Rotronic: Reliable measurements even under extreme conditions
02/12/2015 Rotronic Instruments (UK)
BKW Energie AG trusts in HygroMet4 probes for its ice-load measurements at exposed points.High voltage power lines criss cross Europe in a dense network, transporting electricity both nationally and internationally. Their functional reliability is of utmost importance.
Weather conditions change very quickly in the Alps. These changes can cause rapid ice buildup on the transmission lines. The ability to predict this ice formation allows for preventative steps prior to a power line failure.
One significant factor is the formation of ice at low temperatures and high humidity. When ice forms on the transmission lines the weight can reach ten times normal.
The company BKW Energie AG operates transalpine high voltage lines. The ice load is measured at especially critical points. This is done with strain gauge sensors attached to the masts.
Danger for humans and animals
Although the lines are installed to minimize danger to people, it cannot be ruled out that people will stand underneath a line. Falling chunks of ice can injure or even kill people and animals, and the additional weight can also damage a line.
When ice forms, the lines are disconnected from the grid and heated with a power of about 50 MW to melt the ice. The problem with this is that disconnecting a line generates a financial loss, and the interruption must also be reported in advance to the grid operator - Swissgrid in Switzerland. BKW Energie AG therefore sought a solution by which it could not only estimate the potential for ice formation better, but also minimize grid disruptions and report them at shorter notice. The basis for this is measurement of the humidity of the ambient air.
To achieve this measurement, a meteorological probe from the Rotronic HM4 series was installed on a mast on the Grimsel and one on the Chringe, both with
a weather protection shield. The probe is heated constantly. Heating of the probe prevents condensation on the sensor in mist. The heated sensor is then able to reliably measure humidity even during periods of condensation.
BKW report
The hazard of ice deposits forming on high voltage overhead power lines during winter is a known problem. In critical weather conditions it can happen that the masts are no longer able to bear the rising weight of the wires and therefore collapse.
As early as the 1920s, BKW installed sensors to measure the ice load on the transmission lines. This information, along with local weather data, was communicated several times per day back to BKW for action. Over time, the measurement system was gradually improved as new tools became available.
Reliable and informative measurement data are critical Apart from the tensile forces acting on the wires, weather data at exposed masts is measured and transmitted in real time via the company's optical fiber cables to its control center in Mühleberg. BWK decides, together with Swissgrid, based on current trends and defined limit values for weight, humidity, and temperature when a transmission line is removed from the grid and heated to remove the ice formations.
The reliability and accuracy of the measurement data for tensile force, humidity and temperature are therefore of decisive importance. Working closely with BKW, Rotronic facilitated a comprehensive evaluation of the HM4 meteorological probe and shield.
For more information, please contact:
Rotronic Instruments (UK)
Crompton Fields
Crompton Way
Crawley
West Sussex
RH10 9EE
Tel: +44 1293 571000
Fax: +44 1293 571008
Email: chrisf@rotronic.co.uk
Web: www.rotronic-humidity.com
Print this article
Process and Control Today are not responsible for the content of submitted or externally produced articles and images. Click here to email us about any errors or omissions contained within this article.