System integrity protection (SIPS) IEDs are designed to react on abnormal electric power system conditions and faults with the aim of electric power system recovery to normal operating mode. Two main tasks stipulate presence of system integrity protection IEDs:

  • Protection of the equipment against failures
  • Increasing of power transmission capacity

There may be defined two levels of SIPS: local and centralized. IEDs of these two levels differ by the data volumes processed and by the set of implemented functions. Local SIPS IEDs process data belonging to one or two bays; centralized SIPS IEDs collect and process data belonging to a subset of bays related to the specific area, including both generating facilities and substations.

As a rule, centralized SIPS IEDs operate under control of the specific system – centralized integrity protection scheme control and processing complex – which is controlled by System Operator. Local integrity protection IEDs usually operate according to the algorithms which were introduced at commissioning stage.

For implementation of local SIPS functions Prosoft-Systems offers TPA-01 IEDs. Centralized SIPS are implemented using UPAE IED. The list of protection schemes, which can be implemented using Prosoft-Systems products, is presented in Table 1.

Table 1.
Types of SIPS actions.



Out-of-step protection  Automatic power system stability
Overvoltage protection Automatic load shedding of power node
Equipment overload protection Intelligent load shedding
Overfrequency protection Automatic load shedding by one or two line tripping
Undervoltage protection Special load shedding automatics
Underfrequency protection Automatic load shedding of power plant
Automatic load shedding by close short circuits Automatic load of power plant
Automatic load shedding by power overload  
Automatic reactor control  
Pre-fault mode supervision  
Secondary voltage monitoring  
Line tripping identification  
Transformer tripping identification  
Generator block tripping identification  
Bus tripping identification  
Power drop identification  
Fault severity identification