IEC 60255-151:2009

FOREWORD
1 Scope and object
2 Normative references
3 Terms and definitions
4 Specification of the function
  4.1 General
  4.2 Input Energizing quantities/energizing quantities
  4.3 Binary input signals
  4.4 Functional logic
      4.4.1 Operating characteristics
      4.4.2 Reset characteristics
  4.5 Binary output signals
      4.5.1 Start (pick-up) signal
      4.5.2 Operate (trip) signal
      4.5.3 Other binary output signals
  4.6 Additional influencing functions/conditions
  4.7 Specific characteristics
5 Performance specification
  5.1 Accuracy related to the characteristic quantity
  5.2 Accuracy related to the operate time
  5.3 Accuracy related to the reset time
  5.4 Transient performance
      5.4.1 Transient overreach
      5.4.2 Overshoot time
      5.4.3 Response to time varying value of the characteristic
            quantity
  5.5 Current transformer requirements
6 Functional test methodology
  6.1 General
  6.2 Determination of steady state errors related to the
      characteristic quantity
      6.2.1 Accuracy of setting (start) value
      6.2.2 Reset ratio determination
  6.3 Determination of steady state errors related to the
      start and operate time
  6.4 Determination of steady state errors related to the
      reset time
  6.5 Determination of transient performance
      6.5.1 General
      6.5.2 Transient overreach
      6.5.3 Overshoot time
      6.5.4 Response to time varying value of the characteristic
            quantity for dependent time relays
7 Documentation requirements
  7.1 Type test report
  7.2 Other user documentation
Annex A (normative) Constants for dependent time
        operating and reset characteristics
Annex B (informative) Reset time determination for relays
        with trip output only
Bibliography

IEC 60255-151:2009 specifies minimum requirements for over/under current relays. It includes a specification of the protection function, measurement characteristics and time delay characteristics. Defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions.