Page 55 - Practical Power System and Protective Relays Commissioning

52 Practical Power System and Protective Relays Commissioning

FIGURE 5.4 OFWF oil and water are circulated in closed loop by pumps. OFWF, Oil forced
water forced.

TABLE 5.1 Transformer Cooling Methods

Symbol Title Description
ONAN Oil Transformers are radiators for oil natural circulation
natural
Air
natural
ONAF Oil The radiators are provided with cooling fans. Fans are
natural switched on in two stages
Air
forced
OFAF Oil The oil is circulated through coolers by pumps. The coolers
forced have cooling fans to exchange heat from oil into air
Air
forced
OFWF Oil The heat is exchanged from oil to cooling water. Both oil
forced and cooling water are circulated through radiator by pumps
Water
forced
AN Air The ambient air is used for cooling
natural