Choice in Selecting Type of Power Generating Station

Power Generating Station

POWER GENERATING STATION 

Power generating station: The necessity of Electrical power energy increases daily. This form of energy can be gotten from a power station or cheaper from any close to the grid. A grid is an infinite busbar, having alternators connected in parallel to it. Well, if there be any nearby grid, then power can be gotten through the grid authority. Electrical power gotten from the grid is received by transmission substation, then distributed to a distribution substation. Meanwhile, there could be a local power station or a bulk supply unit, and the choice of any is factored on economics. However, the determination of any is then further considered on the type and location.

It’s quite necessary to lay consideration on the physical location of power generating station, transmission, and distribution substation. This will economically help the system. Most power stations are located close to where their energy source is present. The importance of this is to reduce the expenses of transporting this energy(coal, oil, or gas) to where the power station is located. 

Although, power stations could be near or far away from consumers. Meanwhile, building a power station could take a duration of 2-4 years. This duration is factored on the size and amount of civil work required on site. For this reason, the capital it placed for several years before the return is recovered on the money invested. So, you made want to consider it as a long time investment.

Selection of Type of Power Generating Station 

There are different types of power generating stations. However, selecting any type of power generating station is factored on the following consideration:

  • In power stations, electrical power is generated from other sources of energy. So, the availability of energy sources and the cost should be considered. Also, the nature of the load to be supplied. Meanwhile, since this whole process entails the emissions of heat energy, then the availability of suitable sites should be considered. These mentioned and even more should be considered when selecting the site of the power station.
  • For site selection of a power generating station, the system needs to consider the distance for which power will be supplied to the consumers. How good is the road, to transport the energy source like that of coal where it’s availability is not within the region of the power station. Proper roads should be put into consideration, else this might affect the vehicles for transportation. 
  • Again for site selection of power generating stations, the intensity of the soil should be considered also. The reason for this is that, in a power station, heavy-duty equipment will be mounted on the ground for the operation to take place. For steam power station, where the heat combustion from coal is used for the conversion process. Meanwhile, part of its disadvantages is the production of smoke and fume gases. This results in atmospheric pollution and this can be avoided by siting the power station away from the human population.  

Other factors to consider for power generating station selection:

Electrical power(electricity) generated is to be transmitted and also distributed. This process should be economical for the system and can be best seen when the power station is located at the center of gravity of the load. Although for the steam power station due to the fume gases emitted, it’s preferable for the power station to be situated away from the city. Other factors to consider includes:

  • Degree of system reliability 
  • Governmental taxes 
  • Depreciation and interest rate 
  • Cost of Energy Source 
  • Land cost and size
  • Power Plant cost and size
  • Availability of water supply for prime movers or  cooling engine 
  • Strength of foundation 
  • Cost of purchasing power
  • Storage Space for Energy source 
  • Nature of load to the supplied 
  • Transport facilities.

Prime mover is a device that helps to convert the dry steam from the burner into mechanical energy. The alternator makes use of this mechanical energy and converts it to three-phase electrical power.

Center of Gravity of Load in power generating station 

Placing of the power station at its load center of gravity makes it more economical for distribution. Although, this isn’t applicable for all types of power stations. Like Hydroelectric power station, which requires a suitable site should be located remotely away from the population of humans. Therefore, they can’t be located at the center of gravity of the load. As such, they will require longer transmission to get power to their load center. 

For a single power station which is not interconnected by a network of transmission line with other stations. The center of the load can be determined as stated below:

Let’s assume we got four load center represented with A.B.C.D, whose demands is in KVA. Meanwhile, the position of the load can be formulated as:

Position of load = sum of moments/sum of loads

The moment of the load is with respect to its coordinate axis(x,y). The load position coordinates help to determine the position of the power station.

Terms Associated with Power Supply 

Connected load: This term is used to measure the total load equipment installed at the consumer’s end. The power rating is rated in KW(kilowatt). It’s expected to know that, the consumption of electrical power(electricity) is paid for by the consumers. This is known as Electricity Traffic.

Recommended: What is Electricity Traffic and its Type

Demand factor and Maximum demand: Load used by consumers varies, being maximum during the day and minimum during the night. Meanwhile, the maximum load consumed by the consumers is referred to as Maximum demand. On the other hand, the ratio between the maximum load demand and that of the connected load is referred to as Demand factor. 

Demand factor = Maximum demand/ Connected load 

Load factor: Loads are subjected to variation, and it’s dependent on consumers’ usage. Statistically, the load becomes maximum during the day and it becomes minimum at the remaining time of the day, usually the night. Moreover, we have seen that maximum load demand is the highest load consumed during the 24hours. Well, the total energy consumed during the 24 hours is referred to as the average load. Meanwhile, on the load curve, the average load is less than the maximum. However, the ratio between the average load and the maximum load Is referred to as the load factor.

Load factor = Average Load/Maximum Load

Understanding Diversity Factor 

Before an electric power is supplied to a consumer, both his maximum load demand and the average load is known. We have seen what these two are and the power supplied capacity is based on both the maximum demand and average load. However, when the load capacity supplied to the consumer is being utilized throughout the day. When this occurs, it means that the maximum demand and the average load are equal. That is, the load would be 100% and that the consumer made use of the available energy. Therefore, we can say that the consumer’s load factor is 100%. In such cases, the cost of electricity per kilowatt-hour would be minimum.

Again, when this supplied capacity is not being utilized throughout the day. This means that the maximum load demand is not equal to the average load. The load factor becomes less than 100% and the cost of electricity per kilowatt-hour will be high. Although, in reality, a 100% load factor is not possible. Owing to different consumers with different maximum loads. Meanwhile, these consumers could have the same maximum loads but these loads could be utilized at a different point in time.

This creates the necessity to meet up the load demand and at the same time ensure a smooth load characteristic curve. Let’s say there exist five load consumers with the same maximum demand. Well, despite the same maximum demand, these loads will still be operated at different times intervals because every load consumers have different habits. Therefore, this creates a diversity in the occurrence of the loads. 

So, the ratio of the sum of the maximum demand of each consumer to the simultaneous maximum demand of the total consumers at a particular time is known as the DIVERSITY FACTOR.

Plant Capacity of Power Generating Station

Another term used for power supply in power generating stations in the plant capacity. Well, both the load factor and the diversity factor can’t really tell the actual reserved power capacity in the power generating station. However, the factor to be considered to tell the reserved capacity required in a station is known as the plant capacity. Meanwhile, the plat capital is actually the ratio between the actual energy produced in a power generating station and the maximum possible energy that could have been produced during the same period. 

Plant Use Factor

Same as the plant capacity factor but taken for either a day or annually. Considering for a day, it will be the area under the load curve divided by the overall plant capacity installed in the station. This actually includes the reserved plant in kilowatts, then multiplied by 24hours. Meanwhile, when considered annually, it will be the annual energy produced in kilowatts-hour divided by the capacity of the plant(KW) then multiplied by the number of hours plant is in operation for a year.

However, the reserved capacity installed in the station is considered from the difference between the load factor and the plant capacity factor. Nevertheless, the choice in selecting the generator unit’s size and the number of units can be from the compromising between the plant use factor and the plant capacity factor. So, let’s take a look at the choice in selecting the number of units and of the size of the generator units.

Generator Units Size and Number it Unit Selection 

The whole essence of a power station is to supply the load connected to it. Meanwhile, the load connected to it varies, they aren’t stable due to load extendibility and different duration of load usage by different consumers. Moreover, high load variation results in a poor load factor. Nevertheless, the minimum power capacity present in a power station should be able to cater for the maximum load demand. Therefore, a single unit can be considered but the alternator and prime mover will have to operate at his full load. This will be only for a short period of time. 

Power Generating Station

Although, due to the variation in load, causing the load factor to less than 100%. In such a case, the load on the station or a single unit in the station could be less than the full load. Maybe half or even at no load at all. Therefore, the generating set won’t be in operation at all time giving maximum efficiency. This effect will cost a lot for the plant. In that, it will increase the cost of fuel purchase and invariably becomes less economical to operate. 

Every power plant aims for continuity and reliability in supply, so no matter what choice to be made, this part of it must be considered too. So, it’s best to have two sets of units, like two means of supply just in case one is out. It becomes economical with two supply units because when one is out, the other can still serve the possible for reliability and continuity. There you have different types of power station arrangements, like that of type A series and type B series

Meanwhile, most power stations have room for extendibility just in case there’s enough capital to make it up. 

Operating Schedule in power generating station 

The operating schedule of a power station, literally tells the sequence of operation to which each set of units operate. This is to ensure that an individual set fits appropriately on the load curve. Each unit should, therefore, be ready to fit in just in case of an interruption in the other. Therefore, the capacity of the plant started and kept ready might be larger than necessary. 

Conclusion 

To wrap things up, we have seen the necessity of Electrical power and with this, care must be made for energy reliability and continuity. With the known terms used in power supply, as explained in this course of study, one can easily tell what each represents. However, there’s always load variation due to different load consumers with different living habits. So, proper care must be made to cater for the maximum demand for the various number of consumers. All theses are being considered when selecting the type of power generating station.

Well, that’s all we have for the Selection of Type of Power Generating Station. Also, we got some other interesting articles on Electrical Engineering that will be of interest to you. So, feel free to check them out: Electrical Archive

Recommended:

  1. Parallel Operation of Alternators
  2. What is Steam Power Plant
  3. Overhead Line Design: STEPS TO TAKE
  4. Introduction to Electrical Energy
  5. Electrical Pole Dressing

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