ABB RELION REX640 Technical Manual page 1181

1MRS759142 F
Power system signals are acquired, filtered and then processed by individual high-
impedance fault detection algorithm. The results of these individual algorithms are
further processed by a decision logic to provide the detection decision. The decision
logic can be modified depending on the application requirement.
Figure 671: Block diagram of PHIZ
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 672: Validation of PHIZ on gravel
REX640
Technical Manual
Protection related functions
Figure 673: Validation of PHIZ on
concrete
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