Electro-Magnetic Interference Assessment for Naroghid Wind Farm Report Number WFD/AU/04/17

Author: Jerome Rowcroft

Reviewer: Wendy Wilson

Authorised: Alistair Wilson

Date: 9th June 2017

Status: Approved for Submission

Revision Comment

Version 1 Map of Transmission and receivers, and P2P links. Includes correspondence with Optus and Telstra confirming no impact on their communication links.

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Contents 1. Introduction .................................................................................................................................... 2

2. Wind Farms and EMI ....................................................................................................................... 3

3. Naroghid Wind Farm and Signal Transmitters ................................................................................ 3

3.1 AM Radio ....................................................................................................................................... 4

3.2 FM Radio ....................................................................................................................................... 4

3.3 Digital Television and Radio .......................................................................................................... 4

3.4 Point to Point Communications .................................................................................................... 4

3.5 VHF and UHF Signals ..................................................................................................................... 5

3.6 Mobile Phone Networks: 3G and 4G Networks ............................................................................ 5

3.7 Weather Radar .............................................................................................................................. 5

3.8 Aviation Navigation ....................................................................................................................... 6

4. Conclusion ....................................................................................................................................... 6

APPENDIX A: Correspondence with Telstra ............................................................................................ 7

APPENDIX B: Correspondence with Optus.............................................................................................. 8

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1. Introduction The Naroghid project site is approximately 175 km West-South-West of Melbourne, 40 km inland

from the coast. It is located in the Shire of Corangamite about 7 km southeast of Camperdown and

10 km South-East of Terang. The location of the site is depicted on the map in Figure 1.

The project area consists of cleared agricultural land used for intensive dairy farming. A tree nursery

borders the northern boundary of the project site. The terrain is flat to slightly hilly with an elevation

between 190 m and 220 m. A photo of the land is shown in Figure 2.

This report addresses the communication links that exist on and pass over the site. Based on this

report, the layouts that have been developed do not impact on communication links.

Figure 1: Location of Naroghid Wind Farm

Figure 2: Photo of Naroghid Wind Farm site.

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2. Wind Farms and EMI Wind turbines have the potential to cause Electro-Magnetic Interference (EMI) – based on their own

Electro-Magnetic (EM) emissions, and more significantly, as an obstacle for EM signals. Wind turbine

and wind farms more generally, do emit EM signals, however, their region of influence is confined to

a small radius (in the tens of metres) around the turbines and infrastructure.

Of tangible concern is the wind turbine’s potential to obstruct, diffract, reflect, or scatter EM signals.

In this report, the following EM signals are considered in the context of the Naroghid Wind Farm:

AM radio signals

FM radio signals

Digital television signals (noting that the analogue television signal was fully

decommissioned in Australia by April 2014)

Satellite television and internet

Point to point communication (microwave)

VHF and UHF signals

Cellular telephony: 3G and 4G mobile phone networks

Weather radar

Aviation navigation facilities

3. Naroghid Wind Farm and Signal Transmitters AM, FM, Digital TV, Digital Radio, and the Melbourne Weather Radar are shown in the map in Figure

3. It can be seen from this map that Naroghid Wind Farm is well set back from these transmitters.

Figure 3: Map of EM transmitters around Naroghid Wind Farm. Data obtained from the ACMA website in August 2016.

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3.1 AM Radio Amplitude Modulation signals are long wave signals. Operating wind turbines can influence the

radiating patterns, with the potential to result in reduced signal quality and strength, as well as

causing interference at neighbouring frequencies. A 2 km radius consultation zone exists around AM

transmitters. The field of influence from the receiver’s perspective is in the order of tens of metres.

As can be seen in Figure 3, the nearest AM transmitter is located near Warrnambool, over 30 km

away, well beyond the 2 km radius consultation. With the exception of the immediate vicinity of a

wind turbine, Naroghid Wind Farm will have no effect on AM radio.

3.2 FM Radio Frequency modulated signals tend to be more robust around obstructions such as buildings and

wind farms. At the edge of their transmission range, where the signal to noise ratio is already quite

low, wind turbines can have an adverse influence on the signal. A 1 km radius consultation zone

exists around FM radio transmitters. The Naroghid Wind Farm site falls well beyond this zone.

3.3 Digital Television and Radio With analogue television transmission decommissioned throughout Australia in April 2014, only

digital television (DTV) transmission needs to be considered. There are also a number of digital radio

transmitters across Victoria, which have similar requirements to the DTV transmission.

Wind turbines can cause shielding and disruption of the transmitted signal. A 2 km radius

exclusion/consultation zone is in place around transmitters, but, as can be seen in Figure 3, the

nearest DTV transmitter is over 7 km from the site, while there are no digital radio transmitters in

the area.

DTV signals are resilient to multipath propagation, which, with an analogue signal, results in

ghosting. DTV signals are, however, susceptible to frequency variation from passing rotor blades,

with impacts varying as a function of turbine orientation and rotational speed, or wind direction and

wind speed. The rotor pass causes a signal frequency variation, resulting in an increase in the bit

error rate.

As a starting point, DTV signal degradation issues are often resolved by refocussing the receiver on

the existing transmitter, or realigning the receiver towards an alternative transmitter. In the case of

the Naroghid Wind Farm, there are a number of DTV transmitters that surround the site – to the

north-west (13 km), east (9 km) and south (23 km).

3.4 Point to Point Communications To avoid impacting on point to point communications, the wind turbine rotor must not cut the

Fresnel Zone of a point to point link. A map showing point to point links and various communication

nodes is presented in Figure 4. The communication nodes typically represent telecommunication

customers. This map demonstrates that no link passes within 1 km of wind turbine. The maximum

radius of the first Fresnel Zone of the nearest link is 8.64 m.

Based on the links identified, Naroghid Wind Farm will have no impact on any point to point

microwave links.

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Figure 4: Point to point links passing across and near the Inverleigh Wind Farm site.

3.5 VHF and UHF Signals VHF and UHF signals are used for regional communications between fixed and mobile stations,

offering robust, low bandwidth links. They typically operate at low power and have broad

beamwidth, rarely less than 40°. As such, line of sight is not required between stations, and signal

attenuation is much lower than high energy, microwave links. For example, through a forest section,

attenuation of 0.4 dB/m is expected with a microwave link, whereas, with a VHF signal, the

attenuation is 0.05 dB/m. 1

As such, wind farms are not anticipated to have an impact on VHF and UHF signals.

3.6 Mobile Phone Networks: 3G and 4G Networks There are no mobile phone towers within 1 km of the site, as such the wind farm will not impact the

mobile phone 3G and 4G networks.

3.7 Weather Radar Victoria has four weather radars, according to the Bureau of Meteorology. The nearest is located

over 150 km to the east of the site, and is shown in Figure 3. At an elevation angle of 1°, the radar

echoes pass at over 2600 m above mean sea level. The highest elevation at the site is nominally

220 m above mean sea level; with the addition of wind turbines, the maximum height of the

1 Electromagnetic Interference Analysis for Mortlake South Wind Farm. Doc ID:

IPTINTAUSVICXXMOR.3

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development may reach 420 m above mean sea level, which is a considerable margin below the

radar echoes.

3.8 Aviation Navigation Correspondence with Air Services Australia has indicated that there will not be any issues with

instrument approaches for the airfields that come under their jurisdiction.

4. Conclusion The Electro-Magnetic Interference associated with Naroghid Wind Farm has been assessed. In

particular, no point-to-point microwave links pass over the site – the nearest link is 1 km from the

nearest proposed wind turbine.

Correspondence with telecommunications providers has confirmed that their services will not be

impacted, based on preliminary layouts provided. While some influence on radio signal reception is

expected, this is anticipated to extend only to the order of tens of metres from turbines. FM signals

will be largely unaffected, unless signal to noise ratios are already very low. Digital television signals

may be affected, however, this is mitigated by directing the receiver at an alternative signal source –

which have been demonstrated to exist in the area. The wind farm will have no significant impact on

weather radars and aviation communications.

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APPENDIX A: Correspondence with Telstra

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APPENDIX B: Correspondence with Optus