Question

Discuss some of the issues with a high uptake of roof-top solar on the local low voltage grid and how these may 2 be addressed F And similar theory type questions relating to the course work, e g. Ybus matrix, fuse and overcurrent relay characteristics, types of energy storage, etc

Answer 1

The integration of rooftop photovoltaic systems in the low-voltage distribution grids has become a major international trend, helped by the sinking prices for photovoltaics. One of the key questions revolves around the technical challenges brought about by the grid integration of these decentralized systems The reason for so many DSOs is the historically large number of regional grid operators. By contrast, the extra high-voltage grid is operated by only four transmission system operators.

Low-voltage grid structure
The low-voltage distribution system in Germany provides grid access points for households, small businesses and small farms. In addition, distributed power generation systems are connected to this voltage level as well. As described in the following sections, these are mainly photovoltaic systems, but can also include small wind turbines and small biomass plants.

In rural areas, the low-voltage grids are predominantly supplied by a single local distribution transformer. In these areas, the low-voltage grids have a radial structure [b,d,g], in which several power lines are connected to the local distribution transformer without being connected to each other (see Fig. 1). For more densely populated rural areas, the grid may be set up as a ring grid or, alternately, two local distribution transformers can be used to supply a single power line [f,j]. By contrast, the grids in urban areas are more likely to be interconnected (i.e. as a ring grid).

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