A method for determining ground fault direction in an adaptive power supply mode of active distribution network

Abstract

A method for determining the direction of a ground fault in an active distribution network with an adaptive power supply mode belongs to the field of ground fault protection for distribution networks. The method includes a distribution switch and is characterized by the following steps: Step a, the distribution switch collects electrical quantity characteristics on the line in real time; Step b, the distribution switch determines whether a ground fault has occurred in the line. If a ground fault has occurred, step c is executed; if no fault has occurred, the method returns to step a; Step c, the distribution switch calculates the zero-sequence impedance at the time of the fault; Step d, the distribution switch determines the power supply mode of the line and identifies the fault direction; Step e, the distribution switch executes a protection action based on the power supply mode and fault direction identification results. This method for determining the direction of a ground fault in an active distribution network with an adaptive power supply mode can detect the power supply direction of both traditional distribution networks and active distribution networks, and implement ground fault direction determination and protection actions in an adaptive power supply mode.

Description

Technical Field

[0001] The invention discloses a ground fault direction determination method for an active distribution network adaptive power supply mode, belonging to the field of distribution network ground fault protection. Background Art

[0002] Ground faults in distribution networks are an important factor affecting the safe operation of power grids and the reliability of power supply. Reasonable relay protection configuration and setting can quickly and effectively isolate faults, minimize the scope of fault outages, and improve the safety and reliability of power supply.

[0003] Transient directional protection is currently the most widely used ground fault protection method in the field. When a ground fault occurs on a distribution network line, the upstream switch closest to the fault (on the power supply side of the line system) is actuated, enabling selective and localized ground fault clearance. Since most lines have interconnecting lines, when a line is powered by an interconnecting line, the power supply direction changes, and the switches that require actuation must be adjusted based on the operating mode. Distribution switches equipped with transient directional protection typically determine the power supply direction by detecting the direction of the load current and adjust their switching operation accordingly.

[0004] In recent years, with the large-scale access of distributed renewable energy sources such as wind power and photovoltaics to the distribution network, the load current direction of the active distribution network is related to the renewable energy power generation and section load. Therefore, the distribution switch can no longer determine the power supply direction by detecting the load current direction, resulting in the protection failing to operate normally. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a method for determining the direction of ground faults in an adaptive power supply mode of an active distribution network, which can detect the power supply direction of a traditional power distribution network and an active power distribution network, and realize ground fault direction determination and protection action in an adaptive power supply mode.

[0006] The technical solution adopted by the present invention to solve the technical problem is: the ground fault direction determination method of the active power distribution network adaptive power supply mode includes a distribution switch, which is characterized by comprising the following steps:

[0007] Step a: The distribution switch collects electrical quantity characteristics on the line in real time;

[0008] Step b, the distribution switch determines whether a ground fault occurs in the line. If a ground fault occurs, step c is executed; if no fault occurs, step a is returned to;

[0009] Step c, the distribution switch calculates the zero-sequence impedance during a fault;

[0010] Step d: The distribution switch determines the power supply mode of the line where it is located and identifies the fault direction;

[0011] In step e, the distribution switch performs a protection action according to the power supply mode of the line to which it is located and the fault direction identification result.

[0012] Preferably, in step a, the electrical quantity characteristics collected include: three-phase voltage, zero-sequence voltage, three-phase current, and zero-sequence current on the line.

[0013] Preferably, in step d, the power supply mode of the line is determined based on the zero-sequence impedance downstream of the switch during normal operation and the zero-sequence impedance during a fault:

[0014] in, is the zero-sequence impedance downstream of the switch during normal operation, is the zero-sequence impedance during fault, when k<K set When it is forward power supply, otherwise it is reverse power supply, K set Preset values ​​for the power distribution switch.

[0015] Preferably, in step e, the distribution switch first determines whether the fault point is within the boundary. When the line is powered in the forward direction and the fault is an within-boundary fault, the distribution switch performs a tripping action; when the line is powered in the reverse direction and the fault is a non-within-boundary fault, the distribution switch performs a tripping action; when the line is powered in the forward direction and the fault is a non-within-boundary fault, or when the line is powered in the reverse direction and the fault is an within-boundary fault, the distribution switch does not perform a tripping action.

[0016] Preferably, the distribution switch preset value K set The value of is 0.8.

[0017] Preferably, the zero-sequence impedance downstream of the switch during normal operation is The calculation formula is:

[0018]

[0019] Where ω is the angular frequency, ω=2πf, f=50Hz, C l.d is the line capacitance downstream of the switch.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] In the ground fault direction determination method of the active distribution network adaptive power supply mode, the power supply directions of the traditional distribution network and the active distribution network can be detected, and the ground fault direction determination and protection action of the adaptive power supply mode can be realized.

[0022] By using the ground fault direction discrimination method in the adaptive power supply mode of the active distribution network, the changes in the line power supply mode can be adapted, the fault direction can be identified, and the corresponding protection action can be executed to achieve correct protection action when the power supply mode changes during the operation of the distribution network and accurately isolate the fault point. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The flowchart of the ground fault direction determination method for the adaptive power supply mode of the active distribution network is shown in FIG.

[0024] Figure 2 This is a power distribution circuit diagram of a power distribution switch with adaptive power supply mode. DETAILED DESCRIPTION

[0025] Figures 1-2 The best embodiment of the present invention is shown below in conjunction with the attached Figures 1-2 The present invention is further described.

[0026] like Figure 1 As shown, a method for determining the direction of a ground fault in an active power distribution network adaptive power supply mode includes the following steps:

[0027] Step 1001, start;

[0028] like Figure 2 The diagram shows a power distribution circuit diagram of a conventional power distribution switch with adaptive power supply. The distribution circuit can be powered by either power source A or power source B. Circuit breakers QF1 and QF2 are installed, respectively, along with distribution switches Q1 through Q5. Q3 is a tie switch. When power source A is supplying forward power, tie switch Q3 is open. When power source B is supplying reverse power, tie switch Q3 is closed.

[0029] Step 1002, calculating the zero-sequence impedance downstream of the switch during normal operation;

[0030] The distribution switch is based on the capacitance C of the line (including the connecting line) downstream of the switch. l.d Calculate the downstream zero-sequence impedance during normal operation

[0031]

[0032] Wherein, ω is the angular frequency, ω = 2πf, f = 50 Hz.

[0033] Step 1003, determine whether there is a fault in the line;

[0034] The distribution switch of the adaptive power supply mode collects the three-phase voltage, zero-sequence voltage, three-phase current and zero-sequence current on the line in real time to determine whether a fault occurs in the line. If a fault occurs (such as Figure 2 Between the middle switch Q1 and the switch Q2), execute step 1004. If no fault occurs, return to execute this step.

[0035] Step 1004, calculating the zero-sequence impedance during the fault;

[0036] After detecting a ground fault, the line protection device uses the zero-sequence current at the time of the fault to and zero sequence voltage Calculate zero-sequence impedance

[0037] Step 1005, determining the power supply mode of the line where the line power distribution switch is located;

[0038] Comparison of zero-sequence impedance of distribution switches in adaptive power supply mode during faults and downstream zero-sequence impedance The calculation results are based on the formula: Determine the power supply mode of the line:

[0039] When k<K set When it is forward power supply, otherwise it is reverse power supply, K set K is the preset value of the line protection device. set =0.8.

[0040] Step 1006, identifying the fault direction and executing protection action;

[0041] The distribution switch with adaptive power supply mode first determines whether the fault point is within the boundary. When the line is supplying power in the forward direction and the fault is within the boundary, the distribution switch performs a tripping action; when the line is supplying power in the reverse direction and the fault is not within the boundary, the distribution switch performs a tripping action; when the line is supplying power in the forward direction and the fault is not within the boundary, or when the line is supplying power in the reverse direction and the fault is within the boundary, the distribution switch does not perform a tripping action.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for determining the direction of a ground fault in an active power distribution network in an adaptive power supply mode, comprising a distribution switch, characterized in that: The steps include: Step a: The distribution switch collects electrical quantity characteristics on the line in real time; Step b, the distribution switch determines whether a ground fault occurs in the line. If a ground fault occurs, step c is executed; if no fault occurs, step a is returned to; Step c, the distribution switch calculates the zero-sequence impedance during a fault; Step d: The distribution switch determines the power supply mode of the line where it is located and identifies the fault direction; Step e: The distribution switch performs a protection action according to the power supply mode of the line to which it is connected and the fault direction identification result; In step a, the electrical quantity characteristics collected include: three-phase voltage, zero-sequence voltage, three-phase current, and zero-sequence current on the line; In step d, the power supply mode of the line is determined based on the zero-sequence impedance downstream of the switch during normal operation and the zero-sequence impedance during a fault: in, is the zero-sequence impedance downstream of the switch during normal operation, is the zero-sequence impedance during fault, when k<K set When it is forward power supply, otherwise it is reverse power supply, K set Preset values ​​for distribution switches; In step e, the distribution switch first determines whether the fault point is within the boundary. When the line is supplying power in the forward direction and the fault is within the boundary, the distribution switch performs a tripping action; when the line is supplying power in the reverse direction and the fault is not within the boundary, the distribution switch performs a tripping action; when the line is supplying power in the forward direction and the fault is not within the boundary, or when the line is supplying power in the reverse direction and the fault is within the boundary, the distribution switch does not perform a tripping action. Distribution switch preset value K set The value of is 0.

8.

2. The method for determining the ground fault direction in an active power distribution network adaptive power supply mode according to claim 1, characterized in that: Zero-sequence impedance downstream of the switch during normal operation The calculation formula is: Where ω is the angular frequency, ω=2πf, f=50Hz, C l.d is the line capacitance downstream of the switch.

Images