The power networks of European countries are closely linked; together, they form a transmission system for electric power covering thousands of kilometers. This is for the benefit of supply security, as regional excess may be exported to those regions showing an increased demand.
However, local malfunctions may also spread across this huge network and entail negative effects in other areas, all the way to the feared blackout, potentially costing hundreds of millions of Dollars as well as endangering life and limb in our electrified society.
Moreover, in times of low electricity prices with constant cost pressure as well as the very lengthy approval procedures for new high-voltage lines, the networks are operated ever more closely to their utilization and stability limits.
«Voltage and frequency must be kept within the stability limits in the entire supply network, otherwise there is a risk of chain reactions with far-reaching consequences», emphasizes Petr Korba, Professor for Electric Power Systems and Smart Grids at ZHAW in Winterthur.
Korba himself has done a lot of groundwork when it comes to network stabilization. In his time as Principal Scientist at the ABB Research Center in Baden-Dättwil, he has made decisive contributions to the development of the «Wide Area Monitoring and Control» system (WAMC) and particularly to the detection of unstable situations as well as the algorithms required for monitoring the network stability. The corresponding solution is offered in ABB’s portfolio today, e.g. as «PSGuard».
The required data are collected via the phasor measurement units (PMUs), widely dispersed across the power system network. «These PMUs provide the most precise synchronized measurements of electric currents and voltages in our alternating current system, which are timed with an accuracy of less than one microsecond by GPS signal. Suitable algorithms will provide an overview on the system stability in the dynamic network in real time, allowing us to intervene on a regulatory basis in case of critical deviations», says Korba.
At the lab for electrical engineering at the Zurich University of Applied Sciences (ZHAW) in Winterthur, Korba has now recreated, together with his team, an entire power supply system at a scale of 1:1000 in terms of voltage – with power generation, transmission, distribution, storage, protection and consumers. With it, the basic principles of electric power transmission and stability limits of the network can be made more tangible to students by means of an industrial wide-area monitoring system under real conditions. «This is not a virtual simulation on the computer but a physical emulation. A real electric power system with all key components, only scaled down, to experiment with», emphasizes Korba. For many trials, it were the first facility of this kind.
ABB has contributed PMUs of the latest generation – RES670 – as well as the software PSGuard; in addition also excitation systems for synchronous generators of the type UNITROL 1000. «This is how we intend to close the control loop and develop a wide-area control system. ABB’s support is a valuable contribution to our lab», emphasizes Korba. More than 50 students have already registered for the first course in the autumn semester. «This level of interest already goes to show how important the topic of network stability is and how much sense the development of this lab makes.»