5.4 DC Fault Location with MURRAY Method
The Murray-method applicable when the two wires of the pair have the
same gauge (
∅), the same length, are made of the same material and
only one of them is leaky. To provide the specified accuracy, the good
wire’s insulation resistance between wire and ground must be at least
1000 times greater then the faulty wire’s insulation resistance between
wire and ground.
The insulation resistance of the healthy wire must be higher than 10 MΩ
even if the fault resistance of the faulty wire is smaller than 10 kΩ.
The measurement can be performed if the healthy and faulty wires are
taken from different pairs.
That method can be applied when both wires of the faulty pair are wet but
another healthy pair is available. The two pairs must be in the same
cable.
Test Procedure
Select the MURRAY mode and press ENTER and then the measuring
arrangement appears
The far ending of the tested pair should be joined manually or by means
of the remote controllable loop-closing device KLC 8.
The faulty wire should be connected to socket A.
Two measuring modes are provided: Sensitive or Protected mode.
It is recommended to start the measurement with sensitive mode. When
the interference voltages overload the indicator a warning appears
informing the user that the result can be inaccurate. In that case the
measurement should be repeated in protected mode.
• Select the proper mode with the MODE (F3) key
• Start the measurement with the START/STOP key
Having the measurement completed the following results appear:
To Next Page
