Anti-pumping circuit of relay protection device

An anti-pumping circuit prevents repeated closing of a circuit breaker, ensuring it closes only once per command to protect equipment and maintain system safety.

Purpose of Anti-Pumping Circuit

The anti-pumping circuit is an auxiliary protection mechanism integrated into circuit breaker control systems. Its primary function is to prevent multiple closing operations of a circuit breaker when a fault persists or when the closing command is continuously applied. Without this protection, repeated closing can damage the breaker's mechanical parts, trip coils, or associated equipment, and may create unsafe conditions in the power system .

Working Principle

The anti-pumping relay or coil operates using a combination of normally open (NO) and normally closed (NC) contacts:

• When the circuit breaker is open, the anti-pumping relay's NC contact allows the closing command to energize the breaker's closing coil.
• Once the breaker closes, the auxiliary contacts of the breaker change state, energizing the anti-pumping coil.
• Energizing the anti-pumping coil opens the NC contact in the closing path, disconnecting the closing coil from the control circuit.
• This ensures that even if the operator continues to hold the close button or a continuous signal is sent, the breaker cannot reclose until the command is reset .

Circuit Configuration

In a typical DC control circuit:

• The TNC (Trip-Neutral-Close) switch or remote/local control switch sends the closing pulse.
• The anti-pumping relay is connected in series with the closing coil and in parallel with auxiliary NO contacts.
• During normal operation, the NC contact of the anti-pumping relay allows the first closing pulse to reach the breaker.
• After the breaker closes, the relay opens its NC contact, blocking further closing attempts until the system is reset .

Applications

Anti-pumping circuits are essential in medium and high-voltage circuit breakers, including:

• Generator and alternator breakers
• Grid and feeder breakers
• Switchgear protecting transformers and motors They are mandatory in modern power systems to prevent repeated breaker operations, which could otherwise lead to equipment damage, unsafe voltage/current conditions, or failure of the breaker's trip and close coils .

Key Benefits

• Ensures single closing per command
• Protects breaker mechanical and electrical components
• Enhances system reliability and safety
• Prevents damage during persistent faults or operator errors In summary, the anti-pumping circuit is a critical interlock in relay protection devices, safeguarding circuit breakers from repeated operations and maintaining stable, safe power system operation .