May 2014

MODELING The basic concepts of transient stability are based on highly simplified models. Practical power systems consist of large numbers of generators, transmission circuits, and loads. For stability assessment, the power system is normally represented using a positive sequence model. The network is represented by a traditional positive sequence power flow model that defines the […]

Many factors affect the transient stability of a generator in a practical power system from which few are discussed here. THE POST-DISTURBANCE SYSTEM REACTANCE: The weaker the post-disturbance system, the lower Pmax will be. THE DURATION OF THE FAULT CLEARING TIME: The longer the fault is applied, the longer the rotor will be accelerated and the more

Transient stability is an important consideration that must be dealt with during the design of power systems. In the design process, time-domain simulations are conducted to assess the stability of the system under various conditions and when subjected to various disturbances. Since it is not practical to design a system to be stable under all

While it is true that power systems are designed to be transiently stable, and many of the methods described above may be used to achieve this goal, in actual practice, systems may be prone to instability. This is largely due to uncertainties related to assumptions made during the design process. These uncertainties result from a

For reliable service, a power system must remain intact and be capable of withstanding a wide variety of disturbances. Owing to economic and technical limitations, no power system can be stable for all possible disturbances or contingencies. In practice, power systems are designed and operated so as to be stable for a selected list of

NEED FOR CLASSIFICATION Power system stability is a single problem; however, it is impractical to deal with it as such. Instability of the power system can take different forms and is influenced by a wide range of factors. Analysis of stability problems, including identifying essential factors that contribute to instability and devising methods of improving

Power system stability is the ability of the system, for a given initial operating condition, to regain a normal state of equilibrium after being subjected to a disturbance. Stability is a condition of equilibrium between opposing forces; instability results when a disturbance leads to a sustained imbalance between the opposing forces. The power system is

• Oscillations are due to natural modes of the system and therefore cannot be eliminated. However, their damping and frequency can be modified. • As power systems evolve, the frequency and damping of existing modes change and new ones may emerge. • The source of “negative” damping is power system controls, primarily excitation system automatic

The following methods can be used to mitigate voltage stability problems. MUST-RUN GENERATION: Operate uneconomic generators to change power flows or provide voltage support during emergencies or when new lines or transformers are delayed. SERIES CAPACITORS: Use series capacitors to effectively shorten long lines, thus decreasing the net reactive loss. In addition, the line can

There are three basic reasons for grounding a power system which are personal safety, protective device operation, and noise control. All three of these reasons will be addressed. PERSONAL SAFETY: The most important reason for grounding a device on a power system is personal safety. The safety ground, as it is sometimes called, is provided