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6 Factors Influencing Requirements for a Good Grounding

System

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Grounding of cable trays

Limits the system-to-ground or system-to-frame voltage to values safe for personnel.

Provides a relatively stable system with a minimum of transient overvoltages.

Permits any system fault to ground to be quickly isolated.

2. Grounding of Metallic Parts

Proper grounding of metallic

enclosures and supportstructures that are part of the

electrical system and may be

contacted by personnel. Also to

be included are portable

electrically operated devices.

Consider that only a

small amount of electric 

current – as little as 0.1

 A for one second – can

be fatal! An even smaller 

amount can cause you to

lose muscular control .

These low currents can

occur in your body at 

voltages as low as 100 

V, if your skin is moist.

3. Static Electricity

Protection against static electricity from friction. Along with this are the attendant hazards of shock, fire and

explosion.

Moving objects that may be inherent insulators – such as paper, textiles, conveyor belts or power belts and

rubberized fabrics – can develop surprisingly high charges unless properly grounded.

4. Direct Lightning Strokes

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Illustration of direct and indirect lightning strokes

Lightning strike on lightning rod

Protection against direct lightning strokes. Elevated structures, such as stacks, the building proper, and water 

tanks may require lightning rods connected into the grounding system.

5. Induced Lightning Voltages

Protection against induced lightning voltages. This is

particularly a factor if aerial power distribution and

communications circuits are involved.

Lightning arresters may be required in strategic

locations throughout the plant.

6. Low-resistance Ground Connections

Providing good grounds for electric process control

and communication circuits.

With the increased use of industrial control

instruments, computers, and communications

equipment, accessibility of low-resistance ground

connections in many plant locations – in office

and production areas – must be considered.

Reference: Getting down to Earth – A practical guide

to earth resistance testing – MEGGER 

About Author //

Edvard Csanyi

Edvard - Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV high power 

http://electrical-engineering-portal.com/http://www.csanyigroup.com/http://electrical-engineering-portal.com/case-study-improper-grounding-practice-of-computers-in-buildings

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