WO2017132943A1

WO2017132943A1 - Device and method of testing accuracy of a current sensor in a switch cabinet

Info

Publication number: WO2017132943A1
Application number: PCT/CN2016/073503
Authority: WO
Inventors: Zhonghua Deng; Ping SU; Yongliang LIANG; Ying Jiang; Fei Cen; Chun CUI
Original assignee: Abb Schweiz Ag
Priority date: 2016-02-04
Filing date: 2016-02-04
Publication date: 2017-08-10

Abstract

A device and method for testing accuracies of current sensors in a switch cabinet. The device includes a chassis (160) and a sliding mechanism (170) on the chassis, for allowing the device being attached to the switch cabinet (200) or being detached from the switch cabinet. The chassis supports a power supply (110) operable to, in response to the device being attached to the switch cabinet, connect to a first current sensor (210) of the switch cabinet in series, a reference current sensor (120) connected to the power supply and operable to, in response to the device being attached to the switch cabinet, connect to the first current sensor of the switch cabinet in series, and a calibrator (130) operable to compare a reference current value sensed by the reference current sensor and a first current value sensed by the first current sensor of the switch cabinet. The device and method provides a convenient solution for testing accuracies of current sensors in the switch cabinet, without the need to remove the current sensors out of the switch cabinet, and thus improving the efficiency of testing.

Description

DEVICE AND METHOD OF TESTING ACCURACY OF A CURRENT SENSOR IN A SWITCH CABINET

TECHNOLOGY

Example embodiments disclosed herein generally relate to a testing device and a testing method. More specifically， the embodiments relate to a device and method of testing accuracy of a current sensor in a switch cabinet.

BACKGROUND

In a power distribution network， a switch cabinet (or switchgear) refers to a combination of electrical disconnect switches， fuses or circuit breakers used to control， protect and isolate electrical equipment. Normally， a switch or breaker within the switch cabinet may be equipped with a sensor for detecting the current passing through the switch or breaker， such that the switching on/off of the switch or breaker may be accurately controlled in response to the current exceeding a threshold， for example.

Performance of such a sensor may degrade over time and thus the readings of the sensor may be no longer reliable. A precise detection of the current is vital because mismatched accuracies among different sensors may result in a significant error of switch control. As such， the accuracy of the sensor needs to be tested once in a while so as to ensure the switch performance.

Currently， the sensors for detecting the current passing through need to be taken out of the switch cabinet so as to be tested， meaning that the sensors may not be tested in-situ. Thus， there is a need in the art for providing a solution to conveniently test accuracy of a sensor in the switch cabinet.

SUMMARY

Example embodiments disclosed herein propose a device for testing accuracy of a current sensor in a switch cabinet. The device is detachably installed to the switch cabinet when the test is to be carried out.

In one aspect， example embodiments disclosed herein provide a device， which includes： a chassis and a sliding mechanism on the chassis， for allowing the device being attached to a switch cabinet or being detached from the switch cabinet. The chassis supports a power supply operable to， in response to the device being attached to switch cabinet， connect to a first current sensor of the switch cabinet in series， a reference current sensor connected to the power supply and operable to， in response to the device being attached to the switch cabinet， connect to the first current sensor of the switch cabinet in series， and a calibrator operable to compare a reference current value sensed by the reference current sensor and a first current value sensed by the first current sensor of the switch cabinet.

In another aspect， example embodiments disclosed herein provide a method， which includes： in response to a device for testing a first current sensor in switch cabinet being attached to the switch cabinet， the device including a chassis and a sliding mechanism on the chassis， for allowing the device being attached to a switch cabinet or being detached from the switch cabinet： supplying power by a power supply supported by the chassis to the first current sensor via a reference current sensor supported by the chassis， the power supply， the reference current sensor and the first current sensor being connected in series， receiving， by a calibrator supported by the chassis， a reference current value sensed by the reference current sensor， receiving， by the calibrator， a first current value sensed by the first current sensor， and determining accuracy of the first current sensor by comparing the reference current value and the first current value.

Through the following description， it would be appreciated that the device or method according to the present disclosure provides a convenient solution for testing accuracies of the first current sensors in switch cabinet， without the need to remove the first current sensors out of the switch cabinet. By forming different loops， individual sensors can be tested in-situ. The resulting convenience allows users to carry out tests more frequently， resulting in a better reliability and performance of the switch cabinet.

DESCRIPTION OF DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings， the above and other objectives， features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings， several example embodiments disclosed herein will be illustrated in an example and in a non-limiting manner， wherein：

Figure 1 illustrates a schematic diagram of a testing device for testing accuracy of a current sensor in a switch cabinet in accordance with one example embodiment；

Figure 2 illustrates a schematic diagram of a testing device for testing accuracy of current sensors in a three phase configuration in a switch cabinet in accordance with another example embodiment；

Figure 3 illustrates a perspective view of a testing device in accordance with one example embodiment； and

Figure 4 illustrates a method of operating a testing device being detachably installed to a switch cabinet in accordance with one example embodiment.

Throughout the drawings， the same or corresponding reference symbols refer to the same or corresponding parts.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The subject matter described herein will now be discussed with reference to several example embodiments. These embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein， rather than suggesting any limitations on the scope of the subject matter.

The term “includes” and its variants are to be read as open terms that mean “includes， but is not limited to. ” The term “or” is to be read as “and/or” unless the context clearly indicates otherwise. The term “based on” is to be read as “based at least in part on. ” The term “being operable to” is to mean a function， an action， a motion or a state can be achieved by an operation induced by a user or an external mechanism. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” Unless specified or limited otherwise， the terms “mounted， ” “connected， ” “supported， ” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings， connections， supports， and couplings. Further， “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. In the description below， like reference numerals and labels are used to describe the same， similar or corresponding parts in the several views of Figures 1-3. Other definitions， explicit and implicit， may be included below.

Figure 1 shows a schematic diagram of a testing device 100 for testing accuracy of a first current sensor 210 in a switch cabinet 200 in accordance with one example embodiment. In Figure 1， dash lines indicate that the connection is detachable. A first line 201 is provided in the switch cabinet 200 for conducting current when a corresponding switch in the switch cabinet is closed for the first line 201. In other words， the first line 201 will be opened in response to the corresponding switch being turned off. A first current sensor 210 used in the switch cabinet 200 can be in the form of a ring-shaped inductor which encircles the first line 201. In this case， although the first current sensor 210 may not be in electrical contact with the first line 201， the first current sensor 210 can still be regarded as being coupled to the first line 201， because a coil of the first current sensor 210 encircling the first line 201 will generate a current in response to a current or a current change in the first line 201.

The first current sensor 210 may normally has a terminal for outputting a sensed current so that a component such as a relay or a controller may know the current or current change in the first line 201 detected by the first current sensor 210. In one example， the output signal may be in a fixed proportion to the current passing through the first line 201. Therefore， a particular value of the output signal of the first current sensor 210 or a first current value corresponds to a specific value of current passing through the first line 201. In another example， the first current sensor 210 may output a current or a voltage. It should be understood that the first current sensor in the form of a ring inductor is only an example， and any of appropriate current sensors can be used to detect the current in a line of the switch cabinet.

The testing device 100 can be removable from the switch cabinet 200 when the switch cabinet 200 is in normal operations. On the other hand， the testing device 100 can be installed to the switch cabinet 200 for testing accuracy of the first current sensor 210 when needed. The switch cabinet 200 may include a space for holding the testing device 100 and allowing the accuracy test to be carried out between the testing device 100 and the first current sensor 210 in the switch cabinet 200.

As shown in Figure 1， in one embodiment， the testing device 100 includes a power supply 110 for generating a current. The power supply 110 is connected to a first power line 101， through which the current flows past a reference current sensor 120. The reference current sensor 120 is a sensor for detecting the current flowing through a line to which the reference current sensor 120 is coupled. The reference current sensor 120 may operate in a similarly way to the first current sensor 210 in switch cabinet 200 and thus its principle will not be repeated. However， the reference current sensor 120 is constructed in a higher standard， meaning that the reference current sensor 120 is normally much more reliably accurate than the first current sensor 210. In other words， the reference current sensor 120 can be regarded as a reference， and the larger the first current value sensed by the first current sensor 210 differs from a reference current value sensed by the reference current sensor 120， the less accurate the first current sensor 210 is.

In one embodiment， the power supply 110 includes a voltage regulator and a current transformer (not shown) . By using these two apparatuses， the testing device 100 may receive power from the power distribution network via the switch cabinet 200 by the voltage regulator. The current transformer can be used to provide appropriate currents to be flown in the loop. However， it should be understood that there are other possible configurations for the power supply 110， and other apparatuses may be used to form the power supply 110.

In one embodiment， the reference current sensor 120 encircles or is coupled on the first power line 101. One end of the first power line 101 is engaged with the first line 201 in switch cabinet 200， so that the reference current sensor 120 and the first current sensor 210 are coupled in series when the testing device 100 is installed to the switch cabinet 200. The other end of the first line 201 is coupled with the power supply 110. A second power line 102 is coupled with the power supply 110 at one end and coupled with the first line 201 at the other end for conducting the current back to the power supply 110 when the testing device 100 is installed to the switch cabinet 200. Therefore， a current loop from the power supply 110 through the reference current sensor 120 and the first current sensor 210 and finally back to the power supply 110 can be formed by conducting a certain amount of current on the first power line 101， the first line 201 and the second power line 102.

In one embodiment， the testing device 100 includes a calibrator 130 for receiving the reference current value sensed by the reference current sensor 120. Upon the testing device 100 being installed to the switch cabinet 200， the calibrator 130 also receives the first current value sensed by the first current sensor 210. The calibrator 130 compares the reference current value sensed by the reference current sensor 120 and first current value sensed by the first current sensor 210. If the comparison shows that the first current value is deviated from the reference current value by a value exceeding a threshold in terms of amplitude and/or phase differences， it can be concluded that the accuracy of the first current sensor 210 is not acceptable and thus a maintenance or replacement is required for the first current sensor 210. Otherwise， the first current sensor 210 can still be considered accurate to use.

It should be understood that the first line 201 of the switch cabinet 200 is a part of the switch cabinet 200. The end of the first line 201 connecting to the first power line 101， when the testing device 100 is installed to the switch cabinet 200， is coupled with another line (not shown) in the switch cabinet 200 during normal operation of the switch cabinet 200. Although no switch or breaker component is shown in Figure 1， the first line 201 is coupled with a switch or breaker component during normal operation of the switch cabinet 200. The testing device 100 can be constructed as a module used for the switch cabinet 200， so that it is no longer required to detach the first current sensor 210 from the switch cabinet 200 for testing its accuracy.

Components such as the power supply 110， the reference current sensor 120 and the calibrator 130 can be supported by a chassis. A sliding mechanism is provided on the chassis for allowing the device being attached to a switch cabinet or being detached from the switch cabinet. Therefore， the testing device 100 is an independent device of the switch cabinet 200， and it can be installed to the switch cabinet by attaching the first power line 101 and the second power line 102 to the first line 201 across the first current sensor 210. By doing so， the testing device 100 can be contained in the switch cabinet 200 when it is installed to the switch cabinet 200. On the other hand， the testing device 100 can be detached from the switch cabinet 200 when the test is finished. The movement of the testing device 100 in and out of the switch cabinet 200 can be facilitated by the sliding mechanism， which will be explained with reference to Figure 3.

Although Figure 1 shows only one current sensor on one line， more current sensors can be used one the same line or on additional line (s) in the switch cabinet. The testing device may be used to test an individual current sensor in the switch cabinet， as described above. In other situations， the switch cabinet may include more than one current sensor on respective lines. Another example testing device may be used then to test the multiple current sensors， which will be explained in detail in the following by reference to Figure 2.

Figure 2 shows a schematic diagram of a testing device 100 for testing accuracy of a number of current sensors in switch cabinet 200 in accordance with another example embodiment. In Figure 2， dash lines indicate that the connection is detachable. Normally in a power distribution network， the energy is transferred in three phases and thus at least one line for each of the phases is required. Therefore， in the switch cabinet 200， a first line 201， a second line 202 and a third line 203 are provided. Each of the three

lines

201， 202， 203 is connected to a switch or breaker component (not shown) for functioning as the switch cabinet. However， it should be noted when current sensors of the switch cabinet 200 are to be tested， the switch or beaker components are opened and the three

lines

201， 202， 203 can be disconnected from a main circuit of the switch cabinet 200. As a result， a first terminal 251 is provided at one end of the first line 201 for connecting with the testing device 100. Similarly， a second terminal 252 is provided at one end of the second line 202， and a third terminal 253 is provided at one end of the third line 203.

In various embodiments described herein， a terminal of a line may be in the form of a separate component from the corresponding line， or as a part of the corresponding line such as the end portion of the line. The terminal is adapted to form an electrical connection to a component of another device or a line of another device， but the form， shape， size of the terminal are not to be limited.

As shown in Figure 2， each of the

lines

201， 202， 203 is equipped with a current sensor. Specifically， a first current sensor 210 is coupled to the first line 201， a second current sensor 220 is coupled to the second line 202， and a third current sensor 230 is coupled to the third line 203. As described above， a current sensor may be constructed in the form of a ring inductor not electrically connecting to a line， a sensor being coupled to a line means that the sensor interact with the line， allowing the sensor outputting an inducted current in response to a current flowing through the line.

In one embodiment， a grounding switch set 240 is provided in the switch cabinet 200. The grounding switch set 240 includes a first grounding switch 241 for connecting to the first line 201， a second grounding switch 242 for connecting to the second line 202， and a third grounding switch 243 for connecting to the third line 203. In case that one of the three

grounding switches

241， 242， 243 is closed， the corresponding one of the first， second and

third lines

201， 202， 203 will be grounded by a grounding line of the grounding switch set 240.

In one embodiment， a relay 240 is provided in the switch cabinet 200. The relay 240 is used to receive the inducted current or sensed current values from each of the first， second， third

current sensors

210， 220， 230. Namely， the relay 240 receives a first current value sensed by the first current sensor 210， a second current value sensed by the second current sensor 220， and a third current value sensed by the third current sensor 230. The relay 240 is used to control the expected current threshold for each of the current sensors， so that the relay 240 can be activated upon the current flowing through one of the lines being sensed to exceed the expected current threshold. A terminal 254 is provided for the relay 240 for forming a connection to the testing device 100. However， it should be understood that the relay 240 is not necessarily used， because sometimes the calibrator 140 of the testing device 100 directly receive the outputs from the three current sensors via three terminals， for example.

Similar to the embodiment described by reference to Figure 1， in one embodiment， the power supply 110 includes a power supply 110， a calibrator 130 and a reference current sensor 120. The functions and principles of these apparatuses are then not repeated. For example， the power supply 100 may include a voltage regulator as well as a current transformer.

In one embodiment， a first power line 101， a second power line 102 and a third power line 103 are connected to the power supply 110， with one of the power lines equipped with the reference current sensor 120. Although Figure 2 shows the reference current sensor 120 is equipped with the first power line 101， it should be understood that the reference current sensor 120 may be equipped with any of the three

power lines

101， 102， 103. One end of each of the three

power lines

101， 102， 103 is connected to the power supply 110， and the other end forms a corresponding terminal. Namely， a first power terminal 151， a second power terminal 152 and a third power terminal 153 are provided to be connected to the

terminals

251， 252， 253 in the switch cabinet when the testing device 100 is installed to the switch cabinet 200. The calibrator 130 also has a terminal 154 to be connected to the terminal 254 for receiving the first current value， the second current value， and the third current value sensed respectively by the first

current sensors

210， 220， 230 via the relay 240.

When the testing device 100 is installed to the switch cabinet 200， the first power line 101 is connected to the first line 201， the second power line 102 is connected to the second line 202， and the third power line 103 is connected to the third line 203， via corresponding terminals. The first power line 101 and the second power line 102 can be connected within the power supply 110. In this case， if the first grounding switch 241 and the second grounding switch 242 are closed， a loop is formed from the power supply 110， to the reference current sensor 120 on the first power line 101， the first current sensor 210 on the first line 201， the first grounding switch 241， the grounding line， the second grounding switch 242， the second current sensor 220 on the second line 202， through the second power line 102， and back to the power supply 110. The reference current sensor 120， the first current sensor 210 and the second current sensor 220 are connected in series， such that the current flowing through is the same current for each of the reference current sensor 120， the first current sensor 210， and the second current sensor 220. The third grounding switch 243 should be opened when the test is carried out for the first current sensor 210 and the second current sensor 220 in the above mentioned loop. In this regard， accuracies of the first current sensor 210 and the second current sensor 220 can be obtained simultaneously because the current flows through the two

current sensors

210， 220 in series.

In another example， if the first grounding switch 241 and the third grounding switch 243 are closed， a loop is formed from the power supply 110， to the reference current sensor 120 on the first power line 101， the first current sensor 210 on the first line 201， the first grounding switch 241， the grounding line， the third grounding switch 243， the third current sensor 230 on the third line 203， through the third power line 103， and back to the power supply 110. The reference current sensor 120， the first current sensor 210 and the third current sensor 230 are connected in series， such that the current flowing through is the same current for each of the reference current sensor 120， the first current sensor 210， and the third current sensor 230. The first grounding switch 241 should be opened when the test is carried out for the third current sensor 230 and the first current sensor 210 in the above mentioned loop. In this regard， accuracies of the first current sensor 210 and the third current sensor 230 can be obtained simultaneously because the current flows through the two

current sensors

210， 230 in series. It should be appreciated that different loops can be formed based on which power line the reference current sensor 120 is equipped with.

In one embodiment， all of the switches of the grounding switch set 240 are switched on/off simultaneously， meaning that the first grounding switch 241， the second grounding switch 242 and the third grounding switch 243 are either closed or opened altogether. In this case， the testing device 100 may further include a controller 140. The first power line 101 is inserted with a first power switch 141， the second power line 102 is inserted with a second power switch 142， and the third power line 103 is inserted with a third power switch 143. In this example， each of the power switches 141， 142， 143 is controlled by the controller 140. The first and

second power switch

141， 142 may be closed while the third power switch 143 is opened， so that the first current sensor 210 and the second current sensor 220 are connected to the power supply 110 while the third current sensor 230 is disconnected to the power supply 110. As a result， a loop to test the accuracies of the first current sensor 210 and the second current sensor 220 is formed in response to the testing device 100 being installed to the switch cabinet 200 and the grounding switches being closed altogether. Similarly， the first and

third power switch

141， 143 may be closed while the second power switch 142 is opened， so that the first current sensor 210 and the third current sensor 230 are connected to the power supply 110 while the second current sensor 220 is disconnected to the power supply 110. As a result， another loop to test the accuracies of the first current sensor 210 and the third current sensor 230 is formed in response to the testing device 100 being installed to the switch cabinet 200 and the grounding switches being closed altogether.

In this embodiment， to test the accuracies of the current sensors， the first power switch 141 should be closed， and at least one of the second and

third power switch

142， 143 should be closed while the other can be opened or closed， such that at least one loop is formed， enabling the current flowing in the loop. The second current sensor 220 and the third current sensor 230 are connected in parallel in the switch cabinet 200. When exact one of the second current sensor 220 and the third current sensor 230 is connected to the power supply 110 and the other one is disconnected to the power supply 110， a single loop is formed. The single loop enables a simultaneous comparison among the reference current value sensed by the reference current sensor 120， the first current value sensed by the first current sensor 210， and one of the second and third

current sensors

220， 230. Therefore， accuracy tests for two current sensors can be carried our simultaneously.

In another embodiment， the second current sensor 220 and the third current sensor 230 can be both connected to the power supply 110 at the same time. This will split the current flowing through the first current sensor 210 to two flows， one flowing through the second current sensor 220 and the other flowing through the third current sensor 230. This results in the second and third current value unable to be compared with the reference current value sensed by the reference current sensor 120 because the exact second current value and the third current value sensed respectively by the second current sensor 220 and the third current sensor 230 are usually unknown. However， the first current value sensed by the first current sensor 210 can be compared with the reference current value sensed by the reference current sensor 120， because the current flowing through the reference current sensor 120 also flows through the first current sensor 210.

The testing devices in accordance with various example embodiments enable the current sensors of the switch cabinet to be tested without being removed out of the switch cabinet. As can be seen in Figures 1 and 2， each of the current sensors of the switch cabinet can be tested in-situ by configuring a particular loop for testing a sensor or multiple sensors intended to be tested. Such a convenience allows users to carry out tests more frequently， resulting in an improved reliability and performance of the switch cabinet.

Figure 3 shows an example embodiment of a testing device 100. A chassis 160 is provided for supporting components such as the power supply 110 (not shown in Figure 3) ， the reference current sensor 120 and the calibrator 130 (not shown in Figure 3) . The chassis 160 can be constructed in any way as long as the structure is robust enough. Three pipes， each containing a power line， extend upwards from the bottom of the chassis 160， in each of the pipes the reference current sensor 120 can be contained. The three

power terminals

151， 152， 153 are provided at the ends of the three pipes for forming detachable connections to the three

terminals

251， 252， 253 of the switch cabinet 200. When the testing device 100 is attached to the switch cabinet 200， the three

power terminals

151， 152， 153 can be aligned with the first， second and third

current sensors

210， 220， 230， respectively. Here， “attachment” means that the testing device 100 is fully installed into the switch cabinet 200 with the

power terminals

151， 152， 153 aligning with the positions of the first， second and third

current sensors

210， 220， 230. In such an “attached” configuration， the power lines of the testing device 100 are automatically connected to the lines of the switch cabinet 200. As such， the alignment and attachment allow the power supply 110 (not shown) being connected to the first， second and third

current sensors

210， 220， 230 via the three

power terminals

151， 152， 153.

A sliding mechanism 170 can be provided on the chassis 160 to facilitate a smooth attachment of the testing device 100 into the switch cabinet 200. Such a sliding mechanism 170 can， for example， be a number of wheels so that they are fit into and cooperate with a guide rail in the switch cabinet 200. By means of these wheels cooperating with the guide rail， the testing device 100 can be easily attached to or detached from the switch cabinet 200 by a user or an external activation mechanism. It is to be understood that other types of the sliding mechanisms are also possible， such as chains or gears.

Figure 4 shows a method 400 of operating a device being detachably installed to switch cabinet in accordance with one example embodiment. The device includes a chassis and a sliding mechanism on the chassis， for allowing the device being attached to a switch cabinet or being detached from the switch cabinet. In response to the device for testing a first current sensor in switch cabinet being attached to the switch cabinet， in step 401， power is supplied by a power supply of the device to the first current sensor via a reference current sensor of the device. The power supply， the reference current sensor and the first current sensor are connected in series. In step 402， a reference current value sensed by the reference current sensor is received by a calibrator of the device. In step 403， a first current value sensed by the first current sensor is received by the calibrator. In step 404， accuracy of the first current sensor is determined by comparing the reference current value and the first current value.

In one embodiment， the method 400 may further include： in response to the power supply being connected to a second current sensor of the switch cabinet， the first and second current sensors being connected in series： receiving， by the calibrator， a second current value sensed by the second current sensor， and determining accuracy of a second current sensor by comparing the reference current value and the second current value.

In a further embodiment， the method 400 may further include： in response to the power supply being connected to the second current sensor， disconnecting a third current sensor of the switch cabinet from the power supply， the second and third current sensors being connected in parallel.

In another embodiment， the method 400 may further include： disconnecting the second current sensor from the power supply， connecting the third current sensor to the power supply， and determining accuracy of the third current sensor by comparing the reference current value and the third current value.

In yet another embodiment， the method 400 may further include： in response to the device being attached to the switch cabinet， receiving each of the first current value， the second current value and the third current value via a relay of the switch cabinet.

In still another embodiment， the power supply may include a voltage regulator and a current transformer.

The method 400 and related steps may use apparatuses or components described by reference to Figures 1 and 2. Therefore， the functions and principles of these apparatuses or components will not be repeated.

The above embodiments described herein present a device to be used with switch cabinet. It is no longer needed to remove the current sensors out of the switch cabinet for testing their accuracies because the device is able to form a loop to compare one or more current sensors in the switch cabinet with a reference current sensor in the device. Therefore， the testing of the current sensors can be carried our in-situ， and thus the efficiency to operate the testing can be greatly improved.

While operations are depicted in a particular order in the above descriptions， it should not be understood as requiring that such operations be performed in the particular order shown or in sequential order， or that all illustrated operations be performed， to achieve desirable results. In certain circumstances， multitasking and parallel processing may be advantageous. Likewise， while several details are contained in the above discussions， these should not be construed as limitations on the scope of the subject matter described herein， but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. On the other hand， various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the subject matter has been described in language specific to structural features and/or methodological acts， it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather， the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A device comprising：

a chassis； and

a sliding mechanism on the chassis， for allowing the device being attached to a switch cabinet or being detached from the switch cabinet， the chassis supporting：

a power supply operable to， in response to the device being attached to the switch cabinet， connect to a first current sensor of the switch cabinet in series；

a reference current sensor connected to the power supply and operable to， in response to the device being attached to the switch cabinet， connect to the first current sensor of the switch cabinet in series； and

a calibrator operable to compare a reference current value sensed by the reference current sensor and a first current value sensed by the first current sensor of the switch cabinet.
The device according to Claim 1， wherein

the power supply is operable to， in response to the device being attached to the switch cabinet， connect to a second current sensor of the switch cabinet， the first and second current sensors being connected in series， and

the calibrator is further operable to compare the reference current value and a second current value sensed by the second current sensor.
The device according to Claim 2， wherein the switch cabinet further includes a third current sensor connected in parallel with the second current sensors， the device further comprising：

a controller operable to， in response to the power supply being connected to the second current sensor， disconnect the third current sensor from the power supply.
The device according to Claim 3， wherein

the controller is further configured to disconnect the second current sensor from the power supply and to connect the third current sensor to the power supply， and

the calibrator is further operable to compare the reference current value and a third current value sensed by the third current sensor.
The device according to Claim 4， wherein the calibrator is operable to receive each of the first current value， the second current value and the third current value via a relay of the switch cabinet in response to the device being attached to the switch cabinet.
The device according to any of Claims 3 to 5， wherein the device further comprises three terminals to align with the first， second and third current sensors respectively in response to the device being attached to the switch cabinet， allowing the power supply being connected to the first， second and third current sensors via the three terminals.
The device according to any of Claims 1 to 5， wherein the power supply includes a voltage regulator and a current transformer.
The device according to any of Claims 1 to 5， wherein the sliding mechanism includes a plurality of wheels to slide along a guide rail in the switch cabinet.
A method comprising：

in response to a device for testing a first current sensor in a switch cabinet being attached to the switch cabinet， the device including a chassis and a sliding mechanism on the chassis， for allowing the device being attached to a switch cabinet or being detached from the switch cabinet：

supplying power by a power supply supported by the chassis to the first current sensor via a reference current sensor supported by the chassis， the power supply， the reference current sensor and the first current sensor being connected in series；

receiving， by a calibrator supported by the chassis， a reference current value sensed by the reference current sensor；

receiving， by the calibrator， a first current value sensed by the first current sensor； and

determining accuracy of the first current sensor by comparing the reference current value and the first current value.
The method according to Claim 9， further comprising：

in response to the power supply being connected to a second current sensor of the switch cabinet， the first and second current sensors being connected in series：

receiving， by the calibrator， a second current value sensed by the second current sensor； and

determining accuracy of a second current sensor by comparing the reference current value and the second current value.
The method according to Claim 10， further comprising：

in response to the power supply being connected to the second current sensor， disconnecting a third current sensor of the switch cabinet from the power supply， the second and third current sensors being connected in parallel.
The method according to Claim 11， further comprising：

disconnecting the second current sensor from the power supply；

connecting the third current sensor to the power supply； and

determining accuracy of the third current sensor by comparing the reference current value and the third current value.
The method according to Claim 12， further comprising：

in response to the device being attached to the switch cabinet， receiving each of the first current value， the second current value and the third current value via a relay of the switch cabinet.
The method according to any of Claims 9 to 13， wherein the power supply includes a voltage regulator and a current transformer.
The method according to any of Claims 9 to 13， wherein the sliding mechanism includes a plurality of wheels to slide along a guide rail in the switch cabinet.