Posted on 1/20/2014 1:32 PM By Steven McFadyen
Modelica is an open source (free) software language for modelling complex systems. Having never used it before, I thought I would download a development platform and see how it stacked up. This is where I spent my Saturday.
Posted on 2/27/2014 12:38 PM By Steven McFadyen
I was digging in my bookshelf and came across the 80th Anniversary Association of Mine Resident Engineers, Papers and Discussions Commemorative Edition (May 2004). Within it's dark covers, is a paper I wrote many years ago. Reading through the paper, brought memories of my arrival in South Africa. It seemed a shame to lose them all again; so this is my first off-topic post in a while.
Posted on 3/2/2014 12:06 PM By Steven McFadyen
Traditionally substations have used circuit breakers, current transformers (CT), voltage transformers (VT) and protection relays all wired together using copper cables. With advances in digital technology, communications and standards, this is now changing to what is known as the digital substation. This is an introduction to the digital substation and the bits and pieces which go into making up the system.
Posted on 4/22/2014 1:19 PM By Steven McFadyen
Traditionally generation of electricity has involved rotating machines to produce alternating sinusoidal voltage and current (a.c. systems). With the development of power electronics during the last several decades, semi-conductor devices are now frequently used to convert direct current (d.c.) to a.c. to power conventional alternating current systems.
Posted on 5/13/2014 1:19 PM By Steven McFadyen
Induction motors are frequently used in both industrial and domestic applications. Within the induction motor, an electrical current in the rotor is induced by a varying magnetic field in the stator winding. The rotor current produces it's own magnetic field, which then interacts with the stator field to produce torque and rotation.
Posted on 6/28/2014 6:00 PM By Steven McFadyen
Exposure to time varying magnetic fields, from power frequencies to the gigahertz range can have harmful consequences. A lot of research has been conducted into identifying these effects and developing recommended safe exposure limits.
Posted on 7/10/2014 3:51 PM By Steven McFadyen
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 merit in performing a more detailed study. Carrying out a software study allows both the electrical performance and that of the connected mechanical systems to be evaluated.
This note illustrates by example one possible approach to studying the performance of a star-delta motor starting circuit.
Posted on 10/13/2014 11:54 AM By Steven McFadyen
In three phase systems, the use of transformers with three windings (or legs) per side is common. These three windings are often connected in delta or star, resulting in common transformer configurations such as delta-delta or delta-star. An open delta transformer is a special arrangement which uses only two windings.
Posted on 11/3/2014 11:48 AM By Steven McFadyen
Carrying out a protection system discrimination study is critical to ensure the correct functioning of the electrical system in the event of faults. The IEC defines discrimination as:
Posted on 12/8/2014 10:25 AM By Steven McFadyen
A load flow study is the analysis of an electrical network carried out by an electrical engineer. The purpose is to understand how power flows around the electrical network. Carrying out a load flow study assists the engineer in designing electrical systems which work correctly, have sufficient power supplied by the power grid, where equipment is correctly sized, reactive power compensation is correctly placed and transformer taps are optimised.
Posted on 1/8/2015 3:55 AM By Steven McFadyen
In an earlier note on the site [Photovoltaic (PV) - Electrical Calculations], the theory of solar (PV) cell calculations was introduced. In particular the post looked at the PV cell equivalent circuit and the electrical characteristics of the cell. This note expands on the previous post and shows how we can use tools like MatLab to model the performance of a complete solar panel.
Posted on 10/21/2016 11:31 AM By Steven McFadyen
When sizing cables nearly, everyone uses some form of software. This ranges from homespun spreadsheets to complex network analyses software. Each has its advantages and disadvantages.