Public Works Department Tender

Action to be taken on Distribution transformer on quarterly basis. 1. The oil level in oil cap under silica gel breather quarterly y If it is found the transformer oil inside the cup comes below the specified level, oil to be top up as per specified level. 2. Breathing holes in silica gel breather should also be checked and properlycleaned if required, for proper breathing action. 3. If the transformer has oil filled bushing the oil level of transformer oil inside the bushing must be individually checked in the oil gage attached to those bushing. This action also to be done quarterly basis. If it is required, the oil to be filled in the bushing up to correct level. Oil filling to be done under shutdown condition. There are three main things which to be checked on a Distribution transformer on a daily basis: 1. Reading of MOG (Magnetic Oil Gauge) of main tank and conservator tank. 1. Color of silica gel in breather. 2. Leakage of oil from any point of a transformer. In case of unsatisfactory oil level in the MOG, oil to be filled in transformer and also the transformer tank to be checked for oil leakage. If oil leakage is found take required action to plug the leakage. If silica gel becomes pinkish, it should be replaced.

Yearly Basis Transformer Maintenance Schedule 1. The auto, remote, manual function of cooling system that means, oil pumps, air fans, and other items engaged in cooling system of transformer, along with their control circuit to be checked in the interval of one year. In the case of trouble, investigate control circuit and physical condition of pumps and fans. 2. All the bushings of the transformer to be cleaned by soft cotton cloths yearly. During cleaning the bushing should be checked for cracking. 3. Oil condition of OLTC to be examined in every year. For that, oil sample to be taken from drain valve of diverter tank, and this collected oil sample to be tested for dielectric strength (BDV) and moisture content (PPM). If BDV is low and PPM for moisture is found high compared to recommended values, the oil inside the OLTC to be replaced or filtered.(dehydration to be done depending on test resuls as BDV value ) 4. Mechanical inspection of Buchholz relays to be carried out on yearly basis. 5. All marshalling boxes to be cleaned from inside at least once in a year. All illumination, space heaters, to be checked whether they are functioning properly or not. If not, required maintenance action to be taken. All the terminal connections of control and relay wiring to be checked an tighten at least once in a year.

6. All the relays, alarms and control switches along with their circuit, in R&C panel (Relay and Control Panel) and RTCC (Remote Tap Changer Control Panel) to be cleaned by appropriate cleaning agent. 7. The pockets for OTI, WTI (Oil Temperature Indicator & Winding Temperature Indicator) on the transformer top cover to be checked and if required oil to be replenished. 8. The proper function of Pressure Release Device and Buchholz relay must be checked annually. For that, trip contacts and alarm contacts of the said devices are shorted by a small piece of wire, and observe whether the concerned relays in remote panel are properly working or not. 9. Insulation resistance and polarization index of transformer must be checked with battery operated megger of 5 KV range. 10. Resistive value of earth connections must be measured annually with clamp on earth resistance meter. 11.maintainace of PT,CT,CVT will be also under this scope of work. The Action to be taken once in 2 years: 1. The calibration of OTI and WTI must be carried once in two years.

panel should be maintained ensuring all its protective realys such as multifunctional relay ,earth fault relay,over current and over voltage relays along with all indicative elements ,maintainace of VCB's and its contactors

VCB breaker serving & testing  Cleaning of metal and non-metal parts  Lubrication  Visual inspection  Detection of leakage  Circuit Breaker C-O-CO Time Interval Testing  Insulation resistance Test  Contact Resistance Test  Continuity Test  Coil Resistance Test  Motor Operation Test  Operation Test (Local or Remote Mode)  Interlocking Test

complete job 1 and 2 including all auxillary items and items which are not mentioned in order for proper functioning of transformer Breakdown period of transforemer of panel shall not exceed more than 24 hours and after that penalty shall be levied 2 % per day of the total amount Emergency Visit for trouble shooting and reapiring within 6-7 hours (4 nos inclusive )