TRANSMISSION LINES DESIGN and ELECTRICAL ENGINEERING HUB

The costs of electric power outages to American electric customers are generally called “socio-economic” costs.  Attempts have been made to quantify these costs but the estimates vary widely. One source reports that the costs are $26 billion each year and that they have been increasing as the electric power industry is restructured. A 2001 report1 from the Electric Power Research Institute (EPRI) states that power outages and problems with power quality cost the U.S. economy over $119 billion per year. Numerous impacts of power outages have been identified. Included among these impacts are: • Loss of life due to accidents (e.g., no street lights); • Loss of life of ill and elderly (death rates go up); • Loss of productivity by industry; • Loss of sales by business; • Loss of wages of labor; • Damage to equipment in industry; • Fires and explosions; • Riots and thefts; • Increased insurance rates.

One common method of measuring resistances ranging 0–1000 MΩ is by using meggers or insulation-resistance testers. This is the usual ohmmeter with a battery used for voltage source. This instrument is used to measure very high resistances, such as those found in cable insulations, between motor windings, in transformer windings, etc. Normal multimeters do not provide accurate indications above 10 MΩ because of the low voltage used in the ohmmeter circuit. Meggers can apply a high voltage to a circuit under test and this voltage causes a current if any electrical leakage exists. This makes it useful as an insulation tester. Some laboratory test meters have a built-in high-voltage source. The high voltage permits accurate high-resistance measurement, but such meters are usually not portable. The megger is essentially a portable ohmmeter with a built-in high-voltage source. The built-in high-voltage source may be derived from a magnet-type DC generator or battery. ...

While a person is conducting tests with an instrument on live line supply, there is a possibility of a sharp rise in voltage for a short duration. This may result in an arc or flash between measurement terminals of the testing device. In addition, if a heavy flash occurs, it may critically injure a person handling the instrument. To safeguard the person using the measuring instrument and to classify the various instruments as per the application they are used in, the IEC has classified instruments in the following categories: • Category IV: Distribution systems, service connections, and primary overcurrent protection for larger installations • Category III: Three-phase and single-phase distribution within a premises • Category II: Appliances, lighting points, socket-outlets • Category I: Transient-protected electronic equipment. The IEC Standard 61010 provides guidelines for manufacturers to follow safety norms for testing devices. It is to be noted that irr...

The CRO measuring instrument may sound very familiar, as it is a very useful device. It is used for measurement of voltages (AC/DC) and display of waveforms by providing information on time duration, frequency, and their shapes. Features of CRO Below are listed the various features of the CRO: • It allows voltage (AC/DC) amplitude measurement and time period measurement from the waveform displayed on screen. • Dual trace CRO allows the user to see two traces at a time on two different channels for comparison. • Two sets of controls provide the facility to show time period differences, amplitude differences, and shape/distortion comparison. • Storage oscilloscopes allow storage of waveforms for later analysis. • Storage facility is very useful since it provides a cursor function, which shows the value of a measured variable at a particular instance. Operating CRO To operate the CRO, perform the following procedure: • The power on switch is provided for on/off con...

A control circuit is for the automatic control of equipment, for safety interlocking, and sequencing the operations of the plant equipment and machines. Control circuits hardware consists of relay contacts, wires, hardware timers, and counters, relay coils, etc. These consist of input contacts representing various conditions; the output coils are energized or de-energized depending on the input conditions represented by the control circuit. Input contacts represent the binary state of the condition: • True or false • On or off. There are two types of contacts NO (normally open) and NC (normally closed). • Input contact: These are contacts of relays, contactors, timers, counter, field instrument switches, pressure switches, limit switches, etc. • Output coil: These have two states – On or Off. Output coil can be auxiliary contactor or Main contactor coil. A few simple control circuits are shown in figure below to represent logical AND, OR, and such conditions. ...

Electrical power is measured with a wattmeter. A wattmeter consists of a current coil connected in series with load, while the other potential coil is connected parallel with load. Depending on the strength of each magnetic field movement, the pointer gets affected. The true or real power is directly shown in a wattmeter. In three-phase systems, power can be measured using several methods. For temporary measurements, a single wattmeter can be used. However, for permanent measurements, a three-phase wattmeter having two elements is used which indicates both balanced and unbalanced loads. For an unbalanced load, two wattmeters must be used as shown in the below. The total power is calculated by adding the measurement readings given by the two wattmeters. With this method, the power factor can also be obtained. When using the two-wattmeter method, it is important to note that the reading of one wattmeter should be reversed if the power factor of the system is less th...

Battery Types Chemical batteries are individual cells filled with a conducting medium-electrolyte that, when connected together, form a battery. Multiple batteries connected together form a battery bank. At present, there are two main types of batteries: Primary batteries (non-rechargeable) Secondary batteries (rechargeable). Secondary batteries are further divided into two categories based on the operating temperature of the electrolyte. Ambient operating temperature batteries have either aqueous (flooded) or nonaqueous electrolytes. High operating temperature batteries (molten electrodes) have either solid or molten electrolytes. Batteries in EVs are the secondary-rechargeable-type and are in either of the two sub-categories. A battery for an EV must meet certain performance goals. These goals include quick discharge and recharge capability, long cycle life (the number of discharges before becoming unserviceable), low cost, recyclability, high specific energy (amo...

What is commonly defined as electricity is really just the movement of electrons. So, let’s start at that point. Current (I, Amps) Current (as the name implies) is the movement or flow of electrons (I) and is measured in units of Amperes. This is usually abbreviated to Amp or, even shorter, A. The flow of electrons in an electrical current can be considered the same as the flow of water molecules in a stream. To get anything to move requires potential and the same thing happens to electrons. Potential (V, Volts) Potential is the force (called Electromotive Force or EMF) that drives the electrons and has a measurement of voltage. This is abbreviated as a unit of measurement to Volt or even further to V. Resistance (R, Ohms) Resistance is the property that resists current flow. It is analogous to friction in mechanical systems. The unit of this is ohm (we have to give some credit to the fellow who first named it). It is sometimes shown with its official ohm m...

Semiconductors You know semiconductors as transistors, diodes, and chips. Silicon material is used to make devices that will conduct a certain amount of current when needed. These devices are made for easy use and with low voltages. You will encounter semiconductor chips in memory devices and computers; transistors are used in many types of circuits, and diodes are used as rectifiers and control devices. Diodes Diodes have an anode and a cathode. The cathode end is marked (+) to indicate which polarity it must be connected to in order to work properly. Diodes have many uses. They are found in circuits that are used to change ac to dc for certain control devices. They may also be used as protective devices in circuits. Transistors The transistor is used for switching and amplification. It consists of three active elements. There are two basic types of transistors, PNP and NPN. These terms will be discussed later. E stands for emitter, C stands for collector, an...

Delta connection (/_\) In a balanced circuit, when the generators are connected in delta, the voltage between any two lines is equal to that of a single phase.  The line voltage and the voltage across any winding are in phase, but the line current is 30° or 150° out of phase with the current in any of the other windings. In the delta-connected generator, the line current from any one of the windings is found by multiplying the phase current by the square root of 3, which is 1.73. Wye connection (Y) In the wye connection, the current in the line is in phase with the current in the winding. The voltage between any two lines is not equal to the voltage of a single phase, but is equal to the vector sum of the two windings between the lines. The current in line A of is the current flowing through the winding L1; that in line B is the current flowing through the winding L2; and the current flowing in line C is that of the winding L3. Therefore, the current in an...

Relays are a necessary part of many control and pilot-light circuits. They are similar in design to contactors, but are generally lighter in construction so they carry smaller currents. Compressors used for household refrigerators, freezers, dehumidifiers, vending machines, and water coolers have the capacitor-start, induction-run type of motor. This type of compressor may have a circuit that resembles below. When the compressor is turned on by the thermostat demanding action, the relay is closed and the start winding is in the circuit. Once the motor comes up to about 75% of rated speed, there is enough current flow through the relay coil to cause it to energize, and it pulls the contacts of the relay open, thereby taking the start capacitor and start winding out of the circuit. This allows the motor to run with one winding as designed. Below show the current type of relay. This is generally used with small refrigeration compressors up to 3/4 horsepower. ...

French physicist and physician, D’ Arsonval was a pioneer in electrotherapy, he studied the medical application of high-frequency currents. Among his inventions were dielectric heating and various measuring devices, including the thermocouple ammeter and moving-coil galvanometer. These measuring tools helped establish the science of electrical engineering. d’Arsonval’s galvanometer, which he invented in 1882 for measuring weak electric currents, became the basis for almost all panel-type pointer meters. He was also involved in the industrial application of electricity. Jaques-Arsene d’Arsonval was born on June 8, 1851 at the Pigsty, canton Saint-Germain-les-Belles, in his family house of “Borie” known from 14th century. His family had very old and noble roots. Nine children were born in the family, but only two of them including Arsene survived. Arsene d’Arsonval has studied in the Imperial College of Limoges (now LycEe Gay-Lussac). After the Franco-Prussian war of 1870 ...

Six general types of capacitors are the most widely used: 1. Air 2. Ceramic 3. Mica 4. Electrolytic 5. Paper 6. Tantalum The electrolytic capacitor is marked with + and - and has polarity that must be observed when it is connected in a circuit. The other types do not need a polarity marking. Below shows an electrolytic capacitor that may be found in air conditioning, refrigeration, and heating applications. It is used as ac motor run and start capacitors below:   Air capacitors. Air capacitors have air for a dielectric. They are usually variable capacitors used in the tuning circuits of radios. Mica capacitors. Aluminum foil is used as the plate material in mica capacitors. Between the aluminum foil plates is a thin sheet of mica. Sometimes the mica is sprayed with a conducting paint. The paint then forms the plate on one side of the mica. Mica capacitors are usually sealed in Bakelite or some type of plastic. Paper capacitors. Aluminum is al...

The d’Arsonval meter movement has a small, rectangular coil of wire. The coil is suspended in a magnetic field created by a permanent magnet. When current is applied to the coil, it becomes an electromagnet. The energized coil then lines up with the poles of the permanent magnet. The amount of current applied to the coil controls its movement. An electromagnet that is free to move will align its axis with the magnetic axis of a fixed magnet. The coil must be free to rotate in order to align itself with the magnetic axis. The coil in the meter is mounted on pivots that permit easy rotation. Two small springs are mounted on the top and bottom. These springs offer slight resistance to the rotation of the coil. The springs control the position of the coil when there is no current flowing. When current flows in the coil, it produces a magnetic field around the coil. This magnetic flux overcomes the force of the springs and moves the coil. A pointer on top of the coil rot...

Electricity is all around us. It moves the entire planet. Most, if not all activities significant to our lives involves electricity. The evolution of our world, corresponded with the advent of electricity. But how much do we know about electricity. More importantly, how much do we not know about electricity? Electricity is viewed as productive. Electricity is also viewed with amazement and danger by the others. Especially those who have less understanding. As electrical engineer, it is one of our responsibilities to educate people about electricity. This entry is a collection of the best article, and information in the web related to electricity. Basic information, myths, and misconception busters. ELECTRICITY BASIC DEFINITION Electricity, phenomenon associated with stationary or moving electric charges. Electric charge is a fundamental property of matter and is borne by elementary particles. In electricity the particle involved is the electron, which carries a charge desig...

Written by a highly regarded power industry expert, this comprehensive manual covers in full detail all aspects of electric power distribution systems, both as they exist today and as they are evolving toward the future. A new chapter examines the impact of the emergence of cogeneration and distributed generation on the power distribution network.  Topics include an overview of the process of electricity transmission and distribution, a thorough discussion of each component of the system - conductor supports, insulators and conductors, line equipment, substations, distribution circuits and more - as well as both overhead and underground construction considerations.  Improvements in both materials and methods of power distribution are also explored, including the trend toward gradual replacement of heavier porcelain insulators with lighter polymer ones. The complex aspects of electric power distribution are explained in easy-to-understand, non-technical language....

The following are recommended changes to the existing Over-Current Protection Pickup Guidelines: 1.        The minimum line to ground (LG) fault current will be calculated using a 10 Ohm fault impedance. 2.        The minimum phase fault current will be calculated using a 2 ohm fault impedance and will be the lesser of the phase to phase (LL) and a three phase (3p) fault. (2 ohms is the approximate arc impedance through air for our standard wire spacing) 3.        At a backup device (recloser or circuit breaker) we should strive (i.e. not mandatory) to detect a bolted fault at the end of the next device’s zone. This applies for both ground and phase settings. Distribution Circuit Breaker   Time Delay   Phase Pickup Minimum              = line ampacity or 2 x (maximum load current) which ever is the lowest ...

The incandescent lamp is a thermal radiator. The filament wire begins to glow when it is heated to a sufficiently high temperature by an electric current. As the temperature increases the spectrum of the radiated light shifts towards the shorter wavelength range – the red heat of the filament shifts to the warm white light of the incandescent lamp. Depending on lamp type and wattage the temperature of the filament can reach up to 3000 K, in the case of halogen lamps over 3000 K. Maximum radiation at these temperatures still lies in the infrared range, with the result that in comparison to the visible spectrum there is a high degree of thermal radiation and very little UV radiation. Lack of a suitable material for the filament means that it is not possible to increase the temperature further, which would increase the luminous efficacy and produce a cool white luminous colour. As is the case with all heated solid bodies – or the highly compressed gas produced by the sun – the inc...

The detailed procedure for insulation co-ordination set out in IEC 60071-1 (European standard EN60071 1 is identical) consists of the selection of a set of standard withstand voltages which characterize the insulation of the equipment of the system. This set of withstands correspond to each of the different stresses to which the system may be subject: • Continuous power frequency voltage (the highest voltage of the system for the life of the system). • Slow-front overvoltage (a standard switching impulse). • Fast-front overvoltage (a standard lightning impulse). • Very-fast-front overvoltage (depends on the characteristics of the connected apparatus). • Longitudinal overvoltage (a voltage between terminals combining a power frequency voltage at one end with a switching (or lightning) impulse at the other). These voltages and overvoltages need to be determined in amplitude, shape and duration by system study. For each class of overvoltage, the analysis then determines a ...

In order to match both the mechanical and electrical characteristics of the overhead line conductor to the environmental conditions climatic details must first be collected and analyzed. • Temperature The maximum, minimum and average ambient temperature influences conductor current rating and sag. For temperate conditions typically 20°C with 55°C temperature rise. For tropical conditions 35°C or 40°C with 40°C or 35°C temperature rise. Maximum conductor operating temperature should not exceed 75°C for bare conductors to prevent annealing of aluminium. Conductortemperatures up to 210°C are possible with ‘GAP’ conductor • Wind velocity Required for structure and conductor design. Electrical conductor ratings may be based on cross wind speeds of 0.5 m/s or longitudinal wind speeds of 1 m/s. • Solar radiation Required for conductor ratings but also for fittings such as composite insulators which may be affected by exposure to high thermal and ultraviolet (UV) radiation. T...

The machine is provided with an enclosure to give physical protection from external sources of motor damage. The following standard enclosures have been adopted by NEMA: • Open enclosure: An enclosure with ventilating openings that permits passage of external cooling air over and around the windings of the machine. • Drip-proof enclosure: An open enclosure in which ventilating openings are so constructed that successful operating is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle from 0° to 15° downward from the vertical. • Splash-proof enclosure: An open enclosure in which ventilating openings are constructed so that successful operation is not interfered with when drops of liquid or solid particles strike or enter the enclosure at any angle not greater than 100° downward from the vertical. • Guarded enclosure: An open enclosure in which all openings giving direct access to live metal or rotating parts are limited ...