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 05, 2022

Blog #15 - Electrical Wiring Diagrams (1 of 8)

December 05, 2022/ Graham VanBrunt

Electrical Engineers and technicians are often called on to install and maintain hundreds of different types of devices. As these devices have grown in variety and complexity, a system of symbols, and conventions evolved to describe the circuits in a shorthand method of documentation. This allows engineers, designers, and technicians, to understand how the circuits that make up a device work, and how its components connect with each other. Although the schematic diagram is the most common document for this function, there are also block diagrams, wiring diagrams, and other diagrams. Each of these documents has a unique function in describing the circuit to aid in under- standing and troubleshooting.

Technicians encounter some differences between North American company schematics, and those produced in European, or Asian countries. In this series you’ll study mostly the schematics you’ll see from North American companies, but once you’re accustomed to reading these, you’ll recognize common characteristics in all other schematics.

Schematic diagrams document the connection points and construction methods of electrical and electronic circuits. This shows a simple schematic diagram of a power supply; on it, you can see some of the conventions used.

Schematic diagrams are often read from left to right, like a book, with inputs on the left and outputs on the right. This isn’t a universal practice, but it’s a good way to begin your analysis of the schematic. Schematic diagrams show the connections of the components in a clear, easily readable format, but they don’t show how the components are physically arranged. In this schematic, you’ll see a plug on the left side; this means the supply (or any device with this symbol) is powered by an AC source, which isn’t shown.

The fuse is in series with the power transformer to prevent damage from overloads, and the switch controls the on and off status of the supply.

Note that neither of the transformer primary wires are grounded.

This shows the symbols for such basic components as wires and connections, switches, power sources, transformers, fuses, and ground connections. In addition to these standard symbols, you’ll sometimes run across symbols that are variations of these, or ones that are specific to certain companies, especially in older schematic diagrams. I will deal with these more specifically later.

In your work, you may encounter a type of schematic called a ladder diagram, as shown here. The general layout of the wires and components resembles a ladder, with vertical rails and horizontal rungs. The input voltage is usually on the left vertical rail; the ground or neutral is on the right vertical rail, and the components are found on the horizontal rungs that connect the two rails. Newer schematics such as this one usually incorporate the symbols used in software that generates the schematics.

This type of schematic is used in control applications for equipment that controls a sequence of operations. For example, a washing machine goes through predefined steps each time a cycle is started, and there are a number of options available at the beginning of and during the wash cycle. Depending on the settings of switches, different actions are possible. In industrial applications, a programmable logic controller (PLC) is often used to control the steps and options with a program installed in the controller. You’ll find PLCs in a variety of industrial applications such as robotic welders, assembly lines, and packaging operations.

Here are some typical symbols used in programmable logic controller diagrams. You’ll see that the symbols on the rungs are switches, motors, contacts, timers, and other high-level devices, and not individual components such as capacitors, diodes, amplifiers, or transistors. Ladder diagrams are usually best understood by reading them from top to bottom and left to right, since the cycle of operations is often performed in that sequence. The power connections are generally at the top of the ladder, and the left rail is the hot side, while the right rail is the neutral, or common. Options in the sequence are determined by the condition of sensors or control settings. Relays, switches, and other controls are always shown in the unenergized state, meaning that the equipment hasn’t been activated to perform the operation.

You’ll encounter three types of diagrams in electricity and electronics:

1) The block diagram,

2) The schematic diagram, and

3) The Wiring Diagram or Layout diagram. Each type of diagram serves its own special purpose.

A block diagram gives you an overview of how the discrete circuits within a device or system interact. Each circuit is represented with a “block” (a rectangle or other shape, depending on the application). Interconnecting lines, sometimes with arrows on one or both ends, reveal the relationships between the circuits.

A schematic diagram (often simply called a schematic) includes every component that a circuit contains, with each component having its own special symbol. This blog is devoted mostly to schematics.

A pictorial diagram, sometimes called a wiring or layout diagram, shows the actual physical arrangement of the circuit elements on a circuit board or chassis, so that you can quickly find and identify components to test or replace.

When you troubleshoot an unfamiliar electronic circuit, you’ll usually start with the block diagram to find where the trouble originates. Then you’ll refer to the schematic diagram (or part of it) to find the faulty component in relation to other components in the circuit.

A Layout or wiring diagram can then tell you where the faulty component physically resides so that you can test it, and if necessary, replace it.

Block diagrams work well in conjunction with schematics to aid circuit comprehension and to streamline troubleshooting procedures. Each block represents all of the schematic symbols related to that part of the circuit. In addition, each block has a label that describes or names the circuit it represents. However, the block does nothing to explain the actual makeup of the circuit it represents. The blocks play a functional role only; they describe the circuit’s purpose without depicting its actual components. Once you’ve gained a basic under- standing of the circuit functions by looking at the block diagram, you can consult the schematic for more details.

To understand how you might use block diagrams, consider these two examples.

First, suppose that you want to design an electronic device to perform a specific task. You can simplify matters by beginning with a block diagram that shows all of the circuits needed to complete the project. From that point, you can transform each block into a schematic diagram. Eventually, you’ll end up with a complete schematic that replaces all of the blocks.

Alternatively, you can go at the task the other way around. Imagine that you have a complicated schematic, and you want to use it to troubleshoot a device. Because the schematic shows every single component, you might find it difficult to determine which part of the device has the problem. A block diagram can provide a clear understanding of how each part operates in conjunction with the others. Once you’ve found the troublesome area with the help of the block diagram, you can return to the schematic for more details.

A schematic diagram acts in effect, as a map of an electronic circuit, showing all of the individual components and how they interconnect with one another. According to one popular dictionary, the term schematic means, “of, or relating to, a scheme diagrammatically.” Therefore, you can call any drawing that depicts a scheme—electronic, electrical, physiological, or whatever, a schematic diagram.

One of the most common schematic diagrams finds a place in almost every car or truck in the United States. Like this schematic diagram of an electronic circuit, that shows all the components relevant to the scheme it addresses. An electronic schematic shows all of the relevant components, and it allows a technician to extrapolate the components and interconnections when testing, troubleshooting, and repairing a small circuit, a large device, or a gigantic system.

A schematic drawing must indicate not only all components necessary to make a specific scheme but also how these components interrelate with one another.

An electronic schematic drawing uses a plain straight line, to indicate a standard conductor, other types of lines represent cables, logical pathways, shielding components, and wireless links. In all cases, when you draw the interconnecting lines, you draw them in order to indicate relationships between the connected components.

A schematic diagram reveals the scheme of a system by means of symbology. On a map, the lines that indicate roadways constitute symbols. But of course, a single black or in this case white line that portrays Route 395 in no way resembles the actual appearance of this highway as we drive on it!. We need to know only the fact that the line symbolizes Route 395. We can make up the other details in our minds. If people always had to see pictorial drawings of highways on paper road maps, those maps would have to be thousands of times larger than those folded-up things we keep in our vehicle glove compartments, and they would be impossible for anybody to read.

On any decent road map, you’ll find a key, or (Legend), to the symbols used. The key shows each symbol and explains in plain language, what each one means. If a small airplane drawn on the map indicates an airport and you know this fact, then each time you see the airplane symbol, you’ll know that an airport exists at that particular site, as shown on this map. Symbology depicts a physical object, (such as an airport, outside a large city) in the form of another physical object (such as an airplane image on a piece of paper). A good road map contains many different symbols. Each symbol is human engineered to appear logical to the human mind. For instance, when you see a miniature airplane on a road map, you’ll reasonably suppose that this area has something to do with airplanes, so a detailed explanation should not be necessary. If, on the other hand, the map maker used a beer bottle to represent an airport, anyone who failed to read the key would probably think of a saloon, or liquor store, not an airport! Because a map needs many different symbols, a good map maker will always take pains to make sure that the symbols make logical sense.

Pure logic will take us only up to a certain point in devising schemes to represent complicated things, especially when we get into the realm of electronic circuits and systems. For example, a circle forms the basis for:

1) a transistor symbol,

2) a light-emitting-diode symbol, and

3) a vacuum tube symbol.

Additional symbols inside the circle tell us which type of component it actually represents. A transistor is an active device, capable of producing an output signal of higher amplitude than the input signal. We can say the same thing about a vacuum tube, but not about an LED.

A circle with electrode symbols inside has been used for many years to represent a vacuum tube. Transistors were developed as active devices to take the places of vacuum tubes, so the schematic symbol for the transistor also started with a circle. Electrode symbols were inserted into this circle as before, but a transistor’s elements differ from a tube’s elements, so the transistor symbol has different markings inside the circle than the tube symbol does. The logic revolves around the circle symbol. Transistors accomplish many of the same functions in electronic circuits as vacuum tubes do (or did), so symbolically they are somewhat similar.

Inconsistencies arise in schematic symbology, and that’s a bugaboo that makes electronics-related diagrams more sophisticated than road maps. A circle can make up a part of an electrical symbol for a device that doesn’t resemble a tube or transistor at all. An LED, for example, can be portrayed as a circle with a diode symbol inside and a couple of arrows outside. An LED is not a transistor or tube, and the electrode symbol at the center clearly reveals this difference. You’ll learn more about specific schematic symbols later.

To further explore how schematic diagrams are used, let’s consider a single component, a PNP transistor. This device has three electrode elements, and although many different varieties of PNP transistors exist, we draw all their symbols in exactly the same way. We might find a PNP transistor in any one of thousands of different circuits! A good schematic will tell us how the transistor fits into the circuit, what other components work in conjunction with it, and which other circuit elements depend on it for proper operation. A transistor can act as:

1) a switch,

2) an amplifier,

3) an oscillator, or

4) an impedance-matching device. A single, specific transistor can serve any one of these purposes. Therefore, if a transistor functions in one circuit

5) as an amplifier, you can’t say that the component will work as an amplifier only, and nothing else. You could pull this particular transistor out of the amplifier circuit and put it into another device to serve as the “heart” of an oscillator.

By knowing the type of component alone, you can’t tell what role it plays in a circuit until you have a good schematic diagram showing all the components in the circuit, and how they all interconnect. Rarely can you get all this information in easy-to-read form by examining the physical hardware. You need a road map…a schematic diagram, to show you all the connections that the engineers and technicians made when they designed and built the circuit.

An electronic circuit is similar to a road map in that it may have many electrical highways and byways. Occasionally, some of these routes break down, making it necessary to seek out the problem and correct it. Even if you can visualize the circuit in your head as it appears in physical existence, you’ll find it impossible to keep in your “mind’s eye” all the different routes that exist, one or more of which could prove defective. When I speak here of visualizing the circuit, I don’t mean the schematic equivalent of the circuit, but the actual components and interconnections, known as the hard wiring.

A schematic diagram gives you an overall picture of a circuit and shows you how the various routes and components interact with other routes and components. When you can see how the overall circuit depends on each individual circuit leg and component, you can diagnose and repair the problem. Without such a view, you’ll have to “shoot in the dark” if you want to get the circuit working again, and you’ll just as likely introduce new trouble as get rid of the original problem!

Look at this schematic…If you’ve had little or no experience with these types of diagrams, you might wonder how you’ll ever manage to interpret it and follow the flow of electrical currents through the circuit that it represents. By the time I am finished with this series of blogs, and, assuming that you already know some basic electricity and electronics principles, you’ll wonder how you ever could have let a diagram like this intimidate you.