Earthing system works & installing in home.pdf

Earthing System

1. Earthing
Md. ZubairAlamEmon,
Lecturer, Dept. Of EEE,
United International University

2. Earth, Neutral & Ground
•Neutral is the return path for normal current.
•Earth is the return path for abnormal current(faulty equipment).
•Earthingcreates a less resistive path than human body, so faulty current flows
through Earthingrod/plate/pipe etc.
•The green connection at the secondary of the Transformer supply side is known
as ‘grounding’.
L
E

3. EarthlessHazard
•Without earthingabnormal current flows through human body.

4. Earthingused in Electrical Installation for
Buildings
Theusualmethodofearthingistojointheexposedmetalworktoearthviaasystemof
EarthContinuityConductors(ECC)connectedtoanEarthElectrodeburiedintheground
throughasystemofEarthLeadWires.Inconjunctionwithafuse,orothersimilardevice,
thisthenformsaprotectivesystem.Thus,ifaliveconductoraccidentallycomesinto
contactwithanexposedmetal,thefuseorprotectivedeviceoperates.Aslongasthe
overallresistanceoftheprotectivesystemislow,alargefaultcurrentflowswhichblows
thefuse.Thiscutsoffthesupplyandisolatesthefaultycircuit,preventingriskofshock,
fire,ordamagetoequipment/installation.
Following types of earthingsare required to be installed:
•L.T. Circuit / System Earthing,
•Equipment Earthing(LT side),
•Substation Neutral Earthing,
•Substation LT System Earthing,
•H.T. Circuit earthingfor a Subtation

5. Integral parts of an EarthingSystem
a)Earth Electrode(s) buried under the
ground
b)Earth Lead Cables/ Wires connecting the
Earth Electrode(s) with the Earthing
BusbarSystem. Earth Lead Cables/
Wires are also need to interconnect the
Earth Electrodes when there are more
than one Earth Electrode.
c)Earth Continuity Conductors (ECC) for
linking EarthingBusbarat the Substation
LT panel or main distribution DB of a
building.
d)Earth Electrode Clamp.

6. Various types of Earthing

7. Plate Earthing
•Copper/ GI plate is
used.
•Wire connection made
through bolt or nut
made of copper / GI.
•Alternative layers of
charcoal and salt is
used.

8. Pipe Earthing
•GI pipe is used
•Permanent wet soil is necessary.
•Coal and salt is used to reduce resistance.

9. Rod Earthing
•Temporary earthingsystem, GI pipe/ Galvanized Iron is used.
•Used in sandy soil.
•Cheapest method.

10. Strip Earthing
•Used in rocky area.
•Pipe electrode is placed horizontally.
•Conductor length is >15m.

11. Things to remember
•You may need multiple ‘EarthingElectrodes’ based on your
need.
•Multiple electrodes provides less resistance and must be
internally shorted.
•Earth resistance is kept between 0.1 to 5 Ω. For Substations
its 0.1 Ωand residential building may have 5 Ω.
•Earthingdepends on soil quality (resistance, humidity,
salts, bedrocks etc.) and the place where it is installed.
Sloppy place with low humidity needs special treatment.
•Improving the Earth resistance may involve more deep and
wider pit, bigger earth electrode, more watering's etc.
•Earth resistance is measured using ‘Earth Tester’ also
known as ‘Megger’.

12. Testing Earth resistance with Megger
•3 Point Method
•Current Spike is set to 30
–50m(=D).
•Potential Spike is set to
62% of D.

13. Maintenance of Earthing
•Earthingrequires digging a pit.
•Requires watering and maintenance at regular intervals.
•3 or 4 buckets of water needs to be poured every few days into the
sump to keep the surrounding of the earth plate or pipe permanently
moist.
•New type of chemical is now available which can be used for
lessening the burden of watering and maintenance. Provides good
earthingfor 10 years.