Method for monitoring a switching operation of an on-load tap changer by means of a drive unit, and drive unit

Abstract

The invention relates to a method for monitoring a switching operation of an on-load tap changer (20) by means of a drive unit (2) having a drive module (3) and by means of a control unit (4) having a control device (11), characterized by the following steps: - receiving or generating, by the control device (11), a switching signal; - determining a first point in time at which the switching operation begins; - determining a second point in time at which the switching operation ends; - determining a final switching operation duration on the basis of the first and second point in time; - comparing the final switching operation duration with a setpoint value; - enabling a subsequent switching operation if the final switching operation duration falls below the setpoint value; wherein - the setpoint value is formed from a plurality of final switching operation durations of previous switching operations.

Description

[0001] Method for monitoring a switching operation of an on-load tap-changer by means of a drive unit and drive unit

[0002] The invention relates to a method for monitoring a switching operation of an on-load tap-changer by means of a drive unit.

[0003] Furthermore, the invention relates to a drive unit for an on-load tap-changer.

[0004] On-load tap-changers are typically used to regulate voltage in different tap-changer transformers. A drive is used to operate the on-load tap-changer. A motor is mounted on a transformer housing and connected to the on-load tap-changer via a linkage. Since the tap-changer transformers, and thus also the drive, are usually located outdoors, fluctuating ambient temperatures can affect the on-load tap-changer's switching operations. Because the on-load tap-changer is housed in an insulating material, which has a temperature-dependent viscosity, a switchover at a particularly low temperature can take significantly longer than at a particularly high temperature. This makes monitoring an on-load tap-changer, and in particular a switchover of the on-load tap-changer, difficult and demanding.

[0005] It is therefore an object of the present invention to provide a method for monitoring a switching operation of an on-load tap-changer, which takes temperature fluctuations into account and thus improves the reliability of switching operations and makes them safer.

[0006] This object is achieved by a method for monitoring a switching operation of an on-load tap-changer by means of a drive unit with a drive module and a control device, which comprises the features of claim 1.

[0007] Furthermore, it is an object of the invention to provide a drive unit for monitoring the actuation of an on-load tap-changer, which operates safely and reliably.

[0008] This object is achieved by a drive unit for an on-load tap-changer comprising the features of claim 9.

[0009] The method according to the invention for monitoring a switching of an on-load tap changer by means of a drive unit with a drive module and a control unit with a control device comprises the following steps:

[0010] - Receiving or generating a switching signal by the control device;

[0011] - Determining a first time at which the switching begins;

[0012] - Determining a second time at which the switching ends;

[0013] - Determining a final switching duration based on the first and second time points;

[0014] - Comparing the final switching time with a target value;

[0015] - Enabling a next switchover when the switchover falls below the setpoint; the setpoint is formed from several final switchover times of previous switchovers.

[0016] The method according to the invention has the advantage that a dynamic setpoint is used to monitor the transfer, and in particular the transfer duration. With a properly designed on-load tap-changer, it is only operated a few times per day. Temperature fluctuations, which occur primarily during the different seasons, can thus be measured during the few transfers per day and used to adjust the setpoint. The setpoint is thus continuously adjusted to temperature fluctuations over a period of several days without any actual temperature measurement taking place.

[0017] Essentially, each switchover is monitored by determining a switching duration. For this purpose, after a switching command, a time is determined at which the switchover begins. This is done by the control device, which detects the actuation of the third contactor, i.e. the brake contactor. A second time determines the end of the switchover. This is also done by the control device, which detects the actuation of a sensor, in particular a microswitch, and / or one of the contactors. Based on the two times, the control device determines the final switchover duration and compares it with a setpoint. If the value of the final switchover duration is less than the setpoint, another switchover is enabled by the control device. In addition, the determined final switchover duration is added to the last final switchover durations, and an average is calculated from this, which forms a new setpoint.Preferably, the setpoint is determined from the final switching times of the last five, ten, twenty, or five to twenty switching operations, i.e., previous switching operations, with the most recent final switching time replacing the oldest final switching time. For this purpose, the individual five, ten, twenty, or five to twenty final switching times are stored.

[0018] After each enabled switchover, the existing setpoint is replaced by the new setpoint and used for the next switchover.

[0019] The first point in time, i.e., the start of the switchover, is determined by a third contactor in the control unit. The third contactor is released at this point in time.

[0020] The second point in time, i.e., the end of the switchover, is determined using a sensor and / or the contactors of the control unit. The sensor and / or the contactors are activated at this point in time.

[0021] Furthermore, the current switching duration is determined based on the initial switching time. The current switching duration is continuously compared with the setpoint or measured by a control device. The switching is aborted if the current switching duration exceeds the setpoint. The current switching duration exceeds the setpoint if the current switching duration is 1.5 to 3 times the setpoint. In other words, the current switching duration is continuously and permanently monitored. As soon as a specified switching time is exceeded, the switching is aborted.

[0022] The final switching duration within the meaning of the invention is a closed time interval determined by the first and second time points. The current switching duration within the meaning of the invention is an open time interval that begins at the first time point and only ends when the setpoint or a multiple of it is exceeded.

[0023] According to a second aspect, the invention proposes a drive unit for an on-load tap-changer for monitoring a switchover, comprising: a drive module with a motor having a motor shaft connected to the on-load tap-changer and a sensor, a control unit with a control device having a first contactor, a second contactor, and a third contactor; wherein the control device is designed and configured to detect the actuation of the third contactor and to determine this actuation as the first time in the switchover; to detect the actuation of the sensor and / or a first and / or second and / or third contactor and to determine this actuation as the second time in the switchover; to determine a final switchover duration based on the first and second time points; to compare the switchover duration with a target value; to enable the next switchover if the switchover duration falls below the target value;to create a setpoint from several switching times of previous switching operations.;

[0024] The drive unit according to the invention serves to monitor and actuate the on-load tap-changer. The control device of the control unit detects when the third contactor and / or the sensor, or the first and / or second and / or third contactor of the drive module, are actuated. Based on the recorded times, a switching duration—the final switching duration—is determined and compared with a setpoint. Correct switching durations are stored and used to generate a new setpoint.

[0025] The contactors are preferably interconnected in such a way that when one contactor drops out, another contactor drops out or the self-holding of one contactor triggers the self-holding of another contactor.

[0026] The control device of the control unit is designed and configured to actuate each of the contactors such that they are activated or deactivated and assume a conducting or isolating state, to record, store, correlate, and process these actuations and the times of the respective actuations. The control device is designed and configured to detect the actuation of the sensor, i.e., the microswitch, in particular the opening and closing, and to record, store, correlate, and process the actuation and the corresponding times of the respective actuations.

[0027] The control device is designed and configured to calculate or determine switching times based on the specific times, to store them, to delete them and to process them, for example for averaging.

[0028] The control device is designed and configured to compare one or more switching times with a setpoint value and to enable the next switching if the switching time falls below the setpoint value.

[0029] To carry out the method steps, the control device has a processing unit and a memory. Furthermore, the control device has interfaces via which the contactors and the sensor are connected to the control device.

[0030] The on-load tap-changer is preferably designed as a reactor tap-changer. This tap-changer comprises a selector with two independently movable selector arms. Furthermore, the on-load tap-changer comprises a diverter switch with a vacuum interrupter and a bridging switch. The on-load tap-changer and the drive unit, including the drive module and the control unit, form a switch assembly.

[0031] The invention and its advantages will now be explained in more detail by means of exemplary embodiments with reference to the attached drawings, without thereby limiting the invention to the exemplary embodiment shown.

[0032] They show:

[0033] Figure 1 is a schematic representation of an embodiment of a drive unit for an on-load tap-changer;

[0034] Figure 2 shows a flow diagram of a method according to the invention for monitoring a switchover.

[0035] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals are shown in the individual figures that are necessary for the description of the respective figure.

[0036] Figure 1 shows a schematic representation of an exemplary embodiment of a switch arrangement 1 with an on-load tap-changer 20 and a drive unit 2. The drive unit 2 comprises a drive module 3, which is connected to the on-load tap-changer 20 via a motor shaft 10, and a control unit 4. This drive unit 2 enables the inventive method for carrying out a switching operation of an on-load tap-changer 20. The on-load tap-changer 20 is designed as a reactor switch. The drive module 3 and the control unit 4 are preferably connected to one another via cables. The drive module 3 comprises a motor 8 with a motor shaft 10 and an encoder 9. The motor 8 is a three-phase asynchronous motor operated in a Steinmetz circuit. The control unit 4 comprises a first, a second, and a third contactor 5, 6, 7.The first contactor 5 and the second contactor 6 are connected to a power source 12 via a motor protection switch 13. The first contactor 5 activates the connection between the motor 8 and the first pole of the power source 12, whereby the motor 8 is rotated in a first direction and the on-load tap-changer 20 is actuated in a first direction. The second contactor 6 activates the connection between the motor 8 and a second pole of the power source 12, whereby the motor 8 is rotated in a second direction and the on-load tap-changer 20 is actuated in a second direction. The third contactor 7 is designed as a braking contactor. In the actuated or activated state, it connects the three windings of the motor 8 or short-circuits the three windings of the motor 8, whereby the motor 8 is braked or held at a standstill.During operation, the energy flows from the energy source 12 via the motor protection switch 13, the first or second contactor 5, 6 and finally via the third contactor 7 to the motor 8.

[0037] The sensor 9 is configured to detect a value for a position, such as an angular position of the motor shaft 10. The sensor 9 is designed as a microswitch that is actuated by cams on the motor shaft 10.

[0038] A control device 11, which is part of the control unit 4, is connected to the contactors 5, 6, 7, the sensor 9, and the motor protection switch 13. The control device 11, and thus the control unit 4, is designed and configured to activate and deactivate or actuate the first, second, and third contactors 5, 6, 7 as well as the motor protection switch 13, and to detect the time of this actuation. Furthermore, the control device 11, and thus the control unit 4, is designed and configured to detect the signals from the sensor 9, in particular when a microswitch is actuated. The control device 11 not only actuates the motor protection switch 13, but also detects its triggering and generates a message accordingly. When the motor protection switch 13 is triggered, the motor 8 is disconnected from the energy source 12. In addition, the motor protection switch 13 acts on the first and second contactors 5, 6 in such a way that they drop out.

[0039] Figure 2 shows a process flow for monitoring a switching operation of the on-load tap-changer 20 with a drive unit 2.

[0040] In the first step 40, the control device 11 first sends a signal 30 to the control unit 4 for "switching," more precisely, for switching up or down. This signal is generated by a voltage regulator, a monitoring system, or by manual input (not shown). The voltage regulator, the monitoring system, and / or means for manual input can be part of the control device 11 and the control unit 4. This means, for example, that the on-load tap changer 20 must be actuated in order to adjust the voltage of a tapped transformer.

[0041] The "switching" signal contains, among other things, a switching direction indication, i.e., it specifies whether switching should occur up or down, or in which direction. In the next step 41, the control device 11 of the control unit 4 activates either the first or the second contactor 5, 6, depending on the direction in which switching is to occur.

[0042] In the next step 42, the control device 11 actuates the third contactor 7, causing the motor 8 to rotate in a corresponding direction and the on-load tap-changer 20 to be actuated in a first or second direction. At the same time, the control device 11 begins a time measurement. The control device 11 thus determines the first point in time, i.e., the point in time at which the third contactor 7 is actuated, in this case, deactivated. Deactivation means that the three windings of the motor 8 are no longer short-circuited, which means that the motor 8 is not braked.

[0043] As soon as the motor shaft 10 of the motor 8 has rotated by a certain angle, preferably between 1 and 30 degrees, the sensor 9, i.e. the microswitch, is actuated and takes over the self-holding of the first or second contactor 5, 6. This actuation is detected by the control device 11.

[0044] As soon as the motor shaft 10 of the motor 8 has rotated further by an angle of 320 to 350 degrees, preferably by an angle of 330 to 385 degrees or an angle of 338 to 382 degrees, this is detected by the sensor 9 in the next switching step 43. The microswitch (sensor 9) is actuated in this angular range. Depending on the design, the control device 11 detects the actuation of the microswitch, the actuation of the third contactor 7, as well as the actuation of the first or second motor contactor 5, 6, and defines this time as a second time.

[0045] The second time can also be determined either solely by means of sensor 9 or first contactor 5 or second contactor 6 or third contactor 7 or any combination of sensor 9 and / or first contactor 5 and / or second contactor 6 and / or third contactor 7.

[0046] The sensor 9 is thus actuated, specifically deactivated, in the angular range of 320 to 350 degrees, preferably in the angular range of 330 to 385 degrees or in the angular range of 338 to 382 degrees, thereby deactivating the self-locking of the first or second contactor 5, 6 and interrupting the power supply to the motor 8. The control device 11 activates the third contactor 7.

[0047] Alternatively, the first and second contactors 5, 6 are coupled to the third contactor, so that when the self-locking contact of the first or second contactor 5, 6 is released, the third contactor 7 also releases. The three windings of motor 8 are short-circuited, braking the motor 8 to a standstill. For a complete switching operation, the motor 8 must rotate the motor shaft 10, preferably by 360 degrees. The braking process begins at an angle of 320 degrees, or alternatively, 330 degrees or 338 degrees.

[0048] In a next step 44, a switching duration is determined by the control device 11 based on the first and second times; in other words, a time required for a switching is measured.

[0049] In a next step 45, the final switching duration is compared with a setpoint by the control device. If the switching duration is greater than the setpoint, further switching is blocked in or by the control device 11. If the switching duration is less than the setpoint, further switching is enabled in the control device 11.

[0050] After step 42, i.e., in step 46, i.e., after time measurement has begun using the control device 11, a continuous comparison of the current switching duration with the setpoint is performed during the switchover. As soon as the measured time, i.e., the current switching duration, is greater than the setpoint, the motor protection switch 13, and thus the first or second contactor 5, 6, and thus the third contactor 7, are actuated, and the switchover is interrupted.

[0051] The value for the current switching duration can exceed 1.5 times or reach 3 times the setpoint before a switching is interrupted.

[0052] If the switching duration is shorter than the setpoint, a new setpoint is generated in the next step 47. First, the last determined switching duration is saved, and the oldest of the ten previous switching durations is deleted. A new setpoint is then calculated as the average of the previous switching durations. This new

[0053] Setpoint will be used at the next switchover.

[0054] In a next step 48 the circuit is terminated or aborted.

[0055] Reference symbol

[0056] 1 switch arrangement

[0057] 2 drive unit

[0058] 3 Drive module 4 Control unit

[0059] 5 first contactor

[0060] 6 second contactor

[0061] 7 third contactor

[0062] 8 Motor 9 Sensor

[0063] 10 Motor shaft

[0064] 11 Control device

[0065] 12 Energy source

[0066] 13 Motor protection switches 20 On-load tap-changers

[0067] 30 signals

Claims

Patent claims 1. A method for monitoring a switching operation of an on-load tap-changer (20) by means of a drive unit (2) with a drive module (3) and a control unit (4) with a control device (11), characterized by the following steps: - receiving or generating a switching signal by the control device (11); - Determining a first time at which the switching begins; - Determining a second time at which the switching ends; - Determining a final switching duration based on the first and second time points; - Comparing the final switching time with a target value; - Enabling the next switchover if the final switchover time falls below the setpoint; - the setpoint is formed from several final switching times of previous switching operations.

2. A method for monitoring a switching operation of an on-load tap changer (20) according to claim 1, wherein - a current switching duration is determined based on the first time of switching; - the current switching time is permanently compared with the setpoint; - the switching is aborted if the current switching time exceeds the setpoint.

3. A method for monitoring a switching operation of an on-load tap changer (20) according to claim 2, wherein - the current switching time exceeds the setpoint, if a value of the current switching time exceeds 1.5 to 3 times the setpoint.

4. A method for monitoring a switching operation of an on-load tap changer (20) according to one of claims 1 to 3, wherein - the setpoint is an average of the final switching times from the last ten enabled switching operations.

5. A method for monitoring a switching operation of an on-load tap changer (20) according to one of claims 1 to 4, wherein - a new setpoint is formed in such a way that the final switching duration of the last switching replaces the oldest of the last final switching durations and an average value is formed from this.

6. A method for monitoring a switching operation of an on-load tap changer (20) according to one of claims 1 to 5, wherein - the setpoint is replaced by the new setpoint after the next enabled switchover.

7. A method for monitoring a switching operation of an on-load tap changer (20) according to one of claims 1 to 6, wherein - the first point in time at which the switching begins is determined via a third contactor (8) of the drive module (3), - the third contactor (8) is actuated at the first time.

8. A method for monitoring a switching operation of an on-load tap changer (20) according to one of claims 1 to 7, wherein - the determination of the second time at which the switching is terminated is carried out via the sensor (9) or the first contactor (5) or the second contactor (6) or a third contactor (7) of the control unit (4), or - determining the second time at which the switching is terminated via the sensor (9) and the first contactor (5) or via the sensor (9) and the second contactor (6) or via the sensor (9) and the third contactor (7), or - the sensor (9) and / or the first contactor (5) and / or the second contactor (6) and / or the third contactor (7) is actuated at the second time.

9. Drive unit (2) for an on-load tap-changer (20) for monitoring a switching operation, comprising: - a drive module (3) with a motor (8) with a motor shaft (10) which is connected to the on-load tap-changer (20) and a sensor (9), a control unit (4) with a control device (11) with a first contactor (5), a second contactor (6) and a third contactor (7); wherein - the control device (11) is designed and arranged to - to detect the actuation of the third contactor (7) and to determine this actuation as the first moment in the switching; - to detect the actuation of the transmitter (9) and / or a first and / or second and / or third contactor (5, 6, 7) and to determine this actuation as the second time of switching; - to determine a final switching time based on the first and second time points; - to compare the final switching time with a target value; - to enable the next switching if the final switching duration falls below the setpoint; to form a setpoint from several final switching durations.

10. Drive unit (2) according to claim 9, wherein the first, second and third contactors (5, 6, 7) are actuated by the control device (11); the motor (8) is supplied with energy by the first and second contactors (5, 6); depending on which of the two contactors (5, 6) is actuated, the motor (8) and thus the on-load tap changer (20) are actuated in a first or a second direction.

11. Drive unit (2) according to one of claims 9 or 10, wherein the third contactor (7) is actuated by the first and second contactors (5, 6) and thus by the control device (11).

12. Drive unit (2) according to one of claims 9-11, wherein the control unit (4) comprises a motor protection switch (13) connected in series between a power source (12) and the first and second contactors (5, 6); the control device (11) is connected to the motor protection switch (13) and the- can actuate it and can detect its actuation; the control device (11) generates a message after the actuation of the motor protection switch (13).

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