02.What is the need of power system protection?
Power system protection is very important for ensuring the ,
People Safety
Equipment safety
Reliability
People Safety
The primary aim of protection is to minimize the risks associated with electrical hazards when a fault occurs in the system.
For example, consider a transformer operating under load conditions. If a fault occurs in the connected feeder, the conductor may catch fire due to the persistence of the fault in the network. This poses a serious safety risk to anyone nearby.
In some cases, a transformer may even burst due to overheating caused by system faults.To prevent such dangerous scenarios, an efficient and reliable protection system is essential.
Reliability
The protection system detects faults and quickly isolates them from the healthy part of the network. This rapid response ensures that the fault is cleared before it can cause significant damage to the equipment. As a result, the time required for troubleshooting is much less than the time and cost involved in repairing or replacing damaged equipment, thereby increasing the overall reliability of the system.
Main components in Protection system
Here, we can identify the main components used in a protection system.
Protection relays are key devices that detect faults using input from measurement units, such as Current Transformers (CTs) and Potential Transformers (PTs), which are connected to the feeder circuit to monitor current and voltage levels.
A battery system plays a crucial role by powering the control circuit, which ensures the operation of circuit breakers and protection relays to isolate faulted sections of the network.
How does protection system works?
Here, we can observe how the protection system functions.
The transformer supplies power to the load through a closed circuit breaker (CB). When a fault occurs, the Current Transformer (CT) senses the abnormal current and becomes energized, triggering the protection relay.
In this example, the relay operates on the induction principle. The energized electromagnet induces an electromotive force (EMF) on a rotating disc. As the disc turns, it eventually closes from Normally Open to Normally Closed (NC) contact, completing the trip circuit, which in turn opens the circuit breaker to isolate the fault.
Equipment safety
Protection systems safeguard electrical equipment during faults and abnormal operating conditions. Without protection, such faults can cause severe damage to equipment, leading to high repair or replacement costs, and extended downtime before the equipment is back in service. Such scenarios, an efficient and reliable protection system is essential.
Normal working condition after fault clearance
You can see here that the fault is detected and controlled by the relay and circuit breaker. Once the fault is cleared, the relay returns to its default position, as the circuit breaker has already interrupted the fault current. After troubleshooting and resolving the issue, the feeder is ready to resume supplying power.
