# Articles

Articles in the field of relay protection and automation, implementation features and modeling of relay protection and automation algorithms.

## Calculation of the Electrical Signal Frequency

Some relay protection and automation functions require information about the frequency of the observed voltage or current. We will consider the option of calculating the frequency of the electric signal from the transition through zero.

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Modern relay protection and automation devices are built on a microprocessor-based elemental base (we denote them as MP device). When discussing the advantages and disadvantages of MP device, they often do this in comparison with electromechanical protection devices (EM device).

## History of relay protection

As far as we know, until the end of the nineteenth century there were neither relayers nor relay protection as such. But electric power and electrical engineering already existed at that time. And short circuits obviously happened periodically. What then protected the electrical equipment from electrical damage?

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## The essence of the Fourier transform

The content of this note reveals the questions of how and why the Fourier transform known to all power engineers works. Here we tried to refrain from using a complex conceptual apparatus, all the calculations used should be clear to anyone who has somehow mastered the initial level of the university course in higher mathematics. For all others, it is possible that the material presented is intuitive.

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## The essence of the method of symmetrical components in three sentences

Physically symmetric components in electrical circuits do not exist. Symmetric components were introduced to significantly simplify the calculation of three-phase circuits due to the fact that the mathematically asymmetric system of three arbitrary vectors can always be replaced by two symmetric systems of vectors and one system of three co-directional vectors (Fig. 1).

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