Arc Resistance - Siemens Sivacon S8 Planning Information

9.2

Arc resistance

An internal arc is one of the most dangerous faults inside
switchboards with extremely serious consequences – in
particular because personal safety is affected. Internal arcs
may be caused by wrong rating, decreasing insulation,
pollution as well as handling mistakes. Their effects, caused
by high pressure and extremely high temperatures, can
have fatal consequences for the operator and the system
which may even extend to the building.
An arc-resistant assembly consists of arc-free and/or arc-re-
sistant zones. An arc-free zone is defined as part of a circuit
within the assembly where it is not possible to apply an
igniter wire without destroying the insulating material of
the conductors, in the insulated main busbar for SIVACON S8,
for example (Fig. 9/1). An arc-resistant zone is defined as
part of a circuit where an igniter wire can be applied and
which fulfils all applicable criteria for test assessment, such
as the main busbar compartment of the SIVACON S8 with
arc barriers (Fig. 9/2). If the assembly is supplied by a
transformer, an arc duration of 300 ms should be consid-
ered in order to enable disconnection by a high-voltage
protection device.
The test of low-voltage switchboards under arcing condi-
tions is a special test in accordance with IEC/TR 61641. For
SIVACON S8 low-voltage switchboards, personal safety was
verified by testing under arcing conditions.
Active and passive protective measures prevent internal
arcs and thus personal injury or limit their effects within
the switchboard:
• Insulation of live parts (e.g. busbars)
• Uniform user interfaces and displays with integrated
operating error protection
• Reliable switchboard dimensioning
• Arc-resistant hinge and lock systems
• Safe operating (moving) of withdrawable units or circuit-
breakers behind closed door
• Protective measures in air vents
• Arc barriers
• Arc detection systems combined with fast disconnection
on internal arcs
The effectivity of the measures described is proven by
countless, comprehensive arcing fault tests under "worst
case" conditions performed on a great variety of cubicle
types and functional units.
Fig. 9/1:
insulation)
Fig. 9/2:
SIVACON S8 Planning Principles – Conforming to standards and design-verified
Insulated main busbar in the SIVACON S8 (optional N
Arc barrier in SIVACON S8
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