Ambient temperature will be as under

Maximum

50°C

Maximum mean over 24 hours

45°C

Mean in any year

30°C

Relative humidity may range to 100% The equipment shall be suitable for installation and operation at an altitude up to 1000 meters above sea level.

BUS BARS

The bus-bars shall be of aluminum of 99.5% purity having 61% IACS conductivity and minimum tensile strength of 8.4 kg/mm2. The bus bars shall be extruded or hard drawn. The size of busbars shall be 40 x 10 mm. These shall have a smooth finish, free from sharp edges, holes and cavities etc.

LUGS

The terminal lugs both for single and three phase box shall be of dimensions as given in WAPDA specification and shall meet the requirements.

EARTHING

A galvanized steel connector of size shall be provided outside the enclosure. All metal parts of the installation shall be bonded so as to be effectively earthed. Door shall be connected to the body of the enclosure by means of flexible strap and the hinges shall not be relied upon for earthing.

NUTS AND BOLTS

All nuts, bolts and washers used for fixing termination lugs and busbars shall be of mild steel and shall be hot dip galvanized. The weight of zinc coating shall be as per WAPDA specification. Two plain and one spring washer shall be provided with each bolt. Nuts, bolts, washers and earthing connector shall be galvanized and tested in accordance with WAPDA specification.

BACKELITE INSULATORS

The Backelite insulators for supporting the bus bar shall be of dimensions and shall be of good commercial grade and insert brass nut of size M-10. The minimum leakage distance shall be 40 mm. Backlite insulator should withstand at least 8 KV for one minute.