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Surge arresters were evaluated as a means of improving reliability by reduction in 13 kV distribution line flashovers; five feeders were extensively monitored for three years. Lightning-caused faults were detected with the US National Lightning Detection Network, magnetic-field and optical sensors attached to fault recorders, and lightning-activated camera systems. Three circuits had arresters added on all phases with spacings of 40 m (every pole), 200 m, and 400 m respectively. Two other control circuits had no additional arresters. There was no discernible difference in the lightning performance of the circuits outfitted with the different arrester spacings when line length and lightning flash exposure are considered. Evidence indicated that most of the faults were caused by direct strokes rather than induced voltage flashovers. The monitored circuits are in areas with relatively heavy tree coverage which should reduce the number of direct strokes but cause higher induced voltages. In a surprising result, the circuit with arresters installed on every pole had several lightning-caused faults.

The Niagara Mohawk Power Corporation (NMPC) Research and Development Department sponsored a major power quality study of two distribution feeders in the Buffalo, New York region. All levels of these systems, from the substation bus to the customer service entrance, were instrumented with monitoring equipment. A variety of measurements, encompassing both transient and steady state system behavior, were performed. The use of multiple monitoring locations allowed NMPC to assess the origins and scope of various disturbances. The study generated a database which can serve as a guide for assessing relative power quality of the NMPC system. The study also formulated suggestions on areas which the industry (both the power industry and consumer products industry) might address in the future on the effect of standard utility operation towards consumer appliances. >

The uncertainties involved in evaluating induced voltage lightning performance of distribution lines are reviewed, and two algorithms to facilitate computer simulation are outlined. These are a simplified surge impedance model of each wire section of the line, permitting the coupled electromagnetic fields to be replaced by simple algebraically computed forward-backward (FB) current pairs, easily processed by computer to handle current reflections and refractions from power transformers, arresters, taps and other discontinuities; and an algorithm for distribution line-induced voltage lightning performance calculations that integrates between a striking distance curve and a critical flashover-distance curve. >

A program, the distribution lightning program (DLP), for analyzing lightning flashovers is discussed. The goal is to improve protection of overhead distribution circuits from lightning. Various lightning protection schemes can be simulated. The program uses traveling wave calculations to analyze direct lightning strokes and induced voltages caused by nearby strokes. Shield wires and arresters, two line protection options that reduce momentary outages caused by lightning, are discussed. The analysis shows that enhanced insulation level, grounding, and conductor placement can improve flashover performance. Two examples are provided to show the flexibility of computer analysis in the design and selection of overhead distribution structures. DLP was written to analyze distribution designs, but the calculation techniques and some of the results can be applied to transmission lines as well. >

A method for obtaining transfer functions for power system stabilizer (PSS) design is presented. It results in an accurate reduced-order model of a generator connected to a large system. The method is based on Prony signal analysis and incorporates both local and interarea electromechanical oscillatory modes. Two PSS units are designed using the proposed method along with root-locus and sequential decentralized control techniques. The design procedure and results are illustrated using computer simulation of a 27 bus system with 16 generators. The test system was developed to exhibit interarea modes that are comparable to the western North American power system. This provides a new perspective on damping interarea oscillatory modes using PSS units. >

Three-phase reclosers with single-phase tripping are being more widely employed on utility distribution feeders. They have the advantages of increasing reliability for the customers on the feeders, because the majority of distribution feeder faults are single-phase. However, certain difficulties may occur when three-phase industrial and commercial loads, with three-phase transformers and motor loads are interrupted on one phase only. These include overheating of motors, ferroresonance of transformers, tripping of power electronic drives and backfeeding of distribution lines. This paper examines these effects, their severity and mitigation techniques.

Basic recommendations are provided for enhancing the reliability of new and existing capacitor controller installations by optimizing their resistance to surges. The sources and types of surges commonly experienced by capacitor controllers are discussed with consideration given to circuit parameters that can influence the magnitude of surges reaching the controller. Different controller surge protection configurations are examined including providing auxiliary secondary-side surge protection. The discussion culminates with some basic surge protection recommendations to enhance the lightning performance of capacitor controllers

This paper considers several approaches to use overcurrent protection to improve distribution reliability. Having more protective devices that are properly coordinated assures that the fewest customers possible are interrupted and makes fault-finding easier. Fusing is an inexpensive way to isolate faults, and this paper describes some often-overlooked fusing considerations. Applications of fuse blowing and fuse saving are also considered. Reclosing practices can be optimized to limit impacts on customers. In addition, single-phase protective devices can also limit customer outage time by reducing the number of customers affected