摘要:
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. The relay protection method and device against LC parallel circuit detuning faults can improve stability of calculation results of a current ratio and raise sensitivity and rapidity of protection.
摘要:
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 (Ua, Ub, Uc, UA, UB, UC) at two sides (M, N) of a circuit breaker (B); 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. The method and the corresponding apparatus can solve the problem of the failure in recognizing an open phase by a traditional negative-sequence current criterion when a circuit breaker has an open phase in the case of light load; and moreover, three-phase inconsistent contact is not needed, and the method and apparatus are also suitable for a three-phase linked circuit breaker.
摘要:
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.
摘要:
In a frequency-conversion differential protection method for an output transformer of a static frequency converter (SFC) system, a protection device measures the three-phase current on each side of the output transformer of the SFC system; according to the connection manner of the output transformer, triangle side is used as a reference to perform phase correction on the star side; at the same time, in consideration of the secondary rated current on each side of the transformer are different, a balance coefficient on each side is adjusted, to calculate sampling values of correcting current on each side and the differential current; a generatorstart-up and shutdown protection algorithm which unaffected by frequency is used to calculate amplitude values of the correcting current, the differential current, and the restraint current; and frequency-conversion differential protection for the output transformer is implemented by using biased differential characteristic and according to magnitudes of the differential current and the restraint current. The protection method adapts to a large-scale frequency change, and compared with instantaneous overcurrent protection, greatly improves the sensitivity of detection on an internal fault of the output transformer.
摘要:
The present application provides a protection method, apparatus and system for a pseudo-bipolar direct-current power distribution network, and a device and a medium. The method comprises: detecting a transverse differential current value of a first direct-current switch of the pseudo-bipolar direct-current power distribution network, the transverse differential current value being an absolute value of a difference between a positive pole current amplitude and a negative pole current amplitude of the first direct-current switch; generating first transverse differential out-of-limit signals in response to a condition of the transverse differential current value being greater than a preset transverse differential out-of-limit threshold; detecting second transverse differential out-of-limit signals of a subordinate direct-current switch of the first direct-current switch; and determining that the fault of the first direct-current switch is an internal fault in response to a condition that the first transverse differential out-of-limit signals have been generated and the second transverse differential out-of-limit signals of the subordinate direct-current switch of the first direct-current switch are not found, and performing fault protection.
摘要:
Embodiments of the present invention disclose a differential protection method for current source converter, 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.