DC voltage in Substation?

Why DC voltage use in Substation? In substations, DC supply is generally used for powering control circuits. You might wonder why we use DC or why not AC instead. Let me explain the main reasons for using DC in power substations.

The primary reason for using DC power supply in the control circuit is to provide a continuous power supply to the control circuitry. DC electricity is a reliable source because it can be obtained from batteries. It can supply uninterrupted electricity as long as the battery remains charged. Batteries have the capacity to store electrical energy, making them suitable for backup power supply.

In a substation, there are numerous control circuits for operating switchgears, circuit breakers, isolators, and relays, which are kept in the On state.

So, where is the inconvenience in using AC supply?

If we use AC supply and experience a power trip, we won’t be able to provide power supply to the control circuit. In case of a power trip, when all devices stop functioning, we won’t be able to examine faults, circuit breakers, and relay statuses.

Thus, even during a power outage, we need to ensure an uninterrupted power supply to the control circuit. Since we can only provide power supply using batteries, and batteries can only supply DC power, the entire control circuitry is designed for DC supply.

Other Uses:

In a substation or power station, DC supply is also used for operating circuit breakers (opening and closing them), protective relays, isolators, indicator lights, alarm circuits, PLCC (Power Line Carrier Communication) panel, emergency lights in the control room, and more.

Using DC supply instead of AC supply in substations comes with some additional benefits:

• Protective devices respond much faster when operating on DC supply compared to AC supply.
• Static devices that require DC supply can be directly connected to batteries. However, when using AC supply, a rectifier circuit is needed.

Control circuits consist of many digital devices, such as digital displays, sensors, LEDs, etc., and these devices always need DC supply. So, using DC supply in the control circuit reduces the need for complex circuitry.

In conclusion, DC voltage is essential at substations due to its reliability, especially in powering control circuits and providing backup power. Its use allows for better operation and management of the substation’s equipment and devices.