Intelligence for Medium-Voltage Networks

This technology exploits the network's efficiency potential and makes it easier to integrate decentralized generation such as small hydroelectric power plants and solar parks. The core of this solution is the Software that monitors the current state of the network. Based in the surveillance information the network can be automatically adjusted to an optimal level.

With this system electric utilities can supply more consumers with the existing network and have more flexibility in the integration of distributed generation. Until now, extra power could only be fed into the network at points where the grid voltage is not incorrectly affected.

Occasionally this requires long connection cables with high connection costs which are hindering the expansion of renewable energy. Since January, the grid in Lungau in the Austrian state of Salzburg has been regulated automatically.

Within the power system, only the complete high-voltage network is automatically regulated and controlled today. Due to the increasing number of energy sources feeding into the medium and low voltage networks, these elements need to become more intelligent as well. Networks could then react flexibly, like the links in a chain.

A medium-voltage distribution network carries voltage ranging from 1 kilovolt (kV) to around 75 kV. Until now, the data needed to actively maintain the voltage within an allowed voltage range has been lacking. Instead, network voltage is periodically set using calculations based on simulated worst case scenarios. As result the network voltage is kept in the upper part of the voltage range in order to maintain an appropriate safety margin.

The Siemens software uses little measurement data to reliably calculate the steady state of the whole network. Based on this information, optimization software can automatically regulate the voltage and dynamically optimize the grid. For example, to properly adjust the network voltage, the small power plants' generators can be operated to produce or absorb reactive power. The network is reacting flexibly to distributed generation and it can be fully operated at a tolerable lower voltage level.

The automation of middle voltage network is a central step toward creating smart grids. Siemens developed this technology together with Salzburg Netz GmbH as part of the Austrian industrial research project ZUQDE which was funded by the Austrian climate and energy fonds.