Three Phase Electricity Explained

Electricity supply covers generation, transmission, distribution, grid infrastructure, voltage regulation, frequency control, power quality, protection, SCADA, and load management to ensure reliable energy delivery to industrial, commercial, and residential loads.

What Is Electricity Supply?

Electricity supply is generation, transmission and distribution of power with set voltage, frequency and reliability.

✅ Involves generation, HV transmission, MV/LV distribution networks

✅ Ensures voltage regulation, frequency control, and power quality

✅ Uses SCADA, protection relays, and load forecasting for reliability

What Is Electricity Supply?

Electricity Supply is a complex balanced system of electric power generation and real time customer demand. Production (supply) and consumption (demand) dictate electricity pricing in the United States and Canada.  For a regional view, the analysis at Electricity Demand in Canada highlights how seasonal peaks and resource availability shape prices.

Where does the term "electricity supply" originate? How does that supply move from one point to another? These are most important questions to ask when you want to understand the electric power industry.

If you're new to the vocabulary, the concise glossary at Electricity Terms can clarify definitions used throughout the industry.

The first thing to know is that electric power is generated in the United States and Canada in power plants which house electrical generators. Then, power is transported (transmission and distriubtution) through the power grid to the customer. This complex network of transmission lines delivers power to industrial, commercial, institutional and residential customers. For a step-by-step overview of system operations, Electricity: How It Works explains generation, transmission, and distribution in practical detail.

In the electricity industry, transmission and distribution wires do the work of transporting power to satisfy electricity demand during real time peak demand. This is the job of the electricity market. The natural gas and fossil fuels industry works in the same way. These lines run from generating station to substations (sometimes over great distances, like in the case of British Columbia and Manitoba where generation is in the far north and the consumption is in the south. This is where the voltage is reduced for local consumption. Substations are usually located close to where the electricity is consumed. 

For background on core power concepts, the primer at Electricity Power connects voltage, current, and load to real-world grid behavior.

The various prices of electricity depends on the electricity supply mix and the energy efficiency of the customer. Electricity energy supply is usually measured in terawatt hours.

The system design is of three-phase alternating current electrical generation and distribution, which was invented by Nikola Tesla in the 19th century. He considered that 60 Hz was the best frequency for alternating current (AC) power generating Electricity Supply. He preferred 240 V, which was claimed to be better for long supply lines. Thomas Edison developed direct current (DC) systems at 110 V and this was claimed to be safer. For more information about the early battles between proponents of AC and DC supply systems see War of Currents. For foundational fundamentals beyond this history, the overview at What Is Electricity clarifies the principles common to both AC and DC systems.

The German company AEG built the first European generating facility to run at 50 Hz, allegedly because the number 60 did not fit into the numerical unit sequence of 1, 2, 5…. At that time, AEG had a virtual monopoly and their standard spread to the rest of the continent. In Britain, differing frequencies (including 25 Hz 40 Hz and DC) proliferated, and the 50 Hz standard was established only after World War II.

To see how frequency standards interact with generation and end-use performance, the explainer at How Electricity Works ties design choices to everyday operation.

Originally much of Europe was 110 V too, just like the Japanese and the US system today. It was deemed necessary to increase the necessary voltage to draw more electrical power with reduced energy loss and voltage drop from the same copper wire diameter.

The choice of utilization voltage is governed more by tradition than by optimization of the distribution system. In theory, a 240 V distribution system will use less conductor material to deliver a given quantity of power. Incandescent lamps for 120 V systems are more efficient and rugged than 240 V lamps, while large heating appliances can use smaller conductors at 240 V for the same output rating. Practically speaking, few household appliances use anything like the full capacity of the outlet to which they are connected. Minimum wire sizes for hand-held or portable equipment is usually restricted by the mechanical strength of the conductors. One may observe that both 240 V system countries and 120 V system countries have extensive penetration of electrical appliances in homes. National electrical codes prescribe wiring methods intended to minimize the risk of electric shock or fire. For household applications, home electricity basics show how these voltage considerations affect outlets, circuits, and safety practices.

Areas using (approximately) 120V allow different combinations of voltage, suitable for use by a variety of classes of electrical equipment.

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Harmonic distortion is the deviation from the ideal electrical waveform caused by nonlinear loads. It impacts power quality, increases heat in equipment, and can lead to system inefficiencies. Monitoring and mitigation are essential in industrial electrical systems.

What is Harmonic Distortion?

Harmonic distortion is not a new phenomenon in power systems. Concern over distortion has fluctuated several times throughout the history of AC electric power systems.

✅ Reduces overall power quality and system reliability

✅ Can damage equipment and increase heat generation

✅ Requires monitoring to ensure system efficiency and safety

In the 1930s and 1940s, the primary sources were transformers, with the primary problem being inductive interference with open-wire telephone systems. Early arc lighting caused similar concern due to its harmonic content, just as today’s electronic power converters do.

Today, nonlinear devices like variable frequency drives (VFDs), arc furnaces, computer power supplies, and LED lighting introduce significant harmonic distortion into electrical systems. Nonlinear devices do not draw current in a linear relationship to voltage, which distorts the sinusoidal waveform and introduces harmonic currents. Harmonic distortion is one of the many issues covered in our comprehensive Power Quality resource channel, which explores causes, effects, and solutions.

Why It Matters

• Harmonics degrade power quality

• Increase energy losses and heat in conductors and transformers

• Lead to premature failure of motors and sensitive electronics

• Interfere with communication lines

In contrast, voltage sags and interruptions are nearly universal to every feeder and represent the most numerous and significant power quality deviations. The end-user sector suffers more from harmonic problems than the utility sector. Industrial users with adjustable speed drives, arc furnaces, induction furnaces, and similar equipment are significantly more susceptible to problems caused by harmonic distortion. To understand the relationship between harmonics and apparent energy flow, see our explanation of Apparent Power vs Real Power.

A good assumption for most utilities in the United States is that the sine wave voltage generated in central power stations is very good. In most areas, the voltage found on transmission systems typically has much less than 1% distortion. However, the distortion increases as the load approaches. At some loads, the current waveforms barely resemble a sine wave. Electronic power converters can chop the current into seemingly arbitrary waveforms. Managing nonlinear loads often requires Power Factor Correction to reduce harmonic effects and improve efficiency.

Industry Standards

• IEEE 519: Sets recommended harmonic limits for both voltage and current.

• IEC 61000-4-7: Defines methods of measuring harmonics and interharmonics.

Harmonic Distortion and Nonlinear Devices

Harmonic distortion is caused by nonlinear devices in the power system. A nonlinear device is one in which the current is not proportional to the applied voltage. Figure 1 illustrates this concept using the case of a sinusoidal voltage applied to a simple nonlinear resistor, where the voltage and current vary according to the curve shown. While the applied voltage is perfectly sinusoidal, the resulting current is distorted. Increasing the voltage by a few percent may cause the current to double and exhibit a different waveform. You can calculate your system’s power quality impact using our Apparent Power Calculator for precise performance metrics.

This is the source of most harmonic distortion in a power system. Figure 1 illustrates that any periodic, distorted waveform can be expressed as a sum of sinusoids. When a waveform is ideal from one cycle to the next, it can be represented as a sum of pure sine waves in which the frequency of each sinusoid is an integer multiple of the fundamental frequency of the distorted wave. This multiple is called a harmonic of the fundamental, hence the name of this subject matter. The sum of sinusoids is referred to as a Fourier series, named after the great mathematician who discovered the concept. Nonlinear loads like VFDs and arc furnaces can affect grounding; learn more in our guide to Electrical Grounding.

Fig. 1. Current distortion caused by nonlinear resistance

Voltage and Current Distortion

The term "harmonics" is often used by itself without further qualification. Generally, it could mean one of the following three:

1. The harmonic voltages are too great (the voltage is too distorted) for the control to properly determine firing angles.

2. The harmonic currents are too great for the capacity of some devices in the power supply system, such as transformers, and the machine must be operated at a lower than rated power.

3. The harmonic voltages are too great because the harmonic currents produced by the device are too great for the given system condition.

Clearly, there are separate causes and effects for voltages and currents, as well as some relationship between them. Thus, the term harmonics by itself is inadequate to describe a problem definitively. Nonlinear loads appear to be sources of harmonic current, injecting harmonic currents into the power system. For nearly all analyses, it is sufficient to treat these harmonic-producing loads simply as current sources. There are exceptions to this as described later.

Fig 2. Harmonic currents flowing through the system impedance result in harmonic voltages at the load.

Voltage distortion is the result of distorted currents passing through the linear, series impedance of the power delivery system, as illustrated in Fig. 2. Although assuming that the source bus is ultimately a pure sinusoid, there is a nonlinear load that draws a distorted current. The harmonic currents passing through the system's impedance cause a voltage drop for each harmonic. This results in voltage harmonics appearing at the load bus. The amount of voltage distortion depends on the impedance and the current. Assuming the load bus distortion stays within reasonable limits (e.g., less than 5%), the amount of harmonic current produced by the load is generally constant.

While the load current harmonics ultimately cause voltage distortion, it is worth noting that the load has no control over the voltage distortion. The same load put in two different locations on the power system will result in two different voltage distortion values. Recognition of this fact is the basis for the division of responsibilities for harmonic control that is found in standards such as IEEE Std 519-1992.

• Control over the amount of harmonic current injected into the system occurs at the end-use application.

• Assuming the harmonic current injection is within reasonable limits, the control over voltage distortion is exercised by the entity that controls the system impedance, typically the utility.

One must be careful when describing harmonic distortion phenomena, as there are distinct differences between the causes and effects of harmonic voltages and currents. The use of the term harmonics should be qualified accordingly. By popular convention in the power industry, the term is used by itself most of the time when referring to load apparatus, indicating that the speaker is referring to the harmonic currents. When referring to the utility system, the voltages are generally the subject. For systems affected by harmonic-induced overheating, understanding Capacitor Bank applications is essential for voltage support and harmonic filtering. For in-depth harmonic analysis, explore our guide to using a Power Quality Analyzer to identify waveform distortion and power anomalies.

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Wireless electricity transmits power without wires using electromagnetic fields, such as magnetic resonance or microwave transmission. It enables charging devices remotely, powering sensors, and improving efficiency in smart grids, EVs, and wireless charging systems.

What is Wireless Electricity?

Wireless electricity refers to the transmission of electrical energy without physical conductors like wires.

✅ Powers devices through electromagnetic fields, like inductive coupling

✅ Enables contactless charging in consumer electronics and EVs

✅ Supports smart grids, IoT, and remote sensors with flexible energy delivery

Wireless electricity, also known as wireless power transmission, was first conceptualized by Nikola Tesla, a pioneer in the field of alternating current (AC) electricity. Tesla’s groundbreaking experiments at Colorado Springs in 1899 showcased how power could be transmitted without wires using a magnetic field. He used a Tesla coil to transmit 100 million volts of high power over a distance of 26 miles, wirelessly powering 200 light bulbs and an electric motor. His vision was to develop a wireless system capable of transmitting power over long distances with minimal energy loss.

Tesla’s system relied on a high-frequency alternating current and magnetic resonance to transmit power wirelessly. His experiments with the Tesla coil laid the groundwork for modern wireless technologies, including short-range wi

reless power transmission systems, such as wireless charging pads and Wi-Fi routers. Wireless charging pads today utilize magnetic fields to transmit power to devices, a concept similar to Tesla’s idea of harnessing the Earth’s resonance to transmit power over longer distances. Tesla’s vision extended beyond short-range wireless systems—he dreamed of a global system where energy flows freely through the air without requiring a direct line of sight.

Tesla’s experiments also demonstrated the efficiency of wireless systems. The Tesla coil could transmit power wirelessly to fluorescent light bulbs even when they were several feet away from the coil. This concept of powering devices wirelessly has evolved over time, with companies like Wi-Charge developing systems to transmit power wirelessly to small devices. In Tesla’s time, he envisioned a world where any amount of power could be transmitted wirelessly across the globe. However, financial struggles eventually led to the abandonment of his wireless power transmission projects, including the unfinished Wardenclyffe tower on Long Island. Devices powered wirelessly still rely on efficient energy flow, making concepts such as electrical resistance and impedance crucial to design and performance.

Despite Tesla’s challenges, modern advancements have kept his vision alive. Short-range wireless power transmission systems, like those used in Wi-Fi routers and wireless charging pads, are now commonplace. These technologies utilize magnetic fields to transmit power wirelessly over short distances, offering a practical solution for wirelessly charging devices such as smartphones and laptops. Wi-Charge is exploring the potential of wirelessly charging devices without requiring close contact, enabling more flexible and efficient energy distribution. Tesla’s coil and modern systems like Wi-Charge operate based on resonant principles, closely related to inductance and capacitance.

Modern Innovations in Wireless Electricity

Recent breakthroughs have brought Tesla’s dream closer to reality:

• In 2024, DARPA successfully transmitted 800 watts of power over 5 miles using a laser beam—enough to make popcorn at the receiver site.

• KAIST in South Korea demonstrated the ability to charge 40 smartphones at once using magnetic resonance over a distance of 5 meters.

• Detroit’s Corktown district now hosts a functioning inductive charging roadway, allowing EVs to charge wirelessly while in motion.

These examples show that wireless electricity is no longer a distant vision but a rapidly advancing technology with real-world applications. Concepts such as watts, volts, and amperes remain fundamental even in advanced wireless systems.

Types of Wireless Power Transmission Technologies

Applications of Wireless Electricity

• Consumer Electronics: Wireless charging pads and smart home devices are now common.

• Electric Vehicles (EVs): Inductive charging roads and parking pads reduce dependency on cable stations.

• Medical Implants: Enables powering of implants and biosensors without invasive wiring.

• Remote Sensors: In agriculture, factories, and infrastructure, wireless power extends sensor life.

• Smart Grids: Flexible energy distribution for remote locations and emergency response.

Challenges and Future Outlook

Despite its promise, wireless electricity faces challenges:

• Efficiency drops over distance

• Alignment issues in inductive systems

• Line-of-sight limitations in laser and IR systems

• Safety regulations for high-power beaming

However, the future is promising. Emerging materials, such as metamaterials and metasurfaces, are enhancing transmission efficiency. AI-enhanced beam control, dynamic alignment systems, and frequency-agnostic receivers are under development.

From Tesla's early experiments to DARPA's record-setting laser transmission, wireless electricity is evolving into a transformative force. As the technology matures, its applications will expand, powering a world that may one day be truly wire-free.

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Basic electricity refers to the fundamental concepts of electric charge, current, voltage, and resistance. It explains how electric circuits work, how energy flows, and how components like wires, batteries, and switches interact in homes, schools, and industries.

What is Basic Electricity?

Basic electricity refers to the foundational principles that explain how electric energy is generated, transmitted, and used in circuits. When an electric current flows through a conductor, it creates a magnetic field (or “flux”) around it.

✅ Explains current, voltage, resistance, and power in simple terms

✅ Describes how electric circuits operate and transfer energy

✅ Essential for understanding household wiring, batteries, and switches

Understanding the fundamentals of voltage is essential for grasping how electric circuits function — see our full explanation of voltage.

The strength of this magnetic field increases when the conductor is shaped into a coil with multiple turns. In electrical engineering, this coiled conductor is known as an inductor. If a steady direct current (DC) flows through the coil, it forms an electromagnet—an object with magnetic properties that can be switched on and off using a basic electrical switch.

Basic Electrical Theory

There are four basic electrical quantities that we need to know:

• Current

• Potential Difference (Voltage)

• Power

• Resistance

Electrical Current

Current is the movement of electric charge through a conductor. Each electron carries a charge of 1.6 × 10⁻¹⁹ coulombs—too small to measure individually—so we measure charge in groups called coulombs. When 1 coulomb of charge passes through a point in a circuit per second, the current is  1 ampere (A). Electric current is measured in amperes and is essential to the functioning of all electrical systems. Learn how voltage drop affects electrical performance and safety in residential and industrial systems. You can estimate losses in long-distance wiring with our easy-to-use voltage drop calculator. For step-by-step guidance on circuit loss calculations, explore the voltage drop formula explained clearly.

Potential Difference

Voltage, or potential difference, refers to the energy per unit charge in a circuit. It represents the work each charge can perform. Think of voltage as the electrical pressure that pushes electrons through a conductor. Higher voltage means more potential energy available to do work, such as lighting a bulb or powering a motor.

Power in a Circuit

Electrical power is the rate at which energy is used or transferred in a circuit. It can be calculated using the formula:

Power (W) = Voltage (V) × Current (A)

This equation is fundamental in both residential and industrial applications, from estimating energy usage to designing electrical systems.

Electrical Resistant Behaviour

Resistance is the opposition to the flow of electric current. It determines how much current will flow for a given voltage. Materials like copper have low resistance and conduct electricity well, while materials like rubber have high resistance and are used as insulators. Learn how voltage drop affects electrical performance and safety in residential and industrial systems.

Electromagnetic Induction

There’s a reciprocal relationship between electric current and magnetism. When a magnet is moved past a conductor at a right angle, it induces a voltage in the conductor—a principle known as electromagnetic induction. The polarity of the induced voltage depends on the direction and orientation of the magnetic field.

This effect becomes more noticeable when the conductor is formed into a coil. As the north pole of the magnet passes the coil, voltage is induced, and current flows. When the south pole passes, the induced voltage reverses polarity, and the current changes direction. This principle is the foundation of generator operation. You can estimate losses in long-distance wiring with our easy-to-use voltage drop calculator.

The Generator and the Sine Wave

In an electric generator, coils placed on opposite sides of a rotating magnet generate alternating current (AC). These voltages combine, doubling the output. For example, a 120-volt, 60-Hz generator creates a wave that oscillates from +169.7V to -169.7V.

This wave is called a sine wave because the voltage at any point corresponds to the sine of the magnet’s angle of rotation. The cycle repeats 60 times per second in North America (60 Hz), creating the household AC power we are familiar with. For step-by-step guidance on circuit loss calculations, explore the voltage drop formula explained clearly.

Forms of Electricity: AC and DC

Electricity exists in two major forms:

• Alternating Current (AC): The direction of current flow alternates regularly. AC electricity is used in power grids because it is easier to transmit over long distances and is compatible with devices such as transformers and capacitors.

• Direct Current (DC): The current flows steadily in one direction. DC is commonly used inside electronics and battery-powered devices. Unlike AC, the voltage remains constant, making it easy to measure with a DC voltmeter.

AC – Alternating Current

Alternating current is the most common form of electricity used in homes, businesses, and utilities. It alternates direction 50–60 times per second, depending on the region. AC is generated by AC generators and is favored for its ability to change voltage levels easily, making it efficient for transmission over long distances. Sudden dips in power can disrupt equipment — find out what causes voltage sag and how to prevent it.

DC – Direct Current

Direct current flows continuously in one direction. Because its voltage is steady or changes very slowly, it’s easy to measure. It is used in battery-powered systems and internal electronic circuits. Unlike AC, DC cannot be easily stepped up or down in voltage without the use of complex circuitry.

When calculating AC power, engineers use RMS (Root Mean Square) voltage, which gives an effective value comparable to DC. For example, 120V AC RMS is equivalent in power to 120V DC, despite the AC waveform's variations. Discover how water and electricity interact, including safety considerations and risks in common environments.

Transformers and Induction

Transformers, built using coiled wires around iron cores, rely on electromagnetic induction. When AC flows through the primary coil, it creates a changing magnetic field that induces a voltage in the secondary coil. This allows voltage to be stepped up or down for different uses, such as high-voltage transmission or low-voltage device operation.

Atoms, Electrons, and Electric Charge

To fully grasp electricity, it’s essential to understand atomic structure. All matter is made up of atoms, which contain a nucleus of protons (positive) and neutrons (neutral), surrounded by orbiting electrons (negative). The outermost electrons—called valence electrons—can be knocked loose by energy, creating an electric current.

When electrons leave an atom, it becomes positively charged. This movement of charge is the essence of electricity. The ability of atoms to gain or lose electrons determines whether a material is a conductor (like copper) or an insulator (like plastic).

Electrical Charge and Attraction

One universal rule in electricity and magnetism is that like charges repel and opposite charges attract. A positively charged object will attract a negatively charged one. This principle governs everything from how circuits function to how magnetic fields interact with conductors. To understand how energy use is measured over time, read our overview of the watthour meter and its function.

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Windmills for electricity use wind energy to generate clean, renewable power. These wind turbines convert kinetic energy into electrical energy, reducing carbon emissions and dependence on fossil fuels. 

What are Windmills for Electricity?

Windmills for electricity are modern devices that transform kinetic wind energy into electrical power.

✅ Harness renewable energy for clean power

✅ Reduce carbon footprint and dependence on fossil fuels

✅ Support sustainable power generation worldwide

Windmills for electricity are part of a broader shift toward renewable energy, providing clean alternatives to fossil fuels for homes, businesses, and utilities.

History of Windmills

Windmills for electricity - Mankind has been harnessing the wind's energy for many years. From Holland to traditional farms around the world, windmills were used in the past for pumping water through primitive irrigation systems or to grind grain. Then, the wind turned large "sails" that were connected by a long vertical shaft, which was attached to a grinding machine or a wheel that turned and drew water from a well. Today's turbines harness the energy of the wind to turn large metal blades, which in turn spin a generator that produces electric power. Alongside wind, other renewable energy sources like solar, biomass, and tidal energy are shaping a diversified and sustainable energy future.

From the mid-1970s to the mid-1980s, the United States government collaborated with industry to advance windmill technology for power generation and enable the development of large commercial wind turbines. NASA led this effort at the Lewis Research Center in Cleveland, Ohio, and it was an extraordinarily successful government research and development activity.

National Science Foundation

With funding from the National Science Foundation and later the Department of Energy (DOE), a total of 13 experimental wind turbines were put into operation, including four major wind turbine designs. This research and development program pioneered many of the multi-megawatt turbine technologies in use today, including steel tube towers, variable-speed generators, composite blade materials, partial-span pitch control, as well as aerodynamic, structural, and acoustic engineering design capabilities. The large Windmills For Electricity developed under this effort set several world records for diameter and power output. The Mod-2 wind turbine cluster produced a total of 7.5 megawatts of power in 1981. Government incentives, such as alternative energy tax credits, have played a major role in expanding wind power adoption across North America.

Wind Turbine Technology

In 1987, the Mod-5B was the largest single wind turbine operating in the world with a rotor diameter of nearly 100 meters and a rated power of 3.2 megawatts. It demonstrated an availability of 95 percent, an unparalleled level for a new first-unit wind turbine. The Mod-5B featured the first large-scale variable-speed drive train and a sectioned, two-blade rotor, which enabled easy transport of the blades.

Later, in the 1980s, California provided tax rebates for ecologically harmless wind turbines. These rebates helped fund the first major deployment of wind power for the utility grid. These turbines gathered in large wind parks such as at Altamont Pass, would be considered small and uneconomical by modern wind power development standards.

In the 1990s, as aesthetics and durability became more important, turbines were placed atop steel or reinforced concrete towers. Small generators are connected to the ground tower, and then the tower is raised into position. Larger generators are hoisted into position atop the tower, and a ladder or staircase is located inside the tower to allow technicians to reach and maintain the generator.

Originally, wind turbines were built right next to where their power was needed. With the availability of long-distance electric power transmission, wind generators are now often on wind farms in windy locations, and huge ones are being built offshore, sometimes transmitting power back to land using high-voltage submarine cable. Since wind turbines are a renewable means of generating power, they are being widely deployed, but their cost is often subsidized by taxpayers, either directly or through renewable energy credits. Much depends on the cost of alternative energy sources. The cost of wind generators per unit of power has been decreasing by about 4% per year.

Modern Wind Turbines

The most modern generations of Windmills for electricity are more properly called wind turbines, or wind generators, and are primarily used to generate electric power. Modern windmills are designed to harness the energy of the wind and convert it into electric energy. The largest wind turbines can generate up to 6 MW of power (for comparison, a modern fossil fuel power plant generates between 500 and 1,300 MW). Many large-scale renewable energy projects now combine wind farms with solar and storage systems, ensuring reliable, clean power for communities worldwide.

Small wind turbines can generate as little as a few kilowatts, while larger models produce up to 100 kilowatts or more, depending on design and location. These devices capture moving air, and as wind turbines operate, the kinetic energy generated can be used directly or sent into the electrical grid. On a utility scale, wind farms combine many large turbines to deliver massive amounts of energy, powering thousands of homes and businesses. This range of applications, from residential to industrial, demonstrates the versatility of wind technology in meeting diverse energy needs.

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Capacitors store electrical energy via a dielectric, offering capacitance for filtering, smoothing, and decoupling in AC/DC circuits, RC networks, and power supplies, spanning ceramic, film, and electrolytic types with distinct impedance profiles.

What Are Capacitors?

Capacitors store charge using a dielectric, providing capacitance for filtering, timing, and decoupling in circuits.

✅ Types: ceramic, film, tantalum, electrolytic; surface-mount or through-hole

✅ Functions: decoupling, bulk energy storage, timing, AC coupling

✅ Key specs: capacitance, voltage rating, ESR/ESL, tolerance, ripple

Capacitors for Power Factor Correction

It is desirable to add shunt capacitors in the load area to supply the lagging component of current with a positive negative charging electrons. The cost is frequently justified by the value of circuit and substation capacity released and/or reduction in losses. Installed cost of shunt capacitors is usually least on primary distribution systems and in distribution substations. For foundational context, see what a capacitor is to understand reactive power roles.

The application of shunt capacitors to a distribution feeder produces a uniform voltage boost per unit of length of line, out to its point of application. Therefore, it should be located as far out on the distribution system as practical, close to the loads requiring the kilovars. There are some cases, particularly in underground distribution, where secondary capacitors are economically justified despite their higher cost per kilovar. The placement effectiveness also depends on capacitance characteristics relative to feeder impedance.

Development of low-cost switching equipment for capacitors has made it possible to correct the power factor to a high value during peak-load conditions without overcorrection during light-load periods. This makes it possible for switched capacitors to be used for supplementary voltage control. Time clocks, temperature, electric charge voltage, current flows, and kilovar controls are common actuators for high frequency capacitor switching. Utilities typically choose among several types of capacitors to balance switching duty and reliability.

Capacitor Installations

Capacitors for primary systems are available in 50- to 300-kvar single phase units suitable for pole mounting in banks of 3 to 12 units. Capacitors should be connected to the system through fuses so that a capacitor failure will not jeopardize system reliability or result in violent case rupture. When voltage ratings limit a single unit, engineers connect capacitors in series to distribute stress effectively.

Effect of Shunt Capacitors on Voltage

Proposed permanently connected capacitor applications should be checked to make sure that the voltage to some customers will not rise too high during light-load periods. Switched capacitor applications should be checked to determine that switching the capacitor bank on or off will not cause objectionable flicker in electronics. Selecting appropriate sizes in the standard unit of capacitance helps manage voltage rise and flicker.

Effect of Shunt Capacitors on Losses

The maximum loss reduction on a feeder with distributed load is obtained by locating positively negatively capacitor banks on the feeder where the capacitor kilovars is equal to twice the load kilovars beyond the point of installation. This principle holds whether one or more than one capacitor bank is applied to a feeder. To meet kvar targets with modular banks, utilities often add capacitance in parallel so reactive output scales predictably.

Capacitor kilovars up to 70% of the total kiovar load on the feeder can be applied as one bank with little sacrifice in the maximum feeder-loss discharge reduction possible with several capacitor banks.

A rule of thumb for locating a single capacitor bank on a feeder with uniformly distributed loads is that the maximum loss reduction can be obtained when the capacitor kilovars of the bank is equal to two-thirds of the kilovar load on the feeder. This bank should be located two-thirds of the distance out on the distributed feeder portion for object charging. Deviation of the capacitor bank location from the point of maximum loss reduction by as much as 10 per cent of the total feeder length does not appreciably affect the loss benefit. Therefore, in practice, in order to make the most out of the capacitor's loss reduction and voltage benefits, it is best to apply the capacitor bank just beyond the optimum loss-reduction location.

Batteries and capacitors seem similar as they both store and release electrical energy. However, there are crucial differences between them that impact their potential electronic applications due to how they function differently, depending on insulator material.

Supercapacitors

A capacitor battery aligns the molecules of a dielectric across an electric field to store energy. A supercapacitor aligns the charging of an electrolyte on either side of an insulator to store a double-layer charge.

Electrolytic capacitors consist of two or more conductive capacitors plate, separated by a dielectric. When an electric current enters the capacitor, the dielectric stops the flow and a charge builds up and is stored in an electric field between the metallic plates. Each capacitor is designed to have a particular capacitance (energy storage). When a capacitor is connected to an external circuit, a current will rapidly discharge. Plate area, separation, and dielectric constant together determine capacitance and thus energy density.

In a supercapacitor, there is no dielectric between conducting plates; rather, there is an electrolyte and a thin insulator such as cardboard or paper. When a current is introduced to the supercapacitor, ions build on either side of the insulator to generate a double layer of charge, no matter the capacitor charged. Supercapacitors are limited to low voltages, but very high capacitance frequencies, as a high voltage would break down the electrolyte. 

Batteries

There are different types of capacitor batteries, which detemine the capacitance of a capacitor. Different battery types are distinguished by their chemical makeup. The chemical unit, called the cell, contains three main parts; a positive terminal called the cathode, negative terminal called the anode, and the electrolyte. Batteries store electric energy. The battery charges and discharges through a chemical reaction that generates a voltage. The store of charge in the battery is able to provide a consistent DC voltage. In rechargeable batteries, the chemical energy that is converted into electricity can be reversed using an outside electrical energy to restore the charge of capacitors storing power in the batteries.

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