Interview Questions and Answers of Specialty Power System Electrical Engineering Set-1
1. What is the role of the transformer in the power system?
A: The transformer is an important electrical equipment in the power system, play a role in the transfer of electricity, from the power plant to the user's entire hair. Transmission process, the transformer plays a role in raising and lowering the voltage.
2. When the secondary side of the transformer short-circuit what is the danger?
A: The transformer secondary side of a sudden short circuit, the winding will have a huge short-circuit current, the value of up to 20 to 30 times the rated current, such a large current damage to the transformer are:
(1) under the action of a huge short-circuit current, the winding will produce a large electromagnetic force, its value up to 400 ~ 900 times the rated electromagnetic force, so that the mechanical strength of the winding damage;
(2) a huge short-circuit current will make the winding heat, resulting in high temperature, may cause the winding burned.
3. What are the conditions of parallel operation of the transformer?
A: Two or more transformers running in parallel conditions: (1) high and low voltage side of the rated voltage are equal, the actual operating ratio should be equal; (2) to connect the same group; (3) short-circuit voltage per unit value (Percentages).
4. Why should the provisions of the allowable temperature of the transformer?
A: Because the higher the operating temperature of the transformer, the faster the insulation aging, not only affects the service life, but also because of insulation brittle and fragmentation, the loss of insulation winding protection. In addition, the higher the temperature the lower the dielectric strength of insulating materials, it is easy to be high voltage breakdown caused by failure. Therefore, the transformer can not exceed the permissible value during operation.
5. What are the basic structure of the synchronous generator?
A: The stator includes: stator core, stator winding, frame, end cover, cooler and so on. The rotor includes a rotor core, a rotor winding, an inter-ring, a slip ring, a fan, and the like.
6. Synchronous generator "synchronization" What does this mean?
A: After the three-phase symmetrical load is applied to the generator, the three-phase symmetrical stator current produces a combined magnetic field which is in the same direction as the rotor and rotates at the same speed.
7. Synchronous generators according to the rotor magnetic pole shape how to classify? What are uses in the power plants?
A: The synchronous generator according to the rotor pole shape is divided into salient and hidden pole machine. Salient pole machine is usually more pole pairs, the rotor speed is low, generally used in hydropower plants.The hidden pole machine is usually a small number of pole, the rotor speed is high, usually in thermal power plants. Thermal power plants and nuclear power plants to use.
