Circuit breaker - disconnector- earthing switch device for a gasinsulated switchgear, for ring networks, of the RMU type, and associated switchgear

Abstract

A circuit breaker - disconnector - earthing switch device for a gas-insulated switchgear, for a ring distribution network, is described, wherein the gas-insulated switchgear comprises a tank with a first wall and a second wall, wherein the device comprises: a circuit breaker unit comprising a plurality of vacuum interrupters and a plurality of fixed line-isolating contacts, wherein, each fixed line-isolating contact is electrically connected to a respective vacuum interrupter; a disconnector unit comprising a shaft rotatable about its longitudinal rotation axis, a plurality of mobile contacts projecting from the rotatable shaft and a plurality of earth contacts; a first plate and a second plate arranged facing each other, wherein the first plate is configured to be fastened to the first wall and the second plate is configured to be fastened to the second wall; and a second tie-bar configured to support the earth contacts.

Description

TECHNICAL SECTOR

[0001] The present invention relates to the sector of electrical networks, in particular the sector of networks for distributing energy in three-phase systems.

[0002] More particularly, the present invention relates to a circuit breaker - disconnector - earthing switch device for a gas-insulated switchgear, for ring networks, of the RMU type, and an associated switchgear comprising one or more of such devices.PRIOR ART

[0003] As is known, usually electrical energy is generated at a low voltage. The voltage is then increased in order to transport it in cables which have a relatively small cross-section.

[0004] Typically, following transport at a high voltage, the energy is distributed in ring networks. The networks also comprise substations in which the voltage is lowered again from a high voltage to a medium voltage. The substations are also known by the abbreviation RMU (Ring Main Unit) and comprise one or more circuit breaker - disconnector - earthing switch devices.

[0005] Typically, the circuit breaker - disconnector - earthing switch devices in the RMUs perform the following functions: line disconnection (allowing a part of the network to be isolated for maintenance or repair work); protection against overloads and short circuits; switching (switching of the energy between different sections of the network); remote control and automation (many circuit breakers are remotely controllable and integrated in automation systems); earthing; and monitoring of network conditions

[0006] RMUs are therefore devices which are used in electrical energy distribution networks for managing the distribution of energy in a safe and efficient manner.

[0007] RMUs are commonly used in medium-voltage distribution networks and are installed in various contexts, such as urban, industrial or residential zones.

[0008] RMUs are designed to offer compact and modular solutions for energy distribution.

[0009] In order to remain compact, typically RMUs use pressurised insulating gases in order to physically reduce the isolating distances.

[0010] A circuit breaker - disconnector - earthing switch device is described, for example, in EP 4254458, in the name of the same Applicant.

[0011] EP 3716422 discloses an electrical switchgear inside a gas-insulated enclosure for electrical distribution networks.SUMMARY OF THE INVENTION

[0012] The Applicant has carefully examined existing RMUs and observed that the pressurized gas, typically at 0.5 relative bar, tends to deform the structure containing it. This deformation may lead to inefficient and unreliable operation of the circuit breaker and / or disconnector. Consequently, the circuit-breaking action may not occur as required or within the necessary time frame. Therefore, the Applicant has set the objective of developing RMUs that are more robust and less prone to deformation.

[0013] The Applicant has also noted that the known RMUs are somewhat bulky. The dimensions, as is known, negatively influence various factors, last but not least, the impact on the environment, for example in terms of the amount of material and volume occupied during transport. The Applicant has therefore defined the object of providing RMUs which are more compact in order to reduce the impact on the environment.

[0014] Moreover, the compactness also has an impact on the amount of gas to be used for insulation of the components: the greater the volume of the RMU, the greater the amount of gas which must be used for insulation.

[0015] These objects, together with others, are achieved by a circuit breaker - disconnector device according to the present invention in which the circuit breaker is arranged, in the form of a tie-bar, between two rigid plates, configured to be firmly fastened to the front wall and to the rear wall of a sealed container (tank). The two rigid plates, when they are fastened to the walls of the tank, make the structure extremely rigid and prevent deformations. Furthermore, the two rigid plates, when fastened to the walls of the tank, provide further protection in the case of an explosion caused by the generation of an arc inside the device. In the event of an internal arc, a person standing in front of the RMU would be better protected than in the case of the known switchgears.

[0016] According to a first aspect of the present invention, a circuit breaker - disconnector - earthing switch device for a gas-insulated switchgear, for a ring distribution network, is provided, wherein the gas-insulated switchgear comprises a tank with a first wall and a second wall, wherein the device comprises: a circuit breaker unit comprising a plurality of vacuum interrupters and a plurality of fixed line contacts used for disconnection, wherein, each fixed line contact is electrically connected to a respective vacuum interrupter; a disconnector unit comprising a shaft rotatable about its longitudinal rotation axis, a plurality of mobile contacts projecting from the rotatable shaft and a plurality of earth contacts; and a first plate and a second plate arranged facing each other, wherein the first plate is configured to be fastened to the first wall of the tank and the second plate is configured to be fastened to the second wall of the tank.

[0017] According to embodiments, the device further comprises a first tie-bar connected to the first plate and to the second plate for keeping the plates at a predetermined distance.

[0018] According to embodiments, the device further comprises a second tie-bar connected to the first plate and to the second plate for keeping the plates at a predetermined distance, wherein the second tie-bar is configured to support the earthing contacts.

[0019] According to embodiments, the first tie-bar supports, at least partially, a transmission mechanism for operating the vacuum interrupters.

[0020] According to embodiments, the first plate and the second plate are at least partially made of steel.

[0021] According to embodiments, the rotatable shaft of the disconnector unit is configured to assume: a first position in which each of the mobile contacts engages with a respective fixed contact of the circuit breaker unit; a second position in which the mobile contacts do not engage with fixed or earthing contacts; and a third position in which each of the mobile contacts engages with a respective earthing contact of the disconnector unit.

[0022] According to embodiments, the mechanism is configured to convert a linear motion into a rotational motion.

[0023] According to another aspect, the present invention provides a gas-insulated switchgear, for a ring energy distribution network, comprising a closed tank with a first wall and a second wall, and a circuit breaker - disconnector - earthing switching device of the type indicated above, wherein the first plate is fastened to the first wall of the tank and the second plate is fastened to the second wall of the tank.

[0024] According to embodiments, the first plate is fastened to the front wall of the tank and the second plate is fastened to the rear wall of the tank.

[0025] According to embodiments, the first plate is bolted to the front wall of the tank and the second plate is bolted to the rear wall of the tank.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] A detailed description of the present invention now follows, being provided purely by way of a non-limiting example, to be read with reference to attached figures in which: Fig. 1 is an axonometric front left view of a circuit breaker - disconnector - earthing switch device for a gas-insulated switchgear, for ring networks, according to an embodiment of the present invention; Fig. 2 is axonometric rear view of the circuit breaker - disconnector - earthing switch device according to Fig. 1; Fig. 3 is an axonometric front right view of the circuit breaker - disconnector - earthing switch device according to Fig. 1; Fig. 4 is a cross-sectional view of the circuit breaker - disconnector - earthing switch device according to Fig. 1; Fig. 5 is a side view, with front on the right, rear on the left, of the circuit breaker - disconnector - earthing switch device according to the invention with the mobile contacts of the disconnector in the opening position; Figs. 6a, 6b, 6c and 6d are side views (front on the left, rear on the right) of the device according to Fig.1 in which some parts have been removed in order to make visible the interrupter devices (vacuum interrupters) and the (kinematic) mechanism for opening / closing the contacts of the interrupter devices; Figs. 7a, 7b, 7c and 7d are various views of the frame with plates, without the circuit breaker unit and the disconnector unit, of the device according to Fig. 1; Fig. 8 is a partial side view of a portion of the gas-insulated switchgears, in which the circuit breaker - disconnector - earthing switch, the copper connection thereof to the insulators, the section of the gas-insulated housing and an insulator, are visible; and Fig. 9 is a rear view of gas-insulated switchgear according to an embodiment of the invention closed by a rear cover, wherein a rear and side part of the tank has been removed to show the inside. DETAILED DESCRIPTION

[0027] With reference initially to Fig. 1 and Fig. 2, the circuit breaker - disconnector - earthing switch device according to an embodiment of the present invention will be described. For simpler illustration, the circuit breaker - disconnector - earthing switch device will also be referred to below by the term "device" and will be indicated by the reference number 1.

[0028] The expressions "rear" and "front", when used with reference to the device 1, are to be understood as referring to the container (tank) T inside which the device 1 is inserted. Therefore, the front part of the device 1 is the part which (as will become clear from the present description) will be fastened to the front wall T-F of the tank. Similarly, the rear part of the device 1 is the part which will be fastened to the rear wall T-R of the tank T. The front and rear walls of the tank are shown in Figures 8 and 9.

[0029] The device 1 is configured to be inserted inside a tank T or container where, for each phase, a busbar typically made of copper or aluminium is present. Obviously, several devices 1 may be housed inside the same tank.

[0030] The device 1 comprises a circuit breaker unit 2, a disconnector unit 3 and a frame 4 with a pair of plates 41, 42. The circuit breaker unit 2 is configured to break the nominal current and the fault current (or short-circuit) and optionally to perform the so-called making function, i.e. to make the short-circuit current. As will become clear from the description below and the drawings, the circuit breaker unit 2 and the disconnector unit 3 have different operating mechanisms.

[0031] The circuit breaker unit 2 comprises circuit-breaking devices, also called "bottles" (or vacuum interrupters) 21, a transmission mechanism 22 and a bottle-support structure 23, all firmly assembled on a frame 4 which forms a monobloc structure. The bottle-support structure may comprise two substantially flat plates which may be made, advantageously, of an insulating material.

[0032] The monobloc structure is delimited by a pair of plates 41, 42.

[0033] The transmission 22 is designed to transfer the movement from a first bar 221 to the bottles 21.

[0034] The bottle-support structure 23 is configured to support the bottles 21 in the correct position.

[0035] The device 1 also comprises a disconnector unit 3 for increasing the safety level. The disconnector unit 3 has preferably three positions and comprises a line insulator and an earthing switch.

[0036] The line switch function is substantially integrated in the circuit breaker unit 2.

[0037] The earthing switch is provided downstream of the circuit breaker unit 2 and has the function of earthing the cables, maintaining the insulation and if necessary, making the short-circuit current.

[0038] According to one embodiment of the present invention, the disconnector unit 3 comprises a rotatable hinged shaft 31. The mechanism of the disconnector unit 3 is different from / independent of that of circuit breaker unit. Essentially, the movement of the disconnector unit 3 is based on a rotational movement of the shaft 31.

[0039] The shaft 31 may be advantageously made of an electrically insulating material. Mobile contacts 311, which are typically made of copper and preferably C-shaped, are mounted on the shaft 31. The shaft 31, rotating, is able to set the disconnector 3 (and therefore the mobile contacts 311 mounted thereon) to three positions: (i) a first position which corresponds to the line insulator closed and the earthing switch open, (ii) a second position which corresponds to the line insulator open and earthing switch open, and (iii) a third position which corresponds to the line insulator open and the earthing switch closed. According to one embodiment of the present invention, the front of the RMU is provided with symbols which indicate the state of the two line switch and earthing switch devices in each of the three positions so as to clearly indicate to the operator the condition of the line switch and earthing switch.

[0040] With reference to Figures 1 and 2, the disconnector 3 is in the second position (ii). In this position, the three mobile contacts 311 on the shaft 31 are spaced from the three terminals 211 projecting from the circuit breaker unit 2 and connected to the bottom (inner) ends of the three bottles 21. Therefore, the three mobile contacts 311 on the shaft are not in electrical contact with the three terminals 211 projecting from the circuit breaker unit 2. The circuit is therefore open and the energy cannot flow. The terminals 211 will also be indicated below and / or in the claims by the expression "fixed contacts".

[0041] When the shaft 31 is rotated in the clockwise direction (looking at Fig. 1), the copper mobile contacts 311 on the shaft 31 engage with the terminals 211 projecting from the circuit breaker unit 2 and the disconnector is therefore in the first position. In the closed position, the circuit is closed and the energy is free to flow within the circuit. The movement described may also be easily understood from Fig. 4. In Fig. 4 the disconnector is in the second position but, when the shaft is rotated clockwise, the disconnector 3 assumes the first position.

[0042] If the shaft 31 were instead to be rotated in an anti-clockwise direction (looking at Fig. 1), the three copper mobile contacts 311 on the shaft 31 would engage with the three earthing terminals (or contacts) 312 and the disconnector would therefore be in the third position. In the earthed position, the cables are set to earth potential. This movement may also be easily understood from Fig. 4. When the shaft is rotated in an anti-clockwise direction, the disconnector 3 assumes the third position.

[0043] As mentioned above, operation of the disconnector unit is also shown in and may be easily understood from Fig. 4 which is a cross-section through a plane of symmetry of a bottle 21. The rear plate 42 mentioned above is also visible. Obviously, for the purposes of the description below, substantially the same image would be obtained by cross-sectioning any of the three bottles 21.

[0044] The inside of the bottle 21 is not shown in detail since it is not of importance for the purposes of the present invention. The inner (or bottom) end 213 of the bottle 21 is any case visible and is electrically connected to the terminal 211 projecting from the circuit breaker unit 2. The figure also shows the shaft 31 of the disconnector unit 3, with the associated mobile contacts 311 projecting therefrom. A double-arrow curved line indicates the possibility of rotating the shaft: upwards in order to engage with the terminals projecting from the circuit breaker unit (position (i)) or downwards in order to engage with the terminals of the earthing switch (position (iii)).

[0045] Advantageously, as can be seen in Fig. 4, in order to avoid the risk of triggering internal arcs and improve insulation, the surfaces of many components are rounded. In particular, the terminals 311 projecting from the shaft 31 of the disconnector unit 3 are rounded. Furthermore, each of the earth terminals 312 comprises a cylindrical body with a circular cross-section having a rounded free end, substantially without corner edges. The three terminals 211 projecting from the three bottles 21 of the circuit breaker unit 2 may have substantially the same form as the earth terminals 312.

[0046] Figures 6a, 6b, 6c and 6d show the mechanism 22 which converts a substantially linear motion into a rotational motion for opening / closing the contacts in the bottles 21. Figures 6a and 6b show the condition in which the switch is open, while Figures 6c and 6d show the condition in which the switch is closed.

[0047] The mechanism 22 comprises the first bar 221, projecting from the front plate 41, and a pair of bars arranged parallel to one another. The mechanism 22 also comprises, for each bottle 21, a pair of substantially triangular plates 222 (with rounded corners) pivotably mounted with the bars 223. In turn, each of the substantially triangular plates 222 is pivotably mounted at the bottom at a pivot point situated at a vertex. A translation movement of the first bar 221 causes the rotation of the substantially triangular plates 222 about the respective pivot point 224.

[0048] According to the embodiment shown, the disconnector unit 3 not only is integrated in the structure of the circuit breaker unit 2, but also has some common components. In this way, the design is not only more robust, but it is also simplified, without however affecting its reliability and / or sturdiness.

[0049] Figures 7a, 7b, 7c and 7d are four views of the frame 4 with plates 41, 42, without the circuit breaker unit and the disconnector unit, of the device according to the invention.

[0050] In the embodiment shown, the frame 4 comprises a first tie-bar 43, a second tie-bar 44, a third tie-bar 45 and a pair of plates 41, 42. The ends of the three tie-bars 43, 44 and 45 are fastened to the plates.

[0051] The first tie-bar 43 of the frame 4 preferably comprises a C-shaped metal profile (for example made of steel) which is open at the top. The substantially triangular plates 222 of the mechanism 22 are pivotably mounted on the walls of the C-shaped metal profile. The walls of the C-shaped metal profile may comprise other holes for fixing other components of the device 1 or for lightening the structure.

[0052] The second tie-bar 44 of the frame is arranged in a bottom corner of the plates. The second tie-bar 44 is configured to support the earthing terminals 312 of the disconnector unit 3. According to embodiments, the second tie-bar 44 is a solid, metal, C-shaped profile with thick walls. Preferably, the bottom of the C of the second tie-bar 44 is inclined with respect to the edges of the plates 41 and 42.

[0053] The third tie-bar 45 is preferably arranged in the top corners of the plates 41, 42, opposite the corners where the second tie-bar 44 is fastened.

[0054] Each plate 41, 42 has preferably the form of a quadrilateral, which is for example substantially square or rectangular. Each plate preferably comprises holes for fastening the plate to a wall of the tank T and / or for supporting parts of the circuit breaker unit and the disconnector unit. Preferably, the front plate 41 comprises a hole for the bar 221 of the mechanism 22 and a hole for a device for rotating the shaft of the disconnector unit with the mobile contacts.

[0055] Each plate 41, 42 is preferably made of metallic material, such as steel.

[0056] As mentioned above, the device 1 according to the present invention is configured to be inserted in a tank T for forming, together with other components, a gas-insulated switchgear for ring networks, of the RMU type. According to the present invention, the device 1 is inserted inside the tank T so that the plates 41, 42 are rigidly fixed to a metal structure, typically made of stainless steel, which forms the housing of the tank T inside which the device 1 and all the energy transporting components are contained.

[0057] The frame, comprising plates and tie-bars, ensure that the tank T is not deformed also following the introduction of the pressurised insulating gas.

[0058] The front (T-F) and the rear (T-R) of the metal tank are therefore fastened to the plates 41, 42 which are in turn rigidly fixed to the tie-bars.

[0059] The rigidity of the device and the tank inside which it is inserted (typically together with other components and one or more devices) is extremely advantageous, for example for maintaining the - necessarily very precise - adjustments of the interruption members (bottles). As is known, in fact, one of the main difficulties encountered in the design of RMUs is that of ensuring that the deformations do not affect the adjustments carried out beforehand on the interrupter, before it is assembled inside the tank and on a special template.

[0060] The vacuum bottle interrupters, in fact, before being installed inside the RMUs, require adjustment.

[0061] The purpose of these adjustments is to ensure that all the vital parameters of the interrupter lie within predetermined ranges.

[0062] These parameters are typically the speed at which the bottles break or make (close) the circuit, the distance between the fixed and mobile contacts of the bottles, the travel movement of the contacts, etc.

[0063] Typically, the initial adjustment is performed in a special "in air" template, i.e. with the interrupter not inside the RMU.

[0064] Once the interrupter has been adjusted, it is assembled inside the RMU.

[0065] The tank is then welded at the rear. Fig. 8 shows the tank T closed in a sealed manner with a rear cover.

[0066] Once the tank T has been sealed, the pressurised gas is blown inside it.

[0067] The pressure of the gas causes deformations which, if not controlled, may alter the adjustments carried on the interrupter in the "free air" template.

[0068] As a result of the innovative design of the device 1 according to the present invention, the deformations may be limited, as described above.

[0069] Furthermore, since the entire circuit breaker unit is contained inside a "monobloc", it is practically non deformable.

[0070] This ensures that a perfect "continuity" of the adjustments made before and after filling of the tank with the insulating gas may be maintained.

[0071] The above, in addition to being a guarantee as to the reliability of the interrupter, avoids the problem of later adjustments - moreover practically impossible - of the interrupter following the pressurisation of the tank.

[0072] In other words, if it were necessary - following deformations to adjust again the interrupter, it would be necessary to remove the weld of the tank.

[0073] According to preferred embodiments all (or most of) the details with which the structure of the interrupter is produced by means of moulding.

[0074] The relative distances between the fixing holes for operation / assembly of the interrupter with the structure are therefore fixed and extremely repetitive distances.

[0075] This means that there is practically zero waste due to non-compliance of the dimensions.

[0076] This also means that there is a high degree of repeatability of the performance of the interrupters.

[0077] An indirect advantage is also the rapid adjustment time, mentioned above, since the interrupter structures are repetitive from the point of view of the dimensions.

[0078] This also results in a reduction in the TAC time (total accumulated cycle time) with a reduction in the cost of the product, without affecting the reliability thereof.

[0079] The compact structure and the two plates 41, 42, in addition to strengthening the tank, protect it from any burn-through phenomena which may occur in the event of an "internal arc".

[0080] As is known an internal arc typically occurs when the electric current (and the correlated energy) follows a path through an insulating medium, instead of along the conductors provided.

[0081] This may happen for various reasons (faults, assembly defects, anomalous service conditions, etc.).

[0082] Internal arcs are dangerous because they cause damage to the electrical equipment, interrupt the power supply and represent a safety risk for persons who are in the vicinity.

[0083] Burn-through consists of a perforation, made by the arc, through one or more parts of the metal housing which forms the tank.

[0084] Should a burn-through occur, there is an outflow of plasma (temperature of the order of thousands of degrees Kelvin) from inside the tank to the outside.

[0085] In the unfortunate case where an operator is situated in the vicinity of an RMU and an internal arc with burn-through occurs, the safety of the operator could be compromised.

[0086] Owing to the structure of the device 1, as described above, it has been possible to carry out and pass the severest internal arc tests at a certified CESI laboratory.

[0087] The structure of the interrupter in fact allows the arc to be "contained" inside a predefined volume preventing it from moving towards the walls of the tank.

[0088] The aim of these tests was to show that, in the event of an arc, the safety of an operator would not be compromised and that there was no risk of burn-through.

[0089] The tests were carried at 24 kA, 21 kA for a duration of one second both at 50 Hz and 60 Hz. Access at the front and the sides was guaranteed and there was no burn-through at the rear of the tank.

[0090] These performance results hitherto had been achieved only with top-of-the-range products.

[0091] The accessibility of the RMUs tested on fours sides (AFLR) was therefore guaranteed.

Claims

1. A circuit breaker - disconnector - earthing switch device (1) for a gas-insulated switchgear (R) for a ring distribution network, wherein the gas-insulated switchgear (R) comprises a tank (T) with a first wall (T-F) and a second wall (T-R), wherein the device (1) comprises: a circuit breaker unit (2) comprising a plurality of vacuum interrupters (21) and a plurality of fixed line contacts (211), wherein each fixed line contact (211) is electrically connected (213) to a respective vacuum interrupter (21); a disconnector unit (3) comprising a shaft (31) rotatable around its longitudinal rotation axis (313), a plurality of mobile contacts (311) projecting from the rotatable shaft (31) and a plurality of earthing contacts (312); and a first plate (41) and a second plate (42) arranged facing each other, wherein the first plate (41) is configured to be fastened to the first wall (T-F) of the tank (T) and the second plate (42) is configured to be fastened to the second wall (T-R) of the tank (T); and a second tie-bar connected to the first plate (41) and to the second plate (42) for keeping the plates (41, 42) at a predetermined distance, wherein the second tie-bar is configured to support the earth contacts (312).

2. The device (1) of claim 1, further comprising a first tie-bar connected to the first plate (41) and to the second plate (42) for keeping the plates (41, 42) at a predetermined distance.

3. The device (1) of claim 2, wherein the first tie-bar supports, at least partially, a transmission mechanism (22) for operating the vacuum interrupters (21).

4. The device (1) according to any of the preceding claims, wherein the first and second plates (41, 42) are at least partially made of steel.

5. The device (1) of claim 1 or claim 2, wherein the rotatable shaft (31) of the disconnector unit (3) is configured to assume: a first position in which each of the mobile contacts (311) engages with a respective fixed contact (211) of the circuit breaker unit (2); a second position in which the mobile contacts (311) do not engage with fixed contacts (211) or earth contacts (312); and a third position in which each of the mobile contacts (311) engages with a respective earth contact (312) of the disconnector unit (3).

6. The device (1) of claim 3, wherein the mechanism (22) is configured to convert a linear motion into a rotational motion.

7. A gas-insulated switchgear (R), for a ring energy distribution network comprising a closed tank (T) with a first wall (T-F) and a second wall (T-R), and a circuit breaker - disconnector - earthing switch device (1) according to claim 1, wherein the first plate (41) is fastened to the first wall (T-F) of the tank (T) and the second plate (42) is fastened to the second wall (T-R) of the tank (T).

8. The switchgear (R) of claim 7, wherein the first plate (41) is fastened to the front wall (T-F) of the tank (T) and the second plate (42) is fastened to the rear wall (T-R) of the tank (T).

9. The switchgear (R) of claim 8, wherein the first plate (41) is bolted to the front wall (T-F) of the tank (T) and the second plate (42) is bolted to the rear wall of the tank (T).

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