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T/F Differential Protection
Can differential protection operate while its only one side is energized or being energized (HT side in this case)? When trying to energize a 132/11KV t/f from HT side when its differential protection operated while its LT side breaker was still open? Was it because of starting inrush current or t/f tap position?(It has an auto tap changer on HT side & while it was being energized tap position was...
pashwuee
- Apr 2nd, 2010
Transformer tripped due to inrush not because of tap changerNumerical relays take care of harmonics during inrush current so transformer does not trips.If it is tripping setting needs to be checked
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Phase Advancer
Explain What is Phase Advancer?
mallick.subratkumar
- Apr 8th, 2010
It is like an power factor improvement deviceIt maintains the phase sequence of the linelike lag-lead compensator.
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Potential Transformer
What is the function of a potential transformer?
dhands
- Jun 6th, 2010
Potential transformer is used to measure the high voltage. It is nothing but stepdown transformer. In our metring systems are dsigned only for 110 v or 220 v but we are using 11000, 22000, 33000, ect. For ex PT input is 11000 v but output is 110v.
deepanshu_jadon
- Mar 10th, 2010
Potential Transformer is used to measure VoltageIt is used in protection
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Vibro Motor Direction of Rotation
Two electrically operated Vibro Motors are fixed in parallel direction in vibrating feeder. What is the direction of both Vibro Motors?
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Main Switch
What the name given for to connect the main switch supply to the various appliances?
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Transformer Core Loss
What is core loss in a transformer?
veerateja
- Jun 16th, 2010
Eddycurrent and hysteresis losses are two core losses in transformers. Eddy currents are minimised by laminating the core where as hysteresis losses are minimised by using pure silicon steel. The two losses are similar in all rotating electrical machinery.
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Harmonics Deduction
How can we control or deduct harmonics?
veerateja
- Jun 18th, 2010
By improving the power factor by using capacitor or by synchronous condenser the harmonics can be reduced.If three phase is used the harmonics can heat the neutral wire ,so it is better to keep the diameter of neutral wire more than the other phases.
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AC line Power Loss
High voltage is traded off for lower current in an AC line transmission. High current would require thicker cables, hence losses. How much can the voltage be increased to have a lower power loss? What is the ratio b/w current and voltage (p = I^2 * R).
Jayrod
- Jun 21st, 2010
"High current would require thicker cables, hence losses." - I disagree. The larger the cross-sectional area of a cable, the lesser the resistance (remember the formula for resistivity). Thi...
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How do you measure the leakage current in a house wiring?
bittu123
- Nov 9th, 2011
Two method suggested above is right.
Beside those,
Measure current through live wire and neutral wire at main switch board of ur house and find the differences.mani777
- Jun 22nd, 2010
There are two ways for it. First one is to keep all lights and other domestic electric appliances OFF for an hour and record the energy consumption in the energy meter. Calculate current from it. Seco...
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Power Factor
A powerplant has 8 gensets operating in grid parallel mode. In one genset sometimes there is pf variation and kvar variation. The plant operates in pf mode. When this variation is onbserved the load is stable, voltage is also stable, freq and genset speed is also stable. How will you check the functioning of pf card. What shall be the ideal output vdc of the pfc, from there it is input to avr.
mani777
- Jun 23rd, 2010
1. pf...........cos #=watt/voltage*current2. pf is cos thita between v & i3. pf is apperent power/realor reactive power.
saginala13
- Jun 19th, 2010
here the variation in the power is is the pf factor of load, in generating station all alternators are connected to a busbar, and load is connected to bus bar so the load will be shared by all generators
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Earthing Resistance
What will be the body impedance of human body>What will be the maximum allowable earthing resistance value?
bkashwin
- Jul 1st, 2010
The resistance of human body is 1000 ohms and allowable resistance is 1000 ohm for some time.
csbalu
- Aug 29th, 2009
Human body impedence depends on the nature of the body and it varies appreciably between different sizes. The fatter the lower resistance.The acceptable earth resistance will be less than 1 Ohm - the lesser the better.
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Corona Effect
What is corona effect ? How this is avoided in transmission?
silverscythe
- Jul 2nd, 2010
Corona Effect is the high voltage electric discharge phenomenon that can be observed between two transmission lines or for that matter any two lines carrying electricity. This occurs generally when th...
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Insulation Value
What is the thumb rule for insulation value in bus bars, phase to phase and phase to earth for 11 & 33 kV system?
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Insulation Resistance Testing
When we apply the DC voltage thro' the digital Megger to test the IR value for cable/motor winding etc., we can see the digital display of the test equipment showing more than the applied voltage (for eg. if we select 500V dc, we can see 526V dc in the display) Why?
sinhasunilk
- Jul 3rd, 2010
When we measure IR value, we measure resistance of insulation of the circuit either w.r.t earth or w.r.t. to other phase.The digital display is resistance between the ckt and earth, not the voltage. I...
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Alternator
Why alternator is operated at lagging power factor?
How alternator responses with changing the load?sinhasunilk
- Jul 3rd, 2010
The Alternator has very little margin to run in the leading P.F. so far electrical stability of alternator is concered. If we operate generator at higher leading P.F. machine will become uns...
rajakumar1985
- Sep 9th, 2009
Since the Synchronous generator having the property of supplying the reactive power along with the real power, this can be operated in lagging power factor only. Suppose if it want to work with leadin...
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Inductive Loads
Why does inductive loads consume KVARs?
sinhasunilk
- Jul 3rd, 2010
Electrical load is of three types: Inductive load, Resistive load and Capacitive load.The power drawn in a circuit will depend on type of load, the power is supplied. The circuit which has i...
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3 Phase Motor
How can we test a 3 phase motor on single phase supply?How can we run a 3 Phase Motor on Single Phase supply for testing?How can we verify of a 3 phase motors' 6 wire & name them a1/a2/a3..b1/b2/b3 and c1/c2/c3 for connecting star delta starter?
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Earthing Standards
What is the standard for Cable sizing & Voltage Drop?What is the standard for earthing?
maxandrean
- Jul 5th, 2010
Standart Earthing Cable in practice is :1. For the cable size is 16 mm2 , the size is equal to the line cable.2. For cable size above 16 mm2, the size is half size of the line cable, but not less than...
salman_moazzam
- Feb 2nd, 2010
Depth to which you must dig. How much should be the amount of salt and charcole to be put. Especially in earthing we must go to the depth untill you get wet mud.
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Power Factor Panel
What will happen if 400 KVar Capacitor banks are on in manual mode and there is no load on mains?
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Vector Group
What is vector group of transformer? Why is it required?
raviiisc
- Jul 11th, 2010
Vector group is a big topic which comes in case of Three Phase transformer connections.There are some connections like Dd0, Dd12, Yy0, Yy12, Dy, Yd.......and so on.Here 180 degrees group,0 degrees gro...
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