standards / manuals / guidelines for small hydro development - AHEC

Annexure-3.1Ambient temperature & temperature rise for Mukerian Stage II Generatortransformer 11/66 kV class rated 10/12.5 MVA and 6.6/33 kVclass transformer for Sikasar Project Generator Transformer3.3/33 kV class rated 2 x 3.5 MWA. Reference Ambient TemperaturesThe reference ambient temperatures for which the transformers are to be designed are asunder:-i) Maximum ambient temperature 50 degree Cii) Maximum daily average ambient temp : 40 degree Ciii) Maximum yearly weighted average ambient temp : 40 degree Civ) Minimum ambient air temperature : ;(Cooling Minus 5 degreemedium shall be Air)CB. CLIMATIC CONDITIONS :i) Maximum relative humidity 100%ii) Yearly average number of thunder storms _______varies from 30 to 50 .iii) Average no. of rainy days per annum 60 daysiv) Fog : The atmosphere is subject to fog for two monthin winter.v) Number of months during which tropical monsoon 3 monthsconditions prevailvi) Dust storms occur at frequent intervalsvii) Average annual rainfall 60 cmsviii) Maximum wind pressure150 kg/sq.m.B. ALTITUDEAltitude above M.S. level not exceeding 1000 mtrs.C. TEMPERATURE RISE , OVER LOAD CAPACITY & CONTINUOUS RATINGa) With the above service conditions, given in clause-6.4 each transformer shall be capableof operating continuously on any tap at normal rating without exceeding followingtemperature rises, over maximum ambient temperature of 50 deg. C.i) 30 deg. C in oil by thermometerii) 45 deg. C in winding by resistanceiii) The temp. of hot spot in the winding not to exceed 90 deg. C when calculatedover max. annual weighted average temp. of 40 deg. C & 105 deg. C at worstambient of 50 deg. C.3-15