tailieunhanh - Lesson 21- Power Station Automation

Tham khảo tài liệu 'lesson 21- power station automation', ngoại ngữ, anh văn thương mại phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lesson 21- Power Station Automation With regard to the functions of the power station automation people may fill up a long list as follows 1 The automatic starting of generating sets. 2 The automatic switching on after electrical voltage is established. 3 The automatic adjustment of electrical voltage. 4 The automatic unloading by different stages of secondary electrical users when generators are overloaded. 5 The automatic parallel of generators. 6 The automatic regulation of frequency and load of generators after their being paralleled. 7 The automatic load transfer before a generator is out of service. 8 The automatic switching off in the case of generator failure. Nowadays first priority has been given to an A. C. power station for common vessels and the generators of self excitation and constant voltage are widely adopted. By the self excitation it means that the excitation needed will be supplied by a generator itself when it is in operation. By the constant voltage it is meant that a generator is equipped with a compound excitation device which is capable of compensating the voltage fluctuation and thus keeping the voltage within the allowance when the generator voltage fluctuates due to load changes. Generators may be overloaded in service owing to the increase of additional loads. In order to ensure the continuity of power supply and protect the generators from overloading it is necessary to unload some of the electrical users. These years the automatic unloading device for the marine power station is either of transistor loop or composed of relay contactor which automatically unloads some secondary electrical users by different stages and ensures the continuous power supply of the other primary electrical users. In case a marine power station is armed with two or more generators it is frequently required to run them in parallel so as to obtain the continuity and economy of power supply. In respect to A. C. generators it is allowed for them to be .