A dead zone fault identification system and method suitable for feeder automation system

Abstract

The present invention discloses a dead zone fault identification system for a feeder automation system, comprising a main control unit and various sub-units; the sub-units are arranged at various branches of a distribution network busbar, and the sub-units are connected to the main control unit via an EtherCAT bus; the sub-units collect current and voltage information of each branch and transmit the collected information to the main control unit. The main control unit determines whether a dead zone fault occurs based on the collected information, i.e., the feedback current of the load, and transmits corresponding instructions to the corresponding sub-units according to the fault condition. The sub-units execute the control to control the on and off of the circuit breaker at the branch according to the instructions. In this scheme, the main control unit and each sub-unit adopt EtherCAT (Ethernet Control Automation Technology), which has low latency, high transmission rate, anti-interference, and low cost. By utilizing a new protection algorithm and a new bus scheme, when a dead zone fault occurs in a load or power supply with feedback current, the dead zone fault can be accurately located, a trip command is sent to the branch circuit breaker where the dead zone fault occurs, the circuit breaker is tripped, and the dead zone fault is eliminated, thereby quickly and accurately identifying the dead zone fault of the entire ring network.

Description

Technical Field

[0001] The present invention belongs to the field of distribution network ring network fault determination, and in particular relates to a dead zone fault determination system and method applicable to a feeder automation system. Background Art

[0002] A dead zone fault occurs when a fault occurs within a specific section of a line, generating a fault signal that does not trigger the protection device to operate. This fault is called a dead zone fault. Traditional distribution networks primarily consist of centralized power plants, substations, and traditional power lines. Their structure is relatively simple, and fault characteristics are clearly defined. Distributed distribution networks, typically comprised of multiple distributed energy resources and various intelligent power electronic devices, are more complex and dynamic. Distributed distribution networks also feature bidirectional current flow, including feedback current. When a fault occurs between a circuit breaker and a current transformer at the busbar outlet, the current transformer will be unable to detect the fault current, rendering the protection device inoperative, thus generating a dead zone fault. Furthermore, the feeder automation system will be unable to obtain fault current information and effectively identify the fault segment and nature, resulting in delayed fault clearance and potentially widening the fault range. Existing relay protection technology needs to be upgraded and improved.

[0003] To address dead zone faults, the current method is to install circuit breakers and current transformers on both sides of the line and a ring network bus differential protection device at the busbar. This device uses longitudinal differential protection and bus differential protection to determine the faulty area when a fault occurs. The protection device then trips the circuit breaker to resolve the dead zone fault. However, this existing technology has the following problems:

[0004] (1) It is difficult to accurately locate dead zone faults, and the protection action has a wide impact range. When the ring network bus differential protection device identifies a dead zone fault, it remotely disconnects the upper level "three remote" switch of the fault zone boundary switch and the branch switch between the two, and remotely closes the power station outgoing line switch and the connecting switch to restore power supply to the non-fault area. Its protection range involves the entire ring network bus, and the impact range is large;

[0005] (2) Troubleshooting is difficult and requires a lot of work: When the ring network with a dead zone fault is isolated, manual inspection is required. All branches and upstream and downstream branches within the fault range of the ring network must be checked one by one to eliminate the fault. This requires a lot of work, high cost, and a long time. Summary of the Invention

[0006] In view of the above problems, an object of the present invention is to provide a dead zone fault identification system and method applicable to a feeder automation system.

[0007] The specific technical solutions for achieving the purpose of the present invention are as follows:

[0008] A dead zone fault identification system applicable to a feeder automation system, comprising a main control unit and various slave units;

[0009] The sub-machine units are arranged at each branch of the power distribution network bus, and each sub-machine unit is connected to the main control unit via an EtherCAT bus;

[0010] The sub-machine unit collects the current and voltage information of each branch and transmits the collected information to the main control unit. The main control unit determines whether a dead zone fault occurs based on the collected information, and transmits corresponding instructions to the corresponding sub-machine unit according to the fault situation. The sub-machine unit executes the control branch to turn on and off the circuit breaker according to the instructions.

[0011] Furthermore, the main control unit determines whether a dead zone fault occurs based on the collected information, specifically:

[0012] First, determine whether a fault may occur based on the busbar differential protection criteria at the branch:

[0013]

[0014] Among them, Represents the power frequency variation current of the i-th branch; I op.min Indicates the minimum operating current of the busbar longitudinal differential protection, K res The braking coefficient of the differential protection including the feedback current is expressed as the braking coefficient. If the above formula is satisfied, it is considered that the system may have a fault and the next judgment is made. Otherwise, it is considered that there is no fault.

[0015] Then judge the value of the current and its direction:

[0016] If I>I set , D irect <0, it is determined that the branch has a dead zone fault, otherwise it is considered that there is no fault;

[0017] Among them, I set is the set criterion current, D irect is the direction of current, where the current flowing through the current transformer is positive when it flows from the bus to the load, and negative when it flows from the bus to the load.

[0018] Furthermore, when the main control unit determines that a dead zone fault occurs in the system, it sends an instruction to the slave unit corresponding to the faulty branch line, and the slave unit controls the circuit breaker to trip according to the instruction.

[0019] Furthermore, the sub-machine unit includes a power supply, an MCU main control chip, an EtherCAT ESC control chip, an Ethernet interface, a WIFI module, a GPRS module, a USB interface, a voltage sampling module, a current sampling module and a switch execution unit;

[0020] The MCU main control chip is respectively connected to the EtherCAT ESC control chip, WIFI module, GPRS module, USB interface, voltage sampling module, current sampling module and switch execution unit. The power supply supplies power to each part of the slave unit. The EtherCAT ESC control chip is used to connect to the host computer through the Ethernet interface and connect each slave unit to the main control unit; the voltage sampling module and current sampling module are used to collect current and voltage information at each branch of the distribution network bus.

[0021] Furthermore, the communication between the main control unit and each slave unit adopts EtherCAT. In the EtherCAT network, the main control unit sends data to all slave units through a single Ethernet frame. Then, each slave unit processes the data in real time after receiving it and passes the result to the next slave unit, which is finally returned to the main control unit.

[0022] That is, the main control unit quickly obtains the switch status, sampled voltage and current values ​​of each circuit breaker from the slave unit through the EtherCAT protocol, and executes the protection judgment. If the sampled value of a slave unit exceeds the set value, the main control unit immediately sends a downlink message to the slave unit. The message data traverses all slave units. The slave unit extracts or inserts data at the specified position in the EtherCAT data frame according to the EtherCAT frame header of the downlink message, and transmits the message to the next slave unit at the same time; after reading the data, the designated slave unit executes the host instruction, outputs the switching value, and disconnects the circuit breaker; when the message reaches the last slave unit in the system logical position, the slave unit returns the processed message as an uplink message to the main control unit.

[0023] Furthermore, the EtherCAT data frame includes an Ethernet frame header, a data packet and an FSC frame check sequence. The Ethernet frame header includes a source address, a destination address and an Ethernet frame type. The EtherCAT Ethernet frame type is Ox88A4. The transmitted data includes a data length and several sub-messages. Each sub-message has a logical address, an offset address and read and write data, and is used to transmit data such as I / O values, application layer protocols and mailbox communications. The frame check sequence verifies whether the data is erroneous through a 32-bit CRC algorithm. Each data packet includes a data packet header, data and a counter.

[0024] The present invention also provides a dead zone fault identification method applicable to a feeder automation system based on the above system, comprising the following steps:

[0025] Step 1: The slave unit collects the current and voltage information of each branch;

[0026] Step 2: The main control unit determines whether a dead zone fault occurs based on the collected information and sends corresponding instructions to the corresponding slave unit;

[0027] Step 3: The slave unit controls the circuit breaker at the branch according to the instruction.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The dead zone fault discrimination of the present invention is achieved by setting up slave units at each branch of the distribution network bus. In the process of fault discrimination after collecting information, a bus differential protection algorithm including feedback current is included, and dead zone discrimination is achieved according to the feedback current of the load. At the same time, EtherCAT (Ethernet control automation technology) is used in the main control unit and each slave unit, which has low latency, high transmission rate, anti-interference, and low cost, and can quickly and accurately realize dead zone fault discrimination of the entire ring network.

[0030] The present invention utilizes a novel protection algorithm and a brand-new bus solution. When a dead-zone fault occurs in a load or power supply with feedback current, the dead-zone fault is accurately located, and a tripping command is sent to the branch circuit breaker where the dead-zone fault occurs, thereby tripping the circuit breaker and eliminating the dead-zone fault.

[0031] The present invention will be further described below with reference to specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 2 is a schematic diagram of a dead zone fault identification system architecture applicable to a feeder automation system in an embodiment of the present invention.

[0033] Figure 2 This is a dead zone fault discrimination logic diagram in an embodiment of the present invention.

[0034] Figure 3 This is a dead zone fault determination flow chart in an embodiment of the present invention.

[0035] Figure 4 This is an example diagram of a branch line in an embodiment of the present invention.

[0036] Figure 5 Schematic diagram of the structure of the sub-unit in the embodiment of the present invention Figure 1 .

[0037] Figure 6 Schematic diagram of the structure of the sub-unit in the embodiment of the present invention Figure 2 .

[0038] Figure 7 This is an EtherCAT communication flow chart in an embodiment of the present invention.

[0039] Figure 8Schematic diagram of the EtherCAT data frame structure in an embodiment of the present invention.

[0040] Figure 9 A flow chart for configuring a main control unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] Example

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0043] Combine Figure 1 , a dead zone fault identification system for a feeder automation system, comprising a main control unit and various slave units;

[0044] The sub-machine units are arranged at each branch of the power distribution network bus, and each sub-machine unit is connected to the main control unit via an EtherCAT bus;

[0045] The sub-machine unit collects the current and voltage information of each branch and transmits the collected information to the main control unit. The main control unit determines whether a dead zone fault occurs based on the collected information, and transmits corresponding instructions to the corresponding sub-machine unit according to the fault situation. The sub-machine unit executes the control branch to turn on and off the circuit breaker according to the instructions.

[0046] Furthermore, the main control unit determines whether a dead zone fault occurs based on the collected information, specifically:

[0047] Combine Figure 2 and Figure 3 First, determine whether a fault may occur based on the bus differential protection criterion at the branch:

[0048]

[0049] Among them, Represents the power frequency variation current of the i-th branch; I op.min Indicates the minimum operating current of the busbar longitudinal differential protection, K res The braking coefficient of the differential protection including the feedback current is expressed as the braking coefficient. If the above formula is satisfied, it is considered that the system may have a fault and the next judgment is made. Otherwise, it is considered that there is no fault.

[0050] Then judge the value of the current and its direction:

[0051] If I>I set , D irect <0, it is determined that the branch has a dead zone fault, otherwise it is considered that there is no fault;

[0052] Among them, I set The criterion current is set, and its value is selected by comprehensively considering the freewheeling effect of the distributed power supply and the feedback current of the motor. irect is the direction of current, where the current flowing through the current transformer is positive when it flows from the bus to the load, and negative when it flows from the bus to the load.

[0053] When the main control unit determines that a dead zone fault occurs in the system, it sends an instruction to the slave unit corresponding to the faulty branch line, and the slave unit controls the circuit breaker to trip according to the instruction.

[0054] That is, on the basis of satisfying the busbar difference criterion, if the current criterion and the direction criterion of a branch meet the conditions at the same time, it is determined that a dead zone fault has occurred in the branch and the branch circuit breaker is tripped.

[0055] Combine Figure 4 , is an example diagram of a branch line in this embodiment. When the load is a motor or distributed power source, the feedback current during a fault is considered. If a fault occurs between QF1 and TA1, the current flowing through TA2 and TA3 is the feedback current of the motor or distributed power source, respectively. If a fault occurs between QF2 and TA2, the current flowing through TA2 is the feedback current of the motor or distributed power source, and the current direction is from the load to the busbar. The same applies when a fault occurs between QF3 and TA3.

[0056] Combine Figure 5 and Figure 6 The sub-machine unit includes a power supply, an MCU main control chip, an EtherCAT ESC control chip, an Ethernet interface, a WIFI module, a GPRS module, a USB interface, a voltage sampling module, a current sampling module and a switch execution unit;

[0057] The power supply adopts an isolated power supply and a non-isolated power supply, the isolated power supply supplies power to the current channel, the voltage channel and the execution unit, and the non-isolated power supply supplies power to the remaining components;

[0058] The MCU main control chip is respectively connected to the EtherCAT ESC control chip, WIFI module, GPRS module, USB interface, voltage sampling module, current sampling module and switch execution unit. The power supply supplies power to each part of the slave unit. The EtherCAT ESC control chip is used to connect to the host computer through the Ethernet interface and connect each slave unit to the main control unit; the voltage sampling module and the current sampling module are used to collect current and voltage information at each branch of the distribution network bus;

[0059] In this embodiment, the slave unit also includes an LCD and buttons, and the switch output unit includes relays and switch outputs. The MCU is connected to the EtherCAT ESC control chip via the FSMC. The ESC control chip is a LAN9253 controller specifically designed for EtherCAT slaves, integrating the EtherCAT protocol stack. It connects to devices on the bus via a network transformer and the Ethernet RJ45 interface at the physical layer. A USB port is used for on-site configuration of the host computer. Current and voltage samples are optically isolated and filtered before being sampled via an ADC using industrial control standard voltage levels of 0V-10V and fed through a parallel bus to the main control MCU. The relay outputs the switch value using industrial control standard voltage levels of 0V / 24V to activate the circuit breaker. The LCD and buttons serve as human-computer interaction. The GUI on the LCD includes current protection settings, device status reports, fault recording, and protocols. The MCU is a 32-bit STM32F407, which includes control algorithms and drivers for various communication protocols. The ESC uses EEPROM to store necessary device-related information and connects to the ESC chip via the IIC protocol. The USB port uses the RS232 standard.

[0060] Combine Figure 7 , the communication between the main control unit and each slave unit adopts EtherCAT (Ethernet Control Automation Technology), an Ethernet fieldbus technology developed by Beckhoff of Germany. EtherCAT is one of the fastest industrial Ethernet technologies. At the same time, it provides nanosecond-level precise synchronization clock and reaches a transmission speed of hundreds of megabits per second (Mbps). Generally speaking, EtherCAT's unique master-slave communication mechanism brings extremely high communication speeds. In the EtherCAT network, the main control unit sends data to all slave units through a single Ethernet frame, and then each slave unit processes the data in real time after receiving it and passes the result to the next slave unit, and finally returns it to the main control unit;

[0061] The master control unit rapidly obtains the switch status, sampled voltage, and current values ​​of each circuit breaker from slave units via the EtherCAT protocol and executes protection criteria. If a slave unit's sampled value exceeds a set value, the master control unit immediately sends a downlink message to the slave unit. The message data traverses all slave units. Based on the downlink message's EtherCAT frame header, the slave unit extracts or inserts data at a specified location within the EtherCAT data frame and transmits the message to the next slave unit. After reading the data, the designated slave unit executes the host's instructions, outputs a switching value, and opens the circuit breaker. When the message reaches the last slave unit in the system's logical position, it returns the processed message as an uplink message to the master control unit. EtherCAT Ethernet frames fully utilize bandwidth during transmission and reception. A single Ethernet frame carries all slave unit data, resulting in data transmission rates of up to 90% and above, reaching full-duplex speeds of 100 Mbit / s. This fully utilizes the data exchanged in a single data frame, equivalent to over 1,000 I / Os, and a sampling frequency of up to 20 kHz.

[0062] Combine Figure 8 The EtherCAT data frame includes an Ethernet frame header, a data packet, and an FSC frame check sequence. The Ethernet frame header includes the source address, destination address, and Ethernet frame type. The EtherCAT Ethernet frame type is Ox88A4. The transmitted data includes the data length and several sub-messages. Each sub-message has a logical address, an offset address, and read / write data, and is used to transmit data such as I / O values, application layer protocols, and mailbox communications. The frame check sequence verifies whether the data is error-free using a 32-bit CRC algorithm. Each data packet includes a data packet header, data, and a counter. The data packet header serves as the functional area of ​​the data and contains various instructions for the data. The counter records the number of times the EtherCAT sub-message is operated by the slave after a communication between the master and slave ends.

[0063] IgH EtherCAT Master is used to develop the main control unit. IgH EtherCAT Master consists of three parts: host module, device driver module, and application program. RT-Preempt is used as the kernel real-time patch. Download and install the RT-Preempt patch source code, and use SecureCRT software to check whether the installation is successful.

[0064] Combine Figure 9 , the configuration method of the main control unit in this embodiment is:

[0065] Step 1: Request a master control unit and configure it, including the startup script and related modules;

[0066] Step 2: Configure MAC, address and network card type;

[0067] Step 3: Check whether the configuration is correct. If it is correct, proceed to the next step. If not, an error message will be displayed.

[0068] Step 4: Configure distributed clocks;

[0069] Step 5: Configure the process data domain;

[0070] Step 6: Configure the process data mapping and the starting address of the mapping. The slave first reads the data from the PDO and then writes the data to be sent to the host.

[0071] Step 7: Determine whether the slave unit is running correctly. If so, activate the main control unit. If not, alarm.

[0072] Step 8: Activate the main control unit to enable the main control unit to start automatically.

[0073] Step 9: Enter the periodic operation, call the periodic function, enter the EtherCAT state machine, IgH EtherCATMaster enters the working phase, and the EtherCAT master control unit starts running.

[0074] The present invention also provides a dead zone fault identification method applicable to a feeder automation system based on the above system, comprising the following steps:

[0075] Step 1: The slave unit collects the current and voltage information of each branch;

[0076] Step 2: The main control unit determines whether a dead zone fault occurs based on the collected information and sends corresponding instructions to the corresponding slave unit:

[0077] First, determine whether a fault may occur based on the busbar differential protection criteria at the branch:

[0078]

[0079] Among them, Represents the power frequency variation current of the i-th branch; I op.min Indicates the minimum operating current of the busbar longitudinal differential protection, K res The braking coefficient of the differential protection including the feedback current is expressed as the braking coefficient. If the above formula is satisfied, it is considered that the system may have a fault and the next judgment is made. Otherwise, it is considered that there is no fault.

[0080] Then judge the value of the current and its direction:

[0081] If I>I set , D irect<0, it is determined that the branch has a dead zone fault, otherwise it is considered that there is no fault;

[0082] Among them, I set is the set criterion current, D irect is the direction of current, where the current flowing through the current transformer is positive when it flows from the bus to the load, and negative when it flows from the bus to the load.

[0083] Step 3: The slave unit controls the circuit breaker at the branch according to the instruction.

[0084] A computer device comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following steps are implemented:

[0085] Step 1: The slave unit collects the current and voltage information of each branch;

[0086] Step 2: The main control unit determines whether a dead zone fault occurs based on the collected information and sends corresponding instructions to the corresponding slave unit;

[0087] Step 3: The slave unit controls the circuit breaker at the branch according to the instruction.

[0088] A computer storable medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the computer program implements the following steps:

[0089] Step 1: The slave unit collects the current and voltage information of each branch;

[0090] Step 2: The main control unit determines whether a dead zone fault occurs based on the collected information and sends corresponding instructions to the corresponding slave unit;

[0091] Step 3: The slave unit controls the circuit breaker at the branch according to the instruction.

[0092] The present invention utilizes a novel protection algorithm and a brand-new bus solution. When a dead-zone fault occurs in a load or power supply with feedback current, the dead-zone fault is accurately located, and a tripping command is sent to the branch circuit breaker where the dead-zone fault occurs, thereby tripping the circuit breaker and eliminating the dead-zone fault.

[0093] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A dead zone fault identification system suitable for a feeder automation system, characterized in that: It includes a main control unit and each sub-unit; The slave units are arranged at each branch of the power distribution network bus, and each of the slave units is connected to the main control unit via an EtherCAT bus; The slave unit collects the current and voltage information of each branch and transmits the collected information to the main control unit. The main control unit determines whether a dead zone fault occurs based on the collected information and transmits corresponding instructions to the corresponding slave unit according to the fault situation. The slave unit executes the control branch circuit breaker on and off according to the instructions. The main control unit determines whether a dead zone fault occurs based on the collected information, specifically: First, determine whether a fault may occur based on the busbar differential protection criteria at the branch: ； Among them, Indicates the The power frequency variation current of each branch; Indicates the minimum operating current of the busbar longitudinal differential protection. It represents the braking coefficient of the differential protection including feedback current. If the above formula is satisfied, it is considered that the system may have a fault and the next judgment is made. Otherwise, it is considered that there is no fault. Then judge the value of the current and its direction: If satisfied , , then it is determined that the branch has a dead zone fault, otherwise it is considered that there is no fault; in, is the set criterion current, is the direction of current, where the current flowing through the current transformer is positive when it flows from the bus to the load, and negative when it flows from the bus to the load.

2. The dead zone fault identification system applicable to the feeder automation system according to claim 1, characterized in that: When the main control unit determines that a dead zone fault occurs in the system, it sends an instruction to the slave unit corresponding to the faulty branch line, and the slave unit controls the circuit breaker to trip according to the instruction.

3. The dead zone fault identification system applicable to the feeder automation system according to claim 1, characterized in that: The sub-machine unit includes a power supply, an MCU main control chip, an EtherCAT ESC control chip, an Ethernet interface, a WIFI module, a GPRS module, a USB interface, a voltage sampling module, a current sampling module and a switch execution unit; The MCU main control chip is respectively connected to the EtherCAT ESC control chip, WIFI module, GPRS module, USB interface, voltage sampling module, current sampling module and switch execution unit. The power supply supplies power to each part of the slave unit. The EtherCAT ESC control chip is used to connect to the host computer through the Ethernet interface and connect each slave unit to the main control unit; the voltage sampling module and current sampling module are used to collect current and voltage information at each branch of the distribution network bus.

4. The dead zone fault identification system applicable to the feeder automation system according to claim 1, characterized in that: The communication between the main control unit and each slave unit adopts EtherCAT. In the EtherCAT network, the main control unit sends data to all slave units through a single Ethernet frame. Then each slave unit processes the data in real time after receiving it and passes the result to the next slave unit, and finally returns it to the main control unit. That is, the main control unit quickly obtains the switch status, sampled voltage and current values ​​of each circuit breaker from the slave units through the EtherCAT protocol and executes the protection judgment. If the sampled value of a slave unit exceeds the set value, the main control unit immediately sends a downlink message to the slave unit. The message data traverses all slave units. The slave unit extracts or inserts data at the specified position in the EtherCAT data frame according to the downlink message EtherCAT frame header, and transmits the message to the next slave unit at the same time. After reading the data, the designated slave unit executes the main control unit instruction, outputs the switching value, and disconnects the circuit breaker. When the message reaches the last slave unit in the system's logical position, the slave unit returns the processed message as an uplink message to the main control unit.

5. The dead zone fault identification system applicable to the feeder automation system according to claim 4, characterized in that: The EtherCAT data frame includes an Ethernet frame header, a data packet and an FSC frame check sequence. The Ethernet frame header includes a source address, a destination address and an Ethernet frame type. The EtherCAT Ethernet frame type is Ox88A4. The transmitted data includes a data length and several sub-messages. Each sub-message has a logical address, an offset address and read and write data, and is used to transmit I / O values, application layer protocols and mailbox communication data. The frame check sequence verifies whether the data is wrong through a 32-bit CRC algorithm. Each data packet includes a data packet header, data and a counter.

6. The dead zone fault identification method applicable to a feeder automation system according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: The slave unit collects the current and voltage information of each branch; Step 2: The main control unit determines whether a dead zone fault occurs based on the collected information and sends corresponding instructions to the corresponding slave unit; Step 3: The slave unit controls the circuit breaker at the branch according to the instruction.

7. The dead zone fault identification method applicable to a feeder automation system according to claim 6, characterized in that: The main control unit in step 2 determines whether a dead zone fault occurs based on the collected information, specifically: First, determine whether a fault may occur based on the busbar differential protection criteria at the branch: ； Among them, Indicates the The power frequency variation current of each branch; Indicates the minimum operating current of the busbar longitudinal differential protection. It represents the braking coefficient of the differential protection including feedback current. If the above formula is satisfied, it is considered that the system may have a fault and the next judgment is made. Otherwise, it is considered that there is no fault. Then judge the value of the current and its direction: If satisfied , , then it is determined that the branch has a dead zone fault, otherwise it is considered that there is no fault; in, is the set criterion current, is the direction of current, where the current flowing through the current transformer is positive when it flows from the bus to the load, and negative when it flows from the bus to the load.

8. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 6 to 7 are implemented.

9. A computer storable medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 6 to 7 are implemented.

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