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10 % increase in voltage gives you 50 % increase in excitation current is called knee point voltage. To measure this first demagnetise the CT and apply voltage gradually from secondary keeping primary winding open circuited. while doing this above phenomeneo will be obsesrved.
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Knee pont voltage- briefly distinguish?
The knee point voltage of a CT is the voltage at the "knee" of a I-V characteristic (if you increase voltage, and plot this voltage with respect to the current flow, you will see a logorithmic type response). The knee is usually specified as 10% distortion (ie, the voltage is 10% less than you would expect relative to the current flow). beyond the knee point, the CT is considered in saturation. This applies to amplifiers / transistors as well as CTs. Transistors used as ampifiers are operated in the "linear region", or the region below the knee point of that particular transistors I-V characteristic.
What is knee voltage and breakdown voltage?
Knee voltage (cut in voltage) :-The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage Breakdown voltage :-It is the minimum reverse voltage at which the P-N Junction can conduct without damage to the current
What is meant by cut in voltage in diode?
Cut in voltage (Knee voltage): The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage.
Zener knee current?
Not 100% sure, but I believe it's the reverse current at which a Zener diode enters breakdown. There is also the Zener max current which refers to the current that must not be exceeded if you do not wish to damage the device and also the Zener test current at which the Zener Voltage is measured. The test current usually lies somewhere (roughly halfway) between the knee and max current.
What is the difference between rectifier diode and zener diode?
A: They are both diodes. The difference lies in the application. A rectifier is used to rectify AC current into pulsating current. The zener diode is used to regulate a voltage source to the zener voltage when connected in the reverse direction. ************************************************************** If you look at the characteristic curves of a rectifier diode and a zener diode, you will see that they are similar, but the reverse curve of the zener has a much sharper bend at what is called the "knee". It is at this point on the zener's curve at which it operates.
Why you have to do current transformer knee point test?
we are not having anyother work, so only we are testing that.
Knee pont voltage- briefly distinguish?
The knee point voltage of a CT is the voltage at the "knee" of a I-V characteristic (if you increase voltage, and plot this voltage with respect to the current flow, you will see a logorithmic type response). The knee is usually specified as 10% distortion (ie, the voltage is 10% less than you would expect relative to the current flow). beyond the knee point, the CT is considered in saturation. This applies to amplifiers / transistors as well as CTs. Transistors used as ampifiers are operated in the "linear region", or the region below the knee point of that particular transistors I-V characteristic.
How do you perform no load magnetizing current measurement of transformer?
I am sure there is more than one way of doing this but what I am currently implementing in my own study of I_mag is the following: At no load perform an over excitation test where you vary the input voltage from 0 V and monitor the current flowing through the primary windings of the transformer. Over-excite the transformer until the rate at which current, I_in increases in the primary windings is relatively larger than the change in Vout , across the secondary windings (this is the point of saturation). Plot your results of voltage Vout (y- axis) against current I_in (x-axis) and you should come up with a characteristic B-H curve. (Remember that the B field is proportional to voltage and the H field is proportional to current from magnetic circuits theory) You are then to decide which point on your curve you will regard as the 'knee' point or the point at which the curve starts to deviate from the linear region. This 'knee' point will correspond to your I_mag. While I_in is not necessarily equal to I_mag at no load, at the knee point on your curve these two currents will be approximately equal.
What is knee voltage and breakdown voltage?
Knee voltage (cut in voltage) :-The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage Breakdown voltage :-It is the minimum reverse voltage at which the P-N Junction can conduct without damage to the current
What is meant by cut in voltage in diode?
Cut in voltage (Knee voltage): The forward voltage at which the current through the P-N Junction starts increasing rapidly is called as Cut in voltage or knee voltage.
How do you calculate knee point voltage?
Step 1: calculating knee point voltage Vkp Vkp = {2 x Ift (Rct+Rw)}/ k Vkp = required CT knee point voltage Ift = max transformer through fault in ampere Rct = CT secondary winding resistance in ohms Rw = loop impedance of pilot wire between CT and the K = CT transformation ratio Step 2: calculate Transformer through fault Ift Ift = (KVA x 1000)/(1.732 x V x Impedance) KVA = transformer rating in kVA V = transformer secondary voltage Impedance = transformer impedance Step 3: How to obtain Rct To measure when CT is produce Step 4: How to obtain Rw This is the resistance of the pilot wire used to connect the 5th class X CT at the transformer star point to the relay in the LV switchboard. Please obtain this data from the Electrical contractor or consultant. We provide a table to serve as a general guide on cable resistance. Example: Transformer Capacity : 2500kVA Transformer impedance : 6% Voltage system : 22kV / 415V 3phase 4 wire Current transformer ratio : 4000/5A Current transformer type : Class X PR10 Current transformer Vkp : 185V Current transformer Rct : 1.02½ (measured) Pilot wire resistance Rw : 25 meters using 6.0mm sq cable = 2 x 25 x 0.0032 = 0.16½ Ift = (kVA x 1000) / (1.732 x V x impedance) = (2500 x 1000) / (1.732 x 415 x 0.06) = 57,968 round up 58,000A Vkp = {2 x Ift (Rct+Rw) } / k = {2 x 58000 (1.02+0.16) } / 800 = 171.1½
What happens to the current when the voltage becomes limited at the knee?
A: Perfect example is a zener. As input voltage increases the current at the knee increases almost linearly at the zener voltage. If the inputs varies up or down then the current will vary up or down at the preset voltage making a zener a voltage regulator because of this feature
Cut in voltage?
The forward voltage at which the current through the junction starts increasing rapidly, is called the knee voltage or cut-in voltage.
What is class PS in current Transformer?
PS is a special class of protection transformer used in differential protection schemes. The CT is specified by what is known as the knee point (that is the point at which the CT saturates). Because they are specified using the knee point, two separate CTs will have the same characteristics. These matched CTs won't introduce measurement error during through faults on differential protection schemes.
What is a class X current transformer?
Class X CTs are special CTs used mainly in balanced protection systems (including restricted earth fault) where the system is sensitively dependent on CT accuracy. Further to the general CT specifications, the manufacturer needs to know: • Vkp - Voltage knee point • Io - Maximum magnetising current at Vkp • Rs - Maximum resistance of the secondary winding
How cable hi pot test be done?
with a voltage source and a current meter and log log paper. (hi-pot tester) plot the voltage vs the current when the line starts to bend or knee you are close to the failure voltage
What is zener break down voltage?
The point in the forward operating region of the characteristic curve where conduction starts to increase rapidly is called Knee voltage of a PN Junction Diode.The breakdown voltage of a diode is the minimum reverse voltage to make the diode conduct in reverse.(or) Breakdown voltage is a parameter of a diode that defines the largest reverse voltage that can be applied without causing an exponential increase in the current in the diode.-- Dinakar
