ABB RED615 Technical Manual page 375

1YHT530004D05 D
615 series
Technical Manual
essential test for the proper operation of the directional function, protection or
measurement in the IED.
• CT secondary loop resistance measurement to confirm that the current
transformer secondary loop DC resistance is within specification and that there
are no high resistance joints in the CT winding or wiring.
• CT excitation test to ensure that the correct core in the CT is connected to the
IED. Normally only a few points along the excitation curve are checked to
ensure that there are no wiring errors in the system, for example, due to a
mistake in connecting the CT's measurement core to the IED.
• CT excitation test to ensure that the CT is of the correct accuracy rating and
that there are no short circuited turns in the CT windings. Manufacturer's
design curves should be available for the CT to compare the actual results.
• Earthing check of the individual CT secondary circuits to verify that each three-
phase set of main CTs is properly connected to the station earth and only at
one electrical point.
• Insulation resistance check.
• Phase identification of CT shall be made.
Both the primary and the secondary sides must be disconnected
from the line and the IED when plotting the excitation characteristics.
If the CT secondary circuit is opened or its earth connection is
missing or removed without the CT primary being de-energized
first, dangerous voltages may be produced. This can be lethal and
cause damage to the insulation. The re-energizing of the CT
primary should be prohibited as long as the CT secondary is open
or unearthed."
Checking of the power supply
Check that the auxiliary supply voltage remains within the permissible input
voltage range under all operating conditions. Check that the polarity is correct
before powering the IED.
Checking binary I/O circuits
Always check the binary input circuits from the equipment to the IED interface to
make sure that all signals are connected correctly. If there is no need to test a
particular input, the corresponding wiring can be disconnected from the terminal of
the IED during testing. Check all the connected signals so that both input voltage
level and polarity are in accordance with the IED specifications. However,
attention must be paid to the electrical safety instructions.
Always check the binary output circuits from the IED to the equipment interface to
make sure that all signals are connected correctly. If a particular output needs to be
tested, the corresponding wiring can be disconnected from the terminal of the IED
during testing. Check all the connected signals so that both load and polarity are in
Section 4
Protection functions
369