Arcing incidents do happen. When they do, the total protection of the REA Arc fault protection system will pay for itself instantly, many times over.
The REA Arc fault system is built for total reliability. Continuous self-supervision of the system and fiberoptic loops helps to ensure protection is never lost. Overcurrent monitoring means that light and simultaneously detected overcurrent is used to trigger a circuit breaker for complete security.
Selective and zone protection are easy to implement. Extension modules allow single feeders or bus couplers to be isolated, maintaining power supply even during an arcing incident. Also, if one feeder is isolated during maintenance, full arc fault protection remains available for the rest of the system.
But above all, ABB REA Arc fault protection provides a total, reliable shield against often devastating consequences of arc flash faults.
Application Example 1
Arc fault protection implemented using the arc fault protection relay REA101. The arc sensor loop of the relay passes through all the spaces to be protected. Tripping requires a light signal generated by an arc and an overcurrent signal caused by a fault current.
Current is measured three-phase as 5 A or 1 A secondary current. When an arc occurs, the Q2 circuit breaker is operated via the semiconductor output HSO1.
The semi-conductor output HSO2 is used as a circuit-breaker failure protection output.
Should, for some reason, the feeder circuit breaker Q2 be unable to break the fault current in 100 ms after the trip operation, then the circuit breaker Q1 on the transformer primary side is opened via output HSO2.
Application Example 2
This application is similar to that of example 1, with the exception that the terminal end of the arc sensor fibre has not been brought back to the arc fault protection relay. However, the loop arrangement, where both ends of the sensor fibre are connected to the relay, is preferred, because this radial arrangement does not allow monitoring of the sensor fibre.
Application Example 3
In this example the number of arc sensor loops has been increased to five by adding two REA103 extension modules, which have been linked to the chain connected to port A via connection cables.
Tripping is activated in the same way as in examples 1 and 2. Information about the loop that detected the arc is obtained via the alarm relay outputs Light1
of the REA103 extension modules.
Application Example 4
In this application, the CB compartments of outgoing feeders and cable terminations are protected by the sensors of REA 107. The busbar is protected by the sensor loop of REA 101. After tripping, the Light LED of REA 101 or REA 107 indicates where the fault has occurred.
Application Example 5
In this application, the CB compartments of outgoing feeders, cable terminations and bus bar compartment are protected by the lens sensors of REA 107. The incoming CB is protected by the lens sensor of REA 101. After tripping, the Light LED of REA 101 or REA 107 indicates where the fault has occurred.
Application Example 6
In this example, the two REA105 extension modules with trip outputs are connected to port A of the main module. Should an arc occur, e.g., in the area monitored by extension module S3, circuit breaker Q3 will be the only one to be opened. Thus selective tripping is obtained, and the healthy part of the system remains live.
If the circuit-breaker failure protection (CBFP) of the REA105 extension module is in use, and the opening of circuit breakers Q3 or Q4 does not eliminate the fault current during the time delay (150 ms), the main module REA101 will open the circuit breaker Q2.
Correspondingly, if the circuit-breaker failure protection of the main module REA 101 is also in use, and the fault current does not disappear during the time delay following the opening of circuit breaker Q2, the main module will open the circuit breaker Q1.
When the main module REA101 performs tripping, it simultaneously delivers a trip command to the REA105 extension modules connected to it.
Application Example 7
Regarding operation, this application is similar to the application in the example 6. The only difference between these applications is the devices used.
Application Example 8
Substation with two power transformers, equipped with a bus coupler. Since the fault current can arrive from two supply directions, two REA 101 main modules, one for each direction, are required. The arc sensor loops of the main modules have been arranged so that the bus coupler Q5 separates the areas to be protected. When an arc occurs, the concerned main module trips its own infeeder circuit breaker and the bus coupler, the healthy part of the switchgear remaining connected.
The main modules send on/off overcurrent information to each other over the signal transfer fibre connection.
In this case, it is enough for the protection relay to operate if one of the units detects overcurrent, even in a situation where one transformer is out of service and the other transformer feeds the whole switchgear over the bus coupler. The REA 105 extension modules perform selective tripping in situations where the arc fault is located behind the concerned circuit breakers.
Application Example 9
Functionally, this application corresponds to that described in the example 8. The difference is that the overcurrent signals between the main modules are transmitted via the connection cable of the extension modules. An REA 105 extension module (not REA 103) has to be used in the connection point between the coverage areas of the main modules. This REA 105 module can normally be used as a part of the system that ends in a main module in the direction of the terminal IN1.
Application Example 10
Substation with three power transformers. Each infeeder has its own main module measuring fault current. Overcurrent data is transmitted to each extension module over the connection cable of the modules. Once the main module M1 or the extension module S1 detects an arc, the circuit breakers Q2 and Q3 are opened.
When the main module M2 or the extension module S3 detects a fault, the circuit breakers Q3, Q5 and Q6 are opened. Correspondingly, when the M3 or the S2 module detects an arc, the circuit breakers Q6 and Q8 will be opened. This arrangement allows just the faulty part of the switchgear to be disconnected.
The trip signal of the circuit-breaker failure protection of the three main modules is linked to the transformer primary circuit breakers (Q1, Q4 and Q7), with a delay of 150 ms.
Application Example 11
REA 101 is used to protect the switchgear against an arc caused by short-circuit or earth-fault current.
The arc sensor loop of the relay passes through all the spaces that are to be protected. Tripping requires a light signal generated by an arc, and a current signal generated by a short-circuit or earth-fault current.
- Short-circuit current is measured by the inputs L1 and L3 (5 A or 1 A). The current threshold of the inputs can be set to 0.5...6 In.
- Earth-fault current is measured by the input L2 (5 A or 1 A). The current threshold of the input can be set to 0.05...0.6 In.
When an arc occurs, the Q2 circuit breaker is operated via the semiconductor output HSO1.
The semi-conductor output HSO2 is used as a circuit-breaker failure protection output. If the feeder circuit breaker Q2 for some reason is unable to break the fault current within 100 ms after the trip operation, the circuit breaker Q1 on the transformer primary side is opened via output HSO2.