformer, |u αsub (t)| and |u βsub (t)| respectively represent the voltage increments calculated using the voltage transformers on the buses of phase α and phase β on the low-voltage side of the transformer:

[0083]

[0084] In the formula, R' Tk and L' Tk are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the low-voltage side, i α (t) and i β (t) are the measured values of the currents of phase α and phase β on the low-voltage side of the substation; u α_m (t) and u β_m (t) are the measured values of the voltages of the voltage transformers of the buses of phase α and phase β on the low-voltage side of the substation.

[0085] (6) For a YNv-connected transformer, |u αsub (t)| and |u βsub (t)| respectively represent the voltage increments calculated using the voltage transformers on the buses of phase α and phase β on the low-voltage side of the transformer:

[0086]

[0087] In the formula, L' S1 and L' S2 are the equivalent inductances of the incoming power supply on the delta-winding side and the auxiliary-winding side of the transformer, respectively, and R' S1 and R' S2 are the equivalent resistances of the incoming power supply on the delta-winding side and the auxiliary-winding side of the transformer, respectively, and R' Tk1 and L' Tk1 are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the delta-winding side, R'Tk2 and L' Tk2 are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the auxiliary winding side, i α (t) and i β (t) are the measured values of the currents of phase α and phase β on the low-voltage side of the substation; u α_m (t) and u β_m (t) are the measured values of the voltages of the voltage transformers of phase α and phase β busbars on the low-voltage side of the substation.

[0088] (7) For a Scott-connected transformer, |u T1sub (t)|, |u T2sub (t)|, |u Msub (t) respectively represent the voltage increments calculated using the main voltage transformer of the T-busbar, the standby voltage transformer, and the voltage transformer of the M-busbar on the low-voltage side of the transformer;

[0089]

[0090] In the formula, R' S and L' S are the equivalent resistance and equivalent inductance of the power system on the low-voltage side of the transformer, R' Tk and L' Tk are the equivalent resistance and inductance of the leakage reactance of the traction transformer on the low-voltage side, i T (t) and i M (t) are the measured values of the currents of the T-busbar and the M-busbar on the low-voltage side of the substation; u T1_m (t), u T2_m (t) and u M_m (t) are the measured values of the voltages of the main voltage transformer of the T-busbar, the standby voltage transformer, and the voltage transformer of the M-busbar on the low-voltage side of the substation respectively.

[0091] Based on the fact that voltage increments are simultaneously detected on both the high-voltage and low-voltage sides of the traction substation during an incoming line fault, the present invention proposes a protection method for the incoming line of the traction substation, which can effectively solve the problems of the incoming line undervoltage protection of the current traction substation being refused to operate in the states of incoming line open-phase operation and open-circuit fault and having a low tolerance rate for voltage transformers.

Claims

1. A protection method for the incoming line of a traction substation, characterized in that, Including the step of determining the fault type after a fault occurs: Calculate the number of phases \(n_1\) of all phases on the high-voltage side of the traction transformer that satisfy \(|u Hsub (t)|\geq U set1 \); calculate the number of phases \(n_2\) of all phases on the low-voltage side of the traction transformer that satisfy \(|u Lsub (t)|\geq U set2 \). If n1≥1 and n2≥1, it is determined as an incoming line fault; If n1 = 1 and n2 = 0, then for the phase where the high-voltage side |u Hsub (t)| ≥ U set1 is satisfied, it is determined as a voltage transformer open-circuit fault; If n1 = 0 and n2 = 1, then for the phase that satisfies |u Lsub (t)| ≥ U set2 , it is determined as a voltage transformer open - circuit fault; Among them, |u Hsub (t)| is the voltage increment on the high-voltage side of the traction transformer, and |u Lsub (t)| is the voltage increment on the low-voltage side of the traction transformer; U set1 is the setting value of the voltage increment criterion on the high-voltage side, and U set2 is the setting value of the voltage increment criterion on the low-voltage side.

2. A traction substation incoming line protection method according to claim 1, characterized in that The voltage increment |u Hsub (t)| of the high-voltage side of the traction transformer belongs to {|u Asub (t)|, |u Bsub (t)|, |u Csub (t)|}; |u Asub (t)|, |u Bsub (t)|, and |u Csub (t)| respectively represent the voltage increments of phase A, phase B, and phase C on the high-voltage side of the traction transformer; The voltage increment |u Lsub (t)| on the low-voltage side of the traction transformer is specifically as follows: If the traction transformer is a Yy connection transformer, then |u Lsub (t)| ∈ {|u L1sub (t)|, |u L2sub (t)|}; |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the main and standby voltage transformers on the low-voltage side busbar; If the traction transformer is a Yy connection transformer, then |u Lsub (t)| ∈ {|u L1sub (t)|, |u L2sub (t)|}; |u L1sub (t)| and |u L2sub (t)| respectively represent the voltage increments calculated using the bus voltage transformers on the T line and F line of the low-voltage side; If the traction transformer is a Vv-connected transformer, then |u Lsub (t)| ∈ {|u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)|}; |u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)| respectively represent the voltage increments calculated by the main and standby voltage transformers on the α-phase and β-phase power supply arm busbars of the low-voltage side; If the traction transformer is a VX-connected transformer, then |u Lsub (t)| ∈ {|u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)|}; |u α1sub (t)|, |u α2sub (t)|, |u β1sub (t)|, |u β2sub (t)| respectively represent the voltage increments calculated by the T-line bus voltage transformers and F-line bus voltage transformers of the α-phase and β-phase on the low-voltage side of the transformer; If the traction transformer is a YNd11 connection transformer, then |u Lsub (t)| ∈ {|u αsub (t)|, |u βsub (t)|}; |u αsub (t)| and |u βsub (t)| respectively represent the voltage increments calculated by the potential transformers on the α-phase and β-phase buses of the low-voltage side of the transformer; If the traction transformer is a YNv-connected transformer, then |u Lsub (t)| ∈ {|u αsub (t)|, |u βsub (t)|}; |u αsub (t)|, |u βsub (t) represent the voltage increments calculated by the potential transformers on the α-phase and β-phase buses of the low-voltage side of the transformer respectively; If the traction transformer is a Scott-connected transformer, then |u Lsub (t)| ∈ {|u T1sub (t)|, |u T2sub (t)|, |u Msub (t)|}; |u T1sub (t)|, |u T2sub (t)|, |u Msub (t)| respectively represent the voltage increments calculated using the main voltage transformer of the T-side busbar of the transformer low-voltage side, the standby voltage transformer, and the voltage transformer of the M-side busbar.

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