US981742A - Lightning-arrester. - Google Patents

Description

B. J. BERG. LIL-HTNING ARBESTER APILIOATION r1mn 11111111, 1901.

981,742. Patented Jan. 17, 1911.

UNITED STATES PATENT OFFICE.

ERNST J. BERG, OF SCHENEC'IADY, NEW YOBK, ASSIGNOR 'IO GENERAL ELECTBIC COM? ANY, A CORIORA'IION OF NEW YQEIK.

LIGH'IN'ING-ABBES'IEB.

Specflcaton 91. Letters Patent.

Patented Jan. 17, 1911.

Application flled June 1, 1907. Serial 11'0. 376,751.

Schenectady, county of Schenectady, State of New York, have invented certain ew and uscful Improvements in Lightningrresters, of which the fellowing is a specification.

My invention relates te devices fer pre tecting electric circuits and apparatus a ainst lightning and similar phenemena of a nermal voltage and abnorrnal frequency, and more particularly te devices for protecting either singlephase er pelyphase alternating-current systems of distribution.

In many alternating-current systems of distribution and particularly in polyphase systems, one of the conductors of the system is greunded threugh the generator and also through a transformer er ether translating device, and it is found that lightning discharges and ether abnermal and destructive disturbances tend te pass te greund through the generator er transformer rather than through the protective devices provided for that purpose. All the circuits of the system may be insulated froxn ground in which case the only path te ground is over the usual lightning arresters er threngh the insulatien of the system, and in en ungrounded systenr, even Wheh the lightning arresters are in goed condition, the lightning discharges tend te break down the 1nsulation of either the generators or the transformers before the insulatien en the ether parts of the system is aected. It is desirable, therefere, that the system be grounded, but in some ether manner than through the generator er transformer and preferably in such a marmer that one line of polyphase systern may be grounded without short-circuiting the system. It is also feund that if each conductor has a discharge path te ground censisting of a series of metallic cylinders separated in series with resistance and by air gaps made se as te prevent the dynarnic current following the very high voltages caused by light-ning, the low frequency oscillation cannot pass across all of the spark gaps of the discharge path te ground, while if the discharge path is of a length te re lieve the greter part of the abnermal conditions en the circuit numerous discharges tend te carry metal trom each cylinder and depesit it on the next, thereby gradually .bu1lding up metallic bridges across the gaps and tending te close up the air gaps until eventually there is ne spark gap path te greund for the high frequency esc1llatiens.

The object of my inventien is te provide alternating-current systems having all the circuits insulated rom ground with the same protection they would have if grounded threugh the generators and transformers, altheugh the generators and transformers are completely irisulated trom ground; te provide a protective device which will relieve the distribution system of oscillations of any frequency; and which will be more reliable and eective than the pretective devices heretofore in use.

In carrying out my nvention I insulate all circuits and cennect the system te an inductive device arranged te produce an artificial neutral, Which is cennected te ground through a current-limitingconnection, such as a resistance, te prevent a shortcircuit in case one of the concluctors comes in contact with the earth.

I provide an improved arrangement of reactances and cendensers te relieve the system of high frequeney oscillatiens, and te relieve the line of either low frequency er high frequency escillations I provide discharge paths which will always be in condition te relieve the system of high frequency oscllations regardless of the number of discharges which may have passed over thern.

My invention will best be understood in connectien with the accompanying drawing which is merely an illustration of one embodirnent of my invention and in which the figure shows my invention applied te a three-phase system, altheugh the invention is equally applicable te s1ngle phase sys tems or any other polyphase system.

In the embediment of the invention shown in the drawings a. three-phase generator 1 is connected te the conductors 2, 3 and 4 of the distribution system which delivers the energy of the generator to any suitable translating device. The generator 1, the conductors 2, 3 and 4 and the translating devices are all insulated from the greun and the enly connectien of the system te reund is through leads 5, 6 and 7 connect- 1ng the conducters of the system to an inductive device 8 having windings arranged to produce a neutrale which is connected through a leed 9 with a current limitin connecting or high resistance 10 connecte to ground. If one of the conductors should break and come into contact with the earth the resulting flow of current would be limited by the current-limiting connection or resistance 10; while as regards lightnin or similar disturbances, the systeni 1s as e ectually grounded through the inductive device 8 as is a system in'which one of the conductors is grounded through the generator and also through the transformers or other translating devices.

The high frequency oscillati0ns or surges upon the line are intercepted by a a reactance coil 11 in series with each conductor and directed to ground through condensers consisting of a condenser plate 12 connected to one end of each reactance coil and a condenser plate 13 connected to the other end, both of said plates being in inductive relation to a condenser plate 14 connected through a leed 15 and resistance 1'6 to ground. High frequency oscillations coming fron1 either side of reactance 11 pass from either plate 12 or plate 13 to the plate 14 and thence t0 ground. Each conductor is also connected te ground through a multigap arrester having a discharge path con sisting of metallic parts 17 in series and separated by air gaps. The arresters are connected by nieans of metallic connections 18 of high resistance so that thereis a discharge path from one to another through part of the gaps of one arrwter, through the connection l8and back through part of the gaps of the other arresterx There is also a discharge path toground through part of the air gaps of the arrester and thence through a portiori of the connection 18 and the resistance 19 to ground. The connection 18 and resistance 19 shunt a portion of the gaps of each discharge path, and a low frequency oscillation will pas over the air gaps to the connection 18, to ground through the Iesistance 19; While a high frequency oscillation will pass directly over the air gaps to ground even though the spark gaps betvveen the conductor and the connection 18 become more or less inefl'ective owing to' repeated discharges the spark gaps between the connection 18 and ground remain in goed" condition and ready to relieve the line of any oscillations which will not readily pass over the resistance 19.

The operation of this device is as follow's: A11 the circuits of the system are completely insulated from the rond, but the system as a whole is groun ed through the neutral of the inductrve device 8 and the current limiting connection 10. If a high frequency surge or oscillation is set 11 anywhere in the system it will not pass through the reactance 11, but will be discharged to ound through the condenser plate 14 and irectly over the air gaps of the discharge paths, the shunt connection throu h resistance 19 having very little effect. T e system isrelieved of other abnormal condit1ons b vdis charge over the air gaps to the co'nnections 18 and thence through the resistance 19 to ground and also by dis :harge to ground through the neutral of the inductive device 8 and the high resistance 10. Excessive tential betvveen phases is relieved by is charge over part of one multigap arrester, through connection 18 and are part of another arrester. The gaps shunted by the resistance 19 are always in operative condition and ready to assist the condensers in relieving the system of high frequency 0scillations. By my invention, therefore, the system is well protected against disturbances of any frequency or voltage and the tendency for discharges t0 pass to ground through the generators or through any 0 the translating devices is reduced to a mini mum.

My invention may be embodied in many different form's than these shown in the drawings, and I therefore do not wish to be restricted to the form shown and described but intend to cover by the appended claims all changes and m0difications which come within the spirit and scope of my invention.

VVhat I claim as new and desire to secure byLetters Patent of the United States:

In a protective device for electric systems, the combination with a reactance adapted to be connected in series with the conductor to be protected, of condenser plates connected on each side of said reactance, and a condenser plate connected to ground and in inductive relation to said first-mentioned plates.

In witness whereof, I have hereunto set my hand this 31st day of May, 1907.

ERNST J. BERG.

Wit nessesz BENJAMIN B. HULL,

HELEN Onronn.

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