Electric Equipment Protection of Lianzhou Power Plant Desulphurization System
Electrical Equipment Protection of Lianzhou Power Plant Desulphurization System Luo Yong (Guangdong Electric Power Test Institute, Guangzhou 510600, Guangdong, China) briefly introduced the protection system of the electrical equipment for the desulphurization system in Lianzhou Power Plant, and discussed the key issues and solutions for setting calculations. .
The Lianzhou Power Plant desulfurization system, which is the first desulfurization system in Guangdong Province, was manufactured using the limestone-gypsum wet desulfurization technology of Austria AE. The company is fully responsible for the design, selection, and overall supervision of equipment production, installation and commissioning. . The Guangdong Electric Power Test Institute is responsible for calculating and setting the protection of electrical equipment.
From the AE company's design ideas for electrical systems, it can be seen that the reliability of power supply and electrical equipment is particularly important for the entire desulfurization system. This article will explain the requirements and calculations for the protection of electrical equipment in desulfurization systems based on the design ideas of electrical systems.
1 system wiring and interlock protection function Lianzhou Power Plant desulfurization system see. The 6kV desulfurization section is connected to the IA section of Unit 1 and the Section A bus of Unit 2 through circuit breakers 671B and 672B, respectively, and is connected with 2 circulating pumps and 1 oxidation fan, and passes through No. 1 or No. 2 desulfurization transformer to 380V. Desulfurization section and security section power supply. There is a backup diesel generator set in the security section. Normally, the 6kVlA and A sections are respectively sent to the breakers 671B and 672B, and the 6kV desulfurization section is only powered by one of the loops (eg, 671B loop). When the 6kVlA section suddenly switches to the standby section, its low-voltage protection has a delay of 1s to avoid the switching time of 0.5s. When the circuit fails or fails to switch, after 28s (test data), the desulfurization automatic control system (DCS) will automatically switch to another loop (such as 672B loop) operation. When the whole plant is out of power and the high-voltage startup standby transformer loses power, the desulfurization system security section and the diesel generator emergency start to ensure the safe operation of the desulfurization equipment.
2 Principles of setting calculations The principle of setting calculations focuses on the overall protection effect and does not focus on the protective effect of a certain set of relay protection. Sometimes it is desirable to reduce the protective effect of a protective device to improve the overall protective effect. A tuning scheme will have different protection effects due to different methods of setting and matching. Therefore, how to obtain an optimal setting scheme will be a research topic for engineering technicians engaged in relay protection setting calculations. This is a problem of setting techniques. After continuous practice, if we can more skillfully use various setting principles and are familiar with the operating characteristics of the protected power system, we can do - oxidation fan § cycle 闱 1 cycle through the bad pump Lianzhou plant desulfurization system 3 setting calculations considered Factors and cooperation of protection The protection of the system adopts MLPR-11C line protection equipment, MTPR-11C transformer protection device and MMPR-11C motor protection device produced by Zhuhai Wanlida Electric Equipment Company. The protection setting calculations are based on the principles in the design manual and are applied flexibly according to the actual wiring and protection configuration. It can be seen that it is necessary to carefully study the setting principles of quick-break and over-current protection for circuit breakers 671B and 672B. The factors to be considered are not mentioned in various materials and manuals. This is a typical design applied by AE in Austria and other countries.
After many discussions with the AE company's electrical experts, because the two branches of the circuit breakers 671B and 672B are powered by a single side power supply, the two circuit breakers cannot be set as line protection and should be used as protection for 6 kV bus and transformers, 6 kV motors Backup protection.
3.1 Quick-break protection The quick-break protection considerations include: a) The maximum value of the three-phase short-circuit current on the low-voltage side of the transformer should be avoided; b) Taking into account the abnormal power cut of the 6kV work section, switching to the standby section or switching to another 6kV working section , The emergence of a short power suspension process, should avoid 2 transformer excitation inrush current Idi and 3 6kV motor starting current / d2, the final setting current Id to take the maximum of the above two.
11.16A, Sensitivity coefficient Kim is tested at the short circuit of the two-phase bus under the minimum operating mode, Km=2.82, meeting the requirements of the design specification manual (Km>2).
3.2 Over current protection The main factor considered in over-current protection is to avoid setting the rated current of 2 sets of transformers and 3 sets of 6 kV motors. Calculation result: Id=4.57A, the sensitivity coefficient is tested at the low voltage side two-phase short-circuit of the transformer in the minimum operation mode, Km=1.63, which meets the requirements of the design specification manual (Kd 5). According to the squirrel-cage motor no-load starting current duration is 5s, and taking into account that if three 6kV motors are started simultaneously, the starting current reaches 487A, which is greater than 457A. Therefore, the action delay of over-current protection takes 6s. As for other protection, Calculate according to conventional settings.
4 Concluding remarks During the trial operation of Lianzhou Power Plant desulfurization system, several 6kV work section power outages occurred suddenly. However, when automatically switching to the standby section or switching to another 6kV work section, two transformers can be avoided at the same time. Magnetizing inrush current and starting current of 3 sets of 6kV motors. It shows that the electrical system design is reliable, the setting calculation is correct, and the safe operation of the desulfurization system is ensured. : Rayong (1963-), male, Xingning, Guangdong, power system automation engineer, mainly engaged in relay protection debugging and automatic device development.
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