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.

November 13, 2022

Blog #14 - The House Main Electrical Panel

November 13, 2022/ Graham VanBrunt

Connecting homes to the electrical grid is the final stage of the electrical grid. After the substations have stepped down the voltage to acceptable distribution levels, this stage may be accomplished. Wires lead off from the neighborhood's power lines and connect to individual buildings, (homes, apartments, and businesses,). But first must go through the electric meter to measure how much electricity the customer 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 outlets around the house.

Every home is connected to the electrical grid through some sort of fuse box or Circuit Breaker Panel.

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 hotlines. The hotlines maintain a certain potential (like 120 Volts) compared to the neutral line. There are two types of overhead service drops, a mast service drop, and an underground service connection.

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

A Circuit Breaker is an electrical switch, that cuts off electrical flow, in the event of a possible short circuit or overload. This device is essential in a modern world that runs on electricity. Without a circuit breaker, you could find yourself dealing with household fires on a regular basis. While you can easily call a professional electrician, you can also learn how to wire a circuit breaker yourself, with relative ease.

Because most power panels today are breaker panels, I'm gonna deal exclusively with breaker panels. If you are to do any work inside the main breaker panel the first thing you must do is switch off the main power switch or breaker. This is usually, but not always, at the top of the breaker panel. It should be the largest switch breaker in the panel, and will also be rated the highest amp rating in the panel.

Take the cover of the breaker box off. It is usually held in place by 4 to 6 large screws located on the perimeter of the cover. You may accidentally trip off some of the lower voltage breakers when doing this, however, this is not a problem, as long as you remember to switch them back on, when you're finished.

This is a sketch of what you will find, inside a standard power panel. At the top, in most instances, is the main breaker. The two hot wires from the utility will be connected here. The neutral from the utility is connected to a neutral bar, which can be located on either side and, sometimes, on both sides of the panel. The ground bar, which receives all of the ground wires, is located on either side of the power panel and can be identified by its connection to the ground rod. All of the circuit feeder breakers are located in the middle of the panel. Cables from the various outlets in the house enter the panel through knockouts that are located on the perimeter of the panel. The hot wires are connected to the breakers in the middle of the panel, while the neutrals are connected to the neutral bar, and the ground wires are connected to the grounding bar.

Depending on the size, and gauge of the wire, a knockout bushing must be used when stringing the wire through the panel side. This bushing, for number 14 three wire, and number 14 two wire, is usually half an inch, but the knockouts and bushings could be as big as 3/4 of an inch.

The bushing not only protects the wire from the sharp edges of the panel box, but it also locks the cable and wires in place.

This picture shows the installation of a single pole breaker, protecting a 120 volt, number 12 two Cable, a double pole breaker, protecting a 240 volt, number 10 two Cable, and a double pole breaker, protecting a 120/240 volt, number 10 three Cable. With the breaker switch in the “OFF” position, install it on the main bus. Many breakers have a hooked outer edge, slide it into the hot bus bar until it engages, then firmly push the other end down, over the protrusion on the breaker until you hear a “click”.

This diagram also illustrates some of the most common circuits found in a typical 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 two cable for this circuit, includes 2 conductors and 1 ground wire. A 15 amp circuit is usually used for wall receptacle outlets, and light fixtures.

This diagram illustrates, the arrangement for a 20 amp, 120 volt, double receptacle circuit, with a shared neutral wire. This arrangement is typically used in a kitchen, or over a workbench, where two separate appliance circuits are needed in close proximity to each other. Notice that the breaker is a “Ganged” breaker, which means that it switches, or trips, both circuits at the same time. This arrangement is absolutely protected, but can supply a total of 40 Amps, from a 20 Amp breaker, provided that the load is evenly split between the two receptacles.

This circuit breaker wiring diagram illustrates installing a 20 amp circuit breaker, for a 240 volt circuit. The 12 two gauge cable for this circuit, includes 2 conductors and 1 ground. The white wire is used as a hot in this circuit, and it is usually marked with black tape on both ends, to identify it as such. A neutral wire is not used in this circuit. A dedicated 20 amp circuit, like this, is used for a heavy household appliance, like large window air conditioners.

This is an outdated circuit, that may still be in use. This wiring is for a 30 amp circuit breaker, serving a 30 amp, 240 volt receptacle. The 10 three cable for this circuit, has 3 conductors, and no ground. Although the newer installations will have a bare copper ground. A 30 amp circuit like this may be found in older installations for clothes dryers and maybe a kitchen cooking range as well.

This is a diagram for a new 30 amp circuit breaker, to serve a 30 amp dryer outlet. This is an upgrade of the outdated 30 amp circuit in the previous diagram. This breaker is connected to a 30 amp receptacle, with a 10 three cable, including a ground wire.

This diagram illustrates the wiring for a circuit breaker, with a built-in ground fault, circuit interrupter, or GFCI. This 20 amp, 120 volt breaker, is a form of GFCI, that can be installed at the circuit source. This kind of circuit is used for dishwashers, whirlpool spas, and other locations, where water contact is likely.