how to calculate knee point voltage of current transformer?
- 20 Answers
- 149756 Views
- Bhel, Bhilai, Jackson, I also Faced
- E-Mail Answers
Answer Posted / pankaj joshi
I am not familiar with the term saturation test but it seems
from the above posts like an exciting current test to
obtain the knee-point of the CT. With this test you can also
obtain the exciting curve (mag-curve) of the CT.
You'll need a variable voltage, (easiest obtain from a
variac - must be able to obtain the suitable voltage) a
voltmeter, an ammeter, a pencil and paper.You'll have to
measure the voltage and the current while you do the test.
Apply the voltage to the secondary winding with the primary
and other windings being open-circuited. Increase the
voltage until you reach a point where a small increase in
voltage results in a big increase in current.
Now slowly decrease the voltage to a few measuring points,
while you measure the current. (write it down) Something like:
205V - 1.1A
200V - 0.6A
190V - 0.238A
180V - 0.149A
170V - 0.114A
150V - 0.08A
125V - 0.061A
100V - 0.049A
50V - 0.028V
25V - 0.017A
0V - 0A
You have to decrease your voltage slowly to zero volt to
demagnetize the CT-core.
BEWARE The knee-point voltage will depend on the size and
class of the CT, and it can be very high on some CTs
(several hundreds of volts) Be very cautious, you will be
working on live equipment during the test.
Now you can just plot the current and voltage values on a
graph. This is the mag-curve of the CT. IEC classify the
knee point voltage as the point where a 10% increase in
voltage results in a 50% increase in current.
| Is This Answer Correct ? | 50 Yes | 10 No |
Post New Answer View All Answers
what is the principle of operation of tungstun bulb ??
what is vtg limit of earth and neutral at transformer side?
Can XLPE/SWB/PVC (P3) 7C X 2.5mm2 be replaced by Can XLPE/SWB/PVC (P2) 7C X 2.5mm2??? P3 vs P2
in my industry we are using 3 step up transformers for induction heaters..i.e 415/580v and other are 11/440v.in power consumption does a step trnsformer makes any difference compared to step up?? plz explain
Some times to change of DOR of a motor, interchange of R & B is not effected and RYB take same current, but interchange of R&Y is effected ie change the DOR. My doubt is what is the problem in motor and how it is happen.
How we can calculate the life of Lead acid battery
in shunt clippers why a resistor is used in sereis with the input
what types of electrical & mechanical test conducted in switchyard?
what is the major difference between LIBBP & HIBBP.. which one is most preferable..
i have a 1500kVA transformer what is the kWH meter i need to use?
What is Servo Ventilated Motor?
what are the precuation should be taken ahen installing power transformer,circuit breaker,current & potential transformer
Why is a synchronous motor always star connected??
What is float cum boost charging system?
I have a small system with two motors that are running on 380 vac, 60 hz. These motors are expensive and I usally get them from Brazil. I am adding another motor to the system, but I want to purchase a 480 vac, 60 hz motor to use. It will be on a VFD that is rated fro 380 thru 480. Is this posible and will I have to use a larger motor and derate it?
