High impedance fault (HIF) detection represents a real challenge to protection engineers in electric utilities because of the
complexity and variability of the phenomena involved. HIFs have
the characteristic of producing low current magnitudes compared
to nominal load currents, which makes difficult its detection by
conventional overcurrent relays in a reliable way [1,2]. Some additional features that influence HIF detection are weather conditions,
fault conditions, fault distance, short-circuit rate, conductor type,
etc. There exist many causes leading to HIFs in Electrical Distribution Systems (EDS). For example, a HIF may occur when an energized conductor makes contact with the soil surface without a
solid grounding, or when the conductor get in touch with a branch
tree or any other object representing a high impedance path to
ground. Under these circumstances, the relatively high voltages
close to human beings and the electric arc associated to HIFs represents a serious risk to public safety and a major concern on
industrial installations.
HIFs are closely related to the grounding method used in EDS. A
description of these methods can be found in [3]. In México, North
America and Latin American countries the common practice is to
use a solidly grounding system. This approach facilitates the
setting of conventional overcurrent relays for detecting low impedance faults. Typical fault levels at the distribution substations bus
are 5–6 kA, 1.5 kA at the end of the feeder and load currents in
the range 300–500 A. Since typically a HIF produce currents