Introduction to wiring diagrams
As already written earlier regarding the LV switchboard, wiring diagrams are used to show the control and signalization principle of operation inside the switchboard. Usually, they are given in form of electrical circuits between two lines which are representing control voltage potentials. Of course, various types of signals can be transferred outside the switchboard, for the purpose of measuring, monitoring, or control, i.e. to be used for SCADA applications.
Within this article, we will be talking about wiring diagrams inside medium voltage (MV) switchgear. Basically, the same rules and principles apply here as well. However, there are some differences related to the fact that in the case of MV applications, primary equipment operates at medium voltage level, while control and signalization circuits are always of low voltage type.
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When we say “medium voltage” or just “MV” switchgear, we refer to a switchgear with “primary” equipment which operates at medium voltage level, typically at or close to 6 kV, 10 kV, 20 kV, and 35 kV in Europe. These are phase to phase, or “line” values of rated operation voltage.