Electrical cloud of answers, Unlimited study Notes, and Downloads with videos
substation which is used for all voltage levels between 55 KV to 765 KV is called outdoor substation. ... The outdoor substations are mainly classified into two types, namely pole-mounted substation and foundation-mounted substations.
Pole Mounted Substation
Foundation Mounted Substation
substation in which the apparatus is equipped inside the substation building is called indoor substation.
indoor substation is subdivided into several compartments like control compartment, indicating and metering instruments and protective device compartment main bus-bar compartment, current transformer and cable sealing box compartment as shown in the figure below.
Concept of using DC supply in substation or power stations is to provide a continuous power supply to the control circuit. DC is a reliable source of power supply because it can obtain from batteries. ... So during power failure also, we have to provide the continuous power supply to the control circuit.
If we use AC supply which can not be obtained from the battery then we cannot provide the power supply to the control circuit during the power failure. If a power failure occurs, all devices will stop working then we cannot check the fault status, status of the circuit breaker and relay.
So during power failure also, we have to provide the continuous power supply to the control circuit. As we can provide continuous power supply only using battery and battery can provide only DC supply, so all control circuit devices are designed for DC Supply.
In a substation or power station, DC supply is used for Opening and Closing of Circuit breakers, to operate protective relays, to operate isolators, indication lamps, alarm circuits, PLCC(Power Line Carrier Communication) Panels, Emergency Lights in Control Rooms, etc.
Using of DC supply instead of AC Supply in Substation also gives some extra facilities such as,
1. When protective devices are operating with DC supply they take very less reaction time than when they are operating with AC Supply.
2. Static Devices or which need DC supply can be directly connected with batteries. But when AC supply is used, the rectifier circuit is needed.
3. Control Circuits are consist of many digital devices also such as Digital Displays, Sensors, LEDs, etc. These devices always need DC supply. So when using DC supply in the control circuit fewer circuits are needed.
