Arc recognition

Abstract

For the detection of an arc (arc) in a setting unit (1) for transmitting a direct voltage (U_dc), a communication transformer (4) with a primary winding (L1) and a secondary winding (L2) is provided, wherein the secondary winding (L2) is connected to a transmitting device (3), which is designed to apply a communication signal (i_Tx) to the secondary winding (L2) of the communication transformer (4), and the primary winding (L1) is connected to one of the direct voltage lines (DC+, DC-), in order to transmit a communication signal (i_Tx') converted by the communication transformer (4) to one of the direct voltage lines (DC+, DC-). For the detection of an arc signal (i_arc) in the setting unit (1) caused by an arc (arc), the secondary winding (L2) is connected to an arc detection unit (5), which is designed to detect an arc signal (i_arc') converted by the communication transformer (4).

Description

[0001] This application is a divisional application of the invention patent application filed on July 26, 2019, with application number 201980049352.7, international application number PCT / EP2019 / 070225, and entitled "Electric Arc Recognition". Technical Field

[0002] This invention relates to a setting unit for transmitting DC voltage from a DC voltage source to at least one DC voltage absorber via at least two DC voltage lines. A communication transformer with a primary coil and a secondary coil is provided, wherein the secondary coil is connected to a transmitting device configured to apply a communication signal to the secondary coil of the communication transformer, and the primary coil is connected to the DC voltage lines to transmit the communication signal converted by the communication transformer to one of the DC voltage lines. A signal processing circuit is connected between the secondary coil on the secondary side and an arc detection unit, wherein the signal processing circuit is configured to process the secondary AC current flowing through the secondary coil for the arc detection unit. Furthermore, this invention relates to a method for detecting an arc signal generated by an arc in a setting unit, the setting unit being used to transmit DC voltage from at least one DC voltage source to at least one DC voltage absorber via DC voltage lines, wherein a communication signal is applied to the secondary coil of the communication transformer and the converted communication signal is transmitted to the DC voltage lines via the primary coil of the communication transformer, wherein the arc signal converted by the communication transformer is processed to identify the arc signal in the setting unit. Background Technology

[0003] In a DC voltage system, at least one DC voltage source provides usable DC voltage, which is transmitted via a DC voltage line to a DC voltage absorber. For example, a number of solar panels or solar cells in a photovoltaic system, or a battery, can serve as a DC voltage source. Simultaneously, a DC voltage is generated on the solar panels or solar cells according to the corresponding solar radiation. An inverter can be used, for example, as a DC voltage absorber. The inverter converts the DC voltage to AC voltage and supplies this AC voltage to the power grid or provides the generated AC voltage to electrical loads (such as motors or batteries).

[0004] In many setup units, communication with existing DC voltage sources and / or DC voltage absorbers is desired. Communication signals sent by a control unit can, for example, be used to synchronize individual solar panels. Particularly in the event of a fault, the communication signals can also be used to disconnect the DC voltage source or other components of the setup unit. Therefore, communication signals can be transmitted, for example, via a dedicated communication line or directly via an existing DC voltage line—using so-called PowerLine Communication (PLC). In the case of PowerLine Communication, the communication signal is modulated onto an existing fundamental signal used for energy transfer in a known manner and transmitted as a fundamental signal along with the DC voltage. The receiving unit can then reacquire and analyze the demodulated communication signal.

[0005] In fault conditions, parasitic arcs can ignite in DC voltage systems. An arc is generated by a voltage between two spaced-apart components. Therefore, it can be initially defined that the two components are in electrical contact. However, if this electrical contact fails or is interrupted, a gap is created between the two components. A high voltage can ionize the air between the two components (which would normally act as insulation), potentially generating an arc. However, an arc can also be generated through defective insulation material (e.g., trapped gas) between two components with a high potential difference. This results in insulation breakdown, generating an arc. Arcs typically do not disappear on their own and must be actively extinguished, for example, by shutting off the power. However, arc identification is a fundamental challenge, as often only ignition is detected, while burning arcs are frequently undetectable. After ignition, the arc signal must be distinguished from the noise that appears, which is impossible with methods known to date. When an arc is burning, it has a very low voltage level and may not change transiently over time.

[0006] Therefore, it is particularly important to detect the inevitable electric arcs in photovoltaic equipment and then quickly and reliably disconnect the system. Thus, additional hardware is typically required for arc detection. US2014 / 084942A1, for example, discloses an arc detection method activated during power line communication transmission interruptions. However, US2014 / 084942A1 does not provide information on the precise construction design of the arc detection unit. DE 10 2014 104 205 A1 discloses a photovoltaic device in which power line communication is performed via a transformer connected to a DC voltage line. Furthermore, an arc detection circuit is provided in an inverter. The inverter is connected to the photovoltaic device via a disconnect device consisting of a coil and a switch contact, and is also capable of receiving PLC signals via the disconnect device. Summary of the Invention

[0007] The purpose of this invention is to achieve arc detection in a setting unit for transmitting DC voltage, which incurs as little hardware cost as possible.

[0008] According to the present invention, this objective is achieved by a setting unit in which the secondary side of a communication transformer is connected to an arc detection unit configured to detect the arc signal converted by the communication transformer in order to identify the arc signal induced by the arc. A signal processing circuit is connected between the secondary coil on the secondary side and the arc detection unit, and this signal processing circuit is configured to process the secondary alternating current flowing through the secondary coil for the arc detection unit. This objective is also achieved by a method in which the arc signal converted by the communication transformer is processed to identify the arc signal in the setting unit, and the secondary alternating current flowing through the secondary coil is processed for arc detection. Therefore, even when the arc has already ignited, the arc signal induced by the arc can be used to detect the arc.

[0009] Therefore, a communication transformer already present in the setup unit can be used to convert the arc signal into a converted arc signal. The communication transformer is originally used to convert a communication signal applied to the secondary coil by the transmitting device to a primary coil connected to a DC voltage line, through which the converted communication signal is transmitted. The communication transformer is typically located in the negative DC voltage line. This is especially true when at least two DC voltage sources or two DC voltage absorbers are present in the setup unit, as this also creates at least two positive DC voltage lines. Because the communication transformer is located in a common negative DC voltage line, it can communicate with multiple DC voltage absorbers or DC voltage sources. Otherwise, each positive DC voltage line would require a separate communication transformer. However, the communication transformer can also be located or integrated into a DC voltage absorber, a DC voltage source, or another component of the setup unit, such as an inverter, a micro-inverter, an optimizer, etc.

[0010] According to the present invention, a communication transformer is additionally used to convert the arc signal present on the primary coil to the secondary coil, wherein the converted arc signal is identified by an arc detection unit. Therefore, no additional transformer is required for arc detection.

[0011] A DC voltage source may include at least one photovoltaic cell. Therefore, a DC voltage source may also include photovoltaic cells connected in series and / or parallel, or other different or identical DC voltage sources with different connections, such as photovoltaic energy storage devices or (internal logistics) batteries. A DC voltage absorber may include at least one inverter. A DC voltage absorber may also include, for example, electrical consumers such as DC voltage / DC voltage stages, motors, lighting fixtures, etc. Particularly in bidirectional setups—e.g., with both a battery and an inverter—the DC voltage source and DC voltage absorber may interchange roles depending on the operating mode.

[0012] The primary alternating current on the primary coil of the communication transformer consists of a converted communication signal and an arc signal, thus forming a mixed signal, in the case of a communication signal being transmitted and an arc occurring. Similarly, the secondary alternating current on the secondary side of the communication transformer also consists of a communication signal and a converted arc signal, similarly forming a (converted) mixed signal. To identify the arc signal induced by the arc, the communication signal can be attenuated relative to the arc signal.

[0013] A signal processing circuit is connected between the secondary coil on the secondary side and the arc detection unit, wherein the signal processing circuit is configured to process the secondary alternating current flowing through the secondary coil for the arc detection unit.

[0014] The signal processing circuit advantageously includes a resistor and a capacitor connected in series, wherein the capacitor is connected in parallel with the secondary coil on the secondary side, and the arc detection unit is connected to the resistor in order to process the voltage present on the resistor to identify the arc. Since the arc induces a high-frequency voltage, it is advantageous to perform voltage analysis in the frequency range, wherein a high-frequency sensor can be provided.

[0015] The transmitting device can be connected only to the secondary coil to convert the communication signal to the primary coil. Alternatively, the transmitting device can be connected to another secondary coil via a subtraction circuit, which receives the converted mixed signal from the primary coil. The subtraction circuit is configured to subtract the communication signal transmitted by the transmitting device from the converted mixed signal to obtain a converted arc signal, which is then transmitted to the arc detection unit for detection. The converted mixed signal received by the other secondary coil consists of the converted arc signal and the communication signal, where other signal components such as noise may be present. Since the (converted) mixed signal is generated by converting a mixed signal from the primary coil to the other secondary coil, the mixed signal is naturally also converted from the primary coil to the primary coil. However, the converted mixed signal on the secondary coil may not be consistent with the converted mixed signal on the other secondary coil, for example, due to a difference in conversion ratio between the two secondary coils. A mixing circuit is generated by a configuration unit consisting of a secondary coil, another secondary coil, and a subtraction circuit. This hybrid circuit can be configured to replace or be added to the signal processing circuit connected to the primary coil.

[0016] The transmitting device is advantageously configured to transmit a communication signal, preferably a disconnection signal, to the DC voltage source and / or DC voltage absorber when an arc is detected by the arc detection unit. For this purpose, a control unit may also be provided, which obtains information about the presence of an arc in the setting unit via the arc detection unit and then transmits a corresponding communication signal via the transmitting device, for example, to disconnect the DC voltage absorber and / or the DC voltage source and / or other components of the setting unit.

[0017] Alternatively, the transmitting device can transmit a communication signal to a DC voltage source and / or a DC voltage absorber when no arc is detected, and stop transmitting the communication signal only when an arc is detected. Therefore, the communication signal can be equivalent to a so-called keep-alive signal.

[0018] The setting unit may be equipped with at least two DC voltage absorbers and / or at least two DC voltage sources, wherein a current sensor for detecting at least one low-frequency portion of an arc signal, preferably an arc signal, is respectively provided on the at least two DC voltage absorbers or at least two DC voltage sources to determine the DC voltage absorber or DC voltage source associated with the arc.

[0019] Thus, when an arc is detected by the arc detection unit, in order to identify the position of the arc in the setting unit - which has at least two DC voltage absorbers and / or at least two DC voltage sources - the arc signal, preferably at least one low-frequency component of the arc signal, can be detected via a current sensor provided on the DC voltage absorber or DC voltage source, so as to determine the DC voltage absorber or DC voltage source associated with the arc.

[0020] If multiple DC voltage sources are provided (or multiple DC voltage sources are provided), these DC voltage sources typically share a negative DC voltage line. Since communication transformers are usually located in the negative DC voltage line, arcs can generally be detected when using communication transformers. If an arc appears in a negative DC voltage line or a DC voltage absorber or DC voltage source, although it can be detected by an arc detection unit, the associated DC voltage line, DC voltage absorber, or DC voltage source cannot be identified. Circuit sensors located on each DC voltage absorber or DC voltage source can help in this regard. If an arc is detected by the arc detection unit, the current characteristic curves of all current sensors can be observed, and thus it can be determined which current sensor the arc signal flows through. Therefore, the location of the arc in the system can be determined, and it can be identified in which branch the arc appears, i.e., which DC voltage line, DC voltage absorber, or DC voltage source. Attached Figure Description

[0021] The following will refer to the appendix. Figures 1 to 4 The invention is described in detail below, and the accompanying drawings exemplify, schematically, and non-limitingly illustrate advantageous structural designs of the invention. In the drawings:

[0022] Figure 1 The present invention provides a unit having an arc detection unit;

[0023] Figure 2 This invention provides a unit having multiple current absorbers;

[0024] Figure 3 An arc detection unit with a signal processing unit;

[0025] Figure 4 This is a hybrid circuit with an additional secondary coil and a subtraction circuit. Detailed Implementation

[0026] exist Figure 1The diagram illustrates the setup unit 1 of the present invention for transmitting a DC voltage U_dc. A DC voltage source 2 is connected to a DC voltage absorber 6 via a positive DC voltage line DC+ and a negative DC voltage line DC-. The DC voltage source 2 may include, for example, one or more solar cells that provide electrical energy, which is transmitted to the DC voltage absorber 6 as the DC voltage U_dc. The DC voltage absorber 6 may include, for example, an inverter or a rectifier and is used to supply power to a power grid or to supply power to a consumer. Alternatively, an electrical consumer can be considered as the DC voltage absorber 6.

[0027] In particular, different structures of DC voltage sources 2 and DC voltage absorbers 6 can be set in photovoltaic equipment, so that, for example, each solar panel as a DC voltage source 2 can be connected to an inverter as a DC voltage absorber 6 via a DC voltage line DC+, DC-. Multiple DC voltage sources 2 and / or DC voltage absorbers 6 can also share a portion of the DC voltage line DC+, DC-. Solar panels as DC voltage sources 2 can also be connected in series and / or in parallel. Therefore, different structures of DC voltage sources 2, DC voltage absorbers 6, and DC voltage lines DC+, DC- can be considered, and thus the present invention is not limited to these structures. Figure 1 The structure is shown in the diagram. When using a battery, depending on whether the battery is discharging or charging, it can be considered either a DC voltage source 2 or a DC voltage absorber 6. Thus, depending on the operating mode, an inverter or charger can be used as a DC voltage source 2 for a battery acting as a DC voltage absorber 6, or a battery can be used as a DC voltage absorber 6 for an inverter or charger acting as a DC voltage source 2.

[0028] Figure 2 A similar configuration unit is disclosed, which has a DC voltage source 2, but also multiple DC voltage absorbers 6, 6'. The DC voltage absorbers 6, 6' share a negative DC voltage line DC- and each has an associated positive DC voltage line DC+, DC+'. Of course, multiple DC voltage sources 2, etc., can also be considered in the configuration unit. Multiple DC voltage absorbers 6, 6' can also constitute multiple stages of a photovoltaic device or an inverter.

[0029] At least one communication transformer 4 is provided in the setting unit 1. This communication transformer includes a primary coil L1 on the primary side and a secondary coil L2 on the secondary side. The primary coil L1 is connected to a DC voltage line DC+ and DC-, and the secondary side is connected to a transmitting device 3. The connection of the primary coil L1 to the negative DC voltage line DC- is exemplary; the primary coil L1 can also be connected to the positive DC voltage line DC+. This is particularly true in setting units with multiple positive DC voltage lines DC+ and DC+', such as in… Figure 2 As shown in the figure, the primary coil L1 of the communication transformer 4 should typically be placed in the negative DC voltage line DC- so that the communication transformer 4 can communicate with all existing DC voltage sources 2 or DC voltage absorbers 6, 6'.

[0030] The primary alternating current l1 flowing through the primary coil L1 is converted into secondary alternating current l2 flowing through the secondary coil L2 via the communication transformer 4, and vice versa. The communication transformer 4 advantageously has a transformation ratio of 1:1, 1:2, or 1:4 from the primary side to the secondary side. Furthermore, the communication transformer 4 may have a ferrite core, such as a high-flux core, which preferably has particularly advantageous saturation characteristics for direct current.

[0031] A communication signal i_Tx can now be transmitted to the secondary coil L2 on the secondary side via the transmitting device 3 within the power line communication range. This converts the communication signal i_Tx to a converted communication signal i_Tx' on the primary coil L1 via the communication transformer 4. The converted communication signal i_Tx' on the primary coil L1 is then superimposed or modulated onto the current flowing through the negative DC voltage line DC-, thereby affecting the DC voltage U_dc. The converted communication signal i_Tx' is then transmitted via DC voltage lines DC+ and DC- to DC voltage source 2 and / or DC voltage absorbers 6 and 6', and received and demodulated by receiving units 20 and 60 provided on DC voltage source 2 and / or DC voltage absorbers 6 and 6'. To close the loop for transmitting the converted communication signal i_Tx' via DC voltage lines DC+ and DC-, a filter capacitor Cf is preferably used in or on the DC voltage absorbers 6 and 6' to circulate the converted communication signal i_Tx'.

[0032] exist Figure 1 In this configuration, only one receiving unit 20 is provided on the DC voltage source 2. Alternatively, a receiving unit 60 for the converted communication signal i_Tx' can also be provided on the DC voltage absorbers 6 and 6'. The receiving units 20, 20' or 60, 60' can be located on either the negative DC voltage line DC- or the positive DC voltage line DC+. Figure 2For example, receiving units 60 and 60' are respectively set on the DC voltage source 2 and on multiple DC voltage absorbers 6 and 6'. For example, pulses used to detect interference points, signals used for impedance measurement, noise level measurement signals, synchronization signals or control signals for each power source 2 such as solar cells can be used as communication signals i_Tx.

[0033] An electric arc may occur in the setting unit, for example, in the plug-in connections of the DC voltage source 2, DC voltage absorbers 6, 6', DC voltage lines DC+, DC+', DC-, or another component of the setting unit 1. For example, in Figure 1 , 3 In arc 4, the arc is marked as the negative DC voltage line DC- in the lightning, while Figure 2 The lightning is marked as a positive DC voltage line DC+'. If an arc ignites, an arc signal i_arc is generated in the DC voltage lines DC+, DC+', and DC-, which is superimposed with the current flowing into the DC voltage lines DC+, DC+', and DC- generated by the DC voltage U_dc. According to the invention, the secondary coil L2 of the communication transformer 4, which is already installed for transmitting the communication signal i_Tx, is connected to an arc detection unit 5. Therefore, the arc signal i_arc generated by the arc on the DC voltage lines DC+ and DC- is converted from the primary coil L1 of the communication transformer 4 into a converted arc signal i_arc', which is available on the secondary coil L2. The arc signal i_arc is here at a high frequency, so a filter capacitor Cf for closing the circuit can be provided in or on the DC voltage absorber 6. Here, the filter capacitor is connected between the negative DC voltage line DC- and the corresponding positive DC voltage lines DC+ and DC+'. Figures 1 to 4 In this context, the filter capacitor Cf is respectively set on DC voltage absorbers 6 and 6', but it can also be an integral part of the corresponding DC voltage absorbers 6 and 6'.

[0034] If an electric arc (arc) occurs simultaneously with the transmission of a communication signal i_Tx, then the arc signal i_arc and the converted communication signal i_Tx' are added to the primary coil L1 to form the primary AC current l1~. The communication transformer converts the primary AC current l~ in the primary coil L1 into the secondary AC current l2~ in the secondary coil L2. On the secondary side, the communication signal i_Tx and the converted arc signal i_arc' are added in a similar manner to form the secondary AC current l2~. In this superposition, the primary AC current l1~ and the secondary AC current l2~ constitute a mixed signal.

[0035] If no arc is generated in the setting unit, then the primary AC power supply L1~ or the secondary AC power supply L2~ will naturally not include the arc signal i_arc or the converted arc signal i_arc', but will include the converted communication signal i_Tx' or the communication signal i_Tx. If no communication signal i_Tx is transmitted, then the primary AC power supply L1~ or the secondary AC power supply L2~ will naturally not include the converted communication signal i_Tx' or the communication signal i_Tx, but will include the arc signal i_arc or the converted arc signal i_arc' if an arc is generated. Of course, in all cases, not only the primary AC power supply L1~ but also the secondary AC power supply L2~ can contain other parts of the AC power supply, such as other signals, interference, etc. Therefore, it is possible to transmit a communication signal i_Tx through the transmitting device 3 and identify an arc or a converted arc signal i_arc' through the arc detection unit at the same time.

[0036] Because an arc detection unit 5 is provided on the secondary side, there is no need to set up additional complex hardware for arc detection, such as an additional transformer. In particular, when an arc is detected by the arc detection unit 5, it is advantageous to send a switch-off signal, either as a communication signal i_Tx or as a converted communication signal i_Tx', to the DC voltage source 2 and / or the DC voltage absorbers 6, 6' via the transmitting device 3. For this purpose, a control unit can be provided, connected to the arc detection unit 5 and the transmitting device 3, which receives corresponding information from the arc detection unit 5 when an arc is detected and causes the transmitting device 3 to send a communication signal i_Tx to the DC voltage source 2 and / or the DC voltage absorbers 6, 6', for example, to disable the DC voltage source 2 or the DC voltage absorbers 6, 6' and thereby eliminate the arc. A warning signal can also be issued when an arc is detected. If a so-called "keep-alive" signal is sent as a communication signal i_Tx, and the communication signal i_Tx is no longer sent due to the detection of an arc, then the DC voltage source 2 or the DC voltage absorbers 6 and 6' can be disabled. Receiving units 20 and 60 are provided accordingly to receive the disconnect signal or the "keep-alive" signal as a communication signal.

[0037] exist Figure 2As previously described, multiple DC voltage absorbers 6 and 6' are provided. If an arc occurs in a positive DC voltage line DC+ or in one of the DC voltage absorbers 6 or 6', the arc signal i_arc is also transmitted in the negative DC voltage line DC- and can be detected by the arc detection unit 5 according to the present invention. However, this usually cannot pinpoint the location of the arc. To determine which branch the arc occurs in, that is, in which DC voltage line DC-, DC+, DC+', or in which DC voltage absorber 6 or 6' (or in the case of multiple DC voltage sources 2, in which DC voltage source 2), current sensors S_boost and S_boost' can be provided on or in the DC voltage absorbers 6 or 6' (or DC voltage absorbers 2). These current sensors S_boost and S_boost' are preferably integral components of the DC voltage absorbers 6 or 6'. If a filter capacitor Cf is also set as an integral part of the DC voltage absorbers 6 and 6', then the current sensors S_boost and S_boost' can be connected downstream of the filter capacitor Cf in the circuit.

[0038] If an arc is detected by the arc detection unit 5, then the branch in which the arc appears can be identified by the corresponding current sensors S_boost and S_boost'. This is possible because the arc signal i_arc, or at least a low-frequency component of the arc signal i_arc, flows only through the relevant current sensors S_boost and S_boost', and not through the current sensors S_boost and S_boost' belonging to other DC voltage absorbers 6 and 6'.

[0039] The existing current sensors on the DC voltage absorbers 6 and 6' can be used as current sensors S_boost and S_boost', respectively. In particular, the inverter, acting as DC voltage absorbers 6 and 6', has such current sensors. The current sensor S_boost cannot reliably identify a burning electric arc on its own and therefore must be used in conjunction with the arc detection unit 5.

[0040] Figure 3An advantageous structural design of the present invention is illustrated. The communication transformer 4 has a secondary coil L2 on the secondary side and a primary coil L1 on the primary side. The primary coil L1 is connected to DC voltage lines DC+ and DC-, and a signal processing circuit 50 is connected between the secondary coil L2 and the arc detection unit 5. However, the arc signal i_arc is high-frequency, making it difficult to detect over a short period of time and, except for a transient process, behaves almost like a DC current during ignition. Therefore, the signal processing circuit 50 is used to process the secondary AC current l2~ flowing through the secondary coil L2. Thus, it becomes possible to more easily detect the arc signal i_arc or the converted arc signal i_arc' by the arc detection unit 5. Therefore, the signal processing circuit 50 can be advantageously designed to better identify the arc arc during the transmission of the communication signal i_Tx. This can be achieved by attenuating the communication signal i_Tx relative to the converted arc signal i_arc' by the arc detection unit 5. A filter capacitor Cf can be used on the DC voltage absorbers 6, 6', for example as the input capacitor of the inverter for the DC voltage absorbers 6, 6'. For this purpose, the signal processing circuit 50 may include a resistor R and a series capacitor C with a preferred capacitance value of 70 to 120 nF, wherein the fundamental frequency can be set in the range of kHz, preferably 130 kHz. The capacitor C is connected in parallel with the secondary coil L2 on the secondary side. The arc detection unit 5 is also connected to the resistor R to process the voltage U_R present on the resistor R in order to identify the arc signal i_arc'. Since the transmitting unit 3 is also connected in series with the secondary coil, a resonant circuit is generated, which, from the perspective of the arc detection unit 5, facilitates a communication signal i_Tx attenuated by up to 1 / 10 relative to the converted arc signal i_arc'. This generates a voltage U on the resistor R, which is proportional to i_Tx / 10 + i_arc'. Therefore, in particular, when transmitting a communication signal i_Tx, the converted arc signal i_arc' can be reliably identified, and the arc arc appearing in the setting unit 1 can be reliably identified in this way.

[0041] exist Figure 3 In the illustrated design, the transmitting device 3 and the arc detection unit 5 are connected to the secondary coil L2. As another preferred design, a communication transformer 4 with a second secondary coil L2' can also be provided, wherein the transmitting device 3 is connected to the other secondary coil L2' via a subtraction circuit 7 – as shown in… Figure 4As shown in the diagram. The transmitting device 3 is also connected to a secondary coil L2 for converting the communication signal i_Tx onto the primary coil L1. This creates a hybrid circuit. The secondary coil L2' here obtains a hybrid signal i_Tx+i_arc' via the primary coil L1, which consists of the communication signal i_Tx and the converted arc signal i_arc'. The subtraction circuit 7 is configured to subtract the communication signal i_Tx transmitted by the transmitting device 3 from the received hybrid signal i_Tx+i_arc', thus obtaining the converted arc signal i_arc'. For this purpose, a negative input terminal is connected to the transmitting device 3, and a positive input terminal is connected to the additional secondary coil. The converted arc signal i_arc' can be transmitted to the arc detection unit 5 for arc detection.

[0042] However, the arc signal i_arc is usually converted to the secondary side via the primary coil L2. Now, to prevent an arc signal i_arc' converted via the primary coil L2 from also being transmitted to the negative input of the subtraction circuit 7, a mechanism can be added to the transmitting device—such as in… Figure 4 As shown in the diagram, an additional amplifier is provided to ensure that only the communication signal i_Tx is transmitted to the negative input of the subtraction circuit 7. This prevents feedback of the communication signal i_Tx, which is applied separately by the transmitting device 3 to the secondary coil L2 and the subtraction circuit 7, here achieved via two separate amplifiers.

[0043] Of course, a construction scheme could also be considered, which would construct a—for example, according to Figure 3 - Signal processing circuit 50 and a according to Figure 4 A combination of hybrid circuits is used to reliably identify arcs.

Claims

1. A setup unit (1) for detecting an electric arc when transmitting a DC voltage (U_dc) from at least one DC voltage source (2) via at least two DC voltage lines (DC+, DC+', DC-) to at least one DC voltage absorber (6, 6'), wherein a communication transformer (4) having a primary coil (L1) and a secondary coil (L2) is provided, wherein the secondary coil (L2) is connected to a transmitting device (3) configured to apply a communication signal (i_Tx) to the secondary coil (L2) of the communication transformer (4). The primary coil (L1) is connected to one of the DC voltage lines (DC+, DC-) to transmit the communication signal (i_Tx') converted by the communication transformer (4) to one of the DC voltage lines (DC+, DC-). To identify the arc signal (i_arc) induced by the arc in the setting unit (1), the secondary coil (L2) is connected to the arc detection unit (5), which is configured to detect the arc signal (i_arc') converted by the communication transformer (4). The secondary coil (L2) is characterized by: The transmitting device (3) is connected to another secondary coil (L2') via a subtraction circuit. The other secondary coil obtains a mixed signal (i_Tx+i_arc') via the primary coil (L1). The subtraction circuit (7) is configured to subtract the communication signal (i_Tx) sent by the transmitting device (3) from the mixed signal (i_Tx+i_arc') to obtain a converted arc signal (i_arc') and transmit the converted arc signal to the arc detection unit (5) for detection.

2. The setting unit (1) as described in claim 1, characterized in that: A signal processing circuit (50) is connected between the secondary coil (L2) on the secondary side and the arc detection unit (5), wherein the signal processing circuit (50) is configured to process the secondary alternating current (l2~) flowing through the secondary coil (L2) for the arc detection unit (5).

3. The setting unit (1) as described in claim 1 or 2, characterized in that: The at least one DC voltage source (2) includes at least one photovoltaic cell, and the at least one DC voltage absorber (6, 6') includes at least one inverter.

4. The setting unit (1) as described in claim 2, characterized in that: The signal processing circuit (50) includes a resistor (R) and a capacitor (C) connected in series, wherein the capacitor (C) is connected in parallel with the secondary coil (L2) on the secondary side and the arc detection unit (5) is connected to the resistor (R) to process the voltage (U) present on the resistor (R) to identify the arc (i_arc).

5. The setting unit (1) as described in claim 1 or 2, characterized in that: The transmitting device (3) is configured to transmit a communication signal (i_Tx) to a DC voltage source (2) and / or a DC voltage absorber (6, 6') based on whether an arc (i_arc) is detected or not by the arc detection unit (5).

6. The setting unit (1) as described in claim 1 or 2, characterized in that: The system is equipped with at least two DC voltage absorbers (6, 6') and / or at least two DC voltage sources (2), and a current sensor (S_boost) for detecting the arc signal (i_arc) is provided on each of the at least two DC voltage absorbers (6, 6') or the at least two DC voltage sources (2) to determine the DC voltage absorber (6, 6') or DC voltage source (2) associated with the arc (arc).

7. The setting unit (1) as described in claim 1 or 2, characterized in that: The system is equipped with at least two DC voltage absorbers (6, 6') and / or at least two DC voltage sources (2), and a current sensor (S_boost) is provided on each of the at least two DC voltage absorbers (6, 6') or the at least two DC voltage sources (2) to detect at least one low-frequency component of the arc signal (i_arc) in order to determine the DC voltage absorber (6, 6') or DC voltage source (2) associated with the arc (arc).

8. A method for detecting an arc signal (i_arc) generated by an electric arc in a setting unit (1), the setting unit being used to transmit a DC voltage (U_dc) from at least one DC voltage source (2) via at least two DC voltage lines (DC+, DC-) to at least one DC voltage absorber (6, 6'), wherein a communication signal (i_Tx) is applied to the secondary coil (L2) of a communication transformer (4), and a converted communication signal (i_Tx') is transmitted via the primary coil (L1) of the communication transformer (4) to the DC voltage lines (DC+, DC+', DC-), wherein, In order to identify the arc signal (i_arc) in the setting unit (1), the arc signal (i_arc') converted by the communication transformer (4) is processed, characterized in that: another secondary coil (L2') obtains a mixed signal (i_Tx+i_arc') from the primary coil (L1), and subtracts the communication signal (i_Tx) from the mixed signal (i_Tx+i_arc') in order to obtain the converted arc signal (i_arc').

9. The method as described in claim 8, characterized in that: The secondary alternating current (l2~) flowing through the secondary coil (L2) is processed for arc detection.

10. The method as described in claim 8 or 9, characterized in that: In order to identify the arc signal (i_arc) induced by the electric arc (arc), the communication signal (i_Tx) is attenuated relative to the arc signal (i_arc).

11. The method as described in claim 8 or 9, characterized in that: Upon detection of an electric arc, a communication signal (i_Tx) is sent to the at least one DC voltage source (2) and / or the at least one DC voltage absorber (6, 6').

12. The method as described in claim 8 or 9, characterized in that: When no arc (i_arc) is detected, a communication signal (i_Tx) is transmitted to the at least one DC voltage source (2) and / or the at least one DC voltage absorber (6, 6'), and when an arc (i_arc) is detected, the transmission of the communication signal (i_Tx) is stopped.

13. The method as described in claim 8 or 9, characterized in that: When an arc is detected by the arc detection unit (5), in order to identify the location of the arc in the setting unit (1) having at least two DC voltage absorbers (6, 6') and / or at least two DC voltage sources (2), the arc signal (i_arc) is detected via a current sensor (S_boost, S_boost') set on the associated DC voltage absorber (6, 6') or DC voltage source (2) in order to determine the DC voltage absorber (6, 6') or DC voltage source (2) associated with the arc.

14. The method as described in claim 8 or 9, characterized in that: Upon detection of an electric arc, a disconnect signal is sent to the at least one DC voltage source (2) and / or the at least one DC voltage absorber (6, 6').

15. The method as described in claim 8 or 9, characterized in that: When an arc is detected by the arc detection unit (5), in order to identify the location of the arc in the setting unit (1) having at least two DC voltage absorbers (6, 6') and / or at least two DC voltage sources (2), at least one low-frequency component of the arc signal (i_arc) is detected via a current sensor (S_boost, S_boost') disposed on the associated DC voltage absorber (6, 6') or DC voltage source (2) in order to determine the DC voltage absorber (6, 6') or DC voltage source (2) associated with the arc.

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