scope:

PURPOSE AND SCOPE

This specification forms part of a suite of documents which define National Grid's functional and performance requirements for new plant and equipment associated with electricity transmission.

The Specification defines characteristics and performance requirements for all round and trapezoidal wire concentric lay ACSR, ACAR, AAAC, ACC (See Note 1), AACSR and for Gap-type GZTACSR overhead line conductors, including their lubrication, procured for and use on overhead lines owned by or directly connected to the National Grid transmission system operating at 132kV, 275kV & 400kV.

This specification defines the technical and general requirements applicable for designing a Conductor, Conductor and/or Earthwire System suitable for operational use on National Grid overhead lines operating at 132kV, 275kV and 400kV. In the case of earthwire conductors this specification details the requirements for standard earthwire & optical ground wire (OPGW). OPGW conductors are intended as a direct replacement for conventional earthwires on National Grid overhead lines where optical communications are required.

Earthwires shall normally be Keziah or Keziah Equivalent OPGW; if tower strength determines that a smaller earthwire be used then this shall be a Horse or Horse equivalent OPGW.

The following abbreviations and conductor designations according to BS EN 50182 and National Grid are used throughout this specification; in the case of composite core conductors for the purposes of clarification abbreviations as used by manufacturers have been adopted:

ACSR - Aluminium Conductor Steel Reinforced AL1/ST1A

ACAR - Aluminium Conductor Alloy Reinforced AL1/AL3

AAAC - All Aluminium Alloy Conductor AL5 (See Note 2)

AACSR - Aluminium Alloy Conductor Steel Reinforced AL5/ST1A (See Note 2)

AACSR - Aluminium Alloy Conductor Steel Reinforced (OPGW) A20SA/AL3

GZTACSR - "Gap" type ZT Aluminium Conductor Steel Reinforced (See Note 3)

ACC - Aluminium and Composite Conductor (See Note 1 & 3)

Note 1:- Conductors that incorporate composite sub components are for the purpose of this specification referred to as Aluminium & Composite Conductor (ACC).

Note 2:- The mean resistivity of AL5 is 31.2 n/m. However, National Grid specify a lower resistivity alloy for phase conductors, see 1.2.2 below, for which an equivalent type is not specified in BS EN 50182.

Note 3:- The material requirements for GZTACSR & ACC conductors are not currently defined in accordance with the nomenclature used for other conductor designs, for further information on these conductors refer to clause 1.2.2 of this specification.

This specification does not include detailed requirements for conductor fittings and sub components; the requirements for these are detailed in TS 3.4.35.