ABSTRACT
As discussed in connection with Figure 2.3, electric power supply systems comprise power production plants and lines transmitting power to areas of load (Figure 5.1), where transformers lower the voltage and feed power into a distribution network capable of reaching every single customer (Figure 5.2). Figure 2.4 indicates the options of connecting several such individual power supply systems by extending the transmission lines to enable transmission between the power systems. The cost of establishing such interconnections must be seen as viable in comparison with the benefits derived, such as increased system stability, insurance against the effects of inoperability of production units, and serving peak demands that would be expensive to satisfy with the production capacity available in a given, single system by use of less expensive units available in a neighboring power system, assuming that this is feasible, e.g., as a result of different time variations of loads in the two regions concerned. In cases where one or more of the interconnected systems employ variable energy sources such as wind or solar radiation, the grid exchange between systems can be an economically very attractive way of dealing with intermittency, despite the substantial cost of establishing new long-distance power lines (e.g., across the bodies of water) capable of transmitting in some instances the entire amount of electricity demanded at a given point in time in one region.
