The case of phase-to-phase fault in a 13.8 kV switchgear caused by heavy rain

In this case study we describe a 13.8 kV switchgear phase-to-phase fault due to by heavy rain evolving into a three-phase fault that was cleared by transformer numerical relays. The…...

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May 17, 2019 | Edvard

The basic protection schemes for 4 typical transformer types in power system

The degree of transformer protection provided depends to a great extent upon the size and functional importance of the unit. A further important factor is the economic aspect. The cost… Read more

May 13, 2019 | Edvard

Three good examples of the application of modern relays to transformer protection

This technical article provides three examples of the application of modern relays to transformer protection. As there are many modern protection relays nowadays that provide advanced software to simplify the… Read more

Apr 22, 2019 | Edvard

7 routine tests for a dry-type transformer you should perform during commissioning

This technical article briefly describes seven very important tests you should perform during commissioning of a dry-type transformer. Usually tests are performed in the factory where transformers are produced. The… Read more

Apr 03, 2019 | Edvard

Transformer no-load loss and excitation-current measurements

A transformer dissipates a constant no-load loss as long as it is energized at constant voltage, 24 h a day, for all conditions of loading. This power loss represents a… Read more

Mar 27, 2019 | Edvard

How not to overspecify high voltage CTs and VTs

The installations wherein CTs and VTs are mounted to measure the normal and abnormal values of current and voltage, have many variations in key system parameters, including voltage class, insulation… Read more

Feb 18, 2019 | Edvard

Connections and working principles of three-phase distribution transformers

A three-phase service can be supplied by one three-phase transformer unit or by interconnecting three single-phase transformer units. One three-phase unit is smaller than an equivalent size bank consisting of…...

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Feb 08, 2019 | Edvard

Protection of a transformer directly connected to a transmission line without switchgear

A transformer-feeder include a transformer directly connected to a transmission line circuit without the intermediation of a HV switchgear. The saving in HV switchgear so achieved is unfortunately lowered by… Read more

Jan 28, 2019 | Edvard

How to determine power transformer impedance for calculation of short-circuit currents

In order to calculate short-circuit currents, it is obligatory to know conductor-specific equivalent data and impedances of electrical operational equipment, which are usually given by the respective manufacturer. The calculation…...

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Jan 25, 2019 | Edvard

6 not-that-easy-to-understand terms related to a power transformer you should understand

There are many terms related to the power transformer operation that can be easily visualized which are especially important for students, like for example transformer construction or regular working principle…. Read more

Jan 21, 2019 | Edvard