Top PDF Transient Stability of the Power System with the Exact Long Transmission Line Model

Abstract: Problem statement: The exact long transmission line model consists of the lump of the series resistance, reactance and shunt capacitance. With the consideration the actual long transmission line model, it causes in the difficulty of deriving the mathematical model. Approach: This study investigates the transient stability of power system with consideration the exact long transmission line model. The concept of two-port network is applied in this study. The generator, transformer and short transmission line are represented by two-port networks. With the combination principles of the series and shunt connection, the mathematical model is achieved in a much simpler way. The proposed method is tested on the sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without the resistance is obviously higher than that of with the resistance whereas the second swing of the faulted system without the resistance is slightly less than that of with the resistance. The critical clearing time of the system with the resistance is better than that of with resistance. Conclusion: It was found from the simulation results that the resistance of the line provides the improvement of the first swing but not for the second swing. It was found from this study that for practical long line, the resistance is very import parameters to determine the critical clearing time of the single machine infinite system whereas shunt capacitance insignificantly affects on the critical clearing time of the single machine infinite bus system.

Abstract— In this paper, field measurements carried out in a suburban SFN network with two synchronized transmitters are reported. It is found that the radio signal coverage of the distributed transmission scheme is distinctly improved when compared to a single transmitter system. The path loss gain and improvement associated to the SFN scheme are obtained as well as the multipath channel parameters including the mean and RMS delay spread. A tapped delay line is used to model the average power delay profile (PDP) in the distributed transmission cases and shows rather different features than the single transmission case.

The accuracy of using static (nonlinear) load models with suitably identified parameters for transient stability analysis has been examined in [9]. Here, numerical studies have been conducted using on-line measurement data for modeling real power behaviors during disturbances and hence were deemed adequate for transient stability analysis. In [10], the authors have carried out Transient stability analysis in different cases such as peak and off-peak loads, connection and disconnection of busbar, with and without current limit reactor (CLR). In this case, the transient stability in peak load condition was more stable than that in off-peak load condition; the transient stability with bus-bar disconnected was more stable than that with bus-bar connected; the transient stability with CLR was more stable than that without CLR. Transient stability analysis in terms of machines rotor angle, electrical power, machines speed and terminal voltage has been done for Sarawak grid system using power system simulation for engineers in [11]. A power system analysis toolbox (PSAT) was used to study transient stability analysis for the IEEE 14-bus system with wind connected generator in [12]. Systematic investigations of transient stability analysis have been conducted by the combination of step-by-step integration and direct methods in [13]. In this case, more time was required to calculate potential and kinetic energies of all machines before and after the faults. Carlo Cecati and Hamed Latafat [14] have

To study the transient stability phenomenon a simplest power system is analyzed by the utilization of SimPower System toolbox presented in the MATLAB/Simulink software environment. Fig.1 represents single line diagram of SMIB system which comprises of a transmission line connecting an AC power source at the sending end and a receiving side connected to a RL load. This arrangement is first studied without STATCOM using a generating source with 230 kV voltage which simulates a synchronous generator of 500MVA capacity with terminal voltage 11kV, and its associated step up transformer with 500MVA, 11/230kV rating. The real power flow and reactive power flow in this configuration and the associated sending end and receiving end parameters have been observed. In Simulink Power system blocks, the reactive and active power blocks are available for measuring the power flow both at the sending end and the receiving end.

Including monitoring and control equipment along with transformer switch gear protection. Transmission and distribution lines are designed for transmission of power from generating station to end user only. However, transmission lines, 66Kv and above are presently employed for audio communication between the operators at two ends of the transmission lines viz. Substation operators, carrier protection schemes and telemetry signal. These signals are modulated before sending on transmission lines in the frequency range of 100 KHz – 500 KHz for overhead transmission lines and 10 KHz – 100 KHz for underground cables. Such conventional modulated communication system over power line functions satisfactorily during normal operation of power system. However, during transient conditions when a fault occurs on the transmission lines, power frequency harmonics up to 100 KHz frequency are generated and distributed to the communication system [5]. It is, therefore required same methodology that the communication shall not be disturbed during transient and emergencies for the safe operation of the power system. Since the power wiring system was originally intended for transmission of AC power, the power wire circuits have only a limited ability to carry higher frequencies.

Abstract: Problem statement: The Static Var Compensator (SVC) have been widely investigated its effect on transient stability of Single Machine Infinite Bus (SMIB) system. The exact medium transmission line model in power system consists of the series resistance series reactance and shunt capacitance. It is not easy task to obtain the mathematical model of the SVC with the exact medium transmission line model for investigating transient stability performance. Approach: This study applied the concept of the two-port network to simplify the mathematical model of the power system. The full capacity of the SVC on transient stability improvement of the SMIB with the medium transmission line was then investigated. The proposed method was tested on sample system and compared on various cases. Results: The first swing of rotor angle curve of the faulted system without resistance was obviously higher than that of with resistance whereas the second swing of the faulted system without resistance was slightly less than that of with resistance. The system with a SVC could improve transient stability of power system. Conclusion: The SVC and resistance of the line can improve first swing of rotor angle. The resistance of the line provides negative effect on second swing of rotor angle. The simulation results indicate that for practical medium line, the resistance is very import parameters for evaluating transient stability of power system.

techniques available in PSAT are the Euler and trapezoidal rule techniques. In this work, the trapezoidal technique is used considering the fact that it is widely used for solving electro-mechanical differential algebraic equations [12] . The type of contingency considered is the three-phase balanced faults created at various locations in the system at any one time. When a three-phase fault occur at any line in the system, a breaker will operate and the respective line will be disconnected at the Fault Clearing Time (FCT) which is set by a user. The FCT is set randomly by considering whether the system is stable or unstable after a fault is cleared. According to ref. [13] , if the relative rotor angles with respect to the slack generator remain stable after a fault is cleared, it implies that FCT<CCT and the power system is said to be stable but if the relative angles go out of step after a fault is cleared, it means FCT>CCT and the system is unstable.

FACTS controllers are capable of controlling the network condition in a very fast manner and this unique feature of FACTS can be exploited to improve the stability of a power system (Panda, 2010; Kumkratug, 2010). The detailed explanations about the FACTS controllers are well documented in the literature. Static Synchronous Series Compensator (SSSC) is one of the important members of FACTS family which can be installed in series in the transmission lines for applications such as increased power transfer, improved transient and small disturbance stability of power systems (Abido, 2009; Shakarami and Kazemi, 2010). SSSC is very effective in controlling power flow in a transmission line with the capability to change its reactance characteristic from capacitive to inductive.

system regains its normal state after transients die out is due to the action of PSS and AVR. If STATCOM is not available, PSS fail to operate, this leads to instability and may also cause the generator to damage if proper action is not taken. In power stations, the relays will identify such situations and will trip the system from supplying power.This leads to load shedding and severe inconvenience to the customers. It can be observed that surge currents can be bypassed to STATCOM which helps in maintaining nearly constant voltage and current. Working of STATCOM depends on the impedance of the line, capacitor ratings, voltage that has to compensate ,MVA rating of STATCOM transformer and reactive power of the system. Generator stator current has controlled with STATCOM and surge currents are mitigated. Different facts devices like SSSC, TCSR Can also be used for the power system stability, FUZZY LOGIC techniques can be used for controlling these FACTS devices for fast operation.

The evaluation of Critical Clearing Time (CCT) of power system is one of the most important research areas for power engineers because it indicates the robustness of the faulted power system. The rotor angle of the synchronous generator determines the stability of the power system. Although the stability of the synchronous machine is used to represent the stability of the power system, all of the power system components such as transmission line and transformer affect the stability of the power system.

It was found from the simulation results that the resistance of the line provides the improvement of the first swing but not for the second swing. It was found from this study that for practical long line, the resistance is very import parameters to determine the critical clearing time of the single machine infinite system whereas shunt capacitance would not affect on critical clearing time of single machine infinite bus system. It was also found in this study that the TCSC can enhance transient stability of power system.

Abstract: Problem statement: The enhancement of transient stability of the power system is one of the most challenging research areas in power engineer. Approach: This study presents the method to enhance transient stability of power system by Unified Power Flow Controller (UPFC). The mathematical model of power system equipped with a UPFC is systematically derived. The parameters of UPFC are modeled into power flow equation and thus it is used to determine control strategy. The swing curves of the three phase faulted power system without and with a UPFC are tested and compared in various cases. Results: The swing curve of system without a UPFC gets increases monotonically and thus the system can be considered as unstable whereas the swing curves of system with a UPFC can return to stable equilibrium point. Conclusion: From the simulation results, the UPFC can enhance transient stability of power system.

operation. More specifically keep voltages close to nominal values, reduce line currents and hence network losses. Reactive power compensation also contributes to the voltage stability margin enhancement. Compensation is provided by either capacitors installed in series with transmission lines or shunt elements connected to a particular load bus. In this study shunt compensation technique is adopted to improve the voltage stability margin.

The cultivating, through different social policies, especially through the ideologization of the values , of the contempt for the real, productive work represents a major problem. Only one country in the world set the objective – within the constitution – to not spend more

Here 1013.25 is the pressure at sea level in mil/bar, z is the altitude in meters. Knowing p 0 ( z ) and the relation for resistance to flow, the pressure variation on the human body have been computed by the following method. We have

The diagram in Figure 1 shows the basic requirements for a material-related module in a CAPCAST system. The system user (manufacturer or his employees) introduces to the system the customer's technical requirements concerning the material, and also gives the current price/cost of materials and processing. Entering current prices is necessary to keep the calculations up- dated all the time against the ongoing market price fluctuations. However, this operation does not have to be performed each time when the type of material is determined; it is enough to provide current prices in the system keeping pace with the rate of changes in the market and introducing these changes with the same fre- quency with which the fluctuations occur in the market (e.g. once a week, once a month, etc.). The user will have at his disposal an intuitive and easy to use interface, which should correspond in its

The metaphysicians of chance point to the probabilistic nature of scien- tiic laws. Such probabilistic laws assert some dependencies and enable us to predict (with a given probability) the future of aggregates or collectives, but not the future of their individual parts. We also meet this kind of unpre- dictability in the case of human behaviour, individual as well as social. All these data give us evidence that our universe has not been created according to a very detailed and precise plan encompassing all substances and all of their properties. Protons, electrons, and genes, but also species, kinds, and particular human beings, are not part of a divine plan and creative volition (Bartholomew 1984, p. 145). How could it be that God brings about the existence of beings which are purposeless, unpredictable and, as such, not determined by his creative volition? If our non-deterministic universe has a Creator, He does not control every substance and every property, de facto, he is not the Creator of all contingent entities in our world. Thus, divine action consists in the creation of the universe in its initial stage, and the world is such that God need neither act continuously upon that world nor intervene from time to time in order to achieve His aims. God created the world in such a way that His providence does not have to control absolutely every contingent substance at every moment of its existence in order to realize all that divine will wills to be realized.

In the meanwhile, Fig. 8 shows that current rating is greatly influenced by wind direction, resulting in the changes of conductor temperature. However, this dependence disappears as the wind velocity is reduced to zero. During the situations in which the wind direction changes rapidly, the conductor temperature can be expected to reflect these changes. The actual response of the conductor temperature will be postponed from the variations in the weather conditions due to the thermal capacitance of the conductor. In Malaysia, there are 2 majors of vibration damage on the conductor. They are Aeolian vibration and sub-conductor oscillation, which cause by wind parameter (JMM, 1958).

The material used in this study was C120U steel. Chemical composition of this steel is presented in Table 1. Specimens as cuboids about dimensions 7,5 x 30 x 30 mm were conventional hardened (temperature austenitization – 770 o C, quenching in oil) and tempered (in temperature 250 o C). Temperatures hardening and tempering were chosen on the basis EN ISO 4957:1999 norms to obtain a structure with a relatively high toughness. Remelting surface was carried out using gas tungsten arc welding method. The surface of the samples were remelted by means of

The Near End cross-talk predictions (Branin model and FDTD method) are compared to the experimental results [2] in figure 9 and figure 10. The signal rise time is T-rise = 20 ns, is slow compared to return-propagation-time T~2.(3.5ns x 2m) = 14ns. Therefore, the predicted Near-end X-talk on victim line (figure 9) correctly reproduces the actual source signal shape. The multiple reflections on measured waveform, at end of queue, have a single step duration of T~14ns. The same oscillations can be identified on predicted waveform, less evident because the parasitic inductance of termination leads has not been included in the model.