Why a grounding electrode is required

[Grounding4me]

Hello,

I was wondering, if there is a grounding electrode at the utility supplying the power, why is one required at the main disconnect panel at a building? Since a fault cannot use the ground path from the service disconnect back to the utility ground as its return. Is it solely for lightning protection? Please explain why it is needed, thank you.

 

[A/A Fuel GTX]

The purpose of the grounding electrode system is to remove high voltage surges caused by lightning and unintentional contact with higher voltage lines on the premises wiring system. It also stabilizes phase to ground voltage during normal operation and during line to ground faults.

 

[steve66]

The grounding electrode helps ensures that the ground wire and the ground around the structure (picture a concrete slab for example) are at the same voltage (or at about the same voltage).

The ground electrode at the utility transformer may be quite a distance from the structure, so it doesn't necessarly ensure this. There could be a voltate drop along the ground wire going back to the transformer, or there could be a voltage gradient through the ground.

 

[petersonra]

The grounding electrode helps ensures that the ground wire and the ground around the structure (picture a concrete slab for example) are at the same voltage (or at about the same voltage).

The ground electrode at the utility transformer may be quite a distance from the structure, so it doesn't necessarly ensure this. There could be a voltate drop along the ground wire going back to the transformer, or there could be a voltage gradient through the ground.

That sounds good but in most any good sized plant, the service GE may be 100's of yards away. there is no requirement to prevent voltage gradients. even in a typical residence there is no real guarantee nor any performance requirement for the GE connection to actually do anything at all, other than to exist.

 

[A/A Fuel GTX]

That sounds good but in most any good sized plant, the service GE may be 100's of yards away. there is no requirement to prevent voltage gradients. even in a typical residence there is no real guarantee nor any performance requirement for the GE connection to actually do anything at all, other than to exist.

Agree....Lightning has a mind of it's own. We offer it a nice easy path to ground but sometimes it becomes defiant.

 

[Jon456]

Hello,

I was wondering, if there is a grounding electrode at the utility supplying the power, why is one required at the main disconnect panel at a building? Since a fault cannot use the ground path from the service disconnect back to the utility ground as its return. Is it solely for lightning protection? Please explain why it is needed, thank you.

The ground fault current (green) in the attached picture is following the path of the EGCs (Equipment Grounding Conductors). An EGC provides a low-impedance path, for bonding purposes, from the load back to the OCPD so that any fault will cause the OCPD to trip and interrupt power to the fault.

A grounding electrode is to provide a low impedance path for lightning to get into the earth; it is connected to service equipment via a GEC (Grounding Electrode Conductor). This is shown as orange in the picture.