Posts Tagged ‘power system’

Usefulness and shortcomings of the power system contingencies

August 14th, 2013 | Make a comment | Posted in Power quality
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Results and Use

Usefulness and shortcomings of the power system contingencies 1

CA results of each element of the power system being studied are evaluated against the safe operation and stability limit for that element.

All the violations are recorded in the form of a list and ranked as per the severity of the situation with the highly overloaded elements on the top of the list.

The major and immediate attention requiring problems are usually covered up in the first 50 violations of the list.

For some elements there can be two limits, one short term and the other long term thermal limit. An example is the effect of the ambient temperature and the overload duration on the operating limits of the transformer and transmission lines within the safe range.

Depending on the operating state and the configuration of the power system whether the load being light, medium or heavy, stability limits can also be present for lines and interconnections. For CA to check these limits it is required by the user to select these options.


Power System contingencies

August 9th, 2013 | Make a comment | Posted in Power quality
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The security of a power system is very important to be evaluated to make sure whether the system will continue working in case one or more element stops to function properly.

Power system contingencies 1

Contingency analysis (CA) is one such evaluating program which separates the Energy Management System (EMS) from a SCADA system which is a level low in complexity. It checks the system for overloads and other problems arising from a contingency.

Contingency can be defined as the non-functionality in the power system of a device such as generator, transformer, transmission line and more or the change of the device state which may include the possibility in a transformer substation of an unplanned opened circuit breaker.

The purpose of the contingency plan is to check the change in the functioning of the device that will occur after the fault element is removed.

There are three levels of problems in case a contingency occurs:


Artificial Neural Network Based Power System Restoration

May 7th, 2013 | Make a comment | Posted in Electrical distribution
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Artificial Neural Network Based Power System Restoration 1

The importance of electricity in the present era cannot be falsified. The need is, thus, that we take necessary measures to ensure not only the safety of the power system equipment but also that they are receiving a continuous supply of electricity. During blackouts the continuous supply is interrupted leaving a strong influence on commerce, industry and our everyday lives requiring restoration within the shortest time interval.

Electricity utility companies have therefore, taken vital steps so as to decrease the social and economic cost caused by these power system blackouts. These measures include step-wise guidelines and operating procedures required to reinstate the power supply and serve as an aid to the operator. The chance of success for this system decreases because it is designed on basis of suppositions.

The emphasis in this post is on the factors that limit the functionality of PSR (Power System Restoration) techniques used currently and how these can be improved by applying the technology of ANN.


Power System Protection

March 22nd, 2013 | Make a comment | Posted in Electrical distribution
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Power System Protection 1

Today, most of the Power Distribution network is either radial or interconnected in nature. The main reason for the distribution network being radial is cost effectiveness & easiness in maintenance. Most of the devices used in the radial distribution network include fuses, auto reclosers & over-under current relays.

The main purpose of these devices is to keep the power distribution network as simple as possible. Reclosers are normally used for maintenance of lines or for clearance of faults. When a fault occurs, reclosers operate in order to isolate the system under fault so that fault current has a path to clear itself without affecting the rest of the system. On the other hand fuses are used for prevention of faults from transient currents. Fuses operate on the events when auto reclosers fail to clear the faults. In case of any fault fuse, nearest to the fault will open to clear the fault. However, if the first fuse fails the immediate fuse after the first one opens to clear the fault. All of these devices work in unison to protect & isolate distribution network under faults.

Goals of Protection

The main reason for designing a protected power system is to isolate the faults & the components affected as a result of the fault. The equation is to protect the remaining operating network besides clearing the fault. This post will discuss the components as well as the techniques which are used for their protection.


Power System Operation and Control

February 8th, 2013 | 1 Comment | Posted in Power quality
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In order to keep any power system in steady state the flow of active and reactive power must be checked. The objective of the control strategy is to generate and distribute power in an interconnected system as economically and reliably as possible while maintaining the frequency and voltage within permissible limits.

Changes in real power mainly affect the system frequency. Reactive Power however, is immune to changes in frequency and mainly depends on voltage changes. Thus real and reactive power is controlled separately. The Load Frequency Loop (LFC) controls the real power and frequency and the automatic voltage regulator (AVR) controls the reactive power and voltage magnitude.


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