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From the category archives: Power Systems

Power systems theory - generation, transmissions and distribution

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How to Size Current Transformers

The correct sizing of current transformers is required to ensure satisfactory operation of measuring instruments and protection relays. Several methods...

IEC 61439 Verification Methods

The (relatively new) switchgear and control gear standard, IEC 61439 'Low-voltage switchgear and controlgear assemblies' has three methods which can be...

Star-Delta Motor Starting - Performance

Many questions sent in to the site are in connection with motor starting and in particular star-delta.  For all but the simplest application, there is...

Power Factor

Power factor is the ratio between the real power (P in kW) and apparent power (S in kVA) drawn by an electrical load. The reactive power (Q in kVAr)...

Random Numbers

Using laser optical pulses the random number generator utilizes the time between arrival of random photos to generate the numbers, ensuring true accuracy...

Battery Sizing

This article gives an introduction to IEEE 485 method for the selection and calculation of battery capacity.

Material Properties

Everything physical in electrical engineering from insulations to conductors revolves around materials. Here we are listing common materials along with...

Lightning Risk Assessment (IEC 62305)

IEC 62305 'Protection against lightning' requires a risk assessment be carried out to determine the characteristics of any lightning protection system...

Bows and Arrows

It starts with me reading one of the Horrible History books with my son (Groovy Greeks). Arrows were mentioned which lead to the discussion of the bodkin...

Cables for MV Power Distribution - Earthed versus Unearthed Systems

Power cables can basically be classified into earthed and unearthed cables, where earthed and unearthed refer to the application for which the cable is...

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