voltage drop

There are the following methods for solution:

a. Increase de tap of the feeding transformer.

b. Increase sd mm2 of the feeder.

c. Put an ammount of KVAR to increase de power factor .

I hope this may help to you.

Gustavo Tello

if u increase da tap of the feeding TRX, other equipment may have some impact, better dont alter tap

I can't believe that; only 390 amps through a 300 sqmm cable of length 450 mt gives a voltage reduction of 5.5% !!!!!!!!! Why?

What type of cables you are using? and what is the power factor of P2?

Some more informations are required for analysis

1) COPPER CABLE /Aluminium cable

2) Power factor of load.

However ,on certain assumptions i got the following results

1 x 3.5 core 300 sq.mm Aluminum cable--390 Amps upf------volts drop 9.5%

1 x 3.5 core 300 sq.mm copper cable--390 Amps upf------volts drop 5.7 %

2 x 3.5 core 300 sq.mm copper cable--390 Amps upf------volts drop 2.7%

2 x 3.5 core 240 sq.mm copper cable--390 Amps upf------volts drop 3.4%

we can give you proper solution provided you give more information like material of cable ,no of runs,method of laying,restricted Voltage drop in %,load pf etc

any further help you can contact .

Dear Sir Ramvinod

My self syed working in DUBAI with EMCO Group

I am fresher here.........My job profile Low voltage designing, Preparing BOQ, tendering. I am using voltage drop formula but i am not sure either this is right or wrong (1.732xKxLxI)/(d2)

K = Resistivity of conductor = 0.00893 (mm²xOhm/m).

Will you please sugest me for calculation of voltage drop and cable size and how to select circuit breaker trip rating.

i will be very thankfull to you

Best Regards

Syed

Dear Mr syed

Thank you for referring.

Please send your problem to "ramesh.cuppu!gmail.com" such that I can send solution.

hi prabhu, u have not given enough detail, i have worked out by following inputs and got the following results from our softwere, check it out, if u have give the actual i/p i will worked out for u.

INPUT PARAMETERS

Install Type Air Cable Type Three Core Run Length 450 m Cable Arrangement Horizontal Flat Spaced (2De) Depth null m Temperature 45 °C Thermal Resistivity null °Cm/W Phase 3 Voltage 400 V Current 390 A Power null Power Unit null Voltage Drop 3% Frequency 50 Hz Power Factor .9

RESULT - 3C/CU/XLPE/SWA/PVC

Size, No of Circuits, Voltage Drop (V), Voltage Drop % (V) (a)50, 11, 11.61, 2.9 (b)70, 8, 11.32, 2.83 (c)95, 6, 11.47, 2.87 9d)120, 5, 11.3, 2.83(d) 150, 4, 12, 3 (e)185, 4, 9.92, 2.48 (f) 240, 3, 11.19, 2.8 (g) 300, 3, 9.44, 2.36 (h) 400, 3, 8.29, 2.07

i think dis will help u.

Let me guess the 450 meter run has a bad splice in it

Size up your wire for the drop, expensive. If this circuit has a supply transformer

move to higher voltage taps, or install a transformer at the end to

adjust the voltage drop.

Good luck,

James

Hey prabhu,

please don't try to transfer 400 volts through anything. Put that 400 volts across the load you're dealing with. As far as cable size, a good rule is to use the diameter of 750 circular mils per ampere or 6.28 times 10 to the 18th # of electrons through your cable and you'll be just fine. just kiddin'.....don't try to count those electrons. The cable you might be using may be a little small and since most metals have a positive resistance coefficient, if you're heating that cable, you're driving up its resistance. That may be the reason you're getting a higher voltage drop across your cable load.

RT Pokin