What is the function of distance relay in auto reclosure?
The distance relay’s major function in the setup of auto-reclosure is to detect & identify faults on the transmission line, & then to initiate the auto-reclosure procedure.
This is the primary function of the distance relay. It assesses if a problem is momentary (transient) and can be successfully reclosed, or whether it is a permanent fault that requires a lockout to be implemented.
In order to provide a more in-depth explanation:
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Detection of Faults
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Classification of Fault
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Auto Reclosure Initiation
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Circuit Breaker Control
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Lockout
Detection of Faults
Between the relay position and the fault location, the distance relay is responsible for measuring the impedance, which includes both resistance and reactance. Through the use of this measurement, the distance between the relay and the fault can be determined.
Classification of Fault
The distance relay determines whether the fault is a transient or permanent fault based on impedance measurement as well as additional factors.
Auto Reclosure Initiation
When the problem is determined to be a temporary fault, the distance relay will send a signal to commence the auto-reclosure sequence. This occurs when the fault is classed as a transient fault.
Circuit Breaker Control
The auto-reclosure procedure consists of activating the circuit breaker, waiting for a predetermined “dead time” to enable the fault to clear (if it is a transient fault), and then closing the breaker once more in order to re-energize the line.
Lockout
In case the failure is determined to be permanent, the distance relay will normally send out a lockout signal, which will prohibit any further efforts at shutting down the system automatically.
In effect, the distance relay functions as a “smart” switch, which enables the auto-reclosure method to automatically restore the electric power to transmission line after the temporary faults while also safeguarding the system from faults that are permanent.
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