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Electrical Engineering Academy

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Transformer Accessories.

TRANSFORMER

STANDARD TRANSFORMER ACCESSORIES & FITTINGS:

STANDARD TRANSFORMER FITTINGS:

  1. STANDARD FITTINGS
  • Rating and terminal marking plate. * Tap Changing arrangement * Off – circuit tap changing switch * Off – circuit tap changing link * On Load tap changer * Two earthing terminals * Lifting Lugs * Drain – cum filter valve * Pressure Relief Device * Silica gel dehydrating breather. * Oil Level Indicator. * Thermometer Pocket. * Conservator with drain plug and filling hole. * Air Release plug. * Jacking lugs (above 1600 KVA) * Filter valve (top tank) * Under base unidirectional flat rollers.
  1. TERMINAL ARRANGEMENT:
  • Bare Bushings or Cable box. * Compound filled for PVC cables (up to 33000 Volts) or Air filled for PVC cable s (Up to 11000 Volts) or * Bus Duct (Bare bushing enclosed in housing up to 600 Volts) * Disconnection chamber between cable box and transformer tank. * Additional bare neutral terminal.
  1. OPTIONAL FITTINGS:
  • These are optional fittings provided at an extra cost, if customer specifically orders them. * Winding temperature indicator * Oil temperature indicator * Gas and oil actuated (Buchholz) relay * Conservator drain valve * Shut off valve between conservator and tank. * Magnetic oil level gauge * Explosion vent * Filter valve (Bottom of tank) * Skid under base with haulage holes * Junction box.

STANDARD TRANSFORMER ACCESSORIES:

  1. THERMOMETER POCKETS:
  • This pocket is provided to measure temperature of the top oil in tank with a mercury in glass type thermometer. It is essential to fill the pocket with transformer oil before inserting the thermometer, to have uniform and correct reading. One additional pocket is provided for dial type thermometer (OTI) with contacts 
  1. AIR RELEASE PLUG:
  • Air release plug is normally provided on the tank cover for transformer with conservator. Space is provided in the plug which allows air to be escaped without removing the plug fully from the seat. Plug should be unscrewed till air comes out from cross hole and as soon as oil flows out it should be closed. Air release plugs are also provided on radiator headers and outdoor bushings.
  1. WINDING TEMPERATURE INDICATOR
  • The windings temperature indicator indicates ‘’ Hot spot’’ temperature of the winding. This is a ‘’Thermal Image type’’ indicator. This is basically an oil temperature indicator with a heater responsible to raise the temperature equal to the ‘’Hot spot’’ gradient between winding and oil over the oil temperature. Thus, this instrument indicates the ‘’Hot Spot’’ temperature of the windings. Heater coil is fed with a current proportional to the windings current through a current transformer mounted on the winding under measurement. Heater coil is either placed on the heater bulb enveloping the sensing element of the winding temperature indicator immersed in oil or in the instrument. The value of the current fed to the heater is such that it raises the temperature by an amount equal to the hot spot gradient of the winding, as described above. Thus temperature of winding is simulated on the dial of the instrument. Pointer is connected thought a mechanism to indicate the hot spot temperature on dial. WTI is provided with a temperature recording dial main pointer. Maximum pointer and re setting device and two sets of contacts for alarm and trip.
  1. OIL TEMPERATURE INDICATOR
  • Oil temperature indicator provides local temperature of top oil. Instruments are provided with temperature sensing bulb, temperature recording dial with the pointer and maximum reading pointer and resetting device. Electrical contacts are provided to give alarm or trip at a required setting (on capillary tube type thermometer).
  1. CONSERVATOR TANK:
  • It is an Expansion Vessel * It maintains oil in the Transformer above a Minimum Level * It has a Magnetic Oil Level Gage. * It can give an alarm if the oil level falls below the limit * A portion of the Tank is separated for use with OLTC. * This usually has oil level indicators * Main Conservator Tank can have a Bellow * It has an oil filling provision * It has an oil drain valve * Provision is there for connecting a Breather
  1. SILICA GEL BREATHER:
  • Prevents Moisture Ingress. * Connected to Conservator Tank * Silica Gel is Blue when Dry; Pink when moist * Oil Seal provides a Trap for Moisture before passing thro Silica Gel
  1. COOLING:
  • ONAN .. Oil Natural Air Natural * ONAF .. Oil Natural Air Forced * OFWF .. Oil Forced Water Forced * ODWF .. Oil directed Water Forced. * By Forced Cooling, the Transformer capacity can be increased by more than 50%
  1. BUSHING:
  • Insulators and Bushings are built with the best quality Porcelain shells manufactured by wet process. * For manufacture of electro porcelain, high quality indigenous raw materials viz, China Clay, Ball Clay, Quartz and Feldspar is used Quartz and feldspar are ground to req…