US1755979A - System for the protection of electrical installations against overvoltages - Google Patents

Description

'1 April 22, 1930. (:AMPQS 1,755,979

SYSTEM FOR THE PROTECTION OF ELECTRICAL INSTALLATIONS AGAINST OVERVOLTAGES Filed Dec. 20, 1926 .zv vvenl of I in/o (am as Patented Apr. 22, 1930 UNITED STATES GINO CAMPUS, OI MILAN, ITALY SYSTEM FOR THE PROTECTION OF ELECTRIGAL INSTALLATIONS AGAINST OVER- VOLTAGES Application filed December 20, 1926, Serial No. 156,037, and in Italy January 9, 1926.

It is well known that the overvoltages which are accidentally produced from various causes in electrical installations, meet with an obstruction which prevents their propagation in each conductor at all points at which there are sudden variations in the electrical or magnetic characteristics (inductances, capacity, etc.) of the conductor; this obstruction frequently causes lateral discharges to earth or 1 between adjacent conductors or even between successive points in the same conductor. It

is also known that these overvoltages have.

what may be termed a directional inertia resulting in a tendency to travel in a straight line in the direction in which they are guided by the conductor, and consequently at each point in a conductor where there is a change of direction of the conductor there is also a tendency to lateral discharges which is the more marked, the more sudden the change in direction. This phenomenon has been employed to bring about lateral discharges at desired points by arranging sharp changes of direction at these points in the conductor carrying the electric current.

The present invention consists ina system for the protection of electrical installations against overvoltages in which at least some of the line conductors leading to the part to be protected contain a series of sharp deviations at a conveniently selected point in their length. The deviations may be furnished with prolongations, extending in the original direction; and to the peaks of said deviations are connected shunts to successive points of the same conductor through resistances which are preferably disposed to lie in the same direction as the part of the conductor from which the overvoltages may arise. These resistances may be replaced wholly or in part by spark gaps, or by a resistant mass or body in which the conductor may be embedded totally or in part but theymust be insulated from the other line conductors and from-earth in such a manner that the overvoltages which have a tendency to keep the original direction of the conductor which they are following, are discharged and dissipated in these successive resistances without the production of danger- 0 ous leakages to earth or to other line conductors, whilst the normal current in the installation is subjected without difficulty or inconvenience to a series of sharp changes in direction in its passage towards the part which it is desired to protect. a

The accompanying drawing shows by way of example several methods of carrying out the invention.

Fig. 1 is a diagrammatic view Fig. 2 shows an arrangement in which protection is efi'ected by means of resistances only; i

Fig. 3 shows an arrangement in which spark gaps are employed;

Fig. 4 illustrates an arrangement employing resistances and spark gaps in combination; and

Fig. 5 shows a protective arrangement in which the sharply bent conductor is embedded in a high-resistance body.

Referring to Fig. 1, it will be seen that between the conductor L and the conductor L which are traversed by the electric current there is a deviating portion L which forms two sharp changes in direction at Z and Z at those points at which it joins the conductors L and L, and that between these points of sharp change of direction there is a space A. Any overvoltages which may be superimposed upon the normal operating current from one of the conductors L and L tends to travel across the gap A in a straight line, instead of following the conductor L, owing to the directional inertia effect referred to above. If, in the gap A between these two I conductors L and L, there are disposed in a straight line with said conductors, high resistances w and w or a spark gap 5, or both (as shown in the drawing), the overvoltage discharge itself gives rise to a temporary,

current which is transformed into heat and so dissipates its energy.

The arrangements which can be adopted in practice are very numerous and they vary according to the form which is given to the. bends in the conductor. They may however be arranged in four gnoups, each of which can have two forms, according to whether the arrangement of bends is symmetrical with regard to the two directions of approach or whether they are provided to deal with only one direction of approach of the overvoltages. In the accompanying drawings, only symmetrical arrangements are dealt with, the necessary changes to asymmetrical arrangements being readily effected.

In the protective arrangement shown in Fig. 2, between the peaks of the bends in the conductor L are inserted high resistance blocks W. In the arrangement shown in Fig. 3, only spark gaps s are provided. In the arrangement shown in Fig. 4, there are employed high resistance blocks IV and W" and interposed spark gaps s. In the protec-- tive arrangement shown in Fig. 5, the sharply bent conductor L is completely embedded in a resistance body IV in which the energy corresponding to the accidental excessive voltage may be dissipated, whatever the manner in which the discharge takes place.

I claim as my invention:

. 1. In a system for the protection of electric installations against overvoltages, a conductor inserted in the line to be protected and formed with sharp bends in a direction opposed to that of the arriving current, and ohmic resistances shunted on the line and completely insulated from ground and from the other oonductors of theline and acting to obstruct the passage of the ordinary line currents, but to dissipate in the form of heat the currents produced by the overvoltage; each bend having its, peak connected .to one end of a resistance, the Other end whereof is connected to said conductor at a point further down the line, said resistances being located substantially in the direction of the arriving current.

2. A protective system, according to claim 1, in which the ohmic resistances include spark gaps for dissipating the overvoltages.

3. A protective system, according to claim 1, in which the ohmic resistances for dissipating the overvoltages include both spark gaps and resistance bodies.

In testimony whereof I aflix my signature.

GINO CAMPOS.

Images