Grounding systems are required not only to ensure the safety of the personnel and the safe operation of equipment but also to protect the system from lightning and ensure accurate measurement of electrical parameters. Here are a few factors that influence the requirements for a good grounding system.
The following are the major factors influencing the requirements for a good grounding system:
- Limiting the voltage to earth of the entire system to a definite value.
- Protection against electrocution.
- Protection against static voltages.
- Providing clean earth for process instruments and communication circuits.
- Protect the system from lighning strokes.
- Protection against induced lightning voltages.
Limiting the voltage to earth of the entire system to a definite value
It is necessary to maintain some point in the system at the ground potential in order to ensure the following:
- Maintaining a ground potential at some point avails a reference point that can be used to limit the voltage to which the system-to-ground insulation is subjected. This can help in more accurately determining the insulation rating.
- The system to ground voltage can be maintained.
- The frame to earth voltage can be limited to a value safe to personnel.
- By limiting the voltage to earth of the entire sytem to a particular voltage, any system fault to ground to be quickly isolated.
- Improves system stablity and minimizes transient overvoltages.
Protection against electrocution
Accesible conductive surface must be properly earthed since small currents as little as 0.1 A for one
second can be fatal. Protective earthing conductors helps in maintaining the potential of these conductive parts close to the earth potential in fault conditions, and thereby reducing the risk of electric shocks.
Protection against static voltages
Static discharges occurs around us so naturally. But when moving insulators such as paper, textiles, conveyor belts or power belts and rubberized fabrics – can develop surprisingly high charges unless properly grounded.
Providing clean earth for process instruments and communication circuits.
A good grounding system can prevent malfunctioning of process instruments and communication circuits. The clean earth ensures that the induced interferences from the power system does not cause the instruments to malfunction.
Protect the system from lighning strokes
Elevated structures like water tanks, stacks, and the building itself might need lightning rods attached to the grounding system.