US2405121A - Counting device for overvoltage - Google Patents

Description

Aug. 6, 1946. P. FEHR V COUNTING DEVICE FOR OVERVOLTAGE Filed Aug. 5, 1943 INVENTOR fan! 7%! HTTORNEY Patented Aug. 6, 1946 COUNTING DEVICE FOR OVERVOLTAGE Paul Fehr, Zug, Switzerland, assignor to Landis & Gyr A. G., a body corporate of Switzerland Application August 5, 1943, Serial No. 497,441 In Switzerland November 7, 1942 3 Claims.

There are several devices known in the art for counting voltage surges on long overhead lines due to atmospheric influences or switchings. Such devices are based on magnetic, dynamic, thermal or chemical action of the current deflected by the protective devices in use.

For instance, in a known form of embodiment, at a voltage-dependent resistance of the overvoltage conductor, a part of the voltage drop caused by the deflected (or discharged) current is tapped and conveyed to the tWo coatings of a condenser to which an electro-magnetically perated counting train is placed in parallel. After having been charged, the condenser discharges itself over the counting train and moves the same forward by one step.

Another known type utilizes the thermal action of the deflected current by passing an endless strip of paper longitudinally and transversely between a spark gap, whereby the strip gets punctured at the incidence of a voltage surge.

In addition other arrangements have been known, which utilize electro-magnets in connection with spark gaps, explosion spark gaps, coherers, &c.

The purpose of all these known devices is to provide a check of the behaviour of the overvoltage conductor during the service and, for instance, to ascertain how often the excess voltage conductor is affected during a, thunderstorm and thus protects the plant from damage; in which part of the overhead line the lightning conductors have acted and, if possible, to measure the approximate strength of the discharged current.

Counting of voltage surges makes considerable demands on the counting devices, in view of the fact that the by-passed currents have a. very short duration, i. e. to 10" sec. and have a peak value of the order of 1000 amperes.

The present invention for counting momentary current impulses is characterized by the fact that a fraction of the deflected currents flowing through the conductance resistance is conveyed over a resistance which is in a tank filled with gas, whereby the gas expands under the influence of the ensuing heating and actuates the counting device through the medium of a flexible diaphragm.

The fundamental principle of the inventive idea may appear from a given form of embodiment according to the accompanying drawing, in which Fig. 1 showsa diagram of the arrangement.

Fig. 2 is a cross-section of the gas-filled counting tank and Figs. 3 and 4 illustrate other forms of embodiment.

The invention is based on the utilization of the thermal action of the deflected current, whereby thisaccording to the diagrammatic representation in Fig. 1is conveyed over a filament resistance I, which is in the counting tank 2 filled with gas. The closure of the tank 2 forms a flexible metallic diaphragm 3 being in connection with a counting train 4. Between the overhead line 5 and the ground lies the protective conductor 6. The counting device is interposed between protective conductor 6 and grounded conductor 1, whereby the deflected current passes via the parallel connection of a voltage-dependent resistance 8 and a reactor (or choking coil) 9. The counting train 4 and the metallic diaphragm 3 are mechanically interconnected.

Fig. 2 represents a sectional view of a form of embodiment of the actuating device for the counting train. The numeral 3 designates a diaphragm consisting of a corrugated metallic tube or pipe being slightly extensible in axial direction. The tube piece with flange 10 serves as connection between the corrugated metallic tube and the glass foot sealed onto it. The tank thus formed accommodates inside a filament resistance I carried by supports 12 that are adapted as current leads. The hollow space is filled with an inert gas possessing a small specific heat value. A socket [3 with connecting plug l4 holds the whole arrangement together. 7

On the lid of the corrugated metallic tube 3 a pin I5 is provided which transfers the movement of the diaphragm via the lever l6 by means of toothed segment I! and gear wheel l8 onto the counting train I 9.

In axially opposite position there is a compensating diaphragm 20 with which the influences of the ambient temperature on the diaphragm are nullified.

The action of the aforementioned device is as follows:

If a discharge occurs in conductor 6, the deflected current produces at the voltage-dependent resistance 8 a voltage drop. This voltage drop results in the transfer of a fraction of the deflected current over the filament resistance I, heating it. The heat thus produced i given off to the gas in the counting tank, which gas expands in consequence of its warming and drives the diaphragm 3 forwards, so that the pin [5 presses against the lever I6 which-by means of the toothed segment I'lturns the gear wheel I8 and hence the counting train l9.

excessive currents being forced through it. Thus,-

resistance 8 has a tendency to smooth or flatten the voltage rise across it as current goes up and preserves filament resistance i from destruction in case of intense discharge.

The reactor 9 connected in paralle1 to the voltage-dependent resistance 8 has in turn for its task to withhold from the counting tank the succeeding current emanating from the line voltage, which current flows after the proper rush dis charge. This is achieved by selecting such a value for the inductance of the reactor 9 that its impedance for the rush discharge is very high. A comparatively small inductance is required for this purpose due to the steep current surge. Such a small inductance, however, offers a low impedance for the succeeding current after the initial steep wave front has passed. Such deviation of the succeedin current is necessary because its I Rt-Value may assume very high figures, and this would lead to the destruction of the filament resistance.

The device may likewise be so disposed that the pin :5 of the diaphragm directly controls a contact (Fig. 3) which operates a relay 22, thus actuating the counting train 3-. It is further conceivable that the counting train be driven by a clockwork 23 (see Fig. 4) and that the axial shifting of the pin !5 causes the clockwork to run down or arrests it by releasing the disk 25 for one revolution at a time. This, for instance, is brought about so, that the pin 55 in its rest position impedes the disk 25 from rotating because it is in the path of an arresting pin 25. If the pin I5 4 moves upwards, the disk is set free and performs an almost complete revolution, that is until an arrestin stud 2'! engages the pin l5. By this rotation the counting train has meanwhile been driven through one figure only.

When the gas in the counting tank 2 cools off, the pin i5 moves downwards thereby releasing the arresting s ud 21; the disk 25 continues to r0- tate until the'arresting stud 25 again impinges on pin l5 and the original position is again restored.

The aforedescribed arrangement is adapted inv its employment for the counting and in combination witha suitable recording device for determining the approximate strength or the deflected current, whereby the expansion of the diaphragm is utilized as a base value.

It will be evident that equivalents of the parts of the arrangement employed to accomplish the action of my said device might readily be devised which, however, would not depart from the scope of my invention.

Having now particularly described and ascertained the nature of my present invention and in what manner the same is to be performed, I declare that what I claim is:

i. A device for counting momentary power surges such as caused by lightning on a transmisline, said ce including a main current conducting path, a resistance shunted across said main current conducting path, a gas-filled exoarsicle cherub-er surrounding said resistance wi the gas oeing heated by said resistance, a counting device associated with said expansible chamber to be operated by each expansion cycle.

2. The system of claim 1 whereby said main current conducting path comprises an inductance.

3. The system of claim 1 wherein said main current conducting path has a resistance characteristic such that the voltage drop across said path tends toward a maximum value irrespective 01 increase in current whereby said resistance shunted across said path is protected against excessive voltages.

PAUL FEHR.

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