FR2462713A1 - Voltmeter for continuous HV with superimposed alternating component - uses resistive potential divider connected to protective amplification circuit via measuring conductor(SE 2.3.81) - Google Patents

Abstract

The voltmeter is esp. for high voltage distribution network using a gas insulation for a screened conductor. The conductor is connected to time resistors (18,20) forming a potential divider to which a measuring conductor (22) is connected. The resistors enable a voltage to be obtained which is independent effects. The measuring conductor passes through an insulated hole in a cover of the metallic screen and allows the voltages w.r.t. ground to be measured by an instrument (26) connected via a protective amplification circuit (24).

Description

 The invention relates to a device for measuring high continuous voltages in high-voltage distribution installations, in particular in distribution installations with metal shielding and gas insulation with sulfur hexafluoride (SF6), device comprising at least two ohmic resistors forming a voltage divider, connected in series between the high voltage potential and the ground and one of which, that is to say the one which is connected to ground, serves as a measurement resistor.

Ohmic voltage dividers of this type, in which the resistance which is at ground potential serves as a measurement resistor, are known for outdoor installations of high voltage direct current transmission. A line of resistors gathered in a strip is coated with a molded resin in order to increase the mechanical resistance and includes a porcelain cap and oil insulation. The dimensions of this voltage divider are very large, because they must be a function of the height of the porcelain cap, this height being determined by the length of the disruptive discharge and the leakage path between the high voltage potential and the ground.

 A measuring generator which is known for shielded high voltage direct current transmission devices comprises two approximately circular elements of sheet metal having notches in segments and rotating relative to each other. When a sheet metal segment of one of the elements crosses the free space of the other element while passing over it, a migration of charge carriers occurs and therefore a current flow which is proportional to the voltage to be measured. The fact that the mechanical elements are rotary is the cause of some wear which lowers the useful life. The particular problem which arises however in this case is that the generator makes it possible to measure only the DC voltage and not the superimposed ripple. The components in AC voltage cannot be measured without an auxiliary element, for example a measuring device capacitive. Furthermore, it is also not possible to detect the polarity of the measured DC voltage.

The subject of the invention is a device of the type as specified which also makes it possible to detect alternating voltages when it is applied to screened installations and whose overall height can be reduced considerably compared to distribution installations mounted outdoors. , so that this device can also be arranged simply and with a small footprint in shielded installations.

 According to an essential feature of the invention, the device comprises at least two ohmic resistors connected in series between the high voltage potential and the ground, one of the resistors, that which is connected to ground, serving as a measurement resistor and these resistors forming together an ohmic voltage divider.

 The particular advantage of this arrangement lies in the fact that an AC voltage component superimposed on the DC voltage can be measured without additional precautions or any other element, no additional capacitive measuring device being necessary, the device of the invention can be implemented with a very small footprint, so that it can also be mounted in distribution installations with metal shielding and gas insulation with SF6.

 The resistor located on the upper voltage side or on the high voltage side may be formed of elements of substantially identical conformation, so that a series circuit can be constructed in a simple manner and formed of several elementary resistors intended to constitute a common resistor under higher voltage and forming part of the voltage divider can be adapted to different levels of nominal voltage. The different resistance elements being identically shaped, the resistance located on the high-voltage side can be assembled in modular form with several elements -adapted to the levels concerned and required for the nominal voltage-.

 It is possible, as mentioned, to give the same dimensions to the resistors; it is of course also possible to give different dimensions to the different resistance elements; it is then possible to obtain the adaptation to the corresponding levels of the nominal voltage by mounting the various resistance elements selected accordingly in a metal shielding which remains the same for many nominal voltage levels.

 According to a particularly advantageous embodiment of the invention, an insulating body which can be used for the formation of a resistance element serves as a substrate for the resistance material. The use of the insulating body promotes the mechanical resistance of the various resistance elements.

 The insulating body may advantageously have the form of a plate on each of the surfaces from which the resistance material can be deposited. The individual insulating bodies can have a constant thickness in the radial direction, but they can also have the shape of a disc whose thickness is reduced towards the outside. The insulating body in the form of a plate, the thickness of which is approximately constant, may have, in the vicinity of its axis of symmetry, an additional thickness projecting at least on one side and intended to maintain the distances between two neighboring insulating bodies; the extra thickness may also be provided at the periphery and, in the latter case, it may have slots oriented approximately radially. The shape of the disc is adopted because it is best suited to the dielectric forces inside the insulating body and in the path followed by the gases between two neighboring insulating bodies.

According to another advantageous feature of the invention, the insulating body may have the shape of a spoke wheel comprising a central region in the form of a hub and an outer part in the form of a rim, these two parts being connected by shaped elements. of rays.

 There are resistors known as metal enamelled resistors which include ceramic substrates in dalumina ribbons on which is deposited by screen printing a paste for resistance in thick film which is dried at approximately 1500C and fired at approximately 8500C. These metal-enamelled resistance elements can be used very advantageously for the connecting elements in the form of a radius, one end face of the central part in the form of a hub forming the "inlet", the external part in the form of a rim constituting the "potential link" between the resistance elements and the other end face located on the side opposite to the previous one that can be used at the start.

 The star or wheel structure of the various resistance elements has significant advantages: it allows firstly to make a significant saving in weight and material and, moreover, the evacuation of heat from the active part is improved by a very strong convection and therefore this arrangement makes it possible to avoid thermal problems.

It is possible to provide each insulating body R on each of its sides with at least one surface perpendicular to the axis to establish contact between the different insulating bodies with each other, the facing surfaces coming into contact during the juxtaposition of two insulating bodies and a galvanic contact of the various resistances thus being established in a place of contact. This arrangement is advantageous when the contact of two insulating bodies takes place in the middle or at the periphery. This electrical contact between two neighboring resistance elements can be established in this case without any other specific additional arrangement.

It is also possible to connect two resistance elements by mounting between them a metal sleeve which, on the one hand, forms a spacer for these two elements and, on the other hand, ensures the connection, that is to say the electrical contact.

 When the insulating bodies used are in the form of a plate, the resistance material can be deposited on the side surfaces of the insulating body so as to save space, this material being able to be deposited on the side surfaces of the insulating body in a spiral shape. shelves or slots. The material for resistance can advantageously be deposited on the two lateral surfaces of the insulating body so that the tracks of material located on a lateral surface are parallel and possibly in opposite directions to those of the other surface. This arrangement creates a weak induction, because the direction of the current on one side of the insulating body is the opposite of that which flows on the other side, so that the magnetic fields compensate globally at least partially. further favor this factor by arranging the tracks of the material for resistance on one side of the substrate so that the current flows there in opposite directions. It is also possible to deposit the material for resistance of the tracks on the insulating bodies so that the different tracks are electrically connected at least partially in parallel.

This arrangement can also relate to the structure of the insulating body in the form of a rim wheel. The resistance material used can advantageously be of the cord type; a cord of this kind consists of a metallic wire wound on a core of fibers of insulating material and it is commercially available. This resistance wire can be glued to the side surfaces of the insulating body or be deposited in grooves made in the side surfaces of each insulating body in which it is optionally fixed by means of a molded resin.

According to an advantageous embodiment, the resistance material used is of the type of a paste which is deposited in thick film; this paste consists of a finely distributed material for resistance, glass particles and organic substrates and additives; the dough dries after deposit at around 1300C, then is baked at 8500C.

Thus, the resistance material and the glass are sintered in the form of a hard resistance tape. This thick film resistance paste can also be replaced by a metal alloy which is deposited in the vapor phase and which forms the resistance material on the insulating body.

When the device of the invention is used in a high-voltage installation gas-insulated with SF6, the resistor located on the high-voltage potential side and the measurement resistor connected to ground are arranged inside a shield metallic. This arrangement of the voltage divider is practically independent of temperature, since the higher voltage resistance and the measurement resistance are exposed to the same temperatures inside the shield. For this reason, the other possibility of placing the measurement resistor outside the metal shield is not as advantageous, but under certain conditions, this arrangement may be more advantageous for construction reasons.

Capacitive control elements are mounted between the insulating bodies in order to capacitively control the various resistance elements after assembly; these control elements can be in the form of plates and have at their circumference shielding rings in the form of toroids. The capacitive control elements can also be shaped as cylinder heads; the toroidal shielding rings are then fixed on the free edge. Capacitive shielding is necessary for the following reason: during certain switching processes, it is possible that peaks of relatively high switching voltage may appear which can cause a disruptive discharge between the resistance elements situated on the side of the higher voltage. and metal shielding. Capacitive control elements can limit this phenomenon, which also prevents capacitive leakage currents from flowing.

The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which
- Figure 1 is an equivalent diagram of an embodiment of the invention in which the measurement resistor is arranged inside the shield
- Figure 2 is an equivalent diagram similar to that of Figure 1, but in which the measurement resistor is arranged outside the shield;
- Figure 3 is an axial section of a device according to the invention
- Figure 4 is an axial section of an alternative embodiment;
- Figures 5 to 11 are partial cross sections of different embodiments of the substrate;
- Figures 12 to 18 schematically show in plan different modes of arrangement of the material for resistance on the substrate
- Figure 19 is an elevation with partial section of a resistance element;
- Figure 20 is an axial section; and
- Figure 21 is a plan view.

Figure 1, as well as Figure 2, are equivalent diagrams of an assembly according to the invention. A metal shield 10 is at ground potential and has, at the right end, in the representation of the drawing, a flange 12 on which a cover 14 is fixed. A phase conductor 16, mounted inside the shield, is at the high voltage potential and connected to a first resistor 18 to which a second resistor 20 is electrically connected in series, the resistor 18 being that which is at the higher voltage and the resistor 20 being the measurement resistor; the expression "resistance to higher voltage" means that this resistance is connected by a terminal to the high voltage potential of the phase conductor. The measurement resistance 20 is connected to cover 14, which is at ground potential, by the terminal located on the other side of that which is connected to the resistor 18. A measurement conductor 22, connected between the two resistors 18 and 20, makes it possible to detect at the terminals of the measurement resistor 20 the voltage relative to the ground which reproduces the voltage to be measured between the phase conductor 16 and the ground potential, this voltage being connected to an electronic amplifier device of the type well known in this technique and which amplifies the measurement signal taken from the resistor 20 so that the The measuring device or the protection device 26 has the necessary input power. The conductor connecting the amplification device 24 and the earth carries the reference 28. The resistor 20 can of course also consist of several elements. The measurement conductor 22 passes through the cover 14 through a hole 30 while being insulated.

The resistors 18 and 20 are mounted so as to form a voltage divider, the measurement resistor 20 being inside the shield 10. This arrangement has the advantage that the resistor 20 is practically at the same temperature as the resistor 18 which is at the upper voltage, so that the division ratio which is determined by the two resistors is practically independent of the temperature.

 Figure 2 is an equivalent diagram of an alternative embodiment. The shield also carries the reference 10, the cover, the reference 14, the phase conductor, the reference 16, the resistance to the higher tension, the reference 18 and the measurement resistance, the reference 20, the free end of the latter being at ground potential. The resistance which is at the upper voltage is inside the screen 10 and the measurement resistor 20 is outside the screen. An input of the electronic amplification device 24 is connected between the measurement resistor 20 and the resistor 18 which is at the higher voltage, this connection being outside the shield 10, the other end of the amplifier being the mass. The assembly of FIG. 2 is in some cases simpler to carry out, but it has the disadvantage that the resistor 18 which is at the higher voltage can be at temperatures different from those of the measurement resistor 20 and the measurements can be distorted.

FIG. 3 represents a first embodiment of a device according to the invention according to a concrete embodiment. It includes the shield 10 as well as the cover 14 and the flange 12. This figure also represents the phase conductor 16. The resistor 18 which is at the higher voltage consists of several resistance elements 32 of an identical embodiment and mounted in series, the concrete structure of these elements being described below.

These resistance elements 32 include, like the element 34 forming the measurement resistance, a hole 36 which passes right through them and, after juxtaposition of these different elements 32 and 34, an insulating bar 38 is introduced into the holes 36 , this bar being able to have the form of a threaded rod comprising at one end a thread 40 and at the other, a hexagonal head 42. The phase conductor 16 comprises a tapped blind hole 44 into which the threaded part is screwed 40 of the insulating bar 38, the various resistance elements 32 being clamped against each other and against the phase conductor 16. Capacitive control elements 46 and 48 clamped between the various resistance elements (only between the three elements of resistance located on the left in Figure 3) have a cylinder head shape as shown in Figure 3.They include a bottom 52 and 54 which is transverse to the longitudinal axis of the device and which is clamped between the elements of resistance 32, as well as a cylindrical rim 56 and 58 which is perpendicular to their bottom and on the free edge of which is attached or fixed or toroidal shielding ring 60, 62. The bottom 54 is larger than the bottom 52, of so that the control element 48 partially envelops the control element 46.

These capacitive control elements practically avoid the distortion of the electric field and the stray capacitances which may appear under the effect of transient effects due to the voltage applied between the resistance elements 32 and the envelope 10 grounded and between the resistor 32 themselves, so that even under sudden switching or instantaneous voltages <at high frequencies), the voltage distribution on the various resistance elements is substantially equal to the voltage distribution at nominal frequency and therefore the effects local dielectric stresses are avoided. Furthermore, the division ratio is practically independent of the frequency within a determined range of the latter, when the capacitive control elements are optimally dimensioned. The resistance elements 32 shown in FIG. 3 have approximately the shape of discs .

 The resistance element 34 of FIG. 3 is advantageously made up of a measurement resistance. The structure of the measurement resistor which is comparable to the resistance elements 32 which are located on the side of the upper voltage ensures that this resistance 34 is exposed to the same thermal conditions as these resistance elements located on the side of the higher voltage, so that the division ratio is practically independent of temperature. The connections of the measurement cables to the measurement resistor 34 are not shown in FIG. 3.

FIG. 4 represents an alternative embodiment of the invention in which the various resistance elements are not in the form of discs, but in the form of plates, which will be described in more detail below.

This embodiment also includes the shield 10, the cover 14, the phase conductor 16 and the various resistance elements 32 and 34. The same references have been adopted to clearly show that the construction or the principle structure of the embodiment of Figure 4 is equal to that of Figure 3. The measuring resistor 34, which is shown in cross section, also has the central hole or passage 36 and Figure 4 also shows the insulating bar 38, which however does not include a hexagon head 32, but instead of this head, a thread 64 on which is screwed a nut 66, a washer 68 of insulating material being interposed between the nut 66 and the resistance element 34. control which are provided are not in the form of cylinder heads, as in the embodiment of Figure 3, but in the form of trays and they bear the reference 70; the shielding rings are arranged at the circumference, that is to say at the periphery of the plate-shaped control elements.

 It is understood that the control elements 70 in the form of plates represented by FIG. 4 can also be combined with the disc resistance elements 32 which are represented in FIG. 3. Likewise, the embodiment of the capacitive control elements 52 and 56 as well as 54 and 58 which is represented in FIG. 3 can also be combined with the resistance elements 32 and 34 in the form of plates which represents FIG. 4.

 The measurement conductor 22 is connected between the resistance element 32 which is on the right and the measurement resistance 34 and exits through the hole or passage 36 and through the hole 30; the amplification circuit 24 is not shown.

All the resistance elements, both the elementary resistances located on the side of the upper voltage and the measurement resistance, consist of bodies in the form of plates or discs of insulating material, for example molded resin or ceramic, a material for resistance being deposited on these bodies in a manner which will be described later. FIG. 5 represents a first embodiment of a substrate of this type which is in the form of a plate and comprises a planar external part 100 and an internal part 102 also planar, but whose thickness is greater than that of the part 100 The plate-shaped part 100 has grooves 104 which can go from the inside to the outside, for example in the form of a spiral, and which are intended to accommodate the material for resistance. The thicker part 102 is provided to provide a distance D between the parts 100 of two juxtaposed substrates, this distance being necessary to avoid disruptive discharges between two neighboring substrates supporting the material for resistance. The two end surfaces 106 and 108 of each body are coated with contact material in order to establish the electrical connection between the resistance elements.

FIG. 6 shows the embodiment of the discoid body in which the thickness of the disc decreases radially from the inside to the outside and the two end surfaces 111 and 112 of the thick part 114 are also coated with contact material.

 In the embodiment of FIG. 6, the section of the discs is advantageously adapted to the dielectric forces appearing on the one hand in the insulating body and on the other hand in the circuit followed by the gases between two neighboring insulating bodies supporting the material for resistance.

Furthermore, the gap reserved for the gases and widening radially outward between two neighboring insulating bodies promotes the evacuation of the dissipation heat released in the material for resistance.

 FIG. 7 illustrates another alternative embodiment in which the different substrates, which in the particular case bear the references 120 and 122, have a wheel shape comprising an inner part 124 in the form of a plate and a thicker outer periphery 126. The end surfaces 128 and 130 of the outer part of each substrate 120 and 122 are in contact in the particular case; the current flows from the phase conductor 16 through a metal intermediate piece 17 to the surface 130 of the substrate 120 and, next to the resistance material located on one side and connected by the central hole to the resistance material which is deposited on the other side.

 A free internal volume 134, in which the heat possibly released could accumulate, being formed between two substrates of the embodiment of FIG. 7, the external parts 126 must comprise channels 136 through which the hot air being internally rely can flow outward. FIG. 8 represents this embodiment in which a total of seven grooves 136 are produced above the central axis of symmetry which is horizontal. It is naturally also possible to produce the thick parts 126 in the manner shown in FIG. 9 and, in this case, three thick segments 138, 140 and 142 are sufficient, which are arranged in a star around the axis of symmetry of the plate.

In the embodiment of FIG. 10, the part or the sector having the greatest thickness is not found externally (see FIG. 5), but internally in the vicinity of the center and only so as to protrude on a lateral surface. This extra thickness, which bears the reference 144, came from molding with a substrate 146 in the form of a plate. The central hole also bears the reference 36 in order to clearly show that it corresponds to the hole 36 of the resistance element 34 in FIG. 4.

A similar overthickness situated on one side or projecting in one direction can also be provided in the arrangements of FIGS. 6 to 9.

 FIG. 11 represents an even simpler embodiment of two juxtaposed substrates 150 and 152.

These two substrates have the form of plates of constant thickness and held at a distance by a spacer sleeve 154 of electrically conductive material. The surface elements situated around the central hole 36 are coated on both sides 150 or 152 with electrically conductive material and against which the bracing sleeve is applied.

 The substrates of the embodiments of FIGS. 6 to 11 have the common characteristic that their juxtaposition on an insulating bar 38 according to FIGS. 3 and 4 makes it possible to produce a particularly simple electrical connection, established by the contact surfaces formed of coating of material. electrically conductive, with the capacitive control elements 52 and 56 and also 54 and 58 in FIG. 3 or 70 in FIG. 4.

 When the spacer sleeves 154 which are used have different lengths, it is possible to vary the distance and therefore the capacity between the two substrates 150 and 152. It is possible to obtain a capacitive control along the stack of substrates to form a resistor whose terminals are at the higher voltage and an outer resistor in the same way as with the control elements 46 and 48 of FIG. 3 or 70 of FIG. 4 when the distance between the substrates is adjusted specifically by the differences in length of the spacer sleeves or by several spacer sleeves of the same length which are mounted between the substrates. This capacitive control method is not limited to the substrates of FIG. 11. It can also be used when the substrates used are those of FIGS. 5 to 10.

 The preceding figures show different embodiments of the substrates. Figures 12 to 18 show the arrangement of the material for resistance.

 In the resistance element of FIG. 12, the resistance material is deposited in a spiral going from the inside to the outside and starting from the internal contact surfaces 112, 110 or 108 and 106 which are coated with conductive material of the 'electricity. It is also possible to deposit the material for resistance in radial slots (see Figure 13) or along spokes (see Figures 14 to 16). In the arrangement of FIG. 14, the material for resistance 164 is deposited in a zigzag shape from the center so as to form a total of six rays and, in the arrangement of FIG. 16, the material for resistance 166 is deposited in rectilinear rays. , while in the arrangement tion of Figure 15, it is deposited in radial slots (see Figure 13). In FIG. 15, the material for resistance bears the reference 168.

Another way of depositing the material for resistance is that represented by FIGS. 17 and 18. In the arrangement of FIG. 17, the material for resistance is in spiral slots. In the embodiment of FIG. 18, the material for resistance 181 can be deposited on the substrate partly in the form of radial rays and partly in circles, this material for resistance being partially electrically mounted in parallel.

The resistance material used can be a wire consisting of a cord around which is wound a thin metal wire, this kind of resistance cord being commercially available. The resistance cord can be glued to the smooth outer surface of the substrate or can be introduced into the grooves 104 and optionally be coated with molded resin.

 It is also possible to use, instead of a resistance cord, a thick film type resistance paste which is also commercially available.

The definition of a resistance paste is a material that consists of finely distributed resistance material, glass particles, organic substrates and additives. The dough is dried at around 1300C after deposition on the substrate, then it is baked at around 8500C, this material for resistance and the glass then being sintered giving a hard resistance tape. Another possibility of ~ depositing material for resistance on the substrates consists in depositing in the vapor phase a metal alloy on the insulating bodies or substrates; these vapor deposition methods on ceramics are well known.

When a paste for resistance in thick film is used, it is possible to simultaneously deposit the capacitive elements also on the material of the substrate in order to thus obtain a capacitive control as described above.

 The resistance tracks can be deposited on the different substrates so as to form a series connection "(see FIGS. 12, 13, 15 and 17). It is also possible to mount the various resistance wires in parallel (FIGS. 14, 16 and 18); in this case, they leave on one side of the substrate from the middle towards the outside to pass through the outside edge on the other lateral surface of the substrate and go inwards. provision for resistance tracks mounted in parallel on an assembly with tracks mounted in series lies in the fact that in the event of a track failure, for example by rupture, the tracks mounted in parallel can allow the voltage measurement to be continued. This repetition considerably increases the availability of the measuring device. In the event of one of several tracks connected in series failing, the measuring device breaks down. It is possible to increase the number of resistance tracks mounted in parallel for example by depositing circular tracks similar to those of FIG. 18 in addition to those of the arrangements of FIGS. 14 or 16.

In principle, it is sought to arrange the resistance tracks on one side so as to form paths in parallel so that the current flows in one direction along a path and backs up on the neighboring path.

An optimal arrangement in this sense is that in slots of FIGS. 13 and 15 and in particular that of FIG. 17.

When the resistance tracks are deposited on the two sides of a substrate, the tracks are deposited on one side in parallel and in opposite direction to those on the other side of the substrate. These two measurements make it possible to maintain the inductance of the assembly at a very low value. The advantage of the slot arrangement of FIGS. 13, 15 and 17 on the tracks juxtaposed on one side of the substrate relates to this particular point. The lower the inductance, the higher the frequency of the voltages that can be measured.

 It is important to deposit the material for resistance on the different plates or substrate elements so that the forming material intended to give the resistance a determined value is put to the corresponding thickness or correspondingly on the different substrates. The subdivision of the resistance located on the side of the higher tension into individual elements identically shaped and which can also have the same resistance value makes it possible to easily realize the resistance situated on the side of the higher tension so that it has the value desired or any resistance value by mounting several resistance elements one after the other according to each particular case. The voltage divider which can then be used for the measurement then consists of individual resistance elements forming a modular arrangement . The resistance elements mounted one after the other do not necessarily have to have the same diameter as in the representations in FIGS. 3 to 12. It is possible as a variant to obtain any resistance value with a constant number of elements in staggering the diameter of the elements or by depositing different amounts of resistance material on elements of the same diameter. However, in this case, the advantage of a modular assembly is more or less lost.

Figures 19 to 21 show yet another alternative embodiment.

FIG. 19 represents a resistance body 200 which is a metal-enamelled resistance and which consists of a ceramic substrate 201 formed from alumina strips and on which is deposited a resistance track 202 consisting of a resistance film paste thick.

Contact connections 203 are located at the ends of the ribbon body 201. The resistance track 202 is deposited on the substrate 201 by screen printing, it is dried at around 1500C, then baked at around 8500C. It is possible to obtain surface resistances from 10 ohms per square up to 10 megohms per square by varying the composition of the pastes in thick film. The resistance elements can optionally be protected by a coating.

Figure 20 shows in cross section the arrangement of Figure 19. This figure shows an inner part 204 in the form of a hub of insulating material which is surrounded by an outer part 205 in the form of a rim; between these two parts are the resistance bodies 200 of FIG. 19 which are arranged so that two of these bodies form practically a radius 206, one of the resistance bodies 200 being connected to, or deposited on, an end surface 207 and the other resistance body 200, on the opposite end face 207 ′ of the inner part in the form of a hub; the two ribbons approach each other and are brought into contact with one another in the outer part 205 in the form of a rim.

As shown in FIG. 21, conductive surfaces 208 which are on the end faces (only the end face 207 is visible) have protrusions 209 which cover the contact surfaces 203 of the resistance tapes. Corresponding protrusions 210 are also located on the outer part 205 in the form of a rim, so as to cover the opposite contact surfaces 203. Thus, the flow of current leaves from the internal part 204, passes through the resistors, that is, i.e. the resistance tracks 202 outwards to arrive in the rim-shaped part 205, then passes through the opposite resistances, that is to say the tracks 202 situated on the opposite side to return to the internal part 204.

 The outer part 205 forming a rim and consisting of a toroldal ring is intended for the mechanical stabilization of the star resistance and also ensures, as mentioned, the electrical connection between the external ends of the resistance bodies 200 arranged in a star, so creating a parallel arrangement of the various resistance elements; in other words: the current flows from the end face 207 by the parallel mounting of the resistance bodies 200 arranged in a star on one side of the resistance body to reach the toroldal ring 205 (or in the external part 205) and return by mounting the resistance elements in parallel on the other side of the body to reach the opposite end face 208.

 It is possible to achieve practically any desired resistance value by varying the number of resistance bodies 200 mounted in parallel as well as the specific surface resistance of the resistance paste in thick film or the dimensions of the resistance track 202.

Claims (34)

RESELL I CAT IONS 1. - Device for measuring high continuous voltages in high voltage distribution installations, in particular in high voltage distribution installations comprising a metal shielding and a gas insulation with SF6, device comprising at least two ohmic resistors connected in series between potential voltage and ground and forming an ohmic voltage divider, the resistor which is connected to ground being used as a measuring resistor, device characterized in that the resistor (18) located on the high voltage side and / or the measuring resistor ( 20) consist of resistance elements shaped in a substantially identical manner and which assemble in a modular assembly, a resistance element being formed of an insulating body forming a substrate for the resistance material and on the external surface of which the material is deposited for resistance. 2. - Device according to claim 1, characterized in that the insulating body is in the form of a plate on at least one surface from which the material for resistance is deposited.  3. - Device according to claim 2, characterized in that the insulating body in the form of a plate has a substantially constant thickness (100, 146) and comprises near its axis of symmetry an excess thickness (102, 144) which is projecting on at least one side and which serves to maintain the distances between two neighboring insulating bodies. 4. - Device according to claim 2, characterized in that the insulating body of substantially constant thickness (124) comprises at the periphery an overthickness (126) projecting on at least one side, this overthickness having grooves (136) oriented at least approximately radially to allow cooling (air circulation) between two neighboring insulating bodies.  5. - Device according to claim 1, characterized in that the insulating body is in the form of spokes (200) and comprises an inner part in the form of a hub (204) and an outer part in the form of a rim (205), these two parts being connected by spoke shaped connecting elements (200). 6. - Device according to claim 5, characterized in that the insulating body is made of ceramic, in particular alumina.  7. - Device according to one of claims 5 and 6, characterized in that it preferably comprises a total of six ray resistance elements, each of which is formed of two resistance bodies (201) on which the material for resistance ( 202) is filed.  8. - Device according to any one of claims 1 to 3, characterized in that each insulating body (32, 34) narrows towards the outside.  9. - Device according to claim 8, characterized in that the insulating body comprises in the vicinity of its axis of symmetry an extra thickness (114) projecting on at least one side and intended to maintain the distances between two neighboring insulating bodies. 10. - Device according to any one of the preceding claims, characterized in that each insulating body comprises on each side at least one surface which is perpendicular to the axis and the facing surfaces of two juxtaposed insulating bodies are in contact, a galvanic contact of the various resistance elements being established at a place of contact.  11. - Device according to claim- 10, characterized in that at least one -surface (108) located in the vicinity of the axis of symmetry of the insulating body is concentric with this axis.  12. - Device according to claim 10, characterized in that each insulating body comprises at least one surface at the periphery.  13. - Device according to any one of claims 2, 3 and 9 to 12, characterized in that two neighboring insulating bodies (150, 152) are kept at a distance by means of at least one metal sleeve (154) which is intended to establish the electrical connection of the resistance tracks of the two insulating bodies. 14. - Device according to any one of the preceding claims, characterized in that each insulating body is made of molded resin.  15. - Device according to any one of the preceding claims, characterized in that each insulating body is made of ceramic.  16. - Device according to any one of the preceding claims, characterized in that the material for resistance is deposited on the two lateral surfaces of the insulating body so that the material tracks located on a lateral surface are parallel to those of the other. 17. - Device according to claim 16, characterized in that the material tracks located on a lateral surface are oriented in the opposite direction to that of the tracks located on the other surface. 18. - Device according to one of claims 16 and 17, characterized in that the resistance tracks arranged on a lateral surface of the substrate are juxtaposed and parallel so that the current flows there in opposite directions 19. - Device according to any one of the preceding claims, characterized in that the resistance tracks are deposited on the substrate so as to be at least partly also electrically connected in parallel. 20. - Device according to one of claims 16 and 17, characterized in that the resistance material is arranged in a spiral (160) on the side surfaces of the insulating body.  21. - Device according to any one of claims 16, 17, 19, characterized in that the material for resistance is arranged in spokes (164, 166) on the two lateral surfaces of the insulating body so that the tracks of material one of the side surfaces are substantially parallel to those on the other side surface.  22. - Device according to any one of claims 16 to 19, characterized in that the resistance material is deposited in the form of slots (Figure 13, Figure 15, 168) on each side surface of the insulating body.  23. - Device according to claim 22, characterized in that the material for resistance is arranged in radial slots and / or in spiral.  24. - Device according to any one of the preceding claims, characterized in that the resistance material consists of a resistance wire which is bonded to each lateral surface of the insulating body. 25. - Device according to any one of claims 1 to 23, characterized in that the material for resistance shaped into wire is arranged in grooves (104) that each insulating body comprises on the lateral surfaces and is optionally fixed thereto by means of molded resin.  26. - Device according to any one of claims 1 to 23, characterized in that the material for resistance consists of a paste for resistance in thick film.  27. - Device according to any one of claims 1 to 23, characterized in that the material for resistance consists of a metal alloy deposited in the vapor phase on the insulating body.  28. - Device according to any one of claims 1 to 27 and used in high voltage installations, with metal shielding and with gas insulation by SF6, characterized in that the resistance located on the side of the high voltage potential (18) as well as the measurement resistor (20) connected to ground are arranged inside the metal shield (10, 12, 14).  29. - Device according to any one of claims 1 to 27, characterized in that the measurement resistor (20) is located outside the metal shield (1O, 12, 14).  30. - Device according to any one of the preceding claims, characterized in that each insulating body has a central hole (36) which passes right through it through which passes a bar (38) formed of a threaded rod of material insulator, a thread at the end of this rod screwing into a threaded hole (44) in the end surface of the conductor for which the AC voltage is to be measured, this threaded rod being intended to fix the insulating bodies against each other the others and against the extreme surface of the phase conductor (16). 31. - Device according to any one of the preceding claims, characterized in that capacitive control elements (46, 48, 70) are arranged between the various insulating bodies (32). 32. - Device according to any one of claims 1 to 31, characterized in that the capacitive control elements (70) are in the form of plates and comprise at the circumference a ring of toroidal shielding.  33. - Device according to any one of claims 1 to 31, characterized in that the capacitive control elements (46 and 48) are in the form of yokes on the free edge of which are fixed toroidal shielding rings (60, 62 ). 34. - Device according to any one of claims 1 to 31, characterized in that the capacitive control is constituted by capacitive elements formed of a thick film resistance film deposited on the insulating body.