Few topics generate as much controversy and argument as that of grounding (or earthing as it is called in some countries) and the associated topics of lightning and surge protection of electrical and electronic systems. Any engineer dealing with power supply networks needs to understand the basic principles of grounding system design and its role in ensuring safety of equipment and personnel. A correct understanding of the basic principles involved will help him/her to avoid mistakes in grounding system design, mistakes that could lead to expensive failures and long downtime. In this workshop, we will try to demystify the concepts of grounding as applicable to utility networks and industrial plant distribution systems as well as their associated control equipment. In fact, a lot of myths have been built around this subject, although it is quite a simple one when approached from basic principles. Our endeavour will therefore be to explain the fundamentals of grounding, which we hope will enable the participants to gain a correct perspective of the subject and give them the knowledge needed to solve real life grounding problems. Essentially this workshop is broken down into system grounding, protective grounding and surge/noise protection of power and electronics systems normally found in distribution networks. A brief introduction to the design of substation grounding has been included. Detailed information on ground electrodes and measurement of ground resistance is also available. WHO SHOULD ATTEND? Building service designers Consulting engineers Data systems planners and managers Electrical and instrumentation technicians Electrical engineers Instrumentation and control engineers Maintenance engineers Power system protection and control engineers Project engineers MORE INFORMATION: http://www.idc-online.com/content/earthing-utility-and-industrial-distribution-systems-28

1. Earthing of Utility and Industrial
Distribution Systems
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2. Overview:
• Basics of system grounding and protective grounding
• Bonding and its role in safety
• Ground electrodes, configurations and ground electrode
resistance
• Grounding design of electrical substations
• Static electricity and grounding needs for safety against
static discharge
• Lightning and grounding of lightning protection systems
• Surge protection approach
• Noise mitigation by proper grounding practices
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3. Objectives of grounding:
• Provides an electrical supply system with a reference to the groundmass
(system grounding)
• Protective grounding of electrical equipment enclosures
– Makes them safe to persons who may come into contact with them
– Enables the flow of fault current in the event of a failure
• Provides a low impedance path for accumulated static charges and surges
(lightning protection grounding)
• Helps in mitigating the generation and propagation of noise (grounding of
shields and signal reference planes)
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4. Fault in an Ungrounded System:
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5. Effect of neutral (system) grounding:
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6. Ground fault current flow:
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7. Ground electrodes:
• The connection to ground mass is normally achieved by a
ground electrode
• Ground electrodes
– Use different materials
– Sometimes use buried facilities not specifically meant as electrodes
(water piping is an example)
– Adopt different physical configurations
– Follow different designs
– Must conform to local electrical installation standards
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8. A typical ground electrode:
Materials
• Copper
• Copper clad steel
• Galvanized steel
• Copper clad stainless steel
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9. A typical chemical electrode:
• Sometimes called a leach
electrode
• Chemical mixtures are
added to lower resistance
of soil
• Needs regular
maintenance
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10. Choice of ground electrode-Factors:
• Need for achieving minimum acceptable earth
resistance (1-10 Ohms) appropriate to the
installation
• Need to maintain this resistance all round the year
in varying climatic conditions
• Type of soil where the grounding is carried out
• Presence of agents that can cause corrosion of
elements buried in ground
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11. Grounding for charge/surge control:
• Grounding helps to drain accumulated static charges
and makes an equipment safe
• Grounding helps to conduct the energy of a lightning
strike to the soil mass
• Energy of over voltage (surge) events is dissipated
away from susceptible electrical equipment. Such
surges can result from:
– Lightning strike on or near electrical conductors
– Switching of inductive circuits
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12. Dissipation of Static Charges:
• Figure above shows a charged body A
and another body B (isolated from A)
• Figure on top right shows body B
earthed and a spark discharge from A
to ground and to earthed body B taking
place
• Figure on right shows A bonded to
earthed body B causing charge to drain
away
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13. Lightning Strike:
• Lightning is the result of charge accumulation in cloud
systems which causes:
– Ionization of air close to the cloud
– Breakdown of the air between clouds or cloud and ground
– Instantaneous dissipation of charge in the form of a lightning strike
– High current flow in the air path
• Lightning strikes to ground may involve:
– Tall structures masts or buildings
– Trees or other natural features
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14. Inductors as sources of voltage surge:
Figure on the left shows an inductor
fed by DC supply
When the current is interrupted, a
voltage spike occurs across the
inductor (see below)
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15. Installations with sensitive equipment:
• Grounding of sensitive equipment needs special care
because:
– They work at very low power and voltage levels
– Cannot tolerate even small over voltages or currents
– Are prone to interference in the signal lines from adjacent
circuits
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16. AVOID:
• Ground loops
• Voltage spikes/surges from
external and internal causes
• Harmonic noise
• Electromagnetic interference
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17. A typical ground loop:
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18. DO YOU WANT TO KNOW MORE?
If you are interested in further training or information, please
visit:
http://idc-online.com/slideshare
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