摘要:

A survey of the data available indicates that lightning flashes in all thunderstorms have similar characteristics as regards the times involved and the number of strokes in a flash, and it is shown that Norinder's divergent values are due to misinter-pretation of his data.It is suggested that while the charge neutralized in a lightning flash is probably about 50% greater than has hitherto been believed, the cloud potential is only a few per cent of the accepted value, and the energy of a flash about 250 kWh, as compared with Wilson's value of about 2800 kWh. A theory is advanced bearing on the mechanism of the leader and return strokes, which enables the shape of the lightning current wave to be calculated; in addition, a form is derived for the whole current wave in a multiple flash. A synthesis made from the results of many investigations leads to a picture of the mechanism of the return stroke and to the calculation of the various field changes produced, which agree well with those observed both in shape and in amplitude. New light is thrown on the analysis of the electrostatic field change caused by a stroke. The importance of space charge is emphasized in several connections, including the neutralization of cloud charge thereby, the frequency of “air discharges” and the peculiarity of flashes to the Empire State Building, the currents to which have been re-analysed.The effect of direct strokes to transmission lines is investigated, and it is shown that successive strokes which do not cause flashover are unlikely. The polarity of flashes to earth is shown to differ in tropical and temperate regions, and it is concluded that the polarity of strokes to phase wires cannot be deduced from that of strokes to towers. Suggestions are made as to further investigations.

DOI:10.1049/ji-2.1941.0065

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The main principles governing the design of a city distribution system and their detailed application in the amalgamation of several undertakings are described. It is suggested that rationalization into larger units will extend, and therefore the problems of standardization are of particular interest at the present time.The standard system described utilizes a low-voltage grid with injections from a primary high-voltage network by means of decentralized transformers in accordance with load demand. The h.v. network is operated on a “radial” basis, and the l.v. network is “solidly” connected up to 3 000 kVA and further interconnected through fuses into 12 000-kVA units.The mode of operation permits of growth in loading without exceeding the initial rupturing duty on the switchgear, which is thereby allowed to serve its full life. Simple well-tried forms of protective gear are used and reliance is placed on “burning off” for clearing l.v. faults.Attention is drawn to the question of fault kVA in l.v. networks, and high-rupturing-capacity fuses are used in service cutouts and recommended for more general use.Improvements effected by the adoption of the system are mentioned, and in particular a comparison is made between adjacent districts developed on different systems. Each district had similar loads but the distribution cost for the one developed on the standard system was less, although the load had to be delivered over a greater area.It is claimed that the system which has been standardized is the one best suited for densely loaded areas; it has been applied to distribution in a large city over a number of years with successful results.

DOI:10.1049/ji-2.1941.0070

出版商:IEE    

年代:1941

数据来源: IET

DOI:10.1049/ji-2.1941.0073

出版商:IEE    

年代:1941

数据来源: IET

摘要:

The practice of power system interconnection which to-day, after more than a quarter of a century's gradual development, has become characteristic of the large-scale generation, transmission and distribution of electrical energy, is one which is based on a technique closely bound up with problems of system stability and power limitation. The starting point in the solution of such problems is, generally speaking, a determination of the power limit of an interconnector under a variety of operating conditions. By the term “interconnector” is here understood a compound power-transmitting circuit acting as a synchronous tie between two otherwise independent a.c. systems.The paper investigates the manner in which the electrical characteristics of a typical interconnector, comprising a transmission line and terminal transformers, limit the interchange of power between its terminal systems. A new method of evaluating the limiting transmitted power, based on the theory of the power circle-diagram, is described. This method employs a rapid geometrical construction for the appropriate charts which is based on the analysis established in the paper. The use of this new method of determining the power limit is illustrated by application to a specific example of interconnection.

DOI:10.1049/ji-2.1941.0074

出版商:IEE    

年代:1941

数据来源: IET