CA1158298A - Valve arrester - Google Patents

Abstract

VALVE ARRESTER

Abstract of the Disclosure A value arrester comprises a serial arrangement which includes at least one nonlinear resistor and spark gaps implemented as arcing horns which are housed in slit-type arc extinction chambers whose walls are made of an electric insulation material and form a single helical blade. The latter is arranged on a central cylindrical member and adapted to produce a single helical arc which i.
formed from arcs struck during the arrester breakdown in the spark gaps, said arcs being joined together during their movement.

Description

~15~2~
VA~ ARRES~R
Field o~ the In~en-tion ~ he invent1o~ rel~tes to gap arresters generally used ~or the protection o~ power network~ ~rom overvol-tages, and more par~icularly to valve arre~ters~
~ he disclosed valve arrester is used ~or the protec tion o~ electric equipment a~d a.c. and d,c. power network~
from o~ervoltages.
De~cription o~ the Prior Ax~
A valve arrester should have a sufficie~t carr~i~g a~d arc eg~.inction capa~ity so as to allow ~or ~uick di~ersion to ground o~ an excessive charge tha~ arises in the network under protection, ~or example, due to a ligh~ning stroke, thereby limi~ing the ~urge impulse le-vel and duration. After the removal of the surge, the arrester ~hould provide ~or quick e~inguishing of the ~ollow current that pa~se~ through i~ and also ~or the reco~ery of the electric ~trength o~ it~ spark gaps.
Known in ~he art are valve arresters comprisi~g ~eries-connected spark gaps in the ~orm o~ arcing horns and nonlinear resi~tor~ (c~. a b~ok by D~V. Shishman et al. entitled "~igh-voltage Valve Arre~ters't, Energi~a Publisher~, ~eni~grad1 1971, pp.l4-28, 146-177, in Russian?O
~he ~park gaps ~n the known valve arresters are many and vAried, while means ~or the e~ti~ctio~ o~ the arc produced by the ~ollow current that arises in the arresters a~ter t~eir bre~kdown may be classed as to the charac~er of the 1 15B2'~

arc as ~ollows. immovable arc; rotatihg arc; split arc; self-blo~i~g arc; and extending arc~
~ he requirements imposed on the operating characteris-tics of the protection apparatus o~ the protection appara-tus of electric installations are continuousl~ increasing.
Therefore the constructors of valve arresters seek to decrease the level and duration of the oveIvoltage impulse in the network under protection and thereby increase the arrester carrying capacity, which is defined as the value of the discharge current passing through the arrester during the time o~ the overvoltage impulse, and increase the arrester arc extinction capacit~ as well.
~ most effective method that provides for greater arc extinction capacity of arc gaps is the magnetic blow-out method in which the arc tends to lengthen due to electro~agnetic interaction between the arc current a~d the applied magnetic field.
~ here is a valve arrester having voltage-limiting spark gaps and operating on the extending arc principle (cf. the US Patent No.3J611,045, c1.317-74, 1972). It comprises a serial arrangement of at least one nonlinear resistor a~d spark gaps implemented a~ arcing horns~ which are housed in slit-type arc ex~inction chambers having its walls made of an electric insulation material.
In this arrester, after the breakdown, the arc is extended from the arc gap and moves over the arcing horn3 due to electromagnetic interaction between the arc current ~ ~5~2~

and the magneti~ field produced by se~ies-connected mag-netic blow-out coils. Each spark gap o~ the arrester is housed i~ its o-~n flat slit-type arc e~tinction chamber ~ade of an electric insulation material. Connected in series with the spark gaps is an additional no~li~ear resistor which is designed to limit the follow current basicall~ at the time of the breakdown of the spark gaps when the pxesent total resistance of the arcs is smalla Since the volt-ampere characteristic of the additional resistor i~ nonlinear, a greater carrying capacity of the arrester is attained.
In the known valve arrester, the arc extinction capa-city is limited by the value of leng-thening the arcs in the flat arc extinction chambers. Moreover, the magnetic blow-out coils require more complicated circuit and design features of the arrester.
Summary of the Invention It is an object of the invention to provide a valve arrester having a large arc ectinction capacity.
It is a~other object of the invention to provide a valve arrester whose construction and electric circuit - are simple.
; ~here i3 provided a valve arrester comprising a serial arrangement which includes at least one nonlinear resistor and spark gaps implemented as arcing horns which are housed in slit-type arc e~tinction chambers whose walls are made of an electric insulation material, in which valve arrester~ accordin$ to the invention, said walls are implemented _ 4 _ -1 :~5~2~8 implemented in the form o~ a single helical blade arranged on a central cylindrical member and adapted to produce a single helical arc which is formed from arcs struck in the spark gaps during the arrester bre ~ own, said arcs being joined together du.:.ing -their movement, the arcing horns being situated between the turns of said helical blade, assuming a helical space orien-tation, and being affixed to the surface of the central c~lindrical member.
Advantageously, said nonlinear resistor should be inserted between the adjacent spark gaps and is shunted at the point in time when a single arc is ~ormed~ thereby providing for an increase in the arrester carrying capaci-t~
~ he disclosed valve arrester has, therefore, greater arc extinction capacity. Owing to the fact that the arcs occupy a smaller space and the nonlinear resistor takes up a smaller load, the valve arrester o~fers simpler design a~d decreased overall dimensions~
Brie~ Description of the Drawings ~ he invention will now be described in more detail, by way o~ e~ample~ with reference to the accompan~ing drawings, in which:
Figure 1 is a diagrammatic dimetric partially sec-tioned represe.ntation of a valve arrester, according to the invention;
Figure 2 is a sectional view on the lineII-II of ~igure 1, according to the invention; and .

~155~

Figure 3 is a sectional view on the line III-III of a valve arrester of ~igure 1~ according to the i~vention.
Referring to ~ig~l; the valve arrester of the inven-tion comprises arc extinction chambers 1 ~Fig.l) o~ its spark gaps which have their walls implemented in the form of a single helical blade 2 arranged on a central cyli~dri-cal member 3. ~hus the arc extinction chambers ~orm toge~her a single helical cavit~ so that a single helical slit is provided for all spark gaps of the arrester~ The central cylindrical member 3 is hollow and the blade 2 on the sur- :
face thereo~ has the lead of it~ helix equal to~ , the latter being in the range from 0.5 to 2 cm~ ~he member 3 and the blade 2 are made of an electric insulation material such as polysulfone carbonate, c-ast pol~eth~leneterephtha-late resin by using casting or stamping method. The blade 2 can also be composed of separat~ components which are joined to~e~her.
~ he width ~ of the arc extinction slit takes its value in the range from 1 to 8 mm depending on the rated value of the follow current through the arrester. The thickness of the helical blade 27 which is equal to the diX~erence ~-a, depends on the associated fabrication proces~ characteristics and on the rated service li~e o~
the valve arrester; this thiclness may be in the range from 2 to 10 mm, ~he formulas below give the external, D, and the 1 ~582g~

internal t d, diameters of the helicaI cavity ~f the arc extinction slit and also the length L of the valve ar-rester: p-d ~ 2J~(t)d ~

/I[US~ ( D = )t J

where E is the stre~th o~ the electric field established in a helical arc and re~erred to the e2ternal edge o~
the arc ~to the length of the leading edge of an arc that is extended in a radial direction); v(t) is.a time func-tion representing the radial speed of the arc; I(t) isthe time function representing the follow current; Us is the amplitude of the voltage rated ~or the network under protection; and ~ is the follow current extinction time~
; ~he value of d determines the inductive ~esistance of the valve arrester at the moment when breakdown occursO.
: The value above taken together with the resistance o~ the nonlinear resistor determine the value of the ~ollow current that arises at that moment, In a valve arrester with d=O, the leads running to the spark gaps and employed, for example, to co~nect shunts may be implemen-ted in the body of the ~elical blade 2~
Arcing ho~ns ~ connec~ed ~erially with one another by means of conductors 5 are housed-within the arc extinction slit on the sur~ace of the central cylindrical _ 7 1~5~298 member 3; the horns assume a helical space orientation and form the spark gaps of the arrester. ~or exampie, a spark gap with its arci~g horns 4 appears to be in the fifth turn of the arc extinction slit 9 while the conduc-tor 5 with the arcing horns 4 belonging to the adjacent spark gaps is seen in the third turn.
1'he arcing horns are designed to defina the direc-tion ~n which the supporting spots of arcs 6, produced in the spark gaps~ are moved. The arcs 6 responsible for the ~ollow current are moved ~1 a radial direction within the helical cavityjo~ the arc extinction slit under the action of force of electromagnetic in-teraction between the arcs and the magnetic field produced by the arrester.
After arcs 6 produced in the corresponding arc gaps have been extended to the ends o~ the arci~g horns 4, there results their joining together and a single helical arc 7 is thus formedO ~or the sake of simplicity~
Fig.l shows arcs 6, 7 present only at the fi~th turn o~
the arc extinction slit. Note that b~ the length of the arcing horns is mean-t herein the distance between their ends and the surface of the central cylindrical member 5.
Using the length and the height o~ the arcing hor~s9 one can determi~e a time interval during which the arcing horns 4 and conductors 5 are held in contact with the supporting spots of the arcs 6 till the moment when these arcs join together.

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2~

~ here are i~put, 8, and output~ 9, arcing ho1~ns in-tended for the displacement of the supporting spots o~ a si~gle helical arc 7 during the course of its e~tension and moveme~t in a radial direction~ ~he arcing horns 8, 9 are located respectively at the beginning and the end of the arc extinction slit. ~ihe arcing horns 8 connect an arrester lead 10, while the arcing horns 9 connect an arres~er lead 12, either in a direct way or via a nonli~ear resistor 119 ~he input arcing horns 8 are connected to the conductor 5 o~ the flrst spark gap~ while the output arcing horns 9 are connected to the conductor 8 of the last spark gap.
~ igure 2 shows the position of the arcs 6 correspond-ing to two successive points in time, 7'a" and "b", '~he position of the arc 6a corresponds to the moment when the arc 6 is struck at the start portions of the arcing horns 4.
~he position of the arc 6b corresponds to the moment when the arc 6 approaches the ends o~ the arcing horns ~; at that moment, one of the ends of the arc 6b is transferred ~dashed lines in Figo2) on to the input arcing horns 8, while the other end of the'arc 6b is joined together with analogous arc 6 available in the second spark gap (dashed lines in ~ig.2). As a result, a single helical arc 7 is formed. The position o~ the arc 7c corresponds to the point i~ time "c" when the helical arc 7 is e~tended, where-as one of the supporting spots of the arc 7c moves o~er the input arcing horns 8.

.

.

^1 ~5~9~

~ here are resistors within the hallow member 3 which are used to dis-tribute the potential amon$ the spark gaps, said xesistors being connected in parallel with said spark gaps~ Parallel connection of a shunt 14 to the first spark gap is established through holes 13 in the wall of the me~ber 3 and via the condu~tors 5. The shunts ~or the re~aining spark gaps (not shown in the drawing) are connected in analogous manner.
~ igure 3 is a lateral sectional view of the valve arrester of the invention that shows how the adjacent spark gaps are interconnected by means of a nonlinear re-sistor 15, which is shunted during the production of a sin-gle helical arc 7. ~eads 19, 20 located within the central ~ember 3 are connected through holes 18 in the wall of the member 3 to sections 16, 17 respectively of one of the conductors 5 having a discontinuity~ ~he nonlinear resistor 15 is connected ~he leads 19~ 20 With the arcs 6 in a position labelled 6b correspond-ing to the production of a single helical arc 7, there results a change in the path of -the follow current through the arrester (there are arrows in Fig.3 to shovJ the path~.
Prior to joining the arcs 6 together, the follow current'.
flows through the nonlinear resistor 15 connected to the leads 19, 20~ After the formation of a single helical arc 7, no curren-t flows through that resistor. '~
There ~a~ be a breakdown between the arcing hor~s 4. , of the adjacent spark gaps or the sections 16~ 17 of the con-- --10-- - , ~ 2~

ductor 59 said sectio~s 16, 17 being i~terconnected via the no~linear resistor 15, coupled to the leads 19, ~0 prior to the formation of a single helical arc 7. ~o avoid that breakdo~m, a radial partition (~ot sho~m) in the helical cavity of the arc e~t~Lction slit may be provided.
The partition installed between the ends of the sections 16, 17 and the adjace~t arcing horns is made o~ an electric insulatio~ ~aterial and has its height, as measured in a radial direction, exceeding the height of these arcing horns 4.
With the nonlinear resistor 15 located outside the member 3, the leads 19, 20 are pre~erably implemented as helical ones and are wound in opposition to the helical blade 2. As a result, the magnetic field of the arrester is increased. ~o provide ~or greater electric strength o~
the arresterj a cast electric insulation material may be filled in the cavity of the member 3.
~ he helical blade 2 of the arc extinction slit should be pre~erably implemented as a zigzag one in a radial directionO lhis protects the spark gaps from the radiation of the separated arc 7 responsible for the ~`ollow curre~t~
As a result, the recovery of the electric strength of the spark gaps is accelerated; the recovery process in this case mea~s the rise of the breakdowrL voltage of the spark gaps up to its rating level~
The valve arres-ter o~ the inve~tion operates in the following ma~nerO With an overvoltage applied to the ar--- 11 ' , ~ 1S~29~

rester3 there results a breakdown in its spark gaps. ~hiscauses the follow current to pass therethrough along a helical line a~d a longitudinal magnetic field~ as viewed -with respect to the arrester axis, îs establishedO ~
other words, a halical space orientation of the arcing horns 4 (~ig~l~ of the spark gaps and their conductors 5 provides these horns with an extra function which is usually performed by magnetic blow-out coils.
After the breakdwon, arcs 6 (Figs.l~ 2~3) are struck in the spark ga~s. As a result of interaction o~ the arc current wi-th said lo~gi-tudinal magnetic field the arcs 6 move in a radial (outward) and an azimuth direc-tion and also lengthen9 During the a~imuth movement~ on the ends o~ the arcs behave as if they recede from each other, when moving over the arcing horns 4. Wi-th the arcs 6 extended to the ends o~ the arcing horns 4, they are joined together so that a sin~le helical arc 7 is ~or~ed. The time counted since the ~oment o~ breakdown till the joining of the arcs 6 depends on the length and height of the arcing horns 4;
the two last values determine the length and resistance of the arcs 6 available at the moment o~ ~ormation of a single arc 7.
The formation of the arc 7 causes a shunted condition of those nonlInear resistors 15 which are inserted between the adjace~t spark gaps~ I~ this condition, the arrester resistance decreases in a stepwise manner~ with the result ~ 29~

.that the ~ollo~ current, which pas~es.~rom the netwo~k under protec~ion to the arrester9 increases. ~hus the carrying capacity o~ the arrester is incraased and the time required for the remoYal o~ the overvoltage from the network is decreasedO U~der the~e circumstanGes, ~he energy dissipated in the nonlinear resistors bei~g shunted9 is decreased~ 80 that these resistors ma~ have a smaller size~ ' ~ y using certain arcing hor~s 4 of di~ferent length and heigh~, one can select a specific shun~ time ~or each o~ the nonlinear resistors 15; thi~ provides for a nearly horizontal location o~ the correspondi~g step~ of the volt-ampere characteristic curve o~ the arre~ter. Under these circumstances, the requireme~ts imposed on the nonlinearity o o~ the nonlinear resistors are ~lOt rigorous.
A~ter a single helical arc 7 i~ ~ormed9 the conductors 7 and arcing horn~ 4 of all ~par~ gaps are di~co~nected from the current circuit . ~hus they are hea~ ed to a le~er ex-te:rlt and their service liIe is increasea. ~he helical arc 7 (a pla~ma solenoid) tends to exte~d more and more in a radial direction and to lengthen concurre~ At a predete~
mined a:rc length, the voltage across the arrester exceeds the protected network ~oltageO As a re~ultq the ~ollow current d:rops dowrL to zero and the arc 7 ceases. If th~
e~ces~ive discharge current existing in the netYvork under protection is not diverted to the ground and the over~oltage is not removed, the:o the e}~pansion o~ the arc 7 is co~ti-nued and the voltage across the arre~ter increases un~il -~, 1 ~5~98 its spark gaps are sub~ect to a breakdown a~ai~. Now the arcs 6 struck agai~ in the spark gaps are ~sed to shun~
the arc 7 and the latter ceases~ ~he operation c~cle of the arrester is repeated.
Since the disclosed arre~ter does no~ require a sp~ce intarval ~or the qu~nching oî the follow current9 it can be used in both d~c~ and a~c. pwoer networks~ providing ~or greater protectiorL oï them ~rom o~rvolt ages due to a decrease in the ~urge level and dura~ion.
The arc 7 e~tended in a radial directlon has.. a he-lical shape with a helix of a ~mall lead~ a ~e~ture pro-~iding for more ef~ective arc lengthening compared with flat-~hape arcs which are produc:ed in the known arc e~tinc-tion chamber~ hus t;he di~closed valve arrester has a considerabl~ increa8ed arc ex*inctio~ capacity and, con-sequen~ly, ~impler circuitxy not provided in this case with magnetic blow-out coils which require protection-t;ype bypass ~park gaps. Since the arcing hor~ the di~closed arre~ter are held in contact with the supporting spot~ o~
the arc~ ~or lesser time, their erosive wear is decrea~ed and the o~nductors are heated to a ~naller extexlt.
The ~hunti~g of the nonlinear resistor 15 has the ad-va~age~ a~ follows: greater carrying capaci~ of the v~l~e arrester (higher degree of nonlinearit~ o~ its ~olt-ampere characteristio); and small~r~amount of energy .dis~ipated in that re~istor du~ to the ~act tha~ its operation time i~
decreased~

Claims (2)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A valve arrester comprising:
arcing horns adapted to form spark gaps connected in series with one another;
at least one nonlinear resistor connected in series with said spark gaps;
arc extinction chambers in which said arcing horns are accommodated;
a single helical blade of an electric insulation ma-terial adapted to form the walls of said arc extinction chambers;
a central cylindrical member carrying said single helical blade;
said arcing horns located between the turns of said helical blade, assuming a helical space orientation, and affixed to the surface of the central cylindrical member, thereby provide for the formation of a single helical arc from the arcs produced is the spark gaps during the arrester breakdown, said arcs being joined together during their movement.

2. A valve arrester as claimed in claim 1, comprising:
said nonlinear resistor inserted between adjacent ones of said spark gaps and shunted at the point in time when said single helical arc is produced.