New Technology for Preventing Residential Electrical Fires: Arc-Fault Circuit Interrupters (AFCIs)


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INTRODUCTION

Annually, over 40,000 fires are attributed to home electrical distribution systems.
These fires result in more than 300 deaths and over 1,400 injuries each year. Statistics
from 1992-1996 show level trends in each of these estimates with no indications of
decline. In 1996, $680 million in property loss was attributed to home electrical
distribution fires.


The Evolution of Circuit Protection Devices

Circuit protection devices have evolved in capability and function from the time
that fuses were introduced in the late 1800s, to the introduction of circuit breakers in the
1920s, to today with the introduction of arc-fault circuit interrupters (AFCIs).



ARCING

Technically, an arc is defined as “a continuous luminous discharge of electricity
across an insulating medium, usually accompanied by the partial volatilization of the
electrodes”.12 Some arcs are a normal consequence of device operation, such as opening a
light switch or commutation from a motor. These devices are designed to contain arcs
from combustible surroundings.


MITIGATING THE EFFECTS OF ARCING

Conventional circuit breakers are designed to protect the branch circuit wiring.
The thermal settings are selected to prevent overloading of the circuit, while the
instantaneous trip is intended for rapid removal of short circuits.



Arc-Fault Circuit Interrupters (AFCIs)
Presently, AFCIs are designed into conventional circuit breakers combining
traditional overload and short-circuit protection with arc fault protection. The AFCI
circuit breaker provides protection for branch circuit wiring and limited protection for
power cords and extension cords. Some designs combine GFCI (ground-fault circuit
interrupter) and AFCI protection (see section on GFCIs). Receptacle types are being
developed, but no receptacle-type AFCIs were available at the time this paper was written.