Whether you are new to the industry or are well seasoned and want to review some of the basic information that you learned in the past, these courses and lessons will clearly outline what you are looking for. “Power Systems Electric” is On-Line training that bridges the gaps between textbook theories and practical power systems experience. As a retired electrical engineer who has gone through the experience of developing a career in electrical power systems, I know how frustrating it can be to try and find the answers, so I put together these courses that I feel would have been a major help to me in my development. I have also taken suggestions from students of what they would like to see in addition to these courses which I have given live in person.

Basic Electrical Learning

For those new to the industry, there is a beginner’s group of courses that cover the “Fundamentals of Electricity ” including DC and AC Circuit Analysis. These lessons examine such basics as Ohm’s Law, Series, and Parallel Circuits. The first, and perhaps most important, relationship between current, voltage, and impedance, “Ohm’s Law”, and its relevance to Series and Parallel Circuits. Subsequently, this will lead to the development of Kirchhoff’s Laws as they help to further analyze Network Analysis & Metering Circuits.

Conductors and Insulators are investigated along with their connected components, Capacitors, Inductors, and how they are influenced by Electromagnetism.

Alternating Current (AC – an electric current that periodically reverses direction) is the form in which electric power is delivered to businesses and residences, and it is the form of electrical energy that consumers typically use when they plug kitchen appliances, televisions, fans, and electric lamps into a wall socket.

The abbreviations AC and DC are often used to mean simply alternating and direct, as they are applied to current or voltage.

These AC courses deal specifically with sinusoidal waveforms and will provide the student with the basic understanding of working with circuits involving Alternating Current, which includes sinusoidal waveforms, vectors & phasors, reactance & impedance of R,L,C circuits, as they relate to the basic laws and theorems of electricity. This includes working with AC Power, Power Factor, Resonance, Complex Numbers, Reactance, and Impedance

Advanced Electrical Learning

These Courses involve subjects such as “Short Circuit Analysis for HV Three-Phase Systems ” which introduces the student to the basic concepts of fault studies on a high voltage three-phase system. System modeling is then used in order to aid in this process, with the ability to move between asymmetrical and symmetrical systems. With hey Searle and extensive study of “Per Phase” & “Per Unit” methodologies system faults are analyzed with the use of symmetrical components.

“A Per-Unit System ” is the expression of system quantities as fractions of a defined base unit quantity. Calculations are simplified because quantities expressed as per unit do not change when they are referred from one side of a transformer to the other.

In these courses, you will learn exactly what Per Unit Analysis is, the main advantages of using it, how manufacturers of equipment use and rate their products, and the technique of converting to and from the Per Unit system.

Several examples of working with Per Unit are demonstrated in this crisp clear presentation. When you finish you will have a though understanding of this subject.

It is important for all power engineers and technicians to be familiar with the concept of Per Unit as it is being used and referred to every day in power flow, short circuit evaluation, and motor starting studies.

The method of “Symmetrical Components ” is used to simplify asymmetrical three-phase voltages and current analysis by converting the unbalanced system into two sets of balanced phasors and a set of single-phase phasors, or symmetrical components. These sets of phasors are called the positive, negative, and zero sequence components.

An understanding of this method is essential for the understanding of fault analysis and modern-day protection schemes. These courses will provide you with the knowledge to comprehend the concept and how it is applied.

Supplemental Electrical Lessons

In all power electrical analyses, the student will encounter special Trigonometric and Mathematical identities and equations. This site contains special supplemental lessons that zero in on those identities and equations. For example, there are lessons that take you from the “Fundamentals of Trigonometry ” to the more sophisticated requirements in electrical engineering. As you work and study in electrical engineering you are going to run into proofs and equations that are based on trigonometry. A good example of this is when studying AC current, voltage, and impedance calculations, phasors or vectors are used and combined mathematically. Further adventures into complex power will also require a knowledge of trig functions and identities. As a student of this course, you will be introduced to these or at least re-introduced to these that may have been long since forgotten.
In mathematics, “The Derivative of a Function ” of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. For example, the derivative of the position of a moving object with respect to time is the object’s velocity: this measures how quickly the position of the object changes when time advances.

Specialized Electrical Lessons

Specialized lessons include the “Protection & Control(P & C)” principles of high voltage stations. HV Bus Differential Protection is studied along with restrictions due to CT saturation & mismatch and its solution, “Restraint Differential Protection”.

High Voltage Circuit Breakers are examined as to the various Types (Oil, Vacuum, Air Blast, SF6), their Controls as well as the introduction of potential transformers & current transformers, and their use in conjunction with the relevant instruments such as ammeters, voltmeters, watt meters, and energy meters.

Other lessons include the study of “Transformers ” including core construction along with losses, cooling, and mitigation techniques. Three-phase transformer configurations are studied along with harmonic distortion, CT saturation, and on-load tap-changer problems and how these problems are dealt with. Over-current and restraint differential transformer protection is developed along with a look at some examples of ” Old School relays” as well as modern IDE (intelligent Electrical Devices) relays.

Transformer Connections: (Y – Y; Delta – Delta; Y – Delta; Delta – Y & Y – Zag Zig) are examined along with Transformer Clock System Vector Nomenclature.

Lastly, there is a special section dedicated to “Single and Three-Phase Metering “, including old analog and new digital kilowatt-hour meters.

Conclusion

Regardless of whether or not you are new to the industrial power system, you’ll find what you’re looking for on this site in the way of training. In order to review or select any of these courses, left-click on any of the blue highlighted hyperlinked words of this posting or on “14 Courses Available” from the top menu of the landing page. All of the courses have a free introduction

As a bonus and in the way of a thank you, for your interest in PSPT’s WEB (and Blog) page, I’m making available my 50-page “Electrical Power” crib sheets. These were prepared for use with my courses that are available on this site. There is one section associated with each course and is extremely valuable while viewing the course, as well as a recall of the pertinent formulas and information after the fact. The contained information is also useful during any technical career as a quick reference from time to time. Simply click here or on the picture to the right to be taken to where you can download this item.

August 28, 2022

Blog #5 - Electrical Grounding

August 28, 2022/ Graham VanBrunt

The Evolution of Electrical Grounding

Grounding is a principle of electricity that sometimes puzzles homeowners. To understand its importance to a home wiring system, it is important to know something about the nature of electrical energy flow.

What Is Electrical Grounding?

Grounding offers excess electricity the most effective and safest route from an appliance back to the ground by way of an electrical panel. Electrical grounding is a backup pathway, that is generally only used if there is a fault in the wiring system.

Electrical service to North American homes began in the late 1890’s, and blossomed from 1920 to 1935, by which time, 70 percent of homes were connected to the electrical utility grid.

In the following 200 years, the methods for installing wiring in those homes has seen several important innovations, aimed at improving the safety of electrical systems.

Between eighteen 90 and 1910, a wiring system known as knob-and-tube, was the principal system of installation. It was quite a dependable system for the time, and a surprising number of homes still have knob-and-tube wiring functioning, where it is often found alongside more modern updates. In knob-and-tube wiring, individually conducting wires protected by a rubberized cloth fabric, are installed in stud and joist cavities, held in place by porcelain knob insulators, attached to the sides of framing members, and protected by porcelain tube insulators where the wires run through, the framing members.

In this wiring system, hot wires, and neutral wires, were run separately for safety. The system also allowed long circuit runs to be constructed by splicing together lengths of wire. To do this, the insulation was stripped back, a new wire was wrapped around the exposed bare wire, and the splice was soldered together then taped to cover the splice.

The downfall was the wire was exposed and there was no ground wire used. Where knob-and-tube wiring is still functioning, it is living on borrowed time, since the rubberized cloth insulation used on the wires has an expected lifespan of about 25 years, before it begins to crack and break down.

Electrical systems containing functioning knob-and-tube wiring are in critical need of an upgrade. But just because you see knob-and-tubes in some wall or floor cavities, doesn't necessarily mean you are in danger.

It was common practice to simply leave old wiring in place, but not energized, and functionally replaced when a home was rewired.

It's possible that the porcelain insulators and wires you see are merely antique remnants of earlier wiring installation.

In the 1920s to 1940s, electrical installations took a turn to a more protective wiring scheme, flexible armored cable or Flex, also known as Greenfield, was a welcomed addition to home wiring because the flexible metal jacket helped to protect the wires from damage, and also offered a metal pathway that could ground the system, when properly installed.

Although it was an improvement, this wiring method had its troubles. Although the individual wire conductors are protected, the flexible outer metal jacket serves as a proper ground only when the metal pathway is complete, all the way to the service entrance and grounding rod. There is still no separate ground wire in these installations.

Nonmetallic Sheathed Cable

In the 1930s, a quicker installation method was developed. Nonmetallic-sheathed cable was born, which incorporated a rubberized fabric coating sheath, much like knob and tube wiring, but here the hot and neutral wire were run together in this one sheathing. It also had its drawbacks due to the lack of a ground wire, but its development would eventually lead to major innovations.

Early sheathed cable, however, also has an expected lifespan of about 25 years, and where it is still in use, such installations need to be upgraded.

The Age of Metal Conduit

The newest addition to wiring was NMD, introduced in around 1965. This form of NMD cable was an update to older NM cable and incorporated the use of a bare copper grounding wire along with the insulated hot and neutral wires, contained within the sheathing. Instead of rubberized sheathing, modern NMD cable uses a very tough and durable vinyl sheathing. This update made the cable inexpensive and very easy to install. It is a very flexible product and is used extensively in virtually every new home built.

Along with NMD cable for interior use, a related type of cable was also developed for underground use. Underground feeder wire, (UF), can be buried directly under the ground without the need for a protecting conduit. This type of wire has a hot, a neutral, and a ground wire embedded in a solid plastic vinyl sheath that protects it from moisture. This offers an inexpensive method for running power underground to outbuildings and yard lights.

Through most of the history of residential electrical service, the preferred metal used in the conducting wires has been copper, known as the best conductor of electrical current. In the mid nineteen 60’s, when copper prices were quite high, aluminum came into vogue, as a material for electrical wiring. Residential installations between 1965 and 1974, sometimes used wires that were solid aluminum, or aluminum covered with a thin layer of copper.

Aluminum or copper-coated aluminum wiring is perfectly safe, if connected to receptacles, switches, and other devices, rated for use with aluminum, but it can pose problems, when it's installed with devices intended for use with copper wiring only.

Because of these issues, aluminum or copper-clad aluminum is no longer used in residential applications. It is for this reason, if you have aluminum wiring, repairs are best made by a professional.

To prevent electrical danger, your home's electrical system includes a backup plan, a system of grounding wires that runs parallel to the hot and neutral wires. It provides an alternate pathway for electrical current to follow should there be a breakdown in the system of hot and neutral wires, that normally carry the current. If a wire connection becomes loose, for example, or a rodent gnaws through a wire, the grounding system channels the stray current back to ground by this alternate pathway, tripping the breaker, before it can cause a fire or shock.

The grounding pathway is generally formed by a system of bare copper wires, that connect to every device, and every metal electrical box in your home.

In standard sheathed NM cable, this bare copper wire is included along with the insulated conducting wires inside the cable. The bare copper grounding wires terminate, in a grounding bar in your main service panel, and that grounding bar is in turn connected to a grounding rod driven deep into the earth outside your home.

This grounding system provides a path of least resistance for electricity to follow back to ground, should a break in the wiring system allow electricity to "leak" out of the preferred system of black and white circuit wires.

In most home wiring systems, evidence of the grounding system can be seen at each outlet receptacle, where the third round slot in the face of the receptacle represents the grounding connection. When a grounded appliance plugs into such a receptacle, its round grounding prong is now directly connected to the system of bare copper grounding wires inside the house circuits.

Not all homes have this elaborate and complete grounding system formed by a network of bare copper wires. While such a grounding system is standard in homes with circuit breakers that are wired with sheathed NM cable, older wiring systems installed before 1965 may be grounded through metal conduit or metal cable, not bare copper grounding wires. And even older systems installed before 1940 may not have any form of grounding at all. Such is the case in knob-and-tube wiring, where there is no grounding path of any kind. Many older systems have already been updated, and it is a good idea to have it done if your wiring is of this older generation. One clue that your wiring is old is when the outlet receptacles have two slots rather than three. This indicates the outlets may not be grounded.