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Description
The MCTT-10 test set is a portable unit
for performing saturation and ratio tests on current transformers using
the voltage-comparison method. Model MCTT-10 provides a variable voltage
output and precision instrumentation for testing single and multi-ratio
CTs. All tests, saturation and ratio – 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.
Saturation and ratio tests are
critical to ensure proper electrical system reliability. Saturation tests
are performed on CT’s to make sure that when a fault occurs the proper
secondary current signals are delivered to the protective devices. If a CT
does not deliver proper secondary current signals to a protective device
because of core saturation, it is probable that the protection scheme will
not operate correctly. A CT ratio test is performed to ensure that the
secondary current signals are proportional and correct, in relation to the
primary current.
Applications
Saturation Test
MCTT-10 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 will be 1 volt. More specifically, if 120
volts were applied to the secondary of a
600/5 current transformer (120:1 ratio), 1 volt will be present on the
primary winding.
Benefits
- The MCTT-10 utilizes the voltage comparison
method. This provides the user with the ability to measure the CT ratio
without the heavy and large equipment needed to test a CT ratio using
the current method. Many of the devices using the current-comparison
method exceed 100 lbs (45 kg). The MCTT-10 is only 37 lbs (16.8 kg).
- A RUN/HOLD switch freezes readings on
instruments when switched to the HOLD position. This permits the user to
freeze all the MCTT-10 meters for simultaneous readings.
- A low range of 40 volts is provided for CTs
that saturate at low voltages. A low voltage output range permits the
MCTT-10 to test low saturation CT’s with the appropriate resolution.
- The unit provides a high range of 1000 volts.
This allows the MCTT-10 to test nearly all protection CT’s
with high saturation knee points.
- A zero-start interlock is incorporated in the
unit. This minimizes the possibility of energizing the CT test with a
sudden high voltage, while under test.
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