Several Improvement Measures to Improve the Reliability of Generator Excitation System

We have taken the following corresponding improvement measures for these problems. 2 Reconstruction of regulated power supply 2.1 Designing different power supply The original excitation regulator is powered by dual 400Hz. The input voltage of the regulated power supply is connected to the secondary side of the power transformer. The primary side is connected to the secondary exciter voltage. In fact, it is an AC power supply. If the output of the primary or secondary exciter of the power supply fails, the excitation regulator will lose its working voltage. This is Very dangerous, therefore, the author will connect a DC inverter power supply through the diode in parallel with the output of the 400Hz regulated power supply, thus improving the reliability of the power supply operation. See, in response to the HWTA type excitation regulator, see Table 1 Table 1 excitation. System action reason statistics serial number cause classification fault frequency number of percentage% statistical sample 1 regulated power supply 12402 over-excitation protection 413. 3 near total 3: number instantaneous limit 267 occurrence of various faults 4 other restrictions 6203 song 5 other reasons 620 from above The statistical results are not difficult to see: the generator excitation system fault of Mawan Power Plant mainly appears on the excitation regulator, while the AVR stability 2.2 selects the high reliability inverter power supply. The obstacles accounted for 4 restrictions and protection delays, 4% of the blig several groups of overhaul, the original operation is extremely unstable. The first two books4 Mawan Power Plant is a 4 300MW thermal power plant newly built in the early 1990s. The generators are QFSN-300-2 steam turbine generators produced by Harbin Electric Machinery Factory. The excitation system adopts three-machine excitation wiring mode. AVR is the HWTA type automatic excitation regulator for Harbin Electric Machinery Factory to introduce the technology of the Westinghouse Company. Excitation regulation is composed of 400Hz induction voltage regulator and isolation transformer. It is composed of diode full-wave rectification and other components. During the 7 years of operation and maintenance, the main power supply of Mawan Power Plant has been replaced by the main power supply with simple wiring and reliable performance. The military-grade inverter power supply produced by the factory still adopts the two-way power supply mode. The output of the 400Hz power transformer is connected to one channel, and the 220V DC of the other road is connected to the inverter for nearly two years. More reliable, no fluctuations in voltage. Such as the output of the unstable phenomenon 3 improved excitation regulator protection HWTA excitation regulator has a high initial response characteristics, with over-excitation protection, maximum excitation current limit and three-stage instantaneous current limit protection. The excitation current of the original design as the main exciter reaches the over-excitation J jump generator 1 10, -1. (type is replaced by -2 5 type, thus eliminating the original AVR protection and limiting the exit trip logic block diagram due to the adjustable resistance contact Bad, easy to change resistance value brings the source of the boat to gHiFig. Plus the new inverter power supply wiring of notebook6. 3 Replace the regulated power supply part of the excitation regulator The original regulated power supply uses the ZL-1A rectifier bridge, which has low rectification power. It is easy to heat up, the temperature rises, the performance is unstable, and the average service life is less than half a year. Sometimes it is necessary to replace it with 2 pieces and replace it with a rated current of 3A. The ZL-3A type rectifier bridge with relatively stable performance is used on average. Life expectancy is increased by 4 times.

Adding a 0.01MF capacitor between the 4th and 8th pins of the integrated block can filter out the harmonic components in the DC voltage and keep the output voltage of the regulated power supply stable. The test result shows: ±15V voltage output from the regulated power supply. After adding the capacitor, the ripple voltage is reduced from the original 40mV to 3.5mV. The voltage regulation effect is obvious to the power regulating board using the IC-317 type regulator tube. A metal with an area of ​​2~3 is installed on the surface. The heat sink can reduce the surface temperature of the integrated block by 10*C. Table 2 is the result of field measurement.

Table 2 uses infrared thermometer to measure the voltage of the integrated block surface temperature data ambient temperature C integrated block surface temperature / C installed heat sink before the installation of heat sink (4) will adjust the adjustable power supply in the power supply adjustment board from the original See the logic diagram of the tripping development limit motor or the de-excitation outlet tripping logic when the protection time limit setting value or the instantaneous three-stage setting value is seen. It can be seen that the importance of the triode Q2卩4 will cause the damage of an electronic component to cause large generators and systems. It is obviously unreasonable to unravel. It is understood that many operating units and our factory have also experienced such Q2Q4 triode breakdown, accidental jump generator accident 1H instantaneous current limit STIH trip relay evil, for this, the original circuit of HWTA has been improved Such as the tripping exit loop plus start blocking according to the manufacturer HWTA data, the general site AVR limit protection settings are as follows: 1.2pu instantaneous current limit CL = 22pu main excitation rotor current through 3 shunts to access AVR 3 DC / DC transmitter According to the protection limit setting values, it can be seen that: greater than 0.% "These two economic indicators, the author believes that on the basis of improving the level of commissioning and maintenance of the automatic excitation regulator, the problem of automatic input of the spare excitation device should be solved as much as possible. The idea is: 1AVR during normal operation, the manual excitation roughly tracks the output of the AVR; 2, the AVR fault is determined by the generator group and the AVR fault is first separated 41E switch, and the 41E control handle position is not corresponding to the standby excitation QF switch, 3 When the generator-changing group protects the action, it jumps to develop the motor, and at the same time jumps the 41 switch and the QF switch and locks the standby self-injection loop; 4 rounds of 4 spare excitation device automatically inputs the loop design. No disc '25 years of magnetic system forcible resection rate is not designed in the design of fc some defects | such as excitation regulator bookmark9 generator excitation system primary wiring diagram engineering design is considered when the generator is connected to the grid When the AVR is in normal operation, the 41E switch is closed, the 400Hz standby excitation regulation loop AC side isolation knife gate FK is closed, the DC output voltage is zero, the DC side QF switch is disconnected, and the standby excitation is in a hot standby state. When the operator finds the AVR When the fault is abrupt, the operator can manually adjust the output voltage of the QF switch and then disconnect the AER AC side 41E switch. Obviously, this manual manual switching mode is difficult to avoid the loss of the generator to ensure the continuous operation of the generator in the case of most AVR faults. The active operation of the operation is to achieve a tracking curve corresponding to the actual output of the generator with the actual rotor voltage of the generator with the automatic excitation regulator due to the excitation system failure, thus obtaining a tracking curve, as shown . As long as the operating personnel can adjust the reference curve properly, the low-excitation limiter cannot be limited when the common part of the excitation of the excitation technology introduced by the Westinghouse technology in the United States fails. At present, these problems have been rationally improved in the 4 units of Mawan Power Plant. The method is simple and appropriate. Table 3: The spare excitation device tracks the measured data of the generator excitation regulator, making the excitation system more reliable and losing. Magnetic protection plays its due role in protecting generators and even system stability.