FR2506067A1 - High voltage circuit breaker - where main switch has by=pass circuit contg. rows of resistors employed to quench arc when switch is opened - Google Patents

Abstract

The circuit breaker is located inside an envelope filled with compressed gas, and has at least one main switch or cut-out (a) with a mobile contact, and an auxiliary switch (b) with sec. contacts. Switch (a) has a by-pass circuit contg. a row of resistors (RU), which are each shunted by a resistance (RT). Each resistor (RT) possesses a resistance which suddenly increases greatly when a critical temp. is reached; and these resistors are pref. based on barium titanate. Each resistor (RU) has a resistance which varies with the voltage and where its conductivity grows exponentially with an increase in voltage; resistors (RU) are pref. based on doped zinc oxide. One preferred circuit breaker is designed for voltages below 30 kV. The main switch (a) has a relatively small size, but efficient arc quenching is achieved.

Description

High voltage circuit breaker
The present invention relates to a high voltage circuit breaker of the type comprising an envelope filled with compressed gas and containing a main cutoff point at the terminals of which is connected, in parallel, an auxiliary cutoff point in series with a set of resistors.

 By main cut-off point (or, for short, main cut-off), is meant a switch which inserts the Set of resistors into the circuit-breaker at the time of cut-out so as to reduce the current.

 By auxiliary cut-off point (or, for short, auxiliary cut-off), is meant a switch which then only has to cut the current reduced to a low amplitude by the resistance.

 The resistors usually used are metallic or graphite-based resistors, therefore having a substantially constant ohmic value.

 If resistors with a high ohmic value (several thousand or tens of thousands of ohms) are used for the equipment of the circuit breakers> the insertion of the resistance is difficult and the main break must be large enough to obtain a supply air very efficient of the main arch; but the current reduced by the resistance is very low (a few amps) and often a simple disconnector can be enough to cut it.

 If the resistance is of low ohmic value, its insertion is easier and the main cut is simpler and less expensive, but the current passing through the resistance and cut by the auxiliary cut can reach or even exceed 2000A, which imposes an auxiliary cut more complex with gas blowing and requires a great dissipation of energy in the resistance; this one and its envelope are voluminous.

 Resistors of variable value with voltage were also installed (non-linear resistors); but these resistances have very high values.

 Also known, in particular from English patent No. 645 004, the use of non-linear resistors of low value during closing, but of high value at opening.

 An object of the present invention is to provide a high voltage circuit breaker with compressed gas with insertion of opening resistance allowing on the one hand the use of a main cut-out of small size and low or no blowing, and on the other hand part of an auxiliary cut without gas blowing.

 The Applicant has had the idea of using variable resistances with temperature having characteristics close to those shown in the graph in FIG. 1.

 These resistors have an ohmic value substantially constant or slightly decreasing in a temperature zone between 20 and 1200C for example (from 60 to 40 ohms for example) and then grow very quickly (20,000 ohms to 140, 300,000 ohms to 1500 and 3,000,000 ohms at 1,600).

 Such resistors are known, but have never been used in circuit breakers. Indeed; in practice, it is possible to use several resistant elements in series, either in a single envelope or in several main envelopes in series.

 The elements undergo different heating consequently, the tensions appearing between their terminals can be badly distributed; some elements are overloaded, others on the contrary are more loaded. A capacitive voltage distribution between these elements would be bulky and expensive.

 The Applicant has observed that by combining in parallel with the resistors of the type designated hereinafter by RT type resistors, resistors whose ohmic value decreases when the voltage increases (and designated by resistors of RU type), it is possible to combine the advantages of insertion resistors of low value at the opening (easy insertion) and of high value at the time of breaking of the arc of the residual current.

 The heating of RT type resistors remains moderate, if the resistance is "monoblock" and of short length, the temperature varies little along the resistance and any increase in temperature leads to a higher resistance which limits the current and reduces it ; the temperature reaches an equilibrium value very quickly. Sitar contreJla resistance is not monobloc but made up of elements in series, these elements -may present at a given time different temperatures which for the hottest resistance leads to a higher voltage than for other resistors less hot than it but this higher voltage across this hotter RT resistor is also applied across the corresponding RU resistor which becomes more conductive and derives part of the current flowing through the hotter RT resistor, therefore there will be self-limitation of the current, therefore of the heating of the RT resistors and equitable distribution of the voltage on the RT resistors in series.

 The invention therefore relates to a high voltage circuit breaker intended to cut a circuit traversed by a current, comprising, in an envelope filled with compressed gas, at least one main cut-off point, comprising a main movable contact, a cut-off point secondary comprising secondary contacts and at least one set of resistors as well as means for temporarily inserting one of said sets in said circuit to be cut during the circuit breaker opening process / each set of resistors comprising one or more elements arranged in series, characterized in that each element is formed by placing a resistor of a first variable type in parallel with the temperature RT, the resistance characteristic of which as a function of the temperature has a marked bend in the vicinity of a value temperature data below which the temperature coefficient is low, positive or negative and above which the temperature coefficient e positive increases exponentially with temperature, and on the other hand a resistance of a second variable type with voltage RU whose conductance characteristic increases exponentially with the voltage applied across its terminals.

 Advantageously, the RT resistance of the first type is based on barium titanate.

 Preferably the resistance RU of the second type is based on doped zinc oxide.

The invention is clarified by the following description of several embodiments of the invention, with reference to the appended drawing, in which - FIG. 1 is a diagram representing the variations of the ohmic value as a function of the temperature of a resistor used in the circuit breaker of the inventiont - Figure 2 is an electrical diagram of a circuit breaker according to the invention - Figure 3 is a cross-sectional view of a circuit breaker provided with resistors according to the invention, - the Figure 4 is a sectional view along line IV-IV of the figure - Figure 5 is an enlarged view of a portion of Figure 3 showing the lower box of the circuit breaker / - Figure 6 is a sectional view along the line VI-VI of Figure 5} - Figure 7 is a developed view of an alternative embodiment of the box of Figure 5, - Figure 8 is a cross-sectional view of a circuit breaker according to another mode of embodiment of the invention - FIGS. 8A and 8B are views through cross sections along lines AA and BB of figure 8
2 - Figure 9 is a sectional view along line IX-IX of Figure 8.

 The invention applies to a high voltage circuit breaker which comprises, as shown in the diagram in FIG. 2, for each phase such as PI to be cut, a main switch 1 (or main break) and an auxiliary switch (or break auxiliary) of insertion 2 of a set of resistors.

According to the invention, the resistance set consists of a plurality of resistors RU1, RU2, ... RU n of the variable type with the temperature, the characteristic of which has a marked bend for a precise value of the temperature, each resistance RU being shunted. by an RT resistor (RT1 associated with RU1, RT2
at RU2, etc ...) whose conductance increases with the voltage at
its limits.

Figure 1 is a diagram of the ohmic value of
RT type resistance as a function of temperature. The scale
ordinate is logarithmic. We see that below 1400C
the resistance value is substantially constant. Above
of this temperature value, the curve has a bend
very affected.

This type of resistance is based on barium titanate
dope.

Resistors RU1, RU2, ..., RU n which, in Figure 2
respectively shunt resistances RTt, RT2, .., RT n by
bridges 3, 4, 5 are based on doped zinc oxide.

The operation of the diagram in FIG. 2 is as follows when the circuit breaker is closed, the switches 1 and 2 are closed, the current flows almost entirely through 1; indeed, the resistors RU1, RU2, ..., RUn, Ru1, RT2, ..., RT connected
RU1, RU2, RUn RT1, RT2, n in series-parallel have at the ambient air temperature a resistance of a few ohms, or tenths of ohms, while the natural resistance of switch 1 is very often less than a few dozen microhms.

On release, switch 1 opens; a bow takes
birth, shunted by resistances, and which will die out at
later at the first zero crossing of the current; the stream
passes through RT resistors / heats them by Joule effect (it
very little current flows through RU since the voltage
across these resistors remains relatively low); the
distance between the main contacts of switch 1
is sufficient to avoid re-ignition: the current is reduced
at a very low value, a few amps at most; switch 2
opens in turn and easily cuts such a current.

 If there is a difference in temperature between the RT elements in series, resistors of different values are in series and a high voltage (the voltage drop in the hottest resistor) may appear which would be dangerous for the resistance element ; but the resistance value RU which is in parallel decreases when the voltage rises which builds up the decrease in current in the corresponding RT resistance the resistance RU therefore opposes the different variations in the heating of the RT resistors by automatic regulation of current in RT.

 3 shows, in cross section, a high voltage circuit breaker containing sulfur hexafluoride and which is provided with the resistors described above.

 In reality, FIG. 3 represents the part of the circuit breaker corresponding to a phase, it being understood that the circuit breaker comprises three distinct identical sets.

 It has also been assumed that there is only one interrupting chamber per phase, the extension to a plurality of interrupting chambers per phase is obvious and within the reach of those skilled in the art.

 A frame 10 supports a hollow support insulator 11 and a switch box 12 whose role will be explained below. A plate 13 carrying an outlet 15 closes an insulating envelope 14 provided with fins for mounting outside a cover 16 closes the upper part of the enclosure 14 and carries the other outlet 17.

 At the inner part of the cover 16 is a fixed contact rod 18, terminated by streaks oriented so as to rotate the arc when it arises, and centered in the axis of the envelope.

 Around this contact rod 18 are regularly distributed stacks of resistance wafers, housed in insulating cylinders such as 19 and 20. As shown in FIG. 4, there are 8 resistance stacks, grouped in pairs, ie 4 sets of 2 resistors, one variable with the temperature 21, (21a, 21b, 21c), the other variable with the voltage 22 (22a, 22b, 22c) corresponding respectively to RT and RU of figure 2.

 Each pair of batteries is provided at its base with an individual tray 23 (23a, 23b, 23c) holding between them the two batteries of the pair and centering them in the envelope 14; these plates can be partially insulating towards the insulating envelope but they are metallic conductors and terminated by a current range 24 (24a, 24b, 24c). The resistance wafers are separated by conductive washers 25 and the conductive washers 25 of two juxtaposed batteries 22, 23 (22a, 23a etc.) are electrically connected by conductors 26 which act as bridges 3, 4, 5 etc. .. of figure 2.

 The plate 13 carries contact fingers 27 to collect the current on the movable rod 28.

 The moving element comprises a rod 28 surmounted by a main end contact 29 cooperating with the fixed contact 18 and having like it streaks oriented for the rotation of the arc.

 The rod 28 is extended by an insulating rod 30 and by a steel rod 31; the rod 31 is associated with means which allow it, when it moves in translation in a given direction, to perform at the same time a rotation of a given angle (90Q for example).

 These means may include, as shown in FIGS. 5 and 6, vertical grooves 40 (four in the example of the figures for a rotation of 900) -practiced in the inner part of the cylindrical box 12. These vertical grooves carry a ramp 41 at their top. The vertical grooves are further connected two by two by helical grooves 42 going from the top of a vertical groove to the bottom of a neighboring vertical groove.

 The rod 31 carries a pin 34 in the shape of a finger, which can be erased inside the rod and recalled by a spring not visible in the figures.

 If the rod 31 moves from bottom to top, the lug follows a vertical groove and gradually disappears when arriving on the ramp and protrudes again after passing the highest point of the ramp.

 If the rod descends, the lug which abuts on the upper part of the ramp, can only take a helical ramp, this results in a rotation of the rod 31 of 900 during its translation.

 As a variant, the grooves have the shape shown in FIG. 7 which is an involute of the internal surface of the tube 12.

 The vertical grooves 40A are connected to the helical grooves 42A by acute beaks 44 which force the lug to follow the prescribed path (indicated by the arrows) without the possibility of taking the same path twice. The lug then does not need to be erasable.

 As a variant, and for the two embodiments of the means for rotating the rod 31 which have just been described, the lug may be arranged on the wall of the box 12, the grooves being formed on the surface of the stem 31 itself.

 In addition there may be one or more pins.

 Returning to FIG. 3, on the conductive part of the rod 28 is an arm 32 terminated by a contact 33 which cooperates successively with the four contact pads 24, 24a, 24b, 24c, then again 24, 24a, .. .etc ...

 The range 24 is large enough for the contact with 33 to last long enough to avoid any re-ignition of the arc between the contacts 29 and 18.

 The enclosure 14, the insulator 11 and the box 12 are filled with insulating gas such as sulfur hexafluoride.

 The circuit breaker operates as follows, the device is closed, the current flows through 17, 16, 18, 29, 28, 27, 13, 15, a very small fraction of the current also passes through 16, 21b / 22b, 24b, 33, 32, 28, during opening, a mechanical, hydraulic or pneumatic actuating member lowers the rod 31, 30, 28, 29 while allowing its rotation; an arc arises between 29 and 18, then goes out at the first zero crossing of the current which then passes entirely through the resistors 21b and 22b, the current reduced by these resistors is cut by separation of the contacts 33 and 24b.

 Initially, the stroke of 28 is rectilinear then it becomes helical which causes the rod to turn 900.

 During reclosure, the rod has a simple translational movement from the bottom up without additional rotation, the contact closes between 33 and the range 24c located at the rear at the bottom of the resistors 22a, 22c; the main contact closing very quickly? the closing current does not have enough time to heat the resistor 21c enough to bring it to a temperature close to the bend in FIG. 1. Less hot than the resistor 21b, it is able to operate on a second opening in good conditions. The arrangement with 4 sets of resistors thus authorizes the operating cycle following opening, reclosing, opening reclosing, opening, reclosing, opening.

 We could only have 3 sets of resistors to satisfy the normal operating cycle, specified by the regulations.

 In this case, three pairs of resistors at 1200 are provided and three grooves are placed in the box 12 so as to allow 7200 rotations of the operating rod of the movable contact.

 FIGS. 8 and 9 relate to a circuit breaker provided with sets of resistors according to the invention with two breaks in series per pole.

 The figures represent a pole of such a circuit breaker.

 The cut is enclosed in a metal enclosure.

The outputs are described below.

 The activated part resting on a fld chase is a metal casing 50 made of cylindrical aluminum alloy, the ends of which are closed by covers 51 and 52, the cover 51 allowing the control shaft 53 to pass. Two openings are provided and terminated by opposite flanges 54 and 55.

 Two insulating cones 56, 57 hold the opposite fixed contacts 58 and 59 having laterally a protrusion forming a spark arrester 60 and 61.

 On the fixed contacts are mounted on either side two sets of resistor batteries 65, 66; 65a, 66a,; and 67, 68; 67a, 68a.

 Resistors 65, 67, 65a, 67a are variable with temperature RT and resistors 66, 68, 66a, 68a are variable with voltage RU. The batteries are arranged inclined and are terminated by a sliding contact 69, 70, 69a, 70a.

 The mobile assembly comprises a shaft 53 comprising metal ends rotating in the bearings 71, 72 provided on crosspieces 73, 74.

 Two insulating parts 75, 76 with a long line of flight and a central part 77 on which several arms are placed.

 Four cross arms, forming main contacts 78, 79, 80, 81 each have a spark protector such as 82, 83, 82a, 83a, which will cooperate with the spark arrester 60, 61. These arms are in the axis of the device.

- Two arms 84a and 85a longer than the main arms 7880 offset angularly in front of 20 to 250 with the main arms 78-80 (see Figure 8) and offset laterally (on the back of Figure 9).

- Two arms 84 and 85 longer than the main arms 7981 angularly offset in front of 20 to 250 with the main arms 79-81 and laterally offset on the front of Figure 8 (visible in Figure 9) the arms 84- 85 therefore form an angle of 900 with the arms 84a, 85a.

- The outputs of the metal casing 50 are made in the case of a conventional circuit breaker by two crossings located on either side of the casing but only one of which is shown in partial section on the left of the figure, a horn 100 is surmounted by an insulating bushing 101, the conductors 102 and 103 are centered in the horn and the bushing, they are connected on the one hand to the conductive part passing through the cone 56, on the other hand to the socket outlet 104 for connection.

A deflector 105 distributes the electric field, and at least one current transformer 106 is placed at the base of the bushing.

-In the case of a post in a metal envelope filled with compressed gas, the outlets are made by ferrules 111 containing the conductor 110, only one of which is shown on the right of FIGS. 8 and 9.

 It is also possible, in a hybrid solution to have, as shown in Figures 8 and 9, on one side a bushing for air connection, and on the other side a ferrule for connection with a busbar under ferrules.

- the envelopes are filled with SFS and have their filling and pressure control devices.

 The circuit breaker operates as follows - the device being open, a rotation of the shaft 53 in the direction of the arrow F causes the contacts 78 and 58 to come into contact simultaneously and on the one hand and 80 and 59 on the other part, after an angular stroke of 450. At the end of the stroke, the arms 84a and 85a come into contact respectively with the contacts 69a and 70a) thus putting the resistors 65a, 66a, 67a, 68a into service; the current flows almost entirely through the main contacts, i.e. 103, tO2, 58, 60, 82a, 78, 80, 83a, 61, 59, 110.

a very low current flows through the resistors 65a, 66a, 67a, 68a located at the rear of the plane of FIG. 8 and in the upper part of FIG. 9.

 When the shaft 53 is triggered by rotation of 450, still in the direction of the arrow F, the main contacts separate; two main arcs arise on the one hand between 0 and 82a and on the other hand between 59, 33a; the current flows completely through the resistors 65a, 66a, 67a, 68a, after the main arcs have gone out, and the current reduced by the resistors is cut by the arms 84a and 85a, which have left the contact pads 69, 70 after a some linear travel between the main contacts.

 Upon reclosure, the main arms 79 and 81 will close while the auxiliary arms 84 and 85 will be put into service, the resistors 65, 66, 67, 68 located in front of the plane of FIG. 8. Thus, during the next breaking, the resistors 65, 66, 67, 68 which have not been heated by the passage of current during the previous breaking are capable of ensuring a correct breaking, allowing the resistors 65a, 66a, 67a, 68a to cool.

 The timing between the auxiliary arms and the main arms can vary depending on their spacing, it is sufficient that the distances between the parts of different potentials are similar.

 The main cut-off can be fitted with a blowing device at the end of the arc, to facilitate the extinction of the arc and the insertion of the resistors.

 We can also place the three phases in the same enclosure 50 which would be longer and have six outputs instead of three, the tree would be unique, but this would prevent pole-by-pole maneuvering.

 The invention has been illustrated by two examples in which the main break is shunted by an assembly comprising, in series, an auxiliary break and a break resistor (parallel mounting).

 Of course, the invention applies, MUTATIS MUTANDIS, in the case of series mounting in which the main cut is permanently shunted by the resistors, the auxiliary cut being in series with the main cut, the latter being able to open and close after the auxiliary cut-off is extinguished, the latter ensuring the closing of the current.

 In the case of medium-voltage circuit breakers (4 to 30 kV), the RT type resistors are homogeneous and their length is such that only one resistance can be placed per phase, the voltage distribution between resistors connected in series no longer makes sense, and in this case, you can only use RT type resistors, excluding RU type resistors.

Claims (10)

1 / High-voltage circuit breaker intended to cut a circuit traversed by a current, comprising, in an envelope filled with compressed gas, at least one main cut-off point comprising a main movable contact, a secondary cut-off point comprising secondary contacts and at at least one set of resistors as well as means for temporarily inserting one of said sets in said circuit to be cut during the opening process of the circuit breaker each set of resistors comprising one or more elements arranged in series, characterized in that each element is formed by the paralleling on the one hand of a resistance of a first variable type with the temperature (RT) whose characteristic resistance as a function of the temperature has a marked bend in the vicinity of a given value of temperature below which the temperature coefficient is low, positive or negative, and above which the positive temperature coefficient increases exponentially ent with the temperature, and on the other hand a resistance of a second type variable with the voltage (RU) whose conductance characteristic increases exponentially with the voltage applied to its terminals. 2 / A circuit breaker according to claim 1, characterized in that the resistance (RT) of the first type is based on barium titanate. 3 / Circuit breaker according to one of claims 1 and 2, characterized in that the resistance (RU) of the second type is based on doped zinc oxide. 4 / Circuit breaker according to one of claims 1 to 3, characterized in that it comprises means for closing the circuit breaker on a set of resistors (21, 22) which have not been crossed by the current during the 'previous opening. 5 / Circuit breaker according to claim 4, characterized in that the resistance sets (21, 22) are regularly arranged around the main movable contact (28) and carry contacts (24) intended to cooperate with the secondary contacts themselves integral of the movable contact, the main movable contact being provided with means (31, 40, 41, 34) to enable it to perform a partial rotation on itself at the same time as it moves in translation in a given direction. 6 / A circuit breaker according to claim 5, characterized in that said means comprise a set of vertical grooves (40) connected by helical grooves (42), formed in the internal wall of a cylinder (12) in which engages a rod extending the movable contact, at least one lug (34) carried by said rod engaging in said grooves. 7 / circuit breaker according to claim 6, characterized in that said means comprise, practiced in the rod extending the movable contact, a set of parallel grooves connected by helical grooves, said grooves cooperating with at least one lug, fixed relative to said rod. 8 / Circuit breaker according to claim 6, characterized in that the movable main contact consists of first arms (82) rotating about an axis (53) perpendicular to the plane of the first arms, said secondary contacts being carried by second rotating arms about the same axis, said second arms (84) being angularly offset from one another and relative to the first arms and being located in at least one plane parallel to and distinct from the plane of the first arms, said second arms cooperating successively in rotation with the various sets of resistances. 9 / High-voltage circuit breaker intended to cut voltages below 30 kv, comprising, in an envelope filled with compressed gas, at least one main cut-off point comprising a main movable contact, a secondary cut-off point comprising secondary contacts and at at least one set of resistors as well as means for temporarily inserting one of said sets in said circuit to be cut during the circuit breaker opening process, characterized in that the resistors are of a type (RT) variable with temperature, the characteristic of which resistance as a function of temperature has a marked bend in the vicinity of a given temperature value below which the temperature coefficient is low, positive or negative, and above which the temperature coefficient increases exponentially with temperature . 10 / A circuit breaker according to claim 9, characterized in that the resistance is based on barium titanate.