20

It is not usual to monitor this directly due to risk of insulation failure with devices embedded in the winding; normally oil temperature is monitored and an additional heating element fed from a current transformer measuring load current is used to simulate the winding ‘hot spot’ temperature within the monitoring device.

3.3.5 Compensation Equipment

There are several forms of compensative equipment, such as :

a) Synchronous Compensators b) Shunt Reactors c) Mechanically Switched Shunt Connected Capacitor Banks (MSC) d) Mechanically Switched Damping Network (MSCDN) e) Series Capacitor Banks f) Static Var Compensators (SVC)

3.4 SUBSTATION LAYOUT ARRANGEMENT

3.4.1 Single Bus

The most simple electrical arrangement which, without a bus section, has poor service continuity, no operational facilities and requires a shut down for any extension. It is more common at the lower voltages especially with metalclad switchgear. When fitted with bus section isolators with or without a bus section circuit breaker, the service continuity and operational facilities improve slightly and extensions are possible with only part shut down. Note that with some circuits (e.g. transformers) the circuit side isolator may be omitted.

Fig 1 – Single Bus

3.4.2 Double Bus

A very common arrangement nearly always incorporating a bus coupler circuit and often a bus sectionalising arrangement. It has very good service continuity and operational facilities and can be extended with little or no shutdown depending upon the physical arrangement.