47 results about "Impedance plane" patented technology

Method of limiting low excitation, calculating measured impedance of generator terminal by detecting generator terminal voltage and terminal current, when the measured impedance entering low excitation limited impedance circle, the low excitation limits prolong action of 40-60 ms on amplifying excitation current to maintain generator in stable operation situation, the low excitation limited impedance impedance circle covers static stable loss of excitation protection impedance circle to implement seamless connection with generator loss of excitation protection impedance criterion, and prevent the generator in low excitation operation, the low excitation is limited lagging behind the loss of excitation protection action, thereby generator error jump is caused. The invention is used in generator excitation regulation, comparing with former low extitation limiting method, the invention is more visualized, the loss of excitation protection and low excitation are all R-X impedance plane coordinate description and easy to cooperate with each other.

The invention relates to a method for pilot protection of a circuit based on the current capacity and the voltage capacity at two ends, which comprises the following steps that: 1) two ends of the circuit are provided with same relay protection devices, and each relay protection device measures the current capacity and the voltage capacity of the end and acquires the current capacity and the voltage capacity of the opposite end through a communication channel; 2) each relay protection device performs calculation according to the current capacities and the voltage capacities of the two ends at the same time, the branch impedance of each phase and/or the inter-phase branch impedance are calculated for an alternating current circuit, and the branch resistance is calculated for a direct current circuit; and 3) for the alternating current circuit, a +R axis region is set on an impedance plane as an action region, and the branch impedance falls into the region and is judged as an internal circuit fault, and for the direct current circuit, a fixed resistance value can be set, the branch impedance is smaller than the fixed resistance value and is judged as the internal circuit fault.

The invention provides a composite steel pipe defect detecting device and a composite steel pipe defect detecting method, and belongs to the technical field of non-destructive detection. The device comprises an eddy current probe, eddy current detection coils wrapped on the outer surface of the eddy current probe and a driving device connected with the eddy current probe. The method comprises the following steps of: (a) inserting the cylindrical eddy current probe into the inner wall of a composite steel pipe to be detected; (b) detecting the composite steel pipe to be detected by the eddy current detection coils wrapped on the outer surface of the eddy current probe to acquire eddy current signals, and executing a step (c) when the impedance amplitude of the detected eddy current signals on an impedance plane graph exceeds a set alarm amplitude range; executing a step (d) when the impedance amplitude of the detected eddy current signals on the impedance plane graph does not exceed the set alarm amplitude range; (c) recording the composite steel pipe to be detected as an unqualified composite steel pipe; and (d) recording the composite steel pipe to be detected with a qualified mark. By the device and the method, defects of the composite steel pipe to be detected are quickly detected with high sensitivity.

The invention relates to a quick distinguishing method for zero-sequence directional elements of an alternating-current and direct-current serial-parallel power grid. The quick distinguishing method includes computing sampling values of zero-sequence voltage and zero-sequence current according to sampling values of three-phase voltage and three-phase current at a protection mounting position; establishing a time-domain differential equation based on instantaneous sampling values of the zero-sequence voltage and the zero-sequence current; computing weights of zero-sequence resistance and zero-sequence inductance by the aid of the time-domain differential equation and a least square method; converting the weight of zero-sequence resistance and the zero-sequence inductance of a system to frequency domain, and computing power-frequency zero-sequence impedance; and judging whether forward or reverse grounding faults occur or not by means of judging whether an area of an impedance plane with the zero-sequence impedance is in a positive-direction action area or a negative-direction action area. The method is not affected by low-frequency weights, fractional harmonic waves or the fact that positive-sequence impedance is unequal to negative-sequence impedance after the alternating-current and direct-current serial-parallel power grid fails, reliability of computation results is guaranteed, action performances of the zero-sequence directional elements are far superior to those of various power-frequency directional elements based on full-period Fourier algorithm and semi-period Fourier algorithm, and the quick distinguishing method has an extremely important application value.

The invention discloses a device and a method for non-contact magnetic induction impedance plane projection imaging. An alternating current magnetic field is generated in an excitation coil by introducing alternating sinusoidal current, a measured object with certain conductivity is arranged in the alternating current magnetic field, the inside of the measured object generates same-frequency alternating eddy current due to electromagnetic induction, measuring coils which are arranged into a plane in a matrix way are used for respectively detecting magnetic filed signals caused by the alternating current eddy current, according to the relationship of the measuring signals and the impedance distribution of the measured object, the impedance distribution condition of the part of the measured object corresponding to each measuring coil is respectively calculated, and all calculating results form an impedance plane projection image according to the positions of the measuring coils.

The invention provides a method and a device for matching and setting low-excitation limitation and field loss protection of a salient-pole machine, which are used for guaranteeing reasonable matching of the low-excitation limitation and field loss protection of the salient-pole machine. The method comprises the following steps: converting a low-excitation limitation curve to an impedance plane from a power plane, comparing the low-excitation limitation curve converted to the power plane with a static voltage stability limitation curve of the salient-pole machine in an R-axis positive semi-axis area; when the low-excitation limitation curve of the R-axis positive semi-axis area does not include the static voltage stability limitation, re-setting the low-excitation limitation curve. According to the technical scheme adopted by the invention, the reasonable matching between the low-excitation limitation and field loss protection of the salient-pole machine is guaranteed, technical basis is provided for power dispatching production management in a facilitated manner, the control and protection functions of the motor are brought into full play, the network source coordination level is improved, the safe and efficient operation of the energy resources are realized, and the power is guaranteed to safely and economically feed out.

A touch screen is disclosed which responds to a user's touch for re-drawing, re-scaling, re-translating and re-positioning an impedance plane signal received from non-destructive testing equipment, such as an eddy current sensor. The impedance plane is manipulated by slidingne, two or more fingers simultaneously to an end position to effectuate a complete re-drawing operation of the image.

The invention relates to a method for positioning a disturbance source of a power system based on high-order harmonic equivalent impedance property. A monitor of the disturbance source is arranged at a demarcation point of a power supply system and a user side, and the monitor of the disturbance source can catch voltage and current waveform containing disturbance at an M point so as to judge the disturbance is from upper stream or lower stream, wherein the power supply system side is arranged at the upper stream, and the user side is arranged at the lower stream; once the occurrence of one disturbance is measured at the detection point, the equivalent impedance Ze is calculated, wherein (Vpre, Ipre) and (Vduring, Iduring) are five-order harmonic negative-sequence voltage and current measured at the measuring point M before and during the occurrence of the disturbance; if the Ze falls in a first quadrant of an impedance plane diagram, the disturbance source is determined to be positioned on the power supply system side; and if the Ze falls in a third quadrant of the impedance plane diagram, the disturbance source is determined to be positioned on the user side.

The invention discloses an external penetrating rotating magnetic field detecting method for sucker rods. The detecting method comprises the following steps: a uniform rotating magnetic field generated by an excitation coil induces an annular eddy on the surface of a sample, and the annular eddy can be disturbed by defects at any angle on the sample; a detection coil picks up all axial disturbancesignals caused by the defects; voltage signals generated by the detection coil are amplified by a voltage amplifier and are received by a lock-in amplifier for processing, and real and imaginary voltage signals of defect signals are output; the signals are collected by a computer, and a variation curve is displayed on a front panel in real time by a LabVIEW program; and an impedance plan is drawnin MATLAB based on the real and imaginary data, and specific circumferential positions of the defects are judged according to image angles. The generated rotating magnetic field is more uniform and sensitive to the defects in all directions, so that all the axial disturbance signals generated by the defects can be picked up without being affected by lifting, and the method is suitable for the sucker rods with different outer diameters, and precise positions of the defects can be determined by a subsequent data processing method.

The invention relates to a co-chord multi-arc phase comparison loss of synchronism protection method. According to the method, an impedance plane is divided into five areas according to change of power angle Delta: 00-Delta 1, Delta 1-Delta 2, Delta 2-Delta 3, Delta 3-Delta 4, and Delta 4-3600, arc boundaries and reactance line boundaries of the five areas are divided, the area, in which measured impedance value ZC corresponding to current power angle Delta is, is detected according to the arc boundaries, historical logic of the ZC passing through the areas and dwell time thereof in the areas are judged, and whether a unit is in a step out state is confirmed; and the judgment result is generator step out or motor step out, pole slipping is recorded for once, and protection actuating signal is sent out through setting number of times of pole slipping. The Delta 1 and Delta 2 boundaries of the arc are corresponding to static stability boundary Delta J and moving stability boundary Delta M of the power angle of the unit, thereby being used as a boundary for unit step out logical judgment, being capable of preprocessing or warning early before step out, and simplifying loss of synchronization protection criteria; only sin Delta X value and cos Delta X value are needed, two multiplication computation are added in run, and then logic judgment is realized. The setting calculation process is simplified, and protection operation efficiency is improved.

A rotary bolt hole eddy current inspection scanner using a differential eddy current probe, the circuitry of the scanner is embodied with a filtering circuit with three filters: FIR (Finite Impulse Response), a low pass filter, and a phase control filter (by means of a Hilbert transform). The result from a scan of a bolt hole is an output signal on an impedance plane exhibiting a “backwards 6” shape of stable size when the scanner changes its rotating rate significantly.

Disclosed is an apparatus and method for generating virtual inspection channels mid-way between the physical inspection channels of an eddy current array probe, thereby reducing the coverage loss and improving defect sizing and imaging. The method is based upon a calibration to determine the mid-channel coverage loss for parallel defects having their long axis parallel to the scanning direction. Based on the coverage loss measurement, a vector analysis system is constructed enabling generation of virtual channel signals which are available for processing in the same way as physical channels, with impedance plane representation including real and/or imaginary signal components. The system differentiates between parallel and perpendicular defects and employs different algorithms to generate virtual channel signals for parallel and perpendicular defect orientations.

The invention relates to an analysis method for analyzing the action behavior of a positive sequence polarization voltage distance relay based on an impedance plane. The analysis method comprises thestep that the action behavior of the positive sequence polarization voltage distance relay is analyzed through the constructed impedance plane. The step further comprises the steps that Sa when a power system fails, the power system is divided into positive, negative and zero sequence subsystems, and the equivalent impedance of each sequential subsystem is solved; and Sb, an action equation of thepositive sequence polarization voltage distance relay based on the impedance plane is established. The analysis method of the relay uses current and voltage data to calculate the positive, negative and zero sequence impedances of the system in real time, so that the behavior of distance protection can be analyzed point by point; the calculated zero, positive and negative sequence impedances of the system are accurate; and the change of one operating mode of the power system can be reflected in real time.

The invention discloses a design method for improving the limiting sensibility of eddy current detection by using a resonant frequency change. A quartz crystal oscillator in an eddy current detection instrument is replaced with a frequency generated by a resonance circuit; an eddy current detection coil is used as an inductor part of the resonance circuit; the eddy current detection instrument designed through the method can obtain a resonant eddy current detection impedance signal chart comprising amplitude, phase and frequency information; the eddy current detection instrument has the work characteristics of a first generation of resonant eddy current instruments, meanwhile, has the advantages of a second generation of impedance plane analysis eddy current instruments; the limiting sensibility of the eddy current detection is further improved through the combination of the two mechanisms.

The invention discloses a method for measuring and estimating differential mode interference noise impedance through insertion loss. According to the method, a known impedance amplitude element is inserted into a circuit to measure voltage before and after the element is inserted so as to obtain the insertion loss value of the element. A noise source impedance amplitude range is obtained by drawing an impedance plane graph. According to the method, the operation is simple and easy, the experimental condition is simple, and the result precision is relatively high. The impedance value estimated by the estimation method is compared with a measured value of a laboratory, and the compared result indicates that the estimation range precision is high. Moreover, the estimation method also can be suitable for a system with unknown impedance, the impedance value estimated by the method is beneficial to later-stage filter parameter design, and the results also can provide effective data for an electromagnetic interference protective problem.