6CP100/50-10
4-4
INITIAL SET-UP--ELECTRICAL
CURRENT METER GUARD CIRCUIT
There are three terminals on the base of the high voltage transformer; white GRD (Guard), green GND
(Ground), and a red RTN (Return). There is a metal jumper that must always be connected between either the
GND and GRD terminals or the GND and RTN terminals.
Refer to Figure 4-1 on the next page:
Standard Mode
In this configuration the current meter measures all leakage current from the high voltage electrode.
Measured current includes specimen leakage and stray leakage.
Guarded Mode
In this configuration only the leakage current from the high voltage electrode through the test specimen
to the RTN terminal is measured by the current meter. Any stray leakage current to ground is guarded
out (bypasses the meter) and is not measured. Stray leakage current to ground can be from several
sources. The high voltage transformer has some capacitive leakage to ground. The high voltage
connection might have some leakage due to partial discharge (corona). The test specimen might have
some leakage current to ground and your application requires that this “stray” leakage not be
measured.
Electrical Setup
In either configuration, the high voltage transformer’s ground stud must always be connected to earth
ground. The GND terminal referred in the following two paragraphs is internally connected to the
ground stud.
For standard current measurement, connect the jumper between the GND and RTN terminals.
Connect the test specimen return (low voltage side) to the RTN terminal.
For guarded current measurement connect the jumper between the GND and GRD terminals.
Connect the test specimen return (low voltage side) to the RTN terminal. Do not connect the specimen
return to ground. The test specimen must be totally isolated from ground.
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