Ipsa 2 Overcurrent Protection Grading


  • Modelling of protection devices
  • Changeable protection device parameters
  • Protective Device Modeller (PDM) database


  • Each device can have any number of curves of different types
  • Protection Groups contain the CTs, fuses, relays etc for each component
  • The device parameters can be varied

The protection and co-ordination module models the operation of protection relays and circuit breakers under steady state, fault and transient conditions. Ipsa comes with an extensive library of protection relays which can be quickly added to the network. Time - current coordination graphs can be plotted to determine the grading margins between protection relays, fuses and other characteristics such as motor start curves and cable or transformer damage curves.

Users are able to add new protection devices or modify existing models using the Protection Device Modeller (PDM) application which is supplied free with all copies of Ipsa.

Key Features

  • Extensive database of relays and characterisitics:
    • Fuses
    • Overcurrent relays
    • Motor starting curves
    • Damage curves
    • Circuit breakers
  • Protection co-ordination in fault level
    • Time - current curves and operating times are calculated for user defined fault currents
    • Actual fault flow currents calculated by Ipsa can also be used to determine operating times
    • Results presented on graphs and in coordination tables
    • Operating time and time between adjacent devices is calculated
  • Optional relay operation in load flow (overloads)
    • Protection devices which may operate in load flow due to overloads or incorrect settings are identified
  • Intertripping of circuit breakers
    • Circuit breakers can be linked to protection devices
    • Operation of the protection relays then causes linked circuit breakers to operate
    • Intertrip logic schemes can be configured to model auto-close bus section schemes and similar
  • Relay operation in transient stability
    • Relay operation can be modelled during transient stability studies
    • Circuit breaker intertrip schemes operate in response to protection relays
    • Cascade tripping of protection devices can be analysed