Correct Answer - Option 4 : cradle guard
Guarding:
A guarding is provided for the safety of life, installation, and communication circuits.
The guarding for 11 kV lines is provided at road crossings, canal crossings, railway crossing, crossing over lt lines, or communication lines.
Regarding guarding of line crossings or approaching each other IER 87 provides all-important guidelines, IER (Indian Electricity Rule) 88 provides that every guard wire shall be connected with the earth at each point at which electrical continuity is broken.
Every guard wire should have sufficient current-carrying capacity to ensure the circuit renders dead, without risk of fusing of the guard wire or wires till the contact of any line wire has been removed. There are various other rules relating to guarding where lines cross trolley wires as mentioned in sub-rule (5) of IER 88.
Different Guarding Schemes:
Cradle Guarding:
Cradle guarding is provided when the conductors are in horizontal or delta formation as in the case of 11 kV lines. The cradle guard is directly connected to an earth wire. If a line conductor breaks, it will fall on the guard, thereby blowing the fuse or tripping the coil of a circuit breaker.
Cage Guarding:
Cage guarding is provided on lt lines with vertical formation. The guard should be made of the same material as used for earth wire. In lt lines, the guard is connected with the neutral and insulated from the earth by means of a porcelain reel.
