If in between FES (Fast acting Earthing Switch) and maintenance earth switch there is no other equipment, then what is the purpose of the FES in this application?
Is the PASS M0 SBB (single busbar) with Disconnecting Earthing Switch and FES and current transformers on both sides such a configuration?
The purpose of Fast Earthing Switch (FES) is, usually, to earth transmission lines where currents may circulate as a result of capacitive and inductive coupling with adjacent energized lines. In these cases, an ordinary maintenance earthing switch (ES) will not be enough to make and break capacitive and inductive currents. From a theoretical point of view, maintenance earthing switch could be avoided if there is FES beside it, with no other equipment in between.
In the case of PASS, the key-point to consider is that disconnector (DS) and ES are a single combined unit.
Let’s consider the configuration indicated: M0 SBB with DS\ES + FES + CT on both sides.
In this case the maintenance ES is normally placed on the breaker side, then there is the disconnector, and then the FES on the other side which is most of the time line side. Hence you have an equipment in between maintenance ES and FES, the DS.
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