The synchronizing process is supervised so that if it lasts for more than a predetermined period, a synchronizing alarm will be initiated causing the set to be stopped and further starting attempts to be blocked.
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Home exercise. Read the text. Divide it into logical units. Point out in English in written form what main themes are dwelt upon. Then in a few words express the main idea of each passage.
Part IV. Starting Program for Diesel and Turbo Alternators
If the load on the sets in service should exceed a certain percentage of the rated output, a new set must be connected in. That level is normally 80 percent. However, in some systems the levels for starting a new set are detected on the basis of the sum of all the sets then in service, e. g. the total power available. This arrangement allows for better utilization of the sets. In order to avoid starting a new set as a result of the appropriate level being temporarily, e. g. when starting a new consumer with a large starting current demand, the starting instruction is delayed by an adjustable period.
On receipt of automatic starting order, the prelubrication pump will first be started and when its pressure switch delivers a signal to indicate that the oil system is pressurerized, the solenoid of the starting air valve will be energized. The supply of starting air is maintained until the ignition speed has been exceeded or for a predetermined maximum period, normally 5 s. If the engine fails to start, the attempt is repeated, normally twice, at an interval of about 5 s. If all starting attempts have failed, the “starting failure” alarm will be initiated. This alarm will also be initiated if the engine has failed to attain normal speed after a predetermined period, normally 30 s. When the ignition speed has been exceeded preexcitation is initiated by a contact function which persists until the voltage is acknowledged or an alarm is initiated. At this speed a time delay is also initiated for activating certain alarms, e. g. alarms for low voltage, low frequency and low lubricating oil pressure.
The turbo is always started manually since it is never used as a stand-by set and the taking into operation of a turbo is based on the fact that you know that the steam power supply will be sufficient for some time. Furthermore, there are often certain visual checks to be done when starting up a turbo.
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Home exercise. Check vour reading skills. See ex. 32, Section I, Unit 2.
Part V. Supervision 20
Each set is protected against damage which could occur in the event of deviation from normal values. Such deviations are sensed by means of transmitters in the automatic equipment or on the set. If a fault is detected, an alarm will be initiated but this can be delayed for up to 60 s.