The document discusses the basics of grounding electrical systems and equipment. It covers lightning and its effects, static charges and the need for bonding. The objectives of grounding are to detect insulation failures and correctly identify fault locations. Various types of ground electrodes and factors in choosing electrodes are described. Special considerations for installations with sensitive electronic equipment include reducing ground loops and voltage spikes.

1. Practical Earthing, Bonding, Lightning and Surge Protection
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

2. Overview
• Basics of grounding of electrical systems and equipment
• Lightning and its effect on buildings, structures and electrical
systems
• Static charges and need for bonding (to ground)
• Ground electrode system
• Dealing with installations having sensitive electronic equipment
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

3. Objective of grounding
• Detecting the failure of insulation and the point of failure
so that repairs can be undertaken
– A ground reference is essential to:
• Permit a fault current through the point of failure to enable detection
• Correctly pinpoint the faulted location for selective isolation
• Clamping the voltage of external enclosures of electrical
equipment to that of ground
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

4. Fault in an Ungrounded System
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

5. Effect of Grounding the Neutral
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

6. 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’s insulation 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
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

7. Dissipation of Static Charges
• Figure above shows a charged body A
and another body B (isolated from A)
• Figure on top right shows a spark
discharge from A to ground and to
unearthed body B
• Fig on lower right shows A bonded to
earthed body B causing charge to drain
away
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

8. 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
(metallic water piping is an example)
– Adopt different physical configurations
– Follow different designs
– Must conform to local electrical installation standards
• An example is shown next
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

9. A typical ground electrode
Materials:
• Copper
• Copper clad steel
• Galvanised steel
• Copper clad stainless
steel
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

10. A typical chemical electrode
• Sometimes called a leach
electrode
• Chemical mixtures are added
to lower resistance of soil
• Needs regular maintenance
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

11. 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 will dictate grounding
• Presence of agents that can cause corrosion of
electrode parts buried in ground.
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

12. Installations with Sensitive Equipment
• Grounding of sensitive devices need special care
because:
– they work at very low power and voltage levels
– cannot tolerate even small overvoltages or currents
– are prone to interference to their signal lines from adjacent
circuits
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

13. A Typical Ground Loop
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

14. Inductors as Source of Voltage Spikes
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)
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

15. Uninterrupted Power sources
• Power supply networks are prone to voltage
fluctuations/interruptions
• Even momentary interruptions cause computer systems and other
process control systems to restart (reboot).
• UPS systems can prevent these problems
• UPS systems can either be of
– Electromechanical type (using an engine-driven generator as the source)
– Static type (using thyristor/ transistor inverters with a standby battery
source)
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss

16. DO YOU WANT TO KNOW MORE?
If you are interested in further training or information, please
visit:
http://idc-online.com/slideshare
Technology www.idc-online.com/slideshare Technology TTrraaiinniinngg tthhaatt Wwoorrkkss