DE102010045920B4 - Surge protection for wind turbines - Google Patents

Abstract

Overvoltage protection for wind turbines with - an electrically conductive bridge (4) which forms a current path between two cable ends within the wind turbine and the cable ends electrically conductively connected to each other, - wherein the bridge (4) in the region of the respective cable ends separation points (6) and wherein the separation points (6) connect the respective cable ends to the bridge (4) in an electrically conductive manner, and - an input (14) for receiving a separation signal, - an electrical interruption at and / or after the reception of the separation signal at each separation point (6) is effected, so that the bridge (4) in the region of the respective separation points (6) is electrically separated from the respective cable end.

Description

The subject matter relates to overvoltage protection for wind turbines, in particular lightning protection for wind turbines (wind power plants).

Wind turbines are now an integral part of the energy supply and ensure in the electricity mix for a high proportion of renewable energy. For power generation, "off-shore" as well as "land-based" wind turbines are known. These are now between 100 and 150 m high and have powerful generators in their gondolas. The generators generate high power with voltages in the range of a few kV with very high currents. Cable harnesses carry the electrical energy from the nacelle of the wind turbines to a converter in the base of the tower of the wind turbine. The inverter feeds the electrical energy into the energy supply network of an energy provider in terms of voltage, frequency, and phase. Due to the high voltages and high currents, such converters are very complex and expensive. The converters therefore account for a significant proportion of the total cost of the wind turbine and must be safely protected from damage.

Nowadays, the problem arises that lightning strikes often lead to destruction of the inverter. Known lightning protection measures do not apply, because of the high currents and the high voltages in the power cables arcs that prevent a complete electrical separation even when lightning protection is triggered. It continues to flow a very high current through the arc, which leads to the fact that the inverter can be destroyed.

A ground connection according to the AT 309 578 B has the purpose to dissipate an overvoltage on an electrical conductor, for example due to a lightning strike or a switching operation, into the earth. In error-free operation of this device, however, a derivative of power to earth is not desired. In order to achieve this, arresters are provided, for example varistors, which produce a conductive connection to ground only from a predefinable voltage limit value in order to dissipate an overvoltage. After dissipation of the overvoltage, the varistors block again and the earth line is again electrically disconnected. However, the arrester may have been damaged by an overvoltage, so that even after removal of the overvoltage to earth continues to be an electrical connection to the earth. In other words, the power does not reach the consumer as desired 2 but continues to drain via the ground wire.

According to this prior art, a current path is provided between a consumer and a fuse. Furthermore, a surge arrester is connected. This surge arrester is in turn earthed via an earth shedding device. In other words, the earth-shedding device is connected to the earth on the one hand and to the surge arrester on the other hand. As can be seen from this prior art, the earth-shedding device always has exactly one pyrotechnic element, which is ignited when the arrester is defective. The earth-shedding device is therefore not intended to provide protection against overvoltage, but to provide protection which, in normal operation, prevents the flow of current through a faulty underground cable. The power cord can then be used with a faulty ground line and the broken ground wire can be repaired at a later date.

The WO 2010/066303 A1 relates to a device for reducing a transient overvoltage as a result of switching operations. According to 3 a wind turbine is disclosed, which has two separately controllable switch It is stated that only one of the switches can be controlled.

From the DE 20 2009 018 086 U1 is a separator for separating a single or multi-pole cable known. It is understood that in multi-pole cables each strand must be separated by parallel disconnectors.

The DE 10 2007 033 669 A1 relates to a system for lightning detection. In particular, flash parameters such as the impact point, an induced magnetic field, etc. are detected. A protection circuit is not disclosed.

According to the EP 1 561 947 A2 different current paths are created, which allow a derivation of the caused by a lightning strike at different locations power to earth. However, there are no indications of overvoltage protection.

The WO 2008/049 777 A1 only relates to a Erdableiter, which has a pyrotechnic separation device to avoid a current flow to earth during normal operation as an additional protection device. An overvoltage protection with a bridge is not disclosed.

The safe separation in the event of a lightning strike is not sufficiently reliably solved from the prior art, for this reason, the object of the object underlying an effective surge protection for wind turbines for To provide that prevents the formation of arcs.

This object is achieved by a surge protection for wind turbines according to claim 1.

It has been recognized that arcing at a single point of separation can not be prevented. Therefore, it is proposed to provide the surge protection with two spatially separated separation points, wherein the separation points are electrically connected to each other via a bridge. Thus, objectively between two cable ends an electrically conductive bridge is provided, which connects the cable ends electrically conductive with each other. In particular, cable ends of a supply line, in particular in the region of section boundaries of the tower of the wind turbine, are connected by means of the bridge.

The wind turbine is preferably formed of a tower with at least three sections. The cables in the respective sections are pre-assembled in the tower and only have to be electrically connected to one another during assembly of the sections of the tower. For this purpose, the bridge is preferably designed as a compensation element, which ensures a length compensation between the cable ends. Due to manufacturing tolerances, it may happen that the cable ends at the section boundaries have a different distance from each other. By means of the bridge, it is possible to compensate both the difference in length, and to connect the cable ends electrically conductive with each other.

The bridge is provided in the region of the respective cable ends with a separation point and electrically connected via the separation point with the cable ends. The bridge is provided at its two ends with the separation points.

It is objectively proposed that an input is provided for receiving a disconnection signal and that the disconnection point form an electrical interruption during and / or after the reception of the disconnection signal, so that the bridge is electrically separated from the respective cable ends in the region of the respective disconnection points.

Thus, the subject surge protection provides two spatially separated separation points. At each of the disconnection points, an electrical disconnection is effected in the case of a detected overvoltage. The separation preferably takes place simultaneously, so that the electrical and mechanical separation takes place essentially simultaneously at both separation points. An arc, which forms at a point of separation, collapses, since the current is also separated at the other separation point. The fact that the cable ends are spatially separated from each other and electrically connected to each other only via the bridge, it is ensured that no arc forms directly over the cable ends.

The isolation signal can come from a flash sensor and leads to a separation of the separation point in the event of a lightning strike.

In order to ensure that the separation between the cable ends and the bridge in the region of the separation point is done safely, without affecting the separation points acting forces at the moment of separation negative, it is proposed that the cable ends are fixed to each other and the bridge is a cable is, which is longer than the distance of the cable ends to each other. Thus, the bridge provides a sufficiently high level of flexibility that allows separation of the separation point. A force acting on a first separation point, then no longer acts directly on the second separation point, since the bridge is long enough to absorb the displacement of the separation point caused by the first force.

In particular, the bridge is arranged in a U-shape between the cable ends. It is possible, for example, that the bridge in the region of the U-bottom is fixedly attached to the housing of the wind turbine, here the tower. This prevents the bridge in case of lightning strike being unpaved and falling to the ground. Due to the high altitudes in the wind turbines, this could lead to significant injuries. It is therefore important to avoid dropping the bridge in the tower.

According to an advantageous embodiment, it is proposed that the separating points are each assigned an auxiliary drive. An auxiliary drive can ensure that a separation force acts on the separating points. Therefore, it is proposed that the auxiliary drive on receipt of the separation signal exerts a separation effecting the electrical separation on the separation point.

According to an advantageous embodiment, it is proposed that the auxiliary drive is an activatable by the separation signal, in particular pyrotechnic auxiliary drive. A pyrotechnic auxiliary drive has the advantage that the separation force acting on the separation point is large and a secure separation of the separation point can be effected. In addition, the pyrotechnic auxiliary drive has the advantage that it is very fast and triggers very quickly when receiving the separation signal. The tripping delay is less than 1 s, in particular less than 100 ms, preferably less than 50 ms. This leads to the case of a lightning strike the Inverter is not destroyed because the separation points separate quickly enough.

According to an advantageous embodiment, it is also proposed that upon receipt of the separation signal, the bridge in the region of the respective separation point is mechanically separated from the respective cable end. In addition to an electrical separation, a mechanical separation of the bridge is effected by the cable end. The mechanical separation may mean that the separation point is spatially separated from the cable end. This spatial separation can be done by the force caused by the auxiliary drive. A spatial separation can be that the separation point is shot away from the cable end and thus a sufficiently large distance between the cable end and the separation point is made that an arc collapses. The fact that at both ends of the cable at the same time a separation, the emergence of an arc is prevented.

According to an advantageous embodiment, it is proposed that the cable end and the separation point have a receptacle and a projection corresponding thereto. The cable end can have the receptacle or the projection and the separation point then the corresponding projection or the receptacle. It is irrelevant whether the receptacle or the projection is arranged in the cable end. It is only essential that the separation point then has the respective corresponding part.

The bridge is mechanically and electrically connected to the cable ends via the receptacle and the projection. The receptacle can be, for example, a tapering cylinder and the projection a tapered cone that can be inserted into the receptacle. The cone and the receptacle can be designed so that they are self-locking and are already connected positively together when pushed together. The self-locking can be so large that it is sufficient, the tensile force exerted by the bridge on the connection between recording and projection holds. The tensile force exerted by the bridge may be, for example, the weight of the bridge.

According to an advantageous embodiment, it is proposed that the auxiliary drive for separating the receptacle is formed by the projection. In this case, the auxiliary drive can be arranged for example in the receptacle and ignited, for example, via a firing wire.

A secure separation while preventing mutual interference between the two separation points is achieved for example by the fact that the auxiliary drive exerts a force at an angle to the line between the cable ends on the separation point. In particular, a force normal to the devices between the cable ends causes a secure separation along the separation point.

Another embodiment proposes that the bridge connects cable ends in the region of a section boundary of the tower of the wind turbines. As already explained, the cables are pre-assembled in the wind turbines and already fixed in the respective sections. In order to electrically connect the cables in the individual sections, the bridge can be used. This ensures on the one hand overvoltage protection and on the other hand, the bridge can compensate for differences in length between the cables. This simplifies assembly and at the same time allows overvoltage protection.

According to an advantageous embodiment, it is proposed that a flash sensor generates the separation signal. The lightning sensor can be arranged for example on the nacelle of the wind turbine and transmit the separation signal immediately upon the impact of a lightning to the auxiliary drives. This causes a simultaneous separation of the separation points and prevents destruction of the inverter.

The article will be explained in more detail with reference to drawings showing an exemplary embodiments. In the drawing show:

1 a wind turbine with an overvoltage protection;

2a a detailed view of a separation point in the closed state;

2 B a detailed view of the separation point after 2a in the open state;

3a a detailed view of a separation point in the closed state;

3b a detailed view of a separation point after 3a in the open state;

4 an overvoltage protection device with two disconnecting points and a bridge.

1 shows a wind turbine 2 , A gondola 2a is on a tower 2 B that's made up of sections 8a . 8b and 8c is formed, mounted. Each of the sections can be up to 30 meters high. In a respective section 8a . 8b are cables 10a . 10b . 10c already pre-assembled. The cables 10a -C connect one in the gondola 2a disposed Generator (not shown) with a converter 5 in the base of the tower 2 B , Every section 8a -C of the tower 2 B is thus with cables 10a -C pre-assembled and the cables 10a -C are fixed to the sections 8a -C arranged.

It can be seen that over a section border 9a away the cables 10a . 10b over a bridge 4 electrically conductively connected to each other. This is the bridge 4 each via separation points 6a . 6b with the essentially stationary in the sections 8a . 8b mounted cable ends of the cables 10a . 10b connected.

It can also be seen that a flash sensor 16 formed from an electronics 16a and antennas 16b in the gondola 2a the wind turbine 2 is arranged. From the flash sensor 16a , b can be over a control line 18 a disconnection signal to a receiving circuit 14 be transmitted. The receiving circuit 14 is parallel to the respective separation points 6a . 6b or these associated auxiliary drives 24 connected. The circuit 14 conducts the isolation signal via a control line 14a to the respective auxiliary drives 24 ,

In the case of a lightning strike this is in the flash sensor 16 detected and via the control line 18 to the circuit 14 transmitted. The circuit 14 generates a disconnect signal, which is sent via the control line 14a to the respective separation points 6a . 6b or the associated auxiliary drives 24 transmitted. The auxiliary drives 24 lead to a separation of the separation points 6a . 6b such that the bridge 4 electrically as well as mechanically from the cable ends of the cables 10a . 10b is disconnected. An arc can not occur between the cable ends of the cables 10a . 10b train, still between the bridge 4 and the respective cable end. This ensures that even in the event of a lightning strike the inverter 5 not damaged.

A closed separation point 6a , b is exemplary in 2 shown.

2 shows a separation point 6a , b in the closed state. It can be seen that a cable 10a in the region of its cable end with a receptacle 20 connected is. In this recording 20 can be an auxiliary drive 24 in the form of a pyrotechnic charge, e.g. As a squib, be arranged. The squib can over the control line 14a which is coupled to a firing wire within the firing pellet, can receive a control pulse.

In the recording 20 is a conical bolt 22 Arranged with the bridge 4 connected is. The bolt 22 can self-locking in the recording 20 be arranged. The adhesion between bolts 22 and recording 20 can be such that the bridge 4 captive on the cable 10a is attached and only in case of triggering the auxiliary drive 24 is separated from this.

In the event of a lightning strike, an ignition pulse is sent via the control line 14a to the auxiliary drive 24 passed, leaving the separation point 6a , b separates, as in 2 B is shown. It can be seen that the bolt 22 from the recording 20 is moved, allowing a mechanical as well as electrical separation between the cable 10a and the bridge 4 he follows.

Another concept of a separation point 6a , b is in the 3a and 3b shown. 3a shows the separation point 6a , b in the closed state and 3b the separation point 6a , b in the open state.

In 3a it can be seen that the cable end of the cable 10a with the recording 20 connected is. The recording 20 is formed as a flat part and serves to receive a conical press-in pin 22 that with the bridge 4 connected is. In the recording 20 is the pyrotechnic auxiliary drive 24 provided, via the control line 14a can receive the ignition pulse.

3b shows the separation point 6a , b in the triggered state. It can be seen that by means of the pyrotechnic auxiliary drive 24 the bolt 22 in the direction of X from the recording 20 is moved. The direction X is normal to the propagation direction Y of the cable 10a , The propagation direction Y of the cable 10a runs along a straight line between the cable ends of the cables 10a . 10b , Because of the mechanical separation of the separation point 6a , b at an angle to the propagation direction Y of the cables 10a . 10b If done, it will prevent the forces acting on the bridge 4 act when the auxiliary drives 24 ignited, negatively influence each other.

4 shows a system where the cable ends 10a . 10b lie on a straight line along the Y direction. It can be seen that the bridge 4 U-shaped between the cable ends of the cables 10a . 10b is arranged. The bridge 4 is through a bracket 28 at one of the sections 8a . 8b attached. This can prevent the bridge 4 in the case of separating the separation points 6a , b falls to the ground.

It can also be seen that two separation points 6a , b respectively in the area of the end of a cable 10a . 10b are provided. At every separation point 6a , b is a pyrotechnic auxiliary drive 24a , b provided by the control line 14a can be ignited. The control line 14a is connected in parallel and directly with the control device 14 coupled. In the case of lightning strike is via the control line 14a an ignition pulse in the pyrotechnic auxiliary drives 24a , b coupled, so that they ignite.

Immediately following are the projections 22a . 22b from the recordings 20a . 20b shot, leaving a mechanical as well as an electrical separation of the bridge 4 from the cable ends 10a . 10b he follows. Because of two separation points 6a , b are prevented, is prevented along a separation point 6a , b an arc between the bridge 4 and a respective cable end 10a . 10b forms. The distance A between the separation points 6a , b is chosen so that it is large enough that even over this arc can not form.

By preventing an arc from forming at the moment of disconnection, it is avoided that a lightning strike will destroy the inverter 5 leads.

Claims (10)

Surge protection for wind turbines with - an electrically conductive bridge ( 4 ), which forms a current path between two cable ends within the wind turbine and electrically connects the cable ends with each other, - wherein the bridge ( 4 ) in the area of the respective cable ends 6 ) and wherein the separation points ( 6 ) the respective cable ends with the bridge ( 4 ) electrically conductively connect, and - an input ( 14 ) for receiving a separation signal, - wherein at and / or after receiving the separation signal at each separation point ( 6 ) an electrical interruption is effected so that the bridge ( 4 ) in the region of the respective separation points ( 6 ) is electrically isolated from the respective cable end. Overvoltage protection according to claim 1, characterized in that the cable ends are arranged stationary relative to each other and the bridge ( 4 ) is a cable which is longer than the distance of the cable ends to each other and wherein the bridge ( 4 ) is disposed between the cable ends. Overvoltage protection according to claim 1 or 2, characterized in that the separation points ( 6 ) in each case an auxiliary drive ( 24 ) and the auxiliary drive ( 24 ) upon receipt of the separation signal, a separation force causing the electrical separation on the separation points ( 6 ) exercises. Overvoltage protection according to claim 3, characterized in that the auxiliary drive ( 24 ) an activatable by the separation signal auxiliary drive ( 24 ). Overvoltage protection according to one of Claims 1 to 4, characterized in that, upon receipt of the disconnection signal, the bridge ( 4 ) in the region of the respective separation points ( 6 ) is mechanically separated from the respective cable end. Overvoltage protection according to one of claims 1 to 4, characterized in that the cable end and the separation point ( 6 ) a recording ( 20 ) and a corresponding projection ( 22 ), the bridge ( 4 ) electrically and mechanically with the cable ends over the receptacle ( 20 ) and the lead ( 22 ) connected is. Overvoltage protection according to claim 6, characterized in that the auxiliary drive ( 24 ) to disconnect the recording ( 20 ) from the projection ( 22 ) is formed. Overvoltage protection according to claim 6 or 7, characterized in that the auxiliary drive ( 24 ) a force transverse to the line between the cable ends on the separation point ( 6 ) exercises. Overvoltage protection according to one of claims 1 to 8, characterized in that the bridge ( 4 ) Cable ends in the area of a section boundary ( 9a ) of the wind turbine ( 2 ) connects to each other. Overvoltage protection according to one of claims 1 to 9, characterized in that a lightning sensor ( 16 ) generates the separation signal.

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