Overcurrent Secondary Protection Relays

Overcurrent secondary protection relays are protection relays that measure phase and earth currents from the secondary circuit of current transformers and give a trip command to the circuit breaker when the set threshold is exceeded. They are used in medium voltage cells and main distribution panels to protect transformers, motors, generators and power lines against short circuits and earth faults. The category includes the Entes CKR-93T, with three phase inputs and one earth measuring input and an 85-265 V AC/DC auxiliary supply. Choose the number of phase and earth inputs, the measuring input suited to the current transformer secondary value, the auxiliary supply voltage, the tripping characteristic and the output contacts according to your protection coordination calculation. A secondary relay does not interrupt the fault current itself; it passes the trip command to the circuit breaker's shunt trip coil, so it does not replace the circuit breaker.

Products

How to choose Overcurrent Secondary Protection Relays

Overcurrent secondary protection relays are protection relays that measure phase and earth currents from the secondary circuit of current transformers and give a trip command to the circuit breaker when the set threshold is exceeded. They are used in medium voltage cells and main distribution panels to protect transformers, motors, generators and power lines against short circuits and earth faults.

  • Separate overcurrent/leakage protection, motor starting and local isolation requirements.
  • Select rated current, pole count and breaking capacity (kA) from the installation calculation.
  • Match coil voltage, auxiliary contacts and tripping curve to the control circuit and load type.

Frequently asked questions

What is Overcurrent Secondary Protection Relays and where is it used?

Overcurrent secondary protection relays are protection relays that measure phase and earth currents from the secondary circuit of current transformers and give a trip command to the circuit breaker when the set threshold is exceeded. They are used in medium voltage cells and main distribution panels to protect transformers, motors, generators and power lines against short circuits and earth faults.

What should I compare when choosing Overcurrent Secondary Protection Relays?

Choose the number of phase and earth inputs, the measuring input suited to the current transformer secondary value, the auxiliary supply voltage, the tripping characteristic and the output contacts according to your protection coordination calculation.

Where can I find technical details for Overcurrent Secondary Protection Relays products?

A secondary relay does not interrupt the fault current itself; it passes the trip command to the circuit breaker's shunt trip coil, so it does not replace the circuit breaker.

Overcurrent Secondary Protection Relays Selection Guide: Technical Criteria & Application Standards