Grounding System

Grounding System

Introduction

In any electrical circuit network, the circuitry that provides a path between the parts of the circuit and the ground, is known as the grounding system. The grounding system is required for reliable operation of any electrical equipment including generator, transformer, power system tower, and other power system installation under fault conditions. In a grounding system, the study of ground resistance is very important in designing any electrical network for residential, commercial and industrial areas. Any electrical equipment needs to be grounded for safe operation. In this case, the enclosure of the equipment is grounded in such a way that the voltage on the equipment maintains the voltage of the ground. This is known as equipment grounding. The grounding is also an important for power generation, transmission and distribution systems. In the transmission systems, each leg of the transmission tower is grounded through a vertically inserted earth electrode. In an electrical substation, all high voltage equipment are grounded with a grounding grid system. In this chapter, objectives, symbols, expression of ground resistance with different types of electrode etc. have been discussed.

Objectives of Grounding System

The objectives of any grounding system are as follows:

Reduce insulation level of power system equipment

Power system equipment like transformer’s neutral must be grounded. This can decrease the operating voltage and insulation level of the equipment.

Ensure personal safety

A good grounding system of a substation can ensure that the touch and step voltages meet the standard voltage levels.

Eliminate electrostatic accidents

Static electric current may create interference of electronic devices and generate fire near any flammable object. A good grounding system can release the static current to the earth which can prevent that type of incident.

Reduce electromagnetic interference

The normal operation of any electronic device is interrupted due to electromagnetic interference. This type of interference can be reduced by the good grounding system.

Reduce cathodic protection current

The voltage is usually induced in the pipeline at the same corridor of the transmission lines which can harm the utility operators. The cathodic protection is used in the pipeline to mitigate high touch potential and reduce the current due to a fault condition. Therefore, the cathodic protection system of the pipeline must be grounded to release the current into the earth.

Detecting ground faults

In the substation, there are many leakage breakers and other fault leakage protection devices used in the low voltage circuits. A high magnitude of the ground fault current is required to bring the protection device into action, if there is an earth fault in the circuit. Therefore, to meet this condition, the neutral point on the secondary side of the step-down transformer must be grounded.

Grounding Symbols and Classification

In the grounding system, three symbols are used which are signal, chassis and earth.