Basic electrical components available in Switchyard are: Power Transformer, Reactors,Instrument Transformers (Current and Voltage/Potential Transformer), Disconnect Switches, Bushings, Surge Arresters, Standoff Insulators and Earthing switches. Some of these components look alike and hence are sometimes misused for one another, effect of which is catastrophic to the equipment, the entire electrical network and to the personnel. This is applicable to Standoff Insulators, Lightning Arresters and Bushings, but each of them possess unique characteristic, which this paper will expatiate. In view of this, discussion will be limited to these three components, and the station Operator and Infrared Thermographers who have limited substation experience will be able to differentiate among these components. Functions, unique characteristics of each components and where they can be located in the Switchyard will be discussed. 1. STANDOFF INSULATOR Function: Standoff insulator is required to keep high voltage overhead Conductor in position and at a certain distance from conductor in other phase or neighboring equipment. It also acts as an insulator between the conductor and the ground. It pilots conductor from one electrical equipment to another (For example, from Transformer to Current Transformer). It is always mounted on an earthed support (gantry support). Unique Characteristics: It contains porcelain section that is mounted between a base plate and a top mounting plate. The base plate is fixed on the grounded support and the top mounting plate is equipped with bus support hardware, on which the overhead conductor is clamped. The porcelain section can either be called rain sheds, Skirts or petticoats. 2. LIGTHNING ARRESTER Function: This component is used to protect electrical equipment from damaging due to lightning effect. The high voltage impose on electrical equipment during lightning is discharge to ground by Lightning Arresters. Unique Characteristics: It has a similar look with Standoff Insulators and Bushings, but the unique characteristic it has is that, it has an earthing terminal at the bottom where a large ground cable is connected and runs down the structure that connects to the station ground.
It is the first component on the circuit, when an incoming line runs to the Switchyard, the first component is the Lightning Arrester, and it is always connected in parallel with the line. The same hold for Power Transformer; the first component you see parallel to the incoming line to the Transformer is Lightning Arrester. 3. BUSHINGS Function: This is the component that allows electricity to enter electrical equipment safely, preventing it from shorting to another phase. They are of different types; Oil filled bushing (oil pressed type or oil immersed type), Gas filled type and Dry solid porcelain type. Unique Characteristic: For this discussion, only Power Transformer bushings will be discussed, since it has the same physical structure with Standoff Insulator and Lightning Arrester. It unique Characteristic is that the porcelain section is between an oil expansion chamber (at the top) and a mounting flange. It contains thru stud at the tip (where incoming or outgoing wires/cables to the Transformer are terminated).Bushing is install to the Transformer through opening at the Transformer tank and is is mostly found on top of the Transformer, although, it depends on the manufacturer’s design. The station Operators, the Thermographers and any personnel working in an Electrical system need to be adequately trained before commencing any activities because any assumption make may be the last.