Current Transformer And Potential Transformer Theory Pdf
File Name: current transformer and potential transformer theory .zip
Hence the secondary of current transformer is never left open. Accuracy class: Metering needs high accuracy at load current while Protection need not have that high accuracy.
- Basics of CT and PT
- Instrument Transformers - CT and PT
- Electrical Sensors: Potential Transformers (PTs) and Current Transformers (CTs)
Basics of CT and PT
A current transformer CT is a type of transformer that is used to reduce or multiply an alternating current AC. It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the large values of voltage or current to small, standardized values that are easy to handle for measuring instruments and protective relays. The instrument transformers isolate measurement or protection circuits from the high voltage of the primary system. A current transformer provides a secondary current that is accurately proportional to the current flowing in its primary. The current transformer presents a negligible load to the primary circuit.
Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of turns on its secondary winding, but very few turns on its primary winding. The primary winding is connected in series with the load so that it carries full load current. A low voltage range ammeter A is connected across the secondary winding terminals. Secondary of the CT is practically short circuited since the ammeter resistance is very low. It should be remembered that secondary of the CT should not be made open as it draws heavy current and damages the primary winding of the CT.
The electrical instruments are not directly connected to the meters or control apparatus of high voltage for safety purpose. The instrument transformers like voltage transformer and current transformer are used for connecting the electrical instruments to the measuring instruments. These transformers reduce the voltage and current from high value to the low value which can be measured by conventional instruments. The construction of the current and potential transformer is similar as both have the magnetic circuit in their primary and secondary winding. But they are different in the method of working.
Instrument Transformers - CT and PT
Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Basic Theory and Practical Considerations in a Current Transformer Abstract: In this paper, a brief discussion about the theory and the governing fundamentals of a current transformer CT is presented. A classical modeling of the CT identifying the essential parameters is introduced and the basic formulas relating the CT voltage, current, burden, and their relationships have been discussed. Practical procedures for measuring the various burdens connected to a typical distribution circuits are analyzed.
The normal range of the current transformer for measuring the current is 5A or 1A whereas the standard voltage at the secondary winding of the potential transformer is up to V. The transformation ratio of the current transformer is always remained high, whereas for the potential transformer its remains low.
Electrical Sensors: Potential Transformers (PTs) and Current Transformers (CTs)
Recieve free updates Via Email! Home Electrical machines Power system Ask a question Contact electricaleasy. Share: Facebook Twitter Linkedin. Instrument Transformers How will you measure AC currents and voltages of very high magnitude?
From these primary variables, we may determine impedance, reactance, resistance, as well as the reciprocals of those quantities admittance, susceptance, and conductance. Other sensors more common to general process measurements such as temperature, pressure, level, and flow are also used in electric power systems, but their coverage in other chapters of this book is sufficient to avoid repetition in this chapter. Two common types of electrical sensors used in the power industry are potential transformers PTs and current transformers CTs.
Current Transformers CT and Potential Transformers PT are used to measure the current and voltage in a circuit of the order of hundreds of amperes and volts respectively. A CT has large number of turns on its secondary winding, but very few turns on its primary winding. The primary winding is connected in series with the load so that it carries full load current.
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