User Manual

Description
2.3 Protection system
3WA Air Circuit Breakers
64 Equipment Manual, 05/2021, 92310000002-03
2.3.6 DAS+ maintenance mode
An arcing fault can be described as a gas discharge with plasma formation and temperatures
up to 50,000 K, in which the electric current flows through unintended dynamic paths. In
addition to the extreme temperatures, very high pressures are also generated.
Arcing events typically result from:
• Human error,
such as accidental contact with voltages above ground potential, tools or debris
inadvertently left behind after maintenance, or improper assembly
• Lack of adequate maintenance for the operating or ambient conditions
• Insulation failure due to aging, environmentally-related degradation, animals in the
system (e.g. snakes or rodents), or operation not in accordance with the product ratings
After ignition, the arc transforms its surroundings by ionizing the air and converting metallic
materials into conductive plasma and expands with explosive force under extreme heat. The
more material is vaporized, the stronger the arc.
DAS+ maintenance mode
Fast tripping of circuit breakers and extinction of the arc are extremely important in order to
protect employees working in the immediate vicinity of live parts. To this end, the DAS+
maintenance mode operates with its own set of protection parameters to reduce the trip
threshold, thus ensuring that the circuit breaker trips at a lower threshold than would be
necessary for normal operation and without delay times.
The DAS+ maintenance mode is an energy-reducing function with local status indication,
which is used to comply with the following norms/standards:
• National Electrical Code (NEC) Section 240.87 (B)(3) Arc-Flash energy reduction (energy-
reducing maintenance switching with local status indicator)
• NFPA 70E Standard for Electrical Safety in the Workplace
• DIN EN 50110-1 Operation of electrical installations/B.6 Arc hazard