Analysis and treatment of a domestic generator rotor interturn short circuit fault
1 Overview Inter-turn short circuit of generator rotor is one of the rotor failures. Minor failures may only lead to local overheating and increased vibration. Serious failures can develop into rotor grounding and large shaft magnetization, which seriously threatens the safe operation of the generator. The QFSN 1 000-2-27 type generator manufactured by Dongfang Electric is currently widely used in the construction of thermal power generating units in China. Therefore, the QFSN 1 000-2-27 type generator A summary analysis of rotor interturn short-circuit faults will be of great significance to the safe operation of the same type of generator.
2 generator overview
QFSN 1 000—2—27 type steam turbine generator is a hidden-pole, two-machine, three-phase synchronous generator directly dragged by the steam turbine. The generator adopts water-hydrogen-hydrogen cooling method, equipped with a set of hydrogen oil-water control system, adopts static thyristor, base-end variable self-excitation excitation, and is supported by end-cap bearings. The rotor winding is made of silver-containing copper wire with good electrical conductivity, mechanical energy and creep resistance. There are 32 slots in the rotor winding of the generator, which are divided into 16 groups of I and II poles. The number of turns per slot of the rotor is 4xl + 7x7. The size of each turn of the copper bar is 46. 4x7. 9mm, rotor interturn insulation thickness is 0. 33mm. Composite insulation materials are used to isolate the turns.
3 Failure process After a company's 1000 MW turbine generator was put into operation for one month, the rotor had a dynamic turn short circuit phenomenon, and the on-line turn-to-turn short-circuit on-line monitoring device issued a short-circuit alarm signal. At the same time, it was found that the Y-axis vibration of the No. 9 bearing of the generator exceeded the standard seriously (up to 1 82 m), and the vibration value had a positive correlation with the excitation current of the generator. The larger the excitation current, the larger the vibration value. When the unit maintains phase-in operation, the unit vibration is significantly reduced. During its start-up process, the Chinese Academy of Electrical Sciences carried out a diagnostic test of interturn short-circuits in the rotor windings. The main items are the AC impedance test and the RSO test of the rotor at different speeds. Through experiments, it was found that the AC impedance at the time of 3 000 r / min was about 7% different from the handover data. The AC impedance changed abnormally between 0 and 3 000 r / min, and at 3000 r / min RSO test data also indicate the possibility of inter-circuit short-circuit. An on-line monitoring device for the rotor inter-turn short circuit was observed under the conditions of active power of 900 MW and reactive power of 50 Mv ar. The device showed that there were short circuits in 4 slots and 5 slots. In the process, the unit vibration reached 200 um. To further confirm whether the generator is actually stored
After the generator is installed, the generator rotor is subjected to AC impedance test and short-circuit air-gap waveform test (Gang 4). The test data are all satisfactory. It is determined that the rotor turns li IJ moment waypoint has been f 『L i Except when the normal running of the standby generator is full with a load of 1 006 MW F 1 '", it is measured that the vibration of the bearing pads of the generator returns to normal. 06
Within nl Hl, the generator excitation current is 3
A (rated value: 5 04l A). This confirms that the rotor has been repaired.
Figure 4 Air gap waveform after rotor repair
6 Fault prevention and diagnosis of generator rotor turns n 1 J Moment fault is a very common fault defect, which harms the giants. Therefore, various measures need to be taken to minimize the loss of swords. First, it is necessary to strengthen JJ l I For manufacturing operations, the personnel must strictly control the last fire during the refining of the scales, and urge the cattle manufacturers to complete the various f I plant tests in strict accordance with the l standards, and carefully review the test data. For data that exceeds the standard, be sure to look for "} 1 The original defect must not be easily placed to ensure that it can be transferred to Chuanzo. L When the excellent live-in factory test, the exchange outside the rotor bore "5 l [Anti}! J! IJ test, shared point pressure test and AC resistance test can only Detecting the static state of the apricot rotor is a short-circuit fault in the bird's turns, and a considerable part of the rotor winding only operates at high speed and the effect of electromagnetic force F / j will cause winding displacement, resulting in "HJ short-circuit fault" due to damage to the insulation. During the manufacturing process, the manufacturer must require the manufacturer to conduct the AC impedance test in the chamber during operation. If the conditions permit, the RSO waveform test is performed on the rotor after the trial rotation is completed. The rotor rotates 90 times. Perform a test and comprehensively compare and analyze the test waveforms. [J] to more accurately diagnose whether the rotor is in the turn. Secondly. Before the generator is put into operation, it is necessary to carefully organize the handover test on the generator rotor. Each test standard simultaneously meets the Jiajia and Jiangxi Electric · 2017 Avoiding Panjiao J Family t 1 ', J ~ H customs standards. ． After being put into operation, the generator needs to be carried out. "F," "Continent (push installation and installation), and the machine is transferred to I t Q short-circuit monitoring system.) The rim is arranged to carry out RSO waveform test and other card H-off tests so 『: Rotor turns short-circuit fault defect was discovered in time. When it was found and confirmed to turn around, after I 1] J short-circuit fault, it is necessary to strengthen the visual inspection of generator foot magnetic current, r power assist rate, special power, and bearing vibration. · H. ff J abnormal tripping conditions such as vibration trips of off-generator units, severely reduced power (excitation of excitation current over rated requirements), high rotor temperature, etc., should be stopped immediately after repairing.