AU2012396428A1

AU2012396428A1 - Current transformer and load interrupter having such a current transformer

Info

Publication number: AU2012396428A1
Application number: AU2012396428A
Authority: AU
Inventors: Ludger Sandhager; Martin Schroder
Original assignee: EFEN GmbH
Current assignee: EFEN GmbH
Priority date: 2012-12-13
Filing date: 2012-12-13
Publication date: 2015-06-11
Anticipated expiration: 2032-12-13
Also published as: AU2012396428B2; HK1211704A1; CN104871013A; CN104871013B; BR112015013818A2; WO2014090319A1

Abstract

The present invention relates to a current transformer system having a current transformer, which detects a current flowing through the current transformer and converts said current into a measurement voltage, and evaluation electronics which, on the basis of the measurement voltage, determine at least one of the characteristic variables from the group G consisting of I, I

Description

WO 2014/090319 PCT/EP2012/075470 Current transformer and load interrupter having such a current transformer 5 The present invention concerns NH fuse switch disconnectors or NH fuse switch rails having a housing with a bottom surface and at least one feed-in contact and at least one outgoing contact. Such voltage high-power (NH) fuse switch disconnectors or NH fuse 10 switch rails have long been known and serve to provide secured outlets of busbars which can be separated under load. The devices generally have one or more lower fuse parts which are arranged in the housing. Corresponding fuse inserts are mounted for example on a switching cover so that, when the switching cover is closed, the fuse inserts are fitted into 15 the lower fuse parts and make a connection between the respective feed-in contacts - which can be connected to the busbars - and the outgoing contacts. When the switching cover is opened the fuse inserts are pulled out of the lower fuse parts so that the connection is interrupted. In principle the present invention can also be used in relation to open 20 distributor bars in which the fuse inserts can be pulled out of the open housing with a suitable tool. The term NH fuse switch rail is therefore also intended to embrace the open distributor bars. For many purposes of use measurement of the current flow by way of the provided outlet is desired. Current transformers are generally used 25 for that purpose. Current transformers operate like transformers, that is to say an alternating current flowing through the outgoing connection (primary conductor) induces in a secondary conductor afforded by the current transformer a secondary current which is galvanically separated from the primary circuit and which can be evaluated to measure the 30 primary current. Thus measurement is effected in contact-less manner. For example plug-on window type current transformers are known which have a primary conductor (for example in the form of an electrically conductive cylinder portion) and a secondary conductor surrounding same.

2 Upon fitment the current transformer is mounted on the feed-in contact so that the primary conductor contacts the feed-in contact and the primary conductor of the current transformer receives the current flowing through the feed-in contact. 5 What is common to the known current transformer systems is that the connection of the secondary conductor to corresponding evaluation devices is laborious as each current transformer must be connected by means of two connecting cables and at the same time shortcircuit-proof cabling is to be guaranteed. 10 Therefore, for the above-mentioned NH fuse switch rails it has already been proposed in DE 10 2007 051 419 that a current transformer module comprising three different current transformers which are respectively linked to a feed-in contact are provided at the underside of the housing. However even with that structure if required a corresponding 15 electronic evaluation device with a display device is to be respectively connected to the desired current transformer. Evaluation devices and in particular display devices are costly and cannot be fitted in the switching cabinets but are only connected if required to the corresponding current transformer. 20 In any case however it is necessary for a technician on site to connect the current transformer to the evaluation and display device in order to establish how much current is being taken off by way of the corresponding outlet. The known structures also only allow the display of a single parameter like for example the detected current strength. The 25 display of other parameters is either not possible or is only possible as an alternative so that it is not possible to implement simultaneous monitoring of a plurality of parameters. Taking the described state of the art as the basic starting point the object of the present invention is to provide an NH fuse switch disconnector 30 or an NH fuse switch rail of the kind set forth in the opening part of this specification, which easily allows the relevant parameters to be ascertained.

3 According to the invention that object is attained by a current transformer system comprising a current transformer with which the current flowing from the feed-in contact to the outgoing contact can be detected and converts it into a measurement voltage, and an electronic 5 evaluation means which on the basis of the measurement voltage ascertains at least one of the parameters from the group G comprising I, In, Ist, Imin, ITR, IMAX, U, Un, f, fn and PF, wherein I = electric current flowing through the current transformer, In = specified reference current strength for which the current transformer was designed, Ist = lowest specified value 10 of I, at which the current transformer measures an electrical active energy at a power factor of one, Imin = value of I, above which the deviation is within the error limits, It, = value of I, above which the deviation is within the lowest error limits which correspond to the accuracy class specified for the current transformer system, Imax = highest value of I at which the 15 deviation is within the error limits, U = electric voltage at the current transformer, Un = specified reference voltage, f = frequency of the voltage at the current transformer, fn = specified reference frequency, and PF = power factor = cosy = cosine of the phase shift p between I and U. In other words the current transformer system not only has the 20 actual current transformer but at the same time an electronic evaluation means which determines at least one of the parameters from the group G. In a preferred embodiment the electronic evaluation means ascertains at least two of the parameters from the group G and at the best all of said parameters. 25 The current transformer system can preferably have a bus system connecting terminal, by way of which the current transformer system can be connected to a bus system so that the ascertained parameters can be transmitted by way thereof. It is thus possible for the fuse switch load disconnector and the fuse 30 switch rail to be connected to a bus system so that the corresponding parameters can be read out by way of a computer which is also connected to the bus and which for example can be arranged at the energy provider and therefore does not necessarily have to be arranged in the proximity of 4 the switching cabinet. In that way it is possible to simultaneously monitor a plurality of parameters over a longer period of time without the presence of a technician being required. Particularly when a plurality of disconnectors or rails are to be 5 monitored each NH fuse switch disconnector or each NH fuse switch rail and at best each outgoing contact of the fuse switch disconnector or fuse switch rail advantageously has associated therewith its own identification address so that, at a remote location, for example at the energy provider, the characteristic parameters for each individual outgoing contact can be easily 10 detected without the need for a technician on site to temporarily connect the corresponding electronic evaluation means. Alternatively or in combination it is also possible for the current transformer system to have a connection for a display device. The display device can then represent the corresponding parameters on a display. It 15 will be appreciated that the connection for a display device must not only communicate the ascertained parameters but must also provide the energy supply for the display device. In that way if necessary a technician on site can also read out the desired parameters. In a further preferred embodiment the current transformer system 20 even has a display device for displaying the ascertained parameters so that there is no need to connect a corresponding display. In addition it has been found that the current transformer is to be arranged as much as possible surrounding the outgoing contact as it is here that the corresponding bus system and possibly a display device can be 25 easily connected. In other words the outgoing contact - or an element connected directly thereto - serves as a primary conductor for the current transformer. The current transformer system is either accommodated in the housing of the fuse switch disconnector or the fuse switch rail or it has its 30 own housing in which the individual components of the current transformer system are accommodated. In addition it is also possible for the current transformer system to be arranged partially in the housing of the fuse switch disconnector and partially in its own housing or for the current 5 transformer system to be arranged in two separate housings. For example the actual current transformer could be arranged in a housing separate from the electronic evaluation means, in which case then the two housings, that is to say the housing of the current transformer and the housing of the 5 electronic evaluation means have to be connected together. That can be effected for example by suitable connecting contacts. In a preferred embodiment there is provided a triggering monitoring means for the at least one fuse insert, which is preferably also arranged in the housing. The triggering monitoring means can also be read out by way 10 of the bus connection. In that way it is now possible even from a remote location, for example at the location of the energy provider, to establish which fuse insert has triggered so that a search for the fault is markedly simplified. Further advantages, features and possible uses will be clearly 15 apparent from the description hereinafter of a preferred embodiment and the related Figures in which: Figure 1 shows a diagrammatic view of an NH fuse switch disconnector with the current transformer system according to the invention, 20 Figure 2 shows a sectional view of a housing of a first current transformer system according to the invention, and Figure 3 shows a sectional view of housings of a second current transformer system according to the invention. Figure 1 shows a diagrammatic view of an NH fuse switch 25 disconnector 1. It has a housing 2 in which three fuse inserts 3, 3' and 3" are arranged. At its underside it is possible to see three outgoing contacts 4, 5, 6 as well as a current transformer block 9 which is fixed to the underside of the disconnector in such a way that the outgoing contacts extend through same. The current transformer system 9 has a connection 8 30 with which the transformer system can be connected to a bus system, that is to say a data transmission system. The embodiment also has a display device 7 which is capable of displaying the ascertained parameters.

6 Figure 2 shows a sectional view through the current transformer system of Figure 1. The housing 2 has a through opening 10 for receiving the corresponding outgoing contact. In addition Figure 2 shows an outgoing terminal 11, 12, the lower part 11 of which is in electrical contact with the 5 outgoing contact fitted into the through opening 10. The upper part 12 can be moved in the direction of the first part 11 by means of the screw 13 so that a corresponding cable which is to be fixed to the outgoing contact can be clamped between the two parts 11 and 12. The housing has a chamber 14 in which the corresponding electronic evaluation means can be placed. 10 Figure 3 shows an alternative embodiment. A substantial difference in relation to the embodiment shown in Figures 1 and 2 is that the electronic evaluation means 15 is now no longer disposed in the housing portion 14 but in a separate housing. Provided at the top side of the housing of the electronic evaluation means 15 is a metal contact block 19. 15 The current transformer 16 which surrounds a busbar 17 is connected to a connecting contact 18. The connecting contact 18 is biased resiliently on to the connecting block 19 so that there is an electrical connection between the electronic evaluation means 15 on the one hand and the current transformer 16 on the other hand. With this embodiment it is now possible 20 to exchange either the electronic evaluation means 15 or the current transformer housing without the respective other part having to be removed.

7 List of references 1 NH fuse switch disconnector 2 housing 5 3, 3', 3" fuse inserts 4 outgoing connection 5 outgoing connection 6 outgoing connection 7 display device 10 8 connection 9 housing 10 through opening 11 outgoing terminal 12 outgoing terminal 15 13 screw 14 chamber 15 electronic evaluation means 16 current transformer 17 busbar 20 18 connecting contact 19 connecting block

Claims

1. A current transformer system comprising a current transformer which detects a current flowing through the current transformer and 5 converts it into a measurement voltage, and an electronic evaluation means which on the basis of the measurement voltage ascertains at least one of the parameters from the group G comprising I, In, Ist, Imin, ITR, IMAX, U, Un, f, fn and PF, wherein I = electric current flowing through the current transformer, 10 In = specified reference current strength for which the current transformer was designed, Ist = lowest specified value of I, at which the current transformer measures an electrical active energy at a power factor of one, Imin = value of I, above which the deviation is within the error limits, 15 Itr = value of I, above which the deviation is within the lowest error limits which correspond to the accuracy class specified for the current transformer system, Imax = highest value of I at which the deviation is within the error limits, 20 U = electric voltage at the current transformer, Un= specified reference voltage, f = frequency of the voltage at the current transformer, f= specified reference frequency, and PF = power factor = cosy = cosine of the phase shift p between I 25 and U.

2. A current transformer system according to claim 1 characterised in that the electronic evaluation means ascertains at least two of the parameters from the group G. 30

3. A current transformer system according to claim 1 or claim 2 characterised in that the current transformer system has a bus system connection terminal, by way of which the current transformer system can 9 be connected to a bus system and the ascertained parameters can be transmitted.

4. A current transformer system according to one of claims 1 to 3 5 characterised in that there is provided a connection for a display device.

5. A current transformer system according to one of claims 1 to 4 characterised in that there is provided a display device for displaying the ascertained parameters. 10

6. A current transformer system according to one of claims 1 to 5 characterised in that the current transformer system has a transformer housing in which the individual components of the current transformer system are accommodated. 15

7. An NH fuse switch disconnector or NH fuse switch rail having a housing with a bottom surface and at least one feed-in contact which projects beyond the bottom surface and at least one outgoing contact, and at least a fuse insert which in the inserted condition connects the feed-in 20 contact to the outgoing contact, characterised in that there is provided a current transformer system according to one of claims 1 to 6.

8. An NH fuse switch disconnector or NH fuse switch rail according to claim 7 characterised in that the current transformer is arranged 25 surrounding the outgoing contact.

9. An NH fuse switch disconnector or NH fuse switch rail according to one of claims 7 and 8 characterised in that there are provided three feed-in contacts and three outgoing contacts and the current transformer system 30 has three current transformers, wherein each current transformer is arranged surrounding an outgoing contact. 10

10. An NH fuse switch disconnector or NH fuse switch rail according to one of claims 7 to 9 characterised in that there is provided a triggering monitoring means for the at least one fuse insert in the transformer housing.