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Microgrids consist of a combination of generation resources and load, forming an electrically sustainable entity. Although the feeder configuration, including location of circuit breakers or switches, and selection of protective devices can change from one microgrid to another, some characteristics like size of microgrid and behavior of sources feeding a fault remains similar. Due to the non-uniformity...
Modern numerical relays have substantially reduced false operation of overcurrent relays used for capacitor protection. However, faster and more reliable operation can be useful. This paper proposes a morphological filter for fast and clear distinction between fault currents and switching currents that can benefit all types of overcurrent relays used for protection of capacitor banks. The filter performance...
According to the real time feature of relay protection and the wave characteristics of fault phase current, a new fault diagnosis scheme is introduced in this paper. It is based on wavelet transform, particularly the multiresolution analysis technique. This work focuses on how to use the wavelet transform to locate fault abrupt points, so that detect whether fault had happened, meanwhile microprocessor...
Digital relays traditionally use phasor estimation techniques based on the digital Fourier transform (DFT) and its variants. In recent literature, it is claimed that discrete wavelet transform (DWT) based filter performs better than traditional filters for phasor estimation. However, these claims are not well supported by sufficiently detailed analysis. This paper presents a detailed analysis to verify...
In recent years protection of electrical systems has developed considerably with the advent of programmable electronic protection devices which provide the scope for much closer protection and monitoring of electrical equipment. However, is this sophisticated equipment being used correctly to provide the protection required and are our systems as well protected as they should be? The protection is...
Overcurrents on distribution systems include permanent faults, temporary faults and other lower magnitude surges, typically from switching events. The overcurrent environment of the distribution system requires quantification if improvements are to be made in power quality, protection and reliability. New and more complex overcurrent protection products require more exact knowledge of feeder conditions...
Correct operation of the protection system is of vital importance for the reliability and security of supply. Information of protection system faults is therefore important for different purposes such as quality of supply regulation and as input data to security and reliability analysis. This paper provides a comparative review of the Norwegian and Finnish fault statistics for line and transformer...
Protection and control systems play important roles in power system operation and for the reliability and security of supply. This paper presents main results from a study of incorrect operations of protection and control systems on the voltage levels 1 - 420 kV in Norway, comprising mainly false and missing operations. The statistics for the period 1999 - 2003 show that false or unwanted operation...
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