CTs are located out door. Comparatively high peak voltage when secondary gets opened. Fine Turns Ratio adjustment is possible. C1 to C2 Lower Ratio e. Classes are 0. Specifications of Protection CTs Protection class CTs are not as accurate as metering class CTs but are designed to operate over a wide range of current. This wider range is necessary to allow the protection relay to operate at different fault levels.
Protection class CTs are typically rated to operate accurately up to 10 or 20 times the CT rating. Bar Primary CTs with one turn are popular Primary no of turns are low. Large no of Secondary winding turns. Primary current depends on the load connected. Secondary current depends on primary current Primary has two terminals one Incoming and other out going. CT secondary should never get open circuited when Primary current is flowing. Otherwise excessively high voltages will appear across secondary open circuited terminals and may damage CT secondary insulation Fuse should never be provided in CT Secondary Circuit.
Potential Transformers PT primary is connected across the line i. Primary current depends on secondary current. Both currents are comparatively low. Secondary voltage depends upon Primary voltage. Primary one terminal is connected to line or Bus and second terminal is connected to earth. PT secondary should not be short circuited.
Other wise PT may get damaged due to excessive heating. Open navigation menu. Close suggestions Search Search. User Settings. Skip carousel. Carousel Previous. Carousel Next. What is Scribd? Explore Ebooks. Bestsellers Editors' Picks All Ebooks.
Explore Audiobooks. Bestsellers Editors' Picks All audiobooks. Explore Magazines. Editors' Picks All magazines. Explore Podcasts All podcasts. Difficulty Beginner Intermediate Advanced. Explore Documents. Current Transformer. Uploaded by Mohammed Ayaz. Document Information click to expand document information Description: current transformer. Original Title current transformer.
Did you find this document useful? Is this content inappropriate? Report this Document. Description: current transformer. Current transformers, also known as CTs, are used to measure alternating current.
This means that they scale larger values of voltage down to small, more standardized ones that can be easily measured. Just like any other type of electrical equipment, each CT has a specific rating. This rating is used to determine what type of CT should be used in a given installation. During current transformer testing , transformer test instruments are used to determine whether your CT is functioning properly and that the power stays within the right parameters. Because CTs play an essential role in accurate consumer billing, transformer testing equipment is necessary to ensure accuracy in revenue calculation for utilities.
Potential transformers, or PTs, also measure an aspect of power supply. Such a permissible load is called burden of an instrument transformer. Let, N p is a number of turn in the primary winding. N s is the number of turns in the secondary winding. I p and I s are primary and secondary turns respectively. Start Learning.
Answer Detailed Solution Below Option 3 : potential transformer. The symbols of different equipment used in single line diagram are shown below. Hence, the given symbol is for the potential transformer. Leakage flux magnetising component of no-load current power factor of the primary energy component of excitation current.
Answer Detailed Solution Below Option 2 : magnetising component of no-load current. Ratio error in current transformer: In the current transformer, the primary current I p should be exactly equal to the secondary current multiplied by turns ratio, i. But there is a difference between primary current I p should be exactly equal to the secondary current multiplied by the turns ratio. This difference is contributed by the core excitation or magnetizing component of no-load current.
The error in the current transformer introduced due to this difference is called current error or ratio error. Phase angle error: In an ideal voltage transformer, there should not be any phase difference between the primary voltage and the secondary voltage reversed. The angle is -ve when the secondary voltage reversed lags the primary voltage. Get Started for Free Download App.
Answer Detailed Solution Below Option 1 : less than the number of secondary turns. Concept: Transformers used in conjunction with measuring instruments for measurement purposes are called instrument transformers. Instrument transformers are two types: potential transformer and current transformer. Application: A potential transformer needs to step down the high voltages i.
A current transformer needs to step down the high currents i. So, the number of primary turns is always less than the number of secondary turns. Transformer will burn immediately High induced EMF is produced in the secondary winding Flux density in the core gets weakened High current is produced in the secondary winding. Current transformer works on the principle of shorted secondary. It means that burden on the system Z b is equal to 0. Thus, current transformer produces a current in its secondary which is proportional to the current in its primary.
Important Points: Most important precaution in use of a CT is that in no case should it be open circuited even accidently. As the primary current is independent of the secondary current, all of it acts as a magnetizing current when the secondary is opened. This results in deep saturation of the core which cannot be returned to the normal state and so the CT is no longer usable. Again, due to large flux in the core the flux linkage of secondary winding will be large which in turn will produce a large voltage across the secondary terminals of the CT.
This large voltage across the secondary terminals will be very dangerous and will lead to the insulation failure and there is a good chance that the person who is opening the CT secondary while primary is energized will get fatal shock. Used to extend the range of the AC measuring instruments only Used to isolate the measuring instruments from the high voltage only Used to extend the range and isolate the measuring instruments Not used at generating stations and transformer stations.
Answer Detailed Solution Below Option 3 : Used to extend the range and isolate the measuring instruments. These are generally classified as i Current transformer - large alternating currents can be measured ii Potential transformer - High voltages can be measured Download Solution PDF Share on Whatsapp.
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