Finding reserves on the electrical grid

May 11, 2011

The weather determines how much energy wind turbine systems provide. The same applies to power line capacity. On cold and stormy days, this capacity is higher than on days with no wind and high mid-summer temperatures. An autonomously powered sensor network monitors power lines to find the reserves in the lines.

When storms lash northern and eastern Germany, it regularly gets tight in the and highest-voltage electrical grids. from has priority on the grid. But, on stormy days in particular, wind turbine systems must be taken offline, because the gird capacities are insufficient. “Currently we are in a situation where we have high inflows from renewable energies into our high voltage line system and are expecting large increases in the future. However, the grid is not designed for this level of energy feed,” reports Hanjo During of envia Verteilnetz GmbH in Halle, Germany, Additional are being planned. But the authorization processes could take years and very often fail due to the resistance of the people living near the projected path of the lines.

For this reason, the grid operators are already utilizing various line-monitoring procedures to increase the grid capacity over the short term: They utilize reserves that are the result of a standardized assumption regarding the worst conditions for operating the line and the actual state of the line. In favorable weather conditions, they were therefore able to increase the transmission capacities by 20 percent or more. Currently, Amprion and envia Verteilnetz are testing a new type of autonomously powered sensor network to monitor 110 kV and 380 kV lines. It is being developed jointly with the Fraunhofer Institutes for Reliability and Microintegration IZM in Berlin and Electronic Nanosystems ENAS in Chemnitz, Germany as well as other research and industrial partners in the “ASTROSE” project. “Our autonomously powered sensor network can be retrofitted easily and does not require additional infrastructure,” says Dr. -Ing. Volker Großer from the IZM. In contrast to the current monitoring systems it supplies measurement data from a tight-knit sensor network directly attached to the conductor wires.

How much current can be transmitted by a power line depends very much on temperature. If the conductor wires heat up as a result of flowing current or the sun, they expand and sag. If the sagging conductor wire gets too close to the ground, buildings, vehicles or humans, there is a risk of electrocution. To rule this out, prescribed safety clearances are mandatory. At the same time, the permitted current flow is calculated under the assumption that the ambient temperature is 35 °C and that the wind’s velocity will not exceed 0.6 m/s. However, high midsummer temperatures often bring with them a lull in the wind. Most wind turbine systems will only start to operate once wind velocity has reached 3 m/s. They deliver high amounts of electricity during fall and in winter when the power lines are effectively cooled by the weather.

To better utilize these reserves in the grid without compromising safety, the ASTROSE project partners equip the 110 kV and 380 kV lines with „eGrains.“ Cylindrical sensor nodes are wrapped around the conductor wire approximately every 500 meters. „They consist of two half cups that are clamped on and attached to each other. The ASTROSE-eGrains measure the cable‘s angle of inclination, the current flow, the temperature as well as wind movement. All measurement values are relayed from eGrain to eGrain to the next transformer station and there they are fed into the central monitoring and control system or rather made available to the internet-based remote maintenance systems of the grid operators,“ explains Großer. The ASTROSE eGrains pull the energy they require from the electrical field that surrounds the conductor wires. However, the ASTROSE does not only help utilize the capacities of the power lines better. It also reports dangerous line sags, such as can occur in winter as a result of ice build-up on the lines. The sensor node can be seen at the "Sensor + Test" tradeshow from June 7 – 9 in Nuremberg, Germany, in Hall 12, Booth 231.

Explore further: Securing America's power grid

Related Stories

Securing America's power grid

June 27, 2006

Terrorists attack Colombia's electrical grid hundreds of times a year. What's to stop attacks on America's power lines? An Iowa State University research team led by Arun Somani, chair and Jerry R. Junkins professor of electrical ...

Intelligent networking of wind farms

April 6, 2010

The EU member states have passed a resolution requiring one fifth of their electricity needs to be derived from renewable energy sources by 2020, with wind farms covering a large part of this requirement. Researchers have ...

Engineers find new way of utilizing solar farms at night

August 17, 2010

( -- New technology from The University of Western Ontario utilizing photovoltaic (PV) solar farms at night will help in connecting more renewable energy sources like wind turbines to Ontario's grid, increasing ...

Saving energy with power grid of the future

November 2, 2010

Green energy too comes out of the electricity socket, but to get there it has to travel a long journey – from wind turbines in the North Sea or regional solar, wind and biogas power plants. On the way to the consumer ...

A world record in direct current transmission

May 3, 2011

Siemens is building power converter stations for a high-voltage direct current (HVDC) transmission system with a record capacity of 2 x 1,000 megawatts. Beginning in 2013 the new HVDC PLUS technology will transmit 2,000 megawatts ...

Recommended for you

The ethics of robot love

November 25, 2015

There was to have been a conference in Malaysia last week called Love and Sex with Robots but it was cancelled. Malaysian police branded it "illegal" and "ridiculous". "There is nothing scientific about sex with robots," ...

No lens? No problem for FlatCam

November 23, 2015

How thin can a camera be? Very, say Rice University researchers who have developed patented prototypes of their technological breakthrough.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.