What is Vk and Imag i.e Knee point voltage & Magnetising
Current?
How to calculate above values?
How to define accuracy class 5P10?

Answers were Sorted based on User's Feedback



What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / zahid ali

Vk is knee point of CT it mean when 10% increase in voltage
varies the current 50% at that point we determine the knee
point voltage. In othe words excitation test of CTs,
connect a single phase variable power supply leads to the
CT seccondary leads k & l or s1, s2 along with ampere meter
& voltage meter & than apply voltage start from zero &
raise incremental simultaneously draw a graph on each
increments by plotting current on X-axis & voltage on Y-
axis.
Magnetizing current is those which is used in core & tank
of transformer due to leakage flux, which is furthur
devided into hysteris losses & eddy current losses.
We can find magnetizing current by open circuit test.
5P10 means: 5 for composite errors in percentage, P for
protection & 10 mean overlaod factor by multiply 10 times
in others words CT will not saturate by passing 10 times
higher current.

Is This Answer Correct ?    84 Yes 9 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / v .selvakumar

knee point means at which the core tends towards
saturation .magnetising current means to produce flux in
the core it will take some current it is called magnetising
current.before knee point the graph between Vk and Imag
will be linear,at which point linear curve getting
disturbed .

Is This Answer Correct ?    31 Yes 9 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / ugrasen

Dear friend,
Knee Point voltage is nothing but a point at which the CT
saturates. Thatsy its always better to design the CTs which
can operate without saturation even at a voltage appears in
the CT during fault condition. Pls find below the following
formula for calculating the Knee point voltage.
The formula for Knee Point Voltage is:

Vkp = K * If/CTR * (RCT + RL + RR)

in which,

K = Constant, conventionally taken as 2.0

Vkp = The minimum Knee Point Voltage

If = Maximum Fault Current at the location, in Amperes

CTR = CT Ratio

RCT = CT Secondary Winding Resistnace, in Ohms

RL = 2-way Lead Resistance, in Ohms

RR = Relay Burden, in Ohms
ugrasen.vishawakrma@gmail.com

Is This Answer Correct ?    12 Yes 0 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / gunasekaran

if it is 5P20 we can calculate from following formula
1.2*VA*ALF/rated secondary current.
magnetizing current it will be mA it may be .5 or .7 of current

Is This Answer Correct ?    13 Yes 3 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / savanth

Formula for vk is as follows

vk=if(rct+2*rl)

where if is fault current
rct is ct secondary resistance rl is lead resistance

Is This Answer Correct ?    12 Yes 3 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / yogesh

How to consider or calculate valu of Rct at the time of detail engineering???

Is This Answer Correct ?    0 Yes 0 No

What is Vk and Imag i.e Knee point voltage & Magnetising Current? How to calculate above valu..

Answer / pradeep maurya

Dear friend,
Knee Point voltage is nothing but a point at which the CT
saturates. Thatsy its always better to design the CTs which
can operate without saturation even at a voltage appears in
the CT during fault condition. Pls find below the following
formula for calculating the Knee point voltage.
The formula for Knee Point Voltage is:

Vkp = K * If/CTR * (RCT + RL + RR)

in which,

K = Constant, conventionally taken as 2.0

Vkp = The minimum Knee Point Voltage

If = Maximum Fault Current at the location, in Amperes

CTR = CT Ratio

RCT = CT Secondary Winding Resistnace, in Ohms

RL = 2-way Lead Resistance, in Ohms

RR = Relay Burden, in Ohms
pkmauryain@gmail.com

Is This Answer Correct ?    0 Yes 1 No

Post New Answer

More Electrical Engineering Interview Questions

In n high voltage 11kv system What happened if 1 of CT cable (IDMT) loose.Will e/f or o/c trip.please explain detail

1 Answers  


DISCUSS THE SHAFT MOUNTED D.C. GENERATOR ,BASED ON EXCITATION SYSTEM IN ELECTRICAL SYSTRM

2 Answers  


What is the difference between surge arrestor and surge capacitor?

2 Answers   Shreem Electric Ltd,


why rating of transformer is in kva instead of kw?

3 Answers  


Whag is the PS class of accuracy of CT?

3 Answers  






What are types of HT Motors.

1 Answers  


what is feeder bay?

0 Answers  


How to calculate the transmission losses incase of overhead transmission lines?

6 Answers   Jindal,


how we select fuse rating for motor?

6 Answers  


my motor rating is 800HP, 128Amps, 3.3kV. What is capaitor bank i can use for PF improvement to 0.990?

3 Answers  


which is better 50 HZ supply or 60 HZ supply?

6 Answers  


Is it recommended to apply H.pot test for new cables segments after terminations or joints, however, this cable has been tested before at the manufactor by the vendor ? or only we can apply megger tests ?

1 Answers   Centroid,


Categories
  • Civil Engineering Interview Questions Civil Engineering (5085)
  • Mechanical Engineering Interview Questions Mechanical Engineering (4451)
  • Electrical Engineering Interview Questions Electrical Engineering (16632)
  • Electronics Communications Interview Questions Electronics Communications (3918)
  • Chemical Engineering Interview Questions Chemical Engineering (1095)
  • Aeronautical Engineering Interview Questions Aeronautical Engineering (239)
  • Bio Engineering Interview Questions Bio Engineering (96)
  • Metallurgy Interview Questions Metallurgy (361)
  • Industrial Engineering Interview Questions Industrial Engineering (259)
  • Instrumentation Interview Questions Instrumentation (3014)
  • Automobile Engineering Interview Questions Automobile Engineering (332)
  • Mechatronics Engineering Interview Questions Mechatronics Engineering (97)
  • Marine Engineering Interview Questions Marine Engineering (124)
  • Power Plant Engineering Interview Questions Power Plant Engineering (172)
  • Textile Engineering Interview Questions Textile Engineering (575)
  • Production Engineering Interview Questions Production Engineering (25)
  • Satellite Systems Engineering Interview Questions Satellite Systems Engineering (106)
  • Engineering AllOther Interview Questions Engineering AllOther (1379)