Fixed Arc Fault Protection System DEHNshort
Details
- Protection of persons and installations and function in accordance with DIN EN 61439-2, Suppl. 1 (IEC/TR 61641 ed. 3, 2014)
- Maximum availability of installations
- Modular system design
- System status is indicated at the front of the installation
Description
DEHNshort optimally protects persons and switchgear installations from the effects of an arc fault. To achieve this, particularly short response times are required in high-energy switchgear installations. Just a few milliseconds are decisive for the intensity and the effects of an arc fault. DEHNshort detects the arc fault the moment it starts to develop, evaluates the detected sensor signals and quenches the arc fault by generating a three-phase bolted short-circuit.
Functional principle:
Detection
The protection transformers situated upstream of the feeder circuit breakers detect the overcurrent resulting from the arc fault in all infeeds. Special light sensors detect the extremely bright light of the arc fault. Depending on the requirements of the relevant switchgear installation, light sensors are available as point sensors or fibre optic sensors.
Evaluation
Electronic detection devices link the sensor signals and activate the quenching devices of the relevant busbar as well as the shunt releases of all feeder circuit breakers in case of both detection parameters.
Quenching
As soon as the quenching devices are activated, a bolted short-circuit is generated in parallel to the arc fault within a short period of time. Due to this low-impedance bypass, the voltage drops and the arc fault is quenched immediately. Thyristors short-circuit the three phases of the busbar directly after the quenching devices have been activated. Subsequently, a spring-driven contact system carries the short-circuit current until the installation is disconnected by the feeder circuit breakers.
Isolation
To ensure that the switchgear installation is not loaded with the short-circuit current for longer than necessary – and to ensure additional safety – a disconnection command is transmitted to the relevant shunt release of all feeder circuit breakers via floating contacts. This means that the busbar section where the arc fault occurred is already isolated from the system.
Re-commissioning
The switchgear installation can be immediately re-commissioned after the fault has been rectified and the quenching devices have been replaced. The arc fault protection system significantly exceeds the requirements of test criteria 1-7 of IEC TR 61641 ed3 of 2014. DEHNshort is used wherever the protection of persons and availability of the power supply is vital.
Functional principle:
Detection
The protection transformers situated upstream of the feeder circuit breakers detect the overcurrent resulting from the arc fault in all infeeds. Special light sensors detect the extremely bright light of the arc fault. Depending on the requirements of the relevant switchgear installation, light sensors are available as point sensors or fibre optic sensors.
Evaluation
Electronic detection devices link the sensor signals and activate the quenching devices of the relevant busbar as well as the shunt releases of all feeder circuit breakers in case of both detection parameters.
Quenching
As soon as the quenching devices are activated, a bolted short-circuit is generated in parallel to the arc fault within a short period of time. Due to this low-impedance bypass, the voltage drops and the arc fault is quenched immediately. Thyristors short-circuit the three phases of the busbar directly after the quenching devices have been activated. Subsequently, a spring-driven contact system carries the short-circuit current until the installation is disconnected by the feeder circuit breakers.
Isolation
To ensure that the switchgear installation is not loaded with the short-circuit current for longer than necessary – and to ensure additional safety – a disconnection command is transmitted to the relevant shunt release of all feeder circuit breakers via floating contacts. This means that the busbar section where the arc fault occurred is already isolated from the system.
Re-commissioning
The switchgear installation can be immediately re-commissioned after the fault has been rectified and the quenching devices have been replaced. The arc fault protection system significantly exceeds the requirements of test criteria 1-7 of IEC TR 61641 ed3 of 2014. DEHNshort is used wherever the protection of persons and availability of the power supply is vital.
Figure 1
Built-in protection transformers
Figure 2
Built-in light sensors
Figure 3
Detection devices integrated in the door
Figure 4
Quenching device above the supply switch
Figure 5
Basic circuit diagram
