Question

Direct laying method of laying underground cables has the drawback of : A. High maintenance cost
B. Localisation of fault is difficult
C. Possibility of damage of cable sheath owing to undergoing chemical changes due to impurities present in soil
D. Risk of cable being damaged
E. Low maintenance cost Choose the correct answer from the options given below :

• A. A, B and D only
• B. B, D and E only
• C. A, B, C and D only
• D. A, B and C only

Hint:

Disadvantages of direct underground cable laying:
• difficult fault location,
• costly maintenance,
• possible mechanical damage,
• chemical corrosion of sheath.

Answer 1

The Correct Option is C

Concept: In the direct laying method, underground cables are laid directly in trenches below the ground. Although this method is economical initially, it has several disadvantages related to:
• maintenance,
• fault detection,
• mechanical protection,
• chemical deterioration.

Step 1: Analyzing statement A. Statement: \[ \text{High maintenance cost} \] This is a drawback. Because:
• cable faults are difficult to repair,
• excavation is required,
• maintenance work becomes costly. Hence statement A is correct.

Step 2: Analyzing statement B. Statement: \[ \text{Localization of fault is difficult} \] This is also correct. Since cable is buried underground:
• exact fault location is not easily visible,
• extensive testing may be required. Hence B is correct.

Step 3: Analyzing statement C. Statement: \[ \text{Possibility of chemical damage due to soil impurities} \] This is correct. Underground soil may contain:
• moisture,
• salts,
• acidic compounds,
• corrosive chemicals. These can damage cable sheath over time.

Step 4: Analyzing statement D. Statement: \[ \text{Risk of cable being damaged} \] This is also correct. Underground cables may be damaged due to:
• digging operations,
• road construction,
• mechanical stress. Hence D is correct.

Step 5: Analyzing statement E. Statement: \[ \text{Low maintenance cost} \] This is not a drawback. In fact, the actual drawback is: \[ \text{High maintenance cost} \] Therefore statement E is incorrect.

Step 6: Selecting the correct combination. Correct drawbacks are: \[ A,\;B,\;C,\;D \] Hence correct option is: \[ \boxed{(3)} \]