Power plant interview question


#1

What are the main circuits in the Thermal Power Plant?

  • Feed water and steam flow circuit
  • Coal and ash circuit
  • Air and gas circuit
  • Cooling water circuit

On which cycle thermal power plant works?

Thermal power plant works on Rankine Cycle.

The Rankine cycle is an idealized thermodynamic cycle of a thermal engine that converts heat into mechanical work. In this mechanism, fuel is used to produce heat inside a boiler, converting water into steam that then expands through a turbine that produces useful work.

On what factors efficiency (thermal) of the steam plant depends?

The efficiency of the thermal plant depends on three factors, they are

  1. pressure of steam entering the turbine
  2. temperature of the steam entering the turbine
  3. pressure in the condenser

What is the purpose of deaerator in the steam power plant?

The purpose of the deaerator is to reduce the dissolved oxygen content in the condensate (feed water) by increasing its temperature. These gases are removed in the deaerator by heating the feed water at saturation temperature through the steam of the turbine.

Why cooling towers require in the Steam power plant?

The cooling towers cool the hot water discharged from the condenser and return the cooled water to the condenser. There are two types of cooling methods provided in the cooling towers, which may be of the wet type or of the dry type.

What are the different auxiliary systems in the thermal power plant?

Coal handling and coal storage, coal pulverizes the water treatment plant, steam boiler, drought systems, ash management systems, steam turbine, water circulation system, electrical systems, control and instrumentation, control equipment of pollution and fire protection system.

What is the purpose of Pulverizes?

Pulverizers serve two purposes, to dry the coal and to grind the coal. They crush the coal to size of 74microns.

How efficiency of Thermal Plant can be improved?

  • By increasing the temperature and pressure of the steam entering the turbine

  • By reducing the pressure in the condenser

  • By reheating the steam between different stages between the turbine

Advantages and Disadvantages of Thermal Power Plant?

Advantages:

  • Thermal Power Plants can be operated near the load centres unlike hydro and nuclear plants

  • Requires less space compared to hydro plants and cost of construction is less

  • Running or operating costs are less compared to diesel or gas plants

  • Can able to handle over load for a certain period of time

Disadvantages:

  • Emits greenhouse gases and causes pollution.

  • Coal and Ash handling requires the large area

  • Efficiency is low

What are different types of circuit breakers employed in thermal power plant?

For low voltage operation, 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.

What are the different Generator Protections employedOverloadal Power Plants?

Faults in the windings, Over load protection, Over heating of windings or bearings, Over speed protection, Loss of Excitation protection, Motoring operation protection, Inadvertent energisation, single phase or unbalanced current protection, out of step operation protection, sub-synchronous oscillations protection and earth fault protection.