Purpose of earthing . Service System Eartha. Switching equipment.B. Transmission equipmentC. Measuring equipmentD. AC power supplyE. Corrosion mitigation.Protective system earth a.Protection against high voltage b.Protection against high current.. Requirement of service system earth. It sh
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1. Direct connection with earth for lightning protective apparatus To provide an earth to stabilize battery potential to the line and equipment earth. Single wire switching to reduce fuses .Positive bus bars are need not have an insulate.
2. Purpose of earthing Service System Earth
a. Switching equipment.
B. Transmission equipment
C. Measuring equipment
D. AC power supply
E. Corrosion mitigation.
Protective system earth
a.Protection against high voltage
b.Protection against high current.
3. Requirement of service system earth It should have low resistance to DC
It should carry high current with out heating and burning on it
It should remain same resistance in all seasons
It enable sufficient current flow to earth
4. Type of earth Individual earth
5. Design Low value of surge impedance
Close to the power plant
No Sharp bend and coil etc
Service earth carries the current to the earth
( it discharge the current to the earth)
6. DC 1 amp flows on a steel wire consumes
10 kg of steel per annum
25ma 20 year consumes 20kg of steel
7. Types Spike earth electrode System
Lead stripe electrode system
Earth plate electrode system
8. SPIKE earth 275,375 dia mm
9. Resistance of a single pipe log 4L
R= r --- -- -1
r= Soil resistively
L= length of the pipe in cm
a= radius of the pipe in cm
10. Earth plate electrode system