From the category archives: Power Systems

Power systems theory - generation, transmissions and distribution

Fault Calculations - Introduction

By Steven McFadyen on 7/1/2012 10:45 AM

Fault calculations are one of the most common types of calculation carried out during the design and analysis of electrical systems. These calculations involve determining the current flowing through... read more..


Low Voltage Fault Tables

By Steven McFadyen on 6/24/2012 7:11 AM

The following tables provide quick order of magnitude fault levels for a a range of typical low voltage situations.

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Cable Sizing Tool

By Steven McFadyen on 5/20/2012 6:14 AM

Our cable sizing tool is one of the more popular tools on the site.  The tool enables cables to be sized in compliance with BS 7671 (the IEE Wiring Regulations) and by implication IEC 60364.

... read more..


Three Phase Power Simplified

By Steven McFadyen on 4/17/2012 2:00 PM

A single phase system is perhaps the most common type of system most people are familiar with. This is what people have in their homes and what appliances are plugged in to. For larger amounts of power,... read more..


Generation of a Sine Wave

By Steven McFadyen on 4/16/2012 1:57 PM

A fundamental concept behind the operation of alternating current systems is that voltage and current waveforms will be sinusoidal – a Sine Wave. This is best explained by considering how a coil of wire... read more..


Low Voltage Circuit Breakers

By Steven McFadyen on 4/15/2012 1:55 PM

Circuit breakers are switching devices whose primary function is to isolate parts of an electrical distribution system in the even of abnormal conditions.  Abnormal conditions are generally caused ... read more..


Battery Sizing

By Steven McFadyen on 4/8/2012 1:34 PM

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

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Variable Frequency Drive

By Steven McFadyen on 3/28/2012 9:58 PM

Variable frequency drives are widely used to control the speed of ac motors.  This note looks at the mechanisms which enable d... read more..


Motor Insulation

By Steven McFadyen on 3/28/2012 1:02 PM

Insulation on a motor prevents interconnection of windings and the winding to earth.  When looking at motors, it is important to understand how the insulation functions and its practical applicatio... read more..


DC Motor Operation

By Steven McFadyen on 3/28/2012 1:00 PM

Coils of wire on the rotor carry a d.c. current which generates a magnetic field. A stator magnetic field is created using either permanent mag... read more..


Restricted Earth Fault Protection

By Steven McFadyen on 3/25/2012 12:49 PM

The windings of many medium and small sized transformers are protected by restricted earth fault (REF) systems. The illustration shows the principal of REF protection. read more..


ANSI (IEEE) Protective Device Numbering

By Steven McFadyen on 3/22/2012 11:40 AM

The widely used United Sates standard ANSI/IEEE C37.2 'Electrical Power System Device Function Numbers, Acronyms, and Contact Designations' deals with protective device function numbering and acronyms. ... read more..




ABB Technical Guides - Motor Operation

ABB has produced a range of technical guides that offer concise explanations of the major technologies and technical issues in low voltage AC drives. ...

IEC Reference Designations

The IEC publishes a series of documents and rules governing the preparation of documents, drawings and the referencing of equipment.   Depending on country...

How D.C. to A.C. Inverters Work

Traditionally generation of electricity has involved rotating machines to produce alternating sinusoidal voltage and current (a.c. systems). With the development...

Meeting room of the future

The IET site has a video of a visit showing of a high tech meeting room developed at Napier University in Edinburgh. It a good demonstration of innovative...

Power Transformers - An Introduction

One of the fundamental requirements of an alternating current distribution systems it to have the ability to change the magnitude of voltages.  It is more...

Tips for a better Low Voltage Protection Discrimination Study

Carrying out a protection system discrimination study is critical to ensure the correct functioning of  the electrical system in the event of faults. ...

What is Aircraft Ground Power

Ever wondered what kind of power an aircraft uses when parked at the airport stand. Normally the aircraft generates it own power, but when parked with...

How Electrical Circuits Work

If you have no idea how electrical circuits work, or what people mean then they talk about volts and amps, hopefully I can shed a bit light.  I’m intending...

How to refer fault levels across a transformer

Over the past year or so I've been involved in on going discussions related to referring fault levels from the secondary of a transformer to the primary...

Occam's Razor

I was reminded of Occam's Razor while reading a book. It's quite a simple principal of logic which has stood the test of time and is accepted as central...

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