Atec Megger-CTER91 - Manual

CTER-91
Current Transformer Excitation,
Ratio and Polarity Test Set
■
Can test bushing CTs mounted inside
transformer or switchgear
■
Saturation, ratio and polarity tests
performed without changing test lead
connections
■
Overload and short-circuit protection
CTER-91
Current Transformer Excitation, Ratio and Polarity Test Set
DESCRIPTION
The CTER-91 test set is a lightweight, portable unit for
performing excitation, ratio and polarity tests on current
transformers using the voltage-comparison method.
Utilizing the latest technology, Model CTER-91 provides a
variable voltage output and precision instrumentation for
testing single and multiratio CTs. All three tests –
excitation, ratio and polarity – can be performed without
changing any leads.
Current transformers can be tested in their equipment
configuration, such as being mounted in transformers, oil
circuit breakers or switchgear.
It is necessary for the equipment to be totally isolated
from the electrical system prior to testing.
APPLICATIONS
Saturation Test
Model CTER-91 provides a variable voltage output and
digital instrumentation for measuring the excitation voltage
and excitation current that results as the voltage applied to
the CT under test is increased.
As the CT under test begins to saturate, a large increase in
current will be detected for a small increase in voltage.
Ratio Test
The ratio test is performed by comparing a voltage applied
to the secondary winding to the resulting voltage
produced on the primary winding.
For example, if 1 volt per turn is applied to the secondary
winding, the voltage present on the primary winding
would be 1 volt.
More specifically, if 120 volts were applied to the
secondary of a 600/5 current transformer (120:1 ratio), 1
volt would be present on the primary winding.
Polarity Test
Polarity of the current transformer under test is determined
by special circuitry that divides the voltage applied to the
secondary winding by either 10 or 100, depending on
switch position, then adds the result to the primary
voltage.
An increase in magnitude indicates correct polarity, and a
decrease shows incorrect polarity.
FEATURES AND BENEFITS
■ Voltmeter can be used to measure external voltages up
to 600 volts ac.
■ A RUN/HOLD switch freezes readings on instruments
when switched to the HOLD position.
■ A low range of 40 volts is provided for CTs that saturate
at low voltages.
■ The unit provides a high range of 1000 volts.
■ A zero-start interlock is incorporated. This minimizes the
possibility of energizing the CT under test with a sudden
high voltage.