{'fraction_non_alphanumeric': 0.016755521706016754, 'fraction_numerical': 0.0, 'mean_word_length': 5.4411764705882355, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Research on the volute pressure in start-up process of hydroelectric generating units

The dynamic quality in start-up process of hydroelectric generating units has a direct influence on power system stability and economic benefits of hydropower stations. However, the existing researches just focus on the rapidity and stability of unit rotation speed, never analyze the volute pressure or other control conditions, and ignore the security of unit operation. This paper strongly emphasizes that the volute pressure should be regarded as an important evaluation index in analysis of start-up process. By using a nonlinear mathematical model which takes into account the turbine characteristics and elasticity of the pipeline, this article calculates and analyzes the start-up transient process of hydroelectric generating units to seek the change law of volute pressure, and the engineering example is a hydropower station with the surge chamber and long draw water tunnel. To discuss the influence factors of the volute pressure, this paper also makes sensitivity analysis of start-up strategy, start-up working conditions and characteristics of pipeline. Meanwhile, according to various factors, this paper provides some suggestions to guarantee the rapidity and security of the start-up process simultaneously.