Introduction to Hydro Power Plant

Introduction to Hydro Power Plant

A hydro power plant has an advantage in that it does not need fuels for its operation as compared with oil or thermal power plants. However, there are no differences between both types of plants in that appropriate operation and maintenance (O&M) are essential for their long-term operation. They can be operated for long periods if its facilities are properly operated and maintained. We should effectively utilize hydro power because aside from being an indigenous energy resource, it is also renewable.

We have to operate and maintain micro-hydro power plants with strict compliance to the operation and maintenance manuals. In general, operators of micro-hydro power plants should understand the following:

（１）Operators must efficiently conduct operation and maintenance of a plant complying with the work plans, rules and regulations.

（２）Operators must familiarize themselves with all the plant components and their respective performance or corrective and preventive functions. Furthermore, they must also be aware of measures against various accidents for prompt recovery.

（３）Operators must always check conditions of facilities and equipment. When they find some troubles or accidents, they must inform a person in charge and try to remedy the situation.

（４）Operators must try to prevent any accidents. For this purpose, they should repair or improve facilities preventively as necessary. Operation and maintenance manuals should basically be prepared for each plant

individually before the beginning of operation. The following are general manuals of

operation and maintenance for micro-hydro power plants.

Energy in Afghanistan and Afghanistan Power System Structure

 Energy in Afghanistan is primarily provided by hydro-power. According to the World Bank, approximately 84.1% of Afghanistan's population has access to electricity. Some rural areas, however, may not get 24-hour electricity but this will change once the major CASA-1000 project is completed in 2020.

According to Da Afghanistan Breshna Sherkat (DABS), Afghanistan generates around 300 megawatts (MW) of electricity mainly from hydro power followed by fossil fuel and solar. About 1,000 MW more is imported from neighboring Uzbekistan, Tajikistan, Iran and Turkmenistan.

Due to the large influx of expats from neighboring Pakistan and Iran, Afghanistan may require as much as 7,000 MW of electricity in the coming years.The Afghan National Development Strategy has identified alternative energy, such as wind and solar energy, as a high value power source to develop.

As a result, a number of solar and wind farms have been established, with more currently under development.

Frequency Control Of a Power System

  Frequency Control Of a Power System

How can the system frequency of a larger power system be adjusted without affecting the power sharing among the system generators?

It can’t unless each generator has room to move up and down in its allowed power output band. The power output band is defined as its maximum capacity minus its minimum capacity. Each generator has a maximum power output based on the unit size and a minimum power output based on both economics and engineering.

The frequency is determined by the ratio of load to generation. If there is too much generation then the frequency will rise. If there is too little generation then the frequency will drop. Assuming the load is fixed, the generation output has to be changed to adjust the frequency. If the balance of generation or the share of total output is to remain the same, then each generator has to be able to move up or down in its power output band to adjust the system frequency. Now this will never happen due to economics.

Each generator has a cost curve which dictates the price at each output range the generator will bid at. In the electric market the system will use the cost curves to find the most economical dispatch. This means some units with a lower price will be 100% committed to their maximum output while other more expensive units may be committed at their lowest output or below maximum.

The cost is dictated by several factors such as startup costs, fuel costs, and operations and maintenance (O&M) costs among others. At the Pmin - minimum power output the cost will be comprised of a startup cost plus fuel costs etc... As the units output rises, the startup cost stays fixed but the fuel and O&M costs rise.

The system frequency will be maintained by bringing generators online and offline in an economical order. As load rises the higher costs units will be brought online as all the lower units are already committed and generating.

Selecting Pole Positions and Pole Top Construction For MV Line

Selecting Pole Positions and Pole Top Construction For MV Line

For pole positioning guidelines.

Firstly, position poles along the route at any key or constrained locations.

Next determine the maximum span length that can be achieved over flat ground given the attachment heights on poles, the sag at the nominated stringing tension and the required ground clearance. Also check the spanning capability of the pole top constructions to be used. Position poles along the route so that this spacing is not exceeded. If there are gullies between poles, the spacing can be increased and if there are 'humps' mid-span, span lengths can be reduced.

Strain Points, Pole Details and Pole Top Constructions have to be determined. Strain point locations need to be determined:

1) To isolate electrically different circuits.

2) To keep very short spans or very long spans mechanically separate, such that all spans in a strain section are of similar length (no span less than half or more than double the ruling span length, and on tight-strung lines, the longest span not more than double the shortest span). Failure to limit span variance can cause excess sagging in longest span at higher design temperature loadings.

3) To isolate critical spans, e.g. spans over a river, major highway or railway line, to help facilitate repairs or maintenance.

4) On line deviation angles too great for intermediate constructions, e.g. Cross-arms with pin insulators.

5) At locations where there are uplift forces on poles.

6) At intervals of approximately 10 spans or so.

The following points also must be considered:

1) Strain section length limitation will be favorable if a line is affected by wires brought down in a storm. Also, the length of conductor on a drum may be a consideration.

2) Span lengths within the strain section must be reasonably similar and poles and pole top construction used must be reasonably consistent, as this gives the line a tidy appearance.

3) When nominating suitable pole top constructions for intermediate poles, adequate capacity must be available for the deviation angle at each site.

4) Pole strengths and foundation types/sinking depths must be nominated as a first pass, as these may need to be amended later once tip loads are determined. Stronger poles will be required at terminations and on large deviation angles. Pole sinking depths can be determined.

Selection of Poles and Pole Tops For MV Line Design

 Selection of Poles and Pole Tops

Typical pole sizes are presented in when selecting poles, potential future sub-circuits and streetlight mounting must be considered, if these are identified / known during the design phase.

Apart from spanning and angular limitations, selecting a suitable pole top configuration should take in to account:

1) Life cycle suitability;

2) Reliability;

3) Suitability for the environment (vegetation, wild life, salt and/or industrial pollution levels); and

4) Ease of construction and maintenance.

Horizontal (flat) construction has the advantage of reduced pole height at the expense of a wider line and corresponding broader easement width.

Flat configurations are preferred in areas frequented by birds. For higher risk spans increasing conductor separation can reduce conductor flash-over due to bird impact. Attaching bird diverts on conductors is also effective as a visual warning to birds.

Delta pin configuration provides for both horizontal and vertical separation and helps reduce conductor clashing.

Overall, more compact pole top configurations are less visually obstructive. It is best to keep to reasonably consistent configurations to maintain visual amenity as well as maintain spanning capability and ease of conductor phasing.

Route Survey and Ground Line Profile for MV Line Design

 Route Survey and Ground Line Profile for MV Line Design

A ‘line route survey’ is carried out to determine:

a) Details of existing electricity infrastructure;

b) Terrain and site features, e.g. trees, access tracks, fences, gullies; and

c) Ground line rise and fall along the route.

Ground line profiling may not be necessary for minor projects in urban areas where the ground is reasonably level or has a consistent slope throughout and there are no on site obstructions.

The designer can check worst case ground clearances by deducting the sag in the span from the height of the supports at either end by taking the following measurements:

a) Conductor temperature

b) Conductor size/type

c) Ambient temperature

d) Conductor attachment point with respect to ground level

e) Strain points

However, ground line profiling is essential where:

1) Poles have to be positioned along an undulating traverse;

2) There is a 'hump' or change in gradient in the ground at mid span;

3) Outside of urban areas where spans are comparatively long-say in excess of 80 m;

4) The designer has doubts about the adequacy of required clearances; and

5) Where uplift on poles is suspected.

The equipment used to obtain measurements will depend on the complexity of the project. For many distribution lines, a simple electronic distance measuring device and inclinometer are adequate. Elsewhere, use of a high end GPS unit or LiDAR may be warranted. The route is broken up into segments, typically corresponding with 'knee points' or changes in gradient. Slope distance and inclination measurements for each segment can be converted to chainage and reduced level (RL) values to facilitate plotting as follows:

Software packages can be used to plot survey data. Apart from the ground line, various features and stations must be shown, including existing poles, gullies, fences, obstacles, roadways. A clearance line is then drawn offset from the ground line, according to the minimum vertical clearances that apply.

Selection of Conductor Size and Type For MV Line Design

 Selection of Conductor Size and Type For MV Design

Factors influencing selection include:

a) Load current and whether the line is 'backbone' or a spur;

b) Line voltage and voltage profile along the line;

c) Fault levels and line rating;

d) Environmental conditions – ambient temperature, vegetation, wildlife, pollution or salt spray;

e) Compatibility with existing adjacent electrical infrastructure;

f) Required span lengths and stringing tension; and

g) Future requirements with respect to distribution system planning.