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.

December 11, 2022

Blog #16 - Block Diagrams (2 of 8 in the Series) Electrical Wiring Diagrams

December 11, 2022/ Graham VanBrunt

Block Diagrams. A block diagram portrays the general construction of an electronic device, or system. A block diagram can also provide a simplified version of a circuit by separating the main parts, and showing you how they are interconnected.

This is a block diagram of a device that converts alternating current, to direct current. The terminal at the left accepts the AC input. In sequence, going from left to right, the electricity passes through the transformer, the rectifier, and the filter, before arriving at the output as DC. In this case, the lines that connect the blocks do not have arrows because readers will naturally assume that the flow goes from left to right. The input terminal resides at the left-hand end of the diagram, and the output lies on the extreme right. In more complicated block diagrams, the interconnecting lines may include arrows to show which block affects which or to indicate the general direction of signal flow when it might not otherwise be clear.

Another way of using block diagrams starts with a finished schematic diagram. Imagine that the schematic is complicated and that the equipment whose circuit it represents does not work properly. Although schematic diagrams can describe the functioning of an electronic circuit, they are not as clear and basic as a functional block diagram for that purpose.

In the absence of a pre-existing block diagram, a technician would have to start with the schematic, laboriously identify each stage in the system, and then draw the entire system diagram in block form. When finished, the block diagram would reveal how each stage interacts with the others.

Using this method, one or more stages could be identified as a possible trouble area. Then the technician would refer to the original schematic and conduct tests in specific areas, based on his or her knowledge of how each stage works at the component level.

In practice, you’ll often encounter block diagrams. If presented without accompanying schematics, a block diagram describes the basic functional operation of an electronic device or system. The block diagram can prove most useful when you don’t need to know the functions of individual components.

We can describe the operation of a specific type of wireless transmitter, say an amplitude-modulated voice transmitter, such as the type found in Citizens Band radios, by means of a block diagram. This diagram will apply to most other AM voice radio transmitters. Of course, no two transmitters built by different manufacturers are exactly alike, but all of them contain the same basic circuit sections as far as functionality goes. One type of oscillator might work differently from another type, but they all do the same thing: generate a radio-frequency signal! When we need to know or portray, individual differences between circuits that do essentially the same things, then we need schematic diagrams.

The block diagram here illustrates the various parts of a strobe light circuit. Let’s go through the diagram block by block to under- stand how it works. The input signal enters at the left; it’s utility AC, such as we get from a standard wall outlet. In the United States and some other countries, this AC has a nominal voltage of 117 volts and a frequency of 60 hertz, where “hertz” means “cycles per second.” (In some countries, the voltage is about 234 Volts, and in some countries, you’ll find a frequency of 50 Hz rather than 60 Hz).

The input AC goes to a fuse, and also to a combination of components that provide timing. The top path, where the fuse is located, leads to a diode-type rectifier, and the rectifier output passes directly to one terminal of the three-terminal strobe lamp. The rectifier also outputs to an adjuster that provides a variable flash rate for the lamp. The output from that adjuster goes to a transformer, which supplies the remaining two outputs required to operate the lamp.

This shows a power supply that produces several different voltage outputs. As you go through this diagram from the left, (the input) to the bottom and the right, (the outputs). Note that the circuit is powered with 120 volts AC, quite close to the nominal 117 Volts commonly found at utility outlets in North America.

The input AC goes through a filter and then splits into two paths. Part of the AC goes to the “lower” transformer that provides 16 Volts AC and 3 Volts AC output along with a ground connection. From the filter, the input voltage gets fed to another transformer that derives the voltages to be converted to DC.

One output of the transformer goes to a rectifier that provides 12 volts DC without any voltage regulation. The other transformer output goes to a separate rectifier that provides 18 Volts DC, also unregulated. This transformer output also serves as a diagnostic detector for a power “off” condition. That line is further tapped to join with the output of the voltage regulator, to provide 12 Volts DC, with voltage regulation.

Block diagrams are comparatively easy to draw, comprising squares or rectangles along with interconnecting lines (sometimes with arrows). More sophisticated block diagrams also include triangles to represent circuit blocks built around specialized amplifiers constructed within integrated circuits known as chips.

Here is another block diagram of an AM radio transmitter. The microphone preamplifier stage goes to the input of the audio amplifier stage (note the direction of the arrows). The output of the audio amplifier goes to the matching network, which in turn goes to the RF amplifier section.

The crystal oscillator is also connected to the RF amplifier section, whose output leads into the RF tuning network. Only one connection exists between the audio section of the circuit and the RF section: the one between the matching network and the RF amplifier. This block diagram, with its arrows, tells us not only how the components of the system connect to one another, but also the sequence of events or direction of signal flow.

Block diagrams can describe the functioning of electronic circuits, but in the world of computers, another form of diagramming is sometimes used to portray the functioning of a program. This system is called flowcharting. A flowchart resembles a block diagram, except that the symbology applies to the sections of a computer program, an intangible thing (as opposed to an electronic circuit, a tangible thing). A flowchart provides a graphic representation of the logical paths that a computer will take as it executes a particular program. Flowcharts are often prepared in conjunction with specifications and are modified as the requirements change to fit within the constraints of the computer system.

For complex problems, a formal written specification might be necessary to ensure that everyone involved understands and agrees on what the problem is, and on what the results of the program should be. To illustrate this concept, let’s suppose that a teacher wants to write a computer program that will determine a student’s final grade for a course by calculating an average from grades the student has received over a certain period of time. The teacher will supply the grades to the program as input. Only the average grade is needed as an output. Now, we can make an orderly list of what the program has to do:

1) Input the individual grades.

2) Add the grade values together to find their sum.

3) Divide the sum by the number of grades to find the average grade.

4) Print out the average grade.

We can prepare a flowchart of the program, as shown here. As we can see, the flowchart graphically presents the structure of the program, revealing the relationship between the steps and paths. When the flow of control is complicated by many different paths that result from many decisions, a good flowchart can help the programmer sort things out. The flowchart can serve as a thinking-out tool to understand the problem and to aid in program design. The flowchart symbols have English narrative descriptions rather than programming language statements because we want to describe what happens, not how it happens.

It takes a lot of time to conceive and draw up a formal flowchart and modifying a flowchart to incorporate changes, once a program has been written and its flowchart composed, can prove difficult. Because of these limitations, some programmers will shy away from the use of a flowchart, but for others, it can provide valuable assistance in understanding a program. In order to promote uniformity in flow- charts, standard symbols have been adopted, the most common of which are shown and defined in this slide.

The normal direction of processes in a flowchart runs from…top to bottom and from left to right, the same way as people read books in most of the world. Arrowheads on flow lines indicate direction. The arrows can be omitted if but only if, the direction of flow is obvious without them.

This is a flowchart for a program that duplicates punched cards and at the same time prints the data on each card. Keep in mind that this particular “beast” is of historical interest only! (Were you born long enough ago to remember punch cards for inputting programs into computers? I recall using them, all the way back in the 1960s when I attended university. I guess that little fact kinda dates me, doesn’t it?

Tracing the flow of the program. The program begins at the “Start” oval at the top and proceeds in the direction of the arrows. In the first box below “Start,” the program reads a card. Then the program punches the card’s contents (data) as holes in a blank piece of heavy paper and sends the data to a printer.

The program then goes back to the top and reads the next card. The circles marked, “A", represent inflow and outflow points. In this case, they’re superfluous, but in complicated flowcharts, they can be useful when it would create a mess to include all the applicable dashed lines. The program repeats itself as long as it has cards to read and punch.

In a sophisticated flowchart, we might see several different symbols. Oval boxes show, start, or stop points; Arithmetic operations go in rectangular boxes; Input and output instructions go in upside-down trapezoids. If we want to show a program that someone wrote earlier within the context of a larger flowchart, we don’t necessarily have to draw the flowchart for the inside program. Rather, we might represent the entire program as a flattened hexagon.

If a box indicates a decision, we use a diamond shape; A five-sided box portrays a part of the program that changes itself.

A small circle identifies a processing junction point. Such a point in the program can go to several places.

A small five-sided box, which has the shape of the home plate on a baseball field, shows where one page of a flowchart connects to the next if the entire flowchart has more than one page. The intermediate junction and off-page connection points are labeled with numbers and letters to let readers know that all like symbols, with the same character inside, are meant to be connected together.

Arrows indicate the direction of the flow.

Looking at the flowchart for duplicating punched cards, suppose that you want to change the card-punching program so that the computer skips blank cards and duplicates only those cards with some holes in them.

Because the computer must make a decision about each card, you’ll need to include a decision block in the flow- chart.

Except for the decision block, this shows the same process as the previous process path does. The program begins in the “Start” oval at the top and then goes to the block marked “Reed a card.” From there, the program moves on to the decision block labeled “Card blank?” If the answer is “Yes,” the program proceeds to the connection circle marked, “A” and back to the top to read the next card. If the answer is “No” (the card has holes in it), the program instructs the hardware (the physical components of the computer) to punch a duplicate card and print its contents. Then the program goes to another circle marked, “A” and back to the starting point.

These are simple flowcharts, showing a process that uses only input and output devices and that does no calculations. Most programs and flowcharts involve more complicated processes.

Closely related to the block diagram is the "operating diagram”. It is also closely related to the one-line diagram, but without the protection and control data that's on one-line diagrams. Operating diagrams are used by the operating staff to operate the system whether it's electrical, water, or fluid flow, or any other system that needs to be understood when operating it. In this series of blogs, we will be concentrating on the electrical systems.

Operating diagrams are similar to block diagrams in that the system is made up of blocks and pictorial elements that represent items such as breakers, disconnect switches, transformers, etc, to which power runs along a single connecting line. The flow of power is represented by single lines connecting these elements.

Operating diagrams are designed primarily to assist in the operation and maintenance of a power system. In addition to diagrams of electrical systems, operators and maintenance personnel must also refer to diagrams of compressed air, steam and hydraulic systems. A large portion of the information in any diagram is conveyed by symbols. In order that each diagram will convey the same information to everyone reading it, symbols have for the most part been standardized. The Standard for electrical operating diagrams is quite rigid and there is virtually no duplication of symbols in use.

The field of microcomputers uses many different types of diagrams that deal mostly with software (the operating systems and programs) rather than hardware (the physical components). From a purely electronic standpoint, functional diagrams abound and are usually more numerous than schematic diagrams in the computer world. From an understanding standpoint, block diagrams can serve to display machine functions in general, but hardware maintenance and repair procedures require well-defined schematic drawings. Computers take advantage of the latest state-of-the-art developments in electronic components and are relatively simple from this standpoint, especially when you consider all they can do. However, from a pure electronics standpoint and as far as schematic diagrams are concerned, computers are highly complex; it would take many pages of schematics to represent even the most rudimentary computer.

Block diagramming can help you understand the general functioning of electronic circuits. Block diagrams are easy to draw, usually requiring only a marking instrument, some paper, and a straightedge (or a vector graphics computer program and a little bit of training on it). Schematic diagrams, in contrast, need more tools and can in some cases, take many hours to render in a form that people can easily read and interpret.