Method and apparatus for personnel protection during high voltage testing

Abstract

The present invention relates to a method for personnel protection during high-voltage testing on a test object (300), the method comprising: outputting (701) a high-voltage alternating current to the test object (300) by means of a high-voltage generating device (200), the high-voltage generating device having a high-voltage transformer (201) for generating the high-voltage alternating current. The method further comprises the steps of: determining a time curve of at least one electrical variable at the high-voltage transformer (201) during the output of the high-voltage alternating current, and terminating the output of the high-voltage alternating current according to the time curve of the at least one electrical variable.

Description

Technical Field

[0001] The present invention relates to a method for personnel protection during high-voltage testing on a test object, and a high-voltage generating device operating according to the method for personnel protection. Background Technology

[0002] High-voltage insulation measurements (such as capacitance and loss factor measurements) are established methods for testing the condition of high-voltage equipment (i.e., transformer insulation or bushing insulation). High test voltages of several thousand volts (e.g., 10 kV), especially high AC voltages, are used in this context. Measurement currents can reach several hundred mA, for example, up to 300 mA.

[0003] Suitable measuring equipment is typically constructed to protect users from high test voltages (e.g., through proper insulation of the measuring equipment and the measuring circuitry used). However, there may be uninsulated or poorly insulated components on the test piece itself (e.g., on transformers or some other high-voltage equipment) that are subjected to high voltage during testing. To protect personnel from electrical hazards during measurement, it is necessary to make the test area inaccessible and to provide warning signals, such as visual warning signals with red lights or flashing lights, and audible warning signals (e.g., loud warning sounds). Therefore, personnel protection is based on the assumption that all personnel involved in the test and all personnel within the test area know and comply with appropriate safety regulations. Despite these safety regulations, accidents frequently occur, for example, if they are not followed or circumvented. Because of the use of high voltage during testing, contact with live parts poses a significant risk to human life. Summary of the Invention

[0004] Therefore, there is a need in the existing technology to improve personnel protection during high-voltage testing or measurement.

[0005] According to the present invention, a method for personnel protection during high-voltage testing on a test object and a high-voltage generating device for performing high-voltage testing on a test object are provided, according to the independent claim. The dependent claims define preferred or advantageous embodiments of the invention.

[0006] A method for personnel protection during high-voltage testing on a test object includes: outputting a high-voltage alternating current to the test object using a high-voltage generating device. The high-voltage generating device has a high-voltage transformer for generating the high-voltage alternating current. For example, the high-voltage alternating current can be used to perform high-voltage insulation measurements on the test object. The high-voltage alternating current can have a voltage, for example, from 2kV to 12kV. Furthermore, in this method, a time curve of at least one electrical variable on the high-voltage transformer is determined simultaneously with the output of the high-voltage alternating current. For example, the time curve of at least one electrical variable can be measured directly on the high-voltage transformer, or it can be determined from one or more measurements on the high-voltage transformer using a control device or processing device. The output of the high-voltage alternating current is terminated based on the time curve of at least one electrical variable.

[0007] For example, the time curves of one or more electrical variables (e.g., current, voltage, power, phase angle, or impedance) on a test object (e.g., a high-voltage transformer or high-voltage bushing) differ from the corresponding time curves of one or more electrical variables flowing through a human body. This allows observation of the time curves to identify whether a person has been in contact with a high-voltage alternating current. If such contact is identified in this way, the high-voltage alternating current can be interrupted to protect the person from injury. In this case, prompt interruption is crucial because the length of exposure time to the high-voltage alternating current significantly impacts the potential severity of injury. For instance, with a current flow of 200 mA and an exposure time of less than 300 ms, reversible muscle contractions are typically observed, while longer exposure times and higher current flows may produce irreversible effects and significantly increase the likelihood of ventricular fibrillation.

[0008] For example, a high-voltage transformer can have an input side with an input winding and an output side with an output winding. A high-voltage alternating current is output to the test object at the output winding. A time curve of at least one electrical variable is determined by detection on the input side of the high-voltage transformer. The output of the high-voltage alternating current is terminated based on the time curve of the at least one electrical variable determined in this way. The voltage present on the input winding of the high-voltage transformer is typically significantly lower than the voltage present on the output winding. Compared to the output side, current and voltage measurements on the input side can be performed more cost-effectively and, especially, more quickly, due to the lower voltage. However, the electrical variables on the input and output windings of the high-voltage transformer are directly interdependent, allowing the electrical variables on the output winding to be derived from those on the input winding. As a result, it is possible to quickly identify whether a person has come into contact with the high-voltage alternating current, thus enabling rapid disconnection. The relationship between the electrical variables on the input and output windings is determined by the characteristics of the high-voltage transformer. Therefore, it is also possible to disconnect the high-voltage alternating current based on at least one characteristic of the high-voltage transformer. In other words, when deciding whether to continue outputting or cut off the high-voltage alternating current, it is possible to detect the electrical changes on the input winding and deduce the corresponding electrical changes on the output winding by means of the characteristics of the high-voltage transformer.

[0009] According to one embodiment, at least one electrical variable includes the phase and absolute value of the current on the high-voltage transformer and the phase and absolute value of the voltage on the high-voltage transformer. In this method, the phase angle between the current and voltage on the high-voltage transformer can also be determined based on their phases. If the phase angle is less than a predefined phase angle threshold, the output of the high-voltage alternating current is terminated. The phase angle threshold can be, for example, 80° to 89°, preferably, for example, 80° or 85°. For example, if the phase angle is less than 80°, the high-voltage alternating current can be disconnected. When the insulation of the insulation measurement and the test piece or object is substantially intact, the test piece essentially constitutes a capacitive load, such that the phase angle between the current and voltage is almost 90°. In this case, the current lags the voltage by almost 90°. If a person comes into contact with the high-voltage alternating current, the phase angle decreases because the person constitutes a resistive load. If a corresponding change in the phase angle between the current and voltage is established, the high-voltage alternating current can be disconnected to protect the person.

[0010] Alternatively or additionally, the loss factor can be determined based on the phase angle of the current and voltage. If the loss factor is greater than a predefined loss factor threshold, the output of the high-voltage AC current is terminated. The loss factor threshold can have a value of, for example, 0.5% to 10%, preferably 5% or 10%. The loss factor is equal to the tangent of the loss angle, which in the case of a capacitor corresponds to 90° minus the phase angle.

[0011] In another embodiment, the impedance of the load connected to the high-voltage transformer is determined based on the absolute values ​​and phases of the current and voltage. If the impedance is less than a predefined impedance threshold, the output of the high-voltage alternating current is terminated. The impedance threshold can be, for example, from 30 kΩ to 70 kΩ, and is preferably 50 kΩ. In high-voltage equipment with substantially normal insulation, the impedance is typically significantly higher than 50 kΩ, and often exceeds 70 kΩ. Therefore, a lower impedance indicates an insulation defect in the high-voltage equipment, or indicates that personnel have come into contact with the high-voltage alternating current. Thus, disconnection in this situation can effectively protect personnel from electric shock and its consequences.

[0012] In another embodiment of the method, a time curve of the power output by the high-voltage transformer is determined. The power output by the high-voltage transformer is determined based on the time curve of the absolute values ​​and phases of the current and voltage. For example, the effective value (rms value) of the power output by the high-voltage transformer can be determined. If the change in output power exceeds a predefined power change value within a predefined time period, the output of the high-voltage alternating current is terminated. For example, the power change value can be a relative value, such as 10% to 30%, preferably, for example, 20%. The predefined time period can be a few milliseconds, such as 10ms to 300ms, preferably 200ms. In other words, if, for example, it is determined that the power output by the high-voltage transformer increases by more than, for example, 200ms, the high-voltage alternating current is cut off. Assuming that the voltage output by the high-voltage transformer does not increase within the predefined time period, such an increase in output power can indicate that a person has touched a live part, causing an additional current to flow through the person, thus increasing the output power. By detecting such a power increase within a relatively short time period of, for example, 200ms, the high-voltage alternating current can be quickly cut off, so that the person is exposed to the high-voltage alternating current for only a very short period of time.

[0013] In another example, the output of the high-voltage alternating current is terminated if the absolute value of the current exceeds a predefined current threshold. The current threshold can be from 100mA to 300mA, and is preferably 200mA. For example, the current can be the effective value of the current. As mentioned above, exposure to a 200mA current over a 300ms time period generally does not cause any irreversible damage, and the likelihood of ventricular fibrillation is relatively low.

[0014] If, within a predefined time period, the change in the absolute value of the current over time exceeds a predefined current change value, the output of the high-voltage AC current can also be terminated. The predefined time period can be from 10 ms to 300 ms, and is preferably 200 ms. The current change value can be a relative value and, for example, can be 10% to 20%. In this example, if the current increases by more than 20% within, for example, 200 ms, the high-voltage AC current is therefore interrupted. For example, the current can be the effective value of the current. This sudden increase in current occurs if a person touches a live component. Therefore, interrupting the high-voltage AC current in this situation reduces harm to personnel.

[0015] In another embodiment, if the absolute value of the voltage does not reach a predefined minimum voltage during the output of high-voltage AC current to the test object, the output of the high-voltage AC current is terminated. The minimum voltage can be, for example, 1kV to 10kV. The reason for not reaching the predefined minimum voltage may be, on the one hand, that the test object lacks sufficient insulation, and on the other hand, that a person may come into contact with a live part, allowing current to flow through them. Since the performance of the high-voltage transformer is limited, this current limits the maximum output voltage. Therefore, disconnecting the current in these situations helps protect personnel.

[0016] If, within a predefined time period, the change in the absolute value of the voltage over time exceeds a predefined voltage change value, the output of the high-voltage AC current can also be terminated. For example, the voltage change value can be the absolute value or percentage value of the voltage at the start of the predefined time period. For instance, the voltage change value could be -10% to -20%, meaning that if the voltage changes by, for example, 10% or 20% within the predefined time period, the high-voltage AC current is cut off. If a person touches a live component during high-voltage testing, the additional current from the person can significantly increase the current output by the high-voltage transformer, causing a voltage drop due to the limited performance of the high-voltage transformer. Therefore, cutting off the high-voltage AC current can reduce harm to personnel in this situation.

[0017] In another embodiment, a high-voltage alternating current is output in the absolute value of a continuously increasing or staged voltage increase. For example, the high-voltage alternating current can start from a low voltage on the order of, for example, 25V or 100V and continuously or stagedly increase to a final voltage. The high-voltage alternating current can increase from, for example, a low voltage of 1kV to a final voltage of, for example, 12kV, for example, within a time period of a few seconds, for example, 1 to 5 seconds, preferably 3 seconds, from 1kV to 12kV in stages. Combined with the above-described protection mechanism that identifies personnel touching live parts and then cuts off the high-voltage alternating current, harm to personnel can be further reduced because the cut-off can be performed before reaching, for example, the full measured voltage of 12kV.

[0018] A high-voltage generating device for performing high-voltage testing on a test object includes a high-voltage transformer, an output terminal, and a control device. The high-voltage transformer generates a high-voltage alternating current. A high-voltage alternating current is supplied to the test object at the output terminal. The control device is designed to protect personnel during high-voltage testing by outputting the high-voltage alternating current to the test object via the output terminal and simultaneously determining a time curve of at least one electrical variable on the high-voltage transformer. Based on the time curve of the at least one electrical variable, the control device terminates the output of the high-voltage alternating current. The high-voltage generating device is therefore suitable for performing the above-described method and thus also includes the advantages described in conjunction with the above-described method.

[0019] The high-voltage generating equipment or corresponding testing system can preferably be in the form of a portable device or unit. Attached Figure Description

[0020] The present invention will now be described in detail with reference to the accompanying drawings.

[0021] Figure 1 A high-voltage generating device according to an embodiment of the present invention is illustrated schematically.

[0022] Figure 2 The diagram schematically illustrates the time curves of two electrical variables on the high-voltage transformer of a high-voltage generating device according to an embodiment of the present invention.

[0023] Figure 3 Another time curve of two electrical variables on the high-voltage transformer of a high-voltage generating device according to an embodiment of the present invention is schematically shown.

[0024] Figure 4 A flowchart illustrating the steps of a method according to an embodiment of the present invention is shown. Detailed Implementation

[0025] The above-described features, characteristics, and advantages of the present invention, as well as the ways in which they are realized, become clearer and more apparent in conjunction with the following exemplary embodiments, which are described in more detail with reference to the accompanying drawings.

[0026] The invention will now be described in more detail with reference to the accompanying drawings and embodiments. In the drawings, the same reference numerals denote the same or similar elements. The drawings are schematic illustrations of different embodiments of the invention. Elements shown in the drawings are not necessarily shown to scale. The various elements shown in the drawings are described such that their function and general purpose will be understood by those skilled in the art. The connections and couplings shown in the drawings between functional units and elements can also be implemented as indirect connections or couplings. Functional units can be implemented as hardware, software, or a combination of hardware and software.

[0027] Figure 1A test object or measurement object 300 connected to a high-voltage AC voltage testing device 100 and personnel 400 are shown. The test object 300 (also referred to as the test piece) includes high-voltage equipment (i.e., a transformer, high-voltage switch, or high-voltage bushing). The high-voltage AC voltage testing device 100 is designed to perform high-voltage insulation measurements on the test object 300. For this purpose, a test voltage of several kilovolts, for example 2kV to 12kV, is applied to the test object 300, and the resulting current flowing through the test object 300 is determined. The insulation quality of the test object 300 relative to ground or another conductor can be determined using the current and voltage. For this purpose, the high-voltage AC voltage testing device 100 has, for example, a current measuring device 102 and a voltage measuring device 103, which measure the current fed into the test object 300 or the voltage present at the test object 300. To obtain a high-quality report on the insulation of the test object, the measuring devices 102, 103 are highly accurate and detect electrical signals (e.g., current and voltage) directly connected to the test object 300. For this purpose, current and voltage can be sampled, for example, at a sampling rate significantly higher than the frequency of the high-voltage AC current fed into the test object 300. In the processing device 101 of the high-voltage AC voltage test equipment 100, the sampled current and voltage signals are processed and, for example, the insulation resistance is determined and output to the user.

[0028] The high-voltage AC voltage testing apparatus 100 also includes a high-voltage generating device 200 for generating a high-voltage AC current to be fed into the test object 300. The high-voltage generating device 200 includes a high-voltage transformer 201, which is coupled to the test object 300 via an output terminal 202 at its output winding on the output side 211. On the input side 210, the input winding of the high-voltage transformer 201 is connected to an energy supply device (e.g., an AC voltage supply network with a voltage of 110 to 240 V) via a switching device 204. The high-voltage transformer 201 is designed to provide a desired high-voltage AC current at its output winding for measurement based on the voltage supplied to the high-voltage transformer at the input winding. The high-voltage generating device 200 also includes a control device 203 and measuring devices 205, 206 (e.g., current measuring device 205 and voltage measuring device 206). Compared to measuring devices 102 and 103, measuring devices 205 and 206 are not designed for high precision but for rapid measurement. Measuring devices 205 and 206, like measuring devices 102 and 103, are capable of sampling current or voltage values ​​and providing these sampled values ​​to control device 203. The sampling rate of measuring devices 102 and 103 can be significantly higher than the voltage frequency on the input winding of the high-voltage transformer 201, for example, 10 to 100 times higher; that is, for example, a sampling rate of 500 to 5000 samples per second when the voltage frequency on the input winding is 50 Hz. Control device 203 is coupled to switching device 204 and is capable of switching the energy supply to the high-voltage transformer 201 on or off. High-voltage generating device 200 can include additional components to provide a high-voltage AC current with an adjustable voltage, for example, under the control of control device 203, to enable continuous or phased increases in the high-voltage AC current, for example, from 1 kV to 12 kV.

[0029] Figure 2A graph 500 is shown, showing the time curves for voltage 501 and current 502, as seen, for example, during insulation measurements on a high-voltage transformer 201 with a substantially capacitive load. In the case of a substantially capacitive load, there is a phase angle 503 of approximately 90° between the time curve for voltage 501 and the lag time curve for current 502. In typical insulation measurements of high-voltage equipment (i.e., high-voltage transformers or high-voltage bushings), there is capacitance, for example, up to 50 nanofarads, resulting in a maximum current of approximately 150 mA flowing at 12 kV. This corresponds to an impedance of approximately 60 kΩ to 70 kΩ. The loss factor is typically less than 10%, i.e., the loss angle is less than 6°, resulting in a phase angle greater than 84° between current and voltage. The loss factor, loss angle, and phase angle are directly related to each other. The loss factor is the tangent of the loss angle, and the loss angle in the case of a capacitive load is 90° minus the phase angle. Hereinafter, the loss factor will be considered primarily. However, it is clear that the same considerations apply to the phase angle and the loss angle.

[0030] If person 400 comes into contact with a live part of test object 300, an additional current can flow through person 400. Since the human body has inherent ohmic resistance, the phase angle, loss angle, and loss coefficient change. Furthermore, the impedance of the human body depends on the applied voltage, the contact surface, and the location of the contact point. As the voltage increases, the impedance decreases, and at a voltage of, for example, 1000V, it can have an absolute value of 700Ω to 1500Ω. Figure 3 A graph 600 shows a time curve for voltage 601 and a time curve for current 602, as it appears, for example, on a high-voltage transformer 201 during insulation measurements of test object 300 while simultaneously in contact with a person 400. The phase angle 603 between the time curve for voltage 601 and the lag time curve for current 602 is less than [missing value]. Figure 2 There is no phase angle of 50° where personnel 40° are in contact. The loss factor thus increases, typically by at least 10%.

[0031] In addition (but not in) Figure 3 As shown in the diagram, the absolute value of current 602 can be increased due to the overall lower impedance. As a result, the total power output at the output winding and subsequently consumed at the input winding of the high-voltage transformer 201 can also be increased. Furthermore, since the high-voltage transformer 201 itself has a specific internal resistance, voltage 601 can be reduced due to the lower impedance.

[0032] The above understanding can be used to improve personnel protection during high-voltage testing or measurement, especially high-voltage insulation measurement. In high-voltage testing, particularly in high-voltage insulation measurement, several thousand volts of voltage are applied to the object being tested. Measuring equipment that generates this high measurement voltage is typically designed to prevent contact with live parts. However, on the object being tested (e.g., a transformer or high-voltage bushing), voltage can also be present on exposed parts that personnel can touch. To avoid this, safety measures are typically implemented to prevent contact with live parts. These safety measures include, for example, making the measurement area inaccessible or providing visual and / or audible warnings. Despite these safety measures, accidents can still occur if, for example, safety regulations are not followed or are circumvented. If a person comes into contact with high voltage, the duration of exposure is crucial to the severity of injury. Therefore, it is important to identify as soon as possible that a person is touching a live part and, in such cases, to disconnect the voltage as quickly as possible.

[0033] Assessing the absolute values ​​and phases of the current and voltage at high-voltage transformer 201 allows control device 203 to determine, for example, whether the entire load is capacitively dominant when the loss factor is less than 10% and the load impedance is within the typical range of the test object rather than within the typical range of the body through which the current flows (e.g., when the impedance is >50kΩ). In this case, the measurement continues. However, if the loss factor is greater than, for example, 10%, or the impedance is within the range that can be caused by the current flowing through a person, for example, when the impedance is less than 50kΩ, the measurement is immediately interrupted. For this purpose, control device 203 can disconnect switching device 204 so that high-voltage transformer 201 does not provide any high-voltage AC current at output terminal 202. Furthermore, if the power consumed or output by the high-voltage transformer changes suddenly, the current suddenly increases or the voltage suddenly drops, the high-voltage AC current can be cut off. Detection and disconnection should be performed within a very short time after the current begins to flow through the person, preferably within 300ms, to avoid permanent damage. Therefore, in a preferred embodiment, the invention is designed such that the method includes detection and disconnection within 300ms. In many cases, the measurement of electrical variables on the output side 211 of the high-voltage transformer 201 (i.e., the high-voltage side of the high-voltage transformer 201), especially the time curves of these electrical variables, cannot be obtained quickly enough because these measurements are typically designed for accuracy rather than speed. Therefore, the corresponding variables are preferably measured on the input side 210 of the high-voltage transformer 201 (i.e., on the primary or low-voltage side of the high-voltage transformer 201), and by taking into account the characteristics of the high-voltage transformer 201 (e.g., internal losses), the corresponding values ​​on the output side 211 of the high-voltage transformer 201 are estimated, thereby enabling faster measurements. Once a body is detected to be in the circuit, current is cut off. This can be performed in a fully automated manner and thus very quickly, generally preventing relatively large personal injuries. Therefore, the correct operation of the measurement (i.e., the measurement without contact with live parts) is unaffected.

[0034] For example, Figure 4 Details of a corresponding method that can be executed in control device 203 are shown. For this purpose, control device 203 can include an electronic control unit (i.e., a processor, particularly a signal processor). However, the electronic control unit can also be implemented with a similar structure. Figure 4 The method 700 shown includes method steps 701 to 708. Although the method steps are... Figure 4 The steps are shown in a specific order, but can be performed in any other desired order or in parallel. In particular, steps 703 to 707 can be performed in any other desired order, or preferably in parallel in time.

[0035] At the start of the high-voltage test, in step 701, a high-voltage AC current is generated and output in the high-voltage AC voltage testing device 100. For this purpose, the switching device 204 is turned on, supplying electrical energy to the high-voltage transformer 201. The high-voltage transformer 201 generates a high-voltage AC current from the supplied electrical energy as a test voltage, which is output at output terminal 202. The test object 300 is connected to output terminal 202. For example, the high-voltage test can be a high-voltage insulation measurement, in which the insulation of the test object 300 is checked. For this purpose, while outputting a high-voltage AC current to the test object 300, the current and voltage of the high-voltage AC current are determined using measuring devices 102 and 103. To achieve accurate measurement results in the high-voltage insulation measurement, the current measuring device 102 and the voltage measuring device 103 are typically designed for very precise measurements rather than very fast measurements. In particular, the voltage measuring device 103 must be designed to be able to measure very high voltages of several thousand volts. Voltage measurements at such high voltages typically take longer than those at lower voltages (e.g., below 500V).

[0036] The high-voltage AC voltage testing equipment 100 also includes measuring devices (e.g., current measuring device 205 and voltage measuring device 206) on the input side 210 of the transformer 201. Measuring devices 205 and 206 can have lower accuracy than measuring devices 102 and 103, but can perform measurements much faster. For example, measuring devices 205 and 206 can provide current and voltage values ​​at a sampling rate of 500 to 5000 samples per second and a delay of only a few milliseconds (e.g., less than 100 ms). This sampling rate is significantly higher than the frequency of the high-voltage AC current, for example, 10 to 100 times higher. As a result, time curves of electrical variables, such as the time curves of current and voltage on the input side 210 of the high-voltage transformer 201, can be determined based on the sampled values ​​in step 702. For example, by considering the characteristics of the high-voltage transformer 201 (e.g., the turns ratio of the input winding to the output winding, internal losses, and transmission characteristics), the corresponding curves of electrical variables at the output 202 can be derived.

[0037] Then, in steps 703 to 707, the time curves of these electrical variables are evaluated. In this case, the time curves of the electrical variables on the input side 210 of the high-voltage transformer 201 can be used directly, or the time curves of the corresponding electrical variables at the output side 211 of the high-voltage transformer 201 can be used from them. The thresholds used in steps 703 to 707 must be adjusted accordingly.

[0038] In step 703, the phase of the current and voltage is evaluated. For example, based on the phase of the current relative to the voltage, the loss factor can be determined, and if the loss factor rises above a predefined threshold (e.g., exceeding 10%), the high-voltage AC current is interrupted in step 708. The control device 703 can accordingly actuate the switching device 204 to interrupt the high-voltage AC current in step 708.

[0039] Furthermore, in step 704, the impedance is determined, as seen from the output terminal 202 of the high-voltage AC current testing device 100. The impedance is determined by the test object 300 and may also be determined by personnel 400. If the impedance drops below a predetermined threshold, for example, below 50kΩ, then in step 708, the control device 203 can cut off the high-voltage AC current by actuating the switching device 204.

[0040] Furthermore, in step 705, the power output at output terminal 202 can be observed and estimated over time. For example, the power can be apparent power or active power. In the event of a sudden power change, in step 708, controller 203 can cut off the high-voltage AC current. For example, a sudden power change can be defined by the relative change in power over a predefined time period. For example, if the output power increases by more than 10% or 20% within 200 ms, it can be considered a sudden power change. This sudden increase can be caused by a person 400 touching a live component. Alternatively, instead of the power output at output terminal 202, the power consumed by high-voltage transformer 201 can also be determined, and taking into account the internal losses of high-voltage transformer 201, it can optionally be used as the criterion for cutting off the high-voltage AC current in the same manner.

[0041] Similarly, in step 706, the current output at output terminal 202 can be observed and estimated over time. For example, the current can be the effective value current (rms current). In the event of a sudden increase in current, in step 708, control device 203 can cut off the high-voltage AC current. For example, a sudden change in current can be defined by the relative change in current over a predefined time period. For example, if the current increases by more than 10% or 20% within a time period of 100 or 200 ms, it can be considered a sudden change in current. A sudden increase in current can be caused by personnel 400 coming into contact with a live component.

[0042] Similarly, in step 707, the voltage present at output terminal 202 can be observed and estimated over time. For example, the voltage can be the effective value voltage (rms voltage). In the event of a sudden voltage drop, in step 708, control device 203 can cut off the high-voltage alternating current. A sudden voltage drop can be caused by a person 400 touching a live part. Since the impedance of the person 400 is relatively low compared to the impedance of the insulation of the test object 300, the current will rise sharply, causing the high-voltage transformer 201 to be unable to maintain the output voltage due to its internal resistance or the corresponding protection circuit of the high-voltage transformer 201. Similarly, if the desired output voltage is not achieved when the high-voltage alternating current is connected, control device 203 can cut off the high-voltage alternating current.

[0043] If the evaluation of the time curve of the electrical variable in steps 703 to 707 does not cause the high-voltage AC current to be cut off in step 708, then method 700 continues with step 702 until the high-voltage AC current measurement is completed. Therefore, using the above method 700 can improve personnel protection during high-voltage AC current measurement.

[0044] Of course, the features of the above embodiments and aspects of the present invention can be combined with each other. In particular, without departing from the scope of the present invention, these features can be used not only in the described combinations, but also in other combinations or individually.

Claims

1. A method for personnel protection during high-voltage testing on a test object, the method comprising: - A high-voltage alternating current (701) is output to the test object (300) by means of a high-voltage generating device (200), the high-voltage generating device having a high-voltage transformer (201) for generating the high-voltage alternating current. - Determine the time curve of at least one electrical variable at the high-voltage transformer (201) of the high-voltage transformer (702) while outputting the high-voltage alternating current. -The output of high-voltage AC current ends (708) according to the time curve of the at least one electrical variable. The at least one electrical variable mentioned above includes the phase and absolute value of the currents (502, 602) on the high-voltage transformer (201) and the phase and absolute value of the voltages (501, 601) on the high-voltage transformer (201). The method further includes: - The impedance is determined based on the absolute value and phase of the current (502, 602) and the voltage (501, 601), wherein if the impedance is less than a predefined impedance threshold, the output of the high-voltage AC current is terminated.

2. The method according to claim 1, The high-voltage transformer (201) includes an input side (210) and an output side (211), at which a high-voltage alternating current is output to the test object (300). The time curve of the at least one electrical variable is determined by means of detection at the input side (210) of the high-voltage transformer (201), and The output of high-voltage AC current is terminated based on at least one characteristic of the high-voltage transformer (201).

3. The method according to claim 1, wherein the method further comprises: - Based on the phase of the currents (502, 602) and the voltages (501, 601), determine the phase angles (503, 603) between the currents (502, 602) and the voltages (501, 601) at the high-voltage transformer (201), wherein if the phase angles (503, 603) are less than a predefined phase angle threshold, the output of the high-voltage AC current is terminated.

4. The method according to claim 1, wherein the method further comprises: - The loss coefficient is determined based on the phase of the current (502, 602) and the voltage (501, 601), wherein if the loss coefficient is greater than a predefined loss coefficient threshold, the output of the high-voltage AC current is terminated.

5. The method according to claim 1, wherein the method further comprises: - The time curve of the power output by the high-voltage transformer (201) is determined based on the time curve of the absolute value and phase of the current (502, 602) and the voltage (501, 601), wherein if the change in the power output by the high-voltage transformer (201) exceeds the predefined power change value within a predefined time period, the output of the high-voltage AC current is terminated.

6. The method according to claim 5, wherein the predefined time period is from 0ms to 300ms.

7. The method according to claim 1, wherein if the absolute value of the current (502, 602) exceeds a predefined current threshold, the output of the high-voltage AC current is terminated.

8. The method according to claim 1, wherein if the change in the time curve of the absolute value of the current (502, 602) exceeds a predefined current change value within a predefined time period, the output of the high-voltage AC current is terminated.

9. The method according to claim 8, wherein the predefined time period is from 0 ms to 300 ms.

10. The method according to claim 1, wherein if the absolute value of the voltage (501, 601) does not reach a predefined minimum voltage during the output of high voltage AC current to the test object (300), the output of high voltage AC current is terminated.

11. The method according to claim 1, wherein if the change in the time curve of the absolute value of the voltage (501, 601) exceeds a predefined voltage change value within a predefined time period, the output of the high-voltage AC current is terminated.

12. The method according to claim 11, wherein the predefined time period is from 0 ms to 300 ms.

13. The method of claim 1, wherein the method is designed such that the time period for performing the method is at most 300 ms, the method comprising ending (708) the output of the high voltage alternating current.

14. The method according to claim 1, wherein the high-voltage test includes a high-voltage insulation measurement at the test object (300).

15. The method according to claim 1, wherein the high-voltage AC current output to the test object (300) has a voltage of 2kV to 12kV.

16. The method of claim 1, wherein the output of the high-voltage alternating current (701) comprises outputting the high-voltage alternating current with a continuously increasing or staged increase in absolute voltage value.

17. A high-voltage generating device for performing high-voltage testing on a test object, the high-voltage generating device comprising: - A high-voltage transformer (201) is used to generate high-voltage alternating current. - Output terminal (202), which is used to output high-voltage AC current to the test object (300), and - Control equipment (203), which is designed to protect personnel (400) during high-voltage testing by: - Output (701) high-voltage AC current to the test object (300), - Determine the time curve of at least one electrical variable at the high-voltage transformer (201) while outputting the high-voltage alternating current, and -The output of high-voltage AC current ends (708) according to the time curve of the at least one electrical variable. The at least one electrical variable mentioned above includes the phase and absolute value of the currents (502, 602) on the high-voltage transformer (201) and the phase and absolute value of the voltages (501, 601) on the high-voltage transformer (201). The device (203) is also designed to determine the impedance based on the absolute value and phase of the current (502, 602) and the voltage (501, 601), wherein if the impedance is less than a predefined impedance threshold, the output of the high-voltage AC current is terminated.

18. The high-voltage generating device according to claim 17, wherein the high-voltage device is in the form of a portable device.

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