Introduction

It is not generally know by most users of electricity to what extent power system automation is being used - that is until there is a blackout.

Overcurrent protection

All lines and all electrical equipment must be protected against prolonged overcurrent. If the cause of the overcurrent is nearby then automatically that current is interrupted immediately. But if the cause of the overcurrent is outside the local area then a backup provision automatically disconnects all affected circuits after a suitable time delay.

Note that disconnecion can, unfortunately, have a cascade effect, leading to overcurrent in other circuits that then also must therefore disconnect automatically.

Also note that generators that suddenly have lost their load because of such a protection operation will have to shut down automatically immediately, and it may take many hours to restore a proper balance between demand and supply in the system, partly because there must be proper synchronization before any two parts of the system can be reconnected. By the way, because frequency may no longer be normal, electric clocks may no longer be showing the correct time.

Reclosing operations (only once) of circuit breakers usually are attempted automatically, and often are successful during thunderstorms, for example.

Supervisory Control

Some power stations can control other stations via communication links over long distances. Remote switching, telemetering (showing voltage, current, power, direction etc.), even automatic synchronization is used in some power systems.