46results about How to "Requirements for downsampling" patented technology

The invention relates to a single-ended-data-based multi-segment distance protection method and system of a high-voltage direct-current line. The method comprises: voltage and current information at relay protection device installation locations of p-pole and n-pole lines of a direct-current transmission system are collected and the collected information is sent to respective signal processing units of all segments of protection units of the two poles of lines to carry out low-pass filter processing with different cutoff frequencies; according to line parameters and measurement signals after filtering of all segments of protection units, compensation voltages of set points of all segments of protection units of the two poles of lines are calculated; and ratios of the compensation voltages of set points of all segments of protection units of the two poles of lines to corresponding filtered measurement voltages of the segments are calculated and internal and external faults in the high-voltage direct-current line zone are determined based on the negative or positive state of the ratios. The criterion is simple; the reliability is high; and the set basis does not rely on simulation; and thus a series of problems that the existing high-voltage direct-current line protection is lack of clear setting basis and the reliability is low are solved.

The invention discloses a backup protection method and device for a high-voltage direct current transmission line. The method comprises the following steps: collecting current information of a relay protection device installed on both sides of the high-voltage direct current transmission line; filtering the sampled current information by a low-pass filter to obtain a filtered current sampling value; and filtering the sampled current information by a low-pass filter. Using the filtered current value, the differential current of the positive and negative DC lines after filtering can be calculated. By comparing the difference current of the positive and negative DC lines after filtering with the minimum action current, the faults inside and outside the DC line can be determined. If the faultis located in the DC line protection area, the fault of the positive line, the negative line or the bipolar line can be determined by comparing the difference between the positive and negative filtered current values. The invention has the beneficial effects of simple criterion, fast operation speed and high reliability, and can respond to the high-resistance grounding fault of the DC line, and can solve the problem that the action speed of the backup protection of the DC line is too slow.

The invention discloses a bus protection method based on the sudden-change direction of fault current containing power frequency bands, and belongs to the technical field of power system relay protection. When a bus or a circuit breaks down, three-phase current data of all circuits of the bus in a short time window existing after the bus or the circuit breaks down are extracted, and a line model current containing fault phases is obtained after calculation through the three-phase current data; db4 wavelet transform is conducted on the line model current, the frequency bands where power frequency amount exists are used for conducting straight line fitting, and whether the bus breaks down or the circuit breaks down is judged according to whether the slope polarities of straight lines obtained through fitting of all the circuits are the same or not. According to the bus protection method based on the sudden-change direction of the fault current containing power frequency bands, protection is formed by means of the variation tendency of power frequency band components of the current, the protection is reliable, the requirement for the sampling rate is low, and the head polarity of traveling waves does not need to be detected; the needed time window is short, the complete power frequency amount does not need to be extracted, the situations where a current transformer is saturated, and a power frequency current flows out of the fault bus cannot influence the method.

The invention discloses a transverse differential protection method for a DC power transmission line based on a DC filter branch current, and the method comprises the steps: 1, measuring current instantaneous values, passing through an I-pole DC filter branch circuit and an II-pole DC filter branch circuit, of a rectification side of a DC power transmission system, and recording the current instantaneous values as i(t) and i<II>(t); 2, calculating a transverse differential protection current instantaneous value according to a formula: i<hc>(t) = i(t) + i<II>(t), taking 10 ms as a data window, calculating a transverse differential current, the root-mean-square value of the I-pole DC filter branch circuit and the root-mean-square value of the II-pole DC filter branch circuit, and respectively recording the transverse differential current, the root-mean-square value of the I-pole DC filter branch circuit and the root-mean-square value of the II-pole DC filter branch circuit as I<hc>, I, and I<II>; 3, carrying out the fault discrimination: start timing from zero when I<hc> is greater than I<set>, and recording a timing result as t; setting a mark flag = 1 if t is greater than t<set>, judging that a DC power transmission line region has a fault at this moment, and executing step 4, wherein I<set> is a current operation set value, and t<set> is a time delay set value; 4, carrying out the discrimination of a fault region: judging that the fault happens in a I-pole line region if I / I<II> is greater than one, or else, judging that the fault happens in an II-pole line region.

The invention discloses a DC single-ended fault positioning system and a DC single-ended fault positioning method based on active detection. The DC single-ended fault positioning method comprises thesteps of: determining a fault ride-through strategy of a converter, and enabling an MMC system to detect the change of a direct voltage or a direct current when a DC line fails; injecting an active detection signal, and discriminating faults through active fault control and disturbance application; filtering fault information, and processing the fault information by considering the coupling influence between positive and negative direct-current lines; and realizing fault positioning by using a least square method and a data sliding window method according to the voltage and current informationof a set point. The DC single-ended fault positioning system and the DC single-ended fault positioning method can precisely identify the fault region, are suitable for long DC lines, are not affectedby transition resistance, have low requirements for the sampling rate, and have relatively high reliability and precision in fault positioning.