Parallel double-circuit line protection method and system based on single-end transient state quantity information

Abstract

The invention provides a parallel double-circuit line protection method and system based on single-end transient state quantity information, and belongs to the technical field of power system relay protection. Comprising the following steps: sampling according to voltage and current waveforms at two ends of a bus of a current-level line where a mutual inductor collects a fault point, obtaining instantaneous values of a fault phase voltage of a fault loop, a fault phase current of the fault loop, a zero-sequence current and a zero-sequence current of an adjacent non-fault loop, and further calculating transient quantities U (t) LP phi, I (t) LP phi, I (t) LP 0 and I (t) LQ0; and establishing an arbitrary single-phase earth fault model of the parallel double-circuit line, an intermediate quantity M (t), and an expression of the ULP phi (t) and the correction coefficient H with respect to the M (t), and further obtaining a derivation formula of the distance D between the protection installation position and the fault point. According to the method, transient quantity information calculation is adopted, the used data is 1 / 4 period data volume, accurate calculation of the fault distance can be achieved only in 4-5 ms, the correction coefficient H is utilized, the influence of sudden change before and after the fault is considered, and the influence of the transient process can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection of electric power systems, and in particular to a parallel double-circuit line protection method and system based on single-end transient quantity information. Background Art

[0002] Transmission lines are used to transmit electricity to power plants in power systems. When a transmission line fails, it is necessary to promptly remove the fault and perform maintenance. Otherwise, it is easy to cause major accidents such as power grid decoupling and transformer over-tripping. In high-voltage / ultra-high-voltage / ultra-high-voltage parallel transmission lines, distance protection reflects the distance of the fault point based on the size of the measured impedance. Its performance is basically unaffected by the system operation mode. It can selectively remove faults in complex power grids, and it has sufficient sensitivity and speed. Therefore, distance protection has always been the main protection method for high-voltage / ultra-high-voltage / ultra-high-voltage parallel transmission line protection. After the fault is removed, it is necessary to quickly and accurately calculate the distance between the protection device and the fault point in the parallel double-circuit line, and quickly locate the fault position to efficiently restore system operation. Summary of the invention

[0003] In view of this, the present invention provides a parallel double-circuit line protection method and system based on single-ended transient quantity information, which calculates the fault distance by using the single-ended voltage and current of the protected line in the parallel line, and reduces the influence of the sudden change before and after the fault by the correction coefficient H, effectively avoiding the influence of the transient process and improving the calculation accuracy.

[0004] The technical solution adopted by the embodiment of the present invention to solve the technical problem is:

[0005] A parallel double-circuit line protection method based on single-end transient quantity information, comprising:

[0006] Step S1, sampling the voltage and current waveforms of the busbar at both ends of the current line where the fault point is located by the mutual inductor to obtain the fault phase voltage of the fault circuit Fault phase current of fault circuit Zero sequence current i LP0 (t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t), and further calculate the transient quantity I(t) LP0 、I(t) LQ0 :

[0007]

[0008] Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926;

[0009] Step S2: for any single-phase ground fault in a parallel double-circuit line, define expression:

[0010]

[0011] Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1; Z0 is zero sequence impedance, Z0=R0+jX0; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 It is approximately equal to 0 and can be ignored; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point;

[0012] Step S3, define the intermediate quantity M(t), and The expression of M(t) is:

[0013]

[0014] Among them, the expression of the correction coefficient H with respect to M(t) is:

[0015]

[0016] Step S4, deriving the expression of distance D according to the expressions in steps S1-S3:

[0017]

[0018] Thus, the distance D between the protection installation and the fault point is obtained.

[0019] A parallel double-circuit line protection system based on single-end transient quantity information, comprising:

[0020] The acquisition module samples the voltage and current waveforms of the busbar at both ends of the fault point of the current level line according to the mutual inductor to obtain the fault phase voltage of the fault circuit. Fault phase current of fault circuit Zero sequence current i LP0(t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t);

[0021] Calculation module, further calculates the transient quantity I(t) LP0 、I(t) LQ0 :

[0022]

[0023]

[0024] Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926;

[0025] The calculation module defines, for any single-phase grounding fault in a parallel double-circuit line, expression:

[0026]

[0027] Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1; Z0 is zero sequence impedance, Z0=R0+jX0; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 It is approximately equal to 0 and can be ignored; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point;

[0028] Define the intermediate quantity M(t), and The expression of M(t) is:

[0029]

[0030]

[0031] Among them, the expression of the correction coefficient H with respect to M(t) is:

[0032]

[0033] The expression of distance D is derived as:

[0034]

[0035] Thus, the distance D between the protection installation and the fault point is obtained.

[0036] It can be seen from the above technical scheme that the parallel double-circuit line protection method and system based on single-ended transient quantity information provided by the embodiment of the present invention collects the voltage and current waveforms of the busbars at both ends of the current level where the fault point is located by the mutual inductor, obtains the fault phase voltage of the fault circuit, the fault phase current of the fault circuit, the zero-sequence current, and the instantaneous value of the zero-sequence current of the adjacent non-fault circuit, and further calculates the transient quantity I(t) LP0 、I(t) LQ0 ; Establish an arbitrary single-phase ground fault model for parallel double-circuit lines and the intermediate quantity M(t), and The expression of M(t) with the correction coefficient H is used to further derive the distance D between the protection installation and the fault point. The present invention uses transient quantity information for calculation, and the data used is 1 / 4 cycle data. It only takes 4-5ms to accurately calculate the fault distance. The correction coefficient H is used to consider the influence of the sudden change before and after the fault, and the influence of the transient process can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of a parallel double-circuit line of the present invention. DETAILED DESCRIPTION

[0038] The technical scheme and technical effects of the present invention are further elaborated in detail below in conjunction with the accompanying drawings of the present invention.

[0039] refer to Figure 1 As shown, the present invention provides a parallel double-circuit line protection method based on single-ended transient quantity information, the steps comprising:

[0040] Step S1, sampling the voltage and current waveforms of the busbar at both ends of the current line where the fault point is located by the mutual inductor to obtain the fault phase voltage of the fault circuit Fault phase current of fault circuit Zero sequence current i LP0 (t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t), and further calculate the transient quantity I(t) LP0 、I(t) LQ0 :

[0041]

[0042] Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926;

[0043] Step S2: for any single-phase ground fault in a parallel double-circuit line, define expression:

[0044]

[0045] Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1; Z0 is zero sequence impedance, Z0=R0+jX0; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 It is approximately equal to 0, can be ignored, or can be directly taken as 0; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point;

[0046] Step S3, define the intermediate quantity M(t), and The expression of M(t) is:

[0047]

[0048] Among them, the expression of the correction coefficient H with respect to M(t) is:

[0049]

[0050] Step S4, deriving the expression of distance D according to the expressions in steps S1-S3:

[0051]

[0052] Thus, the distance D between the protection installation and the fault point is obtained.

[0053] The present invention also provides a parallel double-circuit line protection system based on single-end transient quantity information, comprising:

[0054] The acquisition module samples the voltage and current waveforms of the busbar at both ends of the fault point of the current level line according to the mutual inductor to obtain the fault phase voltage of the fault circuit. Fault phase current of fault circuit Zero sequence current i LP0 (t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t);

[0055] Calculation module, further calculates the transient quantity I(t) LP0 、I(t) LQ0 :

[0056]

[0057]

[0058] Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926;

[0059] The calculation module defines, for any single-phase grounding fault in a parallel double-circuit line, expression:

[0060]

[0061] Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1, R1 is positive sequence resistance; Z0 is zero sequence impedance, Z0=R0+jX0, R0 is zero sequence resistance; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 Approximately equal to 0, negligible; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance, ωL L0 =X L0 ; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point;

[0062] Define the intermediate quantity M(t), and The expression of M(t) is:

[0063]

[0064] Among them, the expression of the correction coefficient H with respect to M(t) is:

[0065]

[0066] The expression of distance D is derived as:

[0067]

[0068] Thus, the distance D between the protection installation and the fault point is obtained.

[0069] This patent uses transient quantity information for calculation, and the data used is 1 / 4 cycle data volume. It only takes 4-5ms to achieve accurate calculation of fault distance. This patent uses the correction coefficient H, taking into account the influence of sudden changes before and after the fault, effectively avoiding the influence of transient processes, and the calculation results are more accurate.

[0070] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A parallel double-circuit line protection method based on single-ended transient quantity information, characterized in that: include: Step S1, sampling the voltage and current waveforms of the busbar at both ends of the current line where the fault point is located by the mutual inductor to obtain the fault phase voltage of the fault circuit Fault phase current of fault circuit Zero sequence current i LP0 (t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t), and further calculate the transient quantity I(t) LP0 、I(t) LQ0 : Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926; Step S2: for any single-phase ground fault in a parallel double-circuit line, define expression: Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1, R1 is positive sequence resistance; Z0 is zero sequence impedance, Z0=R0+jX0, R0 is zero sequence resistance; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 Approximately equal to 0; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance, ωL L0 =X L0 ; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point; Step S3, define the intermediate quantity M(t), and The expression of M(t) is: Among them, the expression of the correction coefficient H with respect to M(t) is: Step S4, deriving the expression of distance D according to the expressions in steps S1-S3: Thus, the distance D between the protection installation and the fault point is obtained.

2. A parallel double-circuit line protection system based on single-ended transient quantity information, characterized in that: include: The acquisition module samples the voltage and current waveforms of the busbar at both ends of the fault point of the current level line according to the mutual inductor to obtain the fault phase voltage of the fault circuit. Fault phase current of fault circuit Zero sequence current i LP0 (t), instantaneous value of zero-sequence current i of adjacent non-fault circuit LQ0 (t); Calculation module, further calculates the transient quantity I(t) LP0 、I(t) LQ0 : Where P is the fault circuit in the parallel double-circuit line I / II, Q is the adjacent circuit of the fault phase in the parallel double-circuit line, is the fault phase, 0 represents zero sequence; t represents the sampling time; n and k represent the natural sequence, T represents the total number of sampling points within 20ms, k∈[1,T / 4]; e is a natural constant, π=3.1415926; The calculation module defines, for any single-phase grounding fault in a parallel double-circuit line, expression: Where 1 represents the positive sequence, K0 is the zero sequence current compensation coefficient, K0 = (Z0-Z1) / 3Z1, k = I LQ0 / I LP0 , Z is impedance, Z=R+jX, R is resistance, X is reactance; Z1 is positive sequence impedance, Z1=R1+jX1, R1 is positive sequence resistance; Z0 is zero sequence impedance, Z0=R0+jX0, R0 is zero sequence resistance; Z L0 is the zero-sequence impedance between the two circuits, Z L0 =R L0 +jX L0 , R L0 Approximately equal to 0; H is the correction coefficient; L1 is the positive sequence inductance, L0 is the zero sequence inductance, ωL L0 =X L0 ; △t is the time interval between adjacent sampling points; D represents the distance between the protection installation and the fault point; define the intermediate quantity M(t), and The expression of M(t) is: Among them, the expression of the correction coefficient H with respect to M(t) is: The expression of distance D is derived as: Thus, the distance D between the protection installation and the fault point is obtained.

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