Working Principle of Blavier and Earth Overlap Tests

Working Principle of Blavier and Earth Overlap Tests Points : Working Principle of Blavier and Earth Overlap Tests Fig illustrate the working of these tests.

The total resistance of the cable, before the occurrence of the fault, is assumed to be known. Let this resistance be “R” Ω. Suppose also that “r” is the resistance of the fault to ground, and that “r₂” and “r₂” are the resistances of the lengths of cable, “far end” to faults, and “testing end” to fault, respectively.

In the Blavier test the resistance between line and ground is measured, first with the “far end” disconnected from earth and then with the “far end” earthed.

These measurements of resistances may be made with the help of low voltage supply, and either an ammeter and voltmeter or a bridge network. Let these two measured values of resistances by M and M₂.