BANGLADESH POWER DEVELOPMENT BOARD TENDER ... - BPDB

6.4 INSULATORS AND WIRING MATERIALS6.4.1 INSULATORS(1) Type and requirementsa. The insulator assembles shall consist of suspension insulator discs,hardware, strain or suspension clamps as required.b. The suspension insulators shall he of ball and socket type and shallconform to the requirement of IEC 120.c. The insulator unit shall be standard 254 mm porcelain disc type or fogtype 254 mm porcelain disc type, and have a spacing of 146 mm between discs.d. Total creepage distance of the insulator assemblies shall not be less than3300 mm.e. The insulators shall be wet-process porcelain of the highest glade, denseand homogeneous. The glaze shall be smooth, hard, dense and uniform and shallnot be effected by weather or sudden change in temperature, salty atmosphereand lighting during certain periods of the year. Colour of porcelain surface shall bebrown. All ferrous metals shall be galvanised except for female thread andstainless steel. Each insulator shall bear symbols identifying the manufacturer andindicating the year of manufacturer and tension proof test load.(2) Characteristics of Suspension Insulatorsa. Porcelain disc diameter : 254 mmb. Unit spacing : 146 mmc. Minimum electromechanical failing load : 21000 Kgd. Dimension of ball socket and pin : Conform to IEC(3) Characteristic of Insulator Assembliesa. Nominal system voltage : 230kVb. Highest system voltage : 275 kVc. Creepage distance not less than : 3300 mmd. Breaking strength of complete set : 1200kge. System insulation level- Basic impulse insulation level(1.2120 micro sec.) : 1050 kV peak- Power frequency withstands voltage(For 1 mm.): (As per relevant IEC) kV6.4.2 FITTINGThe suspension and tension clamps for bus works and outgoing feeders, tensionclamps for overhead grounding wires, U-bolts, ball eyes, anchor shackles, etc. forwiring of switchyard shall be furnished by the contractor. Unless otherwisespecified, all hardwire fittings shall be made by malleable iron or forged steel hotdip galvanised or aluminium alloy.Ghorasal 200 MW to 300 MW Gas Turbine Peaking Power Plant Project (Vol-2 of 3)68