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5.3 Measurement of Prospective Short Circuit Current
− (Models 4118A and 4120A)
(1) Set the instrument to the 20kA range.
(2) Connect the test lead to the instrument.
(3) Attach the plug to the socket to be tested.
(4) Check that the LED's are lit in the sequence indicated in section 5.1. If
not, disconnect from the mains and check the wiring at the socket.
(5) Press the "Press to Test" button. The prospective short circuit current
(PSC) will be directly displayed on the LCD with the appropriate units.
This will remain for 3s and then revert to AC voltage display.
An audible beep will sound on completion of the test. For best results
always test on the lowest possible range.
For example a PSC measured on the 2000A range may read 60A
whilst on the 200A range it may read 56.0A. To hold the reading keep
the button held down or turn clockwise to lock for Auto Test.
Note:
● For loop impedance greater than 210Ω on PSC 200A range and 25
Ω on 2000A, 20kA ranges, the fault voltage may become high and
dangerous due to the D-LOK current, therefore, the unit is designed
to lock out PSC ranges showing "Uf-Hi" symbol.
Normally PSC tests are conducted at point of origin, e.g. distribution boards,
between phase and neutral.
When conducting PSC tests at socket outlets, a test will be conducted
between phase and earth due to the fixed wiring of the moulded mains plug.
WARNING
● This instrument is intended only for use in single phase operation
at 230V +10% -15% AC phase to earth or for use in OLD-TT
system phase to neutral.
6. DETAILED EXPLANATION
6.1 Measurement of Fault Loop Impedance and Prospective Fault Current
If the electrical installations are protected by over-current protection
devices or by fuses, the Fault loop impedance should be measured.
