Development of an innovative measurement system for audible noise monitoring of OHL

Austrian Power Grid (APG), the main TSO of Austria, uses different approaches to face challenges arising from stricter requirements regarding environmental issues, where audible noise (AN) is one of the important topics in this context. A innovative approach is pursued with a newly developed measurement system for audible noise monitoring of OHL. The main component of this system is an “optical microphone”. The main benefit compared to a conventional capacitive-microphone, is the lack of any metal and moving parts. Thus, it can operate in the proximity of high electric fields without interferences. This opens up new possibilities for AN measurement on energized OHL. That facilitates the direct measurement of the acoustic immissions and not only the emissions. This is an advantage due to the fact, that measuring AN with conventional microphones has several limitations. The emitted noise from OHL is low compared to other emitters in the surroundings (cars, animals, farming, airplanes) and dependant on wind strength and direction and hence difficult to measure. Furthermore, there is the need for a place on the ground to set up the microphones and the power supply. An agreement with the landowners is mandatory. For the operation of the optical microphone additional components are necessary. A special suspension system was developed to mount the sensor head in the direct vicinity of a conductor. One requirement for the suspension is to keep the sensor head at an exact position underneath the conductor. In a close distance to the conductor, noise emissions vary in a wide range if the relative position is not properly fixed. The second requirement is that the suspension system itself doesn’t influence the measurement. This means, that the electric field strength, which is a main parameter for AN, remains unchanged in the presence of the suspension system. The paper will present the solutions and innovations that have been developed, laboratory tests and installation methods to mount the optical microphone on a conductor.