WHAT IS THE NEED FOR POWER SYSTEM PROTECTION?

The power system network in any region or country constitutes the backbone of it's economics development and is necessary for improving the quality of human life.

POWER SYSTEM PROTECTION:

This necessitates the effective, reliable and effective operation of the power system. For economic reasons, The components of a power system, i.e. Alternators, Transformers, Reactors, Circuit Breakers, Bus Bars, Transmission systems, Distribution systems, etc. are all generally designed for normal operation of the network. In the event of an abnormality in any section of the power system network, It is essential to isolate the faulty section from the healthy sections and may result in a major blackout.

So, if abnormality takes place in any section of the power system network, the affected component should immediately be isolated from the rest of network in order to restore power in the remaining sections. The isolation of the faulty component from the rest of the section is undertaken by the protection scheme, which includes protective relays and switch gears, i.e. Circuit Breakers. It is thus imperative to design an appropriate protection scheme for the proposed power system at the planning stage itself. The primary function of the relay is to operate only if a fault occurs and not under normal operating conditions. A protective relay sense the fault, identifies the location of the fault and sends a trip command to the appropriate circuit breaker which disconnect the faulted section.

Under normal conditions, changes occur in the electrical quantities like voltage, current, frequency and phase angle. In order to detect abnormal conditions in any section of the power system, a relay utilises one or more of these electrical quantities. Abnormal conditions in the power systems include:

• Short circuits in the transmission or distribution lines.
• Over voltages due to switching or lighting.
• Overheating of the stator and rotor of the machines.
• Loss of excitation of the machines.
• Over speeding of generator or motors.
• Insulation breakdown between the inter coils of the windings.
• Low oil levels in the transformers and circuit breakers.

Power system protection

It is thus evident that even if all possible precautions are taken in the power system design, there is a need to design a proper power protection system as well, in order to detect intolerable or undesirable conditions such as above within an assigned area. The protective relay system so designed must therefore be reliable and fast in operation, besides being maintainable.