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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 else can I help you with?
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 0.37v and 0.63v in RC circuit?
0.63 is the knee voltage & 0.37 is the cutoff voltage
What is knee voltage for GAAs?
Knee voltage, also known as threshold voltage, in Gallium Arsenide (GaAs) refers to the minimum voltage required to initiate significant current flow in a GaAs device, such as a transistor or diode. This voltage is crucial for determining the operational characteristics of GaAs-based electronic components. Typically, knee voltage in GaAs devices is lower compared to silicon counterparts, making GaAs favorable for high-frequency and high-efficiency applications.
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
Difference between Threshold voltage and knee voltage?
the voltage at which electronic device operates is callled threshold voltageand the voltage at which device show cinduction in forward biased stste
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 point voltage of current transformer?
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.
What is knee voltage for silicon and germanium?
The knee voltage for silicon is approximately 0.7V, while for germanium it is around 0.3V. The knee voltage is the voltage at which a diode starts conducting significantly.
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.
Why the knee voltage for germanium is 0.2v?
The knee voltage for germanium is around 0.2V because this is the point at which the diode starts conducting current in a forward bias condition. Below this voltage, the diode remains non-conductive. This specific value is determined by the band gap energy of germanium.
What is needed to calculate the voltage across a device?
you calculate a voltage circuit by taking it apart and findng the circuit and calculate the voltage and then resible it.
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 0.37v and 0.63v in RC circuit?
0.63 is the knee voltage & 0.37 is the cutoff voltage
What is the value of the knee voltage and breakdown voltage of z?
It is about 0.7 volt for Silicon diodes.
What is the electric field voltage equation and how is it used to calculate the electric field strength at a given point in space?
The electric field voltage equation is E V/d, where E is the electric field strength, V is the voltage, and d is the distance between the charges. To calculate the electric field strength at a given point in space, you can use this equation by plugging in the values of voltage and distance to find the electric field strength.
How do you calculate the excitation voltage and current of an alternator?
formals to calculate exciation voltage of alternator
