These Transformers are the popular and commonly produced type of Transformers. They range from small pole mounted transformers to very large transformers seen openly in distribution yards and substations. Typically robust oil-natural, air natural (ONAN) cooling is used due to the remoteness of the installation site and added complexity of other cooling options.
LARGE DISTRIBUTION TRANSFORMERS:
RANGE: 5000kVA to 20 000kVA
PRIMARY VOLTAGES: up to 33kV
TAPPINGS: Off-circuit Tap switch (OCTS) or on-load Tap Changers (OLTS)
TAPPING RANGE 2,5% to 5% (OCTS) or 5% to 15% (OLTS)
TERMINATION: HV & LV Outdoor open bushings or : HV & LV cable boxes
TANK CONSTRUCTION: Free breathing with bolted on lids, flat under base or Skid base
COOLING: ONAN/ONAF
FITTINGS: Lifting lugs, earth terminal, surge arrestor brackets when requested, rating & diagram plate, drain & filter valve, Jacking pads, Oil level indicator, Oil temperature indicator, winding temperature indicator, dehydrating breather.
STANDARDS: SABS, SANS 780
SMALL and MEDIUM TRANSFORMERS:
RANGE: 5kVA – 5000kVA
PRIMARY VOLTAGES: up to 33kV
TAPPINGS: External Tapping connection (single phase) or of circuit Tap-switch (OCTS)
TERMINATIONS: HV Outdoor open bushings or HV & LV cable boxes
TANK CONSTRUCTION: Sealed welded cover or sealed bolted cover.
COOLING: ONAN
MOUNTING ARRANGEMENT: Pole mounting with brackets or flat base for pole mounting platform mounting
STANDARDS: SABS, SANS 780
