EP3095177A1

EP3095177A1 - Wind turbine radio communication system

Info

Publication number: EP3095177A1
Application number: EP15700169.4A
Authority: EP
Inventors: Per Holgersen; Bjarke Thagaard Ovesen
Original assignee: Semco Maritime AS
Current assignee: Semco Maritime AS
Priority date: 2014-01-14
Filing date: 2015-01-14
Publication date: 2016-11-23
Also published as: DK201600073U1; DE202015009044U1; DK201600073Y3; WO2015106764A1

Abstract

The invention relates to a wind turbine radio communication system. The communication system is a digital two-way radio system, and comprises an outside antenna for being mounted outside of a wind turbine structure. The system further comprises an inside tower antenna for being mounted inside the wind turbine tower, and an inside transition piece (TP) antenna for being mounted inside the wind turbine transition piece. Finally, the system comprises a digital two-way radio system repeater for being in communication with the outside antenna,the inside tower antenna, and the inside TP antenna, the repeater being configured for relaying radio signals received with the outside antenna with the inside tower antenna and/or the inside TP antenna, and vice versa. The invention further relates to a wind turbine comprising the radio communications system.

Description

WIND TURBINE RADIO COMMUNICATION SYSTEM

FIELD OF THE INVENTION The present invention relates to a wind turbine radio communication system. More particularly, the invention relates to a system for providing radio communication coverage within a wind turbine tower and/or transition piece (TP).

BACKGROUND OF THE INVENTION

As wind turbines installed tend to become increasingly large, and to be deployed in even more remote locations and harsh environments, issues of personnel security has an increased focus in the industry. This is especially the case for offshore wind turbines, where even minor accidents may have particularly severe consequences.

One safety problem relating to wind turbines is that radio coverage within the wind turbine tower or transition piece (TP) onto which the tower is mounted, is generally very poor. This is caused by the Faraday's cage effect of the steel towers in common use.

US 2002/0028655 Al discloses a repeater system for wireless communications, particularly for cellular phones. The repeater system includes a repeater coupled to an inside antenna system and to an outside antenna system, wherein the inside antenna system is inside a structure in the form of an edifice or a vessel. The document is silent about use in wind turbine towers and/or transition pieces.

Hence, an improved wind turbine personnel safety system would be

advantageous, and in particular a more efficient and/or reliable radio

communications system would be advantageous.

OBJECT OF THE INVENTION

It is a further object of the present invention to provide an alternative to the prior art. In particular, it may be seen as an object of the present invention to provide a wind turbine radio communication system that solves the above mentioned problems of the prior art with obtaining an adequate radio coverage within a wind turbine tower and/or transition piece.

SUMMARY OF THE INVENTION

Thus, the above-described object and several other objects are intended to be obtained in a first aspect of the invention by providing a wind turbine radio communications system. The communication system is a digital two-way radio system, and comprises an outside antenna for being mounted outside of a wind turbine structure. The system further comprises an inside tower antenna for being mounted inside the wind turbine tower, and an inside transition piece (TP) antenna for being mounted inside a wind turbine transition piece. Finally, the system comprises a digital two-way radio system repeater for being in

communication with the outside antenna, the inside tower antenna, and the inside TP antenna, the repeater being configured for relaying radio signals received with the outside antenna with the inside tower antenna and/or inside TP antenna, and vice versa. In this way, the problem of obtaining radio coverage within the wind turbine tower and/or TP may be alleviated, thereby greatly improving security for e.g. technicians working within the wind turbine. More specifically, the

communication system acts to bi-directionally relay transmission between the inside and outside of the wind turbine, and thereby circumventing the "Faraday Cage"-effect of the tower.

In an embodiment of the inventive communication system, the digital two-way radio system is a terrestrial trunked radio (TETRA) system. In this way, the system may provide "seam-less" radio coverage for personnel entering the wind turbine with a suitable radio terminal. Thus, no manual intervention is required to adjust the radio terminal when moving from outside to inside the tower, or vice versa.

In an embodiment of the wind turbine communication system, the digital two-way radio system repeater comprises a squelch circuit, which is adapted to turn off transmission from the outside antenna except when receiving radio transmission within a monitoring frequency band on the inside tower antenna and/or the inside TP antenna. In this way, the squelch circuit acts to suppress radio transmission from the outside tower antenna when there is no radio activity inside the wind turbine, i.e. when no personnel is present inside the tower and/or the transition piece. In this way, a problem is alleviated wherein otherwise, e.g. a remote base station in radio contact with multiple wind turbine radio communication systems could be overloaded by cumulative noise transmissions from otherwise inactive communication systems. This could e.g. be the case in a wind turbine field where a central base station provides digital two-way radio coverage to the field.

However, when a person enters the wind turbine tower with a radio transceiver emitting within the monitoring frequency band, the repeater automatically receives signals from the radio transceiver on the inside tower antenna or the inside TP antenna and therefore begins to relay the signals to the outside tower antenna. Thus, no action is needed from the person in order to activate the communication system.

In an embodiment, a bandwidth of the monitoring frequency band is in the range of lMHz-50MHz, such as 2MHz-20MHz, or even 3MHz-10MHz. More particularly, the bandwidth of the monitoring frequency band could be about 5MHz.

In an alternative embodiment of the communication system, the digital two-way radio system is a Digital Mobile Radio (DMR) system. In an embodiment of the inventive communication system, the outside antenna is an omni-directional antenna. In this way, a particularly versatile communication system may be achieved in that a communication party located outside the tower may obtain a good radio connection to the communication system, irrespective of a position of that communication party, relative to the wind turbine.

In an alternative embodiment, the outside antenna is a directional antenna. In this way, the directional outside antenna may enable an uplink to a distal radio transceiver with improved signal strength and/or transmission range. In an embodiment of the inventive communication system, the inside tower antenna is a directional, circularly polarized antenna. In this way, an improved transmission range is obtained within the wind turbine tower, i.e. so as to provide radio coverage throughout the height of the tower. For instance, if the inside tower antenna is mounted at the bottom of the tower, use of a directional and circularly polarized antenna enables radio coverage toward the top of the tower. Typically, wind turbine towers are metallic cylinders, which provides for particularly difficult radio communication inside the tower, e.g. due to the tower being a large waveguide for the signals. The present inventors have realized that detrimental back-reflections of radio waves arising from metallic objects and walls within the tower may be reduced by using a circularly polarized antenna.

Compared to an ideal case, wherein the inside tower antenna and an antenna of a user terminal inside the tower have polarizations that are perfectly aligned, a circularly polarized inside tower antenna will give a slightly lower signal quality. However, the inventors have found out that signal quality for non-ideal cases are much improved by using a circularly polarized antenna as the inside tower antenna. Thus, the overall radio coverage or availability when considering both ideal and non-ideal cases are much improved with a circularly polarized antenna. In an embodiment of the inventive communication system, the inside tower antenna is a flat-panel antenna. Thus, a particularly space-efficient inside tower antenna may be achieved.

In an embodiment of the inventive communication system, the inside tower antenna and inside TP antenna are nominally identical. In this way, a particularly cost-efficient and simplified system may be achieved that uses fewer parts. Thus costs related to keeping stock or inventory may be reduced, by allowing interchanging antennas e.g. in case of malfunction or maintenance. In an embodiment of the inventive communication system, the inside TP antenna is a directional, circularly polarized antenna. In this way, an improved

transmission range is obtained within the wind turbine transition piece, i.e. so as to provide radio coverage substantially throughout TP from the foundation to the tower. For instance, if the inside TP antenna is mounted at the top of the TP, use of a directional and circularly polarized antenna enables radio coverage toward the bottom of the TP. Alternatively, the inside TP antenna may be mounted at the bottom of the tower in a vicinity to the top of the TP. Advantages of using a circularly polarized antenna were discussed above when describing the inside tower antenna, but also applies to the inside TP antenna.

In an embodiment of the inventive communication system, the inside TP antenna is a flat-panel antenna. Thus, a particularly space-efficient inside TP antenna may be achieved. In an embodiment of the inventive communication system, the repeater is a trunk-mode-operation/trunk-mode-operation (TMO/TMO) repeater. In this way, the communication system may be seamlessly integrated in existing two-way digital radio systems, such as TETRA. Thus, personnel entering or leaving the wind turbine need not adjust or change settings on their radio terminal.

In an embodiment of the inventive communication system, the repeater is a TETRA repeater, and optionally the outside and/or inside antennas is/are configured for a Rx/Tx- channel spacing of nominally 14.5MHz. By allowing such a nonstandard channel spacing for a TETRA system, operation in certain

jurisdictions with difficulty of obtaining a frequency license using the standard spacing of 10MHz is enabled. For instance, it is difficult to obtain a frequency licence in United Kingdom for a spacing of 10MHz, whereas a licence for a spacing of 14.5MHz surprisingly has been found to be obtainable. In another embodiment, the repeater and optionally the outside and/or inside antennas is/are configured for a Rx/Tx- channel spacing of nominally 10MHz. Thus, the system is adapted for the standard frequency spacing of a TETRA system. In an embodiment of the inventive communication system, the repeater and optionally the outside and/or inside antennas is/are configured for a Rx/Tx- channel spacing of nominally 7MHz.

In an embodiment of the inventive communication system, the repeater is configured for providing a reduced antenna power output on the inside TP antenna, when compared to the antenna power output of the inside tower antenna. Since the volume of TP is generally less than the volume of the tower, sufficient radio coverage in the TP may be achieved using less output power. In this way, power efficiency is improved, and the risk of detrimental reflections of the radio waves is reduced.

In an embodiment of the inventive communication system, the repeater is adapted for transmitting state messages indicating an operational status of the communication system, preferably via a Simple Network Management Protocol (SNMP) module comprised by the repeater. Thus, personnel security is even further improved by monitoring the communication system with regards to operational faults or malfunctions.

In one embodiment of the system, the SNMP module is adapted for transmitting data signals over a local area network (LAN) connection.

In one embodiment the system comprises a digital two-way radio transceiver comprising a monitoring circuit for monitoring an operational status of the digital two-way radio system repeater, the transceiver being configured for transmitting state messages indicating the operational status via the outside tower antenna. In this way, remote status monitoring of the communication system may be achieved also without a LAN connection. Note, however, that this embodiment may also be combined with the use of a SNMP module as described above, so as to transmit state messages in multiple ways.

In one embodiment, transmission of state messages may be triggered by polling from a remote location via the outside antenna.

In one embodiment, transmission of state messages may be triggered internally by the communication system. For instance, the communication system may be configure to transmit such messages at regular time intervals, or at particular times. The invention is particularly, but not exclusively, advantageous for obtaining improved radio communication coverage within wind turbine structures, such as the wind turbine tower and transition piece.

According to a second aspect, the invention is also particularly, but not

exclusively, advantageous for obtaining a wind turbine comprising the wind turbine radio communication system according to the first aspect.

In an embodiment of the wind turbine according to the invention, the wind turbine is an offshore wind turbine.

In an alternative embodiment, the wind turbine is an onshore wind turbine.

In an embodiment of the wind turbine according to the invention, the inside tower antenna is mounted in a bottom part of the wind turbine tower, and oriented to emit in a generally upwards vertical direction.

In an embodiment of the wind turbine according to the invention, the inside TP antenna is mounted in an upper part of the wind turbine transition piece or in a bottom part of the wind turbine tower, and oriented to emit in a generally downwards vertical direction.

The first and second aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The wind turbine radio communication system according to the invention will now be described in more detail with regard to the accompanying figures. The figures show one way of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set. Figure 1 illustrates a wind turbine comprising the wind turbine communication system according to an embodiment of the invention.

Figure 2 schematically shows a communication system according to another embodiment of the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT

Figure la illustrates a wind turbine 1, comprising a wind turbine tower 2, mounted on a transition piece (TP) 3. The wind turbine shown is an off-shore wind turbine, as indicated by the sea surface 4. The wind turbine further comprises a radio communication system 10 as highlighted in Figure lb. In the present

embodiment, the communication system is illustrated to be installed towards the bottom of the wind turbine tower 2, although other locations may also be envisioned. The system 10 comprises an outside antenna 12 mounted in a suitable position outside the wind turbine tower 2. The outside antenna 12 is connected via cable to a digital two-way radio system repeater 14. The repeater 14 is here illustrated to be mounted inside the tower 2, but may in other embodiments be mounted outside the tower, e.g. in proximity to or in connection with the outside antenna 12. The repeater 14 is further connected by cable to an inside tower antenna 16, which is arranged to emit primarily in a vertical upwards direction, as indicated by the zigzag line 18. By configuring the repeater 14 to relay digital radio communication received by the outside antenna to the inside tower antenna, improved radio communication coverage may be achieved within the wind turbine tower. The repeater may comprise a squelch circuit (not illustrated) which acts to turn off radio transmission from the outside antenna 12 when no radio activity is detected by the inside tower antenna.

In a preferred embodiment of the communication system according to the invention, the system operates according to the TETRA standard. As such, the outside antenna 12, inside tower antenna 16, and the repeater 14 are all adapted for the specific radio frequencies used. Furthermore, the repeater is preferably configured as a trunk-mode-operation (TMO)/ Trunk-mode-operation (TMO) repeater, i.e. to seamlessly relay the received TETRA signal from the outside into the tower and vice versa. In certain variations of the present system, the repeater 14 is further equipped with an online monitoring system, e.g. connected via a local area network - and configured for transmitting status and/or performance data from the repeater to a remote location. The online monitoring system is preferably a Simple Network Management Protocol (SNMP) module. The communication system may also have a built-in radio transceiver that has a monitoring circuit for monitoring the operational status of the repeater, and is configures so as to transmit state messages about this operational status of the repeater via the outside tower antenna. Thus, transmission of the state messages may be performed independently from the repeater, and thereby e.g. also if the repeater is un-operational. Transmission of the state messages may in some implementations be triggered from within the communication system, e.g. in response to a change in state, or at given time intervals/specific times.

Alternatively, transmission may be triggered by an external poll signal received by the radio transceiver. For instance, a remote base station may address a specific communication system and poll for a status reply. In this way, the base station may monitor multiple wind turbine communication systems by polling each one in sequence.

In another preferred embodiment of the communication system according to the invention, the system operates according to the Digital Mobile Radio (DMR) standard.

The inventors have found that a particularly good radio coverage within the wind turbine tower may be achieved by using an inside tower antenna which is designed to emit circularly polarized radio waves. This polarization has been found to minimize interfering reflections from the tower structure. Such an antenna may preferably be of a flat-panel type, to minimize space consumption within the wind turbine. The outside antenna 12 is preferably of an omni-directional type so as to enable radio communication with radio operators outside the wind turbine, regardless of their position in relation to the turbine.

Figure 2 shows another embodiment of the communication system according to the invention when mounted in a wind turbine. The embodiment relates to the one shown in Figure lb, for which reason only the differences between the two embodiments are described. In this embodiment, the communication system 10 comprises an inside TP antenna 20 in addition to the inside tower antenna 16. The inside TP antenna 20 is located and oriented to emit primarily in a downwards vertical direction, as indicated by the line 22. Thus, the inside TP antenna 20 provides improved radio communication coverage in the TP - in addition to the coverage in the tower provided by the inside tower antenna 16. In this

embodiment, the repeater 14 is adapted to relay outside communication received on the outside antenna 12 onto both the inside tower antenna 16 and the inside TP antenna 20 simultaneously, so as to provide seamless operation throughout the wind turbine structures of both tower and TP. Since the volume of the TP is generally significantly less than the volume of the tower, the transmission output power on the inside TP antenna 20 is preferably reduced compared to the transmission output power on the inside tower antenna. In one embodiment, the output power on the inside TP antenna is -20dB, compared to the output power of the inside tower antenna. However, it is also envisioned that for other

configurations of wind turbines, output power reductions of -3dB, -5dB, -lOdB, or -15dB would be suitable to reach adequate power while maintaining a low degree of reflections from the TP structure. The inside TP antenna 20 is preferably of the same or similar type as the inside tower antenna 16, such as a circularly polarized flat-panel antenna.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. For instance, even though the system has been described in the context of an off-shore wind turbine, the use in connection with on-shore wind turbines is also envisioned. Furthermore, the system may also be used for wind turbines deployed without a transition piece, without deviation from the scope of the invention. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

Wind turbine radio communication system, the communication system being a digital two-way radio system, the system comprising :

- an outside antenna for being mounted outside of a wind turbine structure,

- an inside tower antenna for being mounted inside the wind turbine tower,

- an inside transition piece (TP) antenna for being mounted inside a wind turbine transition piece, and

- a digital two-way radio system repeater for being in communication with the outside antenna, the inside tower antenna, and the inside TP antenna, the repeater being configured for relaying radio signals received with the outside antenna with the inside tower antenna and/or inside TP antenna, and vice versa.

The communication system according to claim 1, wherein the digital two-way radio system is a terrestrial trunked radio (TETRA) system.

The communication system according to any one of the preceding claims, wherein the digital two-way radio system repeater comprises a squelch circuit, which is adapted to turn off transmission from the outside antenna except when receiving radio transmission within a monitoring frequency band on the inside tower antenna and/or the inside TP antenna.

The communication system according to any one of the preceding claims, wherein the outside antenna is an omni-directional antenna.

The communication system according to any one of the preceding claims, wherein the inside tower antenna and/or inside TP antenna is/are a directional, circularly polarized antenna.

The communication system according to any one of the preceding claims, wherein the inside tower antenna and/or the inside TP antenna is/are a flat- panel antenna.

7. The communication system according to any one of the preceding claims, wherein the repeater is a trunk-mode-operation/trunk-mode-operation

(TMO/TMO) repeater.

8. The communication system according to any one of claims 2-7, wherein the repeater is a TETRA repeater, and optionally the outside and/or inside antennas is/are configured for a Rx/Tx- channel spacing of nominally 14.5MHz.

9. The communication system according to any one of claims 1-7, wherein the repeater and optionally the outside and/or inside antennas is/are configured for a Rx/Tx- channel spacing of nominally 7MHz. 10. The communication system according to any one of the preceding claims,

wherein the repeater is configured for providing a reduced antenna power output on the inside TP antenna, when compared to the antenna power output of the inside tower antenna.

11. The communication system according to any one of the preceding claims,

wherein the repeater is adapted for transmitting state messages indicating an operational status of the communication system, preferably via a Simple Network Management Protocol (SNMP) module comprised by the repeater.

12. The communication system according to any one of the preceding claims,

wherein the system comprises a digital two-way radio transceiver comprising a monitoring circuit for monitoring an operational status of the digital two-way radio system repeater, the transceiver being configured for transmitting state messages indicating the operational status via the outside tower antenna.

13. Wind turbine comprising the wind turbine radio communication system

according to any one of the preceding claims. 14. Wind turbine according to claim 13, wherein the wind turbine is an offshore wind turbine.

15. Wind turbine according to any one of claims 13-14, wherein the inside tower antenna is mounted in a bottom part of the wind turbine tower, and oriented to emit in a generally upwards vertical direction.

16. Wind turbine according to any one of claims 13-14, wherein the inside TP antenna is mounted in an upper part of the wind turbine transition piece or in a bottom part of the wind turbine tower, and oriented to emit in a generally downwards vertical direction.