HK1211704B - Current transformer and load interrupter having such a current transformer - Google Patents

Description

Current transformer and load interrupter having the same

Technical Field

The invention relates to an NH fuse switch circuit breaker or an NH fuse switch rail having a housing with a bottom surface and at least one feed connection and at least one output connection.

Background Art

Such high-voltage (NH) fuse-switch circuit breakers or NH fuse-switch rails are well known and are used to provide a safe outlet from a busbar that can be disconnected under load. These devices typically have one or more lower fuse assemblies arranged in a housing. The corresponding fuse inserts are mounted, for example, on a switch cover. When the cover is closed, the fuse inserts fit into the lower fuse assemblies and connect the corresponding infeed and outfeed connections, which can be connected to the busbar. When the cover is opened, the fuse inserts are removed from the lower fuse assemblies, interrupting the connection.

In principle, the invention can also be used in connection with open distributor bars, in which the fuse inserts can be extracted from the open housing with a suitable tool.The term NH fuse switch rail is therefore also intended to encompass open distributor bars.

For many purposes, it is necessary to measure the current flowing through the provided outlet. Current transformers are commonly used for this purpose. Current transformers operate like instrument transformers. An alternating current flowing through the output connector (primary conductor) induces a secondary current in the secondary conductor provided by the current transformer. This secondary current is galvanically isolated from the primary circuit and can be evaluated to measure the primary current. The measurement is thus carried out contactlessly.

For example, plug-type window-type current transformers are known, which have a primary conductor (e.g., in the form of a conductive cylindrical portion) and a secondary conductor surrounding the primary conductor. When installed, the current transformer is mounted on the feed connector so that the primary conductor contacts the feed connector and the primary conductor of the AC transformer receives the current flowing through the feed connector.

A common feature of the known current transformer systems is that the connection of the secondary conductors to the corresponding evaluation device is complex, since each current transformer must be connected via two connecting cables and at the same time short-circuit-proof wiring must be ensured.

Therefore, for the aforementioned NH fuse switch rail, as proposed in DE 10 2007 051 419, a current transformer module comprising three different current transformers, each connected to a feed connection, is arranged on the underside of the housing. However, even with this arrangement, if necessary, corresponding electronic evaluation equipment with a display device must be connected to the required current transformers. The evaluation equipment, and in particular the display device, is expensive and cannot be installed in the switch cabinet. Instead, it can only be connected to the corresponding current transformers when required.

In any case, however, a technician is required to connect the current transformer to the evaluation and display device on site to determine how much current is flowing through the corresponding outlet. Known structures also only allow the display of a single parameter, such as the detected current intensity. The display of other parameters is either not possible or can only be used as an alternative, making it impossible to monitor multiple parameters simultaneously.

Summary of the Invention

Taking the described state of the art as a basic starting point, the object of the present invention is to provide an NH fuse breaker or an NH fuse rail of the type explained in the opening part of the description which conveniently allows the relevant parameters to be determined.

According to the invention, this object is achieved by a current transformer system comprising a current transformer, by means of which a current flowing from an infeed connection to an output connection can be detected and converted into a measurement voltage, and an electronic evaluation device, which determines from the measurement voltage at least one parameter from a group G consisting of I, _In , _Ist , _Imin , _Itr , _Imax , U, _Un , f, _fn , and PF, wherein I=the current flowing through the current transformer, _In =a specified reference current intensity for which the current transformer is designed, _Ist =the lowest specified value of I at which the _current transformer measures active energy at a power factor of 1, _Imin =the value of _I above which the deviation is within an error limit, _Itr =the value of I above which the _deviation is within a lowest error limit corresponding to the accuracy class assigned to the current transformer system, _Imax =the highest value of I at which the _deviation is within an error limit, U=the voltage at the current transformer, _Un = specified reference voltage, f = frequency of the voltage at the current transformer, f _n = specified reference frequency, and the cosine of the phase shift between and U.

In other words, the current transformer has not only the actual current transformer but also simultaneously an electronic evaluation device which determines at least one of the parameters from group G.

In a preferred embodiment, the electronic evaluation device determines at least two of the parameters from group G, and preferably all of said parameters.

The current transformer system can preferably have a bus system connection terminal, via which the current transformer system can be connected to a bus system, so that certain parameters can be transmitted via it.

Thus, fuse switch load breakers and fuse switch rails can be connected to a bus system, so that the corresponding parameters can be read out by a computer, which is also connected to the bus and can be located, for example, at the energy supplier and therefore does not necessarily have to be located near the switch cabinet. In this way, multiple parameters can be monitored simultaneously over a longer period of time without the need for a technician to be present.

In particular when a plurality of circuit breakers or rails are to be monitored, each NH fuse switch circuit breaker or each NH fuse switch rail and preferably each output connection of the fuse switch circuit breaker or fuse switch rail is advantageously already associated with its own identification address, so that at a remote location, for example at the energy supplier, the characteristic parameters of each respective output connection can be easily detected without requiring a technician to come on site to temporarily connect the corresponding electronic evaluation tool.

Alternatively or in combination, the current transformer system can also be connected to a display device. The display device can then display the corresponding parameters on a display. It should be understood that the connection to the display device must not only transmit the determined parameters but also provide energy for the display device. This allows technicians to read out the required parameters on site, if necessary.

In a further preferred embodiment, the current transformer system even has a display device which displays the determined parameters, so that it is not necessary to connect a corresponding display.

Furthermore, it has been found that the current transformer is arranged as close as possible to the output connection, since the corresponding bus system and any display device can be easily connected here. In other words, the output connection—or the element directly connected thereto—serves as the primary conductor of the current transformer.

The current transformer system is either housed in the housing of the fuse switch circuit breaker or the fuse switch rail, or in its own housing, in which the components of the current transformer system are housed. Furthermore, the current transformer system can be arranged partially in the housing of the fuse switch circuit breaker and partially in its own housing, or it can be arranged in two separate housings. For example, the actual current transformer can be arranged in a housing separate from the evaluation electronics. In this case, the two housings—the housing of the current transformer and the housing of the evaluation electronics—must then be connected together. This can be achieved, for example, via suitable connecting connectors.

In a preferred embodiment, there is a trigger monitoring device which provides at least one fuse insert, which is also preferably arranged in the housing.The trigger monitoring device can also be read out via the bus connector.

In that way, it is now possible to determine even from a remote location, for example at the location of the energy supplier, that the fuse insert has triggered, so that the fault finding is significantly simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages, features and possible uses of the present invention will become apparent from the following description of preferred embodiments and the associated drawings, in which:

FIG1 shows a schematic diagram of an NH fuse switch circuit breaker with a current transformer (transformer) system according to the present invention;

FIG2 shows a cross-sectional view of a housing of a first current transformer system according to the invention, and

FIG3 shows a cross-sectional view of a housing of a second current transformer system according to the present invention.

DETAILED DESCRIPTION

FIG1 shows a schematic diagram of an NH fuse switch circuit breaker 1. It has a housing 2 in which three fuse inserts 3, 3′, and 3″ are arranged. On its underside, three output terminals 4, 5, and 6 can be seen, as well as a current transformer block 9, which is fixed to the underside of the circuit breaker in such a way that the output terminals extend through the circuit breaker. The current transformer system 9 has a connection 8, via which it can be connected to a bus system, i.e., a data transmission system. The embodiment also has a display device 7 that can display certain parameters.

Figure 2 shows a cross-sectional view of the current transformer system of Figure 1. The housing 2 has a through-hole 10 for receiving the corresponding output connector. Figure 2 also shows output terminals 11 and 12, with the lower part 11 making electrical contact with the output connector inserted into the through-hole 10. The upper part 12 can be moved toward the upper part 11 by screws 13, allowing the corresponding cable secured to the output connector to be clamped between the two parts 11 and 12. The housing has a chamber 14 in which the corresponding evaluation electronics can be placed.

FIG3 shows an alternative embodiment. The essential difference with respect to the embodiments shown in FIG1 and 2 is that the evaluation electronics 15 are no longer arranged in the housing part 14, but in a separate housing. A metal contact block 19 is provided on the top side of the housing of the evaluation electronics 15. The current transformer 16, which surrounds the busbar 17, is connected to a connection lug 18. The connection lug 18 is elastically biased against the connection block 19, ensuring an electrical connection between the evaluation electronics 15 on the one hand and the current transformer 16 on the other. This embodiment now allows either the evaluation electronics 15 or the current transformer housing to be replaced without having to dismantle the other component.

Reference Signs List

1 NH fuse switch circuit breaker

2. Housing

3,3',3" Fuse Inserts

4 output connectors

5 Output connector

6 Output connector

7 Display Devices

8 Connectors

9. Housing

10 through holes

11 Output terminals

12 output terminals

13 screws

14 Chamber

15 Electronic evaluation device

16 Current transformer

17 busbar

18 Connector

19 Connection Block

Claims (18)

1. An NH fuse switch circuit breaker, comprising: a housing having a bottom surface; at least one feeder connector extending from the bottom surface; at least one output connector; and at least one insert; wherein the at least one insert, in an inserted state, connects the feeder connector to the output connector, wherein a current transformer system is provided, comprising: a current transformer that detects current flowing through the current transformer and converts the detected current into a measured voltage; and an electronic evaluation device that determines, based on the measured voltage, at least one parameter from a group G comprising I, _In , _Ist , _Imin , _Itr , _Imax , U, _Un , f, _fn , and PF, wherein: I = Current flowing through the current transformer; _In = is the specified reference current intensity designed for the current transformer; I _{_st} = the lowest specified value of I, where I_{_st} is the active energy measured by the current transformer when the power factor is 1. If the value of _{I_min} = I is greater than _{I_min} , the deviation is within the error limit; The value of _Itr = I is greater than _Itr , and the deviation is within the minimum error limit corresponding to the accuracy class specified for the current transformer system; _Imax = the highest value of I, where the _deviation is within the error limit; U = the voltage at the current transformer; U _{_n} = specified reference voltage; f = the voltage frequency at the current transformer; f _{_n} = specifies the reference frequency, and PF = Power Factor = cosj = Cosine of the phase shift j between I and U The current transformer is arranged around the output terminal. 2. The NH fuse switch circuit breaker as claimed in claim 1, characterized in that it is provided with three feed in terminals and three output terminals, and the current transformer system has three current transformers, wherein each current transformer is arranged around the output terminals. 3. The NH fuse switch circuit breaker as claimed in claim 1 or 2, characterized in that it provides a trigger monitoring device with at least one fuse insert, wherein the current transformer system has a transformer housing, and the at least one fuse insert is housed in the transformer housing. 4. The NH fuse switch circuit breaker as claimed in claim 1, wherein the electronic evaluation device determines at least two of the parameters from the group G. 5. The NH fuse switch circuit breaker as claimed in claim 1, characterized in that: the current transformer system has a bus system connection terminal, through which the current transformer system can be connected to the bus system and can transmit defined parameters. 6. The NH fuse switch circuit breaker as claimed in claim 1, characterized in that: it is provided with a connector for a display device. 7. The NH fuse switch circuit breaker as described in claim 1, characterized in that: it has a display device for displaying determined parameters. 8. The NH fuse switch circuit breaker as described in any one of claims 1, 2, 4 to 7, characterized in that: the current transformer system has a transformer housing, and the components of the current transformer system are housed in the transformer housing. 9. The NH fuse switch circuit breaker as claimed in claim 3, wherein each component of the current transformer system is housed within the transformer housing. 10. An NH fuse switch rail, comprising: a housing having a bottom surface; at least one feeder connector extending from the bottom surface; at least one output connector; and at least one insert; wherein the at least one insert, in an inserted state, connects the feeder connector to the output connector, characterized in that: a current transformer system is provided, comprising: a current transformer that detects a current flowing through the current transformer and converts the detected current into a measurement voltage; and an electronic evaluation device that determines, based on the measurement voltage, at least one parameter from a group G comprising I, _{In, Ist, Imin, Itr, Imax , U , Un ,} f, _fn , and PF, wherein: I = Current flowing through the current transformer; _In = is the specified reference current intensity designed for the current transformer; I _{_st} = the lowest specified value of I, where I_{_st} is the active energy measured by the current transformer when the power factor is 1. If the value of _{I_min} = I is greater than _{I_min} , the deviation is within the error limit; The value of _Itr = I is greater than _Itr , and the deviation is within the minimum error limit corresponding to the accuracy class specified for the current transformer system; _Imax = the highest value of I, where the _deviation is within the error limit; U = the voltage at the current transformer; U _{_n} = specified reference voltage; f = the voltage frequency at the current transformer; f _{_n} = specifies the reference frequency, and PF = Power Factor = cosj = Cosine of the phase shift j between I and U The current transformer is arranged around the output terminal. 11. The NH fuse switch rail as claimed in claim 10, characterized in that: it is provided with three feed in terminals and three output terminals, and the current transformer system has three current transformers, wherein each current transformer is arranged around the output terminals. 12. The NH fuse switch rail as claimed in claim 10 or 11, characterized in that: a trigger monitoring device is provided for at least one fuse insert in the transformer housing of the current transformer system. 13. The NH fuse switch rail as claimed in claim 10, wherein the electronic evaluation device determines at least two of the parameters from the group G. 14. The NH fuse switch rail as described in claim 10, characterized in that: the current transformer system has a bus system connection terminal, through which the current transformer system can be connected to a bus system and can transmit defined parameters. 15. The NH fuse switch guide rail as claimed in claim 10, characterized in that: a connector for a display device is provided. 16. The NH fuse switch guide rail as claimed in claim 10, characterized in that: it has a display device for displaying the determined parameters. 17. The NH fuse switch rail as described in any one of claims 10, 11, 13 to 16, characterized in that: the current transformer system has a transformer housing, and the components of the current transformer system are housed in the transformer housing. 18. The NH fuse switch rail as described in claim 12, wherein each component of the current transformer system is housed within the transformer housing.