External Causes of Failure and Abnormal Operation of Equipments
Q. What are the external causes of failure and abnormal operation of equipments.
External Causes :
- A 3 – phase machine is supplied with 3-line wires L1 L2 L3. These are called as lines. If the fault is developed in the feeder / Distributor line only two lines will supply the equipment. The two lines supply the power to 3 phases of machine and two phases become excessive of load and over heating take place and machine condition becomes abnormal (single phasing on distributor side).
- Sometimes due to wind, rains, birds etc. short circuit occurs in the supply system which affects working of machine instantly.
- If supply system generator working in generating station is subjected change in the speed of prime mover, then supply frequency changes which affects the working of machine connected to this supply system.
- Sometimes in the generating station / receiving station / substation there occurs overvoltage or under voltage which affect the normal working of the machine.
- Some times negative sequence currents are developed due to unbalance supply system which affects the normal working of the machine.
- If external load on the machine is sustained for a length of period, the insulation may start burning due to excessive temperature rise.
These external conditions affect the performance of machine and abnormalities are developed.