Tettex MIDAS 2881, Operating Instructions Manual

Page: 124 / 164

114 Applications Guide
The tap insulation (C2) of
bushings equipped with taps,
can be measured directly.
As illustrated in the figure
beside, the High Voltage and
the INPUT A cable must be
interchanged.
Using the GST gA+B mode will
bypass the main insulation (C1)
and measure the tap insulation
(C2).
Warning: Check the
manufacturer’s
recommendation for max. tap
test voltage
Spare Bushing Tap Insulation Test
14.1.2 Installed Bushings
Overall Test (Centre Conductor to Flange) .
If a bushing is mounted on an equipment, the overall measurement method would include all
conduction and insulation elements connected between the bushing center conductor and ground.
Therefore the overall method is not recommended for separate tests on bushings, unless the bushing
conductor can be completely isolated or the bushing has no tap.
Center Conductor to Tap, C1
Most high-voltage condenser-type bushings are equipped with either potential or power-factor test
taps. These permit separate tests on the main bushing insulation (commonly referred to as C1)
without the need to disconnect a bushing from the equipment or bus to which it is connected.