Power System Protection – ElectricalEngineering.XYZ

This ultimate guide on power system. Covers all fundamentals concepts on Power System Protection

Power system protection is a subfield of Electrical Power Engineering which is focused on techniques and methods used for the protection of electrical power systems from faults.

Types of Faults

Faults are usually classified into two major classes.

Open Circuit Faults

Open circuits faults occur due to the failure of one or more conductors. Such faults might arise due to the failure of one or more phases of CB. They might also arise due to the melting of a fuse or a conductor either in single or multiple phases.

Short circuit faults

A short circuit fault arises due to a low impedance path between two different phases or between two points that have different potential. Short circuit faults are classified into different types. Given below is a brief list of different types of short circuit faults and severity:

Power System Protection Components


The fuse is an electrical protection device that provides overcurrent protection to the connected electrical circuit.

In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. A fuse is actually a short piece of metal that is inserted in the circuit. In case of excessive current flow, the wire elements melt thus interrupting the current in the circuit.

Circuit Breaker

A circuit breaker is a protection element that is employed for the protection of electrical systems in residential and commercial areas. It is an automatically operated electrical switch which protects the electrical circuit from damages caused by excess currents.

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A relay is responsible for detecting the fault. Once the fault is detected the relays supplies information to the circuit breaker which takes action and interrupts the circuit.

Similar reading: 20 Different types of relays use in Power System Protection

Protection Transformers

The terms Protection transformers (also known as instrumentation or instrument transformers) is referred to the current and potential transformers. Both current and potential transformers are employed to step down the high voltage and current levels of the power system to a safe level (that is acceptable for relays and other measurement devices)

Performance measurement of Power System Protection

A power system protection should meet following criterian:

ReliabilityThe protection system should function consistently. In case of fault conditions, it should operate. Even, if it is idle for many months, it should function perfectly when there is a fault condition.
SpeedThe devices should quickly operate so as to reduce the damage
SelectivityDevices should avoid false trips
SensibilityThe power system should be alive to select the fault current. It should be sensitive enough to detect the presence of the smallest faults.

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