CN112255573B - A single-phase-to-earth fault processing method for a neutral point unearthed system - Google Patents

Abstract

The invention provides a single-phase earth fault processing method of a neutral point ungrounded system, which judges whether an earth fault occurs or not through the out-of-limit of a secondary side opening triangular voltage signal and a zero sequence current signal of a voltage transformer, further judges the specific fault type, controls a bus fault phase quick switch to execute different operation instructions according to different fault conditions, effectively transfers fault current and ensures the safety of equipment and workers.

Description

A single-phase ground fault processing method for neutral point ungrounded system

technical field

The invention belongs to the technical field of power fault processing, and in particular relates to a single-phase ground fault processing method for a neutral point ungrounded system.

Background technique

The ground fault is one of the most common faults in the power system, and it is an important step to ensure the safety and reliability of the power system to quickly and accurately determine the specific fault type and fault line and take further maintenance measures.

The present invention proposes a single-phase grounding fault processing method for a neutral point ungrounded system, which judges whether a grounding fault occurs through the triangular voltage signal of the secondary side opening of the voltage transformer and the zero-sequence current signal exceeding the limit, thereby improving fault discrimination The quick action; further judge the specific fault type, control the fast switch of the bus fault phase according to different fault conditions to execute different operation instructions, effectively transfer the fault current, and ensure the safety of equipment and staff.

Contents of the invention

The invention provides a single-phase ground fault processing method for a neutral point ungrounded system, which can quickly and accurately determine the fault type and line, and effectively transfer the fault current through a fast switch.

The present invention is specifically a single-phase ground fault processing method for a neutral point ungrounded system, and the fault processing method includes the following steps:

Step (1): Collect the triangular voltage signal of the secondary side opening of the voltage transformer, the zero-sequence current signal of the line, the three-phase voltage signal, and the three-phase current signal;

Step (2): judging whether the triangular voltage signal of the secondary side opening of the voltage transformer is greater than the voltage reference value, if so, proceed to step (3); if not, return to step (1);

Step (3): Judging whether all the zero-sequence current signal mutations occur, if so, a single-phase ground fault occurs, and enter step (4); if not, return to step (1);

Step (4): Judging whether one phase voltage is close to zero, and the other two phase voltages are close to line voltage, if so, metal grounding occurs, and the phase voltage is close to zero phase is a faulty phase, enter step (6); if not, enter step ( 5);

Step (5): Determine whether the voltage of one phase is lower than the voltage of the other two phases, and the voltage of the previous phase of the phase with the lower voltage is greater than the voltage of the other two phases. If so, a small resistance single-phase grounding fault occurs, and the phase with the lower voltage is the fault phase , enter step (6); if not, a large resistance single-phase ground fault occurs, and the phase after the phase with the largest voltage is the fault phase, enter step (6);

Step (6): Controlling the fast switching action of the busbar of the faulty phase to close;

Step (7): Judging whether there is a certain line a, the zero-sequence current signal on the line a is opposite to the zero-sequence current signal of all other lines, and the zero-sequence current amplitude of the line a is greater than that of other lines line, and the zero-sequence current direction of the line a changes before and after the fast switching action of the bus, if so, the line a is a faulty line, and enters step (8); if not, the line a is a non-faulty line, enters the step (9);

Step (8): Controlling the busbar fast switch of the faulty phase to no longer open, enter step (10);

Step (9): the bus quick switch for controlling the fault phase is no longer disconnected, and enters step (10);

Step (10): collecting the triangular voltage signal of the secondary side opening of the voltage transformer and the zero-sequence current signal of the line;

Step (11): Judging whether the triangular voltage signal of the secondary side opening of the voltage transformer is greater than the voltage reference value, if so, proceed to step (12); if not, a temporary ground fault, and the fault has been eliminated, proceed to step (15) ;

Step (12): judging whether all the zero-sequence current signal mutations occur, if so, a permanent ground fault, proceed to step (13); if not, a temporary ground fault, and the fault has been eliminated, proceed to step (15);

Step (13): controlling the fast switching action of the busbar of the faulty phase to close;

Step (14): controlling the fast switching action closing of the fault line;

Step (15): Determine whether to continue detection, if yes, return to step (1); if not, end.

The bus fast switch of the fault phase will close quickly after receiving the closing signal, and transfer the ground current at the fault point to the bus, so that the fault arc is extinguished and the arc re-ignition is suppressed.

Compared with the prior art, the beneficial effect is that the fault handling method judges whether a ground fault occurs through the triangular voltage signal of the secondary side opening of the voltage transformer and the zero-sequence current signal, and then further judges the specific fault According to different fault conditions, the fast switch of the bus bar of the fault phase is controlled to execute different operation instructions, effectively transfer the fault current, and ensure the safety of equipment and staff.

detailed description

The specific implementation of a single-phase ground fault processing method for a neutral point ungrounded system of the present invention will be described in detail below.

Troubleshooting method of the present invention comprises the following steps:

First, judge whether there is a fault: collect the triangular voltage signal of the secondary side of the voltage transformer, the zero-sequence current signal of the line, the three-phase voltage signal, and the three-phase current signal; judge whether the triangular voltage signal of the secondary side of the voltage transformer is greater than the voltage reference value, if not, continue to collect signals; if so, judge whether all zero-sequence current signal mutations occur, if so, single-phase ground fault occurs; if not, continue to collect signals.

Further, it is judged whether one phase voltage is close to zero, and the other two phase voltages are close to line voltage. If there is a metal grounding, and the phase voltage is close to zero, the phase is a faulty phase, and the fast switching action of the bus bar of the faulty phase is controlled to close; if not, judge Whether the voltage of one phase is lower than the voltage of the other two phases, and the voltage of the previous phase of the phase with the lower voltage is greater than the voltage of the other two phases, if so, a small resistance single-phase ground fault occurs, the phase with the lower voltage is the fault phase, and the bus bar of the fault phase is controlled Fast switching action to close; if not, a large resistance single-phase ground fault occurs, the phase after the phase with the largest voltage is the fault phase, and the bus bar that controls the fault phase is closed by fast switching action.

Judging whether the direction of the zero-sequence current signal on a certain line is opposite to that of all other lines, and the amplitude is greater than that of other lines, and the direction of the zero-sequence current changes before and after the fast switching of the busbar. If so, the line is a faulty line, The bus quick switch controlling the faulty phase is no longer open; if not, the line is a non-faulty line, and the bus quick switch controlling the faulty phase is no longer disconnected.

Further, collecting the triangular voltage signal of the secondary side opening of the voltage transformer and the zero-sequence current signal of the line; judging whether the triangular voltage signal of the secondary side opening of the voltage transformer is greater than the voltage reference value, if not, a temporary ground fault, and the fault has been eliminated; If so, judge whether there is a sudden change in all zero-sequence current signals. If yes, there is a permanent ground fault, and the fast switching action of the busbar that controls the fault phase is closed, and the fast switching action of the fault line is closed; if not, the ground fault is temporary, and the fault has been eliminated.

The method of judging the occurrence of single-phase ground fault by using the triangular voltage signal and the zero-sequence current signal at the secondary side of the voltage transformer to exceed the limit saves the extraction and calculation process of feature quantities, and improves the quickness of fault discrimination.

The bus fast switch of the fault phase will close quickly after receiving the closing signal, and transfer the ground current at the fault point to the bus, so that the fault arc is extinguished and the arc re-ignition is suppressed.

Finally, it should be noted that the combination of the above embodiments only illustrates the technical solution of the present invention rather than limiting it. Those of ordinary skill in the art should understand that those skilled in the art can modify or equivalently replace the specific embodiments of the present invention, but these modifications or changes are within the protection scope of the pending claims.

Claims (2)

1. A single-phase earth fault processing method of a non-grounded neutral system is characterized by comprising the following steps:

step (1): collecting a secondary side opening triangular voltage signal, a line zero sequence current signal, a three-phase voltage signal and a three-phase current signal of a voltage transformer;

step (2): judging whether the secondary side opening triangular voltage signal of the voltage transformer is larger than a voltage reference value or not, and if so, entering the step (3); if not, returning to the step (1);

and (3): judging whether all the zero sequence current signals are suddenly changed or not, if so, generating a single-phase earth fault, and entering the step (4); if not, returning to the step (1);

and (4): judging whether a phase voltage is close to zero or not, and the other two phases of voltages are close to the line voltage, if so, the metal grounding occurs, and the phase voltage close to zero is a fault phase, and entering the step (6); if not, entering the step (5);

and (5): judging whether a phase voltage is smaller than the voltages of the other two phases and the previous phase voltage of the phase with small voltage is larger than the voltages of the other two phases, if so, generating a single-phase earth fault with small resistance and taking the phase with small voltage as a fault phase, and entering the step (6); if not, a large-resistance single-phase earth fault occurs, the latter phase of the phase with the maximum voltage is a fault phase, and the step (6) is carried out;

and (6): controlling the bus fast switch of the fault phase to act closing;

and (7): judging whether a certain line a appears, wherein the direction of the zero sequence current signal on the line a is opposite to that of the zero sequence current signals of all other lines, the amplitude of the zero sequence current of the line a is larger than that of other lines, and the direction of the zero sequence current of the line a is changed before and after the quick bus switching action, if so, the line a is a fault line, and entering the step (8); if not, the line a is a non-fault line, and the step (9) is carried out;

and (8): controlling the bus fast switch of the fault phase not to be switched off, and entering the step (10);

and (9): controlling the bus fast switch of the fault phase not to be disconnected, and entering the step (10);

step (10): collecting a triangular voltage signal of a secondary side opening of the voltage transformer and a zero sequence current signal of the line;

step (11): judging whether the secondary side opening triangular voltage signal is larger than a voltage reference value or not, and if so, entering the step (12); if not, the temporary earth fault is eliminated, and the step (15) is entered;

step (12): judging whether all the zero sequence current signals are mutated or not, if yes, carrying out permanent ground fault, and entering the step (13); if not, the temporary earth fault is eliminated, and the fault is eliminated, go to step (15);

step (13): controlling the bus fast switch of the fault phase to close;

step (14): controlling the quick switch action of the fault line to close;

step (15): judging whether to continue detection, if so, returning to the step (1); if not, the process is ended.

2. The method as claimed in claim 1, wherein the bus fast switch of the fault phase is closed rapidly after receiving a closing signal, and ground current at the fault point is transferred to the bus, so that the fault arc is extinguished and arc reignition is suppressed.