FLOW-R Research Project: Development of
the WA-MSR Mesh Current Controller

 

FLOW-R, synonymous with the WA-MSR mesh current controller, was developed jointly by TU-Kaiserslautern, Pfalzwerke, Pfalzwerke Netz, PPC, and Walcher.

The mesh current controller, FLOW-R, has the task of controlling the current flows in meshed low-voltage networks or ring mains in such a way as to balance out strong fluctuations in current flows in parallel mesh lines.

The two Kirchhoff laws are implemented by FLOW-R to form the basis for the controller.

For this, within a mesh, the currents and the phase voltages and angles are cyclically queried at technically relevant measurement points approximately every ten seconds and evaluated in the WA-MSR.

If there is a need for action by the controller, it becomes active and sends suitable dynamic compensating current through the monitored mesh by connecting or disconnecting adapted tap-changing transformers.

The WA-MSR also determines the direction of flow of the compensating current within the ring main; with this, the rated current at all points of the mesh can be influenced.

The WA-MSR can also assume the task of voltage control within certain limits.

The WA-MSR can optionally be monitored from the master display and, if necessary, parameterized via telecontrol protocol IEC 60870-5-104.

Operating Principle

The figure to the left shows the current flow through the mesh without the WA-MSR.

The figure to the right shows the same mesh with installed WA-MSR. It can be seen that the compensating current of 100 A injected by FLOW-R (WA-MSR) counteracts overloading of the right circuit with 220 A at the time. Through this, the current that would theoretically flow without the WA-MSR is reduced from 220 A to 120 A. Because the injected compensating current must flow back to FLOW-R, the relatively poorly loaded parallel branch is better utilized than before. Network conversion can hence be avoided or at least considerably delayed.

The WA-MSR is installed in a cable distribution cabinet for easy mounting on a concrete plinth.

The figure shows the opened FLOW-R with the very maintenance-friendly arrangement of components.

The arrangement of input and output fuses enables rapid switching to a bypass.

Closed WA-MSR (left cabinet) in the local network.

Deployment in test network

Diagram showing test network of Pfalzwerke with measurement points and transformer station as well as the location of the FLOW-R (WA-MSR) marked.

The data are exchanged via power line.

The control principle can be derived more easily in a simplified equivalent circuit diagram.

 

Comparison of representative measurement curves recorded at different times in the same mesh once without and once with FLOW-R. The mode of operation of the WA-MSR can clearly be seen in the curve in Figure 7. The current Ilimit = 40 A shown in blue is well maintained.

As soon as this current wants to rise, it is compensated for by the current injected by FLOW-R
(shown in red). The green curve (tap) given below shows the transformer tap changes at the given times.

 

With the WA-MSR, completely new, low-cost equipment that can avoid the often very expensive network expansion required in many application cases is available.