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.

September 07, 2022

Blog #6 - Residential Electrical Power Chapter one

September 07, 2022/ Graham VanBrunt

Residential Electrical Power Chapter one

This blog covers general information about what you will generally find in North American residential electrical power systems. It is focused mainly on theoretical and observational information. It is not a comprehensive guide to regulations or safety requirements. For any “do it yourself work” you are encouraged to consult with your local utility and safety regulations before starting any work.

Connecting homes to the electrical grid is the final stage of the electrical grid. After the distribution grid's substations have stepped-down the voltage to safe levels, this stage may be accomplished. Wires lead off from the neighbourhood's power lines and connect to individual buildings (homes, apartments, businesses,) by first going through the electric meter to measure how much electricity the home uses. The electricity then passes through a service panel, which houses the electrical safety devices (circuit breakers or fuses). This service panel has all of the wires that run to the different electrical appliances around the house.

Every home is connected to the electrical grid through some sort of fuse box or circuit breaker.

The overhead power connection from the utility lines to the service entrance is referred to as the service drop. It has three wires. One neutral line and two hot lines. The hot lines maintain a certain potential (like 120 V) compared to the neutral line. There are two types of overhead service drops, a mast service drop, or an underground service connection.

The service connection enters the panel via the main disconnect breaker, which is utilized during emergencies to stop electrical power flow. This is positioned in between the service meter and the rest of the electrical panel. The main disconnect is a circuit breakers housed in the electrical panel. In order for this to work the circuit breakers must be in series with the two hot lines of the conductors because it must cut power to all circuits. It is rated to be able to interrupt the total household load.

This diagram to the right, illustrates some of the most common circuits found in a typical circuit breaker service panel box. The breakers are installed in a panel so that contact is made with one or both of the hot bus bars running down the middle of the box. The hot wire for a branch circuit is connected to the breaker by a set screw on the base. The neutral and ground wires for the circuit are connected to a bar along the side of the service panel box. The neutral and grounding bars in the panel may be separate or, in the case of older service panels, the same bar may be used for both purposes.

This wiring diagram illustrates installing a 15 amp circuit breaker for a 120 volt branch circuit. The 14/2 awg cable for this circuit includes 2 conductors and 1 ground wire. A 15 amp circuit is usually used for wall receptacle outlets and room light fixtures.

Since most appliances are designed to operate with 120 V, such as the lighting and outlet recepticles, they are connected to the 120-V lines as in Circuits #1 & #2. Larger appliances requiring 240 V, are connected as in circuit #3.

To avoid trouble, insulation, grounding, fuses, and circuit breakers are used. Modern wiring codes require a third wire for a separate ground.

Because of the dangers of electricity, house wiring is carefully regulated by a code drawn by local ordinances and by the National Electrical Code (NEC).

Electrical outlets provide a means of connecting various devices which require electricity. There are many different types of outlets around the world, with varying voltage and electric current properties. Some are shown here.

As of the 2011 NEC, most new and replacement receptacles must be tamper-proof. This requirement is designed to protect small children from injury by preventing the insertion of objects, other than electrical plugs, into the receptacle contacts. Some exceptions to this requirement include wall receptacles that are more than 62 inches from floor level and large appliance receptacles located out of reach.

New wall receptacles will have two types of contacts: terminal screws on the sides, and holes in the back. The screws may be designed to secure a hooked wire to the device when driven home, or they may be used to tighten a clamp around the end of a straight wire.

The holes in the back of the device are used for inserting a straight wire into an internal clamp. The holes will be labeled to indicate what wire size they can accept.

Receptacles are available for 15 and 20 amp ratings. In older homes, the devices and wiring may be outdated and you will find receptacles that are ungrounded or even ungrounded and non-polarized.

This is a standard 15 and 20 amp, 120 volt wall receptacle outlet wiring diagrams. This is a polarized device. The long slot on the left is the neutral contact and the short slot on the right is the hot contact. A grounded contact at the bottom, center is crescent shaped. The hot screws are usually a brass colour. Neutral screws are usually silver in colour and ground screws are usually green.

The 15 amp, 120 V duplex receptacle outlet can typically be found in livingroom and bedroom wall outlets. One of these may be controlled with a switch and/or wired to other outlets in the circuit. For a 15 amp receptacle like this, 14/2 cable with ground should be used to feed the circuit.

A 20 amp, 120 V duplex receptacle outlet like this should be installed in a circuit using 12 awg cable and a 20 amp circuit breaker. These receptacles are usually found in kitchen wall outlets where two branch circuits are needed to serve small appliances and a refrigerator separately.

When using this device for heavy appliances like washing machines and microwaves, it should be connected to a dedicated 20 amp/120 V circuit breaker. Some electrical codes require circuits to be protected from Arc faults. This can be accomplished with the use of AFI breakers.

An AFI or Arc-Fault Interrupter, is a circuit breaker that breaks the circuit when it detects an electric arc that is a signature of loose connections in home wiring. Loose connections, which can develop over time, and can sometimes become hot enough to ignite house fires.

A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) sometimes simply refered to as a GFI, is an electrical safety device that quickly breaks an electrical circuit with leakage current to ground. It is to protect equipment and reduce the risk of serious harm from an ongoing electric shock.

These electrical wiring devices are designed to quickly and automatically isolate a circuit when it detects that the electric current is unbalanced between the supply and return conductors of a circuit.

They are designed to disconnect the conducting wires ("trip") quickly enough to potentially prevent serious injury to humans, and to prevent damage to electrical devices.

RCDs are testable and resettable devices. A test button safely creates a small leakage condition, and another button resets the conductors after a fault condition has been cleared.

This leakage can be detected either at the receptacle itself (self-contained GFI protection) or back at the power panel with a special breaker that will protect the whole circuit (circuit breaker GFI protection). The above drawing shows how both of these receptacles are connected.

This is the first entry for

Low Voltage Residential Wiring…more to follow