The excitation control method is satisfactory only for relatively short lines. However, it is not suitable for long lines as the voltage at the alternator terminals will have to be varied too much in order that the voltage at the far end of the line may be constant. Under such situations, the problem of voltage […]
TAP CHANGING TRANSFORMERS Read More »
When the load on the supply system changes, the terminal voltage of the alternator also varies due to the changed voltage drop in the synchronous reactance of the armature. The voltage of the alternator can be kept constant by changing the field current of the alternator in accordance with the load. This is known as
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In this type of regulator, exciter field rheostat is varied continuously or in small steps instead of being first completely cut in and then completely cut out as in Tirril regulator. For this purpose, a regulating resistance is connected in series with the field circuit of the exciter. Fluctuations in the alternator voltage are detected
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In this type of regulator, a fixed resistance is cut in and cut out of the exciter field circuit of the alternator. This is achieved by rapidly opening and closing a shunt circuit across the exciter rheostat. For this reason, it is also known as vibrating type voltage regulator. CONSTRUCTION OF TIRRIL REGULATOR Figure shows
WHAT IS VOLTAGE CONTROL? In a modern power system, electrical energy from the generating station is delivered to the ultimate consumers through a network of transmission and distribution. For satisfactory operation of motors, lamps and other loads, it is desirable that consumers are supplied with substantially constant voltage. Too wide variations of voltage may cause
DC Ground detectors: are the devices that are used to detect/indicate the ground fault for ungrounded DC systems. When a ground fault occurs on such a system, immediate steps should be taken to clear it. If this is not done and a second ground fault happens, a short circuit occurs. Lamps are generally used for
A booster is a DC generator whose function is to inject or add certain voltage into a circuit so as to compensate the IR drop in the feeders etc. A booster is essentially a series DC generator of large current capacity and is connected in series with the feeder whose voltage drop is to be
The devices in switching equipment are referred to by numbers, with appropriate suffix letters when necessary, according to the functions they perform. These numbers are based on a system adopted as standard for automatic switchgear by IEEE, and incorporated in American Standard C37.2-1970. This system is used in connection diagrams, in instruction books, and in specifications.
PROTECTIVE DEVICES AND THEIR FUNCTIONS Read More »
External faults are those faults or hazards that occur outside the transformer. These hazards present stresses on the transformer that may be of concern and may shorten the transformer life. These faults include the following. • OVER LOADS Overloads cause the transformer to overheat and have the potential to cause permanent damage or loss of
TRANSFORMER EXTERNAL FAULTS Read More »
Overheating of a synchronous generator may occur due to one of the following causes: 1. Overload 2. Failure of the ventilation or hydrogen cooling system 3. Shorted laminations in the stator iron 4. Core bolt insulation failures in the stator iron Excessive overload is not likely since the prime mover rating is usually not much
GENERATOR OVERHEATING PROTECTION Read More »