power systems loss

TYPES OF IMPEDANCE FAULT IN DISTRIBUTION SYSTEM Low Impedance and High Impedance fault in the distribution system Low Impedance Faults Low impedance faults or bolted faults can be either very high in current magnitude (10,000 amperes or above) or fairly low, e.g., 300 amperes at the end of a long feeder. Faults able to be detected by normal protective devices are all low impedance faults. These faults are such that the calculated value of fault current assuming a "bolted fault” and the actual are very similar. Most detectable faults, per study data, do indeed show that fault impedance is close to 0 ohms. This implies that the phase conductor either contacts the neutral wire or that the arc to the neutral conductor has a very low impedance. An EPRI study performed by the author over 10 years ago indicated that the maximum fault impedance for a detectable fault was 2 ohms or less. Figure 2, shown below, indicates that 2 ohms of fault impedance influences the level of fault cur

FUSE APPLICATION GUIDE RULES Basic points to consider in installing fuses in electrical system network 1)  Cold load pickup -  after 15 minute outage,  200% for.5 seconds                                                                          140% for 5 seconds                                        after 4 hrs, all electric  300% for 5 minutes 2)  "Damage" curve - 75% of minimum melt 3)  Two expulsion fuses cannot be coordinated if the available fault current is great enough to indicate an interruption of less than .8 cycles. 4)  "T" - SLOW and "K" - FAST 5)  Current limiting fuses can be coordinated in the sub-cycle region. 6)  Capacitor protection: The fuse should be rated for 165% of the normal capacitor current.  The fuse should also clear within 300 seconds for the minimum short circuit current. If current exceeds the maximum case rupture point, a current limiting fuse must be used. Current limiting fuses should be used if a s

Authored by: Alicia Valero Masa, Jean-Claude Maun, Stefan Werben ABSTRACT High Impedance Fault (HIF) detection is increasingly a concern of distribution network protection engineers. Practical methods to deal with HIFs are in great demand in the USA, where HIFs are not detected by conventional protection devices. The lack of a globally accepted description of HIFs is a difficulty for HIF detection. In the effort to understand and explain HIFs, we have carried out a theoretical study, simulations, laboratory tests, and studied field recordings. To study the influence of factors affecting HIFs, we have developed an Alternative Transients Program (ATP) simulation model and designed laboratory tests. HIF field recordings provided by Iberdrola Distribución Eléctrica S.A.U. validate the findings. In this paper, we present a  HIF characterization to improve HIF detection. This accurate characterization of HIFs allows us to develop a pattern recognition method to detect HIFs.