Method for operating on-load tap changer and on-load tap changer arrangement
By using control devices and sensors to detect current changes in the on-load tap-off operation, determining the characteristic value and comparing it with the limit value, the operational insecurity caused by inrush current is solved, and safe and reliable operation is achieved.
Patent Information
- Application Number
- CN202380046085.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-14
- Filing Date
- 2023-06-20
- Publication Date
- 2025-02-11
AI Technical Summary
The prior art fails to effectively handle inrush current when operating the on-load tap-off switch, resulting in unsafe operation.
The control device receives the switching command, uses the sensor to detect the current change direction, determine the time and interval of the current zero crossing point, derive the characteristic value and compare it with the limit value, and if the limit value is exceeded, the operation will be suspended or suspended.
Ensure that current changes are monitored before or after switching commands, and inrush current is detected and processed for safe and reliable operation of the on-load tap-off switch.
Smart Images
Figure CN119422219A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for operating an on-load tap changer and an on-load tap changer device. Background Art
[0002] In transformer substations there are a large number of switches for different tasks and with different requirements. In order to operate the respective switches, they must be driven by a drive system. Among other things, these switches are on-load tap changers, load changeover switches, selectors, double commutators, commutators, preselectors, power switches, load switches or disconnect switches.
[0003] Therefore, the on-load tap changer is used, for example, for the interruption-free switching between different winding taps of an electrical device such as a power transformer. For example, the transformation ratio of the transformer or the inductance of the choke can be changed thereby.
[0004] On-load tap changers are usually operated by means of a combination of a motor drive and a spring accumulator. The operation takes place immediately after the switching command, i.e. at any time. The occurrence of inrush currents is not taken into account. Summary of the invention
[0005] It is therefore an object of the present invention to provide a method for operating an on-load tap changer which ensures safe switching.
[0006] This object is achieved by the corresponding technical solutions of the independent claims. Other embodiments are the technical solutions of the dependent claims.
[0007] The invention proposes a method for operating an on-load tap changer by means of a drive device, a sensor and a control device, the method comprising the following steps:
[0008] - receiving a switching command for operating the on-load tap-changer via the control device;
[0009] - Detect the direction of current changes through sensors;
[0010] - determining a plurality of successive instants of current zero crossings of the current profile by means of a control device;
[0011] - determining, by means of the control device, a plurality of intervals between these instants of the current zero crossings;
[0012] - deriving, by the control device, characteristic values from the plurality of intervals;
[0013] - comparing the characteristic value with a limit value by means of a control device;
[0014] - if the characteristic value exceeds the limit value, the operation is terminated or suspended by the control device;
[0015] - If the characteristic value corresponds to or falls below the limit value, the operation is performed by controlling the drive device by the control device.
[0016] The method is based on the following idea: the current change trend in the variable transformer, on-load tap changer or vacuum switching tube is monitored before or after the switching command and the inrush current that occurs is detected before the actual operation of the on-load tap changer. The interval between these current zero crossings is determined based on the current zero crossings determined in the past or after the switching command. The characteristic value derived from the interval is compared with the limit value. When the limit value is met, the inrush current can be excluded, so that the operation can be performed safely and reliably. However, if the inrush current occurs before or after the switching command, the operation is suspended or stopped. In the sense of the present invention, the inrush current can be understood as the occurrence of irregularities in the current change trend.
[0017] After receiving a switching command for operating the on-load tap changer from the control device, the on-load tap changer is not operated immediately, but the past current profile or the current profile after the switching command is first checked for irregularities. Only when no irregularities are detected is the actual operation performed accordingly.
[0018] The current profile can be detected in any desired manner. In particular, the current profile is detected by one or more sensors on the tapped transformer or the on-load tap changer and transmitted to the control device.
[0019] The detected current variation trend is processed and evaluated in the control device and a plurality of successive moments in the current variation trend are determined. These moments are current zero crossings. Preferably, at least three successive moments when the current is zero are determined. In addition, a starting moment in the current variation trend is determined. According to an embodiment, the current variation trend in the past from the starting moment or the current variation trend in the future from the starting moment is determined. Here, the current variation trend in the past before the starting moment has been stored in the control device, or is stored after the starting moment.
[0020] In addition, a plurality of intervals between the plurality of consecutive moments of the current zero crossings are determined by means of the control device. In the case of three moments, two intervals are determined. In particular, the interval between the first moment and the second moment and the interval between the second moment and the third moment are determined.
[0021] Furthermore, a characteristic value is determined from the plurality of intervals by means of the control device. The characteristic value may be a ratio, an average value, etc. The characteristic value is compared with a limit value by means of the control device. The limit value is stored in the control device. The limit value may be adjusted manually or automatically.
[0022] Furthermore, if the characteristic value meets or falls below the limit value, the on-load tap changer is operated by means of the control device by controlling the drive device. If the characteristic value exceeds the limit value, the actual operation is paused or terminated. The pause or termination of the operation can last for several seconds, such as 1 to 10 seconds. After the pause, the current change trend is detected again and the method is executed again until the operation is possible.
[0023] In addition, the present invention provides an on-load tap changer device, comprising:
[0024] - On-load tap-changer;
[0025] - sensor;
[0026] - drive device;
[0027] - control device;
[0028] Wherein, the control device is arranged and constructed for
[0029] - receiving switching instructions for operating the on-load switch-disconnector;
[0030] - Detect the direction of current changes through sensors;
[0031] - multiple successive moments of current zero crossings that determine the course of the current change;
[0032] - determining a number of intervals between these moments of the current zero crossings;
[0033] - deriving characteristic values from the plurality of intervals;
[0034] - comparing the characteristic value with a limit value;
[0035] - if the characteristic value exceeds a limit value, the operation is terminated or suspended by the control device;
[0036] - If the characteristic value corresponds to or falls below the limit value, the on-load tap-changer is actuated by means of the drive.
[0037] The on-load tap changer device includes an on-load tap changer having a load changeover switch and a selector. The load changeover switch has at least one vacuum switch tube. In addition, the on-load tap changer device includes a drive device, a sensor and a control device. The on-load tap changer device allows the current change trend to be checked before the on-load tap changer is operated and thus ensures safe operation when a surge current occurs. The control device is constructed and arranged to continuously detect, store and process the current change trend during the operation of the adjustable transformer, that is, before the switching instruction, through one or more sensors. For this purpose, the control device correspondingly has a calculation unit and / or a processor and / or a memory. The control device is constructed and arranged to detect, store and process the current change trend through one or more sensors after the switching instruction. For this purpose, the control device correspondingly includes a calculation unit and / or a processor and / or a memory.
[0038] Furthermore, the control device is designed and provided for controlling a drive device which in turn actuates the on-load tap changer. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] The present invention will be described in detail below according to exemplary embodiments with reference to the accompanying drawings. The accompanying drawings are as follows:
[0040] Figure 1 A variable transformer with an on-load tap changer is shown;
[0041] Figure 2 Show the method flow;
[0042] Figure 3 A diagram for illustrating the method is shown;
[0043] Figure 4 A further diagram is shown to illustrate a further specific embodiment of the method. DETAILED DESCRIPTION
[0044] Figure 1An on-load tap changer device 1 is shown. The on-load tap changer device 1 comprises a control device 2, at least one sensor 5 and an on-load tap changer 4. The control device 2 is connected to a drive device 3 of the on-load tap changer 4. The control device 2 is provided and constructed to control the drive device 3 so that the drive device operates the on-load tap changer 4. In addition, the control device 2 is connected to a sensor 5 or a plurality of sensors 5, which measure the current flowing through the tapped transformer 7, the vacuum switching tube 6 or the on-load tap changer 4. The control device 2 is constructed and arranged to detect, measure and evaluate the current detected by the one or more sensors 5. In particular, the control device 2 determines the course of the current change, that is, when the current has or takes a zero value and how often this occurs. The sensor 5 can be arranged, for example, on the tapped transformer 7, in particular on the high voltage side 8 or the low voltage side 9. In addition, the sensor 5 can be arranged in the on-load tap changer 4, directly on the vacuum switching tube 6 or at any other position suitable for detecting the course of the current change.
[0045] The control device 2 continuously detects the current profile before an operation or only when a switching command is received in the control device 2. For this purpose, the control unit 2 accordingly has a computing unit and / or a processor and / or a memory.
[0046] The drive device 3 is mechanically connected to the on-load tap changer 4 and thus also to the vacuum interrupter tube 6 via a drive train 10. The drive device is provided and designed to operate the on-load tap changer or to execute a switching command of a control unit.
[0047] The control device 2 can be arranged as an independent device on the variable transformer 7 or in a control room. In addition, the control device 2 can be part of the drive control device of the on-load tap changer 4 or be designed as part of a voltage regulator. The control device 2 is designed and arranged to control the drive device 3.
[0048] The tapped transformer 7 has a main winding 11 and a regulating winding 12. The on-load tap changer 4 is connected to the regulating winding 12 via a winding tap 13. The main winding 11 and the regulating winding 12 are arranged on the high-voltage side 8 (in rare cases, also on the low-voltage side). In addition, the tapped transformer 7 has a low-voltage winding 14 that is inductively coupled to the main winding 11 and the regulating winding 12.
[0049] Figure 2A flow chart of a method for operating an on-load tap changer is shown. In the context of the invention, "before operating the on-load tap changer" means that an irregular current profile can be detected before a switching command or can also be detected after a switching command. Before a switching command, the method is continuously executed during operation. If an irregularity is detected, the operation is aborted immediately after the switching command or is paused for a predetermined time and the method is executed again until operation is possible.
[0050] In a first step 30, the control device 2 receives, at a starting time T0, a switching command for operating the on-load tap changer 4. The switching command can be a manual switching command or can also come from a voltage regulator.
[0051] In the next step 31, the current profile is detected by the sensor 5 and transmitted to the control device. The current profile can be detected both after the switching command and before the switching command.
[0052] In a next step 32, the control device determines a plurality of successive times T1, T2, T3, Tx with current zero crossings of the current profile 20. In this case, the newly detected current profile or the current profile before the switching command is used.
[0053] In a next step 33 , the intervals A1 , A2 , Ax are determined based on the times T1 , T2 , T3 , Tx of the current zero crossings.
[0054] In a next step 34 , a characteristic value K is formed based on the intervals A1 , A2 , Ax.
[0055] In a next step 35 , the determined characteristic value K is compared with a limit value G, and if the characteristic value K corresponds to or falls below the limit value G, the on-load tap changer 4 is actually actuated in a next step 36 . For this purpose, the control device 2 controls the drive device 3 accordingly.
[0056] If the characteristic value K exceeds the limit value G, the operation is terminated in a next step 37. Alternatively, when the limit value G is exceeded, the operation can be suspended for a certain time in a next step 38 and the method can be restarted.
[0057] Figure 3Used to illustrate the method according to the present invention. The time current change trend t (in ms) in the tapped transformer is plotted on the X-axis. The Y-axis represents the magnitude of the current I in amperes. The change trend of the current or the current change trend is sinusoidal or approximately sinusoidal here. The curve of the current change trend 20 intersects the X-axis at the current zero point. Therefore, at these times T1, T2, T3, Tx, no current flows through the tapped transformer and the vacuum switch tube 6 or the on-load tap changer 4. At the starting time T0, a switching command for operating the on-load tap changer 4 or a switching command for starting to operate the on-load tap changer is received in the control unit 2.
[0058] This time is assumed to be a possible starting time T0 of the load changeover. Starting from this starting time T0, at least three subsequent times T1, T2 and T3 of the subsequent current zero crossings are determined.
[0059] In the next step, the intervals A1 and A2 between the determined moments T1, T2, T3 are determined. Specifically, a first interval A1 between the first and second moments T1, T2 and a second interval A2 between the second and third moments T2 and T3 are determined. The intervals A1 and A2 indicate how much time has passed between these moments.
[0060] In the next step, a characteristic value K is determined based on the intervals A1, A2, Ax. For example, the ratio of the intervals A1 and A2 or all determined intervals to one another can be determined. In the ideal case, for example, A1 and A2 are equally large and the ratio is therefore one. After the characteristic value K is determined, the characteristic value is compared with the limit value G. If the characteristic value K exceeds the limit value G, the operation is terminated or paused. Pausing means stopping the switching for a defined time and then executing the method again. When the limit value is met or undershot, the on-load tap changer is operated by means of a drive device controlled by a control device.
[0061] In the example shown here, the current change trend is implemented based on three times T1, T2, T3, i.e. three current zero crossings. However, any number of current zero crossings T1-Tx and intervals A1-Ax can also be used for evaluation. This depends on how long the actual operation can wait after the switching command. The way of determining the characteristic value K and the way of defining the limit value G can also be adjusted arbitrarily.
[0062] Figure 4Used to illustrate the method according to the present invention according to another embodiment. The time current change trend t (in ms) in the tapped transformer is plotted on the X-axis. The Y-axis represents the magnitude of the current I in amperes. The trend of the current change or the current change trend is sinusoidal or approximately sinusoidal here. The curve of the current change trend intersects the X-axis at the current zero crossing. Therefore, at these times T1, T2, T3, Tx, no current flows through the tapped transformer and the vacuum switch tube 6 or the on-load tap changer 4. At the starting time T0, a switching command for operating the on-load tap changer 4 or a switching command for starting to operate the on-load tap changer is received in the control unit 2.
[0063] This moment is assumed to be the starting moment T0 of the load switching. From this starting moment T0, at least three moments T1, T2 and T3 of the current zero crossing are determined, i.e. at least three moments of the current zero crossing before the starting moment T0. This is possible because the current change trend has been monitored and recorded before the switching instruction.
[0064] In the next step, the intervals A1 and A2 between the determined moments T1, T2, T3 are determined. Specifically, a first interval A1 between the first and second moments T1, T2 and a second interval A2 between the second and third moments T2 and T3 are determined. The intervals A1 and A2 indicate how much time has passed between these moments.
[0065] In the next step, a characteristic value K is determined based on the intervals A1, A2, Ax. For example, the ratio of the intervals A1 and A2 or all determined intervals to one another can be determined. In the ideal case, for example, A1 and A2 are equally large and the ratio is therefore one. After the characteristic value K is determined, the characteristic value is compared with the limit value G. If the characteristic value K exceeds the limit value G, the operation is terminated or paused. Pausing means stopping the switching for a defined time and then executing the method again. When the limit value is met or undershot, the on-load tap changer is operated by means of a drive device controlled by a control device.
[0066] In the example shown here, the current change trend is implemented based on three times T1, T2, T3, i.e. three current zero crossings. However, any number of current zero crossings T1-Tx and intervals A1-Ax can also be used for evaluation. This depends on how long the actual operation can wait after the switching command. The way of determining the characteristic value K and the way of defining the limit value G can also be adjusted arbitrarily.
[0067] The method thus makes it possible to check for irregularities in the course of the current already before a switching command and also immediately after a switching command. Reference numerals list
[0068] 1On-load tap-changer equipment
[0069] 2 Control device
[0070] 3. Drive device
[0071] 4On-load tap changer
[0072] 5 Sensors
[0073] 6 Vacuum switch tube
[0074] 7Adjustable transformer
[0075] 8 High voltage side
[0076] 9 Low voltage side
[0077] 10 Drivetrain
[0078] 11 Main winding
[0079] 12 Adjustment winding
[0080] 13 Winding taps
[0081] 14 Low voltage winding
[0082] 15 Additional Sensors
[0083] 20 Current change trend
[0084] T0 start time
[0085] T1 first zero crossing
[0086] T2 second zero crossing
[0087] T3 third zero crossing
[0088] Tx other zero crossing
[0089] A1 first interval
[0090] A2 Second Interval
[0091] Ax Additional Interval
Claims
1. A method for operating an on-load tap changer (4) by means of a drive device (3), a sensor (5) and a control device (2), the method comprising the following steps: - receiving a switching command for operating the on-load tap changer (4) via the control device (2); - Detecting the current change trend (20) through the sensor (5); - determining a plurality of successive times (T1, T2, T3, Tx) of current zero crossings of the current variation (20) by means of the control device (2); - determining a plurality of intervals (A1, A2, Ax) between these instants (T1, T2, T3, Tx) of the current zero crossing by means of the control device (2); - deriving a characteristic value (K) from the plurality of intervals (A1, A2, Ax) by means of a control device (2); - comparing the characteristic value (K) with a limit value (G) by means of a control device (2); - if the characteristic value (K) exceeds the limit value (G), the operation is terminated or suspended by the control device (2); If the characteristic value (K) corresponds to or falls below the limit value (G), an operation is performed by controlling the drive device (3) by the control device (2).
2. The method according to claim 1, wherein: The current profile (20) is detected before or after a switching command for operating the on-load tap changer (4) is received from the control device (2).
3. The method according to claim 1 or 2, wherein: The multiple consecutive time points (T1, T2, T3, Tx) of the current zero crossing point of the current change trend (20) before the starting time point (T0) of the switching command arrival or after the starting time point (T0) of the switching command arrival are determined.
4. The method according to claims 1 to 3, wherein: The eigenvalue (K) is a ratio of at least two intervals.
5. The method according to claims 1 to 4, wherein: The characteristic value (K) can deviate from the limit value (G) by several percentage points.
6. The method according to claims 1 to 5, wherein: The operation is paused for a few seconds via the control device (2).
7. The method according to claims 1 to 6, wherein: At least three consecutive times (T1, T2, T3, Tx) of current zero crossings of a current change trend (20) before a starting time (T0) of a switching command arrival or after a starting time (T0) of a switching command arrival are determined.
8. The method according to claims 1 to 5, wherein: At least two intervals (A1, A2, Ax) between the times (T1, T2, T3, Tx) of the current zero crossings are determined by the control device (2).
9. On-load tap-changer equipment (1), comprising: - on-load tap-changer (4); - sensor (5); - driving device (3); - control device (2); The control device (2) is configured to: - receiving a switching instruction for operating an on-load switch-disconnector (4); - Detecting the direction of current change through a sensor (5); - determining a plurality of successive moments (T1, T2, T3, Tx) of the current zero crossing of the current variation trend (20); - determining a plurality of intervals (A1, A2, Ax) between these instants (T1, T2, T3, Tx) of the current zero crossing; - deriving characteristic values (K) from the plurality of intervals (A1, A2, Ax); - comparing the characteristic value (K) with a limit value (G); - if the characteristic value (K) exceeds the limit value (G), the operation is terminated or suspended by the control device (2); If the characteristic value (K) corresponds to or falls below the limit value (G), the on-load tap changer is actuated by means of the drive device (3).