Engineering plant facilities 02 electricity fundamentals
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Transcript of Engineering plant facilities 02 electricity fundamentals
ELECTRICITY
L | C | LOGISTICS
PLANT MANUFACTURING AND BUILDING FACILITIES EQUIPMENT
Engineering-Book ENGINEERING FUNDAMENTALS AND HOW IT WORKS
September 2014
Expertise in Process Engineering Optimization Solutions & Industrial Engineering Projects Management
Supply Chain Manufacturing & DC Facilities Logistics Operations Planning Management
Atom
An atom is the basic constituent of matter. An atom consists of a central nucleus which is surrounded by one or more electrons.
The nucleus contains protons, which are positively charged, and neutrons, which are electrically neutral.
Atom
Electricity Fundamentals
Electrons
Electrons
The electrons closest from the nucleus are strongly attracted. But those which revolve in orbits far from the nucleus, less attracted, can leave easily the atom and become free.
We say that the atom has become a positive ion.
But a free electron can also “hang up” to a neutral atom which will become a negative ion.
Electricity Fundamentals
Voltage
Voltage
The force that wants the free electrons return to the positive ion is called Voltage. The unit for the voltage is the Volt (V) and the conventional symbol is U.
Electricity Fundamentals
Electricity Current
These electrons travel through a conductor.
The movement of these electrons is known as Current. The unit for measuring this flow is the Ampere and the conventional symbol is I.
Current
Electricity Fundamentals
Resistance
Resistance is the opposition to this movement. The unit measuring the resistance is the Ohm (Ω) and the conventional symbol is R. We have the following formula:
U = R.I
Resistance
Electricity Fundamentals
Conductor
A conductor is a material which lets circulate the electric current. There are several different conductors:
Silver (one of the best conductors)Iron, copper, aluminum…
Water (especially salt water)Human body (composed mainly of water)
…
But there are also several materials which are not conductor:
WoodStoneRubberPaper sheet…
Conductor
Electricity Fundamentals
Electric Power & Energy
Electric power is the multiplication of the voltage U by the current I. The unit is Watt (W) and the conventional symbol is P. We have the following formula:
P = U.I
The energy is the consumption of power during a certain period of time. Energy is the product of power, in Watts, and time, in hours. The unit is Kilowatt hour (kWh).
Electric power
Electricity Fundamentals
Direct Current DC
We name the current Direct Current (DC) when the direction of current is flowing in one constant direction.
Direct Current
Electricity Fundamentals
Alternating Current AC
When the direction of current flowing is constantly being reversed back and forth, the current is named Alternating Current (AC).
Alternating Current
Electricity Fundamentals
Period & Frequency
The period is the time required for the same event occurs again. The unit is second (sec) and the conventional symbol is T.
The frequency is the number of times a repeating event occurs during 1 second. The unit is Hertz (Hz) and the conventional symbol is f.
f = 1/T
Period & Frequency
Electricity Fundamentals
Series Circuit
In a series circuit, all of the components carry the same current.
Current: I
Voltage: UPN = UR1 + UR2
Resistance: Rtotal = R1 + R2
Series Circuit
Electricity Fundamentals
Parallel Circuit
In a parallel circuit, the voltage is the same for all elements.
Current: I = I1 + I2
Voltage: U = U1 + U2
Resistance:
Parallel Circuit
Electricity Fundamentals
Single-phase Electric Power
Single-phase electric power refers to the distribution of a single source of Alternating Current.
So we have one conductor for input, the phase, and neutral for output. Typically, a third conductor, called the ground, is used as a protection against electric shock.
Single phase is widely used in rural areas.
Single-phase
Electricity Fundamentals
Three-phase Electric Power
Three-phase electric power refers to the distribution of three sources of Alternating Current.
So in a three-phase system, we have three circuit conductors, with the same frequency, which reach their instantaneous peak values at different times. We have also the neutral and a fifth conductor, the ground.
Three-phase
Electricity Fundamentals
230 V / 400 V
A single-phase system usually frees a voltage, between the phase and the neutral, equals to 230 V.
In a three-phase system, if we measure the voltage between one phase and the neutral, we have 230 V.
The voltage between two phases is equal to 400 V.
We can notice the following formula:
Electricity Fundamentals
Phasing reversed
What happens to a three-phase motor if the phasing of the power source is reversed?
If we reconnect the phases switching any two of the three phases, the motor will turn in the opposite direction. It is important to ensure proper connection of wires because the rotation of the motor can be important.
Tip: there is a color code to get it right.
US EuropePhase 1 Phase 2 Phase 3 Neutral Ground
Electricity Fundamentals
Phase disconnected
What happens when a phase gets disconnected in a three-phase system?
When a phase gets disconnected, the motor will run until it is stopped, but it will not start again. In that case, the other 2 phases will increase in amps.
Electricity Fundamentals
Safe Working Electricity Fundamentals
Electric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Electricity FundamentalsElectric Motor components and applications
Electricity FundamentalsElectric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Electricity Fundamentals
Electric Motor components and applications
Motor burned
Why a motor burns?
There are several reasons why a motor burns. We can retain the 4 following reasons:
All mechanical parts wear out eventually Insulation breaks down over time due to heat exposure Some motors are intended to be lubricated from time to time Anything that is powered by electricity will last longer in a cooler environment.
Electricity Fundamentals
Short circuit
A short circuit is an abnormal low-resistance connection between two conductors supplying electrical power. This results in excessive current flow in the power source and may even cause the power source destroyed.
We saw before the following formula: U = R.I
If we have a short circuit, then R decreases sharply. With this formula, if U must remain constant then I have to increase strongly.
Short Circuit
Practical case:
Assume that U = 9 V. If we have a resistance R equals to 3 Ω then the current I must be equal to 3 A (3*3 = 9).
Now, U = 9 V but R is now equal to 0.03 Ω. The current I = 300 A.
Electricity Fundamentals
Hot Terminals
Why terminals get hot ?
There are several causes for hot terminals; most of them are usually result of focal points of resistance. They often appear with higher temperature at the point of high-strength. Load imbalances appear just as hot at the stage or in the part of the circuit which is bad design or overloaded.
If the driver is hot, it might be is wrong sizing or overloaded.
Why it is important to detect it early?
The most common example of damage is a burned fuse. In the control circuit of a motor, this can produce a single-phase condition and, possibly, a costly damage to the engine.
Electricity Fundamentals
ABC
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Electricity Fundamentals
Content
Overview of electrical power system
Maintenance, Testing and Commissioning
● Regular test
● Maintenance activities
● Cable testing
● Capacitor testing
● Switchboard
● Circuit Breakers
● Contactors and Relays
● Electric Motors
Electrical safety
Electricity Fundamentals
Overview of power distributionElectricity Fundamentals
Maintenance, Testing and Commissioning
Checking the insulation system, electrical properties, and other factors related to the overall operation of the distribution system.
Insulation testing
Relay and protective device testing
Circuit breaker time to trip
Earth grounding resistance
Infrared inspection testing
Power Quality
Regular test
Electricity Fundamentals
Maintenance and Testing
A well-organized and implemented program minimizes accidents, reduces unplanned shutdowns, and lengthens the mean time between failures (MTBF) of electrical equipment:
Cable and cable Insulation
Capacitor Banks
Switchboards
Earth links and potential
Connections
Maintenance activities
Electricity Fundamentals
Cable and Insulation TestingElectricity Fundamentals
Damage to electrical cables can cause them to not effectively transmit electricity. Even worse, these faults can cause electrical sparks which become a fire hazard.
Cable and Insulation Testing
Cable meggers detect cable faults through the use of a pulse echo, which helps electricians locate damage to a cable. Poor joints or impedance cause damage and resistance to the current flow.
Electric cables
Electricity Fundamentals
Cable and Insulation Testing
Testers can find the location of the fault by tracking the amount of time that the pulse takes to reflect back to the cable megger.
Impendence is an opposition to alternating currents.
Testers send a pulse down a cable at a velocity determined by the insulation of the cable. Changes in the cable will cause the pulse to be reflected back.
Electricity Fundamentals
Capacitor Bank Testing
Capacitor Banks
Capacitor Banks should be checked with an Infra-red scanner on a monthly basis.
Six monthly Capacitor test using a megger or Ohm meter, this is specialised work and should be undertaken only by Technicians skilled in this area.
Electricity Fundamentals
Should be infra-red scanned every three months
Main Distribution Board Testing
Main Distribution Board
Electricity Fundamentals
Contactor and Relay Testing
First look at the relay or contactor to find out what voltage it takes to pull in the coil. Check to make sure your getting power to it and the voltage is correct. If yes continue below tests the coil of the relay or contactor is probably open. Set meter to measure Ohms.
1. Each coil contains two terminals A1(positive)and A2 (negative or 0V). 2. Detach wires from A1 and A2 Touch one probe to each terminal. 3. The meter usually read around 80-200ohms. If its less than 20 ohms coil is
most likely shorted. If its above 500 ohms it is most likely open and should be replaced. If possible look for another solenoid to compare readings with.
4. If coil ohm resistance looks ok and correct voltage is at coil, replace the coil or contact.
5. If voltage is low check A1 to the common (0V) on a main terminal strip. If this is ok you have a loose connection or bad wire on the common side.
Contactor & Relay
Electricity Fundamentals
Circuit Breaker Tester: Clamping Ammeter
Circuit breakers that trip every time they're reset may be overloaded.
In order to diagnose a circuit breaker overload you can test the circuit breaker by using a clamping ammeter. This circuit breaker tester is used to check overloads and shorts that are in progress and determine whether the electric current is running through the circuit.
Circuit Breaker Testing
The clamping ammeter should be clamped to a single wire not the cable in order to accurately test the circuit breaker.
Electricity Fundamentals
Electric Motor Testing
Testing and troubleshooting electric motors can save you a trip to a repair shop, but it does require caution.
If they're completely beyond repair, most electric motors will have an acrid smell that indicates burnt windings; if yours doesn't, troubleshooting may lead you to a solution.
Maintenance of electric motor
Electricity Fundamentals
Maintenance of electric motor
Put on safety glasses. Any time you are repairing an electrical device, safety glasses should be your No. 1 tool. Shut off all electric power to the motor, whether by turning off a circuit breaker or removing fuses from the disconnect switch.
Electric Motor TestingElectricity Fundamentals
Read the motor's nameplate data to confirm whether it's a low-voltage a 230-volt motor or a three-phase high-voltage 440-volt motor. This will determine the number of power leads the motor has.
All single-phase 230-volt motors have two wire leads that connect to the power supply.All three-phase 440-volt motors have three wire leads that connect to the three-phase power supply.
Electric Motor TestingElectricity Fundamentals
Remove the plastic wire connectors that connect to the power supply.
You may have to identify the power leads to the wires on the motor if it is a three-phase motor. This will ensure the rotation will be correct when you re-terminate the motor.
Electric Motor Testing
Turn your volt-amper meter to the ohm setting. The meter should read OL (open lead) or zero ohms.
Electricity Fundamentals
Electric Motor Testing
Touch one lead to the case of the motor, and test each motor lead. The ohm meter should read OL, or zero ohms.
If a reading of any ohms is observed, you may have a direct short in the motor windings; the motor may be bad.
Some motors, especially the three-phase type, may have a large resistance reading--in the 20 mega ohms range or larger. This may be fine, or this may be a sign that the bearings are going bad, as the motor may have deteriorating windings due to excessive heat.
Electricity Fundamentals
Remove the capacitor from its housing if you are testing a single-phase motor that has a capacitor. Be careful not to touch the exposed leads.
The capacitor is like a battery and stores a high-voltage charge. Turn your volt ohm meter to volts and carefully touch to the bare leads of the capacitor.
Electric Motor Testing
If voltage is read, the capacitor still contains a charge. Holding the leads of the meter to the capacitor should show it discharging.
Electricity Fundamentals
Electric Motor Testing
Continue until zero voltage is observed on the meter.
Most modern volt ohm meters have a capacitor-testing switch, making it easy to determine the status of the capacitor.
In most cases, the capacitor only needs to be replaced on these types of single-phase motors.
Electricity Fundamentals
Deaths
Electrocutions rank fourth (9%) in causes of industrial fatalities (behind traffic, violence and construction). The National Safety council estimates 600 people die every year of electrical causes. Most of these accidents involve low voltage (600 volts or less).
Effects on your body
A small night-light with a 6-watt bulb draws 0.5 ampere, and even that small amount of current can be fatal. Here are some effects of current (in milli amps) passing through a 150 pound body (note that perception is only .5 to 1.5 milli amps):
Shock you painfully Damage sensitive equipment Ignite combustible materials Can be fatal
Electrical Safety
Why Worry About Electricity?
Electricity Fundamentals
This training module will cover some basic safety rules you should follow in regards to electrical safety.
Electrical SafetyElectricity Fundamentals
What are the leading causes of electrical accidents?
The leading cause is Unsafe Acts.
Electrical Safety
There are 2 reasons for unsafe acts: 1. We know better but intentionally do
something unsafe. 2. We don't know better.
Electricity Fundamentals
Procedure to avoid the following unsafe acts
1. Failure to de-energize, lockout & tag out hazards during maintenance, repair or inspections.
2. Use of defective and unsafe tools. 3. Use of tools or equipment too close to energized parts. 4. Not draining off stored energy in capacitors. 5. Using 3-wire cord with a 2-wire plug. 6. Removing the third prong (ground pin) to make a 3-prong plug fit a 2-
prong outlet. 7. Overloading outlets with too many appliances. 8. Using the attached electrical cord to raise or lower equipment. 9. Not verifying power is off when making repair (drilling into a 110 Volt
AC line can kill). 10. Working in an elevated position near overhead lines.
Electrical SafetyElectricity Fundamentals
Electrical Safety
• Loose connections
• Faulty insulation
• Improper grounding (removal of 3rd prong)
• Use of "homemade" extension cords
• Defective parts
• Unguarded live parts--for example:
• Bare conductors or exposed terminals • Metal parts of equipment may become energized when connected by cord or plug. Capacitance may cause up to 55% of line voltage to be stored on the casing of metal tools.
Some common causes of unsafe equipment
Electricity Fundamentals
Hazardous Environments
Use special precautions when working in potentially hazardous environments and situations. Even an accidental static discharge can cause a fire or explosion in areas where the following are present: •Flammable vapors, liquids and gasses •Combustible dusts •Corrosive atmospheres •Explosive environments •Poor housekeeping: blocked electrical boxes, flammable materials stored in equipment rooms, lack of proper hazard signs, excess clutter.
Electrical Safety
Special care is also need in wet or damp locations - water and electricity are a bad combination. If the wire is frayed or damaged, a fatal electrical shock can result.
Electricity Fundamentals
What can you do to help protect yourself ?
Basics of Electricity:
•Electrical current will not flow unless it has a complete path (circuit) that returns to its source (battery, transformer). •Current flows through you and other conductors, such as metals, earth and concrete. •Current can harm you when it flows through your body (electric shock). •Insulators resist the flow of electricity. Insulating materials are used to coat copper conducting wires and are used to make electrical work gloves. Insulators help to protect humans from coming into contact with electricity flowing through conductors. •Just as there is pressure in a water pipe, even with no water flowing, there is voltage at a receptacle, even if current is not flowing. Another word for voltage is "Potential."
Electrical Safety
You have to know about electricity and how it can harm you and your colleagues.
Electricity Fundamentals
How electricity can harm you ?
Current passing through your body can cause electric shock, resulting in 3 types of potential injuries:
Burns (arcs burn with heat & radiation) Physical injuries (broken bones, falls, & muscle damage)
At 10 mA, the muscles clamp on to whatever the person is holding.
Nervous system effects (stop breathing at 30 to 75 mA alternating current at 60Hz, fibrillation at 75 to 100 mA at 60Hz)
Fibrillation = heart is "twitching" and there is no blood flow to the body.
The heart can be damaged because it is in the path of the most common routes electricity will take through the body:
• Hand-to-hand• Hand-to-foot
Electrical SafetyElectricity Fundamentals
Electrical Safety
Minimize your exposure to static shocks
Never clean the glass face of your computer monitor while the computer is on.
You can be injured by the reaction to the shock even though such shocks in themselves are not hazardous.
During normal operation, the glass surface of a monitor's CRT accumulates an electrostatic charge. When you touch the screen with a finger, the charge is from the portion of the screen you touched and it discharges through your finger with a tiny spark. Electric current does not normally flow through glass, so only the part of the screen that your finger touches is discharged.
However, when you clean a monitor the entire glass is wet and the charge on the entire screen will discharge to your finger or hand, causing a much more painful shock.
Electricity Fundamentals
Control hazards though safe work practices
• Plan your work and plan for safety • Avoid wet working conditions and other dangers
• Use Ground Fault Circuit Interrupters. GFCI's are electrical devices that are designed to detect ground faults (when current is "leaking" somewhere outside its intended pathway). If your body provides the path to ground for the leaking current, you could receive a shock or be electrocuted. GFCI's should be used in all wet locations and on outside outlets.
• Avoid overhead power lines: Position yourself so that the longest conductive object you are using (saws, poles, tools, brooms, etc.) cannot come closer than at least 10 feet to any unguarded, energized overhead line.
• Use proper wiring and connectors • Use extension cords properly and temporarily: • Cords must be UL listed and have 3 prongs • Power bars must have a fuse or breaker • Do not use 2-prong, ungrounded cords in a lab • Do not run cords through walls, doors, under rugs, or across aisles • Do not repair cords--buy new ones
Electrical SafetyElectricity Fundamentals
Electrical SafetyElectricity Fundamentals
Follow the Administrative Controls
Safe work procedures Lockout and Tag out Proscribed work practices Signs warning of electrical hazards
Electrical Safety
Use safe equipment Do not use equipment that has been damaged or improperly modified. Always use equipment according to the manufacturer's specifications. "Live" parts (greater than 50 volts) must be guarded by one or more of the following: An enclosure that requires a tool for access. A locked enclosure. An interlocked access door. A substantial insulating guard to prevent contact. Check cords--they should: Be completely free of damage and deterioration.
Electricity Fundamentals
Electrical Emergencies: How to Respond ?
Electrical SafetyElectricity Fundamentals
Electrical Shock
A small night-light with a 6-watt bulb draws .05 ampere, and even that small amount of current can be fatal.
Protect yourself Don't touch the person. That person might be energized, so take time to protect yourself. Don't try to use a conductive tool to free the person. Don't touch anyone who has become grounded.
Electrical Safety
Call for help, if the person:
is obviously injured (loss of consciousness, significant trauma, etc.) has an altered mental status (confusion, slow/slurred speech, etc.) has other obvious injury (laceration, burn, etc.)
Electricity Fundamentals
First things to do when there is an electrical accident
Keep others from being harmed Shut off the power (fuse or circuit-breaker or pull the plug; this might
be difficult because there might be secondary sources; if you are not sure, get help)
Move the victim to safety only when power is OFF and no neck or spine injuries are possible
Give necessary first aid (keep CPR training up-to-date). Report accident to supervisor (even minor shocks and close calls must be
reported) Secure area Collect data for an investigation and to prevent reoccurrence.
Electrical SafetyElectricity Fundamentals
Electrical Safety
In Summary
Electricity Fundamentals
Safe Working
Learning objectives
By the end of this program participants will be able to demonstrate their understanding of the control measures to be followed , as detailed in the safe working procedure, when working with fixed and portable electrical systems and equipment.
Electricity Fundamentals
Safe Working
Operational Analysis and Control (OAC)Model
Analyse the Operation
Manage the Operation
Effectiveness Review
What can cause harm?What are you doing about it?Is it enough?
What has to be done?What resources do you need?When does the operation need reviewed?
Has the operation progressed as planned?Detail the changes needed?List the improvement actions?
Electricity Fundamentals
Safe Working
Set your work objectives to include
“...tasks/ activities are to be completed on time and in a manner that does not cause harm to the employees, customers, other non-employees, or the company/ organisation.”
Three key questions to start with are… • What can cause harm?• What are you doing about it?• Is it enough?
Remember the process is simple but it is NOT to be considered simplistic.
Electricity Fundamentals
Safe Working
Know where the harm is:
Identify the key hazards & outcomes of exposure to electricity
Source of hazards (non-exhaustive list)
BatteriesDamage items, e.g. light bulbs
Fixed electrical installationsFlammable and explosive environments
Fuses, circuits and other devicesOverhead lines
Portable electrical appliancesSockets and plugs
Static electricitySwitches and conduits
Trailing cables and leadsUnderground cables
Outcomes of exposure (non-exhaustive list)
ShockBurnsArcing
FireExplosion
Electricity Fundamentals
Short circuit
If it is a battery that is shorted, the battery will be discharged very quickly.
Short circuit can produce very high temperatures due to the high power dissipation. Electric arc is a common example due to short circuit.
Short Circuit
Electricity Fundamentals
Safe Working
Controlling the Hazard - Options
In priority order:
Eliminate where possible, Use control measures,
Protect all those exposed to the hazard
Electricity Fundamentals
Safe Working
Systems and Equipment
Proper design, construction and maintenance.
Employ competent staff.
Maintain competence.
Inspections and tests.
Pre-use visual checks.
Electricity Fundamentals
Safe Working
Preventative Action
Inspect all electrical equipment,
Check suitable circuit protection equipment is installed,
Test equipment for circuit protection,
Regularly inspect equipment,
Avoid work near live conductors,
Use proper systems,
Use safe working methods,
Ensure competence.
Electricity Fundamentals
Safe Working
When equipment faults occur or are identified…
Isolate from the power source,
Put a warning label on,
Report the fault, and
Have the equipment repair or replaced.
Electricity Fundamentals
Safe Working
Construct & protect equipment from…
Mechanical damage,
Effects of weather, temperature and pressure
Effects of any other natural hazards,
Effects of wet, dirty, dusty or corrosive conditions, or
Any flammable or explosive substances.
REMEMBER Electrical systems and equipment for use in potentially flammable or explosive atmospheres are to be appropriately Certificated as being intrinsically safe.
Electricity Fundamentals
Safe Working
Business Activity Managers
Safety Managers
Managing Director
Employees
Duty Holders
Ensuring compliance.
Providing professional safety advice.
Complying with the requirements.
Responsible for…
Co-operating with the requirements.
Electricity Fundamentals
Safe Working
Documentation
Schedule of inspections and tests.
Maintenance log.
Statutory certifications.
Company Specific Statutory documents
Electricity Fundamentals
Thank You
L | C | LOGISTICS PLANT MANUFACTURING AND BUILDING FACILITIES EQUIPMENT
Engineering-Book
ENGINEERING FUNDAMENTALS AND HOW IT WORKS
ELECTRICITY