On the Condition required for Discharge and Dielectric Breakdown

The condition required for the electric breakdown of gas, liquid or solid against impulse voltage is tentatively assumed. The calculated value by the equation which is derived from this condition is compared with the experimental data about the breakdown of air, heptan and chloroprene, and the validity of this theory is investigated

Reducing Effect in Footing Resistance Against Heavy Impulse Current (II) : Profitable Use and Promotion of Streamer in the Soil

Distortion and promotion of the electric field intensity in the vicinity of earth electrode strengthen the reducing effect of footing resistance against heavy impulse current ; and by a little mixing material in concrete, the earth resistance of concrete electrode that imitates the concrete block of tower foot is reduced

Equivalent Circuit of a Power System by Mesh Method

The simple equivalence of a power system is obtained in the form of a Lagrangian tree, through the transformation of the circuit matrix where mesh currents are variables and some nodes or elements (load, etc., ) of the system are eliminated, then the equivalence is extremely simplified from the view point of network topology. The application of this equivalence to the calculation of system power flow, and transmission loss is studied

Voltage-current Characteristics of MHD Boundary Layer Plasmas

This paper deals with a two-dimensional time-dependent numerical simulation of the growth of discharges in MHD generator boundary layers. The calculated voltage-urrent characteristics in a boundary layer have positive resistance characteristics for small currents and negative ones for large currents. The characteristics agree with those observed in an anodic layer of actual ETL-Mark 7 B-channel experiments for various temperatures of electrodes. The current flows almost uniformly into the electrode surface (diffuse or fine constricted mode) when the current density is in the region of positive V-I characteristics. It concentrates in a large diameter (large constricted mode) in the region of negative ones. The critical current for this transition of discharge mode is about 0.5 A/㎠ for cold electrodes. This value becomes larger for hot electrodes

Assessment of Transient Stability via Stochastic Approach and its Application to Optimum Load Dispatching Problem in Power Systems

This paper describes a method of transient stability evaluation via the stochastic approach developed for the application to security control, and the method is applied to a model system. A comparison was made between the results obtained by the method here proposed and by the pattern recognition method proposed recently for the same purpose. The superiority of the former was ascertained. Furthermore, as an example of a practical application of this method, it was applied to the optimum load dispatching problem, considering not only economy but also transient stability

Calculating Method of Dynamic Stability in a Multi-machine System allowing for Margin

First, the equivalent circuit of a power system transformed into the form of Lagrangian tree is applied to obtain the basic equations required for criterion of system stability. On the next step, the characteristic equation can be obtained by transformation of the matrices which consist of the coefficients of basic equations. Furthermore, a new concept about the margin of system stability is proposed, and the assessment of system stability is carried out by obtainning the root-loci of a characteristic equation

Relative Dymamic Stability of a One-machine System : Frequency-response Approach

A one-machine system under small perturbations was represented in a closed-loop block diagram and its open-loop transfer function was calculated. The concept of relative stability was developed by means of a generalized Nyquist's criterion. Moreover, the indicial response of terminal voltage according to the unit step change of excitation voltage was calculated by means of a Fourier series approximation and its integral squared error was proposed as a measure of relative stability. A stability analysis using this measure was developed for various values of power output. Also, the effects of the regulator gain were analyzed using this measure

The Leader Development and its Mechanism in Air under Impulse Voltage

In this paper, the breakdown phenomena in air for both short and long gaps of 3～20 cm length were observed by means of the voltage, current, light pulse measurement and the still photograph observation (accompanied with chopped voltage). Also, the role played by primary and secondary streamers for leader inception and its development are studied. As a result, several delayed streamers which were named here, and which were made of sets of primary and secondary streamers, were observed ; and only when the current pulse of a delayed streamer continues without interruption, the leader occurred

Transient Stability Equivalents Based on Lyapunov Function

Owing to the increasing size and complexity in power systems, the study of the stability equivalent is receiving a great deal of attention. This paper describes a systematic method for the recognition of coherent machines by means of the Lyapunov function which is used for the transient stability analysis. A group of generators, whose partial Lyapunov function has a small value compared with that for the whole system, is aggregated into one equivalent generator. This method does not require a long time simulation of the entire system. The parameters of the simplified system are also determined by using the Lyapunov function. The method is applied to 10-machine and 50-machine sample systems and the results are shown

The Pre-Breakdown Phenomena in Atmospheric Air Gaps under the Impulse Voltage

Pre-breakdown phenomena against impulse voltage are observed, where rod-toplane electrodes are used, and the gap length is 3～20 cm. Streamers are observed by an oscillograph, a still camera acompanied with chopped voltage and a photomultiplier. As the result of this investigation, for a positive and a negative polarity, the number of charged particles, the field intensities of primary and secondary streamers were obtained experimentally. Furthermore, the difference between a positive and a negative polarity was considered