standards / manuals / guidelines for small hydro development - AHEC

S.No.Item to beinspectedInspection ProcedureAction required ifunsatisfactory conditionindicatedApplicable fortransformersApplicableUATS, SSTS anddistributiontransformerswhen ticked √1 2 3 4 5switch and atmaximum,minimum andnormal taps fortransformers withOLTCii) Magnetising currentat 415 volts.iii) IR values afterisolating thetransformer.iv) Turn ratio.17. Oil coolers Clean oil coolers.Check for leaky tubes.H. 5 yearly forUATS andSSTS andDistributionTransformers& 7-10 yearlyfor otherTransformer/Shunt Reactors1. Transformercore andwindingsi) Wash by hosingdown with cleandry oil.- Flush cooler tubesRepair leaky tubes. Ifmore than 10% tubesleaking, replace the totaltube nest.-- See following paras a &b.I 20 Yearly1. Life assessmenttestsNote:DP and Furan contentmeasurementSee following para c.(a)As there is continuous deterioration of oil and insulation in a transformer, it is preferable thatthe core and windings and the inside surfaces of tank be thoroughly cleaned for any depositsetc. at regular intervals. This can be done while the transformer is in position. Close all valvesconnecting the cooler circuit/ radiators to the tank. Drain oil from the tank while letting thedry air to go inside. Clean core and winding by hosing down clean dry oil through theinspection cover. Remove dirty oil from the tank and wipe off this oil from the tank bottom.Let there be a continuous entry of dry air into the tank while the cleaning activity is on so thatAHEC/MNRE/SHP Standards/ E&M Works – Guidelines for Operation and Maintenance of Small Hydropower Station 50