Electrical systems are mostly built as meshed networks with multiple interconnections between various loads and generation stations. In such a network, the power can be exchanged over different routes, and the cost of power can be considered common to the all loads in the network. However, there are also many hard-to-reach places that are not connected to a power network.
These distant loads include islands and cities in remote areas, or industries in remote locations such as mines. The supply of power to a distant load can be made by a radial transmission from a meshed network or by local generation using diesel generators or gas turbines. Depending on the amount of electricity needed, the distance to the load and other geographical factors, AC or DC transmission can complement or even replace local generation as the power supply for a remote load. The decision to use AC or DC transmission will depend on the specific technical and economic conditions of individual projects.
Usually the remote load must be of a certain magnitude, and the location not too distant in order for the HVDC solution to be competitive. Remote mainland loads are probably rather small. For example, supplying a 100 MW load with a 1,000 km overhead line is feasible for HVDC Light, provided it can compete with local generation.
In the case of sea crossings to islands and peninsulas, AC cables are only feasible for relatively short distances - about 80 km, depending on voltage and power level, due to the cable’s charging currents. This is a classical application for HVDC.