SPECIFICATION ‘STANDARD SPECIFICATION No. ENGINEERS. FOR cea NO NUNED Reread! 6-51-0043 Rev. 5 GROUNDING RESISTOR ago 1 of7 =I User treet & feu fare SPECIFICATION FOR NEUTRAL GROUNDING RES REVISED AND ISSUED AS STANDARD ee ‘SPECIFICATION. REVISED AND ISSUED AS STANDARD cio eee ‘SPECIFICATION 3} onga06 REVISED AND ISSUED AS STANDARD ‘SPECIFICATION - 2 2801.90 _ISSUEDAS STANDARD SPECIFICATION KVS 86 ent - — ‘Standards Standards Rev Committee Bureau Prepared Checked Date Purpose _Gonvenor__ Chairman No. J td ‘Approved by Format No. &-00-0001-F1 Rev. 0 Copyright Ell — All rights reservedSPECIFICATION STANDARD SPECIFICATION No. SSRIS (SS) ENGINEERS, seaebis ONA UMITED Reiopal 6-51-0043 Rev. 5 GROUNDING RESISTOR, Page 20f7 Abbreviations: GL. Galvanised Iron Electrical Standards Committee Convenor: Mr. A Ananthanarayan Members: Mr. VP Sharma Mr. KV Subramanyam Mr. CR Mandal/Mr. Ashok Choudhury Mr. SK Kaul Mr. UA Patro Format No, 6:00-0007-F1 Rev. 0 Copyright BIL Al rights reserved‘SPECIFICATION [STANDARD SPECIFICATION No. 6-51-0043 Rev. 5 Page 3of7 eee: OMAR oh GROUNDING RESISTOR, CONTENTS, 1.0 SCOPE 2.0 STANDARDS 3.0 GENERAL REQUIREMENTS eee 50 TECHNICAL REQUIREMENTS 6.0 INSPECTION, TESTING AND ACCEPTANCE 7.0 PACKING AND DESPATCH Format No. €-00-0001-F1 Rev. 0 ‘Copyright EIL ~ Arights reserved5 SPECIFICATION STANDARD SPECIFICATION No. SSHSITET SS) ENGINEERS. " SNe FOR! seareiics ONO Me NEUTRAL 6-51-0043 Rev. 5 GROUNDING RESISTOR Page 4 of 7 1.0 SCOPE 1.1 The intent of this specification is to define the requirements for design, manufacture, testing, packing and transport of Neutral Grounding Resistor (NGR), 2.0 CODES AND STANDARDS 2.1 The equipment shall comply with the requirements of latest revision of the following standards issued by BIS (Bureau of Indian Standards) and other agencies, unless otherwise specified: IS:5 Colours for ready mixed paints and enamels IS: 2705 Current transformers. IS: 3043 Code of practice for earthing IS: 3427 A.C. metal enclosed switchgear and controlgear for rated voltages above IkV and up to and including 52kV. IS: 13947 _L.V. switchgear and controlgear. IEEE: 32 Neutral Grounding Devices- Standard requirements, terminology and test procedure. ASTM-A240 Specification for heat resisting Chromium and Chromium-Nickel stainless steel plate, sheet and strip for pressure vessels 2.2 Incase of imported equipment, standards of the country of origin shall be applicable if these standards are equivalent or more stringent than the applicable Indian standards. 2.3. The equipment shall also conform to the provisions of Indian Electricity Rules and statutory regulations currently in force in the country. 24 Incase Indian standards are not available for any equipment, standards issued by IEC/ BS! VDE/ IEEE/ NEMA or equivalent agency shall be applicable, 2.5 Incase of any contradiction between various referred standards/ specifications’ data sheet and statutory regulations, the following order of decreasing priority shall govern: - Statutory regulations - Data sheets - Job specification - This specification : Codes and standards. 3.0 GENERAL REQUIREMENTS 3.1 The offered equipment shall be brand new with state of art technology and proven field track record, No prototype equipment shall be offered. 3.2. Vendor shall ensure availability of spare parts and maintenance support services for the offered equipment at least for’IS years from the date of supply. 3.3 Vendor shall give a notice of at least one year to the end user of equipment and EIL before phasing out the product/spares to enable the end user for placement of order for spares and services, 4.0 SITE CONDITIONS, The Neutral Grounding Resistor shall be suitable for outdoor installation (without a shed) for satisfactory operation under conditions of restricted natural ventilation in a tropical humid and corrosive atmosphere as prevalent in refineries, petrochemical and fertilizer plants. The NGR shall be designed to operate under site conditions as specified in the data sheet. If not specifically mentioned therein, a design ambient temperature of 40° C and an altitude not exceeding 1000 m above mean sea level shall be considered, Format Ne. &00-0007-F1 Rev. 0 ‘Copyight EL — All ights reservedSPECIFICATION —_—_stavonnDspcrteano eit OQAiiw Woe 6-5-0043 Row 5 ‘GROUNDING RESISTOR Page 5 of 7 5.0 TECHNICAL REQUIREMENTS or Resistors SAL ‘The resistor elements shall be made of unbreakable, corrosion proof, joint-less stainless steel 313 521 5.2.5 5.2.6 grid conforming to ASTM standard A240-304. The grids shall be in punched form. The resistor shali be sized for carrying the rated current specified in the data sheet for 10 seconds with maximum temperature limited to 790° C for stainless steel resistor elements, while limiting the temperature of aluminium conductor / bus bar to 350° C. If specified in the data sheets, the resistor shall also be sized to carry 10% of the rated current continuously with the maximum operating temperature of resistor elements limited to 415° C. Further, the temperature rise of the resistor elements when they carry 10% of the rated current followed by the specified rated current for 10 seconds shall not exceed the temperature limits specified in clause 5.1.2 above. Under the steady-state conditions when the NGR carries 10% of the rated current, the surface temperature of the enclosure, excluding the roof but including the separate canopy, shall be limited to maximum 70° C. Grids shall be mounted on stee! rods insulated by special heat-resistant insulating materials, suitable for the above temperatures. Ceramic/ porcelain insulators shall be used to insulate the resistor elements from the enclosure, The insulators and terminal bushings shall have adequate minimum creepage values (total and protected) for the required voltage grade. Resistor banks shall be provided in series and parallel combinations to achieve the overall resistance value. Minimum two banks in parallel shall be provided in the system, unless specified otherwise. Enclosure ‘The resistor elements shall be housed in 2 naturally ventilated sheet steel enclosure with ‘minimum IP-31 degree of ingress protection and suitable for outdoor installation. ‘The enclosure thickness shall not be less than 3 mm. The NGR shall have a suitable arrangement for fixing it on concrete foundations/ grouting in floor. ‘The terminals for neutral and earthing connections shall be housed in a separate vermin- proof, weatherproof terminal box with minimum IP-55 degree of ingress protection. The terminal box shall be provided with a separate bolted removable undrilled gland plate of non-magnetic material. This shall be drilled at site to suit the cable entry ‘A separate canopy shall be provided above the enclosure roof with a suitable air gap between them, It shall also cover the terminal compartment. Suitable lifting arrangement shall be provided to lift the“eanopy. It shall be possible to periodically clean the resistor elements and enclosure after removing the bolted side covers. Facility shall be provided to earth the enclosure at two points. For this purpose, suitably sized studs shall be provided on the sides of the enclosure to accommodate the connection of GI strip. ‘The bottom of the enclosure shall be provided with a drain plug to remove water that may get collected in the enclosure. Format No, -00-0001-F1 Rev. 0 Copyright EL ~ Alvights reservedSRG IIE ft ENCINEERS SPECIFICATION ‘STANDARD SPECIFICATION No. sear ESA UMITED FOR So ett eens nce NEUTRAL 6-51-0043 Rev. 5 GROUNDING RESISTOR Page 6 of7 53 Terminals 5.3.1 The two ends of the resistor shall be brought out to suitable epoxy/ porcelain bushing type terminals of adequate rating for the neutral and earth connections. The terminals shall be suitable for terminating the specified size of cables/ earthing strip and shall be supplied complete with tinned-copper lugs. Bolted type link shall be provided for isolating the resistor at the neutral end, 5.3.2 Suitable washers shall be provided between the grid element ends and the terminals to ‘maintain good electrical contact. 5.3.3 The connection between the transformer neutral and the NGR shall be carried out by means of single core / multi core cable of size and type as specified in the data sheet. 5.3.4 The connection between the NGR and the earth pits shall be carried out using GI Earthing strip/ cable as specified in the data sheet. 54 Space Heater Suitable anti-condensation space heater shall be provided inside the NGR enclosure to prevent condensation of moisture. This shall be rated to operate from a 240 V, 50 Hz, single phase supply. The terminals of the space heater shall be brought out to a separate weatherproof terminal box. The terminal box/M.B shall have minimum IP-55 degree of ingress protection The space heater shall be controlled using a double pole MCB and thermostat provided in the terminal box. The MCB shall be operable from the front of enclosure without opening. the terminal box cover. 35 The current transformer, if specified, shall be of cast resin type suitable for the applicable voltage grade and temperature conditions. The secondary connections of the current transformer shall be brought out to suitable terminals in M.B and shall be provided with a shorting link 5.6 Cooling The Neutral Grounding Resistor shell be natural air cooled. Forced cooling shall not be used. If required, louvers can be provided in the enclosure provided they are completely guarded on the inside with a fine wire mesh, 5.7 Nameplate Marking The equipment shall be provided with a stainless steel nameplate located prominently indicating following minimum information a Make b. Tag No, c. Resistor nominal value in ohms a. Rated voltage ¢ € System voltage and frequency f Rated current a Time rating in seconds h ‘Temperature rise in centigrade i Enclosure protection class. 5.8 Painting ‘Afier manufacture, all surfaces to be painted shall be thoroughly cleaned, descaled, made free from rust and given one coat of primer and two coats of epoxy paint of shade 632 as per IS: 5 or as specified in the data sheet, Format No. 6:00-0001-F1 Rev. 0 Copyright BIL — Alvights reseedSPECIFICATION [STANDARD SPECIFICATION No. SOiifetazeT ay ENGINEERS, 2a ROR UMITED FOR 6-51-0043 Rev. 5 60 61 62 63 64 70 ao Ral table NEUTRAL GROUNDING RESISTOR Page 7 of7 INSPECTION, TESTING AND ACCEPTANCE The offered NGR shall have been suitably type tested and manufacturer shall furnish test certificates in this regard. During fabrication, the equipment shall be subjected to inspection by EIL/ Owner or by an agency authorised by the owner. Minimum four weeks advance notice shall be given to ‘owner for this purpose, Manufacturer shall furnish all necessary information concerning the supply to EIL/ Owner's inspector. Tests shall be carried out at manufacturer's works under his, care and expense. The following tests shall be conducted: a. Visual and dimension checking b. Measurement of resistance value at prevailing ambient temperature by Kelvin Double Bridge. ©. One minute power frequency high voltage withstand test d. Insulation resistance measurement, both before and after the power frequency high voltage test. e. Heat run test.(on one NGR of each rating) ‘The heat run test shall be conducted by passing the rated current for rated time on a limited resistor section in a proportionately sized test enclosure. The temperature rise shall be measured under simulated conditions ensuring that heat produced (Rt) in the test enclosure is more than or equal to the calculated value of energy dissipation required for the test enclosure in proportion to the complete Neutral Grounding Resistor enclosure as per the thermal model adopted, PACKING AND DESPATCH lll the equipment shall be divided into several sections for protection and ease of handling, uring transportation. The equipment shall be properly packed for the selected mode of transportation i.e. by ship/ rail or trailer and shall be wrapped in polythene sheets before being placed in crates/ cases to prevent damage to finish. The crates’ cases shall have skid bottom for handling. Special notations such as ‘Fragile’, “This side up’, “Center of gravity’, “Weight’,’ Owner's particulars’, "PO nos.’ etc., shall be clearly marked on the packages together with other details as per purchase order. ‘The equipment may be stored outdoors for long periods before installation. ‘The packing, shall be completely suitable for outdoor storage in areas with heavy rains/ high ambient temperature unless otherwise agreed, Format No, 6.00-0001-F1 Rev. 0 Copyright EI. ~ Al rights reserved