Power Engineering Consultants plc

Use of armoured single core cables in HV installations may be the designer's choice; easy to install and terminate and they contribute to good earthing, but there can be serious consequences if the flow of armour current is neglected.

When cable armour is insufficient to carry expected earth fault current for the necessary period of time, a supplementary earth cable can be provided.

Although it is generally the practice to provide an earth path in HV systems, there are examples where this is not the case and the HV power system operates in isolation from earth.  We call these unearthed systems.  The term ungrounded is also used.

The excitation of a synchronous generator is usually done by an AVR (Automatic Voltage Regulator) that uses generator voltage and/or current as inputs in order to control its output to a pre-set value.

The differential protection function of a generator relay uses the difference between current into and out of the generator in order to detect internal faults in the generator winding.