Grounding is important in an electrical system since it provide the lowest resistance path to the ground. Circuit protection device such as circuit breakers have maximum allowable resistance to operate properly. In case that the required value of resistance goes beyond the allowable value, it will not trip in due time. The right value of earth fault loop impedance is needed.
For example, the table below shows the maximum value of overall earth fault loop impedance in order to comply with BS 7671 and IEC 60364 to disconnection time.
In general, the following are the purpose of effective grounding.
- To provide safety to personnel during normal and fault conditions by limiting step and touch potential.
- To assure correct operation of electrical/electronic devices.
- To prevent damage to electrical/electronic apparatus.
- To dissipate lightning strokes.
- To stabilize voltage during transient conditions and to minimize the probability of flashover during transients.
- To divert stray RF energy from sensitive audio, video, control, and computer equipment.