Hazards
Due to Improper Earthing
Earthing plays an important role in generation,
transmission and distribution of power for safe and proper
operation of electric installations, says Kamal Goliya.
The
faults in any electrical system are unavoidable.
Every electrical equipment, appliance, systems must be earthed or grounded
to obtain a low resistance path for dissipation of current into the
earth.
Earthing plays an important role in generation, transmission and distribution
of power for safe and proper operation of electric Installation.
The latest Clamp- On earth / ground resistance tester can measure within
a few minutes, ground resistance and AC current (load and leakage) by
just clamping to the grounding lines without disconnecting the circuit
or driving auxiliary electrodes.
Applications
Active Lines / Power-on (Live Electrical Installation) To measure
earth/ground resistance.
of an active line (live electrical installation), clamp the device at
earthing wire of the transformer (A), Motor (B/C), Control Panel (D)
without shutdown (Refer fig. above).
Whenever the electrical installation is to be completed, its non-conducting
parts should be connected firmly to the earth electrodes.
Power Transmission
Towers Clamp the device at
the earthing cable of the transmission pole
(tower) to get the ground resistance of soil resistivities.
Soil resistivity is a crucial factor in obtaining a “Good Earth”.
Every overhead lines, which are exposed and are liable to accident from
lightening shall adopt efficient means for diverting to earth any electric
surge due to lighting.
Telecommunication
System
To measure ground resistance of individual equipment, clamp the
device at the earthing wire of the respective equipment.
Telecommunication from the contact between the soil and the stake.
If this is poor the flow of electricity is restricted.
Passive Lines / Power – off Electrical Installation
Clamp the device at a neutral point to measure proper grounding of passive
line.
As in delta connected systems a neutral point can be obtained by insertion
of grounding transformer and current limiting resistance or impedance.
An effective grounding system is one in which the on material to limit
the induced voltage on telecommunication lines and over voltage on LV
components.
Petrol / Oil Storage Tanks Fault current entering the earth through
point, raises potential of earth at that point than remote earth carrying
result in dangerous touch potential.
Passing fault current can heat the earth conductor and potential gradient
of soil.
Hence, earthing potential rise of the surrounding earth is minimised,
the rate of potential falloff from the injection point is maximised
and the high frequency components of the lightning discharge are safely
arrested without substantial surface discharge occurring.
Telecom Signal Relay Telecast System Clamp the device at the Earthing
wire of storage tanks should be tested so as resistance of earth connection
should be minimum.
Indoor / Outdoor Electrical Appliance The ground fault current directly
has an impact on human as well as appliance safety. It is good to select
an acceptable surface material and a grounding system with a low ground
fault current in order to reach a safe voltage limit.
The author is with Meco Instruments
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