32 S&C Instruction Sheet 682-510
Dielectric Testing
Routine Switchgear Testing
For the convenience of users who normally perform elec-
trical tests on system compo nents such as switchgear,
appropriate with stand test values for Vista switchgear are
given in Table 1. These test values are signicantly greater
than the normal operating voltage of the switchgear and
are near the ashover voltage of the gear. They should be
applied only when the switchgear is com pletely de-energized
and disconnected from all power sources.
CAUTION
On Vista switchgear equipped with internal voltage
transformers (option suffix “-Y4”), do not apply test
voltage greater than normal system voltage to the
B phase if the switch way being tested is not open�
Refer to Table 1 and Figure 55 to determine the
location of the B phase
� Failure to follow this
precaution can result in injury or equipment
damage�
Dielectric testing on phases A and C can be performed
using standard industry practices in accordance with
the warnings and maximum test voltages indicated on
this page.
WARNING
When performing electrical withstand tests on Vista
switchgear, always observe the following precautions�
Failure to observe these precautions can result in
a flashover, injury, and equipment damage�
1�
Completely de-energize the switchgear and
disconnect it from all power sources�
2�
Terminate bushings with an insulated cap or
other appropri ate cable termination capable of
withstanding the test volt age�
3�
Verify that the insulating-gas pressure gauge is
in the Green zone�
Table 1� Maximum Insulation Test Voltages
Vista Switchgear Rating, kV Withstand Test Voltage, kV
50 Hertz 60 Hertz Impulse (BIL) Power Frequency
① Dc②③
12 15�5 95 27 42
24 27 125 40 62
36 38 150 50 82
① The listed power-frequency withstand test voltages are approxi-
mately 80% of the design values for new equipment�
② The listed dc withstand test voltages are approximately 80% of the
design values for new equipment�
③ Dc withstand test voltages are given for reference only for those
users performing dc withstand tests� The presence of these values
does not imply a dc withstand rating or performance requirements for
the switch gear� A dc withstand design test is specified for new equip-
ment because the switchgear may be subjected to dc test voltage when
connected to the cable� The dc withstand test values listed in the table
are approximately equal to the ac peak test voltage�
X X X X
X Do not apply test voltage to phase B unless
the switch is in the Open position�
Figure 55� Location of B phase indicated by an X�
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