PT is the English symbol of the voltage transformer, and the PT disconnection is the voltage transformer disconnection.
In the power and electrical production activities, PT disconnection is a relatively common fault, the main reason is the secondary side overload, insulation drop or short circuit, which will affect the accuracy and reliability of protection, metering, measurement and other operations.
PT disconnection can generally be divided into PT primary side disconnection and secondary side disconnection, whether it is a primary side disconnection or a secondary side disconnection, it will make the voltage of the PT secondary circuit abnormal.
When the primary side of the PT is disconnected, one is all disconnected, at this time the secondary side voltage is completely absent, and the opening triangle has no voltage; the other is asymmetrical disconnection, at this time, there is no phase voltage on the secondary side of the corresponding phase, the secondary voltage of the continuous line phase is unchanged, and there is a voltage in the opening triangle.
When the secondary side of the PT is disconnected, there is no voltage in the PT opening triangle, and the phase voltage of the broken wire is zero.
When a single-phase grounding system with a neutral point is not grounded, the voltage to ground of the ground phase becomes 0, and the voltage to ground of the other two phases is doubled, while the load current and line voltage in the three phases are still symmetrical.
Therefore, in the neutral point ungrounded system line protection device, the criterion of PT disconnection should be able to distinguish between single-phase ground fault and asymmetric disconnection.
Anhui Kaichuan Electric Power Protection Equipment Co., Ltd. developed BWKX intelligent arc detuning and overvoltage protection device, can assume the function of PT cabinet; BWKY power grid integrated overvoltage protection cabinet can replace the PT cabinet, with the suppression of overvoltage, low voltage, voltage loss, elimination of ferromagnetic resonance, PT disconnection, ground fault line selection alarm and other protection functions, when the system single-phase ground fault is eliminated, can effectively limit the inrush charging current through PT, protect PT and fuse from being burned.
Introduction of Anhui Kaichuan Electric Power Protection Equipment Co., Ltd