Power System Protection, fault location, distributed generation

This paper presents the application of the multiframe digital interconnection protection for cogeneration systems. The multiframe digital interconnection protection is constructed from two frequency main frames; one frame to detect islanding events and the other frame to detect faults on either side of the pointof-common-coupling (PCC). Islanding events are detected based on the wavelet packet transform high-frequency subband, which is extracted from the d-q-axis components of the instantaneous 3φ apparent powers determined at PCC. The detection of faults, on either side of PCC, is achieved by extracting the magnitudes and phases of the high-frequency contents present in PCC currents. The high-frequency contents present in PCC currents are extracted by a phaselet filter bank that is composed of six digital high-pass filters, which are designed to implement six phaselet subframes. The multiframe digital interconnection protection is experimentally tested on a 3.6 kVA cogeneration system for islanding events, different faults on both sides of PCC, and nontransient conditions. Test results demonstrate the ability of the proposed interconnection protection to initiate accurate, fast, and reliable responses to various types of transient disturbances.

This paper presents a coordinated anti-islanding protection for collector systems with multiple distributed generation units (DGUs). The presented anti-islanding protection is established based on processing the d-q-axis components of the instantaneous three phase apparent powers (s d and sq) determined at the point-of-common-coupling using the wavelet packet transform (WPT). Processing s d and sq by using WPT allows the extraction of lowand high-frequency sub-band contents. The contents of the high-frequency sub-band are used to detect and distinguish islanding events, and contents of the lowand high-frequency subbands are employed to define a coordination index, which is used to identify the islanded DGU(s). The presented anti-islanding protection is implemented for off-line testing using data obtained from a laboratory collector with four different DGUs. Off-line test results demonstrate accurate, fast, and reliable responses to islanding and nonislanding event(s), and accurate identification of islanded DGUs along with negligible sensitivity to levels of power delivery to the collector system.

This paper describes an adaptive distance relaying scheme which can eliminate the effect of fault resistance on distance relay zone reach. Distance relay is commonly used as main protection to protect transmission line from any type of fault. For a stand-alone distance relay, fault resistance can make Mho type distance relay to be under reached and thus the fault will be isolated at a longer time. In this scheme, the relay detects the fault location using a two-terminal algorithm. By knowing fault location, fault voltage at the fault point can be calculated by using equivalent sequence network connection as seen from local terminal. Then, fault resistance is calculated by using simple equation considering contribution from remote terminal current. Finally, the compensation of fault resistance is done onto
calculated apparent resistance as seen at relaying point. The
modeling and simulation was carried out using Matlab/Simulink software. Several cases were carried out and the results show the validity of the scheme.

Faults can occurred at the transmission line due to lightning strike, broken conductor, cross arm or tower falls, danger tree, crane or animal encroachment, polluted insulator etc. Each type of fault will represents a fault resistance value. Fault resistance will affects the accuracy of protection relays in fault location and fault zone detection. Phase to phase fault is one type of unsymmetrical fault at the transmission line. This paper represents the accurate way to calculate the actual phase to phase fault resistance value by using data from both local and remote substations. From the finding, the actual fault resistance can be represented by fault resistance as seen from local substation in parallel with the fault resistance as seen from remote substation. To prove the finding, simulation has been carried out and the results show the validity of the proposed theory.