SPECIAL REPAIR TO EARTHING PITS AT AF STN DARBHANGA UNDER GE AF BIHTA

Copper strip of size 20mm x3mm

Aluminium strip of size 25mm x3.15mm with saddle.

Test point terminal block made of gun metal or phosphorus bronze size 75x75x25mm drilled and screwed including 3 nos. 8mm dia 25mm long hex, head screw complete all as specified.

Air terminations single pointed aluminium rod 12mm dia and 300mm long including mounting arrangement complete all as specified.

GI Pipe light grade of 40mm with necessary GI fittings laid in floors / wall & cover complete all as specified

Rigid non-metallic PVC conduit 32mm, ISI marked, exclusive of boxes (junction/terminal) but inclusive of all tees, bends elbows, reducers, bell mouth tube ends and fixing accessories such as couples, lock nuts, saddles, pipe hooks etc. complete all as specified.

Advance Chemical Sealed Electrode Box type light weight GI horizontal electrode of 4 sets designed for use in any type of soil condition. Each electrode is to be designed in box shape using 2mm thick GI plates of 600x450mm x100mm as outers of the box with 1.5mm thick pure Cu plate of dimension 450mm x 450mm, two 50mm sockets are to be placed on top with removable caps and two handles to facilitate handling. The inner space between plates is to be fillled with about 28 Kg of specilized ASEM-GB (Advance Soil Enhancement material- Graphite based), an extremely low resistivity (0.05 ohm/m & below) (High conductivity) hygroscopic, non-soluble stable material. The material is filled in the electrode in very thick slurry form made with water to withstand -30 degree to +70 degree. After filling the high conductive salt in the box both the sockets are crapped and closed. A Cu terminal 200x40x6mm is to be fixed along the centre protruding on the socket centre for necessary connection/bonding. A 1.5 mtr length of PVC insulated 50 sq mm copper flexible cable is to be provided with each electrode for necessary connection to distribution box or bonding between two electrodes. One galvanized iron sheet junction/Distribution box is to be provided with every two electrodes. The electrode should not weight more than 45 Kgs. (ii) A pit of 650x500mmx150mm with depth of 2.0-3.0 feet is required to be dug out. The pit is filled with water and left till the water is absorbed. Electrode is now placed centrally in the pit in the desired format. The pit is filled with dug out soil duly filtered from gravel; water source should be active when soil is being filled. Adequate amount of water is poured in the trenches, and then the soil is compacted and left to settle for some time before any measurements are done. after removing the electrode, clean it wash it any dry it before storing. Note- (i) Earth resistance should be less than one Ohm. In case the test results are not found below one Ohm, complete earthing shall be redone by contractor without any extra cost to Govt . (ii) Grid 4 Electrodes shall be included in the quoted rate. (iii) Contrctor submiit all test certificates as NABL accredited laboratory. (iv) "Performance Guarantee" as mentioned in PS clause 19.1.5.

Earthing complete with copper plate 60x60x3.15mm thick electrode buried directly in round (earth pit not less than 2.25 metres deep below ground level) with top edge of the plate not less than 1.5 metres below normal ground level. Connected to 20x3mm copper strip as earthing lead by means of bolts, nuts, check nuts and washers of galvanised iron or steel all as shown in electrical plate No. 5 connected to earthing test point all as specified or indicated including testing on completion. The earthing conductor up to length of 7.5mtr up to test point from copper rod is also included. The scope include PCC 1:3:6 size C-1 (using 20mm grade store aggregate) with pit cover or the pit cover as per company standard shall be as recommended by manufacturer complete all as specified and directed by Engr-in-charge. NOTE: - (a) The unit rate includes earthing lead and protection pipe upto 7.5 metre from top of earth plate. (b) PCC pit with cover shall be fixed at least 500 mm away from earth pit. (c) Earth resstance shall be less than 2 ohm. In case the test results are not found less than 3 ohm, complete earthing shall be redone by the contractor without any extra cost to Govt.

Disconnecting and taking out old earthing for site clearance all as specified and directed.