Nr Electric Co., Ltd

Nr Engineering Co., Ltd

Nr Electric Engineering Co., Ltd.

Qixue Zhang

Jun Chen

Guang Wang

Huazhong Li

Wei Yan

Kai Wang

Jiasheng Chen

Zigang Guo

Yaoyao Ji

Shouping Zhong

Jie Zhang

Quanrong Shen

Xiangjian Shi

Weiqun Liu

Honglin Wang

Baoli Xu

Yao Wang

The present invention discloses a method for detecting open phase of a startup/standby transformer based on optical CT. A startup/standby transformer in a power plant is in a no-load condition for a long time as a standby power supply. Once a single-phase open phase fault occurs, there is no significant change in the voltage phasor and voltage sequence component of each side. If not found in time, the defect may pose a great threat to the safe operation of the power plant. In the present invention, the optical CT is used to detect a three-phase current of the high-voltage side of the startup/standby transformer. If the current satisfies an open phase criterion, it is determined that an open phase fault occurs, and then, an alarm signal is given after a delay and an operator is informed to handle the fault in time. Therefore, the operation reliability of the startup/standby transformer system in the power plant is enhanced.

Method for detecting open phase of startup/standby transformer based on optical CT

The present invention discloses a method for quickly eliminating ferromagnetic resonance of a voltage transformer. The method includes: first sampling a three-phase voltage and an open-delta voltage of a voltage transformer; calculating a flux linkage corresponding to a zero-sequence voltage by means of an integral algorithm; and when detecting that ferromagnetic resonance occurs in the mutual inductor, further checking whether the absolute value of the flux linkage corresponding to the zero-sequence voltage or the absolute value of the open-delta voltage respectively falls within a set range, and if yes, starting a secondary resonance elimination loop for resonance elimination. The present invention also discloses a corresponding device for quickly eliminating ferromagnetic resonance of a voltage transformer. The present method and device accurately analyze and control resonance elimination trigger time based on a conventional secondary resonance elimination principle, and can effectively eliminate the impact of the core saturation of a voltage transformer on a resonance elimination process, thereby greatly improving the success probability of single resonance elimination.

Method and device for quickly eliminating ferromagnetic resonance of voltage transformer

A method and apparatus for identifying an open phase of a circuit breaker on the basis of voltage. The method comprises: a protection apparatus measures three-phase voltages at two sides of a circuit breaker; respectively calculates a vector difference and an effective value of the voltages at two sides of the circuit breaker; when the phase voltages at two sides are both greater than 80% to 90% of a rated voltage, and the voltage vector difference at two sides of the one-phase or two-phase circuit breaker is greater than a set voltage, it is determined that the circuit breaker has an open phase; and actuates an alarming or tripping operation after a short time delay t.

Method and apparatus for identifying open phase of circuit breaker on basis of voltage

A relay protection method against LC parallel circuit detuning faults comprises the steps of: a relay protection device samples a current of a parallel LC, that is, a reactor and a capacitor, and samples a total current flowing through the whole LC; convert the current of the reactor into a current of an equivalent capacitor; calculate amplitudes of the current of the equivalent capacitor and a current of a realistic capacitor and calculate an amplitude of the total current flowing through the LC; calculate a current amplitude ratio of the equivalent capacitor to the realistic capacitor; and when the amplitude of the total current flowing through the LC is large enough, send an alarm signal or a trip after a setting time delay if the current ratio exceeds a preset upper and lower limit range. Also provided is a corresponding relay protection device.

Relay protection method and apparatus against LC parallel circuit detuning faults

Embodiments of the present invention disclose a current source converter differential protection method, including: sampling, by a relay protection device, secondary side currents of current transformers on two sides of a protected current source converter, to obtain incomer-side three-phase currents, and outgoer-side three-phase currents; rectifying the incomer-side three-phase currents and the outgoer-side three-phase currents, to obtain an incomer-side input current and an outgoer-side output current which are equivalent; converting the incomer-side input current and the outgoer-side output current according to a current ratio of the current transformers on the two sides, to acquire a transient differential current and a transient restraint current; acquiring a differential current and a restraint current according to the transient differential current and the transient restraint current; and achieving differential protection according to the differential current and the restraint current. The embodiments of the present invention further disclose a relay protection device correspondingly.

Current source converter differential protection method and relay protection device

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Jiangsu, China

Qixue Zhang