Comprehensive identification method for grounding faults and fault types

Abstract

This invention relates to a method for comprehensively identifying ground faults and their types. The method includes the following steps: determining whether a ground fault is permanent or intermittent based on changes in zero-sequence voltage; if it is intermittent, the identification process ends. If the ground fault is permanent, determining whether it is a high-resistance ground fault based on changes in zero-sequence power; if it is, the identification process ends. If the ground fault is not a high-resistance ground fault, determining whether it is an arc ground fault based on changes in phase voltage and zero-sequence current; if it is not an arc ground fault, the ground fault is identified as a metallic ground fault. This invention novelly proposes a ground fault type identification method capable of comprehensively identifying typical power distribution network fault types such as intermittent ground faults, high-resistance ground faults, arc ground faults, and metallic ground faults.

Description

Technical Field

[0001] This invention relates to the field of grounding fault testing technology, and in particular to a method for comprehensive identification of grounding faults and fault types. Background Technology

[0002] Most power distribution network systems employ low-current grounding methods, and most faults are single-phase grounding faults. Single-phase grounding faults include various types such as intermittent grounding faults, metallic grounding faults, high-resistance grounding faults, and arcing grounding faults. Currently, research on grounding faults mainly focuses on using transient or steady-state methods for fault phase / line selection, or identifying only a single type of grounding fault. For example, patent CN108508320A proposes an arcing grounding fault identification method based on harmonic energy and waveform distortion characteristics, but this method only addresses arcing grounding faults; patent CN201210425453.X proposes a high-resistance grounding fault detection method based on the convexity and concavity of zero-sequence current waveform distortion, but this method only addresses high-resistance grounding faults. While the grounding fault detection methods disclosed in the aforementioned patents are effective, they are only applicable to specific fault characteristics and lack the ability to comprehensively identify fault types, thus limiting their practical application. Summary of the Invention

[0003] The purpose of this invention is to provide a fault type identification method to solve the problem that existing ground fault identification methods only target specific types of ground faults and cannot accurately identify multiple ground fault types. Furthermore, the purpose of this invention is to provide a comprehensive ground fault and fault type identification method to solve the problem that existing ground fault identification methods only target specific types of ground faults and cannot accurately identify multiple ground fault types.

[0004] The fault type identification method of the present invention includes the following steps:

[0005] 1) Obtain voltage and current information at the time of and before the ground fault occurs;

[0006] 2) Determine whether the grounding fault is a permanent grounding fault or an intermittent grounding fault based on the change in zero-sequence voltage. If it is an intermittent grounding fault, the identification process ends.

[0007] 3) When the ground fault is a permanent ground fault, determine whether the ground fault is a high-resistance ground fault based on the change in zero-sequence power. If it is a high-resistance ground fault, the identification process ends.

[0008] 4) When the ground fault is not a high-resistance ground fault, determine whether the ground fault is an arc ground fault based on the phase voltage change and the zero-sequence current change. If it is an arc ground fault, the identification process ends. If it is not an arc ground fault, the ground fault is determined to be a metallic ground fault, and the identification process ends.

[0009] This invention proposes a novel method for identifying grounding fault types. This method can comprehensively identify typical fault types in distribution networks, such as intermittent grounding faults, high-resistance grounding faults, arc grounding faults, and metallic grounding faults. It helps to quickly and accurately determine the causes of grounding faults, so as to formulate targeted measures for hazard mitigation and fault prevention, thereby improving the level of lean operation and maintenance and management of distribution networks.

[0010] Furthermore, in step 2), the zero-sequence voltage change rate is calculated using the sampling period as the differential interval. If the zero-sequence voltage change rate is less than -500V / s, the delay time is greater than the preset delay time, and the zero-sequence voltage at the end of the delay is less than 10V, the fault is considered a permanent grounding fault; otherwise, it is considered an intermittent grounding fault. After a grounding fault occurs in the power distribution system, during the system recovery process after the grounding fault disappears, the zero-sequence voltage exhibits a continuous attenuation process, with the amplitude attenuation value per cycle being approximately 10% to 20%, and the attenuation time not exceeding 10 cycles. If the grounding fault reappears intermittently, the amplitude of the zero-sequence voltage will increase abruptly. Therefore, based on whether the zero-sequence voltage exhibits the characteristic of continuous attenuation, the above-mentioned specific identification method can accurately determine whether the fault is an intermittent grounding fault or a permanent grounding fault.

[0011] Furthermore, in step 3), the zero-sequence power of each branch at the moment of ground fault initiation and the zero-sequence power of each branch at least one cycle before the moment of ground fault driving are calculated based on the acquired current and voltage information. Then, the change in zero-sequence power of each branch before and after the ground fault initiation is calculated, and the maximum value ΔP of the change in zero-sequence power of each branch is found. max Determine whether the condition is met. Among them, I C U is the capacitive current of the distribution network line. se The system's rated voltage is given, and k is the zero-sequence power calculation coefficient, with a value range of 0.06 to 0.1. If this condition is met, the ground fault is a high-resistance ground fault. When a high-resistance ground fault occurs in the system, only the zero-sequence current of the fault feeder contains a zero-sequence current component related to the transition resistance. The change in its zero-sequence power can effectively reflect the active power consumed by the transition resistance of the fault feeder. Furthermore, the zero-sequence power of the fault feeder is necessarily greater than that of the non-faulty feeders. Therefore, as in this scheme, after the fault starts, referring to the characteristics of the zero-sequence power of the fault feeder can accurately reflect the high-resistance ground fault of the system.

[0012] Furthermore, in step 4), based on the three-phase voltage value U at the moment of ground fault initiation... Aqd U Bqd U Cqd And the three-phase voltage value U at least one week before the ground fault starts. Aqd-nT U Bqd-nT U Cqd-nT Calculate the maximum value ΔU of the three-phase voltage change. max =max{ΔU A ,ΔU B ,ΔU C After a ground fault is initiated, zero-sequence current pulse detection is performed. The number of zero-sequence current pulses X between any two cycles within ten cycles after the fault is initiated is counted, and the number of zero-sequence current pulses Y within ten cycles after the fault is initiated is counted.

[0013] Determine if the following conditions are met:

[0014]

[0015] Where n is 1, 2, or 3;

[0016] If the above conditions are met, an arc grounding fault is considered to have occurred; if the above conditions are not met, a metallic grounding fault is considered to have occurred. After an arc grounding occurs in the system, the voltage of the faulty phase decreases, while the voltage of the non-faulty phases fluctuates and changes with the arc discharge. At the same time, the zero-sequence current of the system is unstable. At the moment of arc discharge, the zero-sequence current surge is large, and its waveform is similar to a pulse spike. Therefore, this scheme can effectively identify arc grounding faults by detecting changes in voltage and the pulse characteristics of the zero-sequence current.

[0017] Furthermore, during zero-sequence current pulse detection, the differential value of each sampling point of the zero-sequence current is calculated in real time. When the differential value 3I0'(t) of two adjacent sampling points satisfies the following condition, a zero-sequence current pulse is considered to have occurred.

[0018]

[0019] In the formula, di set This is the determination value for the differential value of the zero-sequence current.

[0020] The zero-sequence current pulse can be detected using the above criteria, which is convenient, quick, and accurate.

[0021] Furthermore, in step 1), the voltage and current information is obtained by collecting the three-phase voltage, zero-sequence voltage, and zero-sequence current of the low-voltage busbar on the low-voltage side of the distribution transformer. This replaces the distributed installation of the detection module, requires less address space, and provides better real-time data feedback and more accurate detection and identification.

[0022] Furthermore, data is acquired at a sampling frequency of at least 10 kHz. Maintaining a high sampling frequency in this way can improve detection sensitivity.

[0023] The present invention provides a method for comprehensive identification of ground faults and fault types in a power distribution network, comprising a ground fault identification method for determining whether a ground fault has occurred and a ground fault type identification method for identifying the type of ground fault. The ground fault type identification method includes the following steps:

[0024] 1) Obtain voltage and current information at the time of and before the ground fault occurs;

[0025] 2) Determine whether the grounding fault is a permanent grounding fault or an intermittent grounding fault based on the change in zero-sequence voltage. If it is an intermittent grounding fault, the identification process ends.

[0026] 3) When the ground fault is a permanent ground fault, determine whether the ground fault is a high-resistance ground fault based on the change in zero-sequence power. If it is a high-resistance ground fault, the identification process ends.

[0027] 4) When the ground fault is not a high-resistance ground fault, determine whether the ground fault is an arc ground fault based on the phase voltage change and the zero-sequence current change. If it is an arc ground fault, the identification process ends. If it is not an arc ground fault, the ground fault is determined to be a metallic ground fault, and the identification process ends.

[0028] This invention proposes a novel method for comprehensive identification of grounding faults and fault types in distribution networks. This method can comprehensively identify typical fault types in distribution networks, such as intermittent grounding faults, high-resistance grounding faults, arc grounding faults, and metallic grounding faults. It helps to quickly and accurately determine the causes of grounding faults, so as to formulate targeted measures for hazard mitigation and fault prevention, thereby improving the level of lean operation and maintenance and management of distribution networks.

[0029] Furthermore, in step 2), the zero-sequence voltage change rate is calculated using the sampling period as the differential interval. If the zero-sequence voltage change rate is less than -500V / s, the delay time is greater than the preset delay time, and the zero-sequence voltage at the end of the delay is less than 10V, the fault is considered a permanent grounding fault; otherwise, it is considered an intermittent grounding fault. After a grounding fault occurs in the power distribution system, during the system recovery process after the grounding fault disappears, the zero-sequence voltage exhibits a continuous attenuation process, with the amplitude attenuation value per cycle being approximately 10% to 20%, and the attenuation time not exceeding 10 cycles. If the grounding fault reappears intermittently, the amplitude of the zero-sequence voltage will increase abruptly. Therefore, based on whether the zero-sequence voltage exhibits the characteristic of continuous attenuation, the above-mentioned specific identification method can accurately determine whether the fault is an intermittent grounding fault or a permanent grounding fault.

[0030] Furthermore, in step 3), the zero-sequence power of each branch at the moment of ground fault initiation and the zero-sequence power of each branch at least one cycle before the moment of ground fault driving are calculated based on the acquired current and voltage information. Then, the change in zero-sequence power of each branch before and after the ground fault initiation is calculated, and the maximum value ΔP of the change in zero-sequence power of each branch is found. max Determine whether the condition is met. Among them, I C U is the capacitive current of the distribution network line. se The system's rated voltage is given, and k is the zero-sequence power calculation coefficient, with a value range of 0.06 to 0.1. If this condition is met, the ground fault is a high-resistance ground fault. When a high-resistance ground fault occurs in the system, only the zero-sequence current of the fault feeder contains a zero-sequence current component related to the transition resistance. The change in its zero-sequence power can effectively reflect the active power consumed by the transition resistance of the fault feeder. Furthermore, the zero-sequence power of the fault feeder is necessarily greater than that of the non-faulty feeders. Therefore, as in this scheme, after the fault starts, referring to the characteristics of the zero-sequence power of the fault feeder can accurately reflect the high-resistance ground fault of the system.

[0031] Furthermore, in step 4), based on the three-phase voltage value U at the moment of ground fault initiation... Aqd U Bqd U Cqd And the three-phase voltage value U at least one week before the ground fault starts. Aqd-nT U Bqd-nT U Cqd-nT Calculate the maximum value ΔU of the three-phase voltage change. max =max{ΔU A ,ΔU B ,ΔU C After a ground fault is initiated, zero-sequence current pulse detection is performed. The number of zero-sequence current pulses X between any two cycles within ten cycles after the fault is initiated is counted, and the number of zero-sequence current pulses Y within ten cycles after the fault is initiated is counted.

[0032] Determine if the following conditions are met:

[0033]

[0034] Where n is 1, 2, or 3;

[0035] If the above conditions are met, an arc grounding fault is considered to have occurred; if the above conditions are not met, a metallic grounding fault is considered to have occurred. After an arc grounding occurs in the system, the voltage of the faulty phase decreases, while the voltage of the non-faulty phases fluctuates and changes with the arc discharge. At the same time, the zero-sequence current of the system is unstable. At the moment of arc discharge, the zero-sequence current surge is large, and its waveform is similar to a pulse spike. Therefore, this scheme can effectively identify arc grounding faults by detecting changes in voltage and the pulse characteristics of the zero-sequence current.

[0036] Furthermore, during zero-sequence current pulse detection, the differential value of each sampling point of the zero-sequence current is calculated in real time. When the differential value 3I0'(t) of two adjacent sampling points satisfies the following condition, a zero-sequence current pulse is considered to have occurred.

[0037]

[0038] In the formula, di set This is the determination value for the differential value of the zero-sequence current.

[0039] The zero-sequence current pulse can be detected using the above criteria, which is convenient, quick, and accurate.

[0040] Furthermore, in step 1), the voltage and current information is obtained by collecting the three-phase voltage, zero-sequence voltage, and zero-sequence current of the low-voltage busbar on the low-voltage side of the distribution transformer. This replaces the distributed installation of the detection module, requires less address space, and provides better real-time data feedback and more accurate detection and identification.

[0041] Furthermore, data is acquired at a sampling frequency of at least 10 kHz. Maintaining a high sampling frequency in this way can improve detection sensitivity.

[0042] Furthermore, the ground fault identification method includes a fault identification step. This step involves real-time calculation of the current zero-sequence voltage amplitude and at least one cycle-ahead zero-sequence voltage amplitude, and calculation of the zero-sequence voltage mutation. If the zero-sequence voltage mutation exceeds a preset mutation parameter, a ground fault is considered to have occurred. This fault identification step enables accurate detection of ground faults and allows for timely identification of the fault type through subsequent steps. It also allows for rapid determination of the cause of the ground fault, facilitating the development of targeted hazard mitigation and fault prevention measures. Attached Figure Description

[0043] Figure 1 This is a flowchart of Embodiment 1 of the distribution network grounding fault and fault type comprehensive identification method of the present invention. Detailed Implementation

[0044] This invention proposes a comprehensive identification method for grounding faults and fault types in distribution networks. Based on the fault mechanisms of various grounding fault types, it integrates different fault identification algorithms and a complete identification process, which can cover a variety of typical fault types in distribution networks, such as intermittent grounding faults, high-resistance grounding faults, arc grounding faults, and metallic faults. This helps to determine the causes of grounding faults, so as to formulate targeted measures for hidden danger management and fault prevention, and improve the level of lean operation and maintenance and management of distribution networks.

[0045] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0046] See Figure 1 In this embodiment, the comprehensive identification method for ground faults and fault types in the distribution network includes a ground fault identification method for determining whether a ground fault has occurred and a ground fault type identification method for identifying the type of ground fault. The ground fault identification device is deployed on the low-voltage side of the distribution transformer and is connected to the three-phase voltage (UA, UB, UC), zero-sequence voltage 3U0, and system zero-sequence current 3I0 of the low-voltage side bus of the distribution transformer at a sampling frequency of not less than 10kHz.

[0047] The specific methods for identifying grounding faults are as follows:

[0048] Based on the collected data, the system is assessed in real time to determine if a ground fault has occurred. Specifically, the current zero-sequence voltage amplitude and the zero-sequence voltage amplitude two weeks prior are calculated in real time, and the difference between the two is calculated to obtain the zero-sequence voltage change Δ3U0. If the zero-sequence voltage change is greater than 5V, a system fault is considered to have occurred, and fault type identification begins. During fault type identification, the system's zero-sequence voltage Δ3U0 at the moment the ground fault initiates is recorded. qd Phase voltage (U) Aqd U Bqd U Cqd ), zero-sequence current 3I0 qd Zero-sequence current 3I0 in each branch of the busbar qdn Record the system zero-sequence voltage 3U0 one cycle before the ground fault initiation time. qd-T Phase voltage (U) Aqd-T U Bqd-T U Cqd-T ), zero-sequence current 3I0 qd-T 3I0 of each branch of the busbar iqd-T .

[0049] It should be noted that in other embodiments, the current zero-sequence voltage amplitude and the zero-sequence voltage amplitude one or three cycles ago can also be calculated in real time as the basis for calculation. The zero-sequence voltage amplitude one cycle ago can also be used as the basis for calculation. However, this will increase the data storage requirements of the equipment and increase the burden on the equipment. The zero-sequence voltage amplitude one cycle ago can also be selected. However, since it is close to the start time of the ground fault, the zero-sequence change may not be able to accurately reflect the fault occurrence phenomenon. Therefore, in this embodiment, the zero-sequence voltage amplitude two cycles ago is preferred as the basis for calculation.

[0050] In this embodiment, the preset standard value for the zero-sequence voltage change that determines whether a ground fault has occurred is preferably 5V. Of course, in other embodiments, it can be 3V, 4V, or other natural values ​​above 6V. A smaller preset standard value achieves higher sensitivity, but may lead to false positives due to system fluctuations. A larger preset standard value avoids false positives caused by system fluctuations, but excessively large preset standard values ​​reduce sensitivity and cause a significant delay in detecting ground faults. In this embodiment, a preset standard value of 5V is preferred, ensuring both high sensitivity and minimizing the risk of false positives.

[0051] The specific method for identifying ground fault types is as follows:

[0052] After determining that a ground fault has occurred in the system, the first step is to identify whether the ground fault is permanent.

[0053] Mechanistically, after a ground fault occurs in a power distribution system, during the system recovery process after the ground fault disappears, the zero-sequence voltage 3U0 exhibits a continuous attenuation process, with the amplitude decreasing by approximately 10% to 20% per cycle, and the attenuation time not exceeding 10 cycles. If the ground fault reappears intermittently, the amplitude of the zero-sequence voltage 3U0 will increase abruptly. Therefore, this invention determines whether a fault is reliably grounded based on whether the zero-sequence voltage exhibits the characteristic of continuous attenuation.

[0054] The identification method is as follows:

[0055] The zero-sequence voltage change rate is calculated using the device sampling period Ts (0.1ms, the specific sampling period depends on the sampling frequency of the ground fault identification device) as the differential interval. If the following equation (1) is satisfied, that is, the zero-sequence voltage change rate is less than -500V / s and the delay time t set If the delay is greater than 0.4s and the zero-sequence voltage at the end of the delay is less than 10V, the fault is considered to be a reliable grounding fault and a permanent grounding fault; otherwise, it is considered to be an intermittent grounding fault and the identification process ends.

[0056]

[0057] In the formula, t set The delay time is adjustable; the default delay time is 0.4s. 3U0(t) set ) is the set delay t set The zero-sequence voltage amplitude is calculated at the end time. In this step, the preset delay time can be adaptively selected according to the magnitude of the rate of change, with a range of 0.2s-0.5s being preferred.

[0058] When the ground fault is a permanent ground fault, further identify whether the ground fault is a high-resistance ground fault.

[0059] Mechanistically, when a high-resistance ground fault occurs in the system, only the zero-sequence current of the faulted feeder contains a zero-sequence current component related to the transition resistance. The change in its zero-sequence power can effectively reflect the active power consumed by the transition resistance of the faulted feeder; and the zero-sequence power of the faulted feeder is necessarily greater than that of the non-faulted feeders. Therefore, after the fault starts, the characteristics of the zero-sequence power of the faulted feeder can be used to reflect the high-resistance ground fault in the system.

[0060] Specifically, it includes the following steps:

[0061] Step 1: Calculate the zero-sequence power of each branch at the moment of fault initiation according to the following formula (2);

[0062]

[0063] Step 2: Calculate the zero-sequence power of each branch one week before the fault start time according to the following formula (3);

[0064]

[0065] Step 3: Calculate the change in zero-sequence power of each branch before and after the fault starts according to the following formula (4);

[0066] ΔP i =P iqd -P iqd-T Equation (4);

[0067] Step 4: Find the maximum value ΔP of the zero-sequence power change in each branch. max ;

[0068] At this point, determine the maximum value ΔP of the zero-sequence power change. max If the following formula (5) is satisfied, the ground fault is considered to be a high-resistance ground fault, and the identification process ends; if it is not satisfied, the ground fault is considered not to be a high-resistance ground fault, and the next step of the identification process continues.

[0069]

[0070] Among them, I CU is the capacitive current of the distribution network line. se The voltage is the rated voltage of the system, and k is the zero-sequence power calculation coefficient. Since the capacitor current of the distribution network system is generally 100A to 300A, the value range of k is approximately 0.06 to 0.1.

[0071] If the grounding fault is not a high-resistance grounding fault, further identification is needed to determine whether the grounding fault is an arc grounding fault.

[0072] Mechanistically, after an arc grounding occurs in the system, the voltage of the faulty phase decreases, while the voltage of the non-faulty phase fluctuates and changes with the arc discharge. At the same time, the zero-sequence current of the system is unstable. At the moment of arc discharge, the zero-sequence current surges significantly, and its waveform is similar to a pulse spike. Therefore, the voltage change and the pulse characteristics of the zero-sequence current can be detected to identify the arc grounding fault.

[0073] The specific identification method includes the following steps:

[0074] Step 1: Calculate the change in phase voltage according to the following formula (6);

[0075]

[0076] In the formula: U Aqd U Bqd U Cqd These are the three-phase voltage values ​​at the moment of fault initiation, U Aqd-T U Bqd-T U Cqd-T These are the three-phase voltage values ​​one week before the fault started.

[0077] Step 2: Find the maximum value ΔU of the three-phase voltage change. max =max{ΔU A ,ΔU B ,ΔU C};

[0078] Step 3: After the ground fault is initiated, calculate the differential value of the zero-sequence current at each sampling point in real time. Zero-sequence current pulse detection is performed. When the differential value 3I0'(t) of two adjacent sampling points satisfies the following equation (7), it is considered that a zero-sequence current pulse has occurred.

[0079]

[0080] In the formula, di set This is the determination value for the differential value of the zero-sequence current.

[0081] Step 4: Count the number of zero-sequence current pulses X between any two cycles within ten cycles after the fault starts.

[0082] Step 5: Count the number of zero-sequence current pulses Y within ten cycles after the fault starts.

[0083] After the above steps are completed, if the following formula (8) is satisfied, the system is considered to have an arc grounding fault. If the following formula (8) is not satisfied, the system is considered to have a metallic grounding fault.

[0084]

[0085] The identification process is now complete.

[0086] In this identification step, the zero-sequence current pulse detection can also be performed using other existing methods, and is not necessarily based on the zero-sequence current differential value as described in this embodiment.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. The scope of patent protection of the present invention shall be determined by the claims. Similarly, any equivalent structural changes made based on the description and drawings of the present invention shall also be included within the scope of protection of the present invention.

Claims

1. A method for identifying ground fault types, characterized in that, Includes the following steps: 1) Obtain voltage and current information at the time of and before the ground fault occurs; 2) Determine whether the grounding fault is permanent or intermittent based on the change in zero-sequence voltage. If it is an intermittent grounding fault, the identification process ends. 3) When the ground fault is a permanent ground fault, determine whether the ground fault is a high-resistance ground fault based on the change in zero-sequence power. If it is a high-resistance ground fault, the identification process ends. 4) When the ground fault is not a high-resistance ground fault, determine whether the ground fault is an arc ground fault based on the phase voltage change and the zero-sequence current change. If it is an arc ground fault, the identification process ends. If it is not an arc ground fault, the ground fault is determined to be a metallic ground fault, and the identification process ends. In step 2), the zero-sequence voltage change rate is calculated with the sampling period as the differential interval. If the zero-sequence voltage change rate is less than -500V / s, the delay time is greater than the preset delay time, and the zero-sequence voltage at the end of the delay is less than 10V, the fault is considered to be a permanent ground fault; otherwise, it is considered to be an intermittent ground fault.

2. The ground fault type identification method according to claim 1, characterized in that, In step 3), based on the acquired current and voltage information, the zero-sequence power of each branch at the time of ground fault initiation and the zero-sequence power of each branch at least one cycle before the ground fault driving time are calculated. Then, the change in zero-sequence power of each branch before and after the ground fault initiation is calculated, and the maximum value of the change in zero-sequence power of each branch is found. Determine whether the condition is met. ,in, This refers to the capacitive current of the distribution network line. The system's rated voltage, The zero-sequence power calculation coefficient, The corresponding value range is 0.06~0.1; if this condition is met, the ground fault is a high-resistance ground fault.

3. The ground fault type identification method according to claim 1, characterized in that, In step 4), based on the three-phase voltage value U at the moment of ground fault initiation... Aqd U Bqd U Cqd And the three-phase voltage value U at least one week before the ground fault starts. Aqd-nT U Bqd-nT U Cqd-nT Calculate the maximum value of the three-phase voltage change. After a ground fault is initiated, zero-sequence current pulse detection is performed. The number of zero-sequence current pulses X between any two cycles within ten cycles after the fault is initiated is counted, and the number of zero-sequence current pulses Y within ten cycles after the fault is initiated is counted. Determine if the following conditions are met: ； Where n is 1, 2, or 3; If the above conditions are met, an arc grounding fault is considered to have occurred; if the above conditions are not met, a metallic grounding fault is considered to have occurred.

4. The ground fault type identification method according to claim 3, characterized in that, in When performing zero-sequence current pulse detection, the differential value of the zero-sequence current at each sampling point is calculated in real time. When the differential values ​​of two adjacent sampling points are... A zero-sequence current pulse is considered to have occurred if the following conditions are met: ； In the formula, This is the determination value for the differential value of the zero-sequence current.

5. The ground fault type identification method according to any one of claims 1-4, characterized in that, In step 1), the voltage and current information is obtained by collecting the three-phase voltage, zero-sequence voltage, and zero-sequence current of the low-voltage busbar of the distribution transformer.

6. The ground fault type identification method according to claim 5, characterized in that, Data is collected at a sampling frequency of not less than 10kHz.

7. A method for comprehensive identification of grounding faults and fault types in a distribution network, comprising a grounding fault identification method for determining whether a grounding fault has occurred and a grounding fault type identification method for identifying the type of grounding fault, characterized in that, The ground fault type identification method includes the following steps: 1) Obtain voltage and current information at the time of and before the ground fault occurs; 2) Determine whether the grounding fault is permanent or intermittent based on the change in zero-sequence voltage. If it is an intermittent grounding fault, the identification process ends. 3) When the ground fault is a permanent ground fault, determine whether the ground fault is a high-resistance ground fault based on the change in zero-sequence power. If it is a high-resistance ground fault, the identification process ends. 4) When the ground fault is not a high-resistance ground fault, determine whether the ground fault is an arc ground fault based on the phase voltage change and the zero-sequence current change. If it is an arc ground fault, the identification process ends. If it is not an arc ground fault, the ground fault is determined to be a metallic ground fault, and the identification process ends. In step 2), the zero-sequence voltage change rate is calculated with the sampling period as the differential interval. If the zero-sequence voltage change rate is less than -500V / s, the delay time is greater than the preset delay time, and the zero-sequence voltage at the end of the delay is less than 10V, the fault is considered to be a permanent ground fault; otherwise, it is considered to be an intermittent ground fault.

8. The method for comprehensive identification of grounding faults and fault types in distribution networks according to claim 7, characterized in that, In step 3), based on the acquired current and voltage information, the zero-sequence power of each branch at the time of ground fault initiation and the zero-sequence power of each branch at least one cycle before the ground fault driving time are calculated. Then, the change in zero-sequence power of each branch before and after the ground fault initiation is calculated, and the maximum value of the change in zero-sequence power of each branch is found. Determine whether the condition is met. ,in, This refers to the capacitive current of the distribution network line. The system's rated voltage, The zero-sequence power calculation coefficient, The corresponding value range is 0.06~0.1; if this condition is met, the ground fault is a high-resistance ground fault.

9. The method for comprehensive identification of grounding faults and fault types in distribution networks according to claim 7, characterized in that, In step 4), based on the three-phase voltage value U at the moment of ground fault initiation... Aqd U Bqd U Cqd And the three-phase voltage value U at least one week before the ground fault starts. Aqd-nT U Bqd-nT U Cqd-nT Calculate the maximum value of the three-phase voltage change. After a ground fault is initiated, zero-sequence current pulse detection is performed. The number of zero-sequence current pulses X between any two cycles within ten cycles after the fault is initiated is counted, and the number of zero-sequence current pulses Y within ten cycles after the fault is initiated is counted. Determine if the following conditions are met: ； Where n is 1, 2, or 3; If the above conditions are met, an arc grounding fault is considered to have occurred; if the above conditions are not met, a metallic grounding fault is considered to have occurred.

10. The method for comprehensive identification of grounding faults and fault types in distribution networks according to claim 9, characterized in that, in When performing zero-sequence current pulse detection, the differential value of the zero-sequence current at each sampling point is calculated in real time. When the differential values ​​of two adjacent sampling points are... A zero-sequence current pulse is considered to have occurred if the following conditions are met: ； In the formula, This is the determination value for the differential value of the zero-sequence current.

11. The method for comprehensive identification of grounding faults and fault types in distribution networks according to any one of claims 7-10, characterized in that, In step 1), the voltage and current information is obtained by collecting the three-phase voltage, zero-sequence voltage, and zero-sequence current of the low-voltage busbar of the distribution transformer.

12. The method for comprehensive identification of grounding faults and fault types in distribution networks according to claim 11, characterized in that, Data is collected at a sampling frequency of not less than 10kHz.

13. The method for comprehensive identification of grounding faults and fault types in distribution networks according to claim 7, characterized in that, The ground fault identification method includes real-time calculation of the current zero-sequence voltage amplitude and the zero-sequence voltage amplitude at least one cycle ago, and calculation of the zero-sequence voltage mutation amount. If the zero-sequence voltage mutation amount is greater than the preset mutation amount parameter, a ground fault is considered to have occurred.

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