The article deals with the necessary information regarding the types of faults and the causes of faults occur in underground cables. It also deals with the detection, localization and rectification of the faults.

CABLE FAULTS – DETECTION & LOCALIZATION
On analysis it has been found that about 70% of the external faults are noted as under cable faults so the efficiency of the maintenance of external plants largely depends on the proper planning, execution, constructional practices and maintenance of cable network ie the primary, secondary and distribution cables, cabinets, pillars, DPs etc. Moreover one cable fault usually effects a large number of circuits even upto 3600 circuits. So proper care and vigilance on the cable network is of utmost importance.

THE GENERAL TYPES OF CABLE FAULTS: –

(A) Earth fault When the insulation between the earth and the conductor in the cable becomes very low.

(b) Low insulation fault . :: When the insulation between conductors in the cable or between the pairs or between pair and earth falls below a prescribed limit (normally 0.5 meg ohm) This may be due to entry of moisture or due to failure of wire insulation.

(c) Disconnection Fault :: When the Conductor is cut then the fault is called break fault or is called High Resistance fault when High Resistance is introduced in the circuit.

(d) Short Circuit Fault :: When the resistance between the wires or between the conductors becomes very low even without any loop in the circuit on the pairs. This is also called contact fault.
pressure in the cable signifies the sheath fault in the cable and hence the whole cable drum should be sent back to the manufacturer. Proper laying can prevent a large number of the aforesaid reasons. Joint is the weakest portion in the length of the cables. So proper and utmost care should be taken at the time of jointing by using standard type and quantity of jointing material and employing efficient workmen.

Any how cable faults cannot be totally avoided and any of the above faults or a number of faults together may crop up due to any reason. The effect of the fault is either disconnection of communication or impairment or transmitted signals