PURPOSE AND SCOPE

The purpose of this document is to give guidance to National Grid and its Contractors on the sources of Impressed Voltage, giving guidance on the means by which the hazards emanating from impressed voltage can be controlled.

The tables located in sections 1, 2, & 3 in the main body of the document identify the areas where Impressed Voltages are likely to occur, what the source of the Impressed Voltage is likely to be, the area of concern, proposed method of control and the associated reference documents. It is not by any means a full and exhaustive list and should be considered as instructive advice when considering carrying out work on HV equipment.

The procedure shall apply to all Electricity Transmission works / projects that comprise both the capital plan and maintenance programmes and sets out what needs to be considered throughout both the scheme development process through TP 500 for Capital Projects and for National Grid Maintenance under PS (T) EPS 11.0, Maintenance Policy to help develop and maintain a safe system of work.

The document itself does not constitute a safe system of work but does give guidance on known situations of where Impressed Voltages can occur and actions to be applied for their control