ISA T2000, User Manual

Page: 28 / 110

DOC. MIE11110 Rev. 5 Page 28 of 110
. With more transformers, it is necessary to lift the transformers
and operator with a lifter.
Connection cables from the interposing module to the transformers
are 20 m long, and allow reach any distance while leaving
If instead the CT is located into a cabinet, disconnect the high
current cables from the screw driven clamps, and connect them to
the spring driven clamps, using
a clamp per cable , then clamp
both clamps onto the CT terminations: this is necessary because
at high currents the spring clamp contact resistance would be so
high to make it impossible to reach high currents, and also the
heating would cause a great temperature increase.
In both instances, before clamping,
clean the CT contact
surfaces : surface oxidation can impair the capability of generating
high currents, and/or cause an huge temperature increase .
Connections from the test set to the Interposing module
IM2000are:
. The variable AC voltage output (not isolated from the mains),
that performs the fine current adjustment;
. The TEST START command, coming from the auxiliary output;
. The test set mains supply.
. When the time delay is to be measured, also the TIMER START
contact.
The secondary current can be measured by opening the circuit,
and entering the test set high current measuring sockets, or by
means of the optional clip-on current transformer, and entering
the low current measuring sockets: to this purpose, the clip-on
transformer is foreseen, but it looses accuracy.
Secondary CT leads should be twisted to reduce stray flux
influence. Take care of current direction, else the polarity test will
give wrong result: the red socket (output or input) is the positive;
with the clip-on transformer, look at the arrow or at the red mark
(entering current).
The following is the connection schematic, for the case of one
transformer.