Grounding system high-resistance grounding protection method, device, equipment and readable storage medium

Abstract

The present application provides a method, apparatus, device and readable storage medium for high-resistance grounding protection of a grounding system. The present application can use the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line to determine the zero-sequence admittance of the feeder to be tested, thereby judging whether a line fault occurs based on the phase range of the zero-sequence admittance of the feeder to be tested. The zero-sequence current information of a single feeder is used as the basis for judgment. The high-resistance grounding fault identification sensitivity is high and the fault identification is accurate. The present application can provide a protection strategy for single-phase high-resistance grounding faults in a low-resistance grounding system with a high transition resistance tolerance.

Description

Technical Field

[0001] The present application relates to the technical field of distribution network fault identification, and in particular to a method, device, equipment and readable storage medium for high-resistance grounding protection of a grounding system. Background Art

[0002] With the development of distribution network technology, distribution networks with low-resistance grounding at the neutral point need to be equipped with zero-sequence overcurrent protection. Generally, when determining the zero-sequence overcurrent protection action setting value, it is necessary to consider the impact of the capacitive current of the protected line and the maximum unbalanced current during normal operation. Therefore, the action setting value of the zero-sequence overcurrent protection is usually too high. However, when a high-resistance grounding fault occurs in a distribution network system with low-resistance grounding, the fault current is usually relatively small. If the zero-sequence overcurrent protection action setting value is set too high, conventional protection will have difficulty identifying the high-resistance grounding fault. Although high-resistance faults do not affect the system's normal power supply to the load, they can easily cause electric shock and electrical fire accidents. Therefore, it is of great significance to quickly and reliably detect high-resistance grounding faults in distribution networks with low-resistance grounding at the neutral point. Summary of the Invention

[0003] The present application aims to solve at least one of the above-mentioned technical defects. In view of this, the present application provides a high-resistance grounding protection method, device, equipment and readable storage medium for a grounding system, which are used to solve the technical defect of difficulty in identifying high-resistance grounding faults in the grounding system in the prior art.

[0004] A high-resistance grounding protection method for a grounding system, comprising:

[0005] Real-time measurement of the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested;

[0006] Determining whether the first zero-sequence current is greater than a preset first threshold;

[0007] If the first zero-sequence current is greater than the preset first threshold, calculating a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current;

[0008] Based on the first zero-sequence admittance, determining whether the phase of the first zero-sequence admittance is greater than a preset second threshold;

[0009] If the phase of the first zero-sequence admittance is greater than a preset second threshold, a countdown is started, and a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested are obtained at the end of the countdown;

[0010] Calculating a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current;

[0011] If the phase of the second zero-sequence admittance is greater than the preset second threshold, it is determined that a fault occurs on the feeder to be tested, and a circuit breaker of the feeder to be tested is opened.

[0012] Preferably, it also includes:

[0013] If the phase of the first zero-sequence admittance is less than or equal to the preset second threshold, it is determined that no fault occurs on the feeder to be tested.

[0014] Preferably, the calculation process of the zero-sequence admittance includes:

[0015] The ratio between the zero-sequence current of the busbar at the starting end of the feeder to be tested and the zero-sequence voltage of the busbar at the starting end of the feeder to be tested is used as the zero-sequence admittance of the feeder to be tested.

[0016] Preferably, the preset second threshold is 160°.

[0017] Preferably, the preset first threshold is a maximum unbalanced current value of the feeder to be tested during normal operation.

[0018] A high-resistance grounding protection device for a grounding system, comprising:

[0019] The first measuring unit is used to measure the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested in real time;

[0020] a first judging unit, configured to judge whether the first zero-sequence current is greater than a preset first threshold;

[0021] a first calculating unit, configured to calculate a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current when the execution result of the first zero judgment unit is yes;

[0022] a second determining unit, configured to determine, based on the first zero-sequence admittance, whether a phase of the first zero-sequence admittance is greater than a preset second threshold;

[0023] a second measuring unit, configured to start a countdown when the execution result of the second judging unit is yes, and obtain a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested at the end of the countdown;

[0024] a second calculating unit, configured to calculate a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current;

[0025] A fault identification unit is configured to determine that a fault occurs on the feeder to be tested, and to disconnect a circuit breaker of the feeder to be tested, when the phase of the second zero-sequence admittance is greater than the preset second threshold.

[0026] Preferably, the device further comprises:

[0027] The non-fault identification unit is configured to determine that no fault occurs in the feeder to be tested when the execution result of the first judgment unit is no.

[0028] Preferably, the execution process of the first computing unit includes:

[0029] The ratio between the first zero-sequence current of the busbar at the starting end of the feeder to be tested and the first zero-sequence voltage of the busbar at the starting end of the feeder to be tested is used as the first zero-sequence admittance of the feeder to be tested.

[0030] A high-resistance grounding protection device for a grounding system, comprising: one or more processors, and a memory;

[0031] The memory stores computer-readable instructions, and when the computer-readable instructions are executed by the one or more processors, the steps of the high-resistance grounding protection method for the grounding system as described in any one of the above introductions are implemented.

[0032] A readable storage medium stores computer-readable instructions. When the computer-readable instructions are executed by one or more processors, the one or more processors implement the steps of the high-resistance grounding protection method for the grounding system as described in any of the above descriptions.

[0033] It can be seen from the above technical solution that the embodiment of the present application can measure the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested in real time; so that it can be determined whether the first zero-sequence current is greater than the preset first threshold value; if the first zero-sequence current is greater than the preset first threshold value, it indicates that the feeder to be tested may have a high-resistance grounding fault. In order to further confirm whether the feeder to be tested has a fault, the first zero-sequence admittance of the feeder to be tested can be calculated based on the first zero-sequence voltage and the first zero-sequence current; and based on the first zero-sequence admittance, it can be determined whether the phase of the first zero-sequence admittance is greater than the preset second threshold value; if the phase of the first zero-sequence admittance is greater than the preset second threshold value, it indicates that the feeder to be tested may have a short-term fault. In order to confirm whether a feeder with a short-term fault can automatically resume normal operation, a countdown can be started, and a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested can be obtained at the end of the countdown; after obtaining the second zero-sequence voltage and the second zero-sequence current, a second zero-sequence admittance of the feeder to be tested can be calculated based on the second zero-sequence voltage and the second zero-sequence current; so that it can be further determined based on the second zero-sequence admittance whether the feeder to be tested has a fault and cannot automatically resume normal operation. If the phase of the second zero-sequence admittance is greater than the preset second threshold, it is determined that the feeder to be tested has a fault and cannot automatically resume normal operation, thereby disconnecting the circuit breaker of the feeder to be tested to protect the normal operation of the distribution network grounding system.

[0034] This application can use the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line to determine whether a high-resistance grounding fault occurs in a low-resistance grounding system. This application uses the zero-sequence current information of a single feeder as the basis for judgment. The high-resistance grounding fault identification sensitivity is high and the fault identification is accurate. It can provide a protection strategy for single-phase high-resistance grounding faults in a low-resistance grounding system with high transition resistance tolerance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 A flow chart of a method for implementing high-resistance grounding protection in a grounding system provided in an embodiment of the present application;

[0037] Figure 2 A schematic diagram of high-resistance grounding of a 10KV low-resistance grounding system according to an embodiment of the present application;

[0038] Figure 3 A zero-sequence network diagram of a distribution network according to an embodiment of the present application;

[0039] Figure 4 A schematic diagram of the relationship between the phase angle of the zero-sequence admittance of a fault line and the number of non-fault lines according to an embodiment of the present application;

[0040] Figure 5 An example diagram of the zero-sequence admittance phase angle of a fault area and a non-fault area of ​​a distribution network illustrated in an embodiment of the present application;

[0041] Figure 6 This is a schematic structural diagram of a high-resistance grounding protection device for a grounding system according to an embodiment of the present application;

[0042] Figure 7 This is a hardware structure block diagram of a high-resistance grounding protection device for a grounding system disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0044] A common approach for analyzing distribution network faults is to measure zero-sequence current and voltage at feeder ports to determine the zero-sequence admittance of each line at the time of the fault. Generally speaking, the zero-sequence admittance of a normal phase is distributed in the first quadrant, while the zero-sequence admittance of a faulty phase is distributed in the second and third quadrants of a rectangular coordinate system. Therefore, the phase of the zero-sequence admittance can be used to identify line faults in the distribution network.

[0045] Research on high-resistance grounding protection schemes has explored the relationship between the zero-sequence currents of each outgoing line and the neutral point zero-sequence current during a fault to identify the faulty line. Others, building on existing zero-sequence current protection principles, introduce zero-sequence voltage information to correct the measured zero-sequence current, making the corrected zero-sequence current measurement similar to that of a metallic ground fault at the fault headend, thereby improving the protection sensitivity for high-resistance grounding faults in low-resistance grounding systems. However, in single-phase high-resistance grounding scenarios in low-resistance grounding systems, the fault characteristics based on zero-sequence admittance vary significantly due to different neutral point grounding methods. The zero-sequence admittance method is applied in low-resistance grounding systems, where the fault characteristics are more obvious. However, in arc suppression coil grounding systems, the phase angle of the zero-sequence admittance is affected by the compensation degree of the arc suppression coil. The fault characteristics are obvious under under-compensation and full compensation. However, under over-compensation, the phase angle of the zero-sequence measured admittance of the fault line may still be biased to the second quadrant near the positive imaginary axis, while the phase angle of the zero-sequence admittance of the non-fault line itself is close to 90 degrees. Therefore, near the positive imaginary axis, the traditional zero-sequence admittance method is prone to misjudgment, resulting in low accuracy in identifying high-resistance grounding faults.

[0046] To this end, the applicant has studied a high-resistance grounding protection scheme for the grounding system. This method can use the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line to determine whether a fault has occurred in the line. Therefore, it is not affected by the load, has a greater ability to resist load interference, high recognition sensitivity, and strong stability. Secondly, the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line used in this application are steady-state information. The problem of fault identification can be solved using single-ended information. Information processing is convenient, the algorithm is simple, and it has the characteristics of low communication volume.

[0047] The following combination Figure 1 , introduces the process of the high-resistance grounding protection method for the grounding system given in the embodiment of the present application, which may include the following steps:

[0048] Step S101 , measuring in real time the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested.

[0049] Specifically, when a fault occurs in the feeder of a low-resistance grounding system, a zero-sequence voltage will appear in the busbar voltage of the feeder, thereby affecting the normal operation of the system. Since the system is single-phase grounded, the grounding point is often accompanied by a lot of grounding resistance at the initial stage of the fault. Taking into account the influence of the arc suppression coil compensation degree and line parameters, the sensitivity of fault detection will be greatly reduced. It has been found through experiments that whether a high-resistance grounding fault occurs in the feeder can be determined by the zero-sequence voltage and zero-sequence current of the busbar at the starting end of the feeder. Therefore, in order to better identify whether a fault occurs in the feeder, the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested can be measured, so that whether a high-resistance grounding fault occurs in the feeder to be tested can be analyzed based on the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested.

[0050] Step S102: determine whether the first zero-sequence current is greater than a preset first threshold.

[0051] Specifically, considering that when line parameters of different feeders are unbalanced, the feeders will also generate zero-sequence currents. Therefore, after measuring the first zero-sequence current of the feeder to be tested, it can be determined whether the first zero-sequence current of the feeder to be tested is greater than a preset first threshold. If the first zero-sequence current of the feeder to be tested is greater than the preset first threshold, it indicates that the feeder to be tested may have a fault. To verify whether the feeder to be tested has a fault, step S103 can be executed to perform further determination.

[0052] The preset first threshold value may be set with reference to a maximum unbalanced current generated when the feeder to be tested operates normally.

[0053] Step S103: Calculate a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current.

[0054] Specifically, in practical applications, single-phase ground fault selection and location in low-current grounded power grids present difficulties. Experiments have shown that line faults occur when the measured zero-sequence admittance of the faulted line differs from the zero-sequence admittance during normal operation. Therefore, the zero-sequence admittance of the feeder under test can be used to further determine whether the feeder under test has experienced a fault. Therefore, the first zero-sequence admittance of the feeder under test can be calculated based on the first zero-sequence voltage and first zero-sequence current of the feeder under test. This allows for further verification of the feeder under test's fault status.

[0055] Step S104: Based on the first zero-sequence admittance, determine whether the phase of the first zero-sequence admittance is greater than a preset second threshold.

[0056] Specifically, as can be seen from the above description, the zero-sequence admittance during a line fault differs from the zero-sequence admittance during normal operation. Therefore, after determining the first zero-sequence admittance of the feeder under test, it is possible to determine whether the phase of the first zero-sequence admittance is greater than a preset second threshold based on the first zero-sequence admittance of the feeder under test. This is used to determine whether the feeder under test has a fault. If the phase of the first zero-sequence admittance is greater than the preset second threshold, step S105 can be executed. If the phase of the zero-sequence admittance is less than or equal to the second threshold, it can be determined that the feeder under test has not a fault.

[0057] The preset second threshold can be set to 160°.

[0058] Step S105 , starting a countdown, and obtaining a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested when the countdown ends.

[0059] Specifically, it can be seen from the above steps that if the phase of the first zero-sequence admittance is greater than the preset second threshold, it means that the feeder to be tested may have a fault. In actual applications, sometimes a short-term fault in the line can be automatically restored. For example, in windy and rainy weather, a short-term fault caused by a foreign object briefly connected to the line will automatically recover after the foreign object is separated from the line. In order to avoid misjudgment, after determining that the phase of the first zero-sequence admittance is greater than the preset second threshold, the countdown can be started again, and the second zero-sequence voltage and second zero-sequence current of the busbar at the starting end of the feeder to be tested can be obtained at the end of the countdown. In order to calculate the second zero-sequence admittance of the busbar at the starting end of the feeder to be tested at the end of the countdown.

[0060] The preset second threshold value may be set with reference to a specific application scenario. For example, the preset second threshold value may be set to 1 second.

[0061] Step S106: Calculate a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current.

[0062] Specifically, as can be seen from the above description, zero-sequence admittance can be calculated using zero-sequence voltage and zero-sequence current. Therefore, if the phase of the second zero-sequence admittance is greater than the preset second threshold, in order to further determine whether a fault has actually occurred in the feeder under test, a second zero-sequence admittance of the feeder under test can be calculated based on the second zero-sequence voltage and the second zero-sequence current. Therefore, whether a fault has occurred in the feeder under test can be analyzed based on the second zero-sequence admittance of the feeder under test.

[0063] Step S107: If the phase of the second zero-sequence admittance is greater than the preset second threshold, it is determined that a fault occurs on the feeder to be tested, and a circuit breaker of the feeder to be tested is opened.

[0064] Specifically, as can be seen from the above description, if the phase of the second zero-sequence admittance is greater than the preset second threshold, it indicates that the feeder under test has indeed experienced a fault. Therefore, it can be determined that the feeder under test has experienced a fault. The circuit breaker of the feeder under test is then disconnected to protect the distribution network and ensure normal operation of the distribution network.

[0065] For example, Figure 2 An example of a high-resistance grounding schematic diagram of a 10KV low-resistance grounding system is shown.

[0066] in,

[0067] It can be the zero-sequence current at the beginning of the fault line;

[0068] It can be the zero-sequence current at the beginning of the non-fault line;

[0069] It can be the zero-sequence voltage at the busbar outlet.

[0070] Combine Figure 2 It can be seen that there are n feeders in the distribution network. For asymmetric faults, the symmetrical component method is used for analysis, and the zero-sequence network of the distribution network is as follows: Figure 3 shown.

[0071] Among them, the expressions of each current and voltage are as follows:

[0072]

[0073]

[0074]

[0075] Where,

[0076] R f It can be a transition resistor;

[0077] j is the imaginary number symbol;

[0078] Z 1∑ 、Z 2∑ 、Z 0∑ are the total positive-sequence, negative-sequence, and zero-sequence impedances of the distribution network respectively;

[0079] ω is the angular frequency of the power frequency;

[0080] c0 is the capacitance per unit length of the line to ground;

[0081] l nu is the length of the upstream line of the fault point;

[0082] z0 is the zero-sequence impedance per unit length of the line.

[0083] The transition resistance only exists in the denominator. By dividing equation (1) by equation (3), the transition resistance term can be eliminated, and the following can be obtained:

[0084]

[0085] in,

[0086] Y up(0) It can be used to represent the equivalent admittance upstream of the fault point in the zero-sequence network, and its expression can be as follows:

[0087]

[0088] Where R g is the neutral point grounding resistance;

[0089] L g is the grounding transformer inductance;

[0090] C S(0) is the total capacitance of the distribution network to ground;

[0091] Y ∑(0) is the total zero-sequence admittance of the distribution network;

[0092] Substitute (5) into (4) and simplify to obtain:

[0093]

[0094] Similarly, by dividing equation (1) by equation (3), we can obtain the equivalent admittance Y of the non-fault line in the zero-sequence network: i(0) :

[0095]

[0096] Among them, Y i(0) is the equivalent admittance of the non-fault line in the zero-sequence network.

[0097] Equations (6) and (7) show that both faulted and non-faulted lines have zero-sequence admittance, which is the ratio of the zero-sequence current at the line start to the zero-sequence voltage at the busbar outlet. This zero-sequence admittance is unaffected by transition resistance, fault location, or load. As long as the system's operating mode remains unchanged, the zero-sequence admittance remains constant. In other words, transition resistance, fault location, and load fluctuations only affect the magnitude of the zero-sequence current and zero-sequence voltage, but do not affect the zero-sequence admittance.

[0098] Combined with the typical parameters of the 10kV distribution network, the length of each non-fault line is set to 10km. It can be found that the phase angle of the zero-sequence admittance of the fault line is related to the number of non-fault lines. However, the phase angle of the zero-sequence admittance is always greater than 160 degrees, while the phase angle of the zero-sequence admittance of the non-fault line is less than 90 degrees. The fault characteristics are very obvious. Among them, the relationship between the phase angle of the zero-sequence admittance of the fault line and the number of non-fault lines is as follows Figure 4 shown.

[0099] Therefore, it can be found that a high-resistance grounding fault protection criterion for a low-resistance grounding system based on zero-sequence admittance can be constructed as a reference for judging the occurrence of a high-resistance grounding fault in a low-resistance grounding system. The zero-sequence admittance phase as a reference can be calculated with reference to the following formula (8):

[0100]

[0101] in,

[0102] θ k Indicates the zero-sequence admittance phase angle of the reference basis.

[0103] Based on this, the zero-sequence admittance phase angle of the fault area and the non-fault area of ​​the distribution network can be obtained as follows: Figure 5 As shown, from Figure 5 It can be seen that in the admittance complex plane, the fault area and the non-fault area are clearly distinguished and there is no overlapping part.

[0104] It can be seen from the technical solution introduced above that the embodiment of the present application can use the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line to determine whether a high-resistance grounding fault occurs in a low-resistance grounding system. The present application uses the zero-sequence current information of a single feeder as the basis for judgment. The high-resistance grounding fault identification sensitivity is high and the fault identification is accurate. It can provide a protection strategy for single-phase high-resistance grounding faults in a low-resistance grounding system with high tolerance to transition resistance.

[0105] As can be seen from the above description, the embodiment of the present application can calculate the zero-sequence admittance of the feeder to be tested based on the zero-sequence voltage and the zero-sequence current. The following describes the process, which may include the following:

[0106] It is known from experiments that the zero-sequence admittance of the feeder to be tested may be equal to the ratio between the zero-sequence current of the busbar at the starting end of the feeder to be tested and the zero-sequence voltage of the busbar at the starting end of the feeder to be tested.

[0107] Right now:

[0108] It can be seen from the technical solution introduced above that the embodiment of the present application can use the zero-sequence voltage and zero-sequence current of the bus at the head end of the line to calculate the zero-sequence admittance of the feeder to be tested, so that it can be determined whether the feeder to be tested has a fault based on the zero-sequence admittance phase of the feeder to be tested.

[0109] The following describes a high-resistance grounding protection device for a grounding system provided in an embodiment of the present application. The high-resistance grounding protection device for a grounding system described below and the high-resistance grounding protection method for a grounding system described above can refer to each other.

[0110] See also Figure 6 , Figure 6 This is a schematic structural diagram of a high-resistance grounding protection device for a grounding system disclosed in an embodiment of the present application.

[0111] like Figure 6 As shown, the grounding system high-resistance grounding protection device may include:

[0112] The first measuring unit 101 is used to measure the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested in real time;

[0113] A first judging unit 102 is configured to judge whether the first zero-sequence current is greater than a preset first threshold;

[0114] A first calculating unit 103 is configured to calculate a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current when the execution result of the first zero judgment unit is yes;

[0115] A second judging unit 104 is configured to judge, based on the first zero-sequence admittance, whether the phase of the first zero-sequence admittance is greater than a preset second threshold;

[0116] The second measuring unit 105 is configured to start a countdown when the execution result of the second judging unit is yes, and obtain a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested at the end of the countdown;

[0117] A second calculation unit 106 is configured to calculate a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current;

[0118] The fault identification unit 107 is configured to determine that a fault occurs on the feeder to be tested, and disconnect a circuit breaker of the feeder to be tested, when the phase of the second zero-sequence admittance is greater than the preset second threshold.

[0119] The device of the embodiment of the present application can use the first measuring unit 101 to measure the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested in real time; so that the first judging unit 102 can be used to judge whether the first zero-sequence current is greater than a preset first threshold value; if the first zero-sequence current is greater than the preset first threshold value, it means that the feeder to be tested may have a high-resistance grounding fault. In order to further confirm whether the feeder to be tested has a fault, the first calculating unit 103 can be used to calculate the first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current; after determining the first zero-sequence admittance, the second judging unit 104 can also be used to judge whether the phase of the first zero-sequence admittance is greater than a preset second threshold value based on the first zero-sequence admittance; if the phase of the first zero-sequence admittance is greater than the preset second threshold value, it means that the feeder to be tested is faulty. A short fault may have occurred on the feeder. In order to confirm whether the feeder with the short fault can automatically resume normal operation, the second measuring unit 105 can be used to start a countdown and obtain a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested at the end of the countdown; after obtaining the second zero-sequence voltage and the second zero-sequence current, the second calculating unit 106 can be used to calculate the second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current; so that it can be further determined based on the second zero-sequence admittance whether the feeder to be tested has a fault and cannot automatically resume normal operation. If the phase of the second zero-sequence admittance is greater than the preset second threshold, the fault identification unit can be used to determine that the feeder to be tested has a fault and cannot automatically resume normal operation, thereby disconnecting the circuit breaker of the feeder to be tested to protect the normal operation of the distribution network grounding system. This application can use the zero-sequence voltage and zero-sequence current of the busbar at the head end of the line to determine whether a high-resistance grounding fault occurs in a low-resistance grounding system. This application uses the zero-sequence current information of a single feeder as the basis for judgment. The high-resistance grounding fault identification sensitivity is high and the fault identification is accurate. It can provide a protection strategy for single-phase high-resistance grounding faults in a low-resistance grounding system with high transition resistance tolerance.

[0120] Further optionally, the device further includes:

[0121] The non-fault identification unit is configured to determine that no fault occurs in the feeder to be tested when the execution result of the second judgment unit 104 is no.

[0122] Further optionally, the execution process of the first calculation unit 103 may include:

[0123] The ratio between the zero-sequence current of the busbar at the starting end of the feeder to be tested and the zero-sequence voltage of the busbar at the starting end of the feeder to be tested is used as the zero-sequence admittance of the feeder to be tested.

[0124] Among them, the specific processing flow of each unit included in the above-mentioned grounding system high-resistance grounding protection device can refer to the relevant introduction of the grounding system high-resistance grounding protection method part above, and will not be repeated here.

[0125] The grounding system high-resistance grounding protection device provided in the embodiment of the present application can be applied to grounding system high-resistance grounding protection equipment, such as terminals: computers, etc. Optionally, Figure 7 The hardware structure diagram of the high-resistance grounding protection device of the grounding system is shown. Figure 7 The hardware structure of the grounding system high-resistance grounding protection device may include: at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4.

[0126] In an embodiment of the present application, the number of processor 1 , communication interface 2 , memory 3 , and communication bus 4 is at least one, and the processor 1 , communication interface 2 , and memory 3 communicate with each other through the communication bus 4 .

[0127] The processor 1 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application;

[0128] The memory 3 may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory;

[0129] The memory stores a program, and the processor can call the program stored in the memory, wherein the program is used to implement various processing flows in the aforementioned high-resistance grounding protection solution for the terminal grounding system.

[0130] An embodiment of the present application also provides a readable storage medium, which can store a program suitable for execution by a processor, and the program is used to: implement various processing flows of the aforementioned terminal in the high-resistance grounding protection scheme of the grounding system.

[0131] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0132] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0133] The above description of the disclosed embodiments is intended to enable those skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. The various embodiments may be combined with one another. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-resistance grounding protection method for a grounding system, characterized in that: include: Real-time measurement of the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested; Determining whether the first zero-sequence current is greater than a preset first threshold; If the first zero-sequence current is greater than the preset first threshold, calculating a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current; Based on the first zero-sequence admittance, determining whether the phase of the first zero-sequence admittance is greater than a preset second threshold; If the phase of the first zero-sequence admittance is greater than a preset second threshold, a countdown is started, and a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested are obtained at the end of the countdown; Calculating a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current; If the phase of the second zero-sequence admittance is greater than the preset second threshold, it is determined that a fault occurs on the feeder to be tested, and a circuit breaker of the feeder to be tested is opened.

2. The method according to claim 1, characterized in that Also includes: If the phase of the first zero-sequence admittance is less than or equal to the preset second threshold, it is determined that no fault occurs on the feeder to be tested.

3. The method according to claim 1, characterized in that The calculation process of zero-sequence admittance includes: The ratio between the zero-sequence current of the busbar at the starting end of the feeder to be tested and the zero-sequence voltage of the busbar at the starting end of the feeder to be tested is used as the zero-sequence admittance of the feeder to be tested.

4. The method according to any one of claims 1 to 3, characterized in that The preset second threshold is 160°.

5. The method according to any one of claims 1 to 3, characterized in that The preset first threshold is the maximum unbalanced current value of the feeder to be tested during normal operation.

6. A high-resistance grounding protection device for a grounding system, characterized in that: include: The first measuring unit is used to measure the first zero-sequence voltage and the first zero-sequence current of the busbar at the starting end of the feeder to be tested in real time; a first judging unit, configured to judge whether the first zero-sequence current is greater than a preset first threshold; a first calculating unit, configured to calculate a first zero-sequence admittance of the feeder to be tested based on the first zero-sequence voltage and the first zero-sequence current when the execution result of the first judging unit is yes; a second determining unit, configured to determine, based on the first zero-sequence admittance, whether a phase of the first zero-sequence admittance is greater than a preset second threshold; a second measuring unit, configured to start a countdown when the execution result of the second judging unit is yes, and obtain a second zero-sequence voltage and a second zero-sequence current of the busbar at the starting end of the feeder to be tested at the end of the countdown; a second calculating unit, configured to calculate a second zero-sequence admittance of the feeder to be tested based on the second zero-sequence voltage and the second zero-sequence current; A fault identification unit is configured to determine that a fault occurs on the feeder to be tested, and to disconnect a circuit breaker of the feeder to be tested, when the phase of the second zero-sequence admittance is greater than the preset second threshold.

7. The device according to claim 6, characterized in that Also includes: The non-fault identification unit is configured to determine that no fault occurs in the feeder to be tested when the execution result of the first judgment unit is no.

8. The device according to claim 6, characterized in that The execution process of the first computing unit includes: The ratio between the first zero-sequence current of the busbar at the starting end of the feeder to be tested and the first zero-sequence voltage of the busbar at the starting end of the feeder to be tested is used as the first zero-sequence admittance of the feeder to be tested.

9. A high-resistance grounding protection device for a grounding system, characterized in that: include: one or more processors, and memory; The memory stores computer-readable instructions, which, when executed by the one or more processors, implement the steps of the high-resistance grounding protection method for a grounding system as claimed in any one of claims 1 to 5.

10. A readable storage medium, characterized in that: The readable storage medium stores computer-readable instructions, which, when executed by one or more processors, enable the one or more processors to implement the steps of the high-resistance grounding protection method for a grounding system as described in any one of claims 1 to 5.

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