CN113765056B

CN113765056B - Single-phase grounding processing method

Info

Publication number: CN113765056B
Application number: CN202011451441.5A
Authority: CN
Inventors: 薛占钰; 丁同同; 刘建伟
Original assignee: Baoding Yuxin Electrical Technology Co ltd
Current assignee: Baoding Yuxin Electrical Technology Co ltd
Priority date: 2020-12-12
Filing date: 2020-12-12
Publication date: 2022-09-02
Anticipated expiration: 2040-12-12
Also published as: CN113765056A; WO2022121779A1

Abstract

The invention discloses a processing method of single-phase grounding, after the single-phase grounding occurs, a non-fault phase or a neutral point is connected with the ground to form a closed loop with the grounding phase and generate current; then, the controlled switch is used for detecting the current duration, and the current duration triggered and cut off by the controlled switch at the downstream of the power supply direction is set to be shorter than the current duration triggered and cut off by the controlled switch at the upstream of the power supply direction; and when one controlled switch is cut off when a trigger condition is met, stopping the non-fault phase from being grounded. The method can quickly position the single-phase earth fault point interval, can automatically, quickly and accurately remove the fault, can well improve the processing quality of the single-phase earth fault, and improves the power supply safety.

Description

Single-phase grounding processing method

Technical Field

The invention relates to the field of power system fault processing, in particular to a processing method of a non-effective grounding power supply system after a single-phase grounding fault occurs.

Background

When a single-phase grounding occurs in a non-effective grounding system (such as a three-phase power supply system), the following steps are generally performed: 1. searching a fault line; 2. stopping a fault line; 3. searching and eliminating fault points; 4. and recovering power supply. The processing method has the defects of slow fault point searching, long power failure time, large power failure area and the like, and the single-phase grounding duration is long before the fault is eliminated, so that the method has danger to the outside. In order to solve this problem, the utility model CN 202815149U provides an asymmetric current source, by which a non-fault phase can be grounded and form a short circuit with a ground phase to generate a short-circuit current, and then the current detector can display the loop of the short-circuit current to quickly indicate the fault point. However, when the method is used, the grounding resistance during single-phase grounding is difficult to predict, the short-circuit current is too small or even difficult to detect when the grounding resistance is too large, and the short-circuit current is too large when the grounding resistance is too small, so that a series resistor is needed to prevent damage to a line, and the practicability of the method is greatly reduced. An improved idea is to make the short-circuit current have a short duration, so that there is no need to serially connect a current-limiting resistor and no damage to the line, and to make the short-circuit current as large as possible and easy to detect without serially connecting a current-limiting resistor, thereby enhancing the utility of the above method (for example, CN 110634713A, CN 110531822A, CN 209822486U is a patent application proposed for making short-circuit current). Even so, the above method only helps to indicate a single-phase earth fault point, and the actual search for the fault point is still time-consuming, and the long-lasting hazard of the single-phase earth fault still exists. How to automatically and rapidly cut off a single-phase grounding fault point to form an ineffective grounding system, reduce the area of power failure as much as possible, and shorten the duration of single-phase grounding so as to reduce the damage is a technical problem to be solved in the field.

Disclosure of Invention

The invention aims to provide a single-phase grounding processing method which can quickly position a single-phase grounding fault point interval, can automatically, quickly and accurately remove faults, can well improve the processing quality of single-phase grounding faults and improve the power supply safety.

In order to achieve the purpose, the invention adopts the following technical scheme:

a single-phase grounding processing method is characterized in that a plurality of controlled switches are distributed on a non-effective grounding system, the controlled switches can automatically cut off a circuit according to current duration, and the processing is carried out according to the following steps:

step (a): after single-phase grounding occurs, a non-fault phase or a neutral point is connected with the earth to form a closed loop with the grounding phase and generate current;

step (b): detecting the current duration by using the controlled switch, and setting the current duration triggered and cut off by the controlled switch at the downstream of the power supply direction to be shorter than the current duration triggered and cut off by the controlled switch at the upstream of the power supply direction; and when one controlled switch is cut off when the trigger condition is reached, stopping the non-fault phase from being grounded.

Preferably, in the step (a), the non-fault phase is switched on and off with the ground through a power electronic switch.

Preferably, the power electronic switch is an insulated gate bipolar transistor.

Preferably, before the non-faulted phase is switched on to ground, the non-faulted phase is selected by: detection of 3U by a Voltage Transformer ₀ After the single-phase earth fault is sensed to be out of limit, any two phases are sequentially connected with the ground through a switch and then disconnected, and one phase with larger current through the switch when the two phases are connected with the ground is selected as the non-fault phase.

Preferably, a grounding point is selected from the non-fault phase close to the power supply side of the first controlled switch closest to the power supply to achieve connection with the ground, and the controlled switch is set to automatically cut off the line when the current duration of any phase reaches a preset value.

Preferably, the non-effective grounding system is a two-phase power supply system or a three-phase power supply system.

Preferably, in the step (a), a current-limiting resistor is connected in series in the closed loop.

The invention has the beneficial effects that: after the single-phase earth fault occurs, a non-fault phase or a neutral point is grounded, an earth short circuit loop can be formed by the non-fault phase or the neutral point and the grounded fault phase, short-circuit current is generated, the current can be detected by a controlled switch on a line, and the controlled switch can cut off the controlled switch closest to the upper end of the single-phase earth fault point according to the detected current duration and the preset trigger current-cutting duration, so that the single-phase earth fault is automatically isolated.

Drawings

FIG. 1 is a schematic wiring diagram of an embodiment of the method of the present invention.

Detailed Description

The invention will be further illustrated by the following specific embodiments in conjunction with the drawings in which:

the three-phase power system is a common non-effective grounding system, a plurality of outgoing lines are arranged on a bus of the three-phase power system, a plurality of controlled switches are arranged on the outgoing lines, the controlled switches can detect currents on the phase lines, the three-phase lines can be cut off when the duration of the current passing through any phase reaches a preset value, or the three-phase lines can be cut off when the duration of the current passing through any two phases reaches the preset value. In a specific embodiment of the controlled switch, the controlled switch includes a control unit, a current detection unit and an execution unit, the current detection unit can respectively detect each phase current of the three-phase line, the control unit compares the time length detected by the current detection unit with a preset value, and can set the current time length of any phase or the current time lengths of any two phases to reach the preset value to send a signal to the execution unit to cut off the three-phase line. For the preset value of the duration of the current triggering the cut-off, the preset value of the controlled switch at the downstream of the power supply direction is shorter than the preset value at the upstream of the power supply direction, namely, the controlled switch is relatively closer to the power supply, and the controlled switch at the downstream of the power supply direction is relatively farther from the power supply, namely, the electric energy is emitted from the power supply and is transmitted from the upstream to the downstream. Or, when viewed from the upstream and downstream of the power supply direction, the shorter the preset value of the current duration for triggering and cutting off the controlled switch farther from the power supply, the easier the preset value of the current duration for triggering and cutting off the controlled switch is to reach the triggering condition first and then cut off the controlled switch.

In a specific embodiment, as shown in fig. 1, ABC three phases (or at least two phases thereof) are grounded above the first controlled switch 1 nearest to the power supply, and the phases A, B, C are connected to the ground through the controlled switches KA, KB and KC, respectively, when the duration of the current detected by each controlled switch to any phase reaches a preset value, the three-phase line is cut off. The voltage transformers installed at KA, KB and KC are used to collect the voltages of each phase (not shown in the drawings, refer to utility model patent CN 202815149U), the 3U0 is used to find out the single-phase grounding (for example, the C phase is single-phase grounded at point F), and then a non-fault phase (for example, phase a) is connected to the ground above the first controlled switch 1, so that an earth short circuit loop is created between the non-fault phase a above the switch KA and the power supply, fault phase C above point F, and ground, and a short circuit current can be generated, and the short circuit current only flows through the controlled switches above the single-phase ground fault point F (i.e., the controlled switch 3, the controlled switch 2 and the controlled switch 1) on the fault phase circuit, but not through the controlled switches below the single-phase ground fault point F (i.e., the controlled switch 4 and the controlled switch 5). Therefore, when the time length of the short-circuit current reaches the preset value of the nearest controlled switch 3 above the single-phase earth fault point, the switch can be automatically cut off, and the single-phase earth fault can be automatically removed. Although the controlled

switches

4 and 5 below the single-phase earth fault point F are short in current time for triggering to be cut off, they are not connected to the earth short circuit, and therefore, there is no cutting operation, and the controlled switches 2 and 1 are connected to the earth short circuit, but the current time for triggering to be cut off is longer than that of the controlled switch 3, and the triggering condition is not fulfilled, and therefore, they are not cut off. Therefore, the nearest controlled switch above the single-phase earth fault point F is cut off, automatic fault removal is guaranteed, and the minimum power failure area is guaranteed. The method is also applicable to two-phase systems or more than three-phase systems. In addition to grounding the non-faulted phase, the neutral point can also be grounded, and short circuit currents can also be generated.

In the above embodiment, the controlled switches are tripped in time, so as to prevent the current duration detected by the previous switch from reaching the trigger condition of the switch, thereby causing one or more controlled switches to be tripped undesirably, and thus causing unreasonable large-area power failure.

In one embodiment, power electronic switches, such as insulated gate bipolar transistors, are used. As described above, the occurrence of the single-phase ground fault can be detected by the PT and the non-fault phase can be determined, thereby implementing the non-fault phase switching-on. If it is determined that single-phase grounding occurs, but it cannot be accurately determined which two phases are non-fault phases, the non-fault phases can be determined by the following method: any two phases are grounded and disconnected sequentially through the electronic power switch, so that a current value can be obtained twice (wherein the current is small in one time), and then the phase with the large current value during grounding is selected as a non-fault phase to start grounding. Because if the current of one operation is small, the phase is a single-phase earth fault phase, the other operation is definitely a non-fault phase, the current ratio is large, and if the two operations are both non-fault phases, the non-fault phase with relatively large current is also selected.

For the condition that the impedance is small when the single phase is grounded, a current limiting resistor can be connected in series in the closed loop so as to prevent the system from being damaged by large current.

The above embodiments are only a few illustrations of the inventive concept and implementation, not limitations thereof, and the technical solutions without substantial changes are still within the scope of protection under the inventive concept.

Claims

1. A single-phase grounding processing method is characterized in that:

a plurality of controlled switches are distributed on a non-effective grounding power supply system, the controlled switches can automatically cut off a circuit according to current duration, and the method comprises the following steps:

a step (a): after single-phase grounding occurs, a non-fault phase or a neutral point is connected with the earth to form a closed loop with the grounding phase and generate current;

2. The method of claim 1, wherein in step (a), the non-faulted phase is switched on and off to ground by power electronic switches.

3. The method of claim 2, wherein the power electronic switch is an insulated gate bipolar transistor.

4. The method of claim 1 wherein the non-faulted phase is selected by, prior to switching the non-faulted phase to ground on: detection of 3U by a Voltage Transformer ₀ After the single-phase earth fault is sensed to be out of limit, any two phases are sequentially connected with the ground through a switch and then disconnected, and one phase with larger current through the switch when the two phases are connected with the ground is selected as the non-fault phase.

5. A method for processing single-phase grounding as claimed in any one of claims 1 to 4, characterized in that a grounding point is selected on the non-fault phase close to the power supply side of the first controlled switch closest to the power supply to realize the connection with the ground, and the controlled switch is set to automatically cut off the line when the current duration of any one phase reaches a preset value.

6. The method of claim 1, wherein the non-active ground power system is a two-phase power system or a three-phase power system.

7. The method of claim 1, wherein in step (a), a current limiting resistor is connected in series in the closed loop.