The Impact of Topology awareness

It leads also to the increasing dependence of a function in one  IED from the data provided by other IEDs, thus introducing some new issues in system maintainability and reliability. Some of these issues can be overcome by a systematically used approach of topology aware functions. This is illustrated by means of some protection related system functions like breaker failure protection, reverse blocking and the lockout function.

Topology aware functions

In the context of this article we call a function ‘topology aware' if it either can analyze switch yard related topology properties or use these properties for its application purpose. An example is the breaker failure protection. In case that the operation to trip a breaker has finally failed, it has to trip all breakers in the adjacent protection zones. Thus it must ‘know’ at least the adjacent protection zones, possibly also the contained breakers – this depends on the details of the function implementation. The distributed functional elements of the breaker failure function, in IEC 61850 terms the logical nodes forming the function, are called ‘topology aware’, if they ‘know’ to which protection zone they belong, thus directly understanding what a ‘tripping of the zone’ means.  To get this knowledge, additionally to the wanted function itself a topology analysis function is needed, which tells the application logical nodes to which zone they currently belong. For breaker failure detection the breakers learn to which protection zone they belong. Just sending a trip for an identified zone is then sufficient to trip all breakers contained in that zone. The result of the zone analysis can be shared between different functions relying on the zone concept.

Protection zones are one possible topology part which is useful to identify, especially in the context of protection functions. Other meaningful topology parts might be electrically connected parts with their properties like electrical potential, used for interlocking functions, or defining which healthy VT measures the voltage within a connected part for a bus bar image function.

The following example illustrates the underlying concepts by means of protection zones.