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Smoked Flavor From Electric Grills
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With the advent of electric grills, it is possible to cook food outdoors without the mess of charcoal, lighter fluid, or blinding smoke. What can go missing is the smoky flavor that so many desire from food off the barbecue. Here are some tips to help you grill with electricity but still get that smoked food taste.

Safety is always the first priority in all outdoor cooking. Just because there is no flame, it doesn’t remove all fire risk. Follow clearance measurements stated in the owner’s manual to cook a safe distance from all structures. If you must use an extension cord with your grill, use the proper gauge or thickness and length to avoid overheating the cord from excess resistance. Never leave your grill unattended. A flare-up or grill knocked over from a gust of wind can quickly ruin your food or your day.

Your smoke source will be wood, of course, in the form of chips or a large chunk. The wood can be soaked in water beforehand, but that will only increase the time it takes to get smoke. Wrap a handful of chips in a double layer of heavy aluminum foil, and use a fork to poke a few holes in it. Poke too few holes, and the wood will not get enough air to burn. Poke too many, and the wood may burn up too quickly.

Whether wood chips or chunks, you will need to learn the nature of your particular grill to determine the best placement. The wood may be best suited to positions above, below, or beside the element. So long as you get a small but steady stream of smoke, it is enough.

If your electric grill cycles the element on and off based on the thermostat, it may be necessary to increase the heat setting to have enough heat to get wood smoking. The next consideration becomes how to avoid burning the food. Increase the distance between the element and the food when you’re smoking it. If you increase the heat setting but don’t get smoke, you may need to slightly alter the element control to allow turning it slightly higher. That option is beyond the scope of this article.

The smoke cannot be excessive from the wood, nor can it be allowed to accumulate around the food. The goal is a stream of smoke around the food and out the top area of grill. If your grill lid has a vent hole of some sort, it needs to be fully open or mostly so. Merely tilting the grill lid may not allow smoke to stream out. You may have a thermometer in the lid; this is an ideal place to put a vent hole for the smoke. Remove the thermometer and plug most of it with aluminum foil. Another solution is to use a metal can top screwed through the lid next to the hole to adjust the smoke exhaust.

Another obvious safety point is to remember the possibility of your wood flaming up. Keep a spray bottle of water handy to mist the wood. Remember that the smoking wood gets a large load of oxygen when you lift the lid, and you should be prepared to keep it safe.

Treadmill Fitness Equipment – Manual Treadmill Or Electric Treadmill, Which is Better?
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Looking to get some treadmill fitness equipment? When you’re looking for a treadmill, there are 2 main considerations, you need to decide on if you want a manual treadmill or an electric treadmill. This article will help you to distinguish between the two so that you pick up the treadmill fitness equipment that is right for you.

1. Manual Treadmill

A manual treadmill is often going to be the cheaper of the two options as there is no motor that powers it. It is run based off of momentum. In order to get it started, you need to apply your body weight to it to get the treadmill conveyor rolling. Once its rolling you can then resume running at a more even pace.

Not everyone likes having this kind of functionality though, it’s a bit primitive, however it does get the job done. This kind of treadmill is perfect for someone on a small budget.

2. Electric Treadmill

On the other hand, if you need the treadmill to come with bells and whistles, you had best look to an electric treadmill. Electric treadmills will give you things like heart rate monitors and intensity programs. You can even adjust the incline on the fly as well as the resistance.

This all comes at a premium though as electric treadmills are often double the cost, coming in at $500-$1000 at the cheapest levels.

When you’re deciding on the treadmill fitness equipment that is right for you, it’s essentially going to come down to price. I would look upon this as a long term investment though and go with the more expensive of the two, if you do it will last you at least a good 5 years.

Class of Protection in Electrical Appliances
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All electrical appliances using mains voltage have to provide at least 2 levels of protection to the user. This is to ensure that if one of the protection layers were to fail, there is the back-up of the second layer still in place. This makes electrical equipment very safe to use. Appliances can be Class 1 or Class 2.

When PAT testing, it is important to first identify the Class of the appliance as Class 1 appliances are tested differently from Class 2 appliances.

Depending on how exactly the protection is provided, electrical appliance are put into 5 Classes of equipment construction which are Class 1, 2, 3, 0, 01. Of these the most important are Class 1 & 2. For completeness all the Classes are described below.

CLASS 1

Here the protection is provided by a combination of insulation and use of the mains Earth. It is best shown by referring to an electric fire that has been taken apart.

In the open plug the three wires connecting to the LIVE, NEUTRAL and EARTH pins. Inside the fire, the brown LIVE wire and the blue NEUTRAL wire connect to a plastic connector. The green/yellow Earth wire connects to the metal case of the fire.

The user is protected from electric shock by the plastic insulation of the connector. This holds the LIVE and NEUTRAL wires in place and prevents them from touching the metal case of this electric fire. This plastic insulation of the connector is known as basic insulation.

If this basic insulation were to fail, say due to excessive movement of the cable where it touches the metal case then the user of the fire can receive an electric shock if not for the fact that the EARTH wire is present.

By connecting to the metal case of the electric fire, the EARTH wire keeps all this metal at EARTH potential. What this means is that it is impossible to get an electric shock even when the metal case of the fire is connected directly to the LIVE voltage. In practice a fuse would blow either in the plug or the main fuse box to protect the user.

In summary, in Class 1 appliances the user is protected by a combination of basic insulation and the provision of an EARTH connection, thus providing two levels of protection.

When PAT Testing Class 1 appliances, the Earth Continuity and Insulation Resistance tests are carried out.

CLASS 2

In a Class 2 appliance, the user is protected by at least two layers of insulation. For this reason, Class 2 appliances are also known as Double Insulated. They do not require an Earth connection.

This is best shown by looking inside a Class 2 electric drill which has been opened up. Inside one can see that as well as the plastic connector providing basic insulation, there is additional insulation provided by the plastic enclosure of the drill.

The user is therefore protected by two separate layers of insulation. When PAT testing Class 2 appliances, just the Insulation Resistance test is carried out.

Class 2 appliances are always indicated by the double box symbol on the rating plate.

CLASS 3

Equipment built to Class 3 standard are designed to be supplied from a special safety isolating transformer whose output is known as Safety Extra-Low Voltage or SELV. This must not exceed 50 V AC and is normally is below 24V or 12V. All Class 3 appliances are marked by a special symbol. There is no use of an Earth in Class III appliance

The electrical safety of Class 3 appliances are taken care of in the safety isolating transformer design where the separation between the windings is equivalent to double insulation. The transformer is marked as being suitable for use with Class III appliances.

CLASS 0 & 01

This type of equipment is not for normal use in business or residential environments. It is just presented here for completeness.

Class 0 appliances depend only on basic insulation for protection from electric shock. For this reason, they do not have 2 levels of protection built in and are not allowed for sale. The brass lamp shown here is an example of a two wire, metal cased appliance with only basic insulation. There is no provision for connection of an earth to the bulb holder.

In Class 01 appliances, there is provision for an Earth connection, but it is wired with either twin core cable or only has a 2-pin plug, so an Earth cannot be connected. AS in Class 0 equipment, one is dependent only on basic insulation for protection from electric shock. As they only have 1 level of protection, Class 01 appliances are not allowed for sale.

If during PAT testing one comes across a Class 0 or Class 01 appliance these can be failed.

IDENTIFYING CLASS I & CLASS II APPLIANCE

As the PAT testing carried on Class 1 and Class 2 appliances differ, it is important to identify one from the other. There is no other area of PAT testing that causes more confusion than this and there are many myths surrounding this. It will be informative to list some of these.

If there is a fuse in the plug, then it must be Class 1.

It is made of metal so it must be Class 1

The case is plastic so it must be Class 2

It has a three core cable so it must be Class 1

The plug has a metal Earth pin so it must be Class 1

None of the above statements is a fool-proof way to identify Class I and Class II appliances and some are quite misleading.

The easiest rule to apply is the one below.

If the rating plate has a double box then the appliance is Class 2. If it does not then it is Class 1.

Example – Kettle

The rating plate on this kettle clearly has no “double-box” symbol, so using our rule, it must be Class 1. The Earth connection from the plug is terminated on the outside metal casing of the heating element. When PAT testing this kettle the Earth Continuity and Insulation Resistance test has to be carried out.

Example – Plug-top power supply

The rating plate on this Plug-top transformer clearly shows the “double box” symbol, so this is a Class 2 appliance. Note that it has a plastic Earth pin, as this is not required for Class II. (Not all Class 2 appliances have a plastic earth pin). Just the Insulation Resistance test has to be carried out during PAT testing.

Example – Mains extension

The rating plate on this extension is moulded in the plastic. It clearly does not have a “double-box” symbol, so it must be a Class 1. When PAT testing this extension lead the Earth Continuity and Insulation Resistance test has to be carried out.

Example – Table lamp

The rating plate on this table lamp clearly shows the “double-box” so it is a Class 2 appliance. (Note that this is a Class 2 appliance that is largely in a metal enclosure). The bulb holder is made of plastic and provides the required double insulation. Just the Insulation Resistance test has to be carried out during PAT testing.

Example – Desk fan

The rating plate for this fan not only does not have a “double-box” symbol, it also says that the appliance must be earthed. So this is clearly a Class 1 appliance. Note that it does not have any user accessible metal.

Example – Metal Lamp

If this metal lamp had a rating plate, then it would be a Class 1 appliance as it has an earth point on the lamp holder. However, as the rating plate is missing, this would have to be failed.

Are Class 1 and Class 2 appliances just as safe?

As both have 2 levels of protection built in, they are both safe for general use.

However with Class 1 an appliance, one of the layers of safety is provided by the earth connection. For this to be effective, the wiring in the building has to be inspected regularly to check that the Earth in the mains socket is correctly taken to the local earth potential. This is usually picked off the Earth sheathing of the mains cable coming into the premises, or by driving a local stake into the ground. So Class 1 appliances depend on the external wiring in the building to fully provide the 2 levels of protection.

Class 2 appliances however always provide 2 levels of protection irrespective of the status of the wiring installation. Both layers of protection are built into the design making Class 2 appliances are a lot safer than Class 1 appliances.

How the Electric Guitar Revolutionized the Music Industry
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When you first listen to a song, with the exception of the lyrics, the first sound that you’re going to recognize is the sound of the guitar. No guitar has changed music, quiet like the electric guitar.

Before the electric guitar, there was America’s beloved acoustic guitar. It greatly changed music in that it allowed musicians alternatives to the mandolin and banjos. The acoustic guitar is a huge asset for songwriters because of its portability, which allowed musicians to write or perform their music almost anywhere.

When the electric was first built in the 1930’s, it was met with strong resistance. Critics actually believed that the sounds would not be appealing to music lovers and they didn’t believe the electric guitar would make it off the assembly line. Even the original creator couldn’t have imagined the impact that the electric guitar would have on the music industry. No one in those days could have. The very first electric to be manufactured and sold to the general public was built by the Electro String Company in 1931. These guitars were actually made from cast aluminum, and people actually referred to them as “frying pans”, which prompted the Gibson Guitar Corporation to create their ES-150 guitar. These guitars quickly became popular and this particular Gibson guitar became one of Gibson’s best sellers, ever. And when artists began to realize that the electric gave them the flexibility to create their own musical style, it started to change the sound of music.

The invention of the electric was a huge asset to concert halls. Before it, concert halls we’re smaller, accommodating smaller crowds. This was because the acoustic guitars’ sound was hard to hear from a distance. It allowed venues to expand because the sound could be amplified, allowing much more people to hear the concerts from a greater distance. Concerts started to change forever. Now, instead of a musician playing for a few hundred people, they were playing for a few thousand. And today, musicians are performing for a few hundred thousand fans and selling out every single seat!

Electrics have evolved from the original production. There are additional pickups on the modern guitars that allow artists to create unique, individual music styles. No guitar has been able to capture the emotions of a song or its musician like the electric guitar. What makes the guitar able to do this is that it can be amplified. You can’t have one without an amplifier. When used alone, it doesn’t create the mood changing sounds that the amplifier does. The electric guitar and amplifier go hand in hand. The amplifier to the electric guitar is the bread to the butter in the music industry.

No one can truly evaluate the way music has changed over the last several years. Great music has the power to change lives. Music expresses what simple words alone cannot. The electric guitar expresses the feelings that words cannot. The sounds of the electric guitar are electrifying (no pun intended). It has created some of the best performances ever. It has become the very definition of rock and roll. It will continue to revolutionize music for generations to come.

What’s the Difference Between a Tuned and an Untuned Oscillator Circuit?
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A tuned oscillator uses a LC (inductor-capacitor) tank-circuit, a frequency-selective RC (resistor-capacitor) circuit or a quartz crystal circuit in its feedback path. Generally, the output waveform shape from a tuned oscillator circuit is sinusoidal and for this to happen positive feedback is used around an amplifying device such as a transistor or op-amp.

If negative feedback is applied to an amplifier the gain of the amplifier is decreased but the stability is increased. With positive feedback however, the gain is increased but the stability is decreased. This increase in gain produces a situation where an alternating sinusoidal output is obtained without a signal input. The amplifier has now become an oscillator giving an alternating output with the energy required to maintain this oscillation is obtained from the d.c. supply.

A tank-circuit consisting of a parallel-tuned LC circuit or RC circuit is used as the frequency determining unit which is “tuned” to give oscillations around its resonant frequency, hence the name tuned oscillator. The output from this device is feedback to its own input in such a way that the feedback signal aids the change in input signal. No input signal is required because the frequency determining unit provides its own signal via the feedback network in such a way that the circuit is self-exciting. Then this type of circuit is known generally as a Feedback Oscillator (positive feedback) and oscillators which use this technique are:

LC Oscillators: As their name implies, LC oscillators consist of a parallel tuned inductor-capacitor tank circuit as their frequency determining unit. The capacitor is constantly charging and discharging through the inductor coil at its selected resonant frequency but due to the heavy losses in the resistive element of the coil, the dielectric of the capacitor, and in radiation from the circuit. So in a practicle LC circuit the amplitude of the oscillatory voltage decreases at each half cycle and these oscillations would eventually die away to zero. If sufficient energy is applied at the appropriate time from a d.c. power supply in the cycle to overcome these losses then oscillations will continue at a constant frequency and amplitude indefinitely. Resonant frequency occurs when the coils inductive reactance (XL) equals that of the capacitive reactance (XC). Oscillations are controlled by varying the value of the capacitor (varactor).

Tuned oscillator circuits which use an LC (Inductor/Capacitor) tank circuit include:

• Hartley Oscillator
• Clapp Oscillator
• Colpitts Oscillator
• Tuned Collector Oscillator
• Pierce Oscillator
• Miller Oscillator

RC Oscillators: RC oscillators are also known as “phase shift oscillators” because their oscillating elements are made up of resistor-capacitor circuits which produce a phase-shifting circuit which corresponds to positive feedback. RC networks are not naturally oscillating circuits but become oscillating elements when connected around transistor or operational amplifiers.

RC oscillators do not use inductors but instead produces oscillations at a frequency at which the RC network produces a 180 deg. phase shift. A single stage amplifier will produce 180 deg. phase shift between its input and output and which can be used as a stage to produce the required positive feedback. The output from the amplifier is fed back via the RC network to its input. The input is shifted 180 deg. through the amplifier and 180 deg. through the RC network and 180 deg. + 180 deg. = 360 deg. or zero phase shift.

One useful property of the RC oscillator is that output frequency is inversely proportional to capacitance which means that a change in capacitance produces a much higher frequency compared to the LC oscillator. However, the disadvantages are that the output power of the RC oscillator is low due to dissipation in the resistive elements and for positive feedback to occur the amplifier gain must be greater than 29.

Tuned oscillator circuits which use a RC (Resistor/Capacitor) phase shifting circuit include:

• Ladder Phase Shift Oscillator
• Relaxation Oscillator
• Quadrature Oscillator
• Wein Bridge Oscillator
• Switched Capacitor Oscillator
• Digitally Switched Oscillators
• Phase Advance Oscillator (current transfer)
• Phase Retard Oscillator (voltage transfer)

Crystal Oscillators: Quartz and some other crystalline substances exhibit the “piezo-electric” effect. When a mechanical stress or physical deformation is applied to two surfaces of a suitably cut crystal it will produce a voltage between the surfaces. Likewise, when a voltage is applied to the crystal it causes a small physical deformation to the actual shape of the crystal.

Then if the voltage produced by mechanical deformation is fed back in some way, it will itself produce mechanical distortion in the crystal which will produce a voltage, which will…continue forever. This forms the basis of a number of crystal oscillators, because this feedback occurs only at the natural frequency of vibration of the crystal with this natural frequency value being determined by the “cut” of the crystal. Then the crystal in fact behaves as a resonant circuit with a very narrow bandwidth.

There is a limit to the stability and frequency that can be obtained from normal LC or RC tuned oscillators. Quartz crystal oscillators operate at very high frequencies up to 10Mhz when operating in the parallel mode. They also have very high stability and a resonant frequency with a very high Q factor making them ideal for use in CPU, microcontroller and video applications.

“Untuned Oscillators”

Unlike the tuned oscillators above, an untuned oscillator has no LC tank-circuit, frequency-selective RC or crystal circuit in its feedback path. Instead, an untuned oscillator uses nonlinear feedback and generally, the output waveform from an untuned oscillator is non-sinusoidal such as square-wave, triangular-wave or pulse being characterised by a sudden transition from one condition of stability or state to the next. Untuned oscillators are more commonly known as relaxation oscillators. Types of untuned oscillators include:

Ring Oscillator: Ring oscillators consist of an “odd” number of logic gates or amplifiers connected together in a series chain so that the output of the last is connected to the input of the first producing a ring type circuit. The frequency of oscillation depends upon the proporgation delay of the components used and the number of odd “stages” that are within the ring. Oscillation frequency is very high as to is the power consumption. Ring oscillators are more of a novelty as their high frequency and use of components make them impractical as an oscillator.

Relaxation Oscillators: Relaxation oscillators are more commonly known as multivibrators. They are a class of oscillator in which the active devices (usually a transistor) in the circuit are driven well beyond their cut-off and saturation regions for a period of time. Relaxation oscillators are cheap and easy to build with the three main types of multivibrator being.

• Astable Multivibrator: – has no stable state.
• Monostable Multivibrator: – has one stable state.
• Bistable Multivibrator: – has two stable states.

555 and Timer Chips: As well as our old favourite the NE555 timer and its variations, there are a whole host of different chips available in both TTL and CMOS that can be used to generate a variety of different waveforms and signals with some of the most popular being the: 74LS121, 74LS123, 74LS221 and their variants.

Tankless Water Heater Information
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Just like you wouldn’t leave the heating systems switched on in your home when you are away for a vacation, wouldn’t it be a whole lot wiser if you were using heating systems for water only when you were actually using the hot water? Conventional water heaters heat your water and then save it all up in a tank and wait for you to use it. This seems pretty convenient. After all, when you do need the water, it is all ready and available. However we rarely realize the amount of electricity that would be wasted in maintaining the hot water at its given temperature. also, there is only a limited supply of hot water at a go, when it finishes off, you must wait for another long while before more water becomes available. The solution to all of this? Tank-less water heater.

Tank-less water heaters can heat water without the need for any kind of a storage tank. They do so by being an intermediate step between the cold water line and the hot water tap. When you need hot water, you simply turn the tap on, as the water starts flowing through the pipe, sensors switch on the heater which then heats the water as it travels to the tap. Usually these units have a long coiled pipe inside of them which allows water to travel a greater distance inside the unit, hence allowing greater time to heat the water. The heating element can be electric or gas. In case of electric element, high resistance coils are wound along the length of the pipe, hence allowing the pipe to get heated up on demand, and hence heat the water as it flows through it. In the other case, gas is used in small burners which too in turn do the same thing by heating the pipe up.

Of course, there are limitations to using such devices. They do not allow fast flow of water which is possible with storage tank heaters, since they are just emptying the tank. The water flow may be slow, but it would be consistent and indefinite. Since there is no storage system, hot water would keep flowing as long as you need it. For a household, it would be wiser to get multiple units or booster units to ensure consistent supply of water because high requirements can take a toll on this system. The benefits of going through the trouble of installing these systems is immense, they can bring down the energy usage by 1/3rd for a house that uses 41 gallons of hot water in a day.

Which tank-less water heater you use would depend on your location and your requirement. Locations makes a difference because the incoming water temperature would play a major role in deciding which heater you need. Also if your necessary temperature rise is achievable by gas or electric heating element would decide the kind that you choose. But rest assured, whichever heating system you may use, using tank-less water heaters would help save energy.

Thermal Plants
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SWITCHYARD and GENERAL SIGNIFICANCE

Electrical energy management system ensures supply of energy to every consumer at all times at rated voltage, frequency and specified waveform, at lowest cost and minimum environmental degradation. The switchgear, protection and network automation are integral parts of the modern energy management system and national economy.

The modern 3-ph, 50 Hz, AC interconnected system has several conventional and non-conventional power plants, EHV AC and HVDC Transmission system, Back to Back HVDC coupling stations, HV Transmission network, substations, MV and LV Distribution systems and connected electrical loads. The energy in electrical form is supplied to various consumers located in vast geographical area, instantly, automatically, and safely with required quality at all times. The service continuity and high quality of power supply have become very important.

For fulfilling the foresaid purpose, a state of the art, scientifically and technologically advanced SUBSTATION is required. Sub-Station is the load control center of the thermal plant where power at rated voltage, frequency and waveform is exported/imported as per requirements.

The substation at GHTP Lehra Mohabat has only one 220 KV switchyard. There are two output units each having a capacity of 210 MW. The generating voltage is limited to 15.75 KV and this voltage as stepped up by two-generator transformer 15.75/220 KV manufactured by BHEL. A part of 15.75 KV supply is fed to unit auxiliary transformer, which is stepped down to voltage 6.6 KV which is used to run the major auxiliaries of the plant.

After step up, the 220 KV output from the generator transformer is fed to either of the two bus bars through relays and circuit breakers and these are connected to various feeders through various equipments.

DIFFERENT TYES OF EQUIPMENTS USED IN SUB-STATIONS

1. BUS-BARS: –

Bus bar is a term used for main bar of conductor carrying an electric current to which many connections may be made. These are mainly convenient means of connecting switches and other equipments into various arrangements.

At GNDTP there are two 220 KV bus bars. These are made of aluminium and all the incoming and outgoing supplies are connected through the bus bars.

2. LIGHTENING ARRESTORS: –

These are equipments designed to protect insulators of power lines and electrical installations from lightening surges by diverting the surge to earth and instantly restoring the circuit insulation to its normal strength with respect to earth.

3. CURRENT TRANSFORMERS: –

The main purpose of current transformer is to step down the current to a level that the indicating and monitoring instruments can read. When rated current flows through its primary winding, a current of nearly 1 amp will appear in its secondary winding.

The primary is so connected that the current being passes through it and secondary winding is connected to an ammeter. The CT steps down the current to the level of the ammeter.

4. POTENTIAL TRANSFORMER: –

These are used to step do the voltage to a level that the potential coils of indicating and monitoring instruments can read. These are also used to feed the potential coils of relays. The primary winding is connected to the voltage being measured and the secondary winding to a voltmeter. The PT steps down the voltage to the level of the voltmeter.

5. POWER TRANSFORMER: –

These are used to step up down the voltage from one a.c voltage to another a.c voltage level at the same frequency. Shunt reactor in EHV substations is to provide reactive power compensation during low loads.

6. WAVE TRAP: –

Wave trap is used to prevent high frequency signals from entering other zones.

7. INDICATING AND METERING INSTRUMENTS: –

Ammeters, voltmeters, watt meters, KWH meters, KVAR meters are installed in sub-station to watch over the currents flowing in the circuit and the voltages and the power loads.

8. ISOLATORS: –

One of the cardinal measures for ensuring full safety in carrying out work on equipment in electrical installations is to disconnect reliably the unit or the section on which the work is to be done from all other live parts of the installation. To guard against mistakes, it is necessary that apparatus, which makes a visible break in the circuit such as isolators, should do this.

Isolators do not have arc control devices therefore cannot be used to interrupt currents at which the arc will be drawn across the contacts. The open arc in these is very dangerous, in that it will not only damage the isolator or the equipment surrounding it but will also cause the flashover between the phase in other words, it will result in short circuit in the installation i.e. why isolators are used only for disconnecting parts after de-energizing them by opening their respective circuits by use of their circuit breakers.

9. EARTHING SWITCHES: –

Earthing switch is used to discharge the voltage on dead lines to earth. An auxiliary switch to provide interlock always accomplishes it.

10. CIRCUIT BREAKERS: –

Circuit breakers are mechanical devices designed to close o open contact or electrical circuit under normal or abnormal conditions. CB is equipped with a strip coil directly attached to relay or other means to operate in abnormal conditions such as over power etc. In GNDTP three types of CB are used. SF6 CB is used to control 220 KV in switchyard.

VCB are used to control 6.6kv in switchgear & ABCB are used to control 415 KV in switchgear.

In sulphar puffer type SF6 CB is filled with SF6 gas at single pressure (4to6kgf/cm2). The pressure and gas flow required for arc extinction is obtained by piston action.

In double pressure type SF6 CB the gas from high-pressure system is released to into low-pressure system over the arc during the arc quenching process.

SPECIFICATIONS OF CB TYPE ELF-SL4-1

S. NO. SPECIFICATIONS RATINGS

1. Voltage 245KV

2. Normal current 3150 A

3. Lightening impulse withstand Voltage 1050V

4. Switching impulse withstand voltage 1050V

5. Short circuit breaking current 40KA

6. Short circuit withstand current And duration 40KA 3 sec

7. Line charging breaking current 125A

8. Operating sequence – First pole to clear factor 1.3

9. Supply voltage 220 V dc

10. Auxiliary circuit supply voltage 240 V dc

11. Air pressure 20.5 bar

12. Frequency 50 HZ

13. Mass 3800 kg

14. Rated current 1600 A

11. VARIOUS OTHER EQUIPMENTS

Shunt capacitors are used to provide compensation to reactive loads of lagging power factor.

Series reactors are used to reduce the short circuit current or starting currents. Neutral grounding resistors are used to limit the earth fault current.

Coupling capacitors are used to provide connection between high voltage line and power line carrier equipment.

Operating Voltage 230 V

Rated current 2000 A

Minimum short circuit current in bus bars 40 KV

Minimum phase to phase clearance 2.5 M

Number of horizontal levels of tubular bus bar/flexible bus bars 2.0 M

Height of tubular bus-bar of first level above ground 6 m

Height of tubular bus-bar of second level above ground 4 m

Tubular aluminium bus bar AL ASTMB241 4″IPS (International pipe standard)

VARIOUS SUBSYSTEMS IN SUBSTATIONS AND THEIR FUNCTION

S.NO. SYSTEM FUNCTION

1. Substation Earthing (Grounding) System – Earth mat – Earthing spikes – Earthing risers To provide an earth mat for connecting neutral points, equipment body, support structures to earth. For safety of personnel and for enabling earth fault protection. To provide the for discharging the earth currents neutrals, faults, surge arrestors over-head shielding wires etc. with safe step- Potential and touch potential.

2. Overhead earth wire shielding or lightning To protect the outdoor substation equipment from lightning strokes.

3. Illumination system (lightning) – For switchyards – Buildings – Roads, etc. To provide illumination for vigilance, operation and maintenance.

4. Protection system – Protection relay panels – Control cables – Circuit breakers – CT’s, PT’s, etc. To provide alarm or automatic tripping of faulty part from healthy part and also to minimize damage to faulty equipment and associated system.

5. Control cabling For protective circuits, control circuits, metering circuits.

6. Power cables To provide supply path to various auxiliary equipments and machines.

7. PLCC system power line carrier current system – Line trap – Coupling capacitor – PLCC panels For communications, telemetry, tele control power line carrier protection, etc.

8. Fire fighting system – Sensors, detection system – Water spray system – Fire protection control Panels To sense the occurrence of fire by sensors and to initiate water power spray, to disconnect power supply to affected region to pin point location of fire by indication in control room.

9. J Cooling water system – Coolers – Water tanks This system is required for cooling the valves in HVDC substation.

10. DC batteries sets and battery chargers Auxiliary low voltage DC supply.

11. Auxiliary stand by power System – Diesel generator sets – Switch gear – Distribution system For supplying starting power, stand by power for auxiliaries.

12. Telephone system For internal and external Communication.

12. BUS BAR ARRANGEMENT IN SWITCHYARDS

There are several ways in witch the switchyard can be connected in the electrical layout of generating station, receiving station or a switchgear in a distribution system. The following aspects in general affect the selection of the scheme:

1. Degree of flexibility of operations desired.

2. Importance of load and local conditions.

3. Economic conditions, availability, and cost.

4. Technical conditions.

5. Maintenance, safety of personnel.

6. Simplicity.

7. Provision of extension.

8. Protective zones.

DUPLICATE BUS BAR ARRANGEMENT

The duplicate bus bar system provides additional flexibility, continuity of supply and permits periodic maintenance without total shut down. In the event of fault o n one bus the other bus can be used.

While transferring the power to the reserve bus, the following steps may be performed:

1. Close tie circuit breaker, i.e. bus coupler. The two buses are now at the same potential.

2. Close isolators on reserve bus starting from far end.

3. Open isolators o9n main bus starting from far end.

Each pole of the circuit breaker comprises one or more interrupts or arc extinguishing chambers. The interrupts are mounted on support insulators. The interrupts enclose a set of fixed and moving contact. The moving contacts can be drawn apart by means of the operating links of the operating mechanism. The operating mechanism of the circuit breaker gives necessary energy for opening and closing of contacts of the circuit breaker.

13. RELAYS

Relay is a device by means of which an electric circuit (trip or alarm circuit) is controlled (closed) by change in the other circuit. Relays are automatic. The function of relay in power supply system is to recognize a start out and to initiate the operation of CB or other devices to isolate the defective elements with minimum disturbance to the normal power supply system. The must operate at required speed and stability to prevent the current and voltage to exceed their limits.

A few relays with their international codes are mentioned below:

S. NO. CODES TYPES

1. 27 Instantaneous under voltage relay

2. 99 Composite motor protection relay

3. 64 Earth fault relay

4. 87M Differential relay for motors

5. 50N Earth fault relays with times for time delayed operation

6. 95 Fuse failure relay

7. 80 Auxiliary supply for DC supervision

8. 80B DC supply control supervision

9. 80A Relay for mains

10. 500/L Triple pole over current definite term

11. 98 Trip circuit supervision relay

12. 87 Triple pole circulating current

13. 63 Auxiliary relay for transformer fault indication

14. 33B Auxiliary relay for stop

15. 25 Check synchronizing relay

16. 52SC Instantaneous high set over current relay

17. 2B Static time delay relay

18. 51RYB Single pole (IDMTL) Inverse definite Minimum time over current relay.

THE FAULT CLEARING PROCESS

During abnormal or faulty conditions the relays sense the fault and close the trip circuit of the circuit breaker.

As the relay contact close, the trip circuit is closed and the operating mechanism of the CB opens and an arc is drawn between them. The arc is extinguished at some natural current zero of a.c. wave.

o Fault Occurs: – As the fault occurs the fault impedance being low, the currents increase and the relay get actuated. The moving part of the relay moves because of the increase in the operating torque. The relay takes some time to close its contacts.

o Relay contacts close, the trip CB closes and trip coil is energized.

o The operating mechanism starts operating for the opening operations. The CB contacts separate.

o Arc is drawn between the breaker contacts. The arc extinguished in the CB by suitable techniques. The current reaches final zero as the arc is extinguished.

SWITCHGEAR

The switchgear constitutes all parts or equipments of power plant whose function is to receive and distribute electric power. It comprises of the following:

· Assemblies of switching apparatus

· Protective and indicating metering devices

· Interconnecting bus bar systems and relevant accessories

Functions of Switchgear: –

The functions performed by switchgear are listed below: –

· To facilitate redistribution of load, inspection and maintenance of system.

· To localize the effects of faults by operation of protective equipment so automatically disconnect faulty part from the system.

· To break efficiently short circuits without giving rise to dangerous conditions.

The switchgear has the responsibility of transmitting the power from the generator to the grid. However plant also needs power for its working. It is mandatory not to use more than 10% of the power developed by the plant. So that all the auxiliaries and lightening system of the plant must be designed in such a way that there consumption is in the limit.

There are two bus bars placed in ducts, which supply power to the switchgear and are fed by two station transformers ST-I and ST-II. The rating of these identical bus bars is 6.6 KV, 3150 Amps, 50 Hz. These are known as C-I and C-II station buses respectively. The material of conductor is Aluminium. C-I station bus feeds US-IA & US-2A buses and C-II feeds US-IB & US-2B buses. C-I & C-II buses are also interlinked. These unit service buses feed the different kinds of load.

The auxiliary voltage for the ac supply system is 6.6 KV and 415 V. 6.6 KV supply system is provided with high resistance grounded neutral with provision of alarm/ trip. 415V auxiliary supply system has solidly/high resistance earthed neutral. All the electric motors of 150 KW rating or below are rated at 415 V and motors above 160 KW are rated at 6.6 KV.

GENERAL ELECTRICAL SUPPLIES IN THE PLANT

Electrical Auxiliary System

· AC Auxiliary supply system

· DC supply system

AC auxiliary supply system is used to feed all the AC auxiliaries installed in the plant.

The DC supply system which consists of 220 V DC, 110 V DC,

+/- 24 V DC, 48 V DC etc. is used for control supplies as required for system control and protection equipment.

Simple Electrical Equipment in Daily Life
electric resistance

Research shows that every year hundreds of people get killed each year in accidents which happen because of electrical failures and fires from short-circuits. They occur predominantly due to the ignorance of people who do not have the expertise to locate and rectify such errors, and also because many of them are too reluctant to seek professional help out of the misconception that the issue is not an important one. Some handy electrical test equipments must be kept at home for emergency purposes. Although it is still advisable that you get immediate professional assistance at the quickest, these tools could at least become useful to those who more or less have a fair idea regarding electrical testing.

Analogue Ammeters: They are used to measure the flow of current. The current level is displayed on a dial, in amperes, with the help of a pointer. This is helpful in determining the correct amount of power needed to run any electrical good.

Analogue Multimeters: As the name implies, this is required to measure important aspects regarding the flow of electricity like voltage, resistance and signal power and gives accurate reading in a very short span of time.

Analogue Voltmeters: They are used to determine the voltage of current passing through the circuit and also notify the user if there is a drop in voltage. The mechanism is easy to read with a simple needle point pointing the current voltage on a dial.

Circuit Tracers: This is also known by the name of signal tracers and is probably the most important of these testing devices, because they help in locating the fault in the circuit in the first place. They help to identify common problems like short circuits and breakages.

Clamp Meters: This equipment is very useful to electricians because it allows the user to measure electricity from a circuit without having to disconnect anything from the main wires. It gives all the necessary readings and help in identifying if the mechanism is under a heavy load.

Field Intensity Meters: These devices are used to measure the strength of any kind of electromagnetic field, and are very useful in detecting piping and equipments which are hidden from view or ferromagnetic ores buried in the earth.

Phase Meters: These are used in circuits where electricity is flowing in from three phases. They include instruments like Phase Testers and Phase Rotation Meters and provide accurate reading from all the three phases simultaneously.

Ground Resistance Testers: These equipments are used to test electrical grounding systems to determine the flow of power in between earth and the conducting objects. They are complicated to read and it is advisable that they be used only by those who have a sound knowledge of electrical testing equipment.

These electrical test equipments make the life of users comfortable and hassle-free.

3 Benefits of Elenco Snap Circuits Jr 100 Electronics Kits
electric resistor

Few things are more exciting and rewarding than building something that really works. Most kids love the challenge of building their own electronic devices, whether it’s a simple robot or a bedroom alarm to keep out little siblings.

Various electronic kits are available, and the potential benefits go beyond the finished product. For a start, it’s a hands-on opportunity to become familiar with some terminology. By high school, science classes often include an introduction to electronics concepts, including circuit diagrams, resistors, and diodes. Kids who build electronics learn about basic physics, electricity, and how electronic devices work.

These are pretty challenging abstract concepts, which can be brought to life by using electronic kits to connect the right parts. For instance, rather than looking at a computer and seeing only a box with a screen, electronics enthusiasts can get their hands on real parts to help them see and better understand the inner workings and infinite expansion possibilities.

Electronic kits contain multiple parts, diagrams, and instructions. To be successful and create a working device, kids need to follow instructions systematically. Starting with electronic kits for beginners, there are multiple levels of difficulty to explore. Kids learn how to read instructions carefully and how to interpret schematic diagrams, developing both spatial and logical skills.

Building electronics requires persistence and patience. Starting with simpler kits allows these skills to be learned gradually. Snap-together versions are more gratifying for beginners, who are getting accustomed to the parts and language. Later, more difficult assemblies become interesting.

Electronics does not have to be a solitary pursuit. Some children’s kits, such as the Elenco Snap Circuits Jr 100, include interactive games to be played with friends. While most beginners start with electronic kits, there are endless possibilities for more advanced enthusiasts. In fact, there are clubs and online hobby groups. As projects get more complicated, kids can move on to more advanced electronic kits. Elenco Snap Circuits Jr 100 is a great place for beginners, but after mastering it, kids can advance to Elenco Snap Circuits 300 and Elenco Snap Circuits 500. There are also other brands available, such as Thames and Kosmos.

Have a science fair coming up? Electronic projects are an interesting way to explore physical concepts. Not only can a budding scientist build his or her own electronic device, but then there are many possible experiments that can be done with instruments like photo-electric cells, electromagnets, and generators.

Even beginners can make a wide variety of devices using Elenco Snap Circuits Jr 100, from radios and doorbells to a flying saucer. With so many options and parts, kids can experiment to build their own creations. Then there are electronic kits available that are specifically designed with one purpose in mind, such as making robotic vehicles, hydroponic gardens, race cars, weather observation centers, motorized dinosaurs, and digital recording instruments.

Most beginner electronic kits are solder-free, so they are straightforward and accessible for children. With practice and advancing skills, older kids can learn how to solder. Once this is mastered, there are many intriguing projects to make. Light dimmer switches, LED displays, combination code locks, and digital clocks make nice additions to any room. So next time you’re looking for an interesting and educational activity, think about an electronic kit.

Description of an Attenuator Voltmeter
electric resistance

An attenuator voltmeter is defined as an instrument used for measuring the electrical potential difference, also known as voltage, between two points in the electronic circuit of different attenuators such as an optical attenuator and digital attenuator. Voltage is referred to as the electric potential energy per unit charge. It is responsible for driving a current from one electron to another electron. The corresponding International System of Units (SI units) for voltage is volt. The attenuator voltmeter can measure direct current (DC) or alternating current (AC).

In technical terms, all voltmeters are considered ammeters. This is because they measure electric current rather than voltage. Voltage is only measured when the electric current is transmitted in the electric circuit via resistance. Voltmeters are originally called galvanometers. Voltmeters are also known as multimeter because they also measure resistance and current.

The two types of attenuator voltmeter are the digital and analog voltmeters. A digital voltmeter usually features a voltage reference, an analog-to-digital converter, a power supply and a digital display unit. This kind of voltmeter directly displays numerals through the analog-to-digital converter. The digital display system could be a light emitting diode (LED) or a liquid crystal display (LCD) panel. There are several factors that may affect the accuracy of measurement of a digital voltmeter. Some of these factors include temperature and supply voltage variations. Users now prefer a digital voltmeter over an analog one because of its accuracy. To maintain its accuracy, periodic calibration of the voltmeter against a voltage standard is recommended.

Basically, an analog voltmeter contains a galvanometer, or current meter, which is in series with a high resistance. An analog voltmeter displays values on a dial, usually with a moving pointer or a needle. This kind of voltmeter may be employed to locate excessive resistance that may indicate an open circuit or ground. The impedance is the internal resistance of an analog voltmeter. This is commonly expressed in ohms per volt. An analog voltmeter is connected in parallel with the circuit being tested. This allows the meter to tap a small amount of electric current.

An attenuator is defined as a device which reduces the amplitude or power of a signal without distorting the signal’s waveform. This electronic device is used in audio and radio signal circuits. To measure the voltage difference in the attenuator circuit, the positive input terminal and negative input terminal are connected to a location in the electric circuit. When the attenuator voltmeter is already attached to the electric circuit, the circuit will be disturbed, which leads to change in the voltage being measured. The disturbance should be negligible enough so that it will not create significant change in the voltage. Some of companies that manufacture voltmeters are Onesto Electric Co. Ltd., China Electronics Zhejiang Co., Sunlogic Electrical Appliance Ltd., Tons International Ltd., People Ele. Appliances Group, Zhejiang Taizhou Wangye Power Co. Ltd., Shanghai Chenchang Power Technology Co. Ltd., Shaanxi Xieli Photo Electric Instruments Co. Ltd., Dongquan Zhengyang Electronic Mechanical Ltd. and Chac Technology Co. Ltd.