Some basic information on Protection Relay RET615. 

  RET615 is a dedicated transformer protection and control IED (intelligent electronic device) for power transformers, unit and step-up transformers including power generator, transformer blocks in utility and industry power distribution systems. RET615 provides main protection for two winding power transformers and power,generator-transformer blocks.The IED offerscontrol of one circuit breaker,(by default HV side circuit breaker) with
dedicated push-buttons for opening and closing.
The IED continuously measures the high, voltage (HV) side and the low-voltage (LV)
side phase currents and the neutral current of the protected transformer. The condition monitoring functions of the , IED constantly monitors the performance and
the condition of the circuit breaker. The , monitoring comprises the spring charging
time, SF6 gas pressure, the travel-time and , the inactivity time of the circuit breaker.A