Zhuhai Wanlida MMPR series microcomputer-type (asynchronous) motor protection is suitable for large and medium-sized asynchronous motors in various systems, as backup protection for phase-to-phase short-circuit protection, comprehensive protection and measurement and control. This paper introduces the principle and setting of the positive sequence protection action of Zhuhai Wanlida MMPR-20H-T1 microcomputer, and analyzes the accident of the three-step test vehicle by air compressor, that is, when the air compressor is running normally, the MMPR-20H-T1 microcomputer is three times. The analysis of the positive sequence protection action finds that there is some problem with the positive sequence protection delay setting value in the protection device, resulting in the positive sequence protection action of the microcomputer and the air compressor jumping. The author takes this opportunity to discuss with colleagues. 2 Microcomputer positive sequence protection principle and setting MMPR series microcomputer type motor protection device phase current quick-break (short circuit) protection, when any phase current is greater than the quick-break setting value and reaches the setting delay, the quick-break protection action. The device can be set separately for the quick-breaking value outside the starting time and starting time of the motor, which can effectively avoid the starting current of the motor without affecting the sensitivity of the protection. Air compressor motor known parameters: motor rated voltage 10kV, rated power 10500kW, power factor 0.89, rated current 696A, starting time 45s, starting current 2227A, CT ratio 1000/5. According to the principle of Zhuhai Wanlida motor microcomputer protection, calculate Is. (Is, the set current of the microcomputer, the actual running current of the motor reacts to the value of the CT secondary side) I s =I e /n 1 = before the setting calculation. 696/200=3.48A current quick-break protection (positive-sequence quick-break), set by avoiding the motor starting current. I dz.j =K k×I stat /n 1 K k: Reliable coefficient Since the quick-break setting of Wanlida microcomputer protection can be set separately after starting time and starting time, it is necessary to calculate two speed setting values: 1 During the starting time, K k is 1.8, then I dz.j =K k×I stat /n 1 =20.043≈20A2 outside the starting time, since the motor running down to the rated current after the starting time, for the non-self-starting motor, to prevent After the starting time, the motor still runs at the starting level, K k is 0.8, I dz.j = K k × Calculated according to the company's relay protection setting and the Wanlida recommendation formula. 3 air compressor three jumps and causes analysis Two sets of 21000 air separation in the oxygen plant, one set of air separation into operation, two sets of air separation began to air compressor debugging and pipeline cleaning. The air compressor for jumping is two sets of air separation equipment. The first time the car was jumped, the air compressor was turned on at 10:30 on April 6 and jumped at 13:15 on April 7. The computer action report showed: 13:15, positive sequence protection action, 7.05A. The second jump, the air compressor started at 10:30 on April 8 and jumped at 13:19 in the afternoon. The computer action report showed: 13:19, positive sequence protection action, 7.86A. The third jump, the car jumped at 13:11 on April 9th, the computer action report showed: 13:11, positive sequence protection action, 7.42A. For these three jumps, the analysis is as follows: 1 The quality of the microcomputer product may not work well; 2 The excessive load of the CT loop may affect the accuracy of the microcomputer or the grounding of the CT loop, which may cause the air compressor to jump; 3 may be high Harmonic; 4 positive sequence current delay from 0 to 0.5s; 5 modify the clock of the microcomputer; 6 check the CT loop. Next, solve the problem. The problem is most likely at 2 and 4. The first item, check the CT loop. There are three versions of the CT loop from the original design to the actual use. The following are the following: (1) The original design of the CT loop: TA1 and TA3 are the two sets of current transformers at the first end of the motor, and TA2 and TA4 are the two sets of current transformers at the end of the motor. Protection device JBZ1 is Zhuhai Wanlida MMPR-20H-T1 microcomputer, PJ is electroplating meter, PA1 is high voltage cabinet ammeter, PA3 is field machine side cabinet ammeter, PTA is DCS current transmitter. The original design schematic of the CT loop. (2) CT loop field principle: TA1 is the motor first-end current transformer, TA4 is the motor tail current transformer, CT is the Siemens motor manufacturer, a total of six, but each CT has only two terminals, that is, one protection Coil. In addition, there is no filter on site. Therefore, the schematic diagram of the CT circuit is changed. (3) After the CT circuit is modified, the principle is as follows: after the above changes, the microcomputer and the background machine have no measurement data. Therefore, after the change, add the measurement loop, and the CT loop changes the schematic diagram again. The second item, the insulation of the CT circuit is qualified. The third item, modify the fixed value. At this point, it is found that the running air compressor has a positive sequence protection delay of 0.5 s, and the delay of the jump is 0. Finally check: 0 is the value of the design institute, and 0.5s is the value of the company's relay personnel. The original fixed value and the new fixed value of the relay protection setting value are unclear. The problem is here. The fourth item, the author believes that the first time and the second time are similar to the time of the jump. I suspect that the microcomputer has some shortcomings, so it is recommended to reset the clock of the microcomputer. At 8 o'clock the next morning, the microcomputer clock was 13 o'clock. In addition, in case of jumping, in order to check the problem. 18:37 boot. At 8 o'clock the next morning, there was no jump, and the Wanlida personnel set the clock back. Up to now, the air compressor has not jumped again. 4 Conclusion Through the three air compressor jump accidents, it can be found that the new fixed value and the original fixed value are unclear, which leads to the air compressor jumping, affecting the company's construction period and wasting a lot of manpower and material resources. Afterwards, the author and the relevant experts discussed again, there are still some problems. Although, so far, no more jumping, but there is still the possibility of parking. Because the CT does not match the microcomputer. There is no filter between the CT and the microcomputer, and some people say that the filter is built in. Furthermore, the CT is led out by two terminals, so that the CT at the head end of the motor is used for measurement and is used for protection, and may not be satisfied at the same time, resulting in the air compressor jumping. As for whether or not the air compressor can no longer be jumped, it needs to be further verified afterwards.
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