US2688715A

US2688715A - Surge diverter

Info

Publication number: US2688715A
Application number: US164355A
Authority: US
Inventors: Vorts Svend Aage; Nilsson Erland Bertil
Original assignee: ASEA AB
Current assignee: ABB Norden Holding AB
Priority date: 1949-06-18
Filing date: 1950-05-26
Publication date: 1954-09-07
Anticipated expiration: 1971-09-07

Description

Sept. 7, 1954 s. A. vR-rs ET AL SURGE DIVERTER Filed May 26, 1950 l 'ab l /oo Invemor m o SS Png fri" WN en @JH a e d d n n e Ym, 5E d m a Q Worm@ Y,

Patented Sept. 7, i954 SURGE DIVERTER Svend Aage Vrts and Erland Bertil Nilsson, assignors to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Application May 26, 195o, serial No. 164,355

Claims priority, application Sweden June 18, `1949 Ludvika, Sweden,

Modern surge diverters usually consist of a series of spark gaps in series with a Valve resistor, usually consisting of blocks of a material with voltage dependent resistance. At high voltages, these parts have been enclosed in a series of tubular insulators. The number of insulators or units arranged above each other is determined by the line voltage. As the spark gaps moreover are generally connected in parallel with controlling resistors, an even voltage stress is obtained on the spark gaps at low steepness of the Wave front of the over-voltages, but at high steepness, the voltage distribution is determined by the capacity conditions. This causes a lower ignition voltage on the whole series of spark gaps at high steepness than at a low one. By itself it is not inconvenient if the decrease of the ignition voltage only sets in at a considerably high steepness. If, however, the decrease of the ignition Voltage sets in at a low steepness, it is possible that the surge diverter is ignited at normally occurring switching over-voltages, which generally is not desirable.

By the uneven voltage distribution also the extinguishing ability of the Whole series of spark gaps is lowered as a consequence of the fact that if a spark gap in the series is not capable of withstanding the recovery voltage, it re-ignites,` with the result that also the following lspark gap ignites, and so on, until the whole series has ignited. Also by this reason it is desirable that the even voltage distribution is maintained up to considerably high steepness.

The present invention relates to a surge diverter, especially for high voltages in which the above mentioned uneven voltage distribution is considerably equalised, and it is characterised in that the total number of spark gaps in the diverter is distributed on the diierent units in approximate proportion to the natural voltage distribution along the diverter, i. e. the voltage distribution which is caused by the capacity conditions. By this means, the Voltage stresses on all the spark gaps will be about the same.

The invention will be best understood with reference to the accompanying drawing, in which Figure 1 shows a section through the surge diverter, whereas Figure 2 shows a diagram of the voltage distribution.

In Figure 2, the dash-line curve shows the approximate voltage distribution along a pile of insulators according to Figure 1, without precautions for voltage equalisation, whereas the full-line curve shows the voltage distribution along the insulators according to the arrange- 3 Claims. (Cl. 317-70) ment shown in Figure l, and the chain-line curve represents the voltage distribution inside the insulators, i. e. along the resistors and piles of spark gaps, before the diverter has ignited.

In the form of the invention shown in the drawing, l designates the insulator cylinders piled on each other and held together by means of metal anges 2. A connecting terminal for the line is denoted 3, and 4 is a voltage equalising metal ring which by means of arms 5 is supported by the top flange 2. Inside the insulators l, piles of spark gaps 6 are arranged, in series with which in every unit are arranged piles o'f voltage dependent resistor blocks l. The bottom unit contains only such voltage dependent resistors.

Because of the fact that the insulators may become outwardly conductive owing to dust or moist coating, it is possible to obtain a voltage distribution across lthe different units, not corresponding to the normal voltage distribution, and thus neither to the distribution of the spark gaps. This may cause an overstrain of the spark gaps in the units which contain a smaller number of spark gaps. According to the invention, this is prevented by adapting the effective external length of the insulators to the number of spark gaps' in the diverter units by outwardly shortcircuiting part of them. In the form shown, this is obtained by providing the outside of the insulators at a suitable height with a bandage 8, conductingly connected with the anges 2 at the lower part of the insulators. This bandage may of course be substituted by metallising or some other conducting covering.

It is not necessary that all units contain spark gaps, but in some cases it may be convenient to connect one or several units, only containing resistors, in series with units containing spark gaps.

We claim as our invention:

1. A surge diverter comprising a plurality of insulator cylinders piled upon each other, conducting anges joining said cylinders, voltage dependent resistors in said cylinders, and a number of series connected combined switching and quench spark gaps of equal length in each cylinder in series with said resistors, said number being different in each cylinder and accommodated to the voltage -falling on each cylinder due to the natural capacitive voltage distribution atthe appearance of a voltage surge.

2. A surge diverter comprising a plurality of insulator cylinders piled upon each other, conducting fianges joining said cylinders, voltage de pendent resistors in said cylinders, a number of pendent resistors in said cylinders, a number: of.

series connected combined switching and. quench spark gaps of equal length in each cylinder in series with said resistors, sadiriumber being `diff ferent in each cylinder and accommodated to the voltage falling on each cylinder due to the natural capacitive voltage distribution at the appearance ot a voltage surge,` and metallic. shields outside part of the cylinders each shield short-circuiting the external surface of the part of the cylinder outside the resistors, said shields consisting of a metal bandage.

RefcrencesOltcd inrthmfile of this Apatent UNITED STATES PATENTS Number Name Date 1,754,158 Goodwin Apr. 8, 1930 2,032,566 Earle Mar. 3, 1936 2.1351135 Ludwig Nov. 1, 1938 2,179,297 Johnson Nov. 7, 1939 2;298,114f Eitorff Oct. 6, 1942 2,586,285 Ackermann Feb. 19, 1952 FOREIGN PATENTS Number Country Date 343,049 Great Britain Feb. 11, 1931 699,016 Germany.- Nov. 21, 1940