Electrical4U 
This is to be noted that, the star point or neutral point of stator winding of an alternator is grounded through an impedance to limit the ground fault current. Reduced ground fault current causes less damage to the stator core and winding during ground or earth fault. If the ground impedance is made quite high, … Read more
Various routine tests are performed for ensuring the quality, performance of a circuit breaker and these are Let us discuss them one by one. Power Frequency Over Voltage Withstand Test Power system can experience temporary overvoltage conditions due to various reasons, like sudden load changes or incorrect tap changer operations. The power frequency over voltage … Read more
The order of a control system is determined by the power of ‘s’ in the denominator of its transfer function. A control system is classified as second order when the highest power of ‘s’ in the transfer function’s denominator is 2. The general expression of the transfer function of a second order control system is … Read more
After installation of power transformer, several pre-commissioning tests must be performed before putting the transformer into service. Additionally, various instruments associated with the transformer should be checked. Common Pre-commissioning Tests of Transformer Insulation resistance values of various winding should be checked. During measurement of insulation resistance, the transformer must not be connected with any external … Read more
Differential protection is primarily used to clear any internal faults in the stator winding of a generator or alternator.The differential protection is provided in the generator by using longitudinal differential relay.instantaneous attracted armature type relays are commonly used because they operate quickly and are not affected by AC transients in the power circuit. There are … Read more
The relays used in power system protection are of different types. Among them differential relay is very commonly used relay for protecting transformers and generators from localised faults.Differential relays are very sensitive to the faults occurred within the zone of protection but they are least sensitive to the faults that occur outside the protected zone. … Read more
Electrolyte of Lead Acid Battery The electrolyte of a lead acid battery cell is a solution of sulfuric acid and distilled water. The specific gravity of pure sulfuric acid is about 1.84 and this pure acid is diluted by distilled water until the specific gravity of the solution becomes 1.2 to 1.23. However, in some … Read more
A generator is subjected to electrical stresses imposed on the insulation of the machine, mechanical forces acting on the various parts of the machine, and temperature rise. These are the main factors which make protection necessary for the generator or alternator. Even when properly used, a machine in its perfect running condition does not only … Read more
Inter turn stator winding fault can easily be detected by stator differential protection or stator earth fault protection. Hence, it is not very essential to provide special protection scheme for inter turn faults occurred in stator winding. This type of faults is generated if the insulation between conductors (with different potential) in the same slot … Read more
The rotor of an alternator is wound with field winding. A single earth fault in the field winding or exciter circuit is not a major issue. However, if multiple earth faults occur, they can cause short circuits between faulty points on the winding, leading to unbalanced magnetic field and potential mechanical damage to the machine’s … Read more