CN106771877A - The determination method and apparatus of the position of failure point of system with non effectively earth ed neutral - Google Patents

Abstract

The present invention proposes a method and device for determining the location of a fault point in a neutral point non-effectively grounded system, wherein the determination method includes: determining whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system; If a single-phase ground fault occurs on the line, the circuit breaker that controls the line trips for the first time and then recloses; if the circuit breaker fails to reclose, it is determined that the line has a permanent fault; if the circuit breaker recloses successfully, it is determined that the line has a transient fault; When it is determined that the line has a permanent fault, control the circuit breaker to trip again; obtain the reclosing time of the circuit breaker and the arrival time of the reflected wave at the single-phase ground fault point of the line after the circuit breaker trips again; according to the reclosing time and the reflected wave Time of arrival to determine the location of the single-phase-to-earth fault point of the line. Through the technical scheme of the invention, the fault type can be determined, and when the fault type is a permanent fault, the fault location can be accurately detected.

Description

Method and device for determining fault point location of neutral point non-effectively grounded system

technical field

The present invention relates to the technical field of power systems, in particular to a method for determining the location of a fault point in a neutral point non-effectively grounded system and a device for determining the location of a fault point in a neutral point non-effectively grounded system.

Background technique

At present, the neutral point non-effectively grounded system is the main form of the domestic power distribution system. When this system is single-phase grounded, the line voltage remains unchanged, the grounded phase voltage decreases, and the non-grounded phase voltage increases. At the same time, because the system can only pass The ground capacitance forms a loop, and the ground capacitance capacitance is very large, resulting in a very small fault current, which brings great difficulties to protection and distance measurement.

When a single-phase ground fault occurs in a neutral point non-effectively grounded system, it will not affect the normal power supply to users, and will not pose a direct threat to the safe operation of the system. Therefore, single-phase ground faults in power distribution systems are also allowed in China's operating regulations It can continue to run for 2 hours after failure. At present, the domestic mainstream solution to the single-phase ground fault in the neutral point non-effectively grounded system is to select the fault line, and then give an alarm instead of tripping, and then manually trip and reclose to eliminate the instantaneous fault. However, most of the single-phase ground faults that occur on site are instantaneous faults. If there is protection, the fault can be eliminated automatically by tripping and reclosing; secondly, the long-term existence of this fault state may cause the grounding arc to continue to high temperature and cause the insulation of the wire Permanent damage becomes a permanent fault, and the non-ground phase voltage increases to accelerate insulation aging, which may cause single-phase ground faults to develop into phase-to-phase faults.

When a permanent fault occurs, it is necessary to manually go to the scene to troubleshoot the fault after the fault is located, so the accuracy of the fault location is very important. The bottleneck of distance measurement in the non-effective neutral point grounding system is mainly due to the complex structure of the power distribution system and the grounding method of the neutral point. Firstly, the power supply distance of power distribution lines is short, which requires high distance measurement accuracy; secondly, power distribution systems are mostly radial structures with many line branches, and there are special cases such as overhead-cable hybrid transmission mode and non-transposition. The unique structural characteristics of the line also increase the difficulty of distance measurement; finally, after a single-phase ground fault (accounting for 70%-80% of the total line faults) occurs in the neutral point non-effectively grounded system, because it does not constitute a short circuit circuit, the fault The current is very small, and the fault zero-sequence current is easily submerged in the zero-sequence current generated by the asymmetry of the distribution system line structure, which makes it very difficult to use power frequency single-phase grounding protection and distance measurement.

Therefore, when a single-phase ground fault occurs in a neutral point non-effectively grounded system, how to determine the type of fault and how to accurately determine the location of the fault point in the event of a permanent fault have become urgent problems to be solved.

Contents of the invention

Based on the above problems, the present invention proposes a new technical solution, which can accurately determine the fault type when a single-phase ground fault occurs in the neutral point non-effectively grounded system, and when the fault type is a permanent fault, also The fault location can be accurately detected.

In view of this, the first aspect of the present invention proposes a method for determining the location of a fault point in a neutral point non-effectively grounded system, including: determining whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system; If a single-phase ground fault occurs in the line, the circuit breaker controlling the line will be reclosed after tripping for the first time; if the circuit breaker fails to reclose, it will be determined that a permanent fault occurs in the line. , it is determined that a transient fault occurs in the line; when it is determined that a permanent fault occurs in the line, control the circuit breaker to trip again; obtain the reclosing time of the circuit breaker and the circuit breaker after tripping again The reflected wave arrival time of the single-phase ground fault point of the line; according to the reclosing time and the reflected wave arrival time, determine the position of the single-phase ground fault point of the line.

In this technical scheme, if a single-phase ground fault occurs in the line of the neutral point non-effectively grounded system, the circuit breaker will be reclosed after tripping. If the gate fails, there is a permanent fault on the line, and the circuit breaker is tripped again, and the position of the one-way ground fault point in the line is determined by the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave in the line after tripping again. Through the above scheme, even if the fault current is not obvious when a single-phase ground fault occurs in the neutral point non-effectively grounded system, the fault type can be accurately determined, and when the fault type is a permanent fault, the fault location can also be accurately detected.

In the above technical solution, preferably, the determination of whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system specifically includes: acquiring the sampled value of the zero-sequence voltage, the sampled value of the zero-sequence current and the zero-sequence current sampled value of the line Zero-sequence voltage effective value of the zero-sequence voltage sampling value; if the zero-sequence voltage effective value is greater than or equal to the preset voltage threshold, then wavelet transform is performed on the zero-sequence voltage sampling value and the zero-sequence current sampling value respectively , to obtain the zero-sequence voltage wavelet component and the zero-sequence current wavelet component; respectively calculate the wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component; according to the zero-sequence The wavelet modulus maximum value of the voltage wavelet component and the wavelet modulus maximum value of the zero-sequence current wavelet component determine the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current; according to the initial zero-sequence voltage The traveling wave polarity and the initial traveling wave polarity of the zero-sequence current determine whether a single-phase ground fault occurs in the line.

In this technical solution, when the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current are opposite, it is determined that a single-phase ground fault has occurred on the line, so as to accurately identify the single-phase ground fault, and then timely The single-phase ground fault can be handled in a timely manner to ensure the normal operation of the system and save the cost of system operation.

In any of the above technical solutions, preferably, a first preset formula is used to respectively perform wavelet transformation on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current, and the first preset formula is:

Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence.

In this technical solution, by using the first preset formula to perform wavelet transformation on the zero-sequence voltage sampled value and the zero-sequence current sampled value, it can ensure that the calculation of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component has the The same operation logic reduces calculation errors to improve the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and then ensures the efficient operation of the system.

In any of the above technical solutions, preferably, using a second preset formula to calculate the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component respectively, the second preset formula is :

Among them, if represents the zero-sequence voltage wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale.

In this technical solution, the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component are respectively calculated through the second preset formula above, which can ensure that the modulus of the zero-sequence voltage wavelet component The calculation of the modulus maximum value of the large value and the zero-sequence current wavelet component has the same operation logic, which reduces calculation errors, improves the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and thus ensures the efficient operation of the system sex.

In any of the above technical solutions, preferably, the determining the position of the single-phase ground fault point of the line according to the reclosing time and the arrival time of the reflected wave specifically includes: according to the reclosing time and The arrival time of the reflected wave, using the third preset formula to calculate the distance of the single-phase ground fault point of the line; according to the distance, determine the position of the single-phase ground fault point of the line, the third preset The formula is:

Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.

In this technical scheme, the single-phase ground fault point can be obtained by the half of the time difference between the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave of the line after the circuit breaker trips again, and the product of the line mode wave velocity to determine the location of the single-phase-to-ground fault point. In this way, after obtaining the location of the single-phase ground fault point, the maintenance efficiency of the line can be greatly improved, thereby ensuring the high efficiency of the system operation.

The second aspect of the present invention proposes a device for determining the location of a fault point in a neutral point non-effectively grounded system, including: a determination unit for determining whether a single-phase ground fault occurs in a line in a neutral point non-effectively grounded system; The control unit is configured to control the circuit breaker of the line to reclose after the first trip if the determination unit determines that a single-phase ground fault occurs in the line; the determination unit is also used to reclose if the circuit breaker fails to reclose , it is determined that a permanent fault occurs in the line, and if the circuit breaker recloses successfully, then it is determined that a transient fault occurs in the line; the control unit is also used for determining that a permanent fault occurs in the line , control the circuit breaker to trip again; the acquisition unit is used to obtain the reclosing time of the circuit breaker and the arrival time of the reflected wave of the single-phase ground fault point of the line after the circuit breaker trips again; the determination The unit is also used to determine the position of the single-phase ground fault point of the line according to the reclosing time and the arrival time of the reflected wave.

In this technical scheme, if a single-phase ground fault occurs in the line of the neutral point non-effectively grounded system, the circuit breaker will be reclosed after tripping. If the gate fails, there is a permanent fault on the line, and the circuit breaker is tripped again, and the position of the one-way ground fault point in the line is determined by the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave in the line after tripping again. Through the above scheme, even if the fault current is not obvious when a single-phase ground fault occurs in the neutral point non-effectively grounded system, the fault type can be accurately determined, and when the fault type is a permanent fault, the fault location can also be accurately detected.

In the above technical solution, preferably, the determination unit includes: an acquisition subunit, configured to acquire the sampled value of the zero-sequence voltage of the line, the sampled value of the zero-sequence current, and the effective zero-sequence voltage of the sampled value of the zero-sequence voltage value; the wavelet transform subunit is used to perform wavelet transform on the zero-sequence voltage sampled value and the zero-sequence current sampled value respectively to obtain zero-sequence Sequence voltage wavelet component and zero-sequence current wavelet component; calculation subunit, used to calculate respectively the wavelet modulus maximum value of the zero-sequence voltage wavelet component and the wavelet modulus maximum value of the zero-sequence current wavelet component; determine the subunit , used to determine the initial traveling wave polarity of the zero sequence voltage and the initial traveling wave polarity of the zero sequence current according to the wavelet modulus maxima of the zero sequence voltage wavelet component and the wavelet modulus maxima of the zero sequence current wavelet component The determination subunit is also used to determine whether a single-phase ground fault occurs on the line according to the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current.

In this technical solution, when the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current are opposite, it is determined that a single-phase ground fault has occurred on the line, so as to accurately identify the single-phase ground fault, and then timely The single-phase ground fault can be handled in a timely manner to ensure the normal operation of the system and save the cost of system operation.

In any of the above technical solutions, preferably, the wavelet transform subunit is specifically configured to perform wavelet transform on the zero-sequence voltage sampled value and the zero-sequence current sampled value respectively by using a first preset formula, so The first default formula mentioned above is:

Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence.

In this technical solution, by using the first preset formula to perform wavelet transformation on the zero-sequence voltage sampled value and the zero-sequence current sampled value, it can ensure that the calculation of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component has the The same operation logic reduces calculation errors to improve the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and then ensures the efficient operation of the system.

In any of the above technical solutions, preferably, the calculating subunit is specifically configured to use a second preset formula to calculate respectively the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component , the second preset formula is:

Among them, if represents the zero-sequence voltage wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale.

In this technical solution, the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component are respectively calculated through the second preset formula above, which can ensure that the modulus of the zero-sequence voltage wavelet component The calculation of the modulus maximum value of the large value and the zero-sequence current wavelet component has the same operation logic, which reduces calculation errors, improves the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and thus ensures the efficient operation of the system sex.

In any of the above technical solutions, preferably, the determining unit is specifically configured to use a third preset formula to calculate the single-phase-to-ground fault point of the line according to the reclosing time and the arrival time of the reflected wave Distance, according to the distance, determine the position of the single-phase ground fault point of the line, the third preset formula is:

Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.

In this technical scheme, the single-phase ground fault point can be obtained by the half of the time difference between the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave of the line after the circuit breaker trips again, and the product of the line mode wave velocity to determine the location of the single-phase-to-ground fault point. In this way, after obtaining the location of the single-phase ground fault point, the maintenance efficiency of the line can be greatly improved, thereby ensuring the high efficiency of the system operation.

Through the technical scheme of the invention, when a single-phase ground fault occurs in a neutral point non-effectively grounded system, the fault type can be determined, and when the fault type is a permanent fault, the fault location can be accurately detected.

Description of drawings

Fig. 1 shows a schematic flow chart of a method for determining the location of a fault point of a neutral point non-effectively grounded system according to an embodiment of the present invention;

FIG. 2 shows a schematic flowchart of a method for determining the location of a fault point in a neutral point non-effectively grounded system according to another embodiment of the present invention;

Fig. 3 shows a block diagram of a device for determining the location of a fault point in a neutral point non-effectively grounded system according to an embodiment of the present invention.

detailed description

In order to have a clearer understanding of the above objects, features and advantages of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the case of no conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described here. Therefore, the protection scope of the present invention is not limited by the specific details disclosed below. EXAMPLE LIMITATIONS.

Fig. 1 shows a schematic flowchart of a method for determining a fault point location of a neutral point non-effectively grounded system according to an embodiment of the present invention.

As shown in Figure 1, the method for determining the location of the fault point of the neutral point non-effectively grounded system according to an embodiment of the present invention includes:

Step S102, determining whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system.

Step S104, if a single-phase grounding fault occurs on the line, the circuit breaker controlling the line trips for the first time and then recloses.

Step S106, if the reclosing of the circuit breaker fails, it is determined that a permanent fault occurs in the line, and if the reclosing of the circuit breaker succeeds, it is determined that a transient fault occurs in the line.

Step S108, when it is determined that the line has a permanent fault, control the circuit breaker to trip again.

Step S110, obtaining the reclosing time of the circuit breaker and the arrival time of the reflected wave at the single-phase-to-ground fault point of the line after the circuit breaker trips again.

Step S112, according to the reclosing time and the arrival time of the reflected wave, determine the position of the single-phase-to-ground fault point of the line.

In this technical scheme, if a single-phase ground fault occurs in the line of the neutral point non-effectively grounded system, the circuit breaker will be reclosed after tripping. If the gate fails, there is a permanent fault on the line, and the circuit breaker is tripped again, and the position of the one-way ground fault point in the line is determined by the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave in the line after tripping again. Through the above scheme, even if the fault current is not obvious when a single-phase ground fault occurs in the neutral point non-effectively grounded system, the fault type can be accurately determined, and when the fault type is a permanent fault, the fault location can also be accurately detected.

In the above technical solution, preferably, step S102 specifically includes: obtaining the sampled value of the zero-sequence voltage of the line, the sampled value of the zero-sequence current, and the effective value of the zero-sequence voltage of the sampled value of the zero-sequence voltage; if the zero-sequence If the effective value of the voltage is greater than or equal to the preset voltage threshold, wavelet transform is performed on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current to obtain the wavelet component of the zero-sequence voltage and the wavelet component of the zero-sequence current; The wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component; according to the wavelet modulus maxima of the zero-sequence voltage wavelet component and the The wavelet modulus maximum value determines the initial traveling wave polarity of the zero sequence voltage and the initial traveling wave polarity of the zero sequence current; according to the initial traveling wave polarity of the zero sequence voltage and the initial traveling wave polarity of the zero sequence current, determine the Whether a single-phase ground fault occurs on the above line.

In this technical solution, when the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current are opposite, it is determined that a single-phase ground fault has occurred on the line, so as to accurately identify the single-phase ground fault, and then timely The single-phase ground fault can be handled in a timely manner to ensure the normal operation of the system and save the cost of system operation.

In any of the above technical solutions, preferably, a first preset formula is used to respectively perform wavelet transformation on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current, and the first preset formula is:

Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence.

For example, {h _k1 } _k1 = {0.125,0.375,0.375,0.125}, (k1=-1,0,1,2),

{g _k2 } _k2 = {-2, -2}, (k2 = 0, 1), j = 1, 2, 3 or 4.

In this technical solution, by using the first preset formula to perform wavelet transformation on the zero-sequence voltage sampled value and the zero-sequence current sampled value, it can ensure that the calculation of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component has the The same operation logic reduces calculation errors to improve the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and then ensures the efficient operation of the system.

In any of the above technical solutions, preferably, using a second preset formula to calculate the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component respectively, the second preset formula is :

Among them, if represents the zero-sequence voltage wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale.

In this technical solution, the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component are respectively calculated through the second preset formula above, which can ensure that the modulus of the zero-sequence voltage wavelet component The calculation of the modulus maximum value of the large value and the zero-sequence current wavelet component has the same operation logic, which reduces calculation errors, improves the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and thus ensures the efficient operation of the system sex.

In any of the above technical solutions, preferably, step S112 specifically includes: according to the reclosing time and the arrival time of the reflected wave, using a third preset formula to calculate the distance of the single-phase-to-ground fault point of the line; The distance determines the position of the single-phase ground fault point of the line, and the third preset formula is:

Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.

In this technical scheme, the single-phase ground fault point can be obtained by the half of the time difference between the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave of the line after the circuit breaker trips again, and the product of the line mode wave velocity to determine the location of the single-phase-to-ground fault point. In this way, after obtaining the location of the single-phase ground fault point, the maintenance efficiency of the line can be greatly improved, thereby ensuring the high efficiency of the system operation.

Fig. 2 shows a schematic flowchart of a method for determining a fault point location of a neutral point non-effectively grounded system according to another embodiment of the present invention.

As shown in Figure 2, according to another embodiment of the present invention, the method for determining the location of the fault point of the neutral point non-effectively grounded system includes:

Step S202, acquiring sampled values of zero-sequence voltage and zero-sequence current, and calculating an effective value U0 of zero-sequence voltage. Specifically, an effective value U0 of the zero-sequence voltage is obtained by performing FFT (Fast Fourier Transformation, Fast Fourier Transformation) on the sampled value of the zero-sequence voltage.

Step S204, judging whether U0<U0set is satisfied, if the judging result is yes, go to step S214, and if the judging result is no, go to step S216.

Step S206, performing binary discrete wavelet transform on the sampled values of the zero-sequence voltage and the sampled values of the zero-sequence current to obtain wavelet components of the zero-sequence voltage and zero-sequence current. Among them, the derivative function of the cubic central B-spline function is used as the wavelet function.

Step S208, calculating the wavelet modulus maxima for the zero-sequence voltage wavelet component and the zero-sequence current wavelet component.

Step S210, according to the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component, determine the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current.

Step S212, judging whether the initial traveling wave polarity of the zero-sequence voltage and zero-sequence current are the same, if the judging result is yes, go to step S214, and if the judging result is no, go to step S216.

Step S214, the protection resets.

In step S216, it is determined that it is a single-phase ground fault, and a signal is sent to trip the circuit breaker.

Step S218, delay for 1s-2s.

Step S220, reclosing, and recording the reclosing time t1, delay time.

Step S222, judging whether the reclosing is successful, if the reclosing is successful, execute step S224, and if the reclosing fails, execute step S226.

Step S224, judging that it is a transient fault.

In step S226, it is judged to be a permanent fault, and tripped again.

Step S228, acquiring the traveling wave of the line-mode current between reclosing and reclosing, so as to record the arrival time t2 of the reflected wave at the fault point.

Step S230, through the formula Calculate the distance to the fault point. Among them, D represents the distance of the fault point, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.

Fig. 3 shows a block diagram of a device for determining the location of a fault point in a neutral point non-effectively grounded system according to an embodiment of the present invention.

As shown in FIG. 3 , the device 300 for determining the location of a fault point of a neutral point non-effectively grounded system according to an embodiment of the present invention includes: a determination unit 302 , a control unit 304 and an acquisition unit 306 .

The determining unit 302 is configured to determine whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system; the control unit 304 is configured to control the The circuit breaker of the line recloses after tripping for the first time; the determination unit 302 is also used to determine that a permanent fault has occurred on the line if the reclosing of the circuit breaker fails, and determine that the circuit breaker recloses successfully. The circuit breaker has a transient fault; the control unit 304 is also used to control the circuit breaker to trip again when it is determined that the circuit breaker has a permanent fault; the obtaining unit 306 is used to obtain the reclosing of the circuit breaker Gate time and the reflected wave arrival time of the single-phase ground fault point of the line after the circuit breaker trips again; the determination unit 302 is also used to determine according to the reclosing time and the reflected wave arrival time The location of the single-phase-to-earth fault point of the line in question.

In this technical scheme, if a single-phase ground fault occurs in the line of the neutral point non-effectively grounded system, the circuit breaker will be reclosed after tripping. If the gate fails, there is a permanent fault on the line, and the circuit breaker is tripped again, and the position of the one-way ground fault point in the line is determined by the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave in the line after tripping again. Through the above scheme, even if the fault current is not obvious when a single-phase ground fault occurs in the neutral point non-effectively grounded system, the fault type can be accurately determined, and when the fault type is a permanent fault, the fault location can also be accurately detected.

In the above technical solution, preferably, the determination unit 302 includes: an acquisition subunit 3022, configured to acquire the sampled value of the zero-sequence voltage of the line, the sampled value of the zero-sequence current, and the zero-sequence value of the sampled value of the zero-sequence voltage voltage effective value; wavelet transform subunit 3024, used to perform wavelet transform on the zero sequence voltage sampled value and the zero sequence current sampled value respectively if the zero sequence voltage effective value is greater than or equal to a preset voltage threshold, To obtain the zero-sequence voltage wavelet component and the zero-sequence current wavelet component; the calculation subunit 3026 is used to calculate the wavelet modulus maximum value of the zero-sequence voltage wavelet component and the wavelet modulus maximum value of the zero-sequence current wavelet component respectively ; Determining subunit 3028, used to determine the initial traveling wave polarity and zero-sequence current of zero-sequence voltage according to the wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component Initial traveling wave polarity: the determination subunit 3028 is also used to determine whether a single-phase ground fault occurs on the line according to the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current.

In this technical solution, when the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current are opposite, it is determined that a single-phase ground fault has occurred on the line, so as to accurately identify the single-phase ground fault, and then timely The single-phase ground fault can be handled in a timely manner to ensure the normal operation of the system and save the cost of system operation.

In any of the above technical solutions, preferably, the wavelet transform subunit 3024 is specifically configured to perform wavelet transform on the zero-sequence voltage sampled value and the zero-sequence current sampled value respectively by using a first preset formula, The first preset formula is:

Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence.

In this technical solution, by using the first preset formula to perform wavelet transformation on the zero-sequence voltage sampled value and the zero-sequence current sampled value, it can ensure that the calculation of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component has the The same operation logic reduces calculation errors to improve the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and then ensures the efficient operation of the system.

In any of the above technical solutions, preferably, the calculating subunit 3026 is specifically configured to calculate the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component respectively by using a second preset formula value, the second preset formula is:

Among them, if represents the zero-sequence voltage wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale.

In this technical solution, the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component are respectively calculated through the second preset formula above, which can ensure that the modulus of the zero-sequence voltage wavelet component The calculation of the modulus maximum value of the large value and the zero-sequence current wavelet component has the same operation logic, which reduces calculation errors, improves the judgment accuracy of whether a single-phase ground fault occurs, improves the maintenance efficiency of the line, and thus ensures the efficient operation of the system sex.

In any of the above technical solutions, preferably, the determining unit 302 is specifically configured to use a third preset formula to calculate the single-phase ground fault point of the line according to the reclosing time and the arrival time of the reflected wave According to the distance, the position of the single-phase ground fault point of the line is determined, and the third preset formula is:

Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.

In this technical scheme, the single-phase grounding fault point can be obtained by the half of the time difference between the reclosing time of the circuit breaker and the arrival time of the reflected traveling wave of the line after the circuit breaker trips again, and the product of the line mode wave velocity to determine the location of the single-phase-to-ground fault point. In this way, after obtaining the location of the single-phase ground fault point, the maintenance efficiency of the line can be greatly improved, thereby ensuring the high efficiency of the system operation.

The technical solution of the present invention has been described in detail above in conjunction with the accompanying drawings. Through the technical solution of the present invention, when a single-phase ground fault occurs in a neutral point non-effectively grounded system, the fault type can be determined, and when the fault type is a permanent fault, It is also possible to accurately detect the fault location.

In the present invention, the terms "first" and "second" are only used for the purpose of description, and should not be understood as indicating or implying relative importance; the term "plurality" means two or more. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A method for determining the location of the fault point of a neutral point non-effectively grounded system, characterized in that it comprises: Determine whether a single-phase ground fault occurs in a line in a neutral point non-effectively grounded system; If a single-phase ground fault occurs in the line, the circuit breaker controlling the line will be reclosed after the first trip; If the reclosing of the circuit breaker fails, it is determined that a permanent fault occurs in the circuit, and if the reclosing of the circuit breaker succeeds, it is determined that a transient fault occurs in the circuit; When it is determined that a permanent fault occurs in the line, controlling the circuit breaker to trip again; Obtaining the reclosing time of the circuit breaker and the arrival time of the reflected wave at the single-phase ground fault point of the line after the circuit breaker trips again; According to the reclosing time and the arrival time of the reflected wave, the position of the single-phase ground fault point of the line is determined. 2. The method for determining the location of the fault point of the neutral point non-effectively grounded system according to claim 1, wherein the determination of whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system specifically includes : Acquiring the sampled value of zero-sequence voltage, the sampled value of zero-sequence current and the effective value of zero-sequence voltage of the sampled value of zero-sequence voltage of the line; If the effective value of the zero-sequence voltage is greater than or equal to the preset voltage threshold, wavelet transform is performed on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current to obtain the wavelet component of the zero-sequence voltage and the wavelet of the zero-sequence current weight; respectively calculating the wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component; According to the wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component, determine the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current; According to the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current, it is determined whether a single-phase ground fault occurs on the line. 3. the method for determining the fault point position of the neutral point non-effectively grounded system according to claim 2, is characterized in that, Using a first preset formula, respectively performing wavelet transformation on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current, The first preset formula is: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; W</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; ,</span>$ Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence. 4. the method for determining the fault point position of the neutral point non-effectively grounded system according to claim 3, is characterized in that, using a second preset formula to calculate respectively the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component, The second preset formula is: Among them, if represents the zero-sequence voltage wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale. 5. The method for determining the position of the fault point of the neutral point non-effectively grounded system according to any one of claims 1 to 4, wherein, according to the reclosing time and the arrival time of the reflected wave, Determine the location of the single-phase-to-earth fault point of the line, including: According to the reclosing time and the arrival time of the reflected wave, using a third preset formula to calculate the distance of the single-phase ground fault point of the line; According to the distance, determine the position of the single-phase ground fault point of the line, The third preset formula is: $\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>$ Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity. 6. A device for determining the location of a fault point of a neutral point non-effectively grounded system, characterized in that it comprises: The determination unit is used to determine whether a single-phase ground fault occurs in the line in the neutral point non-effectively grounded system; A control unit, configured to control the circuit breaker of the line to reclose after the first trip if the determining unit determines that a single-phase ground fault occurs in the line; The determining unit is further configured to, if the reclosing of the circuit breaker fails, determine that a permanent fault occurs in the line, and if the reclosing of the circuit breaker succeeds, determine that a transient fault occurs in the line; The control unit is also used to control the circuit breaker to trip again when it is determined that the line has a permanent fault; An acquisition unit, configured to acquire the reclosing time of the circuit breaker and the arrival time of the reflected wave at the single-phase ground fault point of the line after the circuit breaker trips again; The determining unit is further configured to determine the position of the single-phase-to-ground fault point of the line according to the reclosing time and the arrival time of the reflected wave. 7. The device for determining the location of the fault point of the neutral point non-effectively grounded system according to claim 6, wherein the determining unit comprises: An acquisition subunit, configured to acquire the sampled value of the zero-sequence voltage, the sampled value of the zero-sequence current of the line, and the effective value of the zero-sequence voltage of the sampled value of the zero-sequence voltage; A wavelet transform subunit, configured to perform wavelet transform on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current respectively to obtain the zero-sequence voltage if the effective value of the zero-sequence voltage is greater than or equal to a preset voltage threshold Wavelet component and zero-sequence current wavelet component; A calculating subunit, configured to calculate the wavelet modulus maxima of the zero-sequence voltage wavelet component and the wavelet modulus maxima of the zero-sequence current wavelet component, respectively; The determining subunit is used to determine the initial traveling wave polarity of the zero-sequence voltage and the initial row of the zero-sequence current wave polarity; The determining subunit is further configured to determine whether a single-phase ground fault occurs on the line according to the initial traveling wave polarity of the zero-sequence voltage and the initial traveling wave polarity of the zero-sequence current. 8. The device for determining the location of the fault point of the neutral point non-effectively grounded system according to claim 7, wherein the wavelet transform subunit is specifically used for: Using a first preset formula, respectively performing wavelet transformation on the sampled value of the zero-sequence voltage and the sampled value of the zero-sequence current, The first preset formula is: $\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; W</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; k</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; ,</span>$ Wherein, X(n) represents the sampled value of the zero-sequence voltage or the sampled value of the zero-sequence current, if X(n) represents the sampled value of the zero-sequence voltage, then Indicates the zero-sequence voltage approximation component, Represents the wavelet component of the zero-sequence voltage, if X(n) represents the sampling value of the zero-sequence current, then Indicates the zero-sequence current approximation component, represents the zero-sequence current wavelet component, j represents the scale value, h _k1 represents the value corresponding to k1 in the first wavelet coefficient sequence, and h _k2 represents the value corresponding to k2 in the second wavelet coefficient sequence. 9. The device for determining the position of the fault point of the neutral point non-effectively grounded system according to claim 8, wherein the calculation subunit is specifically used for: using a second preset formula to calculate respectively the wavelet modulus maxima of the zero-sequence voltage wavelet component and the zero-sequence current wavelet component, The second preset formula is: Among them, if Represents the zero-sequence voltage wavelet component of the kth point data of the jth scale, then Indicates the wavelet modulus maximum value of the zero-sequence voltage wavelet component of the j-th scale, if represents the zero-sequence current wavelet component of the k-th point of the j-th scale, then Indicates the wavelet modulus maximum value of the zero-sequence current wavelet component of the j-th scale. 10. The device for determining the location of a fault point of a neutral point non-effectively grounded system according to any one of claims 6 to 9, wherein the determining unit is specifically used for: According to the reclosing time and the arrival time of the reflected wave, use a third preset formula to calculate the distance of the single-phase ground fault point of the line, and determine the position of the single-phase ground fault point of the line according to the distance , The third preset formula is: $\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; V</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; ,</span>$ Wherein, D represents the distance, t1 represents the reclosing time, t2 represents the arrival time of the reflected wave, and V represents the linear mode wave velocity.