Method for adapting a voltage target value for controlling a tap transformer and installation for adapting a voltage target value for controlling a tap transformer

Abstract

1. A method for adapting a voltage setpoint Usoll for controlling the voltage of a tap transformer 200 by an on-load tap changer 10, comprising: below, determining reverse power flow on the low voltage side of the tap transformer 200 by measuring current I20 and voltage U20; operating the on-load tap changer 10 from an actual tap position n to another tap position n-1, n+1 and measuring the voltages U21, U19 and currents I21, I19 at the other tap positions n-1, n+1; Calculating values ​​from the powers L19, L20, and L21 of different tap positions n, n-1, and n+1; and using the calculated value m as a slope for a first section of the straight line 50 of the voltage target value Usoll.

Description

[Technical field]

[0001] The present invention relates to a method for adapting a voltage target value for controlling a tap transformer.

[0002] Furthermore, the invention relates to an arrangement for adapting a voltage setpoint for controlling a tap transformer. [Background technology]

[0003] Generally, on the low-voltage side of a tap transformer in a power grid, active power is consumed by power loads. To keep the voltage constant when increasing or decreasing, the voltage is controlled by an on-load tap changer. However, since there may always be more generators on the low-voltage side, active power may flow back. In this case, a new control concept is required. Summary of the Invention [Problem to be solved by the invention]

[0004] It is therefore an object of the present invention to provide a method for adapting a voltage setpoint for controlling a tap transformer by means of an on-load tap changer, in which the voltage at the final power load does not deviate from a preset voltage fluctuation band and, moreover, does not exceed the maximum load factor of the power system, which corresponds to the current flowing in the transmission line. [Means for solving the problem]

[0005] This problem is solved by a method for adapting a voltage setpoint for controlling the voltage of a tap transformer by means of an on-load tap changer, the method comprising the steps of: determining reverse power flow on the low voltage side of the tap transformer by measuring current and voltage; operating the on-load tap changer from the actual tap position n to another tap position and measuring the voltage and current at the other tap position; determining a value from the power at different tap positions; and using the calculated value m as a slope for a first section of a line of the voltage target value.

[0006] The method allows the voltage setpoint used for controlling the on-load tap changer in the tap transformer to be adapted very efficiently and quickly in the event of reverse power flow, thus avoiding overvoltages at the power loads in the power grid. Furthermore, the method guarantees maximum power supply. The constant set voltage setpoint makes it possible for it to be unaffected by fluctuations on the low-voltage side in the power grid. The method allows, for example, a photovoltaic power system to be easily wired in the power grid without adverse effects. The method then allows the voltage setpoint to be appropriately adapted to the new situation in the power grid. For this purpose, after the reverse power flow has been identified, the powers (apparent power and / or real power) are calculated at different tap positions. In this case, the powers are based on the currents and voltages measured on the low-voltage side of the tap transformer when the on-load tap changer is moved to a different tap position. After the calculation of the powers, a divisor of these powers represents the value m of the slope of the line showing the voltage setpoint.

[0007] The power may be calculated in any manner, for example as apparent power and / or real power.

[0008] Reverse power flow may be determined in any manner, for example, by measuring current and voltage on the low-voltage side of a tap transformer. In particular, when reverse power flow is identified, active current flows from the power loads and generators, i.e., from the low-voltage side through the tap transformer to the high-voltage side.

[0009] The on-load tap changer can be configured in any way, for example an on-load tap changer with a diverter switch, a selector or a load tap selector. Furthermore, the on-load tap changer can have mechanical switching elements such as contacts or vacuum valves or semiconductor switching elements. The on-load tap changer can be operated by a motor drive or by electronic control of the semiconductor switching elements.

[0010] The power can be calculated in any way, for example as a product of the measured current and the measured voltage, in which case the apparent power or the real power can be calculated.

[0011] The value m for the slope of the first section of the voltage target line is calculated as a divisor from the power between the different tap positions of the on-load tap changer.

[0012] The method can be performed in any manner, where the calculated value m can be used as the slope of the line of the voltage target value in the first section.

[0013] The method may be carried out optionally, in which the power at the actual tap position is calculated as the product of the measured current and the measured voltage at the actual tap position; the on-load tap changer is operated and moved from the actual tap position to a higher tap position; The power of the higher tap position is determined as a product of the measured current and the measured voltage of the higher tap position; The value m is calculated as a divisor from the power of the higher tap position and the power of the lower tap position.

[0014] At this time, the calculated value m is used as the gradient within the first section of the straight line of the voltage target value, and is therefore replaced with the gradient within the first section ahead of the straight line.

[0015] The method may be carried out optionally, in which the power at the actual tap position is calculated as the product of the measured current and the measured voltage at the actual tap position; the on-load tap changer is operated to move from the actual tap position n to a lower tap position; the power of the lower tap position is calculated as a product of the measured current and the measured voltage of the lower tap position; The value m is calculated as a divisor from the power of the higher tap position n and the power of the lower tap position n-1.

[0016] The method may be carried out optionally, in which the on-load tap changer is operated and moved from the actual tap position to a higher tap position; The power of the higher tap position is calculated as a product of the measured current and the measured voltage of the higher tap position; The on-load tap changer is operated twice to move from the actual tap position to a lower tap position; the power of the lower tap position is calculated as a product of the measured current and the measured voltage of the lower tap position; The value m is calculated as a divisor from the power of the higher tap position n+1 and the power of the lower tap position.

[0017] The method may be carried out optionally, in which the on-load tap changer is operated and moved from the actual tap position to a lower tap position; The power of the lower tap position is calculated as the product of the measured current and the measured voltage of the lower tap position; The on-load tap changer is operated twice to move from the actual tap position to a higher tap position, The power of the higher tap position is calculated as a product of the measured current and the measured voltage of the higher tap position; The value m is calculated as a divisor from the power of the higher tap position and the power of the lower tap position.

[0018] When specifying the voltage target, the on-load tap changer is always switched from the actual tap position to the adjacent tap position. For each tap position, the voltage and current are measured. The divisor from the power of the higher tap position and the power of the lower tap position provides the slope of the line that represents the voltage target. The higher and lower tap positions mean that the value of the higher tap position of the on-load tap changer is greater than the value of the lower tap position.

[0019] Furthermore, it is an object of the present invention to provide an apparatus for adapting a voltage setpoint for controlling a tap transformer, comprising at least one measuring device for measuring the current and voltage on the low-voltage side of the tap transformer and a control device connected to the at least one measuring device for receiving the measured current and voltage.

[0020] The measuring device may be configured arbitrarily. For example, it may have a current sensor and a voltage sensor. These sensors are connected to the control device via a cable or wirelessly. The installation is adapted and configured to carry out the improved method for adapting a voltage setpoint for controlling a tap transformer by means of an on-load tap changer, in particular to detect the measured currents and voltages, to ascertain the reverse power flows, to calculate the respective powers, to control the operation of the on-load tap changer so that it moves to a different tap position, to determine a value for the slope of the voltage setpoint line, to modify the voltage setpoint line accordingly and to store said line.

[0021] The installation can be constructed in any way, in which the tap transformer is a longitudinal control device with variable impedance, in particular a high-voltage transformer.

[0022] Hereinafter, a detailed description will be given with reference to the drawings based on exemplary embodiments. Components that are identical or function identically or have the same effect may be indicated by the same reference numerals. In some cases, the same components or components that have the same function are described only for the figure in which they first appear. The description is not necessarily repeated in the subsequent figures. [Brief description of the drawings]

[0023] [Figure 1] The power supply system is shown. [Diagram 2] FIG. 1 is a schematic diagram of an ideal power grid. [Diagram 3] 1 is a graph for visualizing voltage control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] FIG. 1 shows a power supply system 100 including a tap changer 200 having a number of inductively coupled primary windings 300 and a number of secondary windings 400 and an on-load tap changer 10 coupled to the primary winding. The primary winding 300 has a number of taps. The on-load tap changer 10 is connected to the primary winding 300 via the taps. The on-load tap changer 10 is configured to connect to the taps, i.e. to control the tap transformer 200. A motor drive 11 operates the on-load tap changer 10, which is thereby provided for controlling the tap transformer 200. An arrangement 20 for controlling the voltage is provided. The arrangement 20 comprises a control device 21 connected to the motor drive 11 and to a measuring device 15. The control device 21 is configured and adapted to control the operation of the motor drive 11, i.e. the on-load tap changer 10, which in turn controls the tap transformer 200.

[0025] The tap transformer 200 is connected at its primary side (high voltage side) to a high voltage power grid. Furthermore, the tap transformer 200 is connected at its secondary side (low voltage side) to a low voltage power grid. For example, 110 kV is applied to the high voltage side and 20 kV is applied to the low voltage side. Preferably, the power grid is a three-phase power grid. In general, the voltage of the first power grid is converted to a lower voltage of the second power grid by the tap transformer 200. Preferably, the tap transformer 200 is configured as a linear regulator or a high voltage transformer with variable impedance.

[0026] A control device 21 of the installation 20 at the tap transformer 200 is provided for controlling the voltage, said control device 21 being arranged either directly on the housing of the transformer or separately in a control room.

[0027] In addition to a power load, a generator may also be connected to the secondary side 40, i.e. the low-voltage side. Voltages may therefore fluctuate on this side or on this power side. By operating the on-load tap changer 10 on the primary side 30 of the first power grid (high-voltage power grid), these voltage fluctuations can be counteracted on the secondary side 40. For this purpose, at least one measuring device 15 is arranged on the low-voltage side, which measures these voltage and current fluctuations. In particular, the measuring device 15 is at least one current sensor and at least one voltage sensor arranged on at least one transmission line 16 of the second power grid (low-voltage power grid). This measuring device 15 transmits the measured voltage and the measured current to the control device 21. Furthermore, the measuring device 15 may also be arranged on the high-voltage side, i.e. the primary side 30.

[0028] Based on the transmitted current and voltage, the voltage is controlled, in particular the on-load tap changer 10 is operated by the motor drive 11 according to a method for controlling the voltage.

[0029] Furthermore, the installation 20 comprising the control device 21 comprises means for carrying out the method of the invention or is configured and adapted to carry out the method of the invention.

[0030] 2 is a circuit diagram of an ideal power grid 41 having a power supply system 100. A tap transformer 200 is wired in this power grid. The circuit diagram of the power grid 41 further shows a transmission line with a transmission line impedance 45, a power load with a power load impedance 46, a high-voltage power grid with a power grid impedance 43, and a generator 47. In this case, the generator 47 means all components (generators) that supply power to the power grid and do not take out power. The generator 47 is, for example, a solar power generation system, a wind power generation system, and is generally called a renewable energy generator.

[0031] Power line impedance 45 represents the impedance of all power lines (or high voltage power lines or cables).

[0032] The power grid impedance 43 represents the impedance of the upstream power grid at the connection point of the tap transformer.

[0033] The tapped transformer 200 exhibits a controllable longitudinal impedance.

[0034] Both the power load and the generator are connected to the power grid 41, so that energy is not only extracted from the high-voltage power grid by the power load, but also supplied by the generator. Extracting means that on the secondary side 40 - i.e. on the low-voltage side - the main power (active power) is consumed by the power load. This means the so-called forward power flow (FPF).

[0035] During this supply, on the secondary side 40, power (active power) is supplied from a power source (47) to the power grid 41 by a solar power generation system or the like. In other words, at this time, active power moves from the power load, i.e., the secondary side 40, to a higher-level power grid, or power is transported from the low-voltage side to the high-voltage side. This is called reverse power flow (RPF).

[0036] When determining whether RPF or FPF occurs, the voltage U20 between points A and B of the power grid is measured. Point A is between the tap transformer 200 and the transmission line impedance 45, the power load impedance 47 and the generator 47. Point B is downstream of the transmission line impedance 45, the power load impedance 46 and the generator 47. Furthermore, the current I20 is measured directly at point A. All measurements, especially the measurement at point A, are performed by the measuring device 15. In the case of FPF, the current I20 (active current) flows from the high-voltage power grid through the tap transformer 200 and the transmission line to the power load. In the case of RPF, the current (active current) I20 flows from the combination of the power load and the generating station through the transmission line and the tap transformer 200 to the high-voltage power grid. When measuring the RPF at points A and B, the sign of the measured power (active power) is negative. When measuring the FPF at points A and B, the sign of the measured power (active power) is positive. Therefore, it can be confirmed whether a reverse or forward power flow is occurring based on the sign.

[0037] Figure 3 is a graph for visualizing the voltage control at the tap transformer 200. The power (active power) P taken from or fed to the tap transformer 200 is plotted on the x-axis. Taken in this case means that the main power (active power) is consumed by the power loads on the secondary side 40. This means the so-called forward power flow (FPF).

[0038] During this supply, power (active power) is supplied to the power supply system 100 by a solar power generation system or the like on the secondary side 40. In other words, at this time, power (active power) moves from the power load side, i.e., the secondary side 40, to the power grid, or power is transported from the low voltage side to the high voltage side. This is called reverse power flow (RPF).

[0039] The zero point of the X-axis is plotted in the center of the graph so that the corresponding power state of the power grid, i.e. FPF or RPF, can be represented. The graph can therefore be divided into a first section where FPF occurs and a second section where RPF occurs. In the case of FPF, the measured power is plotted positive on the low voltage side. In the case of RPF, the measured power has a negative sign.

[0040] A reference voltage Uref is plotted on the Y-axis. Here, for example, a reference voltage of 100 V is defined. This reference voltage can then vary by 10%, i.e. between 90 V and 110 V. Alternatively, any voltage value can be plotted. Essentially, the reference voltage Uref directly or indirectly represents the measured voltage of the secondary side 40 in the low-voltage power grid.

[0041] The graph depicts a straight line 50, which is used as a target value in the arrangement 20 for controlling the voltage. This straight line 50 represents the voltage target value Usoll. During operation, the voltage Uist on the secondary side 40 of the tap transformer 200 is therefore continuously monitored by at least one measuring device 15. The measured value of the voltage Uist is depicted in the graph. Depending on where the measured value lies in the diagram, the on-load tap changer 10 is operated by the motor drive 11 until the measured actual value of the voltage Uist lies on or in the immediate vicinity of the voltage target value Usoll indicated by the straight line 50. In this case, a voltage fluctuation band or tolerance range is predefined around the voltage target value Usoll, i.e. the straight line 50. An actual value Uist of the voltage, within which no operation has to be performed, can lie.

[0042] The straight line 50 of the voltage target value Usoll is divided into a first section and a second section, and each of these sections may have a different slope.

[0043] Within the FPF, i.e. when power is drawn by the power loads, the line 50 has a predefined gradient in the second section 50.2 of the control voltage setpoint Usoll. This gradient depends on certain power grid parameters. These parameters are predefined by the power lines (Rline, Lline) and the power loads (Rload, Lload). These parameters can be easily determined and therefore stored in the installation 20 before start-up.

[0044] This ensures that the voltage on the power load side is always maintained within a preset fluctuation range even if the load increases. Generally, the voltage is between 360V and 440V.

[0045] Within the RPF, i.e. when power is supplied on the low voltage side, the straight line 50 in the first section of the voltage setpoint Usoll has another slope in this section of the control, however, different from the slope in the area of ​​the FPF. This slope can also be defined before start-up on the basis of the power grid parameters. For this, however, said parameters must be known for the lines and the generators. In many cases, however, said parameters do not exist or can change over time.

[0046] However, the invention makes it possible to dynamically adapt the slope of the line of the voltage setpoint Usoll, as represented by the double arrow 50.3, without the power grid parameters having to be preset.

[0047] In the following, a method sequence for adapting the voltage setpoint Usoll for controlling the voltage of the tap transformer 200 by the on-load tap changer 10 is illustrated.

[0048] In a first step, the power flow is determined. In particular, it is determined whether a reverse or forward power flow is occurring. For this purpose, the direction of the current I20 or the sign of the active current and the voltage U20 are determined, and from this determination it is derived whether a reverse or forward power flow is occurring. The current I20 and the voltage U20 measured at point A of the power grid are detected by the measuring device 15 and determined at the installation 20. Furthermore, the power L20 is calculated as the product of the measured voltage U20 and the current I20. This power can be apparent power or active power.

[0049] If the active power derived from the voltage U20 and the current I20 is negative (has a negative sign), then reverse power flow occurs, i.e. the active current at point A flows from the generator through the transformer 200 to the power grid.

[0050] If the active power derived from the voltage and current is positive, then forward power flow is occurring, i.e. active current at point A flows from the power grid through transformer 200 to the power load.

[0051] In another step, the on-load tap changer 10 in the tap transformer 200 is operated such that it is moved from the actual starting tap position n to the next higher tap position n+1 or alternatively to the next lower tap position n-1. Now, when the higher tap position is switched to, the first current I21 and the first voltage U21 are measured and from said measurements the power L21 is obtained. However, when the next lower tap position n-1 is switched to, the first current I19 and the second voltage U19 are measured and from said measurements the power L19 is calculated.

[0052] In a subsequent step the on-load tap changer 10 is switched to the first tap position n.

[0053] In the next step, the value m is calculated from the power measured at the touched tap position and the power measured at the actual tap position. The value m is always created as a divisor of the power of the higher tap position and the power of the lower tap position, where higher and lower tap positions mean that the numerical value of the higher tap position of the on-load tap changer is greater than the numerical value of the lower tap position. Thus, in the former ascending switching case, the value m is the divisor of the power L21 of the higher tap position n+1 and the power L20 of the actual tap position n, or in the former descending switching case or when a lower tap position or tap changing position is reached, the value m is the divisor of the power L20 of the actual tap position n and the power L19 of the lower tap position n-1.

[0054] In a next step, this calculated value m is used as the slope for the line 50 of the voltage setpoint Usoll in the first section 50.1 of the RPF. This new line section provides the voltage setpoint Usoll and is used to control the on-load tap changer 10.

[0055] The equation for the line of the voltage setpoint Usoll is then y=m×x. This voltage setpoint Usoll is determined by the equipment 20 for controlling the voltage, in particular by the control device 21. The equipment 20 is therefore not only used to control the voltage of the tap transformer 200, but also to adapt the voltage setpoint Usoll. In many cases, this adaptation can be performed at will, in particular when weather conditions change. For example, it can be performed when clouds move over a large photovoltaic system, when the power supply changes, i.e. when there is a reverse current with a large gradient, or when power grid configurations are coupled or decoupled.

[0056] In the following, an alternative method sequence for adapting the voltage setpoint Usoll for controlling the voltage of the tap transformer 200 by the on-load tap changer 10 is illustrated.

[0057] Here again, in the first step, the power flow is determined. Specifically, it is determined whether a reverse power flow or a forward power flow is occurring. For this purpose, the directional voltage U20 of the current (active current) I20 is identified, and from this identification, it is derived whether a reverse power flow or a forward power flow is occurring. The current I20 and voltage U20 measured at point A of the power grid are detected by the measuring device 15 and identified by the facility 20.

[0058] If the active power derived from the voltage U20 and the current I20 is negative (has a negative sign), then reverse power flow occurs, i.e. the current at point A flows from the generator through the transformer 200 to the power grid.

[0059] If the power derived from the voltage and current is positive, then forward power flow is occurring, i.e., current at point A flows from the power grid through transformer 200 to the power load.

[0060] In another step, the on-load tap changer 10 in the tap transformer 200 is operated such that the on-load tap changer 10 is moved from the actual starting tap position n to the next higher tap position n+1. Then, a first current I21 and a first voltage U21 are determined, from which a power L21 is obtained. The power can be an apparent power or a real power.

[0061] In another step, the on-load tap changer 10 in the tap transformer 200 is operated such that the on-load tap changer 10 is moved from the actual starting tap position n+1 to the next lower tap position n-1 twice in descending order. Then, a second current I19 and a second voltage U19 are determined, from which a power L19 is obtained. The power can be an apparent power or a real power.

[0062] In a subsequent step the on-load tap changer 10 is switched to the first tap position n.

[0063] In the next step, a value m is calculated from the power L21 measured at the touched tap position n+1 and the power L19 measured at the touched second tap position n-1. The value m is always created as a divisor from the power of the higher tap position and the power of the lower tap position, where the higher tap position and the lower tap position mean that the value of the higher tap position of the on-load tap changer is greater than the value of the lower tap position. Thus, in this case, the value m is the divisor from the power L21 of the higher tap position n+1 and the power L19 of the tap position n-1.

[0064] In a next step, the calculated value m is used as the gradient for the line 50 of the voltage setpoint Usoll in the first section 50.1 of the RPF. This new gradient provides the voltage setpoint Usoll. The equation for the line of the voltage setpoint Usoll is y=m×x. This voltage setpoint Usoll is determined by the installation 20 for controlling the voltage, in particular by the control device 21. The installation 20 is thus not only used to control the voltage of the tap transformer 200, but can also adapt, change and store the voltage setpoint Usoll. In many cases, this adaptation can be performed arbitrarily.

[0065] Alternatively, tap position n-1 may be switched once in descending order first, and tap position n+1 may be switched twice in descending order, etc. Compared to the above method, the divisors from the powers of these more distant tap positions are more accurate than the divisors from the powers of the more closely spaced tap positions.

[0066] The installation 20 having a control device 21 has means for carrying out the above-mentioned method or is configured and adapted to carry out the above-mentioned method. [Explanation of symbols]

[0067] 10 On-load tap changer 11 Motor drive unit 15 Measuring Equipment 16 Conductor 20 Equipment 21 Control device 30 200 primary side 40 200 secondary 41 Power grid 43 Power grid impedance of high voltage power grid 45 Transmission Line Impedance 46 Power Load Impedance 47 Generator 50 Voltage target value Usoll 50.1 1st Section of 50 50.2 Second Section of 50 50.3 Double Arrow 100 Power System 200 tap transformer 300 Primary Winding 400 Secondary Winding

Claims

1. 1. A method for adapting a voltage target value (Usoll) for controlling the voltage of a tap transformer (200) by an on-load tap changer (10), comprising: below, determining the reverse power flow on the low voltage side of the tap transformer (200) by measuring the current (I20) and voltage (U20); operating the on-load tap changer (10) from actual tap position n to another tap position (n-1, n+1) and measuring the voltages (U21, U19) and currents (I21, I19) at the other tap positions (n-1, n+1); calculating values ​​from the powers (L19, L20, L21) of different tap positions (n, n-1, n+1); and using the calculated value m as the slope for the first section of the line (50) of the voltage target value (Usoll).

2. 2. The method according to claim 1, wherein the calculated value m is defined as the straight line (50) within a first section (50.1) of the voltage target value (Usoll) and is replaced with the straight line (50) existing within the first section (50.1).

3. The power (L20) at the actual tap position (n) is calculated as the product of the measured current (I20) and the measured voltage (I20) at the actual tap position (n); The on-load tap changer (10) is operated and moved from an actual tap position (n) to a higher tap position (n+1); the power (L21) of the higher tap position (n+1) is calculated as the product of the measured current (I21) and the measured voltage (U21) of the higher tap position (n+1); 3. The method of claim 1 or 2, wherein the value m is calculated as a divisor from the power (L21) of the higher tap position (n+1) and the power (L20) of the lower tap position (n).

4. The power (L20) at the actual tap position (n) is calculated as the product of the current (I20) measured at the actual tap position (n) and the voltage (U20) measured at the actual tap position (n); the on-load tap changer (10) is operated and moved from the actual tap position (n) to a lower tap position (n-1); the power (L19) of the lower tap position (n-1) is calculated as the product of the measured current (I19) and the measured voltage (U19) of the lower tap position (n-1); 3. The method according to claim 1 or 2, wherein the value m is calculated as a divisor from the power (L20) of the higher tap position n and the power (L19) of the lower tap position (n-1).

5. The on-load tap changer (10) is operated and moved from an actual tap position (n) to a higher tap position (n+1); The power (L21) of the higher tap position (n+1) is calculated as the product of the measured current (I21) and the measured voltage (U21) of the higher tap position (n+1), and the on-load tap changer (10) is operated twice to move from the actual tap position (n+1) to the lower tap position (n-1), the power (L19) of the lower tap position (n-1) is calculated as the product of the measured current (I19) and the measured voltage (U19) of the lower tap position (n-1); 3. A method according to claim 1 or 2, wherein the value m is calculated as a divisor from the power of the higher tap position n+1 (L21) and the power of the lower tap position (n-1) (L19).

6. the on-load tap changer (10) is operated and moved from the actual tap position (n) to a lower tap position (n-1); The power (L19) of the lower tap position (n-1) is calculated as the product of the measured current (I19) and the measured voltage (U19) of the lower tap position (n-1); The on-load tap changer (10) is operated twice to move from the actual tap position (n-1) to the higher tap position (n+1); 3. The method of claim 1 or 2, wherein the power (L21) of a higher tap position (n+1) is calculated as the product of the measured current (I21) and the measured voltage (U21) of the higher tap position (n+1), and wherein the value m is calculated as the divisor of the power (L21) of the higher tap position (n+1) and the power (L19) of the lower tap position (n-1).

7. 3. The method according to claim 1, wherein the power is apparent power and / or real power.

8. A facility (20) for adapting a voltage target value (Usoll) for controlling the voltage of a tap transformer (200), comprising: at least one measuring device (15) for measuring currents (I19, I21, I21) and voltages (U19, U20, U21) on the low voltage side of the tap transformer (200); The installation (20) comprises: a control device (21) connected to the at least one measuring device to receive the measured currents (I19, I21, I21) and voltages (U19, U20, U21); and the control device (21) is configured to perform the method according to claim 1 or 2.

9. 9. An arrangement (20) for adapting a voltage target value (Usoll) for controlling the voltage of a tap transformer (200) according to claim 8, comprising: The tap transformer (200) is an autotransformer.

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