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Hanover, April 20, 2009 – Many transmission network operators are experiencing the problem that previously sufficiently designed transmission lines are turning into potential bottlenecks due to growing energy consumption and the increased supply of wind-generated power. Increasing the line load causes the conductor to heat up, the material expands more and the sag of the conductor increases. The minimum distance between the different phases and between the phases and the ground limits the permissible current of the line. To avoid investment in additional capacities, the existing lines should be utilised in the best way. In this respect CAT-1 from Nexans – a real-time monitoring system for transmission lines – helps. In case of new lines, it also increases the network security and the average annual useful capacity.
Complete data capture and information preparation for dispatchers
Using devices powered by solar energy and back-up batteries, CAT-1 measures the mechanical tension of the conductor, ambient and solar temperature and wind data if required. The sag of the lines – the most important parameter for a safe operation of the transmission lines – is calculated at any time. The measurement units transmit the data via radio communication to a receiving unit, which communicates with the network management centre through the internal network using the existing SCADA protocol. Using CAT-1, the actual additional capacity and the line sag are known by the TSO and it’s possible to operate lines under favourable weather conditions above the static ratings. To ensure safe operation at all times, CAT-1 sends an alarm when defined limits are approached. The operators can react in time to prevent severe damage or blackouts.
Double advantage over traditional network management
Real-time monitoring offers two advantages compared to standard operation procedures: 1) the alarm function is based on measurement values and not to a assumed worst-case scenario. This excludes risks in the operation which can arise as a result of extreme weather conditions – such as on calm, hot summer days. 2) under favourable weather conditions – such as high wind speeds or low ambient temperature – CAT-1 allows the use of additional capacities. Doubling the wind speed from 0.6 m/s to 1.2 m/s increases the real-time rating of a line up to 20%. For 95% of operating time CAT-1 usually offers an additional capacity of 10%; and for 85% of the time the maximum load can be increased by 20% possible.
Tangible relief of burden on the personnel in the network management centre
Despite the enormous mass of data which CAT-1 processes in one transmission network, real-time monitoring eases the management centre personnel’s workload. The staff is not bothered with the incoming measurement data, but only with processed and compressed information. The optimized use of the line capacity also reduces the number of switch operations, and the alarm management simplifies the actions in the event of actual network bottlenecks. The CAT-1 system has proved itself in hundreds of installations worldwide and can be delivered and installed within a few weeks. It works reliably at external temperatures of -40°C to +50°C and is not affected by poor weather conditions such as fog, ice and snow. On the contrary, it creates additional benefits in winter: Measuring the tensile stress also identifies increased sagging due to the weight of ice and minimises risks for the public and the materials.
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| Using devices powered by solar energy and backup batteries, CAT-1 measures the mechanical tension of the conductor, ambient and solar temperature and wind data if required. |
A load cell of CAT-1 |
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