Arc Flash Protection System

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.

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