NDB Technologies CTT Series User Manual page 33

9.3 Testing CT's in Shunt Reactor
This section explains how to connect the CTTx5 and CTTx2 to test a current
transformer installed in a high voltage shunt reactor. When performing tests on
CT's located on power transformer bushings, we use magnetic short-circuiting of
power transformer winding impedances. Essentially canceling power transformer
winding impedances. For CT's on shunt reactor bushings, unfortunately there are
no opposite windings we can magnetically short circuit. Therefore an error in ratio
measurements is expected. The following steps explain an alternative test method
that does not require to physically disassemble the shunt reactor to install a cable
on the primary side of the CT to test.
9.3.1 Step 1 - General Tests
This section describes the first steps in testing a CT located in a shunt reactor. All
tests will be conducted, but ratio test results will be discarded and covered in the
next section.
1. Before connecting the CTT instrument to any other cable/equipment, make
sure the ground post is earthed properly using the provided ground cable.
Connect the CTT to a power source and then turn on the instrument.
2. Connect the H1 and H2 tests leads to the primary side of the CT under test.
Connect X tests leads to the secondary side of the CT under test.
3. In order to reduce nearby induction effects, the bushing on which is connected
the H2 clamp, must be shorted to ground.
4. At this step, either refer to section 8.1 for manual mode operation, or section
8.2 for automatic mode operation. CT ratio test results must be discarded.
All other tests are considered valid. Expect a minor error for the polarity test
result.
C T T S e r i e s
H1
H0 CT
Shunt Reactor
- U s e r M a n u a l
X1
X2
Control
Cabinet
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