1. A method for detecting ignition of a carbon brush of a synchronous generator is characterized by comprising the following steps: whether the carbon brush is ignited is found by calculating corresponding excitation impedance of each point according to a uniform time interval T in a certain current time window and carrying out mutation detection, wherein the ignition detection method comprises the following steps: detecting whether the synchronous generator is generating, if the synchronous generator is generating, judging whether the excitation device works normally, if the excitation device works normally, acquiring a series of continuous excitation voltage and excitation current data with a sampling time interval of T in a current time window from the excitation device, and then, through a formula: calculating the excitation impedance of each point as excitation voltage/excitation current, and searching whether the excitation impedance has sudden change or not within 1T-3T time span in sequence; if the excitation impedance mutation exists, whether another group of excitation impedance mutation exists is searched within 1T-3T time span in sequence again, and if the excitation impedance mutation also exists, the synchronous generator is alarmed to have the ignition fault.

2. The method for detecting the carbon brush ignition of the synchronous generator according to claim 1, characterized by comprising the following steps: the impedance mutation detection time span of the ignition detection method is different from 1T to 3T.

3. The method for detecting the carbon brush ignition of the synchronous generator according to claim 1, characterized by comprising the following steps: according to the sparking detection method, two different impedance sudden changes are continuously detected within the current window time to confirm the sparking fault.

Background

The establishment of the rotor magnetic field of the synchronous generator generally needs an external excitation device to continuously provide a relatively large excitation current for the rotor, the excitation current can be transmitted to the rotor only through the dynamic contact of a fixedly installed carbon brush and a bearing rotating the synchronous generator, the dynamic contact may cause instant increase of the resistance of contact surfaces of the two sides (namely poor contact), the carbon brush and a collector ring on a rotating bearing are burnt, once the burning occurs, the contact resistance between the carbon brush and the collector ring is further increased, further burning of the carbon brush and the collector ring is caused, and finally the machine has to be stopped for maintenance, so that the maintenance cost is not increased, the maintenance time is also prolonged, and great loss is brought to power generation due to waste of hydraulic resources due to long-time machine halt. If the ignition fault can be detected at the initial stage of carbon brush ignition, the maintenance is simple, the cost is low, the maintenance time is short, and the power generation loss is basically avoided. Therefore, it is necessary to detect the carbon brush sparking of the synchronous generator in real time.

The ignition of the carbon brush of the synchronous generator is not directly reflected by a proper sensor temporarily, the conventional power plant basically adopts a manual regular inspection method, an inspector observes the joint of the carbon brush and the rotating collecting ring for several minutes at intervals, and if the flashover phenomenon is not found, the power plant is considered to be normal; the inspection mode has the problem of real-time performance, and the longer the time interval between two inspections is, the worse the real-time performance is, the timeliness of the carbon brush ignition fault treatment is seriously influenced, the fault coverage is enlarged, and meanwhile, the unmanned development trend of a power plant is not met. In addition, a special camera is additionally arranged near the carbon brush and is used for detection in a video identification mode, the carbon brush is provided with an end cover, only one camera which is installed near the carbon brush is difficult to observe comprehensively, meanwhile, the carbon brush consisting of the graphite base material generates a large amount of dust when being worn, and workers need to be arranged to clean the lens of the camera at intervals, so that the mode is not good in use and low in identification rate except for increasing a large amount of cost, and meanwhile, the vertical rod for installing the camera can seriously hinder the machine disassembling and overhauling work of a machine set.

Disclosure of Invention

The invention aims to provide a method for detecting carbon brush sparking of a synchronous generator, which aims to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: a method for detecting carbon brush sparking of a synchronous generator includes the steps of calculating corresponding excitation impedance of each point according to uniform time intervals T in a certain current time window and conducting mutation detection to find out whether the carbon brush is sparking or not, wherein the method for detecting sparking comprises the following steps: detecting whether the synchronous generator is generating, if the synchronous generator is generating, judging whether the excitation device works normally, if the excitation device works normally, acquiring a series of continuous excitation voltage and excitation current data with a sampling time interval of T in a current time window from the excitation device, and then, through a formula: calculating the excitation impedance of each point as excitation voltage/excitation current, and searching whether the excitation impedance has sudden change or not within 1T-3T time span in sequence; if the excitation impedance mutation exists, whether another group of excitation impedance mutation exists is searched within 1T-3T time span in sequence again, and if the excitation impedance mutation also exists, the synchronous generator is alarmed to have the ignition fault.

Preferably, the impedance jump detection time span of the ignition detection method is from 1T to 3T.

Preferably, the sparking detection method detects two different impedance sudden changes continuously within the current window time to confirm the sparking fault.

Compared with the prior art, the invention has the beneficial effects that: according to the method for detecting the carbon brush ignition of the synchronous generator, no additional detection equipment is needed, the existing real-time data modeling of the excitation device is fully utilized for online detection, and the cost investment is saved;

according to the method for detecting the carbon brush sparking of the synchronous generator, whether the carbon brush is subjected to sparking or not is detected by utilizing the sudden change of the impedance of the excitation loop of the synchronous generator, the direct reason of the direct sparking is adopted, the sparking is generally caused by poor contact of an electric loop, and the detection reliability is higher;

the method for detecting the carbon brush ignition of the synchronous generator has the advantages that the online automatic detection method is high in real-time performance, extra manual assistance is not needed, the ignition fault can be detected in the initial stage, the expansion of accidents is avoided, and meanwhile, the foundation is laid for the unmanned development trend of power plants.

Drawings

Fig. 1 is a schematic diagram of a working flow of a method for detecting carbon brush sparking of a synchronous generator according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, the present invention provides a technical solution: a method for detecting carbon brush sparking of a synchronous generator includes the following steps: detecting whether the synchronous generator is generating, if the synchronous generator is generating, judging whether the excitation device works normally, if the excitation device works normally, acquiring a series of continuous excitation voltage and excitation current data with a sampling time interval of T in a current time window from the excitation device, and then, through a formula: calculating the excitation impedance of each point as excitation voltage/excitation current, and searching whether the excitation impedance has sudden change or not within 1T-3T time span in sequence; if the excitation impedance mutation exists, whether another group of excitation impedance mutation exists is searched within 1T-3T time span in sequence again, and if the excitation impedance mutation also exists, the synchronous generator is alarmed to have the ignition fault.

The impedance mutation detection time span of the ignition detection method is different from 1T to 3T, so that the possibility of missed detection is avoided;

according to the ignition detection method, two different impedance sudden changes are continuously detected within the current window time to confirm the ignition fault, so that the possibility of false alarm is avoided;

in summary, according to the method for detecting carbon brush sparking of the synchronous generator, other detection equipment is not required to be additionally arranged, the fault identification is carried out by fully utilizing real-time data modeling provided by the excitation device, generally, due to frequent changes of the operation condition of the synchronous generator, the excitation voltage and the excitation current of the synchronous generator can correspondingly change frequently, and therefore whether the carbon brush is sparking or not can not be directly judged according to the frequent changes; however, the impedance of the rotor coil of the synchronous generator is determined in the stage of equipment production and manufacturing, and basically does not change with the change of the operating condition of the generator, as for the normal contact resistance between the carbon brush and the collecting ring is very small and can be ignored, when the synchronous generator is in normal operation, the carbon brush is ignited, the contact resistance between the carbon brush and the collecting ring is suddenly increased, so that the impedance of the rotor excitation loop seen from the measuring end of the excitation voltage and the excitation current is as follows: the inherent impedance of the rotor coil and the contact resistance between the carbon brush and the collector ring have large jump, so that the ignition fault of the carbon brush can be detected by utilizing the sudden change of the impedance of the excitation loop; the method utilizes the sudden change of the impedance of the excitation loop of the synchronous generator to detect whether the carbon brush has the direct cause of sparking or direct sparking.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.