DE102012022919A1 - Overvoltage protective wiring structure for photovoltaic plants, has wires of same polarity that are connected on common varistor, and wires of same polarity with different input channels that are decoupled thought spark gap - Google Patents

Abstract

The overvoltage protective wiring structure has the inverters (4) that are provided with several input channels. The electrical connection region is formed between the photovoltaic modules (5,6) and the direct current (DC) voltage input side of the inverter. A varistor (1,2) is connected with pole spacer wire against the ground potential. The wires of the same polarity are connected on a common varistor. The wires of the same polarity with different input channels are decoupled thought the spark gap (7-10).

Description

The invention relates to an overvoltage protection circuit for photovoltaic systems with inverters, which have a plurality of input channels, wherein in the electrical connection region between the photovoltaic modules and the DC input side of the inverter at least one varistor is connected to ground potential at each pole core, according to the preamble of claim 1.

Multi-pole photovoltaic surge arresters, even with DC switching devices for systems between 600 V and 1200 V are state of the art. Such overvoltage protection devices have a fault-resistant Y-protective circuit of varistors and plus a disconnecting and short-circuiting device. The aforementioned fault-resistant Y-circuit consists of three varistor protection phases and makes it possible to protect photovoltaic systems with DC voltages in the above-mentioned range from overvoltages. Since two modules are always connected in series, the probability of overloading one of the protection modules is significantly reduced and it is such a protected system resistant to earth faults.

Since the risk of overloading a protection module can not be completely ruled out and there is a possibility that an overload of the varistors in the surge protection device triggers a fire, thermally acting shutdown devices are known, which disconnect the varistor in the thermal overload case of the circuit.

Due to the separate guidance of different input channels for inverters to optimize the overall efficiency, it is necessary to realize for each channel its own surge protection circuit.

The wiring of corresponding channels of an inverter can be found, for example, in the installation instructions for the product DS50PV from CITEL, downloadable from www.citel.de.

Since photovoltaic inverters of smaller and medium power already have several mpp inputs, the expense of overvoltage protection, both in terms of space and cost, is very high.

It is therefore an object of the invention to provide a further developed overvoltage protection circuit for photovoltaic systems with inverters, which comprise a plurality of input channels, which provides sufficient protection for the required overvoltage protection devices with minimal effort, without influencing the line conductors during normal operation of the photovoltaic system.

The object of the invention is achieved by an overvoltage protection circuit for photovoltaic systems according to the feature combination according to claim 1, wherein the dependent claims comprise at least expedient refinements and developments.

It is therefore assumed that an overvoltage protection circuit for photovoltaic systems with inverters having a plurality of input channels, so-called mpp channels, wherein connected in the electrical connection region between the photovoltaic modules of the photovoltaic system and the DC input side of the respective inverter at each pole core at least one varistor against ground potential is to achieve surge protection.

According to the invention, all the lines of the same polarity are connected to a common varistor, wherein the line wires of the same polarity, but different input channels are decoupled via at least one spark gap.

In view of the teaching described above, it is possible, a Varistorschutzbeschaltung, z. B. in Y-circuit arrangement for multiple input channels, without the protective effect is impaired, whereby the number of necessary surge arresters can be reduced.

In one embodiment of the invention, the overvoltage protection circuit has at least three Y-connected varistors, wherein two varistors are arranged in parallel and, for this parallel connection, the third varistor leads in series to the ground potential. One of the parallel-connected varistors is connected via a spark gap with the Pluspolleitungsader and the other of the parallel-connected varistors via a further spark gap with the Minuspolleitungsader in combination.

Such a Y-circuit of the varistors can be designed as a central protection circuit for all input channels of a respective inverter.

The spark gaps are preferably designed as gas discharge arresters.

The invention will be explained below with reference to an embodiment and a figure.

The figure shows a schematic circuit diagram of an overvoltage protection circuit for photovoltaic systems with an inverter, which has two mpp input channels in the example shown.

The actual overvoltage protection circuit is made of the varistors 1 to 3 formed, which are connected according to embodiment and preferably in a so-called Y-circuit and of which the varistor 3 with the ground potential of the PV inverter 4 electrically connected.

The photovoltaic modules 5 respectively. 6 each with one input channel A +, A- or B + and B- of the inverter 4 in electrical connection.

The cable cores of the same polarity are common to the varistor 1 leading trained, with a decoupling of the wires between the photovoltaic modules 5 and 6 over the spark gaps 7 and 8th he follows.

The decoupling of the Minuspolleitungsadern the photovoltaic modules 5 and 6 takes place over the spark gaps 9 and 10 ,

From the basic circuit it can be seen that in each case the varistor 1 respectively. 2 over the associated spark gaps 7 . 8th respectively. 9 . 10 is connected to all lines of the same potential.

The spark gaps 7 . 8th ; 9 . 10 are used to avoid mutual interference during normal operation.

In one embodiment, the spark gaps are gas discharge tubes.

In principle, it is also possible to reduce the number of spark gaps per varistor connection to n-1, where n represents the number of DC lines to be protected.

The presented principle of decoupling via spark gaps can also be used if similar configurations are used instead of the illustrated Y circuit of the varistors.

Due to the special wiring using a central surge arrester, costs can be saved and compact designs realized in accordance with the task.

Claims (4)

Surge protection circuit for photovoltaic systems with inverters ( 4 ), which have a plurality of input channels (A +, A-; B +, B-), wherein in the electrical connection region between the photovoltaic modules ( 5 ; 6 ) and the DC input side of the inverter ( 4 ) at least one varistor ( 1 ; 2 ) is connected to earth potential, characterized in that all the lines of the same polarity on a common varistor ( 1 ; 2 ), wherein the line conductors of the same polarity, but different input channels over at least one spark gap ( 7 . 8th ; 9 . 10 ) are decoupled. Surge protection circuit according to claim 1, characterized in that these at least three varistors ( 1 . 2 . 3 ) in Y-circuit, wherein two of the varistors ( 1 ; 2 ) are arranged in parallel and for this parallel connection, the third varistor ( 3 ) lying in series with the ground potential and one of the varistors connected in parallel ( 1 ) over a spark gap ( 7 ; 8th ) with the Pluspolleitungsader and the other of the parallel-connected varistors ( 2 ) over a spark gap ( 9 ; 10 ) is in communication with the negative busbar. Overvoltage protective according to claim 2, characterized in that the Y-connection of varistors ( 1 . 2 . 3 ) as a central protection circuit for all input channels (A +, A-; B +, B-) of a respective inverter ( 4 ) is trained. Overvoltage protection circuit according to one of the preceding claims, characterized in that the spark gaps are designed as gas discharge arresters.

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