بحث بعنوان The Effect of the Harmonics, the Fault Location and the Fault Resistance on the Performance of the Impedance-Type Distance Relay

بحث بعنوان
The Effect of the Harmonics, the Fault Location and the Fault Resistance on the Performance of the Impedance-Type Distance Relay
A.S. Khraiwish, M. Alshamasin, R. Kassasbeh, Y. Al shiboul, Z. Al-Qudah and M. Al-Busoul
Faculty of Engineering Technology, Al-Balqa’a Applied University, Amman, Jordan
Abstract: One of today’s trends is continuously increasing the number and the power ratings of the
non-linear loads connected to the electric power systems. These non-linear loads, such as powerelectronic converters, are the main source of the harmonics that affect the performance of the
impedance-type distance relays. It was found that, in the presence of harmonics, undesired operation of
such type of distance protection will occur, as the distance relay can react improperly and sense faults
at zones other than the desired ones and the selectivity of the distance relays will be violated as
improper relays will react while those concerned will not. It has been also shown that the fault location
and the fault resistance were affecting the impedance seen by the distance relay. The data obtained
from the analysis of a three-phase-to-ground fault, in a sample four-bus practical system, was used to
study the behavior of the distance relay and to estimate the impedance seen by it. An algorithm, that
can be used to calculate the system quantities in the presence of a harmonic source, was suggested.
Key words: Power system protection, distance relay, impedance-type distance relay, impedance seen
by the distance relay, three-phase-to-ground fault, power transmission, non-linear loads.
CONCLUSION
An algorithm for computing the bus voltages and
the line currents, in the presence of a harmonic source,
was presented. This algorithm was used to calculate the
impedance seen by the impedance-type distance relay,
in case of three-phase-to-ground fault, and in the
presence of a harmonic source.Am. J. of Appl. Sci., 6 (4): 788-796, 2009 796
A practical four-bus power system was used as a
sample system for the study. Detailed analysis for the
impedance seen by the distance relay, for different fault
locations, was provided.
It has been found that in the presence of harmonics,
the distance relay will react improperly and sense faults
at zones other than the desired ones. This will violate
the selectivity of the distance protection, as improper
relays will react while those concerned will not, which
will cause disconnection of healthy lines. It has been,
also, shown that the fault location and the fault
resistance were affecting the impedance seen by the distance relay.

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