Wind Energy Assessment Questions on “Effects of Wind Speed and Grid Condition (System Integration) – 1”.
1. Why is the energy output of wind power plant variable?
a) Wind speed is variable
b) Wind speed is an unknown constant
c) Wind speed is known constant
d) Poor equipment is used
Answer: a
Clarification: The energy output of any wind power plant (WPP) is variable because the wind speed is variable. The equipment used in power plant is designed to deal with such variability and uncertainty.
2. Which of the following is a reason for variable wind speed?
a) Water
b) Earth’s rotation
c) Electrons
d) Fans
Answer: b
Clarification: Day and night cycle caused by earth’s rotation and seasonal changes due to tilt axis of earth cause changes in wind speed. Water, electrons and fans do not affect wind speed.
3. What is grid integration of wind energy?
a) Planning the connection of wind power plant to the grid
b) Physical connection of wind power plant to the grid
c) Energy sent from grid to run the wind turbines
d) Collection of all activities related to connecting wind power plants to the grid
Answer: d
Clarification: Grid integration of wind energy is simply the collection of all activities related to connecting wind power plants to the grid. The wind power plant sends energy to the grid. It does not consume energy from the grid.
4. Which of the following depicts the correct order of the stages involved in grid integration of wind energy?
a) System operations → physical connection → planning
b) Planning → system operations → physical connection
c) Planning → physical connection → system operations
d) Physical connection → planning → system operations
Answer: c
Clarification: Grid integration of wind energy consists of three stages starting with planning the connection. After laying out the plan, the power plant is physically connected to the substation (grid). Lastly, the functioning of each system is handled under systems operation.
5. What are the two types of planning activities related to grid integration?
a) Network-wide and project-specific
b) BJT and MOSFET
c) Rotor and shaft
d) Low power and high power designs
Answer: a
Clarification: The two types of planning activities related to grid integration are network-wide and project-specific activities. BJT and MOSFET are electronic/electrical devices (components). Rotor and shaft are used in a rotating mechanism. Low power and high power designs are circuit design specifications.
6. Which of the following best describes network-wide planning activity in grid integration?
a) Planning activities related to a unique wind project
b) Planning activities for all the future wind power plants
c) Planning activities for a telecommunication system
d) Planning activities for the maintenance of the existing wind power plants
Answer: b
Clarification: Network-wide plans are laid out for all the future wind power plants. Planning activities for a telecommunication system are not related to grid integration of wind energy. Maintenance of existing wind power plants is covered in the previous network-wide plan.
7. Network-wide plans in wind energy grid integration include _______
a) system impact studies done for a specific wind project
b) materials used to manufacture wind turbine blades
c) developing grid code
d) solar panel manufacturing plant
Answer: c
Clarification: Network-wide plans include development of grid code, network-wide system integration studies with scenarios for different levels of wind penetration and system operation studies. They are not done for a specific wind project.
8. What is project specific planning in wind energy grid integration?
a) Planning activities for a solar panel system
b) Planning activities for all the future wind power plants
c) Planning activities related to a unique wind project
d) Planning activities for the maintenance of the existing thermal power plants
Answer: c
Clarification: Project specific planning activities in wind energy grid integration are planning activities related to a unique wind project. They include system impact studies done for a specific wind project. The input for this type of study is the wind power plant which is being studied.
9. In a substation, the wind power plant line is connected to a _______ voltage bus bar.
a) high
b) low
c) mini
d) medium
Answer: d
Clarification: In a substation, the wind power plant line is connected a medium voltage bus bar. A medium voltage bus bar is used for medium voltages – 10kV to 50kV. At the wind turbine generator, this bar is connected to a step up transformer which steps up the output of the generator from 0.69kV to 11kV or 33kV.
10. Which of the following are a few primary tests performed after commissioning phase in the physical connection stage?
a) Switch-gear functioning and quality parameters
b) Feathering
c) Wind turbine blade tests
d) Rotor and shaft tests
Answer: a
Clarification: Testing the functioning of switch-gear, quality parameters like harmonics and flicker, proper start-up and shut down are crucial during grid integration. Feathering of blades is done to prevent the blades from being damaged by storm winds. Wind turbine blade, rotor and shaft tests do not come under grid integration tests.
11. Which of the following are impacts of grid integration of wind power plant?
a) Day-ahead unit commitment process
b) Day-ahead unit commitment process, economic dispatch process
c) Generator types
d) Rotor and shaft tests
Answer: b
Clarification: The unit commitment process is cost-effective combination of generating units to meet forecasted load and reserve requirements, while adhering to generator and transmission constraints. Economic dispatch is the optimization of production from generators to minimize cost of generation while meeting all the constraints. In most grids, wind energy has the highest priority due to its low marginal costs.
12. Which of the following is/are good practices for grid integration of wind power plant?
a) Day-ahead unit commitment process
b) Day-ahead unit commitment process, economic dispatch process
c) Optimized transmission from resources-rich areas to load, flexible generation
d) Rotor and shaft tests
Answer: c
Clarification: Optimizing transmission from resource-rich areas to load saves both, power and costs. Using the under-utilized line to transmit power instead of setting a new transmission line is an example of optimization. Flexible power generation helps meeting in varying power demands.
13. What is a grid code for wind energy integration?
a) A binary code
b) A hexadecimal code
c) A code of conduct
d) A rulebook specifying generator properties
Answer: d
Clarification: A grid code for integration is a rulebook that specifies properties of generators and other equipment used to connect to the grid. The equipment must satisfy these properties to ensure reliable and safe operation.
14. What are the types of grid integration costs?
a) Transmission extension, volatility balancing, covering peak load
b) Marginal cost
c) Fixed cost
d) Fundamental Analysis
Answer: a
Clarification: Grid integration costs are divided into three categories – transmission extension, balancing of increased volatility in grid and covering the peak load. The other options are various terms used in economics and finance to define different types of costs. They are not particularly related to grid integration.
15. What is a power flow study in wind energy integration?
a) A binary code
b) Determines flow of electrical energy from generators to consumers
c) Determines flow of electrical energy from generators to consumers meeting line loading requirements
d) A study specifying generator properties
Answer: c
Clarification: A power flow study in wind energy integration determines flow of electrical energy from generators to consumers meeting line loading requirements and all grid code requirements. It is performed using various power systems modelling software like PSS/E and ETAP.