(i) Pipe earthing is done mostly to earth the machine of high power as the earthing has wire earth contact, it provides more safety by earthing more leakage current.
(ii) The contact surface area of GI pipe with soil is more in comparison to the plate because of its circular section and hence can take up heavy leakage current for the same electrode size.
(iii) The earth wire connection with the GI pipe being above the ground level can be checked for carrying out continuity tests as and when desired while plate-earthing it is difficult. It is an advantage over plate-earthing.
(iv) Iron is the cheapest material and remains serviceable even if put in the salty mass of earth.
(v) Pipe earthing and plate earthing is considered to be the best as they have a reasonably low value of earth resistance.
(vi) When compared to the plate earth system, the pipe earth system can carry larger leakage currents as a much larger surface area is in contact with the soil for a given electrode size.
(vii) The system also enables easy maintenance as the earth wire connection is housed at the ground level.
12. While installing pipe earthing a rock is encountered then the rod shall be driven at an angle of
90 degree
45 degree
30 degree
15 degree
Answer.2. 45 degree
Explanation:-
Where rock is encountered, the rod shall be driven at a 45-degree angle from vertical or shall be buried in a trench not less than 30 in. (762 mm) deep.
13. Inside the earth pit, the earthing electrode should be placed at ______ position
Vertical
Horizontal
Inclined at an angle of 60°
Any of the above
Answer.1. Verticle
Explanation:-
The earthing electrode should always be placed in a vertical position inside the earth or pit so that it may be in contact with all the different earth layers.
14. Which of the following is the cheapest method of earthing?
Pipe Earthing
Plate Earthing
Split Earthing
Rod Earthing
Answer.4. Rod Earthing
Explanation:-
Rod earthing: It is the cheapest method of earthing and is employed in sandy areas. In this method, a copper rod is hammered directly into the ground, and no excavation work is required. The earthing lead is joined to this rod with the help of nuts and bolts.
15. The earthing electrodes should be placed within what distance in meters from the building whose installation system is being earthed.
4
2.5
1.5
0.5
Answer.3.1.5
Explanation:-
An earthing electrode should not be situated (installed) close to the building whose installation system is being earthed at least more than 1.5m away. This is to ensure that the conductivity and Electric field created due to one electrode do not interact with the other electrode. Also, the fault current from one electrode does not jump into the second electrode.
16. The earth wire and earth electrode is made up of
Different material
Same Material
Low and high resistance material
Any of the above
Answer.2. Same Material
Explanation:-
The earthing wires are essentially made from the best quality copper or GI that can be used in various electrical, electronic, and automobile instruments.
Copper can be used as earthing lead but, copper strip is also used for high installation and it can handle the high fault current because of a wider area than the copper wire. A hard-drawn bare copper wire is also used as an earthing lead. In this method, all earth conductors are connected to a common (one or more) connecting points, and then, earthing lead is used to connect the earth electrode (earth plat) to the connecting point.
Earth wire and earth electrodes are made up of the same low resistance material because if the earth wire and earth electrode are of different materials then the resistivity will be different and we will not get proper grounding.
17. The size of the earth wire is determined by
The atmospheric conditions
The voltage of the service wire
The ampere capacity of the service wires
None of the above
Answer.3. The ampere capacity of the service wire
Explanation:-
The minimum allowable size of Earthing conductors is determined principally by mechanical considerations, for they are more or less liable to mechanical injury and must therefore be strong enough to resist any strain to which they are likely to be subjected.
The general practice in electrical construction has been to place the minimum size at No. 8 copper, for service or system grounding.
For grounded secondary circuits, the hazard in case of loss of ground connection is less, and the size of the grounding wire is determined more by the amount of current it may be required to carry than by mechanical considerations. current, in turn, is determined by the rated capacity of the smallest fuse in the circuit supplying the equipment.
18. What is the diameter of the GI pipe through which the earth wire needs to be taken out?
13 mm diameter
15 mm diameter
19 mm diameter
6 mm diameter
Answer.1. 13 mm diameter
Explanation:-
The earth wire should be taken through a G.I pipe of 13 mm dia. for at least 32 cm length above and below ground surface to the earth, the electrode to safeguard against mechanical wear and tear.
19. The size of the earth conductor as a general rule should not be less than _____ of the cross-section of the line conductor.
Twice
Thrice
Half
Same
Answer.3. Half
Explanation
The size of the earth wire depends upon the application. Conductor size depends upon the factors like conductor material, maximum allowable temperature, fault current, duration of fault current, etc.
The cross-sectional area of main equipotential bonding conductors shall be at least half the cross-sectional area of the main earthing conductor, the minimum size allowed being 6 mm, copper.
The cross-sectional area of the earthing conductor need not exceed 25 mm if made from copper. A material other than copper can be used, providing it has the same conductance as the one made from copper.
20. ______ earthing is the best form of earthing and is very cheap in cost?
Pipe
Strip
Plate
Wire
Answer.1. Pipe
Explanation:-
Pipe earthing is the best form of earthing and it is cheap also in this system of earthing a GI pipe of 38mm dia and 2 meters length is embedded vertically in the ground to work as an earth electrode.
