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For isolated power systems, an efficient and effective ancillary services market is one of the most important tools to ensure the system security and service quality. It is recognized that pumped storage units can play a unique role in the operation of isolated power systems. As part of the introduction of the ancillary services for Taiwan, a study was performed to identify the role and value of pumped storage units in the fast-response reserve (FRR). This paper analyzes the actual dispatching schedules of pumped storage units in the Taiwan Power System (TPS) to provide FRR when system was operated under seriously insufficient conditions for the year 2004. The results are used to quantify the value of pumped storage units in the ancillary services. Since the dispatching schedules of pumped storage units determined the cost of FRR in the TPS, the actual operating experience of pumped storage units studied in this paper can be used to evaluate the impact on the system security and to further define the role of pumped storage units in the ancillary services market. [ABSTRACT FROM AUTHOR]

This paper presents the protective relay settings of tie line tripping and design of load-shedding scheme for an integrated steelmaking industrial power system to ensure system stability after a severe fault contingency on an external utility power network. The transient stability analysis of the industrial power system with the equivalent external Taipower system has been executed for an actual fault contingency in 2005. The mathematical models of 13 cogeneration units in the plant and several large generators of a nearby Taipower thermal plant are included in the computer simulation to solve the system transient response for the fault contingency to verify the accuracy of the models used. To prevent tripping of critical loads due to an external fault contingency, the undervoltage and under/overfrequency relays with proper settings are applied for the tripping of external and internal tie lines. To restore system stability of the industrial power system for the islanding operation after tie line tripping, load shedding is designed to disconnect a proper amount of noncritical loads by considering the governor response and protective constraints of cogeneration units. According to the transient stability analysis of the industrial power system with the proposed protective relay settings and load-shedding scheme, it is found that the voltage sag and oscillation problem caused by fault contingency in the external Taipower system can be mitigated if the tie line tripping is executed in time to prevent the shutdown of critical loads and tripping of cogeneration units. [ABSTRACT FROM AUTHOR]

The subject of this paper is to construct a current-transformer (CT) model based on the Jiles-Atherton (J-A) theory of ferromagnetic hysteresis using transient analysis of control systems (TACS) functions within the Electromagnetic Transients Program (EMTP) in a closed-loop manner. The J-A theory of ferromagnetic hysteresis is presented by the nonlinear first-order ordinary differential equations and inclusive of five parameters that can be found by measurements of hysteresis characteristic. We can use TACS functions within EMTP to describe the J-A theory of ferromagnetic hysteresis. The powerful advantage of this way is the interaction between the electrical network and TACS in EMTP. Compared with the CT model based on the type 96 nonlinear hysteresis inductor, the simulated result of the CT model based on the J-A theory of ferromagnetic hysteresis is almost the same in steady-state situations, but apparently different in a fault transient situation. The analysis and simulation of the actual measured fault profiles in the Taiwan power system is an example of the validation of this proposed model. Therefore, this proposed CT model based on the J-A theory of ferromagnetic hysteresis has the analysis capability of the transient response. The flexibility of TACS makes the simulation of any other situation easier and is another advantage. [ABSTRACT FROM AUTHOR]

This paper describes the application of proposed under-frequency load shedding scheme with dynamic D-factors, i.e., load frequency and voltage dependent coefficients, of various dynamic load models to Taiwan power system. The load models adopted are 1) a single-motor dynamic model, 2) a two motor (one small and one large) dynamic model, and 3) a composite (static and dynamic) model. First, the dynamic D -factor values of these load models are determined by the actual analytical approach employed in Taiwan power system. Then, a single-machine model representing a multi-machine power system is utilized for validating the proposed load shedding scheme with derived dynamic D-factor values. Finally, time simulation results of load shedding applied to various load models are compared with field measurement data, which are obtained from Taiwan power system in the case of three-phase short circuit fault, to evaluate the effects of different load models on the proposed load shedding scheme, based on the restoration of system frequency. [ABSTRACT FROM AUTHOR]