Transmission Line Parameters And Its Losses Pdf
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- Transmission Line Parameters and Analysis
- Transmission Line Parameters and Analysis
- Electric power transmission
- Performance and modelling of AC transmission
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant , to an electrical substation. The interconnected lines which facilitate this movement are known as a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution. The combined transmission and distribution network is part of electricity delivery , known as the electrical grid. Efficient transmission involves reducing the currents by stepping up the voltage prior to transmission, and stepping it down at a substation at the far end.
Transmission Line Parameters and Analysis
Distribution Sector considered as the weakest link in the entire power sector. There are two types of transmission and distribution losses:. Technical Losses 2. Non-Technical Losses Commercial Losses. The technical losses are due to energy dissipated in the conductors, equipment used for transmission line, transformer, sub- transmission line and distribution line and magnetic losses in transformers. Technical losses are normally The major amount of losses in a power system is in primary and secondary distribution lines.
Therefore, the primary and secondary distribution systems must be properly planned to ensure within limits. The unexpected load increase was reflected in the increase of technical losses above the normal level Losses are inherent to the distribution of electricity and cannot be eliminated.
Fixed losses do not vary according to current. These losses take the form of heat and noise and occur as long as a transformer is energized. Fixed losses on a network can be influenced in the ways set out below:. Variable losses vary with the amount of electricity distributed and are, more precisely, proportional to the square of the current. By increasing the cross sectional area of lines and cables for a given load, losses will fall. This leads to a direct trade-off between cost of losses and cost of capital expenditure.
It has been suggested that optimal average utilization rate on a distribution network that considers the cost of losses in its design could be as low as 30 per cent. Main Reasons for Technical Losses. Thus, the primary and secondary distributions lines in rural areas are largely radial laid usually extend over long distances.
This results in high line resistance and therefore, high I2R losses in the line. Inadequate Size of Conductors of Distribution lines. The size of the conductors should be selected on the basis of KVA x KM capacity of standard conductor for a required voltage regulation but rural loads are usually scattered and generally fed by radial feeders.
The conductor size of these feeders should be adequate. Installation of Distribution Transformers away from Load Centers. Distribution transformers are not located at load center on the secondary distribution system. In most of case, distribution transformers are not located centrally with respect to consumers. Consequently, the farthest consumers obtain an extremity low voltage even though a good voltage levels maintained at the transformers secondary.
This again leads to higher line losses. The reason for the line losses increasing as a result of decreased voltage at the consumers end.
Therefore, in order to reduce the voltage drop in the line to the farthest consumers, the distribution transformer should be located at the load centre to keep voltage drop within permissible limits. In most LT distribution circuits normally the power factor ranges from 0.
A low power factor contributes towards high distribution losses. For a given load, if the power factor is low, the current drawn in high and losses proportional to square of the current will be more. Thus, line losses owing to the poor PF can be reduced by improving the power factor. This can be done by application of shunt capacitors.
A more appropriate manner of improving this PF of the distribution system and thereby, reduce the line losses is to connect capacitors across the terminals of the consumers having inductive loads. Bad Workmanship contributes significant role towards increasing distribution losses. Joints are a source of power loss.
Therefore, the number of joints should be kept to a minimum. Proper joining techniques should be used to ensure firm connections. Connections to the transformer bushing-stem, drop out fuse, isolator, and LT switch etc should be periodically inspected and proper pressure maintained to avoid sparking and heating of contacts.
Replacement of deteriorated wires and services should also be made timely to avoid any cause of leaking and loss of power. One of the easiest loss savings of the distribution system is balancing current along three-phase circuits. Feeder phase balancing also tends to balance voltage drop among phases giving three-phase customers less voltage unbalance.
Feeder phase unbalance may vary during the day and with different seasons. Similarly, balancing load among distribution feeders will also lower losses assuming similar conductor resistance. This may require installing additional switches between feeders to allow for appropriate load transfer. Power consumption of customer varies throughout the day and over seasons. Residential customers generally draw their highest power demand in the evening hours.
Same commercial customer load generally peaks in the early afternoon. Because current level hence, load is the primary driver in distribution power losses, keeping power consumption more level throughout the day will lower peak power loss and overall energy losses.
Load variation is called load factor and it varies from 0 to 1. For example, for 30days month hours peak load of the feeder is 10 MW. Lower power and energy losses are reduced by raising the load factor, which, evens out feeder demand variation throughout the feeder. Companies use pricing power to influence consumers to shift electric-intensive activities during off-peak times such as, electric water and space heating, air conditioning, irrigating, and pool filter pumping.
With financial incentives, some electric customers are also allowing utilities to interrupt large electric loads remotely through radio frequency or power line carrier during periods of peak use. Utilities can try to design in higher load factors by running the same feeders through residential and commercial areas. Distribution transformers use copper conductor windings to induce a magnetic field into a grain-oriented silicon steel core.
Therefore, transformers have both load losses and no-load core losses. For some utilities, economic transformer loading means loading distribution transformers to capacity or slightly above capacity for a short time in an effort to minimize capital costs and still maintain long transformer life.
However, since peak generation is usually the most expensive, total cost of ownership TCO studies should take into account the cost of peak transformer losses. Increasing distribution transformer capacity during peak by one size will often result in lower total peak power dissipation-more so if it is over loaded.
Transformer no-load excitation loss iron loss occurs from a changing magnetic field in the transformer core whenever it is energized. Core loss varies slightly with voltage but is essentially considered constant. Fixed iron loss depends on transformer core design and steel lamination molecular structure.
Improved manufacturing of steel cores and introducing amorphous metals such as metallic glass have reduced core losses. Balancing 3-phase loads periodically throughout a network can reduce losses significantly. It can be done relatively easily on overhead networks and consequently offers considerable scope for cost effective loss reduction, given suitable incentives. One method of reducing fixed losses is to switch off transformers in periods of low demand.
If two transformers of a certain size are required at a substation during peak periods, only one might be required during times of low demand so that the other transformer might be switched off in order to reduce fixed losses. This will produce some offsetting increase in variable losses and might affect security and quality of supply as well as the operational condition of the transformer itself.
However, these trade-offs will not be explored and optimized unless the cost of losses are taken into account.
T system causing high neutral currents. Non-technical losses are at Main Reasons for Non-Technical Losses. Theft of power is energy delivered to customers that is not measured by the energy meter for the customer. Customer tempers the meter by mechanical jerks, placement of powerful magnets or disturbing the disc rotation with foreign matters, stopping the meters by remote control. Losses due to metering inaccuracies are defined as the difference between the amount of energy actually delivered through the meters and the amount registered by the meters.
All energy meters have some level of error which requires that standards be established. Measurement Canada, formerly Industry Canada, is responsible for regulating energy meter accuracy. Old technology meters normally started life with negligible errors, but as their mechanisms aged they slowed down resulting in under-recording.
Modern electronic meters do not under-record with age in this way. Consequently, with the introduction of electronic meters, there should have been a progressive reduction in meter errors. Increasing the rate of replacement of mechanical meters should accelerate this process.
Unmetered losses are situations where the energy usage is estimated instead of measured with an energy meter. This happens when the loads are very small and energy meter installation is economically impractical. Examples of this are streetlights and cable television amplifiers. Unmetered supply to agricultural pumps is one of the major reasons for commercial losses. In most states, the agricultural tariff is based on the unit horsepower HP of the motors.
Such power loads get sanctioned at the low load declarations. Once the connections are released, the consumers increase their connected loads without obtaining necessary sanction for increased loading from the utility.
Most of the utilities deliberately overestimate the unmetered agricultural consumption to get higher subsidy from the State Government and also project reduction in losses.
Moreover, the correct estimation of unmetered consumption by the agricultural sector greatly depends upon the cropping pattern, ground water level, seasonal variation, hours of operation etc. Proper Calibrated Meter should be used to measure electrical energy.
Defective Energy Meter should be replaced immediately. The reason for defective meter are burning of meters, burn out terminal box of meter due to heavy load, improper C. T ratio and reducing the recording, Improper testing and calibration of meters. Reducing Technical Losses. Many distribution pockets of low voltage V in town are surrounded by higher voltage feeders.
At this lower voltage, more conductor current flows for the same power delivered, resulting in higher I2R losses.
Transmission Line Parameters and Analysis
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Electric power transmission
Electric power transmission is the bulk movement of electrical energy from a generating site, such as a power plant , to an electrical substation. The interconnected lines which facilitate this movement are known as a transmission network. This is distinct from the local wiring between high-voltage substations and customers, which is typically referred to as electric power distribution.
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Performance and modelling of AC transmission
Bamigbola, M. Ali, K. A modern and civilized society is so much dependent on the use of electrical energy because it has been the most powerful vehicle for facilitating economic, industrial, and social developments. Electrical energy produced at power stations is transmitted to load centres from where it is distributed to its consumers through the use of transmission lines run from one place to another. As a result of the physical properties of the transmission medium, some of the transmitted power is lost to the surroundings. The overall effect of power losses on the system is a reduction in the quantity of power available to the consumers.
According to the Department of Energy, California lost about The former occurs because of the non-zero resistance found wire's metal. Corona loss is an ionization of the air that occurs when the electric fields around a conductor exceed a specific value. Although the conductors in a transmission line have extremely low resistivity, they are not perfect. This section seeks to quantify that loss through computation of the skin depth and power attenuation factors.
Mathematical Modeling and Optimization of Industrial Problems
A transmission line is used for the transmission of electrical power from generating substation to the various distribution units. It transmits the wave of voltage and current from one end to another. The transmission line is made up of a conductor having a uniform cross-section along the line. Air act as an insulating or dielectric medium between the conductors. For safety purpose, the distance between the line and ground is much more. The electrical tower is used for supporting the conductors of the transmission line.
A transmission line is a wire with a uniform goemetry along its length. Some of the discussion involved losses on power transmission lines. The transmission line losses per transferred energy unit would then be lower for sctl because the losses are fixed. Why is a systems loss of power on a transmission line. At a frequency of 4 mhz a parallel wire transmission line has the following parameters. Its major function is to transport electric energy, with minimal losses. Power losses using the existing kv nigerian transmission network as a case study in his empirical modeling of power losses as a function of line loadings and lengths in the nigeria kv transmission lines has been considered 3.
Distribution Sector considered as the weakest link in the entire power sector. There are two types of transmission and distribution losses:. Technical Losses 2. Non-Technical Losses Commercial Losses. The technical losses are due to energy dissipated in the conductors, equipment used for transmission line, transformer, sub- transmission line and distribution line and magnetic losses in transformers. Technical losses are normally
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Performance modelling is the abstraction of a real system into a simplified representation to enable the prediction of performance. This can, however, point towards different things to people belonging to different fields of work. A model will often be created specifically so that it can be interpreted by a software tool that simulates the system's behaviour, based on the information contained in the performance model. Such tools provide further insight into the system's behaviour and can be used to identify bottlenecks or hot spots where the design is inadequate.
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