Description

“Change is the only constant” – This fits more than ever for today’s electrical power grids.

Just think about the change in the area of power generation. Years ago nobody would have believed powering down nuclear power plants - Today it is reality in Germany.

At the same time we are facing a tremendous growth in the field of renewable energies. And no run out is expected. Independent studies are still talking about a doubling within the next 10 years.

Concerns it with measurement technology? - “A lot”, is our answering.

The traditional generation with belike only one large-scale power plant will be replaced by a huge number of decentralized low power feed-ins. The hitherto consumers transform to so called prosumers. In key words:

Smaller power plant units => reduction of mass and hence the moment of inertia => new time constants => new frequencies in the network.

The question is, what frequency ranges shall be monitored to ensure a reliable power supply? This range has not received much attention so far. It is below 50 Hz!

These frequencies were of interest for only high voltage level so for since load oscillations and inter area oscillations are known always.

What is the impact on the medium voltage level?

The grid dimensions are much smaller thereby the oscillation frequencies are a little bit higher but - still far below 50Hz - with a good deal worse damping compared to the high voltage level. At this level typical feed-insare wind farms.

The low voltage grid is subject to effects in that frequency range too! Photo voltaic power generation plants squeeze the supply network because of the frequency converter used to feed in. Typical frequencies below 50 Hz are monitored which are inhibiting synchronization of additional offline converters to the system or even desynchronize running converters.

How does the GDASys device family help?
(GDASys = Grid Dynamics Analyzing System)
• Measuring of frequencies below 50 Hz / 60 Hz with a resolution 5 mHz!
• Simultaneous measurement of damping, magnitude and duration of such oscillations
• Recognition of very slow drift processes for both voltage and frequency
• Typical phenomena (e.g. torsion modes) are pre-categorized to frequency classes
• Determination of a single parameter for evaluation of grid perturbations (Stability-exponent) in order to get a fast ONLINE overview
• Frequencies appearing in high voltage networks can be valued if they are of importance for the individual grid

What is the benefit achieved with these measurements?
• Time constants of generators can be determined by means of frequency measurements and can be used for optimization of regulators
• Frequencies with low damping can be detected instantaneous. Thereby a deliberate counter measure – e.g. stability enhancement - can be decided in order to avoid unpredictable grid problems
• The effect of the counter measure can be monitored at once (ONLINE-display)
• Selected grid experiments provide evidence about dynamic grid behaviors. Risky switching operations can be avoided for the future
• Permanent ONLINE-measurements enable the power system management a fast learning process to decide about appropriate and trained real-time counter measures

The software GDAView for visualization is of course clearly laid out and easy to operate.