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Electrical energy is generated at various power station & is transmitted & distributed to the consumers. There are various faults which may occur in the system during transmission & distribution of electric power.
Types of faults in overhead system
Short circuit fault is the most common fault in an overhead system. This may occur in the system due to insulation failure caused by over-voltage or due to broken conductors.
The various faults occur in a three phase overhead system are :
1. Single phase to earth
This may occur when one of the conductors of transmission lines breaks & falls on the ground or guard wire.
2. Phase of phase
This may occur when one of the line conductor breaks & falls on the other line conductor. The major cause of this type of fault is the heavy wind. The heavy wind swinging the line conductors which may touch together & hence cause short-circuit.
3. Two phase to earth
This may occur when two conductors of three phase transmission line break & fall on the ground or guard wire.
4. Phase to phase & third phase to earth
This may occur when one of line conductor breaks & falls on the other line conductor whereas the third conductor falls on the ground or guard wire.
5. All the three phase short circuited
This may occur, if two conductors of transmission line fall on the third line conductor.
6. All the three phase to earth
This may occur, if all the three conductors break & fall on the earth or ground wire or they fall on any other object which is further ground.
Whenever any of the faults occur in a transmission line, the line is disconnected from the power system by the protective relays provided at substation. All the faults shown in figure. Out of all the six faults, the first four faults are called unsymmetrical faults because these faults give rise to unsymmetrical currents. The number 5 & 6 are called symmetrical faults because they gives rise to symmetrical currents.
Read Also :
- Main Components of Overhead Lines
- AC and DC System : What is AC And DC Transmission System
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