Specifications

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Doc. no.
Model
Apparatus
Scale
Page No
1SDH000460R0002
L5439
12.7.2. Troubleshooting
The following table lists a series of typical service conditions, to help you understand and solve hypothetical faults or malfunctions.
N.B.:
1. Before consulting the following table, check for a few seconds for any optical signals provided by the LEDs.
2. FN indicates the normal operation of the PR121/P.
3. If the following suggestions fail to solve the problem, please contact the ABB SACE customer support service.
N° Situation Possible causes Suggestions
1 The trip test cannot be run 1. The busbar current is è > 0
2. The TC is not connected
3. PR030/B is not connected
1. FN
2. Check TC connection
(see par.12.4.2)
3. Connect the PR030/B unit
2 Trip times lower
than expected
1. Threshold too low
2. Curve too low
3. Incorrect neutral selection
1. Correct threshold
2. Correct curve
3. Correct neutral adjustment
3 Trip times higher
than expected
1. Threshold too high
2. Curve too high
3. Curve type "t=k/I
2"
4. Incorrect neutral selection
1. Correct threshold
2. Correct curve
3. Select curve type "t=k"
4. Correct neutral adjustment
4 Rapid trip, with I3=Off Iinst tripped FN short-circuit with high I
5 Earth fault current beyond
threshold
G function automatically inhibited but no
trip occurs
FN
6 Expected trip does not happen Function OFF FN enable protection function
7 LEDs irregularly turned on See par. 12.7.1
8 Unexpected trip See par. 12.7.1
9 L LED (orange) flashing FN
12.7.3. In the case of a fault
WARNING: If the PR121/P is suspected of being faulty, if there are signs of malfunctions or it has generated an
unexpected trip, we advise you to strictly follow the recommendations below:
1. Press the “i Test” button (within 48 hours of opening the CB) and make a note of which LED is on, also recording the type of
CB, the number of poles, any connected accessories, the In, and the serial number (see par. 12.5).
2. Prepare a brief description of the opening (what LEDs were displayed?, when did it happen?, how many times?, was it always
under the same conditions? what type of load? what current? is the event reproducible?).
3. Send/communicate all the information collected, together with the circuit diagram for the circuit-breaker, to your nearest ABB
Customer Support service.
The more the information given to the ABB Customer Support service is complete and accurate, the easier the technical analysis
on the problem encountered will be, enabling us to take all action to help the user without delay.
WARNING: Letting a switch run with a fault that has not been remedied may lead to an apparatus malfunction
or shutdown. Remove the apparatus immediately until it can be inspected or repaired if this situation may lead
to personal injury, damage or is otherwise critical.
12.8. Accessories
12.8.1. ABB SACE PR010/T test and configuration unit
Testing with the SACE PR010/T unit enables you to monitor the proper operation of thresholds and trip times of the protection
functions “L”, “S”, “I”, and “G”. The test unit is wired to the relay by a dedicated connector (see ref. 26 par. 12.5).
12.8.2. BT030 USB communication unit
Using the BT030 USB wireless communication unit, the PR121/P can be connected by radio to a normal PC, thus extending the
amount of information available to the user.
12.8.3. PR021/K and HMI030 units
The PR121/P can also be connected to the optional PR021/K external signalling unit (see par. 16), for the signalling by means of
no-potential power contacts of alarms and tripped protections, and to the HMI030 switchboard front unit to view various kinds of
information on the display.
12.8.4. PR030/B power supply unit
The PR030/B power supply unit is a separate unit for powering the relay, auto test, trip test and checking with CB open.
12.8.5. Flex interfaces
Flex interfaces are electronic modules with analogue and/or digital inputs and outputs that can be fitted to a DIN guide. They can
be connected to the supervision system or to the electronic release by internal bus or external bus (see par.16.6).