Safety in Grounding IEEE STD 80 | Basic Problems

This article is about basic problem in grounding of substation and conditions for danger. In this topic, we cover two main topics of

1. Basic Problems in Grounding
2. What conditions of danger

Safety in Grounding IEEE STD 80 | Basic Problem

There are two main purposes of safe grounding designs.

1. In case of normal and fault conditions, to provide main source to carry electrical current into the earth or ground without effecting normal operation of equipment.
2. A person must not be in danger of electric shock or exposed in grounded facilities.

Typical faulted substation with and without multiple ground return paths

For instance, if a substation is supplied from an overhead line with no shield or neutral wire, a low grid resistance is important. A substantial part of the total ground fault current enters the earth causing an often steep rise of the local ground potential; Fig 2 (a).

If a shield wire, gas-insulated bus, or underground cable feeder, etc, is used, a part of the fault current returns through this metallic path directly to the source. Since this metallic link provides a low impedance parallel path to the return cir­cuit, the rise of local ground potential is ultimately of lesser magnitude; Fig 2 (b ).

Read Also: AC Substation Grounding Safety as per IEEE

Conditions of Danger in Substation

Equipotential Contours of a Typical Grounding Grid With and Without Ground Rods

The circumstances that make electric shock accidents possible are:

1. If there is high fault current sinks to ground in proportional to area and resistance of ground system to remote earth.
2. High potential gradients can happen at some points of earth surface by soil distribution and distribution of ground currents.
3. Sometimes due to high potential difference bridging between two points, can harm individual at such point, time and position.
4. Contact resistance and other series resistance is very important to limit current through body for a safe value.
5. Duration of the fault and body contact, and hence, of the flow of current through a human body for a sufficient time to cause harm at the given current intensity.

There is following document to complete understanding of Basic Problems for Safety in Grounding as per ANSI/IEEE STD 80.

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