Transformers that regulate current flow are critical components of the electrical power system’s monitoring and protection. Ct pt testing is instrument transformers that convert primary current to a lower secondary current with meters, relays, control equipment, and other instruments.
The significance of instrument transformer tests is frequently overlooked. Current transformers used for metering must be highly accurate to provide precise billing, whereas those used for protection must react quickly and correctly in the event of a fault. CTs should undergo six electrical ct pt testing to ensure accuracy and optimal service reliability.
Ratio & polarity
In the case of a fully loaded circuit, the CT ratio is defined as the ratio of the principal input signal to supplementary current output. When 300 amps flow through the primary, a ct pt testing with a ratio of 300:5 will produce five amps of secondary current.
Unlike a voltage or power transformer, the primary winding of a current transformer has only one or a few turns. A single flat turn, a coil of heavy-duty wire wrapped around the core, or a conductor or bus bar inserted through a central hole can all be used for the primary winding.
Burden Secondary Side
The secondary resistance test verifies the CT secondary winding resistance with a specified one and no winding discontinuity. This value can be used in other calculations as well.
Loop resistance ensures that the load is connected correctly and that no circuits are left open. For secondary resistance, connect the circuit.
The magnetic channel inside a CT works as a short circuit transmission line when it becomes saturated. Almost all of the energy from the primary winding is diverted from the secondary winding and used to create a magnetic field inside the ct pt testing.
Excitation tests apply an alternating current voltage to the CT’s secondary winding and gradually increase the voltage until the CT reaches saturation.
It is critical to measure the DC winding resistance of a CT to determine the CT’s actual condition, state, and accuracy. Depending on the specimen’s age, use, external conditions, and loading effect, the winding resistance of a CT changes over time.
When connected to a relay or metering circuit, each current transformer has a secondary burden. Ct pt testing is expected to provide the secondary output current based on their accuracy class.
Voltage Withstand Test
The goal of an HV test is to determine whether the equipment is in good enough condition to be put into service after the installation for which it was designed. It should provide some basis for predicting whether or not a healthy state will persist or if the deterioration occurs, resulting in an abnormally short life.
Polarity by pulses
The polarity test confirms the markings on the ct pt testing primary and secondary and ensures they match the drawing. More importantly, it demonstrates how to connect the secondary circuits for the protection and metering to function correctly.