PHIZ is based on algorithms that use earth current signatures which are considered
non-stationary, temporally volatile and of various burst duration. All harmonic and
non-harmonic components within the available data window can play a vital role
in the high-impedance fault detection. A major challenge is to develop a data
model that acknowledges that high-impedance faults could take place at any time
within the observation window of the signal and could be delayed randomly and
attenuated substantially. The model is motivated by extensive research, actual
experimental observations in the laboratory, field testing and what traditionally
represents an accurate depiction of a non-stationary signal with a time-dependent
spectrum.
Figure 434: Validation of PHIZ on gravel Figure 435: Validation of PHIZ on
concrete
Figure 436: Validation of PHIZ on sand
Figure 437: Validation of PHIZ on grass
5.4.5
Application
PHIZ is used to detect a downed conductor dropping to a very resistive ground,
causing an earth fault which is very difficult to detect by a conventional protection
relay functionality. PHIZ is then targeted to be used with overhead lines. PHIZ is
limited to be used in 60 Hz electrical networks with efficiently grounded or isolated
neutral.
Electric power lines experience faults for many reasons. In most cases, electrical
faults manifest in mechanical damage, which must be repaired before returning the
line to service.
Protection related functions
1MRS757644 H
822
620 series
Technical Manual
