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Power Lines Protection
Why the 1st zone of protection relay is 90% not 100%?
ashokumarrk
- Nov 14th, 2010
Zone-1 protection is 80% in (NTPC, POWER GRID, NPCIL, NHPC, BBMB....) bcz we have consider the errors in CT, PT and also the line length. Datas provided should be same as the actual, but it wont. In order to compensate all these Zone-1 protection is 80%
pradipsabar2009
- Jul 29th, 2010
If we consider the 100%, 100% in the sense there is another CB present there. so there is a dilemma which CB should operate first. Hence the first zone of protection is never 100%
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Transformer induced emf
Is the transformer induced emf E1 and E2 in same phase or in opposite phase? Explain Why?
ripago
- Nov 28th, 2010
It depends on winding direction between primary and secondary coil ( this is so called polarity). If winding direction of primary and secondary coil same, then E1 would be in phase with E2. but if opposite then EMF also would be opposite (180 deg.)
kirank_239
- Mar 31st, 2009
The voltage induced in the primary and secondary windings is due to the same flux i.e., the primary flux. Hence E1 and E2 are in same phase
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Series Connection
If 100w & 50w bulb connect in series and if we supply 440v then what happen, which one glow first?
veerateja
- Dec 17th, 2010
The two bulbs will glow at a time bcoz the ckt should close the path through the second bulb also mean while the electricity(electron) speed is nearley equal to light speed.
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Is it possible for a feedback surge to travel over a wireless connection? Would the answer be different in a vacuum?
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Potential Transformers Applications
What are the applications of potential transformers other than metering and under voltage protection?
Raman Jain
- Dec 29th, 2010
There are numerous applications of Potential Transformers .1. For Metering Purpose.2. Required for Synchronisation of Feeders / Generator with Grid.3. For Feed back of AVR.4. Distance Protection of fe...
ripago
- Nov 28th, 2010
1. Over/Under Freq. Protection2. Syncrhonizing Generator to Grid.3. If you don't have spare of PMG then you can use this PT for AC Power supply to the excitation Unit of your own Genarator.
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Motor Vibration
What can be the possible causes of Vibration in HT motors?
Raman Jain
- Jan 2nd, 2011
Vibrations in HT Motors may be due to several reasons :1. Mis-alignment 2. Worn Bearing3. Loose foundation bolts.4. Unbalance rotor etc.
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Reactive Power
How much reactive power does a generator of rating 3.5MW generate?
Raman Jain
- Jan 3rd, 2011
The reactive power , Generator can supply, can be determined by the Capabilty Curve of the Generator , supplied by the manufracturer.This is a design criterion.
raviiisc
- Sep 8th, 2010
Generally the Alternator or Generator is rated in MVA format rather than MW format.The reactive power supplied by the generator is then decided.I think the questioner thinking about the ratings provid...
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Power Plant
What is the processing of power plant and what are the equipment used for coal handling power plant?
Raman Jain
- Jan 3rd, 2011
There are various equipments used in the Coal Handling Plants :1. Wagon Tipplers : to unload the coal wagons2. Stacker - Reclaimers : stack and reclaim the coal in/from stock yard.3. Conveyor Belts : ...
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DG Set Tripp
What will you do when D.G. set gets tripped?
Raman Jain
- Jan 3rd, 2011
First see at what indications D.G set get tripped. Find the cause and rectify . Than again start the DG set.
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AC Generator
To induce EMF, either field has to rotate or rotor has to rotate. In Alternator, AC supply is given to the armature to produce rotating magnetic field. The rotor is rotated by the prime mover. Then how will EMF be produced in an alternator. Explain the working principle of alternator in detail?
manilal.r
- Jan 2nd, 2011
Like a DC generator, an alternator also has an armature winding, but there is one importent difference between two, in a DC generator, the armature winding placed on rotor in order to convert AC? to ...
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Dielectric Strength
What is dielectric strength?
Harish P. Girhe
- Jan 4th, 2011
Material can be conductive or non-conductive. It depends on its di-electric property of that material. Di-electric means property of an material to oppose flow of electrical current. For better condu...
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Wattmeter Circuit
Why pressure coil is named so in wattmeter circuit?
Harish P. Girhe
- Jan 4th, 2011
Current & voltage both requires for utilisation. Current depents on device for its energirising. Each individual device reqiures currents for its own working. But voltage is applied across device term...
prabhat.gaurav
- Dec 8th, 2009
As pressure in pneumatic sysytem is analogaus to voltage that's why the coil connected to supply voltage in wattmeter is called pressure coil.
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Line Wire
When we touch the line wire or supply wire we get shock. What is that? Is it voltage or current or something else?
Harish P. Girhe
- Jan 14th, 2011
Voltage is responsible for electric shock. In house wiring only 5 or at least 10A current flows but potential diff. of 230V get disturb our nervus system. Human body(dry) can sences above 80volt without any danger.(Not every time)
_punjabi_
- Aug 29th, 2010
When you happen to touch the live part of the supply, then your body acts as a part of the circuit and of the Supply system is not grounded and if equivalent resistance of your body is less than that ...
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AC & DC System Components
In DC only resistive component exists where as in AC system resistive, capacitive & inductive component exists. Why its so?
Harish P. Girhe
- Jan 16th, 2011
It is because of loads reactance. Reactance either capacitive or inductive that depends on frequency. XL=2(pi)FL Where f is supply frequency. In DC supply f=0 hence XL=zero. Similarly Xc=1/2(pi)F.C=0 in dc supply. Thats why only resistance is to be present in DC system.
arjun karnati
- Jan 19th, 2009
Good question. to answer this question first of all we need to study the terms resistance, inductance, capacitance on atom level. Generally what we know is Resistance: which opposes the flow of electr...
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Alternators
Which slots does a stotor of an alternator rarely uses?
veerateja
- Jan 22nd, 2011
Open type slots are used in synchronous motor or alternator because to reduce the leakage reactance and leakage flux,which increases if closed slots are used.
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Fan Condensers
Why condensers are used in fans?
veerateja
- Jan 28th, 2011
Fan condenser is just used to create starting torque by increasing the current lead through the starting winding ,after started running of 1-phase motor we can remove capacitor even after removing the...
shafialuva
- Sep 15th, 2010
The most common motor used in a normal household electric fan is a single-phase induction motor. When first switched on such a motor needs to use a "starter" winding, in addition to its ma...
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Location of Circuit Breaker
The designed capacity of the transformer was 1600 watt. The utility company is in shortage of such wattage, so they used two 800 watt transformers in parrallel. The utility company uses only one circuit breaker after the parallel connection. The custmer says it is not correct there should be two separate breakers for each transformer. Which connection is accseptable.
VEERENDRAKUMAR.CH
- Jan 28th, 2011
when one CB used:if fault occurs on any one transformer that fault will effect the another transformer so two CB must be needed
appersundaram
- Mar 27th, 2010
We can use two circuit breakers in parallel, but we should connect the mastertrip relay contact of either breaker should be wired to trip the other breaker as well.
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Two Phase Induction Motor
What is a Two Phase Induction Motor?
sandeep.psg
- Mar 2nd, 2011
2 phase Induction motor(IM) has 2 sets(phase) of coil displaced electrically by 90degree. In practise we dont have dedicated 2 phase IM because of not supplying Constant Torque. But we do have so...
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Transformer Secondary Voltage
Why is it that the secondary voltage of a step-up transformer is lesser than the primary voltage of a distribution transformer?
Jai Pradeep
- Mar 13th, 2011
The primary voltage of a distribution transformer decreases due to increase in length of the conductor between step-up and distribution transformer.
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Power Consumption
A heater of 1500w, bulb of 100w & 40w are connected respectively as sequence as stated above across supply. What effect will be observed on illumination/power consumtion of all of them?Now sequence is changed as bulb of 40w then heater & last bulb of 100w. What effect will be seen on illumination/power consumption of all of them?
Jai Pradeep
- Mar 13th, 2011
In the first method?the heater with 1500Watts connect, i.e large load is connected in first of a sequence so most power consumed by this. The 100 & 40 watts bulb will illuminated lighter.In the seco...
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