ENCAPSULATED MEDIUM-VOLTAGE DISTRIBUTION SYSTEM

Abstract: Encapsulated medium-voltage distribution system which comprises one or more sections. The sections are composed of a number of compartment modules, which comprise a first busbar subsystem, a second busbar subsystem and a switching subsystem and a disconnector subsystem for connecting or disconnecting the first busbar subsystem and/or the second busbar subsystem to and from an external connection subsystem. Each subsystem is in each case accomodated in a separate compartment module, which is in each case separated from the remaining compartment modules physically and in touchproof way.

Description: Encapsulated medium- voltage distribution system The invention relates to an encapsulated medium-voltage distribution system, comprising one or more sections which are composed of a number of compartment modules, which comprise a first busbar subsystem, a second busbar subsystem a switching subsystem, and a disconnector subsystem for connecting or disconnecting the first busbar subsystem and/or the second busbar subsystem to and from an external connection subsystem. A system of this type is known from EP 0 428 220. This document describes a single- busbar system and a double-busbar system. The more expensive double-busbar system is used instead of a single-busbar system where the system management and availability are of particular importance. It is then possible for the load in the system to be distributed, so that the short-circuit current can be limited. In addition, this offers the possibility of connecting network elements and of using two independent voltage control systems. Another important advantage of a double-busbar system is that it enables the availability to be improved. This means in particular that at least one busbar system remains available in the event of a fault in the system. Furthermore, it is also possible to add to the distribution system without the entire system having to be deactivated. From DE 39 27 835 a medium- voltage distribution system is known provided with a first and a second busbar subsystem, by which the need to achieve an as great as possible availability of a double busbar system is met to a great extent. Therefore, the system comprises two power switches which could be ridden out and can connect either the first busbar subsystem or the second busbar subsystem or both busbar subsystems to an external connection subsystem. The use of power switches which could be ridden out has however the great disadvantage with respect to fixed arranged switches in that the system is less compact and less more space consuming. Moreover, with power switches which could be ridden out additional locking means must be provided in order to prevent undesired switching conditions. These additional locking means enlarge however also a change of disturbances and have thereby an adverse effect on the reliability of the system. A further disadvantage with respect to fixed arranged switches is that also the costs are higher. In a system known from EP 428.220 the above mentioned disadvantages are not valid because fixed arranged switches are used. The system disclosed in EP 428.220 offers additionally yet a further cost price advantage because only one power switch is used. Indeed, the system also comprises to disconnectors but the total costs of a fixed arranged power switch provided with two disconnectors will be lower than the costs of two power switches which could be ridden out, with the associated carriage, ride-in contacts and locking means. A disadvantage of a system known from EP 428.220 is however, that in practice it is not possible that, in the event of a fault in the system, sufficient use is made of the advantage of the availability which double-busbar systems potentially offer, such as is the case in the system of DE 39 27 835. Because in the system according to EP 428.220 the disconnectors are accommodated in the busbar compartment, also the respective disconnector will be effected adversely when a fault occurs in one of the busbar compartments, in which soot and so on occurs and for example the respective disconnector could provide a short circuit within the phases. Because the disconnectors are connected to each other electrically with the side by which they are also connected to the power switch, this means that also the other busbar compartment will encounter a phase short circuit through the respective disconnector, when the disconnector has been or is closed. Consequently, the problem must be removed before a supply from the connection subsystem could take place through that other busbar compartment. This means in practice that there is not a complete redundancy which implies that the availability is diminished considerable. Because in the system types as disclosed in EP 428.220, the busbar system is not divided in compartments per section, but extents over several sections of the system this means that also the availability of all respective sections are thus influenced adversely. In order to achieve yet the same redundancy as in DE 39 27 835, in which the ride-in contacts also operates as disconnectors and thus in DE 39 27 835 it is spoken of four disconnectors, one could also add two disconnectors in the system of EP 428.220. However, this means that the system needs not only more space and is thus less compact, but that also the cost price is higher. It is an object of the invention to provide a medium- voltage distribution system of the type described in the preamble in which with maintaining the advantages, the complete redundancy is provided and in which the problems described above are avoided. According to the invention, this object is achieved by the fact that each subsystem is in each case accommodated in a separate compartment module, which is in each case separated from the remaining compartment modules physically and in a touchproof way. As a result, the consequences of a fault remain restricted to the relevant area, so that only the subsystem in the relevant compartment fails. The other functions remain fully available. Preferably the disconnector subsystem is subdivided in two subsystems each in an apart separated compartment module. It is observed further that if the ride-in contacts of DE 39 27 835 are considered disconnectors, these disconnectors are not groupped in own compartments, but in three different compartments. If now a fault arises in the one busbar system, the respective disconnector will be infected adversely. When that disconnector is switched out, the outer disconnector could be switched in subsequently without any problems and the connecting subsystem is supplied through the other busbar system. Under certain circumstances, a fault may lead to an explosion. To keep the explosion under control, the compartment modules are provided with wall parts which are weaker than the remaining wall parts thereof to such an extent that the pressure can be dissipated through them, thus preventing heavy damage to an entire medium- voltage distribution system. Moreover, the mechanical strength of the remaining wall parts can remain limited, which is cost-effective. Preferably, the outer surface of the weaker wall part of the compartment modules of the switching subsystem, the disconnector subsystem and the external connection subsystem faces downwards or upwards. In this case, the surface of the weaker wall part of the compartment module of the first and second busbar subsystems is preferably perpendicular to the busbar direction. The abovementioned orientation of the wall parts ensures that, as a result of an excessively high pressure within a compartment module, the gases which escape through the weaker wall parts do not have an adverse effect on the operation of the subsystems in the remaining compartment modules. A medium-voltage distribution system is known from US 5 892 195, in which the different components of the installation are accommodated in separate compartments and in which measures are provided in order to limit the adversed effects from a fault by which pressure and gases occur. The solution indicated in said publication is in particular the creation of a separate compartment by which pressure and gases can be dissipated. By using such a separate and additional compartment for the discharge of pressure and gases the system will consume more space. Also in DE 39 27 835 such a solution is disclosed for the discharge of pressure and gases, which solution is also constituted by an additional compartment for discharging pressure and gases. This solution demands also more space. In the system of the present invention the compact construction is maintained because an additional and separate compartment is not used for discharging pressure and gases. According to the invention said discharge is carried out in a way of influencing other functions to minimal extent. To further ensure the availability of the medium-voltage distribution system, it is important that the drive mechanism which is used for the switching means should be sufficiently reliable for switching to be possible in any situation in the event of a fault. In addition, for the safety of the operators, it is important for there to be a reliable indication of the position which the switch is in. For this purpose, the medium-voltage distribution system is characterized in that the drive mechanism comprises at least one drive loop, which is tensioned over a drive roller, and at least one rotatably mounted roller with, in between, a straight drive loop section, to a coupling point of which the switching means are coupled, the distance between the centre axes of the rollers and the position of the coupling point being matched to one another in such a manner that, when the drive roller is driven between its limit positions, the distance which is covered by the coupling point corresponds to the travel which is required in order to move the switching means which are to be driven from one position into the other position. To prevent slipping between drive loop and drive roller, the drive loop is an internally toothed drive belt, and the drive roller has external toothing which meshes with the internal toothing. An accurate and more robust embodiment is achieved by the fact that the drive loop is a chain and the drive roller is formed by a sprocket wheel which meshes in the link openings of the chain. The drive roller, the toothed drive roller or the sprocket wheel is/are preferably driven by an electric motor with a reversible direction of rotation. For safety reasons, the drive loop is provided with a position indicator. Furthermore, in one embodiment of the invention, the electric motor is provided with a blocking device which, in the absence of a control voltage, blocks the electric motor. This prevents the possibility, under certain circumstances (for example in the event of a continuous short-circuit current), of an unintended switching movement taking place. For safety reasons, the block is designed in such a manner that it can be overriden by hand, so that the drive mechanism can be operated manually even in the event of a fault. The drive mechanism according to the invention has the property that both hands are required in order to override the block and to actuate the drive mechanism. This prevents accidental use. In an embodiment which is preferably to be used, there are two parallel drive loops with associated rollers. The invention will be explained in more detail below with reference to the drawings, in which: Fig. 1 shows a circuit diagram of a medium- voltage distribution system; Fig. 2 shows an embodiment of the medium- voltage distribution system according to the invention which is preferably to be employed; and Fig. 3 shows a preferred embodiment of a drive mechanism for a medium-voltage distribution system. A medium-voltage distribution system generally comprises, as subsystems, a cable connection, circuit-breaker, earthing device, disconnector and busbar system. These components are accommodated in a space which is encapsulated, the encapsulation preferably being made of metal. According to current international standards, medium- voltage distribution systems, with regard to the enclosure of the components, can be divided into: a. Cubicle systems. The encapsulation is made from metal and is also explosion- proof. All components of the medium-voltage distribution system are accommodated in a metal-encapsulated space. Gas can flow between all the sections (cable connection, busbar system, switch, disconnector, etc.), and they are not separated from one another such that there can be no contact between them. This system therefore has the drawback that the installation cannot safely be added to during operation. Furthermore, there is no redundancy following an internal fault. In fact, the entire system will be damaged after an internal fault. b. Compartmentized systems. In terms of the encapsulation, these systems correspond to a cubicle system, but the space in which the functions are to be accommodated are divided into separate compartments, in order to ensure that there is no contact with them. These compartments may be separated from one another by plastic or metal encapsulation or a combination thereof. The internal area or areas of the systems referred to under a. and b. may be filled with an insulating gas SF6. If SF6 is used, the compartments of the system from category b. not only have to be touchproof but also must be designed so as to be gastight with respect to one another. Furthermore, the encapsulated medium-voltage distribution systems from category a. have to be designed in such a manner that, in the event of a fault occurring in the metal- encapsulated area, this must not cause any danger to any operating staff. This means that a cubicle system has to be able to mechanically withstand such an event. The consequences of the fault, such as soot contamination etc., however, will spread throughout the entire area, making the entire system totally unusable, so that it has to be completely reconstructed or replaced. It is true that a system with compartments from category b. which is filled with SF6 is of gastight design, but this gastightness is not such that it prevents the spread of soot contamination and the like. If such contamination to the system occurs as a result of a fault, although it complies with the standard, the system is not intrinsically safe. To satisfy the desired requirement of optimum availability, the compartments must be explosion-proof with respect to adjoining compartments. Medium-voltage distribution systems may be designed with a single-busbar system or a double-busbar system. Although the double-busbar system is more expensive, it has a number of advantages with regard to availability and system management. The improved availability has two aspects. Firstly, there is redundancy in the event of an internal fault. After an internal fault (spontaneous or caused by a malfunction) at any location in the installation, the installation can be returned to operation within a very short time (known as the reconnection time). Then, the installation can be deactivated ■ . at a scheduled time (known as the repair time) in order to repair the damage. The second aspect is the ability to add items while live. Any addition to the medium- voltage distribution system will be able to take place in a touchproof manner while the installation continues to operate. A double-busbar system is also of importance for system management. A double-busbar system enables network elements to be connected and disconnected. This allows, for example, insular operation. Furthermore, the distribution system of the double-busbar type makes it possible to obtain improved distribution of the load while limiting the short-circuit current. Fig. 1 shows a circuit diagram of an example of a medium- voltage distribution system. This is a distribution system with two busbar systems. The busbar systems Rl and R2 are connected, via disconnectors SI and S2, to one pole of the circuit-breaker VS, the other pole of which is connected to the cable connection KA. In addition, an earthing device A is also shown. The figures clearly show the redundancy, i.e. the fact that the other busbar system is still available in the event of a fault in one busbar system Rl or R2. In the event of a fault, for example a short-circuit, in the busbar system Rl, the circuit- breaker VS will switch off. The disconnector SI can then be used to decouple the busbar system Rl, after which the circuit-breaker VS can be switched on again. As a result, the busbar system R2 is once again fully available. A medium- voltage distribution system generally comprises one or more sections. A system of this type is described, for example, in European Patent EP 0 428 220 Bl. Each section is composed of a number of compartment modules, each containing one or more subsystems. By way of example, in each case one busbar subsystem and one disconnector subsystem are accommodated in one of the compartment modules, for example a first busbar subsystem and a first disconnector system are accommodated in one compartment module, and the second busbar subsystem and the second disconnector subsystem are accommodated in another compartment module. The circuit-breaker is arranged in yet another compartment module. The cable connection is also situated in yet another compartment module. Although the double-busbar subsystem aims to achieve the potential advantage of higher availability, the fact that the busbar subsystem and disconnector subsystem are accommodated in one compartment module means that, in the event of a fault in which, for example, soot is formed, the system availability is not optimized. To enable the advantage of the availability of double-busbar subsystems to be fully utilized in the medium-voltage distribution system according to the invention, each subsystem is in each case accommodated in a separate, dedicated compartment module, which is in each case separated from the remaining compartment modules physically and in a touchproof way. Consequently, a failure of one function of the subsystem remains completely restricted to the relevant function or the relevant subsystem, and is not passed on to any further functions or subsystems. A preferred embodiment of a medium-voltage distribution system according to the invention is diagrammatically depicted in Fig. 2. The first busbar subsystem Rl is accommodated in the compartment module RC1, while the second busbar subsystem R2 is arranged in the second compartment module RC2. The cable connection KA is held in the compartment module KAC, while the circuit-breaker VS is in the compartment module VSC. The disconnectors SI and S2 are accommodated in the compartment modules SCI and SC2, respectively. The disconnectors SI and S2 are driven by the drive mechanisms Al and A2, respectively. The first disconnector subsystem SI is shown in the connected state, while the second disconnector system is shown in the disconnected state. The circuit-breaker is driven, in a manner which is not shown, via the drive A3. Each compartment module has a wall part which is weaker than the remaining wall parts. In the embodiment shown in Fig. 2, these weaker wall parts are the wall parts WI to W6 of the compartment modules KAC, RC2, VSC, SC2, RC2 and RC 1. If an explosion occurs in a compartment module as a result of incorrect operation of the subsystem accommodated therein, the weaker wall part will be blown away, as is diagrammatically indicated by the state of the wall part shown in dashed lines. It should be noted that the weaker part may obviously be a section of a wall part or may ■ comprise a number of wall parts. The weakened wall parts mean that, if an explosion occurs in a specific compartment module, the gases can escape, so that the pressure will not rise excessively. This prevents an entire medium- voltage distribution system from being irreparably damaged. Under the same explosion conditions, the mechanical strength of the remaining wall parts can remain limited, which will also be reflected in the costs. The weaker wall parts are situated at a location which is such that the gases which escape through the weaker wall parts on account of an excessively high pressure within the compartment module will have no adverse effect on the functions of the subsystems in the remaining compartment modules. The dissipation of the gases is indicated by dashed arrows. The weaker wall parts of the compartment modules of the switching subsystem, the disconnector subsystem and the external connection subsystem face upwards or downwards, with a view to protecting the operators. The compartments of the first and second busbar subsystems are connected to one another over the entire length of the installation, i.e. over the sections. If a busbar subsystem fails in one section, therefore, the busbar subsystem in question fails throughout the entire system. For this reason, the weaker wall parts of the compartment modules of the first and second busbar subsystems are preferably perpendicular to the busbar direction. The arrows indicated by dashed lines clearly show that, in the event of an explosion in one compartment module, the escaping gas, which often contains soot, will have no adverse effect on the other subsystems. The switching means, such as for example the disconnectors, of the medium- voltage distribution system according to the invention are driven by a drive mechanism which comprises at least one drive loop which is stretched over a drive roller and at least one rotatably mounted roller, with a straight drive loop section between them. The switching means are coupled to this straight drive loop section at a coupling point. The distance between the centre axes of the rollers and the position of the coupling point are matched to one another in such a manner that, when the drive roller is driven between its limit positions, the distance covered by the coupling point corresponds to the travel which is required in order to open or close the switching means which is to be driven. A standard, well-tensioned drive loop can be used for low drive forces. If higher drive forces are required, the loop could slip on the drive roller, and consequently it is preferable for the drive loop to be designed as an internally toothed drive belt, while the drive rollers have external toothing which meshes with the internal toothing. For even higher forces, a chain is most suitable, interacting with a sprocket wheel, the teeth of which mesh in the link openings of the chain. Fig. 3 shows an embodiment which is preferably to be used, in which two parallel chains with the associated sprocket wheels are employed. Via the gearbox 2, the electric motor drives the shafts 3 and 4. Sprocket wheels 5 and 6 are attached to the free ends of these shafts 3 and 4. The diagrammatically illustrated chains 7 and 8 are placed over the driving sprocket wheels 5 and 6 and the free-running sprocket wheels 9 and 10 and are stretched until they are taut. The principle of the drive mechanism according to the invention is based on the insight that the rotational movement of the output shaft of the electric motor 1 is converted, via a geared transmission, into a translational movement of the straight part of the chain 7, 8. This translational movement is necessary for the purpose of driving the switching means. A switching link 13, which is fixedly attached directly to the chains 7 and 8 by means of attachment links, is used for coupling the switching means to the straight parts of the chains 7 and 8. This switching link 13 may, for example, control the disconnector pins directly or via a transmission. It should be noted that the principle can obviously be implemented using one, two or more parallel drive loops, internally toothed drive belts or chains. The switching link executes a defined translational movement, which corresponds to the travel required to, for example, move the disconnector from the closed position to the open position or vice versa. Obviously, a minimum distance between the centre axes of the sprocket wheels for a defined location where the link is attached to the chains is associated with a desired travel. A position indicator 11 is fixedly attached to the straight section, in Fig. 3 the top right- hand side straight section, of the chain. The location of this position indicator indicates the switching state of, for example, a disconnector. The direct drive method makes the efficiency very good and the power consumption low. Unlike many designs of drives which have been used hitherto, the drive mechanism according to the invention is not self-locking. This means that the system runs very easily and also allows reversal of the transmission. Pushing the switching link causes it to execute a translational movement, with the result that the straight parts of the chains also execute a translational movement, while the motor rotates as a result. This property is undesirable in the limit positions of the switching means. In the case of an earthing disconnector, it is even the case that, with a continuous short-circuit current of 31.5 kA, outwardly directed drive forces of the order of magnitude of 2 kN are generated on the earthing link. Therefore, the drive mechanism according to the invention is provided with a limit-position locking means. The electric motor 1 is therefore provided with a motor brake 12 which is "on" by default, i.e. when there is no voltage applied to the motor. Therefore, in the absence of a control voltage on the electric motor, the latter is blocked by the brake. Manual operation is possible by simultaneously using one hand to lift the brake while the other hand actuates the motor shaft using a handle. This "two-handed" operation protects the disconnector from being used inadvertently.

Claims: CLAIMS 1. Encapsulated medium- voltage distribution system, comprising one or more sections which are composed of a number of compartment modules, which comprise a first busbar subsystem, a second busbar subsystem and a switching subsystem, and a disconnector subsystem for connecting or disconnecting the first busbar subsystem and/or the second busbar subsystem to and from an external connection subsystem, characterized in that each subsystem is in each case accommodated in a separate compartment module, which is in each case separated from the remaining compartment modules physically and in a touchproof way. 2. Medium- voltage distribution system according to Claim 1, characterized in that the compartment modules are provided with wall parts which are weaker than the remaining wall parts thereof. 3. Medium- voltage distribution system according to Claim 2, characterized in that the weaker wall parts are positioned and oriented in such a manner that the gases which escape through the wall parts in the event of an explosion in the compartment module in question cannot affect the operation of the other subsystems. 4. Medium- voltage distribution system according to Claim 2 or 3, characterized in that the outer surface of the weaker wall part of the compartment modules of the switching subsystem, the disconnector subsystem and the external connection subsystem faces downwards or upwards. 5. Medium- voltage distribution system according to Claim 2, 3 or 4, characterized in that the surface of the weaker wall part of the compartment module of the first and second busbar subsystems is perpendicular to the busbar direction. 6. Medium- voltage distribution system according to one of the preceding Claims, which is provided with a drive mechanism for driving one or more switching means, characterized in that the drive mechanism comprises at least one drive loop, which is stretched over a drive roller, and at least one rotatably mounted roller with, in between, a straight drive loop section, at a coupling point of which the switching means are coupled, the distance between the centre axes of the rollers and the position of the coupling point being matched to one another in such a manner that, when the drive roller is driven between its limit positions, the distance which is covered by the coupling point corresponds to the travel which is required in order to move the switching means which are to be driven from one position into the other position. 7. Medium-voltage distribution system according to Claim 6, characterized in that the drive loop is an internally toothed drive belt, and the drive roller has external toothing which meshes with the internal toothing. 8. Medium- voltage distribution system according to Claim 6, characterized in that the drive loop is a chain and the drive roller is formed by a sprocket wheel which meshes in the link openings of the chain. 9. Medium-voltage distribution system according to one of Claims 6-8, characterized in that the drive roller is driven by an electric motor with a reversible direction of rotation. 10. Medium- voltage distribution system according to Claim 9, characterized in that a limit-position locking means is provided. 11. Medium- voltage distribution system according to Claim 9 or 10, characterized in that the electric motor is provided with a blocking device which, in the absence of a control voltage, blocks the electric motor. 12. Medium-voltage distribution system according to one of the preceding Claims, characterized in that the drive loop is provided with a position indicator. 13. Medium- voltage distribution system according to one of the preceding Claims, characterized in that there are two parallel drive loops with associated rollers, and a switching link is attached to the drive loops at the coupling points.

Inventors: BINNENDIJK MARTEEN, ODIJK FRANK ADRIAAN, SCHOONENBERG GERARD CORNELIS, VAN DER ZANDE RICHARD, BINNENDIJK, MARTEEN, ODIJK, FRANK, ADRIAAN, SCHOONENBERG, GERARD, CORNELIS, VAN DER ZANDE, RICHARD
Applicants: BINNENDIJK MARTEEN, HOLEC HOLLAND NV, ODIJK FRANK ADRIAAN, SCHOONENBERG GERARD CORNELIS, ZANDE RICHARD V D, BINNENDIJK, MARTEEN, HOLEC HOLLAND N.V., ODIJK, FRANK, ADRIAAN, SCHOONENBERG, GERARD, CORNELIS, VAN DER ZANDE, RICHARD
Application year: 2001
Main classification: H02B13
IPC codes: H02B13