What is difference between 1A and 5A CT?
– 1A is my favorite, because the cable losses verliezen (VA) are 25x less compared with 5A. – 1A current transformer could be smaller at a required knee-point voltage. – 5A was required when relays took their power supply from the sensing current. – 5A is still commonly used in the US, unfortunately.
What is class1 CT?
Burden of CT. Difference between 0.2 and 0.2S class Metering CT. 5P20 Class Protection CT. Accuracy Limit Factor(ALF) of CT. Instrument Safety Factor(ISF) ofCT.
How do you choose secondary current in CT?
If secondary current is 5 A than burden will 25 times higher than burden of 1 A CT, So it is advisable to select 1 A secondary current if distance between Ct and Instrument is more.
Which is better 5P10 or 5P20?
Its application which differetiate the use of 5P10 and 5P20. If the breaker is used for backup protection say incommer etc you can use 5P20, but if it is say an incommer ACB/ MCCBof PMCC, you should use 5P10 only.
How do I choose a class in CT?
For a metering CT, choose a burden VA equal to, or greater than, 125 % of the total combined VA of instruments connected to the secondary side. For a protective CT, please contact the manufacturer for assistance. Accuracy • For a revenue CT, the accuracy should be at least IEC 0.2 or 0.5 CL or IEEE 0.3 or 0.6 CL.
What are different classes of CT?
Metering CT Accuracy classes are: 0.1, 0.2, 0.5 and 1. In wattmeters, energy meters, and power factor meters, phase shift produces errors. However, the introduction of electronic power and energy meters has allowed current phase error to be calibrated out.
What is the CT ratio?
Ratio. The CT ratio is the ratio of primary current input to secondary current output at full load. For example, a CT with a ratio of 300:5 is rated for 300 primary amps at full load and will produce 5 amps of secondary current when 300 amps flow through the primary.
What is CT and PT ratio?
CT is used to measure current while PT is used to measure voltage. CT is connected in series while PT is connected in parallel. CT ratio range is from 1 to 5A while the PT range is from 110V.
Why CT secondary is never kept open?
If the primary circuit has current flowing the secondary circuit should never be opened. This can cause very high voltages to occur due to the Ampere-Turns of the primary that start magnetizing the core. This results in the core being saturated through a large portion of the cycle.
What class of CT is preferable for differential protection?
The PS class CTs are used for differential protection. The differential protection is also called the zone or unit protection.