0
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
Add your answer:
Earn +20 pts
How do you determine vkp and rct for class x current transformer given example of 8005a 15va class x ct?
RCT is Secondary resistance of Current transformer it depends on Design.
What is accuracy class in current transformer?
don't worry
What is the current in 1KVA Transformer?
Tis question is incompleet.1000 va =1 kva.This is the power capacity of transformer. A transformer having 2 currents Primary current and secondary current . for that we required both voltage. Simply we can calculate by a formula Voltage x Current x 0.8(power factor)=1000.
Why leakage reactance is kept small?
Leakage reactance is useful for limiting the short circuit current in transformer and generators. therefore normally the reactance of transformer varies for 4.5% for distribution transformer to 12.5% for 400KV class.
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
Why current transformer rated as 0.5 5p 10p 20p?
These are the Class codes for CTs used for protection purposes.
What is cl PS current transformer?
CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy. e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current
What does CL of a current transformer signifies?
CL of a CT is its accuracy class.. it is an approximate measure of the CT's accuracy. e.g. The ratio (primary to secondary current) error of a Class 1 (CL:1.0) CT is 1% at rated current
What happens to the current if the potential difference is stepped-up in an ideal transformer?
In an ideal transformer, if the voltage is stepped up by a factor of x, then the current is stepped down by a factor of x. The end result is that the power, P=VI, is not changed. Again, this is in the ideal case.
How is current controlled in welding transformer?
in welding machine, the transformer used is basically a current transforrmer. so by changing the tap of secondary side of transformer, we can increase or decrease the current in the transformer.
What is principle of Current transformer?
why does have to short-circuit secondary wire of current transformer ?
If transformer current 250 amp at 60Hz what will be its current at 50Hz?
Current = voltage x resistance. Therefore the current will be the same, assuming both frequencies are the same input voltage.
