Paper Identification
Name Lauri Kumpulainen Session No 1Company Vamp LtdCountry
Finland Paper ID No 0660Email laurt.kurnoulatneneovamo.f
SELECTIVE ARC-FLASH PROTECTION
The fastest way to detect an arc-flash fault is to detect the
arc-flash light. To preventunnecessary tripping caused by external
light sources, the light information is oftenconfirmed by
instantaneous overcurrent information. This principle can be called
dual-sensing technology.
The arc-flash light is detected by optical sensors. In most
cases point type of sensors areapplied. Point sensors are easy to
install, and they give accurate location information ofthe fault.
In some cases, e.g. low voltage motor control centres, fibre optic
sensors are agood low-cost alternative.
The overcurrent information is received from the CT's of the
normal protection system,thus no extra CT's are requtred,
Dedicated arc-flash protection relays
When using dedicated arc-flash protection relays, the protection
system consists of opticalsensors and CT's connected to I/O units,
communication cables and the arc master unit.Using the location
information from the optical sensors, the system is able to
initiate thetrip of the appropriate circuit breakers within a few
milliseconds. Continuous self-supervision of all components is an
important feature of the system.
Arc-flash option in common numerical protection relays
A cost effective alternative is arc-flash protection integrated
into common numericalrelays. E.g. relays of the outgoing feeders
can be equipped with arc-flash option, providlnqselective
protection in cable compartment faults.
Stand-alone solutions and arc eliminators
Forspecial purposes, low-cost stand-alone devices can be
applied. E.g. many new windpower plants are equipped with simple
arc-flash protection.
If extremely short arcing time is required, arc eliminatorcan be
used. Arc eliminatorcreates a controlled bolted short circuit
within a few milliseconds from the initiation of thearc,
eliminating the arc and even most of the pressure wave.
KUMPULAINEN-Finland-Sessionl-Paper0660 1
