Location of Cable Faults

Location of Cable Faults Points : Location of Cable Faults, Types of Faults, Ground Fault, Short Circuit Fault, Open Circuit Fault, Methods used for Locating Faults, Location of Ground and Short Circuit Faults Types of Faults The common faults which are likely to occur in lower distribution voltages are as under: 1. Ground Fault The insulation of cable may breakdown causing a flow of current from the core of the cable to the lead sheath or to the earth. This is called “Ground Fault”. 2. Short Circuit Fault If the insulation between two conductors is faulty, a current flows between them. This called a “Short Circuit Fault”. 3. Open Circuit Fault An open circuit fault occurs when a conductor gets broken or when a joint pulls out. Methods used for Locating Faults The methods used for locating ground and short circuit faults differ from those used for locating open circuit faults. Location of Ground and Short Circuit Faults In case of multi-core cables, it is advisable first If all, to measure insulation resistance of each core to earth and also between cores. This enables us to sort out the core that is earthed in case of ground fault; and to sort out the cores that are shorted in case of a short circuit fault. Loop tests are use for location of ground and short circuit faults. These tests can only be used if a sound cable runs along with the faulty cable or cables. The loop tests work on the principle of a “Wheatstone bridge”. The advantage of these tests is that their set up is such that the resistance of fault is connected in the battery circuit and therefore does not affect the result. However if the fault resistance is high, the sensitivity is adversely affected. In this section we will explain the “Murray Loop” test.