•
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.
•
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.
Both primary and secondary sides must be disconnected from the
line and IED when plotting the excitation characteristics.
2.8
Checking VT circuits
Check that the wiring is in strict accordance with the supplied connection diagram.
Do not continue before any errors are corrected.
Test the circuitry.
•
Polarity check
•
VT circuit voltage measurement (primary injection test)
•
Earthing check
•
Phase relationship
•
Insulation resistance check
The polarity check verifies the integrity of circuits and the phase relationships. The
polarity should be measured as close to the IED as possible to ensure that most of
the wiring is also checked.
The primary injection test verifies the VT ratio and the wiring all the way through
from the primary system to the IED. Injection must be performed for each phase-to-
neutral circuit and each phase-to-phase pair. In each case voltages in all phases and
neutral are measured.
2.9
Checking the RTXP test switch
The RTXP test switch is designed to provide the means of safe testing of the IED.
This is achieved by the electromechanical design of the test switch and test plug
handle, when the test plug handle is inserted it first blocks the trip and alarm
Section 2
1MRS756801 A
Starting up
18
630 series
Commissioning Manual
