Checking Ct Circuits - ABB REG670 Commissioning Manual

Section 4
Starting up
4.8
54
blocked. The red LED on the IED flashes, and the green LED is lit while the IED is in
the configuration mode.
When the configuration is written and completed, the IED is automatically set into
normal mode. For further instructions please refer to the users manuals for PCM600.

Checking CT circuits

Check that the wiring is in strict accordance with the supplied
connection diagram.
The CTs must be connected in accordance with the circuit diagram provided with the
IED, both with regards to phases and polarity. The following tests shall be performed
on every primary CT connected to the IED:
• Primary injection test to verify the current ratio of the CT, the correct wiring up to
the protection IED and correct phase sequence connection (that is A, B, C.)
• Polarity check to prove that the predicted direction of secondary current flow is
correct for a given direction of primary current flow. This is an essential test for
the proper operation of the differential function and directional protection
functions.
• CT secondary loop resistance measurement to confirm that the current transformer
secondary loop DC resistance is within the specification for the connected
protection functions. When the measured loop resistance is near the calculated
value for maximum DC resistance, perform a complete burden test.
• CT excitation test in order to confirm that the current transformer is of the correct
accuracy rating and that there are no shorted turns in the current transformer
windings. Manufacturer's design curves must be available for the current
transformer to compare the actual results.
• Grounding check of the individual CT secondary circuits to verify that each three-
phase set of main CTs is properly connected to the station ground and only at one
electrical point.
• Insulation resistance check.
While the CT primary is energized, the secondary circuit shall never be
open circuited because extremely dangerous high voltages may arise.
Both the primary and the secondary sides must be disconnected from
the line and the IED when plotting the excitation characteristics.
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
1MRK 502 073-UUS A
M12182-2 v15
Commissioning manual