CA NO CWE/PM/N-25/2020-21 PROVISION OF EARTHING PITS FOR CRITICAL EQUIPMENT AT AF STATION PALAM UNDER GE (AF) PALAM DELHI CANTT-10

Amount

Supply, installation, testing and commissioning of maintenance free earth (grounding) electrode of size 100 mm Dia x 30.5 Mtr long with 17.2 mm Cu bonded MS conductor pre cast or in-situ cast in high purity electrically conductive granular material having ultra low resistive value of 0.001 Ohm-m. Electrode made of conductive earth enhancing material mixed with cement in the ratio 3:1 to achieve result of earth resistance less than 1 Ohms encase or backfill the voids surrounding the 17.2 mm Cu Bonded MS conductor or other metal components placed in augured bore hole of 100mm dia x 30.5 Mtr depth, resulting to increase in the effective surface area of the earth electrode or grids to lower the resistance. Earth enhancing matetial should not leach chemicals into the adjacent soil or underground water channels and should be in pH neutral range. Earth enhancing material should permanently protect the encased metal components of the earthing system, copper bonding on MS rod should be minimum 250 microns. All hardware like nuts, bolts and washers should be of stainless steel. Electrode should withstand fault current upto 35 KA for 1 second. Electrode's top terminal be sealed permanently packed with conductive concrete and Cu bonded MS/ copper strip taken out be terminated on to earth test point and equipment terminal. Test certificate of NABAL laboratory shall be submitted by the contractor, test link of size 50 mmX6mm X200mm, RCC pit cover including brazing of all the joints upto test point complete, all as specified and directed by Engineer-in-Charge. Make: Elancrete/Macronite. Note :- (i) Test certificate of earthing material from certified NABL laboratory shall be submitted & verified by GE. Test certificates shall be kept in record by GE. (ii) Payment of Earthing shall be allowed only if result of earth resistance is achieved below 01 (One) Ohm. (iii) Manufactures warranty for performance of resistance value less than 01 Ohm for period of min 25 years after commissioning shall be provided by contractor.

M&L for earth continuity conductor or main earthing lead fixed to wall or recess or buried in ground or drawn in conduit/pipe or fixed to poles or any other indicated situation for loop earthing etc as required with 20 mm x 3 mm copper strip including fixing on porcelain holder insulator for support on wall/roof etc with suitable size of screws, nuts and bolts etc. complete, all as specified and directed by Engineer-in-Charge.

G M CONSTRUCTION COMPANY

BRIJ MOHAN LAL AND CO.

Ridhi engineers and builders

Shiv Shankar Nirman Co.