Electrical Earthing or Grounding

The term ground or grounding is familiar in countries like USA/Canada/Japan which is defined by IEEE Standard Dictionary ‘Conducting connection to the earth’. The term earthing or earth spelt in UK, Europe and IEC Standards. Ground means Earth.
3 phase AC system neutral points are connected to earth or a DC rectifier system to earth is called neutral grounding or system grounding. Earthing connection of non-current conducting metallic accessories which are inbuilt with electrical installation devices or machines is called equipment body earthing. System ground refers to connecting neutral point to earth. Equipment grounding refers to a connection or non-current carrying metallic parts to earth. Earth is the highest good conductor of electricity and can absorb unlimited charge with no rise in voltage. Hence the earthed point of the equipment always is at very low potential.

System earthing or grounding

Intentional connectivity of equipment or appliance neutral point to earth is called system earthing. If a neutral point is ground, the phase to earthing voltage is at earth fault condition so it does not increase to a high value. Earth fault protective mode becomes easy; hence it is a universal practice to have a neutral earthing at all voltage level.

Equipment earthing or grounding

It is quite different from neutral grounding. Equipment earthing is connecting to earth from non-current carrying metallic spares parts. The non- current carrying metal parts include motor body, switchgear structure, transformers, sheaths of heavy cable body of portable appliance body structure etc..

Equipment earthing ensures safety

The potential of an earthed device will not reach unsecured high values since they are connected to earth. As the earth fault current flow through the earthing and may readily does the operation of fuse or on earth fault relay, circuit breaker and faulty part are cut off automatically from the system. If equipment earthing is not provided or not maintained properly, the fault current will pass by contact through the human body to a ground source and cause high dangerous shock.