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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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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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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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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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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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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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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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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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Main Switch
What the name given for to connect the main switch supply to the various appliances?
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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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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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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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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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What is the main Electrical IS rules?.
yuvaraj moorthy
- Mar 25th, 2010
ISO is international standard organisation and IS is Indian standarad ...ISO has IEC which is International Electrotechnical Commision will do the standarad for all equipments and each national interp...
vishwas_deshmukh
- May 6th, 2008
IS rules is international standrds rule adopted for any comissioning,erection,or any work we want to perform.They have some certain standads according to study of researcher by comparing all geographical and availabe technical parameteres in that concerning area.Which is suitable for any work.
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Core cables
generally we are using 4 core or 3.5 core cable for power supply ,in this practice we are connecting three different phase R,Y,B and Neutral to our 4 core or 3.5 core cable,but for our termination conveniences we have connected R phase to all 3.5 core of one cable,Y phase connected to all 3.5core of other cable and B to another and similarly individual cable for Neutral,in sort we use individual cable...
loganathan.1983
- Mar 19th, 2010
3 Phase 4 Wire termination is better because insulation, eathing. Heat is increased according to routing (undergrounding/outer) and load.
expertnayak
- Jun 12th, 2009
Due to use of bundled conductors it will give rise to sheath losses. Which will increase the temperature to overcome this use cross bounding. In overhead lines use both cross bounding and transposition to get a better result.
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Network Synthesis
Why the roots of the network function are +ve?
deepanshu_jadon
- Mar 10th, 2010
Roots of the network function should be negative for the stability of the function.For positive roots network function is unstable.
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3 Phase Motors
Why do 3 phase motors rotate in the opposite direction when any two phases are interchanged?
deepanshu_jadon
- Mar 10th, 2010
By the interchange of two phases Force acted in the winding inverse.if motor rotate clockwise then by the changing the two phases it start rotate in anticlockwise direction
M.Mohanraj
- Dec 8th, 2009
Magnitude is different in 3 phases so it is possible to rotate reverse direction.
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Phase Sequence
What happens when we change the phase sequence in 3 phase system?
R Raghavendran
- Feb 26th, 2010
Only the sequence of rotation of Magnetic fields changes, which causes a change in the rotor rotating direction accordingly.
SURAJTHEGREAT
- Feb 22nd, 2010
There is no change for ordinary devices,(behaves same as if the unvaried 3 phase supply is given) The rotation direction of the machines varies with variation in sequence of ac supply..
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LV Switchgear
Considering the short circuit fault, which switchgear is preferable, SFU OR MCCB? Which operates faster?
which one is popular in Indian Market and why? 2) Define SCPD. What is type2 co-odination?
3) Why the contactor rating is higher for the fuseless selection than for fuse selection? whether the ratinf of SFU or MCCB remains the same in both the cases?
4) If...veena_gyanchandani
- Feb 24th, 2010
2) SCPD - Short Ckt. Protection Device.eg - SFU.Type 2 coordination says that there should be no danger to personnel as well as no damage to the controller for downstream faults.Light contact welding ...
veena_gyanchandani
- Feb 24th, 2010
During short ckt. faults, the most reliable switchgear is SFU. It is fastest to operate and takes only few miliseconds. The operator just has to replace the fuse.MCCB is good for overload protection.
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Variable and Core Losses
Why copper is called variable loss & core loss is constant loss?
SURAJTHEGREAT
- Feb 22nd, 2010
Iron loss-When an electric current flows through a copper conductor (or any conductor), some energy is converted to heat. i(square)*r...this equation is obvious that iron loss depends on flowing curre...
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