Voltage stability of a system is affected by reactive power limit of the system. FACTs devices improve the reactive power flow in system thereby improving voltage stability and these are used for controlling transmission voltage, Power flow, dynamic response and reducing reactive losses in transmission lines.
WSCC 3-machine, 9-bus system has been used to demonstrate the ability of SVC in improving the voltage stability margin. These FACTs controllers help to increase the load ability margin of the power network. Authors are requested to submit articles directly to Online Manuscript Submission System of respective journal. Related article at PubmedScholar Google.
Their fast response offers a high potential for power system stability enhancement apart from steady-state flow control. Among the FACTS controllers, Static Var Compensator SVC provides fast acting dynamic reactive compensation for voltage support during contingency events which would otherwise depress the voltage for a significant length of time. The important operating tasks of power utilities are to keep voltage within an allowable range for high quality customer services.
Increase in the power demand has been observed all over the world in recent years. The existing transmission lines are being more and more pressurized. Such systems are usually subjected to voltage instability; sometimes a voltage collapse. Voltage collapse has become an increasing threat to power system security and reliability. The voltage stability is gaining more importance nowadays with highly developed networks as a result of heavier loadings.
Voltage instability may result in power system collapse. Voltage stability is the ability of power system to maintain steady acceptable voltages at all buses in the system under normal conditions . Voltage collapses the process by which the sequence of events accompanying voltage instability leads to a low unacceptable voltage profile in a significant part of the power system .
The main symptoms of voltage collapse are low voltage profiles, heavy reactive power flows, inadequate reactive support, and heavily loaded systems. The consequences of collapse often require long system restoration, while large groups of customers are left without supply for extended periods of time.
The voltage stability problem is associated with reactive power and can be solved by providing adequate reactive power support to the critical buses. The control of reactive power of a switched capacitor bank is usually discrete in nature.
Recent trend is to replace the switched capacitor banks by SVC to have a smooth control on reactive power. SVC has the capability of supplying dynamically adjustable reactive power within the upper and lower limits . In the normal operating region, a SVC adjusts its reactive power output to maintain the desired voltage. For such an operation, the SVC can be modeled by a variable shunt susceptance.
On the other hand, when the operation of the SVC reaches the limit, it cannot adjust the reactive power anymore and thus can be modeled by a fixed shunt susceptance. There are many methods currently in use to help in the analysis of static voltage stability.
The minimum singular value of the load flow Jacobian matrix is used as an index to measure the voltage stability limit is considered by reference . Energy method [6, 7] and bifurcation theory  are also used by some researchers to determine the voltage stability limit. Point of collapse method and continuation method are also used for voltage collapse studies . Of these two techniques continuation power flow method is used for voltage analysis.
These techniques involve the identification of the system equilibrium points or voltage collapse points where the related power flow Jacobian becomes singular [10, 11].
In this paper the following methods are used. Modal Analysis method is used to identify the weak bus by calculating participation factors and sensitivity factors. Two Bus Thevenin Equivalent method is used to determine the maximum loading capability of a particular load bus in a power system through the Thevenin equivalent circuit and also the loading capability of the bus after the placement of SVC device.
The SVC uses conventional thyristors to achieve fast control of shunt-connected capacitors and reactors. The configuration of the SVC is shown in Fig. The firing angle control of the thyristor banks determines the equivalent shunt admittance presented to the power system.Reactive power is an imaginary powerbut still, it is needed in the Power System.
If reactive power is in excess in Power System than voltage may go up and in case of shortage of reactive power voltage may be low. In this article, we will explain various aspects of reactive power, what its role is in Power System and how it can be injected into the Power System. It is desirable that the Voltage in Power System should be 1 per unit pu everywhere but it is highly impossible to maintain it. Control of reactive power and magnitude of voltage is almost co-related words; similarly, control of active power and angle of voltage is almost co-related words.
Consider Figure Bus-1 is connected with infinite bus with a long transmission line. Generally, Active power flows from high voltage angle to lower voltage angle and reactive power flows from higher voltage magnitude to lower voltage magnitude. It should be noted that reactive power is imaginary power so it can be supplied or absorbed by SG.
DC current in its field winding is low ; In that case, SG may consume reactive power. DC current in its field winding is high ; In that case, SG may supply reactive power. Active power is called true power. SG always supplies active power; so, you can understand why rotor angle is plus in case of Synchronous generator and it is minus in case of Synchronous motor.
As written above, if SG is running at high excitation than it may generate reactive power, i. SG will supply the reactive power to the system. Suppose the load is Induction Motor.
Why they have chosen first formula instead of second, try to analyze yourself on the basis of this article. From the Figure-3, you can easily understand, why active power is called true power and reactive power is called imaginary power. One diagram of SG is shown in Figure This Figure is also self-explanatory. So, perhaps you may think DC power of field winding is converted into reactive power.After you enable Flash, refresh this page and the presentation should play. Get the plugin now.
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Report on Comparison of Series and Shunt Compensation
Title: Batch Reactor. Latest Highest Rated. Where multiproduct plants are produced using the same processing equipment. Market forces Where products are seasonal e. Short product lifetime e. Operational problems Long reaction times when chemical reactions are slow.
SHUNT COMPENSATION ON EHV TRANSMISSION LINE
This surplus reactive power is present when lines are lightly loaded or there is a sudden drop in load due to a failure somewhere in the system. Other uses of a shunt reactor switch are to control excessive voltage rise Ferranti Effect created on long lines that are lightly loaded. SlideShare Explore Search You. Submit Search. Home Explore. Successfully reported this slideshow. We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads.
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Batch Reactor - PowerPoint PPT Presentation
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Zoya Baloch.Ram Uday Mandal B. Tech EEE 1 B. Series compensation is basically a powerful tool to improve the performance of EHV lines. It consists of capacitors connected in series with the line at suitable locations. Advantages of Series Compensation. Increase in transmission capacity The power transfer capacity of a line is given by. Improvement of System Stability.
For same amount of power transfer and same value of E and V, the in the case of series compensated line is less than that of uncompensated line. V P sin 2 X L XC sin 2 X L X C sin 1 XL A lower means better system stability Series compensation offers most economic solution for system stability as compared to other methods reducing generator, x-mer reactance, bundled conductors, increase no. Load Division between Parallel Circuits When a system is to be strengthen by the addition of a new line or when one of the existing circuit is to be adjusted for parallel operation in order to achieve maximum power transfer or minimize losses, series compensation can be used.
It is observed in Sweden that the cost of the series compensation in the kV system was entirely recovered due to decrease in losses in the kV system operating in parallel with the kV system.
Less installation Time. The installation time of the series capacitor is smaller 2 years approx. This reduces the risk factor.Shunt Reactors quietly ensure the power grid’s quality and efficiency
Hence used to hit the current thermal limit. The life of x-mission line and capacitor is generally years. Increase in fault current 2. Mal operation of distance relay- if the degree of compensation and location is not proper. High recovery voltage of lines- across the circuit breaker contacts and is harmful.
Location of Series Capacitor. The choice of the location of the series capacitor depends on many technical and economical consideration.This paper is to develop a program to determine the required shunt and series compensation on an EHV long transmission line and after which, conduct a power system analysis using a power system simulation package to evaluate the effect of compensations on the line with, To deter mine the shunt compensation at the load end to maintain the load voltage at a fixed percentage of the sending-end voltage, the maximum power transfer limit that may be transmitted under different conditions and to investigate the influence of various factors such as the line length, load power factor and the degree of series compensation on the maximum power transfer capability.
This paper will commence with an overview of the problems encountered with an EHV long transmission line.
This is followed up by a literature review that covers the research of useful background theories. The results from the performed studies and simulations will also be discussed in details. Finally, this paper will end with a conclusion of and recommendations for future work in this area of research. Authors are requested to submit articles directly to Online Manuscript Submission System of respective journal.
Vijaysimha 1P. Engineering College, Tirupati, India. Related article at PubmedScholar Google. The continuous increase of the voltage of transmission, line lengths and number of sub-conductors per bundle has emphasized the importance of the excessive line MVAR in EHV systems as well as the associated voltage and reactive controls.
During line- charging volt-amperes of a line which have exceeded the inductive vars consumed and operation at light loads, there is an undesirable voltage rises along the line. This voltage rise in turn demands a much higher insulation level, which poses a great problem for the capacitive generator.
Moreover, the problem is further deteriorated when the var is necessary to flow to its maximum, causes transmission losses and take up equipment rating. It has been proven that by using the series and shunt compensations are the best available methods because the transmission distance can be reduced artificially and hence, more power can be transferred.
The increase in the interconnections of Extra High Voltage EHV systems with the increased demand for electrical power has elevated concerns about system security and reliability. There are two methods to achieve the increase in the maximum power transfer limit of the line. The first method is to increase the transmission voltages. However, this will lead to an accumulating effect of cost increases in the generator.
The second method is by reducing the characteristic impedance of the line. The reduction of the characteristic impedance of the line can be achieved either by changing the line dimensions or by addition of capacitors in series with the line. The line dimensions cannot be changed widely and it only creates a small impact on the characteristic impedance value. Therefore, the addition of capacitors in series with the line, also known as the series compensation, is the best available method to reduce the characteristic impedance of the line, the percentage of series compensation and the optimum location of series compensation will be studied.
However, the overview on the types of series capacitors, which could result in improving the system stability. A lumped compensation can be placed at any locations marked 1 to 11 and a distributed compensation consists of splitting the compensation from a range of locations, for example, from location 4 to 8 or location 1 to The results of the computation are shown below.
The percentage or the degree of series compensation is used to analyse a transmission line with the required addition of series capacitor s.
It is defined as the fraction of Xc, which refers to the total capacitive reactance of series compensators and Xlwhich refers to the total inductive reactance of the line, as. The identification of the optimum location of the series compensation on the line is very important because compensation at this location has been proven that it could obtain more economical loading and results in minimum loss of revenue to the supply utility and minimum rise in receiving end voltage.
Due to the lack of sufficient generating capability in developing countries, the implementation of an under-frequency operation of the power system is accepted as a Strategy for maintaining the continuity of supply. This is due to the fact that the Subnormal frequency operation is associated with the reduced load demand, taking into Consideration of the frequencydependent characteristics of load.