Overhead distribution systems in wartime

Overhead distribution conductors move as a result of short-circuit conditions. In some cases, this motion can lead to conductors swinging together closer to the source. The subsequent fault causes higher stresses on the substation transformer and causes a backup overcurrent protective device to operate, having a negative impact on reliability. This paper reports on an investigation involving conductor motion on Dominion Virginia Power's overhead distribution system. It builds upon prior work dealing with compact overhead transmission lines. The author extends the model to typical overhead distribution lines and provides guidance to the distribution engineer as to when conductor swinging might become a problem. The characteristics of the most vulnerable spans led to the development of time-current curves depicting regions where spans are likely to have problems from short-circuit forces. The resulting critical clearing time curves have been adopted by the author's company to minimize problems from swinging conductors.

It is necessary to detect a fault point in overhead distribution system for failure restoration. To search the fault point effectively and precisely, we apply TDR (Time Domain Reflectometry) measurement with utility-pole-distance resolution. In this method, we inject a pulse wave into distribution lines and measure the reflection. In this paper, the authors confirm propagation characteristics of overhead distribution system and compare the measurement of the reflected wave with the simulation result. Through the experiments, the authors confirm an influence of parasitic capacitances in overhead distribution facilities such as a transformer and a switchgear. When distribution facility is not connected with distribution line, the reflected wave from every utility pole and the end terminal are observed; the reflected waves from every utility pole are caused by parasitic capacitors between the distribution lines and cross arms. When distribution facility such as a transformer and a switchgear is connected with distribution line, the reflected waves caused by these facilities are observed. As a result, we confirmed that parasitic capacitances of distribution facilities affect the propagation characteristics of distribution failure pulse wave. In addition, the authors developed a simulation tool to evaluate the propagation characteristics of the pulse wave in the overhead distribution system based on the result utilizing the test distribution system, and confirmed that the simulation results corresponded to the measurement results.

This paper presents basic guidelines on design considerations for wind power plant substation and collector system based on redundancy, reliability, and economics. Design considerations, although similar to utility substation and underground or overhead distribution systems, often include aspects not normally considered for those systems. This paper will highlight design considerations unique to wind power plant design comparing economic and reliability benefits among available design options. Power loss analysis in a typical wind power plant is explained. Finally, an overall economic analysis to be considered when designing a new wind power plant is presented.

Downed distribution conductors in overhead distribution systems, may not be a concern for equipment, but greatly challenge the safety of persons, as well as the integrity of properties. Upstream overcurrent protective devices may not be able to detect the magnitudes of fault currents resulting from these high-impedance faults. Even though protective devices capable to detect such faults have been available on the market, not all the utilities have equipped their stations with these products, likely due to the costs. In this paper, the authors formalize the problem, and propose a possible cost-effective solution for the low-voltage over-head lines with neutral wire. Such solution includes a metal hook underneath the line conductors, supported by the pole, and connected to the neutral wire. This arrangement would cause a line-to-neutral short circuit, positively activating existing over-current devices, which can therefore disconnect the supply. Costs and possible safety issues for workers related to the installation of the device to existing overhead lines are herein also delineated.

This paper presents the development of a virtual real-time test platform for intelligend electronic devices (IEDs) with high impedance fault detection function. High impedance faults are very common events in overhead distribution systems, being difficult to detect due to it’s low current magnitude. Considering the difficulty of recording oscillographies of these faults, and the availability of real-time digital simulations, this paper proposes a test platform for protection devices. In order to accomplish this, a real-time simulation platform from Typhoon HIL Inc., equipped with a Typhoon HIL 604 is used. The elaboration and validation process of the high impedance fault model proposed by Gautam and Brahma (2013) is demonstrated, testing the parameters of three different surfaces. The results reflect what is expected for high impedance faults, with the tests occuring dynamically through the accesses of the low-level interface of the used IED.

This chapter has introduced the important concept of insulation coordination of high voltage systems. The reader should be aware that increasing environmental and aesthetic concerns regarding the utilisation of overhead electrical power transmission lines have resulted in critical evaluation of underground alternatives and, in particular, at opportunities to further reduce the cost ratio between overhead and underground distribution and transmission systems. A joint CIGRE Working Group has been established to evaluate the influence of transient over-voltages on AC cable insulation design. Briefly, if one considers the inherent costs associated with cable systems (cable and accessories) then, by reducing the required withstand capability with improved protection devices and network design philosophy, one could develop a more economic underground system.

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the Irish Branch, at Dublin, 18th November, 1948

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the Southern Centre, at Southampton, 2nd February, 1949

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the North-Western Centre, at Preston, 19th January, 1949

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the South-Western Sub-Centre and the Western Supply Group, at Taunton, 23rd March, 1949

The author's reply to the discussions on “The lightning protection of high-voltage overhead transmission and distribution systems”

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the Scottish Centre, at Edinburgh, 9th March, 1949

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the North-Eastern Centre, at Newcastle-on-Tyne, 13th December, 1948

Discussion on “The lightning protection of high-voltage overhead transmission and distribution systems” before the East Midland Centre, at Loughborough, 25th January, 1949

Large-scale rescue excavation beyond the guardianship area around the Roman fort on the Antonine Wall at Croy Hill (NGR: NS 7335 7652) was undertaken over four summers (1975–8), funded by a predecessor to Historic Environment Scotland. The aims of the excavation were to identify any potential civil settlement associated with the fort and to confirm the character and date of a pre-fort enclosure identified by Sir George Macdonald in the 1930s. The latter proved to be a camp associated with the building of the Antonine Wall, not an earlier Flavian fort as previously postulated. A civil settlement was shown to lie within the guardianship area on a plateau immediately to the west of the fort, though only one timber structure extended into the excavated area. However, a curvilinear trackway wound its way down the hill from the settlement towards a southern road that bypassed the fort. The trackway was defined by substantial ditches that contained a large quantity and wide variety of artefactual material washed down from the settlement, predominantly after its abandonment. The bypass road, which showed signs of at least two phases of construction, was traced for a distance of some 275m. The area on either side of it to the east of the fort was divided up by a system of fence lines and ditches into fields or compounds, one of which contained a pottery kiln, another a cremation burial. Field observation during the excavation led to the suggestion that a fortlet lay some 80m west of the fort. This was confirmed by limited excavation within the guardianship area. The construction of the fortlet was shown to have been contemporary with the Antonine Wall.