Akira Isono

Power System Voltage Stability

Power system voltage stability is characterized as being capable of maintaining load voltage magnitudes within specified operating limits under steady state conditions. In this paper, the first order delay model of a load admittance change is introduced. Then, using this model, a set of linearized dynamic equations is derived and stability conditions are obtained. An earlier result in the literature is shown to agree with that in this paper. The stability conditions are tested and verified in a 2-load, 2- power source system and a 13-node, 4-power source system.

Load Flow Convergence in the Vicinity of a Voltage Stability Limit

Because load flow problems are expressed as sets of nonlinear simultaneous equations, they have no unique solutions. In this paper a region where a set of initial values converges to a stable load flow solution under specified conditions, is investigated theoretically when the Newton-Raphson method is applied to a set of nodal power equations expressed in either polar or rectangular coordinates. The results are tested in load flow calculations on a 28-node power system and the convergence characteristics for the two types of coordinates are compared.

Transient Behavior of Synchronous Machine with Shunt-Connected Thyristor Exciter Under System Faults

This paper covers an analytical method for transient behavior of a synchronous machine with shunt-connected thyristor exciter under power system faults such as line-to-line and three-phase short-circuit faults, considering performances of the thyristor converter and characteristics of the excitation control system.

Digital Simulation of Power Distribances and Protective Relaying

This paper describes simulation of power system disturbances and protective relaying performance by means of a digital computer. Line-to-line faults, faults involving ground and open conductors in a power system including both of single-and parallel double-circuit lines are dealt with, that is, voltage distribution under independent or simultaneous occurrence of such faults are calculated. The protective relaying can optionally be simulated by adding or modifying its own subprograms, and the following relayings are herewith detailed as examples: a) Combined phase and directional comparison carrier relaying for extra high voltage system. b) Out-of-step system-split relaying with distance relay of rectangular characteristics. c) Single-and three-phase reclosing systems.