NG TGN(E) 187
Technical Guidance Notes - Guidance for Conductor Jointing in Substations
|Publication Date:||1 June 2004|
PURPOSE AND SCOPE
Within a substation there are many electrical connections ranging from high current busbar and earthing joints down to small assemblies on electronic circuit boards. This appendix deals with the former i.e. connections required to carry either primary load current or fault current or both. The associated maximum permitted temperatures under these conditions in accordance with NGTS 3.1.2 are 90C and 405C (325C for aluminium). This appendix does not cover equipment contacts, contractors, and sliding/moving contacts for which specific and detailed installation and maintenance instructions exist.
The integrity of busbar and earthing connections is essential for the security and safety of the high voltage substation. They are heavily loaded and temperatures at the connection interface are high such that degradation of poorly made and maintained joints is likely. Outdoor connections that operate under all weather conditions require protection to avoid corrosion induced long-term degradation.
The aim of this document is to provide guidance on good practice for conductor jointing in substations and it is Informative rather than Normative in nature. It aims to promote a good understanding of how to achieve high quality electrical connection and details typical problems encountered within the jointing process. Particular emphasis is placed on bolted joints for two reasons. Firstly, they can be less secure than joints which rely on fusion of materials e.g. welding and secondly, many bolted joints are disconnected for maintenance or to provide electrical isolation and thereby are at risk of being incorrectly remade.