Arrangement for interrupting current in a high-voltage line and method for operating such an arrangement

Abstract

An arrangement for interrupting current in a high-voltage line, the arrangement comprising a series circuit of an inductive load (10) and a controllable mechanical isolating switch (20), which is provided for connection to the terminals of a high-voltage AC power source (30), the inductive load (10) being connected to a resistor arrangement (40) in order to discharge energy contained in the inductive load (10) via the resistor arrangement (40) when the isolating switch (20) is opened and to reduce a restart voltage of the isolating switch (20), the resistor arrangement (40) comprising a series circuit of a discharge resistor (41) and a controllable switching element (42), which is connected to the winding ends of a secondary winding (12) of the inductive load (10), the arrangement being designed such that the isolating switch (20) and the switching element (42) are controlled during operation of the arrangement,to close the switching element (42) in the resistor arrangement (40) immediately before an arc occurs between contacts of the circuit breaker (20) during the current interruption.,

Description

[0001] The invention relates to an arrangement for interrupting current in a high-voltage line, a system for interrupting current in a high-voltage line of a power system and a method for interrupting current in a high-voltage line of a power system.

[0002] In AC power grids, it is common practice to switch a reactor on and off as an inductive load using a circuit breaker. The reactor is used, for example, as a voltage regulator for a long transmission line, such as a high-voltage line (110 kV) or an extra-high-voltage line (400 kV), during off-peak periods. Other applications for reactors include load flow control.

[0003] It is well known that significant overvoltages can occur when switching inductive loads, and especially reactors, in a high-voltage line. Since the problems associated with switching current in a high-voltage line differ significantly from other power interruption tasks, the requirements and solutions are addressed in a separate IEC standard, IEC 62271-110:2017: High-voltage switchgear and controlgear - Part 110: Inductive load switching.

[0004] Load break switches used on a high-voltage line to interrupt alternating current are designed to interrupt shunt reactor currents. When a shunt reactor is de-energized, upon receipt of the trip signal by the load break switch, a trip circuit of the circuit breaker is energized, causing its main contacts to move apart. Current continues to flow through the load break switch's main contacts while the contacts move apart. This process typically takes between 15 ms and 40 ms for a high-voltage (HV) load break switch. When the contacts open wide enough, an arc begins to form between the arcing contacts of the load break switch. Current continues to flow in a conductive gas between the open contacts in the form of an arc.As the current approaches a natural zero crossing, the arc cooling mechanism of the load breaker forces the arc current to zero before the natural zero crossing. This phenomenon is called current chopping. The energy trapped in the reactor being switched at the time of current interruption then oscillates between its inductance and a stray capacitance connected in parallel with the inductance.

[0005] The latest generation of load breakers generally have very low breaking currents, so that the inductive current is interrupted near a natural current zero point. Depending on the specification and design of the reactor, the breaking current varies, so that higher interrupting currents also occur. As a result, the transient recovery voltage (TRV) across the gap between the load breaker contacts varies in magnitude. However, it has a very short rise time at a frequency in the range of 1 kHz.

[0006] These rapidly rising transients can cause the contact gap to break and the current to reappear due to arcing. This occurs in a very short time and is also referred to as reignition or restrike. According to the definition in IEC 62271-110, reignition refers to a voltage breakdown in the switch-disconnector within a quarter cycle of the interruption attempt. In this standard, restrike is defined as a voltage breakdown in the switch-disconnector at a time equal to or greater than a quarter of a cycle after the interruption attempt. Restrike results in a steep voltage transient with a high amplitude and frequency in the kilohertz range, which is referred to as a reignition overvoltage.The re-ignition overvoltage can adversely affect the dielectric integrity and electrical lifetime of the load break switch and the inductive load.

[0007] When used as a voltage regulator, the reactor is typically switched on and off daily in a power transmission circuit. This usually occurs at night when loads are low. Load break switches are therefore subject to a higher switching frequency than fault breakers, such as circuit breakers.

[0008] When switching the reactor located in high- and extra-high-voltage transmission lines, the current re-ignitions between switching operations caused by an arc in the load break switch cause very steep voltage rises in the reactor. This can lead to cumulative damage that shortens the reactor's service life. Since reactors for high- and extra-high-voltage transmission lines are very expensive and critical equipment, this damage must be kept to a minimum.

[0009] Frequent restriking can also damage the circuit breaker's interrupting element by puncturing nozzle material. This, in turn, increases the likelihood of further restriking. The intense pressure created within the circuit breakers can also force the current to zero prematurely, resulting in further increasing voltage across the reactor, requiring the circuit breakers to withstand even higher voltages. For this reason, it is important to switch the reactor in a manner that minimizes damage to the reactor, the circuit breakers, and other power system components caused by restriking during the switching operation.

[0010] DE 30 04 521 C2 discloses an arrangement for interrupting current in a high-voltage line with a series circuit comprising an inductive load and a controllable mechanical disconnector. The arrangement comprises a series combination of a first circuit breaker contact and a resistor connected in series with a power transmission line, the series combination being connected between a power supply source and the power transmission line, a second circuit breaker contact, and a control device which closes the second circuit breaker contact after a prescribed period of time following the closing of the first circuit breaker contact. The second circuit breaker contact is arranged parallel to the series combination.

[0011] The object of the invention is to provide an arrangement for interrupting current in a high-voltage line, which is structurally and / or functionally improved to minimize damage to components of the power system caused by switching the inductive load. Further objects include providing a corresponding system for interrupting current in a high-voltage line of a power system and a method for interrupting current in a high-voltage line of a power system.

[0012] These objects are achieved by the features of the independent claims. Advantageous embodiments emerge from the dependent claims.

[0013] The invention proposes an arrangement for interrupting current in a high-voltage line, wherein the arrangement comprises a series connection of an inductive load and a controllable mechanical disconnector. In the present case, a high-voltage line is understood to be a line to which voltages of more than 70 kV up to more than 800 kV are applied. Frequently used high voltages are 110 kV or 400 kV. Lines with a voltage of more than 400 kV are sometimes also referred to as extra-high voltage lines. The inductive load is a directly grounded choke coil, an ungrounded choke coil, or a choke coil grounded via a neutral choke coil. In particular, the inductive load is a choke coil with a winding around a core, wherein the components of the inductive load are surrounded by an insulating material, e.g., oil. The inductive load can be a single-phase unit or a three-phase unit.Such an inductive load is used, for example, as a voltage regulator for long transmission lines or for load flow control. A controllable mechanical disconnector is generally understood to be a mechanical switching device that connects and interrupts a circuit (operating and fault currents) and carries the rated current when closed. There are many types of circuit breakers that can be used as disconnectors, classified according to their mode of operation or the internal insulation of a breaker. Circuit breakers classified according to their mode of operation include single-pole disconnectors, where each pole operates independently, and three-phase disconnectors, where all poles are switched simultaneously. Circuit breakers classified according to the internal insulation of the breaker include, for example,Vacuum insulation, clean air insulation, gas insulation: SF6 gas, g3, non-SF6 gas.

[0014] The series circuit comprising the inductive load and the controllable disconnector is intended for connection to the terminals of a high-voltage AC power source. The inductive load is connected to a resistor arrangement in order to discharge energy contained in the inductive load via the resistor arrangement when the disconnector is opened and to reduce a reclosing voltage of the disconnector. For this purpose, the resistor arrangement comprises a series circuit comprising a discharge resistor and a controllable switching element, wherein the series circuit is connected to the winding ends of a secondary winding of the inductive load. The arrangement is designed such that the disconnector and the switching element are controlled during operation of the arrangement in order to close the switching element in the resistor arrangement immediately before an arc occurs between contacts of the disconnector during the current interruption.

[0015] As is known to those skilled in the art, the process of breaking the circuit breaker's power involves four phases: 1. Closed position: Current flows through the main contacts of the circuit breaker. 2. Contact separation: Upon receipt of a trip control signal to initiate the opening of the circuit breaker, a trip circuit of the circuit breaker is energized and the contacts move apart. Current continues to flow through the contacts of the circuit breaker while the contacts move apart. This process typically takes 15 ms to 40 ms for a high-voltage circuit breaker. 3. Arcing: When the contacts open wide enough, an arc is created between the circuit breaker contacts. Current continues to flow in a conductive gas between the open contacts, forming an arc. As the current approaches a natural zero crossing, an arc-cooling mechanism in the circuit breaker forces the arc current to zero before the natural zero crossing. This phenomenon is called current interruption. If no restrike occurs, the current is interrupted. 4. Open position: The current is or is interrupted.

[0016] According to the invention, it is therefore provided that the discharge resistor is integrated into the electrical circuit shortly before the occurrence of the arc.

[0017] This arrangement allows the energy trapped in the load-side inductance and capacitance to be discharged quickly through the discharge resistor and dissipated in the form of heat. This allows the reclosing voltage to be significantly reduced. The lower reclosing voltage across the circuit breaker contacts prevents re-ignition.

[0018] Thanks to the controllable switching element, the discharge resistor does not need to be continuously connected to the power supply, thus avoiding significant energy losses and a correspondingly large cooling device for heat dissipation. Preferably, the secondary winding of the inductive load is designed to reduce the high voltage generated by the high-voltage AC source to a medium voltage. In particular, the ratio between the high voltage and the medium voltage is 5:1 or higher. The high voltage generated by the high-voltage AC source is between 70 kV and more than 800 kV.

[0019] This eliminates the need to connect the discharge resistor directly to the high-voltage line. Another advantage of transforming the voltage in the resistor arrangement is that the resistor can be made smaller, allowing the energy generated in the inductive load to be discharged in a very short time.

[0020] The main purpose of the secondary winding of the secondary winding is thus to reduce the voltage applied to the inductive load on the primary side in order to enable the rapid switching of the discharge resistor into the arrangement at low cost.

[0021] The discharge resistor is preferably dimensioned such that it discharges the energy trapped in the inductive load so that the voltage across the inductive load becomes zero within half an AC voltage period. The resistance of the discharge resistor is dimensioned according to the following equation: R <LCL2N2CL, where R is the resistance of the discharge resistor, L is the main reactance of the inductive load, N is the voltage ratio between the primary voltage and the secondary voltage of the inductive load, and C L the stray capacitance of the inductive load.

[0022] The controllable switching element preferably has a switching time (switch-on time) that is shorter or significantly shorter than the switching time (switch-off time) of the mechanical disconnector. This can be achieved, for example, by designing the controllable switching element as a semiconductor switching element, in particular a thyristor, or as a fast mechanical medium-voltage circuit breaker. The switch-on time of the fast controllable switching element, when implemented as a semiconductor switch, is the time required to change its state from blocking mode to conducting mode upon application of a control signal. The switch-on time of the fast controllable switching element, when implemented as a mechanical medium-voltage circuit breaker, is measured from the start of receipt of the control signal until the moment the contacts touch and connect.

[0023] For a mechanical circuit breaker, the opening time (or mechanical time) is the time it takes for the circuit breaker to open its contacts sufficiently to create an arc across the circuit breaker's arcing contacts. This time is measured from the start of receiving the control signal until the moment the contacts begin to arc. This time typically ranges from 15 ms to 40 ms for a HV circuit breaker.

[0024] The mechanical disconnector therefore has a switching time that is considerably longer than the switching time of the controllable switching element.

[0025] A further advantageous embodiment provides that the respective control terminals of the disconnector and the switching element are connected to a common output of a control unit to receive the same control signal. Due to the different switching times of the disconnector and the switching element, the properties mentioned above are achieved: the switching element in the resistor arrangement can already be closed, and an arc is created between the contacts of the disconnector during the current interruption.

[0026] Conveniently, the inductive load comprises a primary winding, with the primary winding and the secondary winding surrounded by an insulating fluid, e.g., oil. The combination of primary winding and secondary winding thus forms a transformer, which transforms the high voltage applied to the primary winding into a lower voltage, particularly medium voltage, which is processed in the resistor arrangement.

[0027] The present invention further proposes a system for interrupting current in a high-voltage line of a power system, which uses one current interruption arrangement according to one or more embodiments of the invention per phase.

[0028] The invention further proposes a method for interrupting current in a high-voltage line of a power system, which comprises an arrangement for interrupting current according to one or more embodiments of the arrangement. The method comprises the step of controlling the disconnector and the switching element during operation of the arrangement by means of a control signal in order to close (switch on) the switching element in the resistor arrangement immediately before an arc occurs between contacts of the disconnector during the current interruption. This enables the energy trapped in the load-side inductance and capacitance and the heat generated in the process to be dissipated via the discharge resistor. The reclosing voltage of the mechanical disconnector can thus be significantly reduced. In particular, the lower closing voltage across the contact of the disconnector prevents reignition.

[0029] Conveniently, an identical (common) control signal provided at a common output of a control unit is processed as the control signal.

[0030] It is also advisable for the circuit breaker to be switched on during operation of the arrangement, and for the switching element to be switched off. This means that before the control signal is received, the inductive load carries the current to be interrupted, while no current flows in the resistor arrangement.

[0031] The invention is explained in more detail below using an exemplary embodiment in the drawing. In the drawings: Fig. 1 an electrical equivalent circuit diagram of a single-phase power system known from the prior art; Fig. Figure 2 is an electrical equivalent circuit diagram of a single-phase power system illustrating the principle of the present invention; Fig. 3 an electrical equivalent circuit diagram of a single-phase power system with a resistor arrangement according to the invention; Fig. 4 the electrical equivalent circuit of the Fig. 3, in which the control of the switching elements by means of a control signal is illustrated; Fig. 5 is a diagram showing the voltage flowing through the choke coil after a current interruption; and Fig. 6 a diagram showing the voltage of the choke coil after re-ignition.

[0032] Fig. 1 shows an electrical equivalent circuit diagram of a prior art single-phase power system with a single-phase transmission line 50, via which an inductive load 10 is supplied from a high-voltage AC source 30.

[0033] The inductive load 10 is designed, for example, in the form of a choke coil. This has a coil (winding) 11 with an inductance L and a load-side capacitance 14 of size C connected in parallel. L The coil 11 is wound around a core (not shown). The capacitance 14 is a stray capacitance. The components of the inductive load 10 are generally surrounded by an insulating material, e.g., oil. The precise mechanical structure of such an inductive load 10 is known to those skilled in the art and is not important for further understanding.

[0034] The inductive load 10 and the high-voltage AC power source 30 are connected to each other via the transmission line 50. A load-break switch 20, e.g., a mechanical element, is arranged in the transmission line 50. The load-break switch 20 is, for example, a gas-insulated load-break switch, such as an SF6 load-break switch. From an electrical point of view, the load-break switch 20 comprises, in addition to the actual mechanical switch 21, a capacitive scattering element 22 of size C. p and an inductive scattering element of size L p . The capacity C p is much smaller than the capacity C L (C p << C L ). The series circuit consisting of capacitive scattering element 22 and inductive scattering element 23 is connected in parallel to the terminals of the mechanical disconnector 21.

[0035] A source-side section 51 of the transmission line 50 connects a source-side end of the load-break switch 20 to a terminal of the AC voltage source 30. A load-side section 55 of the transmission line 50 connects the other, load-side end of the load-break switch 20 to a terminal of the inductive load 10. The other terminal of the inductive load 10 and the AC voltage source 30 are connected to each other via a return conductor 57. For safety reasons, the load-break switch 20 is usually integrated into the transmission line 50 such that the source-side section 51 of the transmission line is longer or significantly longer than the load-side section 55 of the transmission line.

[0036] The source-side section 51 of the transmission line is electrically characterized by an inductance 52 of size L S The load-side section 55 of the transmission line 50 is represented by an inductance 56 of size Lb represents, where: L S >> L b . The source-side section 51 of the transmission line 50 further comprises a capacitance 53 of size C S , where the capacity is an inherent capacity of the source-side section 51.

[0037] To interrupt the current through the inductive load 10, a Fig. 1 transmits a signal (not shown in detail) that switches the mechanical disconnector 21 from the conductive (closed) state to the blocking (open) state. After receiving the control signal, a short period of time elapses until the contacts of the disconnector 21 are mechanically separated. This period of time depends on the size and design of the disconnector 21 and is typically between 15 ms and 40 ms. This period of time is referred to as the switching time or opening time.

[0038] When the mechanical circuit breaker 21 is triggered, its contacts separate before the current zero point, and the current continues to flow due to the arc created between the contacts. As the current approaches the current zero point, it is forced to the zero point prematurely, which is known as current chopping. This results in energy stored in the inductive load 10 and oscillating between its components 11, 14. A maximum load-side overvoltage occurs when the stored energy is converted into capacitively stored energy in the load-side capacitor 14. This is Fig. 5 shown.

[0039] Fig. Figure 5 shows the reactor voltage after a power interruption. A denotes the source-side power frequency voltage. B denotes the influence of the arc voltage. C denotes the suppression of the maximum overvoltage (suppression peak overvoltage). D is the maximum recovery voltage (recovery voltage peak overvoltage). E denotes the load-side oscillation in the reactor. The maximum peak overvoltage is the so-called suppression peak overvoltage, also known as chopping overvoltage.

[0040] In the event of a successful current interruption, the inductive load is subjected to a load-side oscillogram (see E), which gradually returns to zero. For high-voltage reactors, the frequency of the load-side oscillation is typically a few kilohertz at most, with the exact frequency being determined by the values ​​of L and C. L the load-side inductance 11 and the load-side capacitance 14.

[0041] If, however, the attempt to interrupt the current is unsuccessful, reignition occurs, resulting in a breakdown between the contacts of the circuit breaker 21. The voltage on the load side must then adjust to the voltage of the high-voltage AC source 30. In the worst case, reignition occurs at the reclosing peak, as shown in Fig. 6 is shown.

[0042] The magnitude of the re-ignition overvoltage V pdepends on the damping in the circuit. The inductive load is subjected to a re-ignition oscillation with a frequency in the order of hundreds of kilohertz, although in rare cases frequencies of up to 1 MHz are reached. This frequency is determined by the size of the source-side capacitance 53 (C S ) and the load-side capacity 14 (ie C L ) and this intermediate inductance of the circuit is determined.

[0043] In the Fig. 6, which shows the voltage of the load-side inductance (choke coil) after re-ignition, are: V ma : the suppression peak overvoltage V o : the voltage at the inductive load 10 (choke coil) before the current interruption V c : the voltage peak recovery (recovery voltage peak) V p: the reignition overvoltage peak to earth V s : the reignition overvoltage excursion.

[0044] Point G shows the voltage curve during a reignition at the restart peak, while point H shows the curve during a successful current interruption.

[0045] Fig. Figure 2 illustrates the principle underlying the invention, which avoids the problems described above. The functional principle of the inventive approach is to combine the Fig. 1 to include a discharge resistor 15. The discharge resistor 15 is connected in parallel to the inductive load 10. This allows the energy trapped in the load 10 at the time of the current interruption, which oscillates between its inductance 11 and the load-side capacitance 14, to be discharged via the resistor 15 and dissipated in the form of heat. This reduces the restart voltage. Furthermore, the risk of reignition via the contacts of the mechanical disconnector 21 of the load-break switch 20 is reduced.

[0046] To discharge the energy contained in the inductive load in a very short time, the resistance value R of resistor 15 must be small enough. However, since the inductive load is connected to a high-voltage line 50, it is not practical to connect the discharge resistor 15 directly to this voltage level. Furthermore, a permanent parallel connection to the inductive load 10 would constantly convert energy into it, requiring complex cooling to dissipate the heat.

[0047] Fig. Figure 3 shows a resistor arrangement 40 that can implement the functional principle of resistor 15 while simultaneously preventing the problems described. The resistor arrangement 40 comprises a series circuit consisting of a discharge resistor 41 with resistance value R and a controllable switching element 42. The series circuit of these two elements is connected to the winding ends of a secondary winding 12 of the inductive load 10. The secondary winding 12 is magnetically coupled to the coil 11, designed as the primary winding, of the inductive load 10 via a core 13.

[0048] The main purpose of the secondary winding 12 is to reduce the high voltage occurring in the primary winding to a relatively lower voltage. A medium voltage can be achieved by a ratio of, for example, 5:1 between the high voltage and the voltage occurring in the resistor arrangement 40. If the voltage provided by the high-voltage AC source 30 is, for example, 110 kV, the secondary winding 13 reduces the voltage in the resistor arrangement 40 to at least 22 kV. The reduction in the voltage present in the primary circuit enables the use of a fast, controllable switching element 42. For example, a semiconductor switching element, in particular a thyristor, which has a switching time of approximately 1 ms, can be used as the controllable switching element 42.The reduced voltage in the resistor arrangement further enables the discharge resistor 41 and the controllable switching element 42 to be provided at low cost. Alternatively, a mechanical medium-voltage circuit breaker can be used as the controllable switching element 42.

[0049] When the mechanical disconnector 21 receives the control signal to interrupt the current through the high-voltage line 50, it usually takes between 15 ms and 40 ms from receipt of the control signal until the mechanical separation of the contacts of the disconnector 21. As in connection with Fig. As explained in Figure 5, its contacts separate before the current zero point, and the current continues to flow through the resulting arc. As the current approaches the current zero point, it is forced to the zero point prematurely, which represents the current interruption. Without the resistor arrangement provided according to the invention, this leads to an oscillation of the energy stored in the inductive load, with the maximum load-side overvoltage occurring when this energy is converted into capacitively stored energy in the load-side capacitor 14.

[0050] By providing the Fig. 3 and its physical properties, the switching element 42 in the resistor arrangement can already be closed before an arc is generated between contacts of the mechanical disconnector 21 during the current interruption. With a shorter switching time than the mechanical disconnector 21, the controllable switching element 21 connects the discharge resistor 41 via the secondary winding 12 of the inductive load 10 into the power supply path before the arc is drawn between the contacts of the mechanical disconnector 21 during the current interruption process. If the current is forced to zero prematurely, the current stored in the load-side inductance 11 and the load-side capacitance 14 flows through the discharge resistor 41 and is converted into heat. This results in a very low suppression peak voltage and restart voltage, as shown in Fig. 5 is marked with the reference symbol F.

[0051] The dimensioning of the discharge resistor 41 can be based on simulation results, particularly depending on the desired restart voltage. To achieve a good result, the discharge resistor 41 can be selected using the following equation: R <LCL2N2CL, where R is the resistance of the discharge resistor 41, L is the main reactance of the inductive load 10, N is the voltage ratio between primary and secondary voltage of the inductive load and C L the stray capacitance of the inductive load is 10.

[0052] The control of the isolating switch 20 and switching element 42 during operation of the arrangement takes place as follows: Fig.4, by means of a common control signal CS, which is output at an output 61 of a control unit 60. Before receiving the control signal to interrupt the current in the high-voltage line 50, the circuit breaker 20 is switched to the conducting state during operation of the arrangement, and the switching element is switched to the blocking state. During operation of the arrangement, the current to be interrupted thus flows through the inductive load 10. Upon receipt of the control signal, the circuit breaker is switched to the blocking state and the switching element is switched to the conducting state.

[0053] Due to the physically different design principles of the isolating switch 21 and the controllable switching element 42, the isolating switch 21 has a switching time that is longer than the switching time of the controllable switching element 42 of the resistor arrangement. The time-delayed switching of the mechanical isolating switch 21 and the controllable switching element 42 is achieved due to the different physical properties. Separate control with different signals is not provided and is not required. This allows the discharge resistor in the resistor arrangement 40 to be inserted into the circuit before an interruption of the current in the transmission line 50 occurs due to the opening of the isolating switch 20.

[0054] The invention has been described in connection with a single-phase power system. If the power system has multiple phases, the described system is used in particular per phase.

[0055] In a three-phase transmission system, each phase can be protected separately by an arrangement of the type described above. The three-phase disconnector 20 can be operated independently of one or three poles.

[0056] The arrangement according to the invention is applicable to various types of choke coils, such as directly grounded choke coils, ungrounded choke coils or choke coils grounded via a neutral choke. List of reference symbols 10 inductive load 11 Winding (primary winding) with inductance C L 12 Winding (secondary winding) with inductance L 13 Coupling element 14 load-side capacity 20 disconnectors 21 mechanical disconnector 22 capacitive scattering element of the mechanical disconnector 21 23 inductive leakage element of the mechanical disconnector 21 30 high-voltage AC power source 40 resistor arrangement 41 controllable switching element 42 Discharge resistor 50 transmission lines 51 Source-side section of the transmission line 52 Inductance of the source-side section 51 (source-side inductance) 53 Capacity of the source-side section 51 (source-side capacity) 55 load-side section of the transmission line 56 Inductance of the load-side section 51 (load-side inductance) 57 return conductor 60 control unit 61 Control unit output

Claims

[1] Arrangement for interrupting current in a high-voltage line, wherein the arrangement comprises a series circuit of an inductive load (10) and a controllable mechanical isolating switch (20), which is provided for connection to the terminals of a high-voltage AC source (30), wherein the inductive load (10) is connected to a resistor arrangement (40) in order to discharge energy contained in the inductive load (10) via the resistor arrangement (40) when the isolating switch (20) is opened and to reduce a restart voltage of the isolating switch (20), wherein the resistor arrangement (40) comprises a series circuit of a discharge resistor (41) and a controllable switching element (42), which is connected to the winding ends of a secondary winding (12) of the inductive load (10), wherein the arrangement is designed such that the isolating switch (20) and the switching element (42) during operation of the arrangement be controlled,to close the switching element (42) in the resistor arrangement (40) immediately before an arc occurs between contacts of the circuit breaker (20) during the current interruption., [2] Arrangement according to claim 1, characterized by that the secondary winding (12) of the inductive load (10) is designed to reduce the high voltage generated by the high-voltage AC source (30) to a medium voltage. [3] Arrangement according to claim 1 or 2, characterized by that the high voltage generated by the high-voltage AC source (30) is between 70 kV and more than 800 kV. [4] Arrangement according to claim 2 or 3, characterized by that the ratio between high voltage and medium voltage is 5:1 or higher. [5] Arrangement according to one of the preceding claims, characterized bythat the discharge resistor (41) is dimensioned such that it discharges the energy enclosed in the inductive load (10) in such a way that within half an AC voltage period the voltage across the inductive load (10) becomes zero. [6] Arrangement according to one of the preceding claims, characterized by that the discharge resistor (41) is dimensioned according to R <LCL2N2CL, where R is the resistance value of the discharge resistor (41), L is the main reactance of the inductive load (10), N is the voltage ratio between primary voltage and secondary voltage of the inductive load, and C L the stray capacitance of the inductive load (10) are. [7] Arrangement according to one of the preceding claims, characterized by that the controllable switching element (42) has a switching time which is shorter than the switching time of the disconnector (20). [8] Arrangement according to one of the preceding claims, characterized by that the controllable switching element (42) is a semiconductor switching element, in particular a thyristor, or a fast mechanical medium-voltage circuit breaker. [9] Arrangement according to one of the preceding claims, characterized by that respective control terminals of the circuit breaker (20) and the switching element (42) are connected to a common output of a control unit (60) in order to receive the same control signal (CS). [10] Arrangement according to one of the preceding claims, characterized by that the inductive load (10) comprises a primary winding (11), wherein the primary winding (11) and the secondary winding (12) are surrounded by an insulating fluid. [11] A system for interrupting current in a high-voltage line of a power system, which uses a current interrupting arrangement according to any one of the preceding claims per phase. [12] A method for interrupting current in a high-voltage line of a power system, which uses a current interrupting arrangement according to any one of claims 1 to 11, the method comprising the step of: - controlling the circuit breaker (20) and the switching element (42) during operation of the arrangement by means of a control signal in order to close the switching element (42) in the resistance arrangement (40) immediately before an arc occurs between contacts of the circuit breaker (20) during the current interruption. [13] Method according to claim 12, wherein a same control signal (CS) provided at a common output of a control unit (60) is processed as the control signal. [14] Method according to claim 12 or 13, wherein the isolating switch (20) is switched to conducting during operation of the arrangement and the switching element (42) is switched to blocking.

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