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SMART GRIDS

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Smart grids: what is a smart electrical grid – electricity networks in evolution

A smart grid is an electricity network/grid enabling a two-way flow of electricity and data whereby smart metering is often seen as a first step. Smart grids – as a concept – became known over a decade ago. An introduction with definitions, trends and essential characteristics of smart grids.

Big data and advanced analytics are essential technology drivers in smart grids whereby analytics shift to the edge, as in edge computing. Smart grids leverage more technologies but aren’t just about IT nor even technologies.

A smart grid is an electricity network enabling a two-way flow of electricity and data with digital communications technology enabling to detect, react and pro-act to changes in usage and multiple issues. Smart grids have self-healing capabilities and enable electricity customers to become active participants.

A smart grid serves several purposes and the movement from traditional electric grids to smart grids is driven by multiple factors, including the deregulation of the energy market, evolutions in metering, changes on the level of electricity production, decentralization (distributed energy), the advent of the involved ‘prosumer’, changing regulations, the rise of microgeneration and (isolated) microgrids, renewable energy mandates with more energy sources and new points where and purposes for which electricity is needed (e.g. electrical vehicle charging points).

An electrical grid or electric grid is a network to deliver electricity from the producer(s) and places where it’s generated and transformed (power plants and substations) to the final destinations where electricity is ‘consumed’: households, businesses, various facilities and the consumer in general.

In practice it is a highly interconnected network with several components such as substations, transmission lines and wiring, distribution lines, transformers and more.

Available at https://www.i-scoop.eu/industry-4-0/smart-grids-electrical-grid/. Acceso el 1 de octubre, 2020

Latest Trends In Smart Grid Technology In The Utilities Industry

REALICE LAS ACTIVIDADES QUE SE ENCUENTRAN AL FINAL DEL TEXTO

SMART GRID SYSTEM DELIVERING NEXT-GENERATION UTILITIES, KNOW HOW!

Global energy providers adopt modernized grids integrated with hardware and software innovations, to ensure a smarter, faster, and efficient solution for achieving the growing energy demand. Upgrading the current system it helps utilities and consumers to access the potential of a digital grid. Although the upgradation of the existing electrical grid infrastructures delivers significant output; industries are making strategic decisions and taking meaningful steps to create a next-generation workforce and a vibrant, thriving utility of the future.

• Future for the Energy Consumers

The energy consumers in the present world tend to have more information, choice, and control over virtual aspects of the energy supply chain. As renewable and distributed energy rapidly becomes the mainstream, the impact of deploying advanced technologies, automation, and innovations on the grid cannot be ignored. Benefit monitoring, health management, maintenance, and replacements are the results of data-driven decisions and predictions. Today, all the efforts to improve safety, efficiency, and better information enhance the reliability and save cost for the customers, delivering flexible, robust, agile grid to satisfying their new demands.

• Restructuring the Business Model

The utility business model increases the integration of load and generation at the distribution level. New technologies for communications and coordinated controls enable significant changes in grid operations, customer experiences, and empowerment. It helps to make the grid operations more efficient and reliable, enabling an environmentally friendly electric supply. A smart grid needs to facilitate the integration of distributed energy resources, minimize outages, and provide improved communications and response and cost-effectively availing real-time information and controls for consumer benefit.

• Up-grading the Energy Production System

With the changes in customer demands and requirements, while measuring the environment-friendly ways, energy providers and industries need the right training and tools to adapt and succeed in the energy revolution. The implementations of the innovations empower the employees to take risk and challenges to explore new solutions in the existing problems. It encourages the employees to learn, contribute, and stretch their capabilities and take a leadership role for challenging projects. There are tremendous opportunities and enormous potential for the industries to achieve new economies with a flexible, modern grid and customer-driven energy choices.

Utilities demand sets of technology components to take a holistic approach for grid modernization. The multiple grids and micro-grids system enables the management of energy from diverse power sources and leads to generate efficiency at a low cost of operation. Smart grids function as an advanced distribution management system availed from the real-time, analytical, and ancillary applications. Technologies like Internet of Things (IoT) devices and cloud-based data management platforms leverage analytics and facilitate IT/OT convergence. Smart grid systems promise a bright future for utilities by embracing the technologies in the right directions.

Available at https://medium.com/@mikethomsan/latest-trends-in-smart-grid-technology-in-the-utilities-industry-9e2f295d3a4f. Acceso el 2 de octubre, 2020.

Dielectric Strength

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 Dielectric Strength

Dielectric Strength reflects the electric strength of insulating materials at various power frequencies. Or it can be defined as the measure of dielectric breakdown resistance of a material under an applied voltage and is expressed as Volts per unit thickness. It is an indicator of how good an insulator a material is.

In other words, it is the voltage per unit thickness at which a material will conduct electricity. The higher the value, the more electrically insulating a material is.

It is an important property sought for materials used in applications where electrical field is present and is a vital parameter for electrical industry applications.

Applications include:

  » Development of materials for energy storage applications

  » Dielectric materials for capacitors

  » Thin films in high speed digital circuitry

The dielectric strength depends on:

  » The type of the plastic and electrodes

  » The shape of the plastic and electrodes

  » The rate with which the field is increased, and

  » The medium that surrounds the insulator

How to Measure Dielectric Strength?

The most generally used standard tests to calculate dielectric strength are ASTM D149 or IEC 60243-1 (ofcourse there exist several other methods as well, but they are not discussed here).

The measurement of dielectric strength is usually carried out either by the:

  »  Short-time method

  »  Slow rate-of-rise method

  »  Step-by-Step method

Short-time method

In this method, the voltage is applied across the two electrodes and increased continuously at a uniform rate (500 V/sec) until the breakdown occurs. Breakdown is defined as when an electrical burn- through punctures the sample or decomposition occurs in the sample.

Slow rate-of-rise method

In this test method, the voltage is applied to the test electrodes from the starting voltage 50% of the breakdown voltage until breakdown occurs.

Step-by-Step method

The voltage is applied to the test electrodes at the preferred starting voltage in steps and duration until breakdown occurs.

Specimen Size - The recommended specimen type is a 4 inch plaque or larger. Any specimen thickness can be used.

Dielectric strength is calculated by dividing the breakdown voltage by the thickness of the sample.

Most plastics have good dielectric strengths (in the order of 100 to 300 kV/cm).

Factors Affecting Dielectric Strength

• The dielectric strength of an insulation material usually decreases with increase in temperature 
  It is approximately inversely proportional to the absolute temperature. At the same time, it is equally important to note that below room temperature, dielectric strength is substantially independent of temperature change.


• Mechanical loading has a pronounced effect on dielectric strength
  Since, a mechanical stress may introduce internal flaws which serve as leakage paths, mechanical loaded insulators may show substantially reduced values of dielectric strength.


• Dielectric Strength of an insulating material is influenced by the fabrication details
  For example, flow lines in a compression molding or weld lines in an injection molding may serve as paths of least resistance of leakage currents, this reducing the dielectric strength. Even nearly invisible minute flaws in a plastics insulator may reduce the dielectric strength to one-third this normal value.

Available at https://omnexus.specialchem.com. Acceso el 9 de octubre, 2020.

Control and limitation of high short-circuit currents

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Control and limitation of high short-circuit currents

Nasser D. Tleis BSc, MSc, PhD, CEng, FIEE, in Power Systems Modelling and Fault Analysis, 2008

Example 9.3

Again, we will use the system and data of Figure 9.5. In addition, the ZPS system infeed at 400 kV is assumed equal to the PPS infeed. The autotransformers have unloaded, closed 13 kV delta-connected tertiary windings and their equivalent 400, 132 and 13 kV windings ZPS reactances on 240 MVA base are 19.2%, 0% and 24%, respectively. The generator-transformers' windings are star-delta connected and the ZPS reactance is 11% on 100 MVA. Calculate the single-phase short-circuit fault current at the solid 132 kV busbar under the following conditions:

(a)

Normal condition with autotransformer's delta windings closed.

(b)

Autotransformers's delta windings are opened. The core construction is 3-limb. The effective equivalent 400 kV, 132 kV and neutral reactances are –4%, 12% and 100% on 100 MVA base, respectively.

Delta windings closed

From Example 9.1, the PPS/NPS (negative phase sequence) Thévenin's equivalent impedance ‘seen’ at the fault point is equal to 0.0188 pu. Also, the ZPS Thévenin's equivalent impedance ‘seen’ at the fault point is calculated as

As expected, in this example, the single-phase fault current is 20% higher than the three-phase fault current.

Delta windings opened

The opening of the autotransformer delta windings for 3-limb cores would produce changes in the ZPS equivalent reactances of the autotransformers, as discussed in Chapter 4. The Thévenin's PPS/NPS reactance is unchanged and is equal to 0.0188 pu. The ZPS Thévenin's equivalent impedance ‘seen’ at the fault point is amenable for hand calculation but requires one simple star-to-delta transformation. It is easily shown that 

32×0.0188+0.0324×100MVA3×132kV=18.7kA

It is interesting to note that although opening the delta windings increases the ZPS Thévenin's impedance by a factor of 0.0324/0.00895 = 3.6, the single-phase fault current is reduced by 33% which in this example is quite significant.

Where the autotransformers are of 5-limb core or shell-type construction, then as we discussed in Chapter 4, the opening of the delta winding will cause the ZPS shunt neutral impedance to become very large. Values may range from 3000% to 5000% on 100 MVA base. The reader may wish to repeat the calculation of single-phase fault current for a 5-limb or shell-type autotransformer and compare with questions (a) and (b) above.

Available at https://www.sciencedirect.com/topics/engineering/autotransformers. Acceso el 4 de octubre, 2020.

ELECTRICITY GROUNDING Actividades

Understanding Electrical Grounding in Household Wiring 

Written by 

Timothy Thiele

Updated 10/20/19

Grounding is a principle of electricity that sometimes puzzles homeowners. In essence, the grounding system in a residential wiring system serves a "backup" pathway that provides an alternate route for electrical current to follow back to "ground" in the case of a problem in the wiring system. To understand its importance to a home wiring system, it is important to know something about the nature of electrical energy flow.

Some Electricity Basics

The electrical current in your home's wiring system consists of a flow of electrons within metal circuit wires. The current comes in two forms, a negative and a positive charge, and this charged electrical field is created by huge generators operated by the utility company, sometimes many hundreds of miles away. It is this polarized charge than effectively constitutes the flow of electrical current, and it arrives at your home through a vast network of high-tension service wires, substations, and transformers that blanket the landscape.

The negative half of the charge is the "hot" current. In your home's wiring system, the hot current is normally carried by black wires, while the neutral wires, which are white, carry the positive charge. Both sets of wires enter your home through the utility's main service wires, run through your electrical service panel, and run side-by-side through every circuit in your home.

The physics of electrical flow are more complicated than most simple explanations can convey, but essentially, electricity seeks to return its electrons to "ground"—that is, to discharge its negative energy and return to equilibrium. Normally, the current returns to ground through the neutral wires in the electrical system. But should some breakdown of the pathway occur, the hot current may instead flow through other materials, such as wood framing, metal pipes, or flammable materials in your home. This is what may happen in a short circuit situation, where most electrical fires and shocks originate. A short circuit is when electricity strays outside the wires it is supposed to flow through—in other words, when it takes a shorter path to ground.

Available at www.thespruce.com  (Acceso el 27 de junio, 2020)

LINEAR-NON LINEAR CIRCUITS Cuestionario

A) Responda el cuestionario con la información del texto.

1- ¿Con qué se construyen los dispositivos eléctricos?

2- ¿De qué habla en este artículo?

3- ¿Qué es un circuito lineal?

4- ¿Cuáles son sus parámetros?

5- ¿Qué es un circuito lineal?

B) El resto del texto será leído en clase.

What are Linear and Non-linear Circuits and Its Differences?

The electrical devices are built with the help of the linear and nonlinear components. To understand the basic design of these devices, the fundamental understanding of linear circuit and non-linear circuit are necessary. In this article, we are discussing what is a linear and non-linear circuits with its differences, elements of the linear & nonlinear circuit and some of the examples are explained.

What are Linear and Non-linear Circuits?

Simply we can say that the linear circuit is an electric circuit and the parameters of this circuit are resistance, capacitance, inductance and etc which are constant. Or we can say that the parameters of the circuits are not changed with respect to the voltage and current is called the linear circuit.

Linear Circuit

The non-linear circuit is also an electric circuit and the parameters of this circuit differ with respect to the current and the voltage. Or in the electric circuit, the parameters like waveforms, resistance, inductance and etc are not constant is called as non- linear circuit.

Non-Linear Circuit

Difference Between the Linear and Non-Linear circuit

Generally, the word linear means a straight line which looks like diagonal and it has linear characteristics between voltage and current. i.e  the current flow in the circuit is directly proportional to the voltage. If there is an increase in the voltage then the current flow in the circuit also increases and vice versa. The output characteristics of the linear circuit are between current and voltage of the figure is shown below.

Linear Circuit Characteristics

In a linear circuit, the response of the output is directly proportional to the input. In the circuit, the applied sinusoidal having the frequency “f” and the output means the voltage between the two points is also having the sinusoidal frequency “f”.

In the non-linear circuit, the output characteristic is like a curve line which in between the voltage and current as shown in the following figure.

The other difference between the linear and nonlinear circuit is solving the circuit. In the linear circuits, the solving of the circuit is a simple by using a simple technique, using a calculator to solve and by comparing with the non-linear circuit the linear circuit is easy to solve.

The solving of the non-linear circuits is complex than the linear circuit and there is a lot of data, information is required to solve the nonlinear circuits. Due to a lot of change in the technology, we can simulate and analyze the output curves of linear and nonlinear circuits with the help of the circuit simulation tools like Multisim, Matlab, and PSpice.

Available at https://www.elprocus.com/linear-and-non-linear-circuit-with-differences/ Acceso el 20 de mayo, 2020