Varley Loop

Varley Loop

The Varley Loop is another piece of test equipment to accurately locate ground faults and short circuits in a multi-conductor cable such as a telephone or wiring cable.  From the diagram the Varley Loop is a Murray Loop with an added resistor, R   .

In the configuration A above, the ground fault does not affect the null since it is the only ground in the circuit.  The null simply measures the total roundtrip cable length resistance, 2R_A as:

When the same components are reconfigured to the B configuration shown on page 8, there is a new bridge equation.