Download REL 512 CT Circuit Current Rating

1
PAL 043002
Rev 0
April 30, 2002
Product Advisory Letter - REL 512 CT Circuit Current Rating
Dear Customer:
The Substation Automation and Protection Division of ABB Inc. is issuing this Product Advisory
Letter to inform you of a potential problem with the REL 512 Line Protection Terminal unit.
This notification affects all REL 512 relays catalog prefix R512 or 210 with serial numbers
greater than R5120055 and shipped after March 1st, 2000.
A failure of the analog input transformer surge protection board was reported by one of our
customers. It occurred while testing with high currents. The nature of the failure is that a trace
on the PC board, which carries the full test current, burned open. If this occurs in application the
CT circuit will open and possibly produce a potentially hazardous high voltage condition at the
failed CT terminals. After evaluation we found that the CT circuit current rating did not meet
our published rating above 65 amps.
The occurrence of this failure mode is extremely unlikely in application unless the relay
currents exceed 100 A during the fault, and there is abnormal fault clearing that allows this high
current to flow in the relay for more than 60 cycles. Normally, faults of this magnitude are
cleared in 4 to 5 cycles minimizing, if not avoiding, any thermal degradation.
Failure, if it occurs, will most likely occur during testing with sustained or repetitive (pulse or
ramp testing) high currents for long test times. This generally occurs when testing the impedance
boundary characteristics for low impedance settings well off the maximum torque angle.
To date, we have had only one failure, which occurred during a bench test. Units now being
shipped are provided with new surge protection boards that exceed our engineering specification.
Production fix
The analog input transformer surge protection board was redesigned to withstand a short time
rated current of 450 amps for one second. The trace width was doubled and thickness tripled.
Also, additional conducting copper paths were added to the top and bottom surfaces of the PC
board. Verification testing at 75 A and 500 A was performed. Results show that the new
capability exceeds the published CT current rating. A test report is available upon request.
These tests verify that the PC board is more than adequately designed to handle its 450 amps for
one second rating.
Upgrade
It is recommended that you upgrade any relay that can see more than 100 A secondary in
application as soon as possible. If you have selected your CT’s to prevent saturation it is
unlikely that secondary current will exceed 100A. For secondary currents above 100 Amps, the
risk of failure in application prior to relay tripping is extremely small.
2
It is also recommended that at your earliest convenience you upgrade any relay that can have
more than 65 Amps but less than 100Amps secondary current in application or any unit you have
not yet installed. Failure in application for this range of current is unlikely. Failure during tests
at these levels is possible.
It is your option to upgrade relays that cannot have more than 65 Amps in application. Failure is
unlikely in application, or test if the I2t rating of the CT circuit is not exceeded.
It is recommended that you return affected product to the factory for replacement of the surge
protection PC board.
If it is more convenient, modification can be done on-site in the field. The PC board will not be
replaced. However, reconnection to the board is made to prevent the board traces from carrying
the CT current. The relay front panel and top cover must be removed so that appropriate access
to the internal current transformers and connections is achieved. This may require the relay to be
removed from the panel or rack and all external terminations removed. It is recommended that
an ABB relay technician perform the field modification. To schedule a field modification
upgrade, or to obtain a copy of our analysis and test information regarding this Product Advisory
Letter, please contact the SAPD Allentown Customer Support department at 800-634-6005, 610336-5227, or fax 610-395-1055
If you have any questions regarding this Product Advisory Letter, please contact the SAPD
Allentown Customer Service Group at 800-634-6005, 610-395-7333, or fax 610-395-1055.