A method and device for identifying power system line faults

Abstract

This invention provides a method and apparatus for identifying faults in power system lines. The method includes acquiring the three-phase instantaneous currents of a simulated line and the difference between any two of the three-phase instantaneous currents; determining a fault identification preset value based on the three-phase instantaneous currents of the simulated line and the difference between any two of the three-phase instantaneous currents; comparing the three-phase instantaneous currents of the line to be identified and the difference between any two of the three-phase instantaneous currents with the corresponding fault identification preset value to achieve fault identification of the line to be identified. Compared with simply using instantaneous current value as the fault identification criterion, this invention uses the two-phase current difference and the three-phase instantaneous current value as the fault identification criterion, resulting in faster identification speed. The identification method does not introduce criteria such as current slope or curvature, and the identification result is less affected by harmonic interference. It does not contain complex algorithms, is simple to calculate, and is easy to implement in engineering.

Description

Technical Field

[0001] The present invention belongs to the field of power system fault identification, and in particular relates to a power system line fault identification method and device. Background Art

[0002] With the continuous development of modern power systems, the short-circuit current level in power grids at all levels continues to grow. Line short circuits may cause serious harm and even exceed the interrupting capacity of circuit breakers, resulting in unimaginable consequences. Although traditional current limiting technologies such as increasing voltage levels and using series reactance can suppress the short-circuit current of the system to a certain extent, they will have a negative impact on the normal operation of the system. The use of fault current limiters has become a new way to solve the problem of excessive short-circuit currents. Its characteristics are that it presents zero impedance or low impedance when the power grid is operating normally, and the impedance increases rapidly when a short-circuit fault occurs in the power grid, achieving the purpose of quickly limiting the short-circuit current. After a short-circuit fault occurs, in order to limit the short-circuit current, the fault current limiter needs to be put into use in the shortest possible time, so quickly and accurately identifying short-circuit faults is one of the key factors in the effectiveness of the use of fault current limiters.

[0003] According to the requirements of the power system for fault current limiters, when a single-phase fault occurs in the line, the fault phase current limiter must be activated, and the non-fault phase current limiter cannot be activated; when a multi-phase fault occurs in the line, the three-phase current limiter must be activated. Therefore, the fault signal rapid identification method needs to accurately and quickly determine whether the line fault occurs and whether a phase is a non-fault phase of a single-phase fault. At present, there are many studies on the rapid identification technology of fault signals of fault current limiters at home and abroad: using the instantaneous value of current for identification is the most commonly used method, but the identification speed is not fast enough; using the current slope or waveform curvature for identification is fast, but it is greatly affected by harmonics, and filters need to be configured, and the calculation is more complicated; the current definite integral has strong anti-interference, and the harmonic components in the line current have little effect on it, but the identification is fast and slow, which can be used as a backup identification method. Although there are many methods for rapid identification of fault current, how to quickly, accurately and reliably identify fault current is still a problem that needs extensive and in-depth research. Summary of the invention

[0004] The present invention provides a method and device for identifying line faults in a power system, the purpose of which is to judge the fault condition of the line according to the difference between two-phase instantaneous currents and three-phase instantaneous current values.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a method for identifying a power system line fault, wherein the method comprises:

[0007] Obtain the three-phase instantaneous current of the simulated line and the difference between any two phases of the three-phase instantaneous current;

[0008] Determining a fault identification preset value according to the three-phase instantaneous current of the simulated circuit and the difference between any two-phase instantaneous currents of the three-phase instantaneous current;

[0009] The three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases of the three-phase instantaneous current are respectively compared with corresponding fault identification preset values ​​to realize fault identification of the line to be identified.

[0010] Preferably, determining the fault identification preset value according to the three-phase instantaneous current of the simulated circuit and the difference between any two-phase instantaneous currents of the three-phase instantaneous current comprises:

[0011] Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit;

[0012] The second fault identification preset value is determined according to the difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit.

[0013] Furthermore, the first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line.

[0014] Furthermore, the second fault identification preset value is the maximum value of the following values:

[0015] When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line;

[0016] When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between two phases of the three phases of the simulated line;

[0017] When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between two phases of the three-phase line is simulated.

[0018] Preferably, the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of two phases in the three-phase instantaneous current are respectively compared with corresponding fault identification preset values ​​to realize the identification of the fault condition of the line to be identified.

[0019] When any of the following conditions is met, it is determined that the line to be identified has a fault:

[0020] The instantaneous current of the phase of the line to be identified is greater than the first fault identification preset value;

[0021] The difference between the instantaneous current of the phase of the circuit to be identified and the instantaneous currents of the other two phases is greater than the second fault identification preset value;

[0022] The instantaneous currents of the other two phases of the line to be identified are both greater than the first fault identification preset value;

[0023] The instantaneous current difference between the phase and another phase of the line to be identified is greater than the second fault identification preset value and the instantaneous current of the third phase is greater than the first fault identification preset value;

[0024] The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases.

[0025] The present invention provides a power system line fault identification device, the improvement of which lies in that the device comprises:

[0026] A preset value determination module, used to obtain the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current, and determine the fault identification preset value according to the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current;

[0027] The fault identification module is used to compare the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified.

[0028] Preferably, the preset value determination module is used for:

[0029] Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit;

[0030] The second fault identification preset value is determined according to the difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit.

[0031] Furthermore, the first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line.

[0032] Furthermore, the second fault identification preset value is the maximum value of the following values:

[0033] When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line;

[0034] When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between two phases of the three phases of the simulated line;

[0035] When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between two phases of the three-phase line is simulated.

[0036] Preferably, the fault identification module is used to determine that a fault occurs in the line to be identified when the following conditions are met:

[0037] The instantaneous current of the phase of the line to be identified is greater than the first fault identification preset value;

[0038] The difference between the instantaneous current of the phase of the circuit to be identified and the instantaneous currents of the other two phases is greater than the second fault identification preset value;

[0039] The instantaneous currents of the other two phases of the line to be identified are both greater than the first fault identification preset value;

[0040] The instantaneous current difference between the phase and another phase of the line to be identified is greater than the second fault identification preset value and the instantaneous current of the third phase is greater than the first fault identification preset value;

[0041] The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases.

[0042] Compared with the closest prior art, the technical solution provided by the present invention has the following excellent effects:

[0043] The present invention provides a method and device for identifying faults in power system lines. The method compares the three-phase instantaneous current of the line to be identified and the difference between the two-phase instantaneous currents in the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified. The two-phase current difference and the three-phase instantaneous current value are used as fault identification criteria, and the identification speed is faster than that of simply using the instantaneous current value as a criterion. The method does not introduce criteria such as current slope and curvature, and the identification result is less affected by harmonic interference. It does not contain complex algorithms, the calculation is simple, and it is convenient for engineering implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a flow chart of the line fault identification method of the present invention;

[0045] Figure 2 is a diagram of a simulation circuit structure of an embodiment of the present invention;

[0046] Figure 3 It is a structural diagram of the line fault identification device of the present invention. DETAILED DESCRIPTION

[0047] The invention will be further described in detail below in conjunction with the embodiments.

[0048] like Figure 1 As shown, the present invention provides a method for identifying a power system line fault, the method comprising:

[0049] Step 1, obtaining the three-phase instantaneous current of the simulation line and the difference between any two phase instantaneous currents of the three-phase instantaneous current;

[0050] Step 2: determining a fault identification preset value according to the three-phase instantaneous current of the simulated circuit and the difference between any two-phase instantaneous currents of the three-phase instantaneous current;

[0051] Step 3: compare the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases of the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified.

[0052] In the line fault identification method, step 1 is specifically:

[0053] like Figure 2 The circuit structure diagram of the embodiment of the present invention is shown in FIG. a 、e b 、e c and e′ a , e′ b , e′ c is a three-phase power supply, R+R′ and L+L′ are the resistance and inductance of each phase respectively, i a 、i b and i c They are three-phase currents, Figure 2 The three-phase instantaneous current of the simulated line and the difference between any two phases of the three-phase instantaneous current are obtained.

[0054] Specifically in step 2:

[0055] Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit;

[0056] The second fault identification preset value is determined according to the difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit.

[0057] Wherein, the first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line;

[0058] The second fault identification preset value is the maximum value of the following values:

[0059] When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line;

[0060] When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between two phases of the three phases of the simulated line;

[0061] When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between two phases of the three-phase line is simulated.

[0062] The fault identification principle of the present invention is:

[0063] The three-phase currents are i a、i b and i c , when a short circuit occurs in phase A, according to the superposition principle, there is i a =i a0 +i a1 、i b =i b0 +i b1 and i c =i c0 +i c1 , where i a0 、i b0 and i c0 are the three-phase currents when the system is running stably, i a1 、i b1 and i c1 They are respectively the three-phase short-circuit current components superimposed after a single-phase grounding fault.

[0064] Due to the symmetry of the three-phase power system, after a single-phase fault occurs in phase A, the superimposed short-circuit currents of phases B and C are equal, that is, i b1 =i c1 , at this time, the difference between phase B and phase C current is

[0065]

[0066] Where I is the effective value of the three-phase current when the system is running stably, ω is the angular frequency of the system operation, is the initial phase of phase A current.

[0067] It can be seen that when a single-phase ground short circuit fault occurs in phase A under the condition of three-phase symmetry, although the short circuit current is superimposed on the current of phases B and C, the current difference between the two will not be affected and will still maintain a standard sine wave. For the current difference between the faulty phase and the non-faulty phase in a single-phase fault, and the current difference between the two phases in a multi-phase fault, the peak value will be greater than the peak value during steady-state operation. Therefore, the two-phase current difference can be used to judge the fault condition of the power system.

[0068] Step 3 is as follows:

[0069] The fault condition of the line to be identified is judged based on the comparison result of the three-phase instantaneous current of the line to be identified with the first fault identification preset value and / or the comparison result of the difference between any two phase instantaneous currents of the three-phase instantaneous current of the line to be identified and the second fault identification preset value.

[0070] The specific identification method in step 3 includes:

[0071] When any of the following conditions is met, it is determined that the line to be identified has a fault:

[0072] The instantaneous current of the phase of the line to be identified is greater than the first fault identification preset value;

[0073] The difference between the instantaneous current of the phase of the circuit to be identified and the instantaneous currents of the other two phases is greater than the second fault identification preset value;

[0074] The instantaneous currents of the other two phases of the line to be identified are both greater than the first fault identification preset value;

[0075] The instantaneous current difference between the phase and another phase of the line to be identified is greater than the second fault identification preset value and the instantaneous current of the third phase is greater than the first fault identification preset value;

[0076] The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases.

[0077] The present invention provides a specific embodiment according to the above technical solution (for phase A in a three-phase circuit):

[0078] The first fault identification preset value I set1 Set to simulate the instantaneous maximum current of the two non-fault phases when a single-phase fault occurs in the line; set the second fault identification preset value I set2 It is set to the maximum value of the instantaneous current difference between two non-fault phases when a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two phases in three phases when the simulated line carries the maximum load, and the maximum value of the instantaneous current difference between two phases in three phases of the line when the circuit breaker outside the line is actuated.

[0079] Judgment methods include:

[0080] When the following conditions are met, a multi-phase fault or a phase A single-phase grounding fault occurs in the line to be identified:

[0081] |i a |>I set1 ;

[0082] |i a -i b |>I set2 and|i c -i a |>I set2 ;

[0083] When any of the following conditions is met, it is determined that a multi-phase fault occurs in the line to be identified:

[0084] |i b |>I set1 and|i c |>I set1 ;

[0085] |i b |>I set1 and|ic -i a |>I set2 , or |i c |>I set1 and|i a -i b |>I set2 ;

[0086] If any one of the above four conditions is met, it can be determined that a single-phase grounding fault occurs in phase A of the line, or two phases of ABC fail, or all three phases ABC fail.

[0087] like Figure 3 As shown, the present invention provides a power system line fault identification device, the device comprising:

[0088] A preset value determination module, used to obtain the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current, and determine the fault identification preset value according to the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current;

[0089] The fault identification module is used to compare the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified.

[0090] The preset value determination module in the device is used to:

[0091] Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit;

[0092] The second fault identification preset value is determined according to the difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit.

[0093] Wherein, the first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line;

[0094] The second fault identification preset value is the maximum value of the following values:

[0095] When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line;

[0096] When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between two phases of the three phases of the simulated line;

[0097] When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between two phases of the three-phase line is simulated.

[0098] The fault identification module in the device is specifically used for:

[0099] The fault condition of the line to be identified is judged based on the comparison result of the three-phase instantaneous current of the line to be identified with the first fault identification preset value and / or the comparison result of the difference between any two phase instantaneous currents of the three-phase instantaneous current of the line to be identified and the second fault identification preset value.

[0100] The fault identification module identifies that a line fault occurs when any of the following conditions is met:

[0101] The instantaneous current of the phase of the line to be identified is greater than the first fault identification preset value;

[0102] The difference between the instantaneous current of the phase of the circuit to be identified and the instantaneous currents of the other two phases is greater than the second fault identification preset value;

[0103] The instantaneous currents of the other two phases of the line to be identified are both greater than the first fault identification preset value;

[0104] The instantaneous current difference between the phase and another phase of the line to be identified is greater than the second fault identification preset value and the instantaneous current of the third phase is greater than the first fault identification preset value;

[0105] The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases.

[0106] In summary, the present invention provides a method and device for identifying line faults in a power system, which compares the three-phase instantaneous current of the line to be identified and the difference between the two-phase instantaneous currents in the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified; using the two-phase current difference and the three-phase instantaneous current value as fault identification criteria has a faster identification speed than simply using the instantaneous current value criterion; the method does not introduce criteria such as current slope and curvature, and is less affected by harmonic interference; it does not contain complex algorithms, the calculation is simple, and it is convenient for engineering implementation.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although ordinary technicians in the relevant field refer to the above embodiments, they should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for identifying power system line faults, characterized in that: The method comprises: Obtain the three-phase instantaneous current of the simulated line and the difference between any two phases of the three-phase instantaneous current; Determining a fault identification preset value according to the three-phase instantaneous current of the simulated circuit and the difference between any two-phase instantaneous currents of the three-phase instantaneous current; Comparing the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases of the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified; The determining of the fault identification preset value according to the three-phase instantaneous current of the simulated circuit and the difference between any two-phase instantaneous currents of the three-phase instantaneous currents comprises: Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit; Determining a second fault identification preset value according to a difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit; The step of comparing the three-phase instantaneous current of the line to be identified and the difference between the two-phase instantaneous current of the three-phase instantaneous current with the corresponding fault identification preset values ​​to identify the fault condition of the line to be identified includes: When the following conditions are met, it is determined that the line to be identified has a fault: The instantaneous current difference between one phase of the circuit to be identified and one of the other two phases is greater than the second fault identification preset value and the instantaneous current of the other phase of the other two phases is greater than the first fault identification preset value; The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases; The first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line; The second fault identification preset value is the maximum value of the following values: When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line; When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between any two phases of the three phases of the simulated line; When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between any two phases of the three-phase simulated line is obtained.

2. A power system line fault identification device, characterized in that: The device comprises: A preset value determination module, used to obtain the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current, and determine the fault identification preset value according to the three-phase instantaneous current of the simulated line and the difference between the instantaneous currents of any two phases in the three-phase instantaneous current; A fault identification module, used for comparing the three-phase instantaneous current of the line to be identified and the difference between the instantaneous currents of any two phases of the three-phase instantaneous current with the corresponding fault identification preset values, so as to realize fault identification of the line to be identified; The preset value determination module is used for: Determining a first fault identification preset value according to the three-phase instantaneous current of the simulated circuit; Determining a second fault identification preset value according to a difference between any two-phase instantaneous currents of the three-phase instantaneous currents of the simulated circuit; The fault identification module is used to identify the fault condition of the line: When the following conditions are met, it is determined that the line to be identified has a fault: The instantaneous current difference between the phase and another phase of the line to be identified is greater than the second fault identification preset value and the instantaneous current of the third phase is greater than the first fault identification preset value; The fault of the line to be identified includes a single-phase fault of the phase, a fault of two phases among three phases, or a fault of all three phases; The first fault identification preset value is the instantaneous current peak value of the non-fault phase when a single-phase fault occurs in the simulated line; The second fault identification preset value is the maximum value of the following values: When a single-phase fault occurs in the simulated line, the maximum value of the instantaneous current difference between two non-fault phases in the simulated line; When the simulated line carries the maximum load, the maximum value of the instantaneous current difference between any two phases of the three phases of the simulated line; When the external circuit breaker of the simulated line is actuated, the maximum value of the instantaneous current difference between any two phases of the three-phase simulated line is obtained.

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