NR RT/E/WI/27099 ISSUE 1 PDF

Introduction

The following instructions apply only to the 25kV Hackney Downs No. 2 TSC. These instructions set out the procedure to be carried out in connection with the issue and cancellation of High Voltage Permits to Work or Sanctions for Test, to enable work/testing to be carried out on this equipment or the connections thereto.

This instruction shall be read in conjunction with the following documents:

a) Instructions for Making Out, Issuing and Cancelling Permits to Work, Sanctions for Test and Circuit State Certificates (BR 12011/1).

b) The Working Instructions for A.C. Electrified Lines (BR 29987).

c) Rules for Ensuring Safety with Electrical Apparatus (BR 11884).

The following abbreviations apply:

E.C.O. Electrical Control Operator

O.H.L. Overhead Line

C.B. Circuit Breaker

Before carrying out any isolation affecting normal feeding arrangements, the E.C.O. shall ensure that arrangements have been implemented for alternative feeding.

All circuit breakers and O.H.L. feeder switches shall be operated in conjunction with the E.C.O. Each step of preparatory switching shall be agreed between the E.C.O. and the Nominated Person in Charge of the isolation. Each step shall be confirmed as having taken place before the next step can be carried out. Details of Permits to Work/Sanctions for Test shall be exchanged between the Nominated Person and the E.C.O. before issue. Each party will record details onto their copy of the document.

Where the use of portable earths is specified in this document, a single portable earth is required at each point of application. The earthing requirements specified herein do not preclude the use of additional portable earths considered necessary by the Nominated Person.

External earth connections shall be connected to the external earthing bar provided. All portable earths and additional portable earths shall be applied by a BR Authorised Person.

All portable earths shall be of an approved type and applied only using an approved earthing device. When using portable earths the earth end clamp shall be connected first before use and removed last after use. All leads shall be clear of rail traffic.

After the equipment has been isolated and earthed in accordance with the following procedures and a Permit to Work has been issued, it will be necessary to apply one or more extra portable earths if the work requires the opening of a C.B. or disconnection of the busbars.

Where no separate earth electrode is installed the connection to "earth" shall be interpreted as connections to the return current busbar, station earth tape or external earth bar, which are common connected and in turn connected by two or more bonds to the adjacent traction return rail, which together with the foundations of the overhead line structures constitute an effective earth electrode.

The bus section C.B. can be isolated by means of the manual and bus section sequential isolators. All other circuit breakers are provided with external circuit isolators, in the form of overhead line feeder switches, and sequential motorised isolators.

Before access can be permitted to any 25 kV enclosure, the circuit breakers, busbars and connections within that enclosure shall be isolated from all sources of supply, and earthed externally.