A grid connection is an electrical tie between a power plant and a transmission grid, a transmission grid and a distribution grid or a distribution grid and a home or business. These grid connections make the distribution and consumption of electricity possible. In order to facilitate a grid connection, components known as busses are typically used. These busses can be very large in connections between transmission and distribution grids, or relatively small in home or business contexts. Grid connections can also be either two or one way, though the type of bidirectional links found in distributed generation contexts typically require extra controls or other safety precautions.
There are many different types of connections that can be found in modern electrical grids. Each electrical grid typically consists of a number of discrete elements, each of which must be interconnected in some way. The portion of the system that is usually connected directly to power generation facilities is referred to as a transmission grid. This part of the grid typically transmits electricity at high voltage and low amperage, and there must be a grid connection between it and at least one power plant in order for the transmission of electricity to take place.
In order to effectively supply electricity to cities and towns, distribution grids are also used. The grid connection between transmission and distribution portions of the system typically involves lowering the voltage to a level that is more suitable for the shorter distances involved. This is usually accomplished at electrical substations that include step-down transformers and other equipment. Power lines in the distribution grid are then connected directly to local homes and businesses.
The final type of grid connection is found at homes and businesses. This type of connection typically involves another step-down transformer that is capable of lowering the distribution voltage to a level that is useful for residential, commercial and industrial applications. These connections are unidirectional in most cases, since homes and businesses tend to consume electricity but do not produce it.
In the case of distributed power generation, bidirectional grid connections at the consumer level can also be possible. This type of grid connection involves a home or business that has solar panels, wind turbines or other electricity generating equipment onsite. In some cases these electrical customers can produce more electricity than they require, in which case a bidirectional grid connection can allow the excess to flow back into the distribution system. These connections often require special permitting to ensure safe operation.