Tips on Electrical Engineer training

Tips on electrical engineer training are quite simple to use and follow. Electrical engineering is quite a demanding career. Those who choose that profession never stop learning. Technology is always being made better so there is continually something new to read about, research or design. The training involved with the electrical engineer profession is one that is not just about reading a textbook. These jobs use computers and technology that has to be used in a hands on type environment.

The first of the tips for electrical engineering training is that a GED or high school diploma must be achieved first in order to start studying the field and all that it has to offer. Also having some electrical engineering experience can help, but most training programs start with the basics of the field and as they progress a specialty can be chosen and trained for. It is a great idea to learn all that you can about electrical engineering, as you never know where your career may take you.

Other tips for electrical engineer training is to read and research the field. This is the first step in understanding engineering, as you will be researching during your career. Having teachers explain the process and then have you use the technology will give you a better overall understanding. As you work with the technology you will grasp the concept and then be able to explain why or why not the design you choose did not work. A last tip is to choose a college or institution that fits your life and schedule rather that be a classroom setting or online courses that work with computers. Electrical engineering is on the cutting edge of technology and the best tip for future engineers is to study hard and never stop.

A few tips on the Electrical Engineer exam

There is a test known as the FE exam that must be passed in order to be able to work as an electrical engineer. The FE exam is also known as the Fundamentals of Engineering exam. There are a few tips on the electrical engineer exam that can help you pass and the top one is being knowledgeable about what the test involves. There are several parts to the exam and knowing what you are up against is better in the long run. That includes a variety of engineering topics such as environmental, mechanical, electrical, and a morning session with the basics like math and science.

There are always a few tips on the electrical engineer exam that can help one to become an engineer. Along with knowing what is covered on the test you must study and that is not just a one-time event either. Months before the exam takes place it is smart to review all types of engineering subjects that will be covered on the exam so that you are prepared in every way possible. In addition, even if you are sure that you know the topics review them one more time before the exam.

The FE exam is a vigorous type of test. A few tips on the Electrical Engineer exam include one major one, which is - you should be well rested and ready to go for the long haul. This exam includes seven main categories plus sub categories. This exam has a morning and an afternoon session. There is 8 hours allotted for those taking for completion. For those dedicated to technology and electrical engineering this exam is necessary. It must be studied for hard so that in the end a new electrical engineer can be introduced into the workplace.

OVERCURRENT PROTECTION PICK UP GUIDELINES EXAMPLE

Over-Current Protection Pickup Guidelines

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

Maximum = 1 phase (EOZ) 2 ohm (the lesser of the phase to phase and three phase fault, at the End OF ZONE, through a two Ohm impedance)

Max. Backup = 1-LL (ENZ) (the bolted phase to phase fault, at the END of the Next Zone)

Ground Pickup

Minimum = 0.3-0.5 x (maximum load current) or 0.3-0.5 x (line ampacity) which ever is the lowest

Maximum = 1-LG (EOZ) 10 Ohm (the line to ground fault current, at the End Of Zone, through a ten Ohm impedance)

Max. Backup = 1-LG (ENZ - the bolted line to ground fault, at the End of th Next Zone)

Instantaneous

Phase Pickup

Minimum = 0.9 x 1-LL (EOZ)

Maximum = 1.25 x 3phase bus fault

Ground Pickup

Minimum = 0.9 x 1-LG (EOZ)

Maximum = 1.25 x 3phase bus fault

Recloser with Phase and Ground Settings

Phase Pickup

Minimum = 2 x (maximum load current)

Maximum = 1 phase (EOZ with 2 Ohm fault impedance)

Max. Backup = 1-LL (ENZ)

Ground Pickup

Minimum = 0.5 x (maximum load current)

Maximum = 1-LG (EOZ with 10 Ohm fault impedance)

Max Backup = 1-LG (ENZ)

Recloser with only Phase Settings

Phase Pickup

Minimum = 2 x (maximum load current)

Maximum = 1-LG (EOZ with 10 Ohm fault impedance)

Max. Backup = 1-LG (ENZ)

The value of a (10) ten ohm ground fault impedance was initially chosen because it appeared to be the most prevalent in the industry from what could be determined. It is recognized that fault impedance from zero to forty Ohms are in use. The (10) ten ohm value gained legitimacy after reviewing EPRI Report EL-3085, Distribution Fault Current Analysis. This report indicates that 83% of faults involved the neutral or ground. The maximum fault impedance was calculated to be 3 Ohms.

As stated earlier, the value of a (2) two ohm phase fault impedance was chosen because it is the approximate arc impedance through air for our standard wire spacing.

HALOGEN LAMPS INFORMATION

Halogen Lamps

It is not so much the melting point of the tungsten (which, at 3653 K, is still a relatively long way from the approx. 2800 K of the operating temperature of incandescents) that hinders the construction of more efficient incandescent lamps, but rather the increasing rate of evaporation of the filament that accompanies the increase in temperature.

This initially leads to lower performance due to the blackening of the surrounding glass bulb until finally the filament burns through. The price to be paid for an increase in luminous efficiency is therefore a shorter lamp life.

One technical way of preventing the blackening of the glass is the adding of halogens to the gas mixture inside the lamp. The evaporated tungsten combines with the halogen to form a metal halide, which takes on the form of a gas at the temperature in the outer section of the lamp and can therefore leave no deposits on the glass bulb.

The metal halide is split into tungsten and halogen once again at the considerably hotter filament and the tungsten is then returned to the coil. The temperature of the outer glass envelope has to be over 250° C to allow the development of the halogen cycle to take place.

In order to achieve this compact bulb of quartz glass is fitted tightly over the filament. This compact form not only means an increase in temperature, but also an increase in gas pressure, which in turn reduces the evaporation rate of the tungsten.

Compared with the conventional incandescent the halogen lamp gives a whiter light – a result of its higher operating temperature of 3000 to 3300 K; its luminous colour is still in the warm white range. The continuous spectrum produces excellent colour rendering properties.

The compact form of the halogen lamp makes it ideal as a point-source lamp; its light can be handled easily and it can create attractive sparkling effects. The luminous efficacy of halogen lamps is well above that of conventional incandescents – especially in the low-voltage range.

Halogen lamps may have a dichroic, heat reflecting coating inside the bulbs, which increases the luminous efficacy of these lamps considerably. The lamp life of halogen lamps is longer than that of conventional incandescents.

Halogen lamps are dimmable. Like conventional incandescent lamps, they require no additional control gear; low voltage halogen lamps do have to be run on a transformer, however.

In the case of double-ended lamps, projector lamps and special purpose lamps for studios the burning position is frequently restricted.

Some tungsten halogen lamps have to be operated with a protective glass cover.

WORLD'S PROFESSIONAL ORGANIZATIONS FOR ELECTRICAL ENGINEERING

Many professional organizations are involved in the functioning of the electric

power industry.

IEEE

“The Institute of Electrical and Electronics Engineers, Inc. (IEEE) is a nonprofit, technical professional association of more than 377,000 individual members in 150 countries.

Through its members, the IEEE is a leading authority in technical areas ranging from computer engineering, biomedical technology, and telecommunications, to electric power, aerospace, and consumer electronics, among others. The IEEE is made up of:

• 10 regions;

• 37 societies;

• 4 councils;

• Approximately 1,200 individual and joint society chapters;

• 300 sections; and

• 1,000 student branches are located at colleges and universities worldwide.”

The Power Engineering Society is one of the 37 societies in the IEEE and has 25,000 members.

“Through its technical publishing, conferences, and consensus-based standards activities, the IEEE:

• Produces 30 percent of the world’s published literature in electrical engineering, computers, and control technology;

• Holds annually more than 300 major conferences; and

• Has nearly 900 active standards with 700 under development.”

“Policy matters related to IEEE Standards are the purview of the IEEE Standards Association (IEEE-SA), which establishes and dictates rules for preparation and approval . . .

Overwhelmingly, it is the Computer Society and the Power Engineering Society that dominate in this regard, for instance, about 40% of all IEEE Standards are . . . within the PES.”

CIGRE

Another important organization is the International Council on Large High Voltage Electric Systems (CIGRE). CIGRE is an international organization through which ideas can be exchanged with people from various countries through meetings, committee activities, and its publications.

TYPE OF USE OF POWER GENERATING PLANT

Generating units may be classified into three categories based on their mode of operation. These are:

1. Base Load;

2. Intermediate;

3. Peaking.

Base load units tend to be large units with low operating costs. They are generally operated at full capacity during most of the hours that they are available.

They are designed to operate for long periods of time at or near their maximum dependable capability. Their low operating costs result from their use of low-cost nuclear and coal fuels and/or lower heat rates (higher efficiencies) than other units on the system.

For a typical region, base load is on the order of 40% to 60% of the annual maximum hourly load and, since this represents the amount of load that will be supplied in the region at essentially all hours, it represents perhaps 60% to 70% of the annual energy requirements of the region.

Base load units are usually shut down for forced outages or maintenance only. Because of their size and complexity, these units may require from 24 hours to several days to be restarted from a “cold” condition.

Once the decision has been made to shut down one of these units, periods of up to 24 hours may be required before another “start-up” may be attempted. When operating a power system decisions on the time of restarting units play an important role in hour-by-hour schedules for generation.

Intermediate units are those generating units which are used to respond to the variations in customer demand which occur during the day. They are designed to withstand repeated heating and cooling cycles caused by changes in output levels.

Intermediate units usually have lower capital costs, and somewhat higher heat rates (lower efficiencies) than base load units. The intermediate load may be on the order of 30–50% of the maximum hourly load for a typical system and represents perhaps 20–30% of the annual energy requirements for the utility.

Peaking units are those generating units that are called upon to supply customer demand for electricity only during the peak load hours of a given period (day, month, year). Combustion turbines, reciprocating engines and small hydroelectric units comprise the majority of peaking units.

These are ordinarily units with a low maximum capability (usually less than 150Mw), which are capable of achieving full load operation from a cold condition within ten minutes. Peaking units usually have the highest heat rate sand lowest capital costs of the three categories of units.

In addition to supplying system needs during peak load hours, they may be called upon to replace the capability of other base load or cycling units which have been suddenly removed from service due to forced outages. They generally supply about 5% of the total energy requirements of a system.

As generating units age, unit efficiency and performance generally decrease. In addition, newer, more efficient, lower operating cost units are continuously added to a power system. These two occurrences tend to cause most generating units to be operated fewer hours as they age.

ELECTRICAL ENGINEERING TERMS AND DEFINITION

BASIC ELECTRICAL TERMS

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 mark (Ω) and the short form of the word resistance is always R.

Resistance not only depends on the material used for the conductor but also upon size and temperature. Increase in the cross-sectional area will decrease the resistance Increase in the length will increase the resistance. Increase in the temperature will increase the resistance (for most materials that conduct electricity)

Capacitance (C, Farads)

Any two conductors separated by an insulating material form a capacitor or condenser. Capacitance of a device is its capacity to hold electrons or a charge. The units of measurement are farads. We commonly see it in smaller amounts called microfarads μF and picofarads pF. Capacitance depends on the construction.

Magnetic Flux (Unit of Measurement is Webers)

When current flows in a conductor, a magnetic field is created around that conductor. This field is commonly presented as lines of magnetic force and magnetic flux refers to the term of measurement of the magnetic flow within the field.

This is comparable to the term current and electron flow in an electric field. The following illustration shows the direction of magnetic flux around a conductor and the application of the easily remembered right-hand-rule. Mentally, place your right hand around the conductor with the thumb pointing in the direction of current flow and the fingers will curl in the direction of magnetic flux.

Magnetic Lines of Force (MMF)

Lines of magnetic force (MMF) have an effect on adjacent conductors and even itself. This effect is most pronounced if the conductor overlaps itself as in the shape of a coil.

Magnetic Self-Inductance

Any current-carrying conductor that is coiled in this fashion forms an Inductor, named by the way it induces current flow in itself (selfinductance) or in other conductors.

Inductance (L, Henrys)

Opposition to current flowing through an inductor is inductance. This is a circuit property just as resistance is for a resistor. The inductance is in opposition to any change in the current flow. The unit of inductance is Henry (H) and the symbol is L.

Frequency (f, Hertz)

Any electrical system can be placed in one of two categories direct current (dc) or alternating current (dc). In dc systems the current only flows in one direction.

The source of energy maintains a constant electromotive force, as typical with a battery. The majority of electrical systems are ac.

Frequency is the rate of alternating the direction of current flow. The short form is f and units are cycles per second or Hertz (short-formed to Hz).

Reactance (X, Ohms)

The opposition to alternating current (ac) flow in capacitors and inductors is known as reactance. The symbol for capacitive reactance is XC and for inductive reactance XL.

Although we will not go into the derivation of the values, it can be shown that when f is the frequency of the ac current:

XL= 2 Πf L

XC=1/2ΠfC

Impedance (Z, Ohms)

The total opposition or combined impeding effect of resistance plus reactance to the flow of alternating current is impedance. The word impedance is short formed to Z and the unit is ohms.

Active Power (P Watts)

Instead of working directly with the term electrical energy, it is normal practice to use the rate at which energy is utilized during a certain time period. This is defined as power. There are three components of power: active, reactive and apparent.

Active power or real power is the rate at which energy is consumed resulting in useful work being done. For example, when current flows through a resistance, heat is given off. It is given the symbol P and has the units of Watts.

Reactive Power (Q, Vars)

Reactive power is the power produced by current flowing through reactive elements, whether inductance or capacitance. It is given the representative letter Q and has the units volt-amp-reactive (VAR).

Reactive power can also be considered as the rate of exchange of energy between a capacitor or inductor load and a generator or between capacitors and inductors.

Although it does not produce any real work, it is the necessary force acting in generators, motors and transformers. Examples of this are the charging/discharging of a capacitor or coil. Although this creates a transfer of energy, it does not consume or use power as a resistor would.

Apparent Power (U, Volt Amps)

Apparent power is the total or combined power produced by current flowing through any combination of passive and reactive elements. It is given the representative letter U and has the units’ volt-amps (VA).

Power Factor (PF)

Real power/ apparent power

Power Factor is the comparison of Real power to apparent power.

• For a resistor, there is no reactive power consumed. Thus apparent power used is totally real. The power factor would be 1 or often referred to as unity power factor

• For a pure inductor or capacitor, the apparent power consumed is entirely reactive (real power is nil). The power factor would then be 0.

• For power consumed by impedance consisting of resistance, inductance and capacitance the power factor will of course vary between these two limits. The most efficient use or consumption of power is obtained as we approach unity power factor.

TRANSFORMER COOLING SYSTEM SELECTION INFORMATION

Choosing the most appropriate method of cooling for a particular application is a common problem in transformer specification. No clear rules can be given, but the following guidance for mineral oil-immersed transformers may help. The basic questions to consider are as follows:

1. Is capital cost a prime consideration?

2. Are maintenance procedures satisfactory?

3. Will the transformer be used on its own or in parallel with other units?

4. Is physical size critical?

ONAN

This type of cooling has no mechanical moving parts and therefore requires little, if any, maintenance. Many developing countries prefer this type because of reliability, but there is an increasing cost penalty as sizes increase.

ONAF

A transformer supplied with fans fitted to the radiators will have a rating, with fans in operation, of probably between 15% and 33% greater than with the fans not in operation. The transformer therefore has an effective dual rating under ONAN and ONAF conditions.

The transformer might be specified as 20/25MVA ONAN/ONAF. The increased output under ONAF conditions is reliably and cheaply obtained.

Applying an ONAN/ONAF transformer in a situation where the ONAF rating is required most of the time is undesirable since reliance is placed on fan operation. Where a ‘firm’ supply is derived from two transformers operating in parallel on a load-sharing basis the normal load is well inside the ONAN rating and the fans would only run in the rare event of one transformer being out of service.

Such an application would exploit the cost saving of the ONAF design without placing too much emphasis on the reliable operation of the fans. Note that fans create noise and additional noise mitigating precautions may be needed in environmentally sensitive areas.

OFAF

Forcing the oil circulation and blowing air over the radiators will normally achieve a smaller, cheaper transformer than either ONAF or ONAN. Generally speaking, the larger the rating required the greater the benefits.

However, the maintenance burden is increased owing to the oil pumps, motors and radiator fans required. Application in attended sites, with good maintenance procedures, is generally satisfactory. Generator transformers and power station interbus transformers will often use OFAF cooling.

ODAF/ODWF

These are specialized cooling categories where the oil is ‘directed’ by pumps into the closest proximity possible to the winding conductors. The external cooling medium can be air or water.

Because of the design, operation of the oil pumps, cooling fans, or water pumps is crucial to the rating obtainable and such transformers may have rather poor naturally cooled (ONAN) ratings. Such directed and forced cooling results in a compact and economical design suitable for use in well-maintained environments.

ELECTRIC VEHICLE BATTERIES BASIC INFORMATION

Road vehicles emit significant air-borne pollution, including 18% of America’s suspended particulates, 27% of the volatile organic compounds, 28% of Pb, 32% of nitrogen oxides, and 62% of CO. Vehicles also release 25% of America’s energy-related CO2, the principle greenhouse gas. World pollution numbers continue to grow even more rapidly as millions of people gain access to public and personal transportation.

Electrification of our energy economy and the rise of automotive transportation are two of the most significant technological revolutions of the twentieth century. Exemplifying this massive change in the lifestyle due to growth in fossil energy supplies.

From negligible energy markets in the 1900, electrical generation now accounts for 34% of the primary energy consumption in the United States, while transportation consumes 27% of the energy supply. Increased fossil fuel use has financed energy expansions: coal and natural gas provide more than 65% of the energy used to generate the nation’s electricity, while refined crude oil fuels virtually all the 250 million vehicles now cruising the U.S. roadways. Renewable energy, however, provides less than 2% of the energy used in either market.

The electricity and transportation energy revolution of the 1900s has affected several different and large non-overlapping markets. Electricity is used extensively in the commercial, industrial and residential sectors, but it barely supplies an iota of energy to the transportation markets. On the other hand oil contributes only 3% of the energy input for electricity.

Oil usage for the purpose of transportation contributes to merely 3% of the energy input for electricity. Oil use for transportation is large and growing. More than two-thirds of the oil consumption in the United States is used for transportation purposes, mostly for cars, trucks, and buses.

With aircraft attributing to 14% of the oil consumption, ships and locomotives consume the remaining 5%. Since the United States relies on oil imports, the oil use for transportation sector has surpassed total domestic oil production every year since 1986.

The present rate of reliance and consumption of fossil fuels for electrification or transportation is 100,000 times faster than the rate at which they are being created by natural forces. As the readily exploited fuels continue to be consumed, the fossil fuels are becoming more costly and difficult to extract.

In order to transform the demands on the development of energy systems based on renewable resources, it is important to find an alternative to fossil fuels. Little progress has been made in using electricity generated from a centralized power grid for transportation purposes. In 1900, the number of electric cars outnumbered the gasoline cars by almost a factor of two.

In addition to being less polluting, the electric cars in 1900 were silent machines. As favorites of the

urban social elite, the electric cars were the cars of choice as they did not require the difficult and rather dangerous handcrank starters. This led to the development of electric vehicles (EVs) by more than 100EV manufacturers.

However, the weight of these vehicles, long recharging time, and poor durability of electric barriers reduced the ability of electric cars to gain a long-term market presence. One pound of gasoline contained a chemical energy equivalent of 100 pounds of Pb-acid batteries.

Refueling the car with gasoline required only minutes, supplies of gasoline seemed to be limitless, and the long distance delivery of goods and passengers was relatively cheap and easy. This led to the virtual disappearance of electric cars by 1920.

POWER SYSTEM FACILITY SAFETY SYSTEM TUTORIALS

Safety systems protect life and property from damage or loss due to accidents. For equipment, the degree of protection should be based on the value and criticality of the facility.

Personnel safety is covered rigorously in the NEC and many other standards. Defining this degree requires an in-depth knowledge of the installation and its function.

The following questions should be considered when designing these systems:

a) How long will it take to replace the equipment and at what cost?

b) Can the function of the facility be performed elsewhere?

c) Loss of what key component would result in operation interruptions?

Safety systems can be as simple as a manually operated emergency power-off button, or as complex as a fully interlocked system. However, the more complex a fully integrated system becomes, the higher the probability of system confusion or failure.

Typical systems include the following functions:

— Smoke and fire protection

— Environmental control

— Smoke exhaust

— Fire extinguishing

— Emergency lighting

— Security

The interfacing of a safety system is generally unique for each installation and requires a logical design approach. Through a well-defined logic matrix and sequence priorities, it is possible to develop a system that can be maintained, modified, or expanded with little confusion and minimum expense.

Generally, safety systems operate from 120 V ac, 24 V ac, or 24 V and 12 V dc. In any case, these systems must remain powered at all times. The quality of the power supplied to these systems is as important as that of the power delivered to the IT system.

Disturbances in the power supply of the safety system can cause shutdown of the protected system.

ELECTRICAL FORMULAS FOR POWER CABLE

Power Cable Capacitance (C) Formula

Single Conductor Shielded Cable

C = 0.024113 x e/ [log (d2/d1)] microfarad/ kilometer

where:

e = dielectric constant for XLPE = 2.3, PVC = 5.0-7.0

d2 = diameter under insulation

d1 = diameter over the insulation

Power Cable Insulation Resistance (IR) Formula

According to ICEA Specification

IR @ 15.6 degrees C = K log (d2/d1) Megaohm - 1000ft

According to JIS Specification

IR @ 20.0 degrees C = 3.665 x 10^-12 x p x log (d2/d1) Megaohm - km

where:

d2 = diameter under insulation

d1 = diameter over the insulation

K = constant (XLPE = 20,000; PVC = 500)

p = volume density (ohm-cm) ; XLPE = 2.5 x 10^15, PVC = 1 x 10^13

Power Cable Inductance (L) Formula

Multiple conductor cable or single conductor cable arranged in parallel and three single conductor arranged in triangular

L = 0.46 log (S/d) + 0.19 mH/km

where:

d = diameter of conductor

S = distance between conductor

Power Cable Charging Current (Ic) Formula

Ic = 2 x pi x fC x v/ 1.73 Amp/km

where:

C = capacitance (F/km)

V = rated line to line voltage (Volt)

f = frequency (Hz)

Power Cable Potential Gradient Formula

E = (v/1.73)/ X ln (d2/d1) kV/mm

where:

X = distance from center of the conductor (mm)

V = rated line to line voltage

d2 = diameter under insulation

d1 = diameter over the insulation

Fault Withstand Capability of Transmission Line Conductors

When a line (Transmission and / or Distribution) short circuit, very large currents can flow for a short time or up until a fuse, breaker or any isolation breaks the circuit. One important aspect of protecting the line from overcurrent and fault is to ensure that the fault arc and fault currents do not cause further, possibly more permanent, damage. The two main considerations are:

Conductor Annealing.

From the substation to the fault location, all conductors in the fault current path must withstand the heat generated by the short circuit current. If the relaying of fuse does not clear the fault in time, the conductor anneals and loses strength.

During high currents from faults, conductor can withstand significant temperatures for few seconds without losing strength. For all aluminum conductors (AAC), assuming temperature of 340®C is common. ACSR conductors can withstand even higher temperatures since short duration high temperature does not affect the steel core. You may assume a limit of 645®C melting temperature for Aluminum in ACSR.

Considering the heat inputs and conductor characteristics, the conductor temperature during a fault is related to the current as:

(I/1000A)² t = K log₁₀ [(T2+ƛ)/(T1+ ƛ)]

Where:

I = fault current (A)

t = fault duration (sec)

A = cross sectional area of conductor (kcMil)

T2 = conductor temperature from the fault

T1 =conductor temperature before the fault

K = constant

ƛ = inferred temperature of zero resistance

Conductor Material	ƛ, ®C	K
Copper (97%)	234.0	0.0289
Aluminum (61.2%)	228.1	0.0126
6201 (52.5%)	228.1	0.0107
Steel	180.0	0.00327

If we set conductors to their maximum temperature and at an ambient temperature of 40® C, these will be their characteristic curves:

AAC

I²t = (67.1A)²

ACSR

I²t = (86.2A)²

Covered conductors have more limited short circuit capability due to its insulation, as they are easily damaged even at relatively lower temperature.

Polyethelene

I²t = (43A)²

XLPE

I²t = (56A)²

Conductor Burndowns.

Right at the fault location, the hot fault arc can burn the conductor. If a circuit interrupter does not clear the fault in time, the arc will melt the conductor until it breaks apart.

Fault currents can damage overhead conductors. The arc itself generates tremendous heat, and where an arc attaches to a conductor, it can weaken or burn the conductor strands. On a distribution and transmission circuit, two areas stand out:

1. Covered Conductors. Covered conductors hold an arc stationary. Arc cannot move, burndowns happen faster than bare. The covering prevents the arc from moving.
2. Small Bare Wires. Small bare wires (less than 2/0) are also susceptible to wire burndowns, especially if laterals are not fused.

Conductor damage is a function of the duration of the fault and the current magnitude. Burndown damage occurs more quickly than conductor annealing.

BASIC ELECTRICAL ENGINEERING FORMULA

Electronics is an engineering discipline that involves the design and analysis of electronic circuits. Originally, this subject was referred to as radio engineering. An electronic circuit is a collection of components through which electrical current can flow or which use electromagnetic fields in their operation.

The electronic circuit design and analysis rests primarily on two Kirchoff's laws in conjunction with Ohm's law modified for AC circuits and power relationships. There are also a number of network theorems and methods (such as Thevenin, Norton, Superposition, Y-Delta transform) that are consequences of these three laws.

In order to simplify calculations in AC circuits, sinusoidal voltage and current are usually represented as complex-valued functions called phasors. Practical circuit design and analysis also requires a comprehensive understanding of semiconductor devices, integrated circuits and magnetics.

I = current(amps.), V = voltage(volts), R = resistance(ohms), P = power(watts)

CURRENT:

I = V/R or I = P/V

VOLTAGE:

V= P/I or V = IR

POWER:

I2R or VI

RESISTANCE:

R = V/I

ALTERNATING CURRENT(AC):

Il = line current(amps.), Ip = phase current(amps.), Vp = phase voltage(volts), Vl = line voltage(volts), Z = impedance(ohms), P = power(watts), f = power factor(angle), VA = volt ampers

CURRENT(single phase):

I = P/(Vp cos(f)

Common electrical units used in formulas and equations are:

Volt - unit of electrical potential or motive force - potential is required to send one ampere of current through one ohm of resistance

Ohm - unit of resistance - one ohm is the resistance offered to the passage of one ampere when impelled by one volt

Ampere - units of current - one ampere is the current which one volt can send through a resistance of one ohm

Watt - unit of electrical energy or power - one watt is the product of one ampere and one volt - one ampere of current flowing under the force of one volt gives one watt of energy

Volt Ampere - product of volts and amperes as shown by a voltmeter and ammeter - in direct current systems the volt ampere is the same as watts or the energy delivered - in alternating current systems - the volts and amperes may or may not be 100% synchronous - when synchronous the volt amperes equals the watts on a wattmeter - when not synchronous volt amperes exceed watts - reactive power

Kilovolt Ampere - one kilovolt ampere - KVA - is equal to 1,000 volt amperes

Power Factor - ratio of watts to volt amperes

Electric Power Formulas

W = E I (1a)

W = R I2 (1b)

W = E2/ R (1c)

where

W = power (Watts)

E = voltage (Volts)

I = current (Amperes)

R = resistance (Ohms)

Electric Current Formulas

I = E / R (2a)

I = W / E (2b)

I = (W / R)1/2 (2c)

Electric Resistance Formulas

R = E / I (3a)

R = E2/ W (3b)

R = W / I2 (3c)

Electrical Potential Formulas - Ohms Law

Ohms law can be expressed as:

E = R I (4a)

E = W / I (4b)

E = (W R)1/2 (4c)

Example - Ohm's law

A 12 volt battery supplies power to a resistance of 18 ohms.

I = (12 Volts) / (18 ohms)

= 0.67 Ampere

Electrical Motor Formulas

Electrical Motor Efficiency

μ = 746 Php / Winput (5)

where

μ = efficiency

Php = output horsepower (hp)

Winput = input electrical power (Watts)

or alternatively

μ = 746 Php / (1.732 E I PF) (5b)

Electrical Motor - Power

W3-phase = (E I PF 1.732) / 1,000 (6)

where

W3-phase = electrical power 3-phase motor (kW)

PF = power factor electrical motor.

ADVANTAGES OF DIESEL ENGINE GENERATOR USE BASIC INFORMATION

The main advantages of using diesel driven electrical power generators are (not in rank order):

1. Performance. Diesel engines normally have high thermal efficiencies, in the region of 40% and higher, almost regardless of their size. Some current state-of-the-art engines can achieve efficiencies over 50%, and engine manufacturers have forecast efficiencies as high as 60% by the twenty-first century.

2. Maintenance. Diesels represent mature and well-developed technology and are comparatively easy to maintain on site without the need for fully skilled personnel except for certain nonroutine tasks.

3. Durability and Reliability. Diesels have long lifetimes in the range, on average, of at least 20 to 25 years, and they can operate 7000 to 8000 h per year and in some cases up to 12,000 h between regular major overhauls.

4. Fuel Efficiency. In most power-generation applications, diesels have the most competitive fuel consumption rates, and between half-load and full-load their fuel consumption rate is reasonably constant. Depending upon the application, size of engine, loading, and the operating environment, diesel engines normally have a specific fuel consumption in the range 160 to 360 g/kWh. The new Sulzer Diesel RTA two-stroke engines are claimed to be able to produce up to 35,431 kW (47,520 bhp) with a specific fuel consumption as low as 154 g/kWh (115 g/bhp).

5. Transportability. Diesel-generators can be transported on purpose-built trucks or in specially equipped containers by land, sea, or air so that they can be used immediately on arriving on-site even in remote areas. For their physical weight and size, they can generate large amounts of electrical energy, sufficient to supply a small town.

6. Cost. The cost per unit power installed is very competitive, but it must be emphasized that in costing diesel-power generation it is crucial to determine the total installed costs, not simply the capital cost of the engine and the generator. As a general rule of thumb, the speed of crankshaft rotation basically determines the weight, size, and cost of an engine in relation to its output power.

7. Operational Flexibility. Diesels can use a wide variety of fuel quality and can be designed to use both liquid and gaseous fuels; that is, they are ‘‘dual–fuel’’ engines. They can also be adopted for use in cogeneration and total-energy systems and in ‘‘non-air’’ environments.

8. Environmentally Compliant. Diesels inherently produce low amounts of harmful exhaust emissions. However, in recent years, engines have had to be redesigned and exhaust-emissions treatment systems upgraded to meet increasingly stringent regulations. It is certain that further advances in the efficacy of emission reduction techniques will be required for all fossil-fuel power systems in the future.

Advantages of Nuclear Power Plants - Big Hope in the Minute Atom

We know that power plants operating on thermal energy, water kinetic energy etc have several limitations in that they are dependent on availability of natural resources such as water, coal and so forth. These resources have a limited availability and also resources like water depend on seasonal variations of climate and therefore cannot be depended upon entirely. Hence nuclear energy provides an advantage over other sources of energy in such circumstances.

Introduction

The energy demands of the world are continuously increasing. Experts are worried about the future of power generation because there are not enough supplies of coal, water and gas to fulfill the needs of mankind in the long term future. Alternative sources of energy such as nuclear energy are being developed. Nuclear energy has several advantages over other sources of energy because it is not limited by space or location. In this article we will learn about nuclear power plants and some of the basic underlying concepts.

What is a Nuclear Power Plant?

As the name itself suggests, a nuclear power plant is a facility where nuclear energy is harnessed to generated electricity. For those of us who haven’t heard about this term, it may seem like a new concept since we usually hear of atomic and hydrogen bombs which use nuclear energy for large scale destruction. But the same power is used for constructive purposes in nuclear power plants

The basic underlying principle of a nuclear power plant can be understood from the equation of mass-energy equivalence which is stated as follows

E = ∆mc²

Where E is the amount of energy released when a change in mass occurs during a nuclear reaction. This equation may not seem very complicated to you, but as you know “c” represents the speed of light which is of the order of 3 lakh kilometers per second. Just imagine the amount of energy released even if a tiny amount of mass is converted into energy.

This gives an edge to nuclear power plants over conventional sources like coal or gas because it means freedom from geographical factors and parameters. Furthermore since the amount of fuel required is much less as compared to conventional sources of power generation, there is no need to have extensive storage facilities and transportation networks for the same amount of power generated.

Basic Nuclear Reactions

Nuclear reactions fall into two major categories: fission and fusion. Fission refers to the nuclear reaction where a heavy nucleus is broken into nuclei of intermediate atomic number. Fusion refers to the nuclear reaction wherein light nuclei get combined to form a new nucleus.

Energy can be either released or absorbed during the process depending on whether the final mass of the products is greater than or less than the initial mass of the reactants.

The Chain Reaction

The above mentioned types of reactions are not of much use for generating electrical energy on their own. We require something known as a controlled chain reaction if power is to be generated in a nuclear power plant. When fission is started in a nuclear material it could die out slowly, sustain itself constantly or develop into an uncontrolled reaction. The first and the last options are not useful for generation of electricity. It is only when we have a sustained reaction, that we can utilize nuclear energy in an effective manner

There are lots of other interesting things to be learnt about nuclear power plants regarding their working, layout, processes and so forth which we shall do in later articles in this series.

The Advantages Of Maintaining A High Power Factor

Elimination Of Penalty Dollars

A high power factor eliminates penalty dollars imposed when operating with a low power factor. For many years, most utilities demanded a minimum of 85% power factor as an average for each monthly billing. Now many of these same utilities are demanding 95%…or else pay a penalty!

The actual wording or formula in the utility rate contract might spell out the required power factor, or it might refer to KVA billing, or it might refer to KW demand billing with power factor adjustment multipliers. Have your utility representative explain the particular rate contract used in your monthly bill.

This will insure you are taking the proper steps to obtain maximum dollar savings by maintaining a proper power factor.Additional Capacity In Electrical System .A high power factor can help you utilize the full capacity of your electrical system. To refresh our me mory, let’s look again at the power triangle story, shown on figures 1, 2. Remember that KVA is a measure of the total power generated by the utility for yo u to accomplish your KW of work.

Remember that the KVA figure is the amount of power passing through your plant transformer, and limited by its rated size: e.g. 750 KVA, 1500 KVA, 2500 KVA, etc. In the previous example, we reduced your transformer loading from 1160 to 913 KVA, thus allowing for more load to be added in the future.

Reduction Of I2R Losses

A potential savings in billed KW-Hrs can be realized depending upon where the capacitors are located in your electrical system. When capacitors are energized they reduce the total power usage (KVA) from their location in the system up to the utility source. In other words, capacitors reduce the current in amperes that had been flowing from the utility to the capacitor location. This ampere reduction might be as high as 20%. Since watt loss generated by current passing through a conductor is expressed by the formula …

watt loss = (Ampere) 2 x Conductor Resistance (W=I2R)

It is obvious that locating the capacitors at the extremities of the feeders and branch circuits (where the loads are) can result in a sizeable reduction in total KW-Hrs usage every month.