Electrical Engineering ⇒ Topic : Protection against over voltages

PROTECTION AGAINST OVER VOLTAGES

Over voltages may be caused by conditions external or internal, to the system ; a convenient classification given below :

A. Internal Causes

1. Sudden change in load

2. Switching operation of an unloaded line

3. Insulation failure

4. Arcing grounds

5.Resonance

6.Sudden opening of loaded line, particularly under short-circuit conditions.

B. External Causes

These are mainly due to atmospheric conditions, i.e., due to lightning.

The devices used for protection of electrical equipment from surges or over voltages are known as over-voltage protection devices, these are enumerated below :

1. Ground wire

2. Earthing screen

3. Surge diverters or lightning arresters

4. Surge absorbers