Line protection CT disconnection locking method and system under power flow reverse condition and medium

Abstract

The invention discloses a line protection CT disconnection locking method and system under a power flow reverse condition, and a medium. The method comprises the steps: carrying out the fault judgmentaccording to the power flow reverse direction of an A-phase line, a B-phase line and a C-phase line, and obtaining a fault judgment result; performing OR logic operation on the fault judgment result,the monitoring result of the first zero-sequence current monitoring logic and the output fault state self-hold logic judgment result, and performing broadening to obtain an output fault state self-hold logic judgment result; and negating the output fault state self-hold logic judgment result, performing AND logic operation on the negated result and the monitoring result of the second zero-sequence current monitoring logic, and delaying the operation result to serve as a CT disconnection control signal. The self-hold logic for zero-sequence current compensation is included, the locking effectcan be achieved in the whole fault period after power flow is reversed, and it is avoided that line protection is locked by CT when zero-sequence current is between a CT disconnection action value anda zero-sequence overcurrent protection action value under the high-resistance grounding fault.

Description

technical field [0001] The invention relates to the field of substation relay protection, in particular to a line protection CT (Current Transformer, current transformer) disconnection blocking method, system and medium under the condition of reverse flow. Background technique [0002] In recent years, several 110kV line high-resistance grounding faults occurred in Hunan Power Grid, which led to the corresponding 220kV main transformer overstepping tripping accidents, resulting in certain power load losses and negative impacts. When a high-impedance ground fault occurs on the line, the system will generate zero-sequence current, but the amplitude is small, which may be between the zero-sequence overcurrent protection action value and the CT disconnection action value, resulting in CT disconnection blocking line protection, and then in Subsequent fault characteristics aggravate, causing the main transformer zero-sequence overcurrent protection to leapfrog trip. [0003] The ...

AI Technical Summary

Problems solved by technology

However, under high-impedance grounding faults, the fault current is small, and the zero-sequence overcurrent protection action condition that responds to the fault state cannot be reached, which makes the CT disconnect and block the line protection by mistake.

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