Line maintenance under extra high voltage


For the maintenance of extra-high voltage overhead lines, transmission system operators (TSOs) normally have to shut down the line in question. This practice is more than understandable in view of occupational safety. On the other hand, it also reduces transmission capacity and increases the workload of the staff in the TSO’s network control centre who are in charge of coordinating the shutdown. An ideal solution must thus take both into account: first and foremost, the protection of employees and then the best possible utilisation of the facilities.

The Swiss TSO and TSCNET shareholder Swissgrid has carried out a pilot test on the 380kV line Chamoson-Romanel near Lausanne. At the beginning of October, just a few hundred metres from the Romanel substation and in the landing corridor of Lausanne-Blécherette airport, an orange signal ball was installed on the ground wire of the line, which had not been switched off beforehand. Swissgrid drew on the expertise and technology of Airtelis, a subsidiary of the French TSO RTE. Since the 1980s, Airtelis has been working on methods and technologies that allow maintenance work on extra-high voltage lines to be carried out safely and without switching off the power.

An Airtelis/RTE team of around 15 specialists travelled to the western Swiss canton of Vaud. An RTE helicopter also arrived on site, adapted to the work under voltage and equipped with various mirrors and an on-board camera. A special nacelle was attached to the helicopter with insulating anti-rotation ropes. Two Airtelis team members climbed into the nacelle to install the signal ball during the flight. They wore a suit specially designed for work under voltage, which protects its wearer like a Faraday cage. The installation work was carried out exactly as planned and was safely completed after 30 minutes. Swissgrid will now analyse the experience gained from this pilot project, in which the first maintenance work under voltage was carried out in Switzerland, and assess whether this technology should be used generally in future.

Swissgrid has carried out a test on the maintenance of high-voltage overhead lines without disconnecting them from the grid (picture: Swissgrid)

> See Swissgrid blog entry (html)

See article on single page

Aviation history for grid maintenance


The Austrian transmission system operator (TSO) APG, the Austrian IT company SmartDigital, and Austro Control, the Austrian air traffic control authority, jointly carried out the first civilian test flight in which an unmanned drone completed a long-range flight of over 100 kilometres. The maiden flight indicates in which areas of the economy drones can be usefully employed.

However, the TSCNET shareholder did not only carry out the flight to explore the technical possibilities of drone flight, but rather to demonstrate potential applications for monitoring the electricity infrastructure. After all, secure power supply is one of the most important foundations of contemporary society, making it so important that the hardware and software of this infrastructure is fully efficient and intact. To ensure this, it must be regularly monitored. In future, overhead line inspection flights could be performed by unmanned drones, especially in weather conditions where conventional helicopter flights are not possible, e.g. at night or in fog.

After an intensive preparation phase and a comprehensive risk assessment, Austro Control granted permission for this first civilian long-range drone flight without visual contact. The drone surveyed the 380kV line leading from the South-East substation in Vienna to Burgenland, more precisely the section from Vienna to Rotenturm an der Pinka. Gerhard Christiner, CTO of APG, comments: “This pilot project shows how we will be able to inspect lines even better in future, for example in the event of disruptions. This will allow us to find and eliminate malfunctions more quickly. This is an important contribution to security of supply and saves costs.”

Thomas Karall, CFO of APG, adds: “On high and extra-high voltage lines, failures, which we cannot clearly assign, occur time and again. A short-term inspection by means of drone flight would be of great help to us here, because it is often only a matter of verifying whether everything works properly after a short power interruption of a line has occurred.” However, many test flights and legal regulations are still needed before this vision can become reality. In the near future, APG intends to further develop its know-how and use the latest technical possibilities for inspections.

APG has successfully completed the first unmanned drone flight over a 100-kilometre power line (picture: Carolina Burger / APG)

> See APG press release, in German (html)

See article on single page

Grid maintenance by helicopter


These days, the western German power transmission system operator (TSO) Amprion, based in Dortmund, is again starting to control its extra-high voltage overhead lines from a helicopter. By the end of September, approximately 3400 overhead line pylons and about 900 kilometres of overhead lines are to be checked from the helicopter. The actual control is carried out by two employees of the TSCNET shareholder, who fly in each helicopter. However, flying over the lines is always a challenge for pilots, as they must fly up to three meters to the masts and lines at low altitudes and a speed of 20 to 25 kilometres per hour.

Any damage is easier to detect from the air than from the ground. The experts are mainly looking for rope damage, defective insulators, or damage to the mast linkage. However, they also look for trees that grow too close to cables or plastic tarpaulins in the cables, for example. Defects are recorded, evaluated, and later repaired by technicians. Serious defects such as a defective insulator are reported immediately and repaired immediately. Within a few weeks, Amprion thus obtains an overview of the entire extra-high voltage grid.

Over the coming weeks, Amprion will inspect its overhead lines from a helicopter (illustration using a picture of Amprion)

> See Amprion press release, in German (html)

See article on single page

Maintenance by helicopter in Austria


Sometimes it needs an helicopter to inspect and maintain the power transmission grid. As a part of the €29m restauration of the 220kV transmission line through the Liezen district in Styria, TSC member APG, the Austrian transmission system operator (TSO), utilised a “Super Puma”, a modern four-bladed, twin-engine, medium-weight utility helicopter able to lift up to 4.5t. Especially in difficult terrain, helicopters can be used to perform transmission line work more quickly and economically while reducing the environmental impact.

> See APG press release, in German (html)

Picture: Lukas Leitner

See article on single page

Inspection from the air


Transmission system operators (TSOs) have to watch over their power lines to ensure safety and efficiency. TSC member ČEPS, the Czech TSO, has purchased three drones with cameras for inspections throughout the country. The remote-controlled devices make inspections safer, more efficient and much faster. The drones are not only used for routine inspections in hard-to-reach places, but also for emergency situations.

> See ČEPS press release (html)

See article on single page

Repair work in Hungary getting on well


In December 2014, two transmission lines were damaged in Hungary due to extreme weather conditions. Now the restoration process reaches its final phase, announced MAVIR Hungarian Independent Transmission Operator Company in a press release today. The Ócsa–Zugló 220 kV and the Albertirsa–Göd 400 kV transmission are expected to return to operation by June or July 2015.

> Open Mavir press release (pdf, 346 kb)

See article on single page