Discussion on high-voltage current limiting fuse combined protection device for generator short-circuit protection Guo Sijun Hefei Kaili Electronics Co., Ltd., Anhui Hefei combined protection device, and discusses its principle. Structure and characteristics, expounding its application scope and its most pre-development development. With the continuous increase of power consumption, the installed capacity of power stations is increasing, which has higher requirements for the reliability and economy of power station operation. The short-circuit protection of the power plant's power system puts forward higher requirements. It requires the circuit breaker to cut off the normal load and reliably eliminate the short-circuit fault in the event of a short-circuit fault. At the same time, it can also undertake the dual tasks of control and protection. China's small and medium-sized generators directly use 3 with 10 0200 type oil-less circuit breakers, which have the shortcomings of long closing time, which are not suitable for frequent operation, large volume and large maintenance. Therefore, many manufacturers now use vacuum circuit breakers more, but Whether it is a low oil switch or a vacuum circuit breaker, there are many questions about the non-periodic component of the short circuit current. When the generator port fails, the short circuit current is provided by the generator, due to the generator 1 1 is the synchronous reactance of the generator, and the total resistance of the stator circuit of the generator is large. Therefore, the decay time constant of the short-circuit current is large when the fault occurs, causing the current in several cycles to be zero, so-called zero-loss. The break is based on the fact that the input fracture energy is zero when the current crosses zero, and the arcing time is as short as possible. The zero-loss phenomenon seriously deteriorates the working condition of the circuit breaker, which makes it difficult to break the arc and even if the circuit breaker can break the short-circuit current, it The protection provided has a certain lag relative to the moment when the fault occurs, especially for many types of AC circuit breakers, which can only extinguish the arc when the current crosses zero. , to achieve the final purpose screen of the breaking fault plus the time difference formed by the relay protection, the breaking time is too long, usually requires several cycles, so that the long time has not been able to protect the certain electrical equipment. The peak of the current of the bean road has been several times for the generator breaker and the transformer. The generator and the circuit breaker have great electric power and thermal effects. Therefore, the circuit breaker protection method is not very effective at the receiving date of 199930. In the case of several major accidents, it is possible to damage the generators that cost millions of baht, and the cattle may have a coal bomb of the circuit breaker. The short circuit of the core occurs at the input end of the transformer. The mountain breaker can not cut off the short-circuit current quickly. The arc energy generated by the short-circuit current for a long time will make the rated current of the transformer burst circuit breaker work normally, and the short-circuit fault occurs. The short-circuit current is very large, and there is a contradiction between the rated current and the short-circuit current. In particular, the capacity of the modern power system is increasing, the value of the short-circuit current is also rising, and the electric shock generated by the powerful short-circuit current is more destructive. The device is selected according to the breaking short-circuit turbulence, and the equipment circuit and the circuit breaker itself must be designed with sufficient thermal stability stability margin, so the investment of the equipment plus the artificial price is too high to use the new! The electrical equipment is set so that it can be short-circuited at the moment of short-circuit and the short-circuit current is not yet available. Cut the hat! When the value is large, the plate current is made to avoid the extreme thermal shock and electric power of the equipment and the switch itself. A new type of circuit protection device is recommended here, that is, the high-card current limiting fuse combination protection device is referred to as 2 basic structure and operation principle. The main part is the following three parts: 1. Current limiting fuse; high-energy zinc oxide resistance; The organic combination of load switch users replaces the circuit breaker, and the circuit breaker fast fuse that controls and protects the body is turned off, and the overload current and rated current are interrupted by the load switch, and the limit of high-energy zinc oxide resistance is utilized. Pressure and energy transfer enable rapid arc extinguishing to limit overvoltage 1 Current limiting fuses Current limiting fuses have two significant advantages over circuit breakers, namely, current limiting and fastness. A large half-wave short-circuit current will limit and forcefully cut off the short-circuit current 02 in the future, so that the current reaches + to the expected short-circuit current peak. When the short-circuit current rises, the fuse is blown and intercepted. The off current is only about 1 of the expected current peak. However, when the fuse is blown, arc voltage is generated, which may usually reach tens or even hundreds of atmospheres. In order to solve the operation overvoltage of the fuse, the voltage limiting energy dissipation is realized by the nonlinearity of the zinc oxide resistor, and the arc voltage generated by the fuse is generated. The current is intruded, the zinc oxide resistor is rapidly attenuated, and each phase fuse is equipped with a single striker. As long as the phase fuse acts, the striker strikes the load switch to trip, and the linkage auxiliary switch sends a signal to the control room, and displays the action signal on the screen. . The load switch action is non-electrical breaking, which prolongs its maintenance period and service life, and avoids the load-breaking switch of the electric-phase phase-deficient operator group and the fuse that only needs to be able to break the rated current and the general overload current. There is no requirement for the short-circuit current and the dynamic stability and thermal stability of the short-circuit current. The body of the load switch can be made much smaller than the oil-burning and vacuum circuit breakers, and the structure is very low. The high-energy zinc oxide electric muscles are connected in parallel and installed on the power supply side of the load switch. They can also be installed on the feed side of the load switch. When it is not necessary to change the fuse frequently, the former arrangement should be adopted, so that the load switch can be protected by the fuse. The short-circuit accident caused by the reverse, the latter arrangement should be adopted to facilitate the high-energy zinc oxide resistance non-linear resistance, the solid-state sensitive component with nonlinear volt-ampere characteristics and the suppression of transient over-voltage, when the terminal voltage is lower than a certain At the threshold, the current is almost zero; when it exceeds this threshold, its current will be large and sharp with the voltage of the terminal. By using the good non-linearity of the zinc oxide resistor, the operating overvoltage generated when the fuse is turned off can be limited to 25 times the phase voltage. At the same time, the energy of the zinc oxide resistor can be tens or even a single piece, which ensures that there is sufficient capacity to absorb the magnetic field energy in the system when the corresponding off current is attenuated to zero, so that the fuse has no arc in the body. The pressure on the breaker housing is relieved, so that the electrical equipment is no longer subjected to large current surges, and the current is quickly attenuated to zero in 0 to 2 time, so that the energy supplied by the power source is minimized. Its non-linear characteristic 2 is the DC 1 reference voltage, and the residual pressure when the current flows through the zinc oxide valve piece is accurately measured and selected by the zinc oxide valve piece, and the small connection contains the residue. . The å“ž å“ž å“ž å¼€å…³ å¼€å…³ å¸¦æœ‰ å¸¦æœ‰ å¸¦æœ‰ å¸¦æœ‰ å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“ž å“žOn the replacement side of the electrical equipment, the installation principle is only for the zinc oxide resistor, 15, for the load switch = 3 fuse zinc oxide resistance and the load switch parameter selection fuse, the principle of the mouth parameter selection is, in addition to the short circuit In any case, it shall not be operated. In the case of short-circuit fault, the short-circuit current shall be limited and cut off as soon as possible. 4 According to the combination curve of the exchange, è –, and fatigue, the rated current of the fuse is greater than 4 of the transformer core, ie 1.47. The second characteristic curve 1 of the device should be located on the side 2 of the transformer overload special line 2, so that the transformer can be guaranteed to be in the shackle, allowing 1 to pass the dip condition of the imitation device without mistakes. When the squash is combined, the magnetizing impulse current is 12 times of the full load current, and the allowable duration is 0.18. Therefore, it is necessary to ensure that the fuse passes through the 12-fold variable instrument full load current and continues to 018 curve 4 and continuously impacts 100 times without aging. According to the above-mentioned vertical selection, the blower occurred at the factory transformer for 26 o'clock; the jet is not affected by the boundary. When the flow = 3.8, the mixing of the jet and the environmental water body is seriously affected by the bottom boundary. 7 Conclusion Pulse floating The mixing of the jet continuous floating jet and the environmental water body is very large; the limb is different. When the initial stage of the jet is less than the jet duration, the pulsed floating jet has no difference from the continuous floating jet, but later, due to the pulse The degree of momentum reduction in the floating stream no longer increases. The front peak dimensionless position pair 2 of the pulse jet is independent of the pulse jet duration. This characteristic is the same as the continuous jet. The influence of the bottom boundary on the jet is mainly related to the buoyancy acceleration of the jet exit flow velocity duration and the influence of the jet orifice from the bottom boundary.
The research method and preliminary results of the research and development of the river bottom jet scouring and sedimentation research laid the foundation for the work. Yu Guoliang, 1964, male, Changsha, Hunan, researcher at the University of Hydropower, engaged in river sediment research and development; Zhuang 1957, female, Chengdu, an engineer at the State Key Laboratory of Rapid Fluid Mechanics, engaged in hydraulics and river dynamics research; Liao Neiping 15 years, male, Yibin, engineer of Southwest Electric Power Design Institute of National Electric Power Company, engaged in thermal power plant Design work such as hydraulic engineering.
The load switch is only used to break the rated current and the general overload current, which greatly reduces the burden of the load switch, prolongs the service life and the repair period. The clicker of the fuse can avoid the lack of phase operation hall, and its action and standby power supply linkage. The host é™åˆ¶ limits the operating overvoltage by non-stop high-energy zinc oxide resistors, which protects the insulation safety of the equipment.
The device has a simple structure, a small volume, and a low cost. High-voltage current limiting fuse 41. Xi'an Jiaotong University Press,1991.2 Wang Jimei. High-voltage AC load switch Beijing Machinery Industry Press, 1997. Author brief introduction Guo Sijun, 1965, male, Hefei, Anhui, deputy general manager and engineer of Hefei Kaili Electronics Co., Ltd., mainly engaged in the development of high-current short-circuit protection for power systems
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