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.

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 .

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

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

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

Answer / yogesh

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

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

deisel generators all elcetical calculation formule's

1 Answers  

what is lumped and distributed elements?

0 Answers  

what is the rating of Insulation tester for measure 15 KW, 3 phase 415V 50 HZ induction motor?

2 Answers   ABB,

two parallel conductors are carrying the current in the same direction.which of the following statements is true? (a)there is arepelling force between the conductors (b)the force increases when the distance between the conductors is increased (c)there is an attaracting force between the conductors (d)the force increases when the distance between the conductors is decreased

1 Answers  

what are the specifications we must look at to select a relay for any capacity motor?

0 Answers  

what is the frequency of direct current(dc)?

12 Answers   Cognizant, University,

What are the two types of compensation?

0 Answers  

What is the most accurate way of testing ELCB?ELCB is better than RCD?

0 Answers   GECO,

what is the eight bit unit?

0 Answers  

What is the function of induction motor when low voltage is apply.

6 Answers  

what are factors to be consider to design a HT & LT motor?

1 Answers  

can anyone help me regarding bout Electrical designs and calculations .. which text book should i follow as i am a trainee engineer.Description of my work which is Electrical designs like cable sizing, lighting, lightning, Gensets sizing, motor sizing, transformer sizing, generator sizing, circuit breakers, PDB MCC PCC SLDB MLDB panels, Single line diagrams mainly, substation desings, cable routing and layouts, reactive power compensations, power factor improvement, voltage drop calculations, power generations, power transmission, power distributions all calculations.Please help me

3 Answers