Page 53 - Practical Power System and Protective Relays Commissioning

50 Practical Power System and Protective Relays Commissioning

FIGURE 5.1 Parts of a power transformer.

The Buchholz relay is a relay with two floats or buckets; one for alarm
and the other to trip the transformer (see Fig. 5.2).
Bushings to isolate the electrical circuit of the power transformer from
the tank. This is usually composed of an outer porcelain body that is
suitable for high voltages, and also an oil-impregnated paper as insulation
within the porcelain column of bushing.
Pumps, fans, and radiators as a part of the cooling system of transformer.
Vacuum valves.
Liquid handling valves and sampling valves.

5.3 TRANSFORMER COOLING SYSTEM
When discussing transformer cooling systems, the following terms are used:

Internal cooling medium oil, referred to as (O)
External cooling medium air, referred to as (A), or water, referred to
as (W)
Type of circulation, referred to as natural (N) or forced (F).