1. The basic representation of the system

1. The basic representation of the system

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Imagine a tandem bicycle moving at constant speed.

The goal of this whole system is to keep the figures in blue at the back of the bike moving, even though they are not generating any of the energy that keeps the bike in motion. They represent the load. There are large loads that consume a lot of electricity, industrial plants for instance, and smaller loads, like private dwellings.

The pedalling figures in red deliver the energy that keeps the system going. They are the power stations where electrical energy is generated. Some power stations are larger and stronger than others and thus supply more power.

The chain connecting all elements of the system is the equivalent of the electrical transmission network. That is the network of high voltage lines used to transport the electrical energy around the country. The chain must turn the wheels at a constant rate to maintain the same velocity. Likewise, the electrical network needs to have a fixed and constant frequency. The upper part of the chain should be under a constant physical tension, just as the connection in the electrical transmission network should have a fixed voltage level. The lower part of the chain is without tension and is the equivalent of the neutral wire in a transmission network.

The pedalling movement (energy) of the red figures is transmitted to the chain by a gear or a gear system. This gear is like the transformer between the turning movement of the turbine in a power station and the electrical high voltage network.

Some of the red figures (= power stations) don’t pedal at full power. They conserve some of their energy to be able to apply some extra force when needed to hold the same velocity. For example when another blue figure suddenly jumps onto the bike (= another load connects to the network), or one of the red figures gets a cramp and has to stop pedalling (= a power station experiences technical problems and has to shut down), replacement force is needed to maintain the same velocity.

The tandem bicycle analogy can also be applied to many specific characteristics of the Electrical Power System and its Power Quality as well.