Single line diagram

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A single line diagram is a form of circuit diagram that is primarily used in the field of electrical power engineering . 3-phase power grids are shown in a simplified manner using a single-line diagram. There is no reference to individual outer conductors in this illustration; the illustration can also be used for asymmetrical three-phase systems. All electrical elements are represented by standardized symbols. This type of representation and its symbols are in DIN standard 40900 part 6, circuit symbols for the generation and conversion of electrical. Energy , normalized.

General

Single line diagram of a coal power plant
Excerpt from a single-line diagram of a substation

Single-line diagrams are used to clearly show electrical systems such as those in power plants or electrical energy distribution networks. An essential application is the load flow calculation . Depending on the requirements and application, voltage or power flow information is also entered in the diagram in addition to the standardized circuit symbols for transformers , load switches , generators or inverters . In the case of power plants, the essential consumers such as pumps are also shown, but further details are missing. Often these values ​​are documented relatively in the so-called per-unit system for further simplification .

The figure on the right shows the single-line diagram of a block of a coal-fired power plant. Each tension level has its own color. The main generator with external excitation is shown on the left, the machine transformer for direct feed into the high-voltage network is shown at the top left . During operation, the power plant is supplied directly from the main generator via the transformer shown in the center, which feeds two redundant 10 kV busbars . The guidance and control technology, various pumps and electrostatic filters are fed from the company's own requirements . Various emergency power supplies are provided to protect against failures . The power plant block shown cannot be black-started and requires the externally supplied 110 kV feed shown in the top right to start up.

The type of abstraction and the restriction of these diagrams to the essentials is comparable to the P&ID diagrams in process engineering.

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