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What is difference between CT and PT?
Mar 27,2024
CT (Current Transformer) and PT (Potential Transformer) are both types of instrument transformers used in electrical power systems, but they serve different purposes:
Construction: Current Transformers consist of a primary winding, which is connected in series with the circuit carrying the current to be measured, and a secondary winding, which is connected to the measuring instrument or relay. The primary winding typically consists of one or more turns of heavy conductor material, while the secondary winding has many more turns of finer wire.
Construction: Similar to CTs, PTs have primary and secondary windings. The primary winding is connected across the high voltage circuit, while the secondary winding is connected to the measuring instrument or relay. PTs are typically step-down transformers.
Output: The output of a PT is a lower voltage, commonly standardized to 120V or 240V for measurement and control purposes.
CTs step down current, while PTs step down voltage.
CTs are typically connected in series with the circuit carrying the current to be measured, while PTs are connected across the high voltage circuit.
The output of a CT is current, while the output of a PT is voltage.
In summary, CTs and PTs are both crucial components in power systems, serving to accurately measure current and voltage, respectively, and provide safe levels of these quantities to instruments and protective devices.
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CT (Current Transformer):
Function: Current Transformers are used to measure alternating current (AC) in high-voltage circuits. They transform high currents into a proportional lower current that can be safely measured by instruments and protective relays.Construction: Current Transformers consist of a primary winding, which is connected in series with the circuit carrying the current to be measured, and a secondary winding, which is connected to the measuring instrument or relay. The primary winding typically consists of one or more turns of heavy conductor material, while the secondary winding has many more turns of finer wire.
Output: The output of a Current Transformer is typically a low current proportional to the primary current, typically standardized to 5A or 1A.
PT (Potential Transformer):
Function: PTs are used to step down high voltages to a lower, standardized voltage suitable for measurement or control purposes. They are also known as voltage transformers.Construction: Similar to CTs, PTs have primary and secondary windings. The primary winding is connected across the high voltage circuit, while the secondary winding is connected to the measuring instrument or relay. PTs are typically step-down transformers.
Output: The output of a PT is a lower voltage, commonly standardized to 120V or 240V for measurement and control purposes.
Key Differences:
CTs measure current, while PTs measure voltage.CTs step down current, while PTs step down voltage.
CTs are typically connected in series with the circuit carrying the current to be measured, while PTs are connected across the high voltage circuit.
The output of a CT is current, while the output of a PT is voltage.
In summary, CTs and PTs are both crucial components in power systems, serving to accurately measure current and voltage, respectively, and provide safe levels of these quantities to instruments and protective devices.