DEVICE AND METHOD FOR DETERMINING A CHARACTERISTIC OF A TRANSFORMER

Description

FIELD OF THE INVENTION

[0001] Embodiments of the invention relate to a device and a method for determining at least one characteristic of a transformer. Embodiments of the invention particularly relate to such devices and methods that enable conclusions to be drawn about a reactance. BACKGROUND

[0002] Transformers are used as components of power grids. Transformers can be used to convert voltage from a first value on a high-voltage side to a second value, which is lower than the first value, on a low-voltage side.

[0003] Determining transformer properties through a transformer test, in which one or more characteristic parameters of the transformer are determined through measurement, is necessary, for example, to ensure operational safety, for control, or for other reasons. Examples of such measurements include determining a static resistance or a transformation ratio, as well as the determination of a leakage inductance or leakage reactance. Leakage reactance can be used to detect deviations from the transformer's characteristics defined in a data sheet, which can be caused, for example, by deformation of a winding.

[0004] EP2787357 A1 discloses a method and apparatus for testing a transformer or instrument transformer, in particular for testing the accuracy of voltage transformers. WO 2016 / 066701 A1 with EP 3 213 095, which is registered under Article 54(3)

[0005] EPC, discloses a transformer testing apparatus and a method for testing transformers. 1

[0006] There is a need for devices and methods that can efficiently determine at least one characteristic of a transformer. There is a need for devices and methods that allow the automation of determining such characteristics. SUMMARY OF THE INVENTION

[0007] The invention is defined by the apparatus of independent claim 1 and the method of independent claim 10.

[0008] According to embodiments, a device and a method for determining a characteristic of a transformer are specified, which are configured to impress a test signal on a low-voltage side of a transformer and to determine a leakage reactance and / or leakage inductance of the transformer depending on a test response.

[0009] A device and method designed in this way provide greater flexibility in determining parameters, as the test signal is applied to the low-voltage side. The leakage reactance and / or leakage inductance can be determined automatically. The leakage reactance and / or leakage inductance can be determined without necessarily requiring rewiring of the connections between the transformer test device and the transformer.

[0010] The device used to determine the characteristic comprises a controllable switching device that shorts one high-voltage side of the transformer while applying the test signal to the low-voltage side. This facilitates the automatic, sequential determination of multiple characteristic values.

[0011] The source of the transformer testing device can be designed so that it can be operated selectively as a current source or as a voltage source.

[0012] The controllable switching means may be a relay or may comprise a relay. The controllable switching means may be an insulated-gate bipolar transistor (IGBT) or a field-effect transistor (FET), or may comprise an IGBT or a FET.

[0013] A device is configured to determine a characteristic of a transformer having a high-voltage side and a low-voltage side. The device comprises terminals for detachably connecting the device to the low-voltage side of the transformer. The device comprises a source for generating a test signal, which is coupled to the terminals in order to impress the test signal on the low-voltage side of the transformer. The device comprises an evaluation device configured to determine a leakage reactance and / or a leakage inductance of the transformer as a function of a test response of the transformer.

[0014] The evaluation device may comprise at least one integrated semiconductor circuit that evaluates the test response.

[0015] The device includes additional terminals for detachably connecting the device to the high-voltage side of the transformer.

[0016] The device may comprise a measuring device coupled to the further terminals for detecting the test response. The measuring device may comprise a voltmeter.

[0017] The device comprises a controllable switching means connected to the further terminals for short-circuiting the high-voltage side.

[0018] The controllable switching means may be integrated into a housing of the device. The controllable switching means may be a relay or other switch configured to switch a load circuit under the control of a control circuit. The controllable switching means may be an insulated-gate bipolar transistor (IGBT) or a field-effect transistor (FET), or may comprise an IGBT or a FET.

[0019] The device is designed to control the controllable switching means such that the high-voltage side is short-circuited while the test signal is impressed on the low-voltage side.

[0020] The evaluation device can be configured to determine the leakage reactance and / or the leakage inductance of the transformer as a function of the test response and as a function of a reactance and / or an inductance of at least one line connecting the further terminals to the high-voltage side.

[0021] The evaluation device can be configured to automatically determine the reactance and / or the inductance of the at least one line.

[0022] The device may be configured to determine the reactance and / or the inductance of the at least one line without rewiring between the device and the transformer.

[0023] The evaluation device can be configured to determine from the test response a total reactance caused by the lines and the leakage reactance of the transformer, and to determine the leakage reactance from the total reactance and the reactance of the at least one line.

[0024] The evaluation device can be configured to determine a short-circuit impedance of the transformer depending on the test response of the transformer.

[0025] The evaluation device can be configured to determine the short-circuit impedance of the transformer as a function of the test response and as a function of an impedance of at least one line connecting the further terminals to the high-voltage side.

[0026] The evaluation device can be configured to determine from the test response a total impedance caused by the lines and the stray impedance of the transformer, and to determine the stray impedance from the total impedance and the impedance of the at least one line.

[0027] The device can be configured to determine a transformation factor of the transformer. The evaluation device can be configured to determine the leakage reactance as a function of the transformation factor.

[0028] The device may include a user interface. The evaluation device may be configured to determine the leakage reactance and / or the leakage inductance of the transformer in response to an input at the user interface.

[0029] The user interface can be configured to display an equivalent circuit diagram of the transformer via the user interface. The user interface can be configured to display the equivalent circuit diagram with information about the determined leakage reactance and / or leakage inductance.

[0030] The evaluation device can be configured to detect deviations from the nominal data of the transformer depending on the leakage reactance and / or the leakage inductance of the transformer. The nominal data can be stored in a non-volatile memory of the device or can be automatically retrieved by the device from a remote memory. Alternatively or additionally, the device can be configured to receive the nominal data via a user interface. The device can be configured to retrieve the nominal data depending on a user input specifying the type of transformer and to compare it with the determined leakage reactance and / or the leakage inductance of the transformer. The device can be configured to output information about a deviation between the nominal data and the determined leakage reactance and / or the leakage inductance of the transformer depending on the comparison.

[0031] The device can be designed as a mobile transformer testing device.

[0032] The device can be designed as a portable transformer testing device.

[0033] A system according to one embodiment includes a transformer having a high-voltage side and a low-voltage side. The system includes a device according to one embodiment connected to the transformer.

[0034] A method is provided for determining a characteristic of a transformer having a high-voltage side and a low-voltage side. The method comprises applying a test signal to the low-voltage side. The method comprises detecting a test response of the transformer. The method comprises determining a leakage reactance and / or a leakage inductance of the transformer as a function of the test response of the transformer.

[0035] The test signal can be an AC current signal or an AC voltage signal.

[0036] The method can be carried out by a device having terminals for detachable connection to the low-voltage side of the transformer for impressing the test signal and further terminals for detachable connection of the device to the high-voltage side of the transformer.

[0037] In the method, the device may comprise a measuring device coupled to the additional terminals for detecting the test response. The measuring device may comprise a voltmeter.

[0038] The method may comprise short-circuiting the high-voltage side by a controllable switching means of the device.

[0039] In the method, the controllable switching means can be integrated into a housing of the device. In the method, the controllable switching means can be a relay or another switch configured to switch a load circuit under the control of a control circuit. In the method, the controllable switching means can be an insulated-gate bipolar transistor (IGBT) or a field-effect transistor (FET), or can comprise an IGBT or a FET.

[0040] The method comprises controlling the controllable switching means such that the high-voltage side is short-circuited while the test signal is impressed on the low-voltage side.

[0041] In the method, the leakage reactance and / or the leakage inductance of the transformer can be determined as a function of the test response and as a function of a reactance and / or an inductance of at least one line connecting the further terminals to the high-voltage side.

[0042] In the method, the reactance and / or inductance of lines between the device and the transformer can be determined automatically by the device.

[0043] In the method, the reactance and / or the inductance of the at least one line can be determined without rewiring between the device and the transformer.

[0044] In the method, the device can determine a total reactance caused by the lines and the leakage reactance of the transformer from the test response. In the method, the device can determine the leakage reactance from the total reactance and the reactance of the at least one line.

[0045] In the method, the device can determine a short-circuit impedance of the transformer depending on the test response of the transformer.

[0046] In the method, the device can determine the short-circuit impedance of the transformer as a function of the test response and as a function of an impedance of at least one line connecting the further terminals to the high-voltage side.

[0047] In the method, the device can determine a total impedance caused by the lines and the stray impedance of the transformer from the test response. In the method, the device can determine the stray impedance from the total impedance and the impedance of the at least one line.

[0048] In the method, the device can determine a transformer's transmission factor. The leakage reactance can be determined as a function of the transmission factor, for example, by converting primed transformer characteristics into unprimed transformer characteristics.

[0049] The method may determine the leakage reactance and / or the leakage inductance of the transformer in response to an input at a user interface.

[0050] With this method, an equivalent circuit of the transformer can be displayed via the user interface. Optionally, a determined leakage reactance and / or leakage inductance can be displayed in the equivalent circuit.

[0051] The method can detect deviations from the transformer's nominal data depending on the transformer's leakage reactance and / or leakage inductance. The nominal data can be stored in a non-volatile memory of the device performing the test or can be automatically retrieved by the device from a remote memory. Alternatively or additionally, the nominal data can be received via a user interface to enable the user to enter the nominal data. The method can retrieve the nominal data depending on a user input specifying the type of transformer and compare it with the determined leakage reactance and / or leakage inductance of the transformer. Depending on the comparison, information about a deviation between the nominal data and the determined leakage reactance and / or leakage inductance of the transformer can be output.

[0052] The device with which the method is carried out can be designed as a mobile transformer testing device.

[0053] The device with which the method is carried out can be designed as a portable transformer testing device.

[0054] The method can be carried out by the device according to an embodiment.

[0055] Devices, methods, and systems according to embodiments allow for efficient determination of a transformer's leakage reactance and / or leakage inductance. Devices, methods, and systems according to embodiments allow for the determination of additional parameters during a test without having to rewire electrical lines between the device and the device under test. This allows the test to be performed more quickly. Devices, methods, and systems according to embodiments can be used to generate a low-resistance short circuit during at least part of a test to achieve an unadulterated test result. SHORT DESCRIPTION OF THE CHARACTERS

[0056] The invention will be explained in more detail below with reference to preferred embodiments and the drawings. In the drawings, identical reference numerals designate identical elements. Figure 1shows a system with a device according to an embodiment. Figure 2 shows a system with a device according to an embodiment. Figure 3 shows an equivalent circuit diagram of a transformer to explain the operation of the device according to an embodiment. Figure 4 shows an equivalent circuit diagram of a transformer to explain the operation of the device according to an embodiment. Figure 5 is a flowchart of a method according to an embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0057] The present invention will now be explained in more detail using preferred embodiments with reference to the drawings. In the figures, identical reference numerals designate identical or similar elements. The figures are schematic representations of various embodiments of the invention. Elements depicted in the figures are not necessarily drawn to scale. Rather, the various elements depicted in the figures are depicted in such a way that their function and purpose will be understood by those skilled in the art.

[0058] Connections and couplings between functional units and elements shown in the figures can also be implemented as indirect connections or couplings. A connection or coupling can be implemented wired or wirelessly.

[0059] The following describes in detail devices and methods for determining a characteristic value of a transformer. The transformer can be a transformer for high- or medium-voltage networks. The transformer can be a transformer installed in a power plant or substation. The device can be a mobile device that allows measurements to be performed on the installed transformer.

[0060] The device is configured to determine the leakage reactance and / or leakage inductance of the transformer. For this purpose, a test signal, such as an alternating current, is fed into the secondary side. The device can detect a test response. The phase position of the test response relative to the test signal can be evaluated to determine the leakage inductance. The test response can be evaluated automatically by an evaluation unit of the device.

[0061] In devices and methods, the reactance and / or inductance of at least one line between the device and the transformer can be taken into account to determine the leakage reactance and / or leakage inductance of the transformer. The test response can, for example, comprise a first detected voltage and a second detected voltage. From the magnitude and phase position of the first detected voltage and the second detected voltage, both the reactance and / or inductance of the line between the device and the transformer and the leakage reactance and / or leakage inductance of the transformer can be determined.

[0062] The device can automatically determine other transformer parameters. For example, the device can be configured to automatically determine a transformer's transformation ratio. The transformation ratio can be used to calculate the leakage reactance and / or leakage inductance, for example, to convert so-called primed parameters into unprimed parameters of the transformer. The corresponding computational processing can be performed automatically by the device's evaluation unit.

[0063] Figure 1 shows a system 1 with a device 10 for determining a characteristic of a transformer 40 according to an embodiment.

[0064] The system 1 comprises a transformer 40 and the device 10. The device 10 can be configured as a single device with a housing 11. The device 10 can consist of an arrangement of multiple devices or devices. In this case, the multiple devices or devices can be controlled by a central controller. The device 10 can be configured as a mobile device and, in particular, as a portable device. If the device 10 consists of multiple devices, each of the devices can be configured as a portable device.

[0065] The transformer 40 can be a power transformer of an electrical power supply facility. The transformer 40 can be permanently installed in a power plant or substation while a transformer test is being carried out using the device 10. The transformer 40 can be a voltage transformer or a current transformer. The transformer 40 can be a voltage transformer or a current transformer that operates according to the inductive principle.

[0066] The transformer 40 comprises at least one first winding 42 and at least one second winding 44. The at least one first winding 42 can be provided on a high-voltage side 41 of the transformer 40. The at least one second winding 44 can be provided on a low-voltage side 43. The transformer 40 can optionally also have a tertiary winding.

[0067] The device 10 comprises a plurality of terminals 12 for connection to the transformer 40, a source 13 for a test signal that is applied or impressed on the transformer 40 as the test object during the transformer test, and an evaluation device 18. One or more measuring devices 14, 16 for detecting a test response of the transformer 40 can be integrated into the device 10.

[0068] The plurality of terminals 12 includes terminals 31 configured for coupling to the low-voltage winding 44 of the transformer 40. The source 13 is coupled to the terminals 31 to apply the test signal to the low-voltage side 43. The plurality of terminals 12 includes further terminals 33, 34 configured for coupling to the high-voltage winding. The measuring device 14 can be connected to the low-voltage side 43 via lines 36. The measuring device 16 can be connected to the high-voltage side 41 via lines 38. The connection between the device 10 and the transformer 40 can be detachable to enable determination of parameters in the field.

[0069] The evaluation device 18 is configured to evaluate the test response of the transformer 40 in order to determine a leakage reactance and / or a leakage inductance of the transformer 40, as will be described in more detail below.

[0070] Source 13 can be a current source that can be controlled to generate an alternating current as a test signal. Source 13 can be controllable to generate alternating currents with several different frequencies as a test signal. Source 13 can also be a voltage source. Source 13 can be operated in different modes, for example, as a current source or as a voltage source and / or as a source of a temporally constant signal or an alternating signal. The test signal generated by source 13 can be impressed on the low-voltage side 43 via terminals 13 and lines 35.

[0071] The device 10 may comprise further devices. The device 10 comprises a control device 17 for automatically electrically controlling the source 13. The first measuring device 14 and the second measuring device 16 may, for example, each be configured for a voltage measurement. The functions of the control device 17 and / or the evaluation device 18 can be performed by a processor 19 or another integrated semiconductor circuit 19.

[0072] The device 10 comprises a controllable switching means 15. The controllable switching means 15 can be configured to selectively short-circuit the high-voltage winding 42. In this way, the test response of the transformer for a short circuit on the high-voltage side 41 can be detected. The test response can also be detected both for a short circuit on the high-voltage side 41 and, in idle mode, for an open switch 15. The controllable switching means 15 is automatically controlled by the control device 18. The controllable switching means 15 can be conductively connected to the high-voltage winding 42 via additional terminals 33 and lines 37 between the additional terminals 33 and the high-voltage winding 42.The controllable switching means 15 may be a conventional switch, a mechanical-electrical switch, a relay, a FET, an IGBT or another component which is suitable for establishing an electrically conductive connection between the terminals 33 depending on a state of the switching means 15.

[0073] The device 10 can determine the leakage reactance and / or leakage inductance of the transformer 40 in various ways. The control device 17 controls the source 13 so that the test signal is impressed on the low-voltage side 43. The test signal can be an alternating current signal. Different frequencies of the alternating current signal can be set sequentially, either user-defined or automatically.

[0074] The device 10 can determine the amplitude and phase position of a test response of the transformer 40. For example, a measuring device 14 can detect a voltage on the low-voltage side 43 as a first test response. A further measuring device 16 can detect a voltage on the high-voltage side 41 as a second test response. The device 10 can determine the phase position of both the first test response and the second test response relative to the test signal from the source 13. This can be carried out in different ways. For example, a time interval between zero crossings of the test signal and the test responses can be detected. A time interval between a zero crossing of the test signal and a zero crossing of a reference signal can be determined, and further time intervals between a zero crossing of each of the test responses and the reference signal can be determined.The phase angle can be determined from the time intervals and the frequency of the reference signal. Alternatively or additionally, multiplication of the test signal and test response in combination with time averaging can be used to determine the phase angle from the time average and the amplitudes of the multiplied signals.

[0075] The device 10 can automatically determine the amplitude of one or more test responses. The evaluation device 18 can calculate a quotient of the amplitude of a test response and the test signal amplitude.

[0076] The evaluation device 18 can determine the total longitudinal reactance of the transformer from the phase shift of the first test response relative to the test signal, the phase shift of the second test response relative to the test signal, and the amplitudes of the first and second test responses. The evaluation device 18 can determine the total longitudinal reactance as a primed characteristic of the transformer 40. The evaluation device 18 can optionally be configured to determine the total longitudinal reactance as an unprimed characteristic by scaling with the square of the transformation ratio of the transformer 40.

[0077] In one embodiment, as described with reference to Figure 4As will be described in more detail, the evaluation device 18 can be configured to determine a total impedance, which is the sum of the longitudinal impedance of the transformer and the impedance of the lines 37, from the phase position and amplitude of the voltage detected by the evaluation device 14. The evaluation device 18 can be configured to determine the impedance of the lines 37 from the phase position and amplitude of the voltage detected by the evaluation device 16. The evaluation device 18 can be configured to determine the total longitudinal reactance of the transformer 40 as the difference between the imaginary part of the total impedance and the imaginary part of the impedance of the lines 37. The evaluation device 18 can be configured to convert the total longitudinal reactance thus determined into an unbiased characteristic of the transformer by scaling with the square of the transformation ratio.

[0078] In a further embodiment, the evaluation device 18 can be configured to determine the total longitudinal reactance of the transformer 40 from the total impedance and the total resistance. The total resistance can be determined by a static resistance measurement or by evaluating the first and second test responses.

[0079] The evaluation device 18 can be configured to determine the total leakage inductance of the transformer 40. To do so, the evaluation device 18 can divide the leakage reactance by the angular frequency of the test signal.

[0080] The device 10 can be configured to automatically determine a transformation ratio of the transformer 40 and to consider it as an unbiased parameter when calculating the leakage reactance or leakage inductance. For example, the source 13 can be operated as an AC voltage source and the voltage on the high-voltage side 41 can be measured to determine the transformation ratio of the transformer. Other techniques can be used to determine the transformation ratio.

[0081] The device 10 may include a user interface 20. The user interface 20 may be a graphical user interface 20 configured to allow user-defined definition of measurements performed by the device 10. The source 13 and / or the controllable switching means 15 may be operated in a time-dependent manner to determine the leakage reactance and / or the leakage inductance of the transformer 40.

[0082] The device 10 can be configured such that different measurements can be performed without the connections 35-38 between the device 10 and the transformer 40 having to be disconnected and / or reconnected. The different measurements can be carried out without the device under test having to be rewired. The measurements can be performed by the device 10 fully or partially automated, i.e., without user interaction between measurements. In this way, for example, both the leakage reactance and / or the leakage inductance of the transformer 40 can be determined and at least one further characteristic, for example a dynamic or static resistance, can be recorded.

[0083] The device 10 can be configured to perform the multiple different measurements sequentially, wherein the measurements and optionally also their sequence can be user-defined via the interface 20. For example, an equivalent circuit diagram of the transformer 40 can be displayed via the interface 20, in which the user can select which parameters are to be measured. Alternatively or additionally, the evaluation device 18 can control the interface 20 such that an equivalent circuit diagram of the transformer 40 is displayed, in which the determined leakage reactance and / or leakage inductance of the transformer 40 is specified.

[0084] While in Figure 1a device 10 is shown in which the controllable switching means 15 is integrated into the device 10, the determination of the leakage reactance and / or the leakage inductance of the transformer 40 can also be carried out in an embodiment which does not fall under the invention if the device 10 does not have a controllable switching means for short-circuiting the high-voltage side 41.

[0085] The device 10 can be configured to perform further processing steps depending on the determined leakage reactance and / or leakage inductance. For example, the device 10 can be configured to detect deviations from the nominal data of the transformer 40. The nominal data can be stored non-volatilely in a memory of the device 10. The nominal data can be automatically retrieved by the device 10 from a remote memory, for example via a wireless or wired wide area network or local area network. Alternatively or additionally, the device 10 can be configured to receive the nominal data via the interface 20. The device 10 can be configured to retrieve the nominal data depending on a user input specifying the type of transformer and to compare it with the determined leakage reactance and / or leakage inductance of the transformer 40.The device 10 can be configured to output information about a deviation between the nominal data and the determined leakage reactance and / or the leakage inductance of the transformer 40 depending on the comparison.

[0086] Figure 2 is a representation of a system 1 with a device 10 according to a further exemplary embodiment. The device 10 may, but need not, have a controllable switching means 15 for short-circuiting the high-voltage side 41, whereby the device 10 only falls within the scope of the invention if it has such a switching means 15. To determine the leakage reactance and / or leakage inductance, the high-voltage winding 42 can be short-circuited with a line 39 so that the short circuit does not pass through the device 10.

[0087] The further design and functioning of the device 10 can be described as described with reference to the device 10 of Figure 1 be described.

[0088] The device 10 can comprise a reference signal source 21. The reference signal source 21 can generate a sinusoidal or other alternating signal with a frequency corresponding to the frequency of the test signal generated by the source 13. The evaluation device 18 can determine a phase shift or a time offset between the test response and the test signal by determining the phase position of the test signal relative to the reference signal of the reference signal source 21 and by determining the phase position of the test response relative to the reference signal of the reference signal source 21.

[0089] Figure 3 and Figure 4 show equivalent circuit diagrams to explain the functioning of the device according to an embodiment.

[0090] Figure 3shows an equivalent circuit diagram of the transformer 40. The winding resistance R 1 of the high-voltage side 41 can be represented by a resistor 51. The transformed winding resistance R 2 ' of the low-voltage side 43 can be represented by a resistor 54. The leakage inductance L σ1 of the high-voltage side 41 can be represented by an inductance 52. The transformed leakage inductance L σ2 ' of the low-voltage side 43 can be represented by an inductance 53. The resistors 51, 54 and inductors 52, 53 define the total series inductance of the transformer. The inductors 52, 53 define the untransformed, i.e. unprimed, total stray inductance, which can be converted into a primed characteristic of the transformer by scaling with the square of the transformation ratio in a manner known per se.

[0091] A main inductance carrying the magnetizing current can be taken into account by an inductor 55. A linear modeling of losses in the transformer core can be achieved by a resistor 56.

[0092] The device according to one embodiment is configured to impress the test signal on the low-voltage side and to determine at least the total longitudinal reactance and / or the total leakage inductance of the transformer 40 depending on the test response.

[0093] Figure 4 shows an equivalent circuit diagram to further explain the functioning of the device 10 according to embodiments.

[0094] The device 10 feeds the test signal from source 13 to the low-voltage side of the transformer. A voltmeter 65 or other voltage measuring device can detect a voltage VL on the low-voltage side as a first test response. A voltmeter 66 or other voltage measuring device can detect a voltage VH on the high-voltage side as a second test response. The first and second test responses can be evaluated, for example, as described above, to determine the leakage reactance and / or leakage inductance of the transformer 40.

[0095] In Figure 4 The total transformed series impedance is represented by resistor 61 and inductance 62. The lines 37 between the device 10 and the transformer 40 have a line impedance to which a line resistance 63 and a line inductance 64 may contribute.

[0096] By evaluating the phase position and amplitude of the voltage VH on the high-voltage side relative to the test signal and by evaluating the phase position and amplitude of the voltage VL on the low-voltage side relative to the test signal, the total transformed series resistance 61 and the total transformed series reactance, which is proportional to the total transformed leakage inductance 62, can be determined. For example, the total impedance can be determined from the phase position and amplitude of the voltage VH on the high-voltage side relative to the test signal. The line impedance can be determined from the phase position and amplitude of the voltage VH on the high-voltage side relative to the test signal. The transformed leakage reactance can be determined as the difference between the imaginary parts of the total impedance and the line impedance.By scaling with the square of the transformation ratio, the leakage reactance can be determined as a non-scalar characteristic of the transformer.

[0097] The evaluation and calculation steps for determining the leakage reactance can be carried out automatically by the evaluation device 18.

[0098] Figure 5 is a flowchart of a method 70 according to one embodiment. The method 70 can be executed automatically by the device 10 according to one embodiment.

[0099] In step 71, a line impedance and / or line reactance of at least one line between the device 10 and the transformer 40 can be determined. For this purpose, the source 13 can generate a test signal.

[0100] In step 72, a test signal generated by source 13 is impressed on the low-voltage side of transformer 40. The test signal may be an alternating current signal.

[0101] At step 73, a test response of the transformer may be acquired. The test response may include an AC voltage across a high-voltage winding and another AC voltage across a low-voltage winding, which are acquired over time.

[0102] In step 74, the leakage reactance and / or the leakage inductance of the transformer 40 are determined. The determined leakage reactance and / or the leakage inductance may correspond to the total series reactance or the total leakage inductance of the transformer.

[0103] Method 70 may include further steps. For example, a transmission ratio may be determined automatically. The transmission ratio may be used to convert transformed parameters into untransformed parameters.

[0104] The method 70 may include the evaluation of a user input with which it is possible to user-defined which characteristics of the transformer 40 are determined.

[0105] The method 70 may include controlling a graphical user interface such that the determined leakage reactance and / or leakage inductance is displayed.

[0106] While embodiments have been described in detail with reference to the figures, alternative or additional features may be used in further embodiments. For example, while certain processing steps for determining the leakage reactance and / or leakage inductance have been described by way of example, other processing techniques may be employed. For example, the leakage reactance and / or leakage inductance may be determined by solving a system of matrix equations for elements of a mapping matrix that maps the sine and cosine components of the test signal into corresponding components of one or more test responses.

[0107] While in embodiments, the device may comprise a controllable switching means for short-circuiting a winding of the transformer, it may also comprise two or more than two controllable switching means for short-circuiting multiple windings of the transformer, or it may not comprise any such controllable switching means. The device may be configured to short-circuit multiple windings simultaneously or sequentially.

[0108] While in embodiments a procedure involving the determination of multiple characteristics of the transformer may be carried out automatically, the apparatus and method according to embodiments may also be used if only one characteristic of the transformer, for example only the leakage reactance, is measured before a new user input is required.

[0109] While the transformer can be installed in a power plant or substation of a power supply network, the device and the method according to embodiments can also be used for smaller transformers.

[0110] Devices, methods and systems according to embodiments allow determination of parameters such as leakage reactance and / or leakage inductance with further automation in transformer testing.

Claims

1. An apparatus (10) for determining a parameter of a transformer (40) which has a high-voltage side (41) and a low-voltage side (43), the apparatus (10) comprising terminals (31) for detachably connecting the apparatus (10) to the low-voltage side (43) of the transformer (40), further terminals (33, 34) for detachably connecting the apparatus (10) to the high-voltage side (41) of the transformer (40), a controllable switching means (15) connected to the further terminals (33, 34) for short-circuiting the high-voltage side (41), a source (13) for generating a test signal, coupled to the terminals (31), for impressing the test signal on the low-voltage side (43) of the transformer (40), a control device (17) configured to automatically control the source (13) and the controllable switching means (15) such that the high-voltage side (41) is short-circuited by the controllable switching means (15) while the test signal from the source (13) is impressed on the low-voltage side (43), and an evaluation device (18) which is configured to determine the leakage reactance and / or the leakage inductance of the transformer (40) on the basis of the test response of the transformer (40), which is detected while the high-voltage side (41) is short-circuited by the controllable switching means (15) and the test signal from the source (13) is impressed on the low-voltage side (43), wherein the evaluation device (18) is further configured to automatically identify a deviation from nominal data of the transformer (40) on the basis of the determined leakage reactance and / or the leakage inductance of the transformer (40) by comparing the determined leakage reactance and / or leakage inductance with the nominal data.

2. The apparatus according to claim 1, comprising a measuring device (16) coupled to the further terminals (33, 34) for detecting the test response.

3. The apparatus according to claim 1 or claim 2, wherein the evaluation device (18) is configured to determine the leakage reactance and / or the leakage inductance of the transformer (40) on the basis of the test response and on the basis of a reactance and / or an inductance of at least one line (37) connecting the further terminals (33) to the high-voltage side (41).

4. The apparatus according to claim 3, wherein the evaluation device (18) is configured to automatically determine the reactance and / or the inductance of the at least one line (37).

5. The apparatus according to claim 3 or claim 4, wherein the apparatus (10) is configured to determine the reactance and / or the inductance of the at least one line (37) without rewiring between the apparatus (10) and the transformer (40).

6. The apparatus according to any one of claims 1 to 5, wherein the evaluation device (18) is further configured to determine a short-circuit impedance of the transformer (40) on the basis of the test response of the transformer (40).

7. The apparatus according to claim 6, wherein the evaluation device (18) is configured to determine the short-circuit impedance of the transformer (40) on the basis of the test response and on the basis of an impedance of at least one line (37) connecting the further terminals to the high-voltage side (41).

8. The apparatus according to any one of the preceding claims, comprising a user interface (20), wherein the evaluation device (18) is configured to determine the leakage reactance and / or the leakage inductance of the transformer (40) in response to an input at the user interface (20).

9. A system comprising a transformer (40) having a high-voltage side (41) and a low-voltage side (43), and an apparatus (10) according to any one of the preceding claims, connected to the transformer (40).

10. A method for determining a parameter of a transformer (40) which has a high-voltage side (41) and a low-voltage side (43), comprising automatically short-circuiting the high-voltage side (41) of the transformer (40) by means of a controllable switching means (15), automatically impressing a test signal on the low-voltage side (43) while the high-voltage side (41) is short-circuited by the controllable switching means (15), detecting a test response of the transformer (40) while the high-voltage side (41) is short-circuited by the controllable switching means (15) and the test signal is impressed on the low-voltage side (43), determining a leakage reactance and / or a leakage inductance of the transformer (40) on the basis of the test response of the transformer (40), and automatically identifying a deviation from nominal data of the transformer (40) on the basis of the determined leakage reactance and / or leakage inductance of the transformer (40) by comparing the determined leakage reactance and / or leakage inductance with the nominal data.

11. The method according to claim 10, which is carried out with the apparatus (10) according to any one of claims 1 to 8.