This document details mandatory prescriptive and functional requirements relating to the construction of new and, where suitable, modifications to existing buildings and associated infrastructure on 400kV and 275kV Gas Insulated Switchgear (GIS) substation sites and where, appropriate Air Insulated Switchgear (AIS) substations. It is a development of, and shall be read in conjunction with, all relevant National Grid standards as appropriate.

For the purposes of this document it is assumed that a GIS substation shall comprises up to three distinct groups of buildings described below. These building units shall be used individually or in combination as necessary to achieve the project objectives. Design and configuration shall be as economic as possible whilst achieving the required levels of functionality. On new build projects all building groups may be utilised whilst at existing sites only certain elements may be required to supplement existing facilities.

Barring the exceptions in 1.1.4 the requirements contained herein shall constitute the design standards for all GIS substation buildings and, where appropriate, the equivalent buildings on AIS substations. Only where it is proven that there is a more technically proficient and/or cost effective solution shall alternative arrangements be permitted.

These requirements shall not apply to 132kV GIS Substation Buildings (which are generally elevated to facilitate cable entry) or multi-storey 400kV and 275kV GIS Substation buildings. This document shall be supplemented with additional specifications for such installations. Design work shall comply with all appropriate National Grid Technical Specifications (NGTS’s and TS’s),

Design Handbooks, British Standards, European Standards and Codes of Practice as appropriate and be in accordance with recognised analytical methods. Where the requirements of this document or any other relevant project specifications are in conflict those specifically detailed within this document shall take precedence.

The building groups shall be as follows;

a) SWITCH HALL The primary function of the switch hall building shall be to act as a ‘weather shield’ for the Gas Insulated Switchgear contained therein. b) ANCILLARY PLANT ROOM BUILDINGS Comprising individual prefabricated modular buildings housing one or more of each of the following facilities; 􀂃 LVAC Supplies/Distribution Room 

Protection Room 

Battery Room 

Telecoms Room 

Substation Control System/Permit Room

c) AMENTIES BLOCK Comprising a single prefabricated modular building containing one or more of the following as necessary; 

• Kitchen/Mess facilities 

• Toilet 

•  Office 

The building groups shall be as follows;0

a) SWITCH HALL The primary function of the switch hall building shall be to act as a ‘weather shield’ for the Gas Insulated Switchgear contained therein.

b) ANCILLARY PLANT ROOM BUILDINGS Comprising individual prefabricated modular buildings housing one or more of each of the following facilities;

• LVAC Supplies/Distribution Room

• Protection Room 

• Battery Room 

• Telecoms Room 

• Substation Control System/Permit Room

c) AMENTIES BLOCK Comprising a single prefabricated modular building containing one or more of the following as necessary; 

• Kitchen/Mess facilities 

• Toilet 

• Office