The author provides a comprehensive review of the basic charge simulation method and its various modified versions reported in the literature. Applications of the charge simulation method, alone as well as in combination with other methods, are considered. Different aspects of this method are critically examined and its potentials and limitations are identified. Possible areas of future research are outlined in order to improve the overall effectiveness of computer-aided analysis and design of high-voltage insulation devices by using the charge simulation method. >

A review of the charge simulation method and its applications

A modified charge simulation method for calculating the electric potential and field distribution along AC HV outdoor insulators is presented. The salient feature of this method is the significantly smaller number of unknowns and the corresponding reduction in computational complexity when compared to earlier charge simulation methods. Non-ceramic and ceramic suspension insulators of voltage ratings ranging from 115 to 500 kV, and non-ceramic line posts (115 and 230 kV) have been modeled under clean and dry surface conditions. Good agreement is obtained between the present calculations and measured data, calculated values using other numerical techniques and observations from service experience, which demonstrates the practical viability of the technique. >

Electric potential and field computation along AC HV insulators

Because of lower voltage levels and smaller power ratings, the R/X ratio of commutation impedance in industrial AC/DC distribution systems is usually higher than that in HVDC transmission systems. Considerable discrepancies may therefore occur in industrial AC/DC power flow results, especially the reactive power consumption of converters, if the commutation resistances of the converters are neglected. To describe the effects of commutation impedance on converter operations and to precisely relate the fundamental line current and DC output current of the converter, a detailed model of the bridge converter with commutation impedance for use of Newton-Raphson power flow studies in industrial AC/DC power systems is derived in this paper. A coal mine power system and a DC electrified transit railway system with regenerative braking function, a part of Taipei Rapid Transit Systems under planning, have been analyzed to show the improved accuracy and good convergence characteristics of the developed Newton-Raphson power flow formulation with the proposed converter model. >

A detailed R-L fed bridge converter model for power flow studies in industrial AC/DC power systems

Presents a comprehensive bibliographic survey pertaining to multi-stress-related degradation and aging of polymers with principal focus on their use as HV (high-voltage) insulators. The papers in the survey are arranged in the order of the year of publication, with most recent first and data as far back as 1948. However, the literature search for the 1980s was more intense than that for the earlier years. This is because most older literature is always referred to in the recent papers. The survey listings do not discriminate between simultaneously and sequentially applied stresses, or do they preclude papers in which only one externally applied stress induces other stress factors. The survey is intended to help the researchers in academia and industry, both in making an assessment of the current status of the particular research area(s) of their interest and in seeking directions in which to proceed. >

Aging of multistressed polymeric insulators

The medium-voltage dc (MVDC) distribution system is a new shipboard power distribution technology that has been extensively discussed and studied by many shipbuilding corporations and ship-owners in recent years. As different types of power converters and ac and dc power distributions simultaneously involved in the system, the system performance for different connections of generators to MVDC converters under varying steady-state operating conditions is essential and important in the design stage of the electrical power distribution system. This type of problem can be analyzed by performing power flow studies. This paper aims presenting a methodology for power flow studies in ship MVDC distribution systems for system planning purpose. A power flow model of the power converters in steady-state is derived to consider medium and low voltage characteristics of electric power system on this type of ship. An ac/dc power flow solution approach then is developed to incorporate ac-system and dc-system models and the ac/dc interface buses in the analysis for determining an appropriate connection of generators and MVDC converters and power converter setting values. Test results of two alternatives for the direct connection of generators to MVDC converters under varying steady-state operating conditions are presented and compared to determine the proper generator-power converter scheme.

Power Flow and Generator-Converter Schemes Studies in Ship MVDC Distribution Systems

A method is described for optimizing the field stress on HV insulators by modifying their profile, seeking a uniform distribution of the tangential field along the insulator surface. This results in an increase of the onset voltage for surface flashover and in a significant saving of the space of the HV installation. The optimization process was achieved by an algorithm developed for calculating the tangential field component and mathematical expressions of the profile to be corrected through an iterative procedure. The algorithm was based on a modified charge simulation technique to satisfy a better matching of the boundary conditions to the electrode and insulator surfaces involved in the HV installation. The algorithm is expanded to study the effect of contamination on the tangential field distribution. It is found that the higher the conductivity of the contamination layer, the higher is the field uniformity along the insulator surface.

Field Optimization of High-Voltage Insulators

Many present-day industrial power systems have combined ac/dc power distribution systems. A typical example is a coal mine power system, where ac is used for running the mining equipment and dc is used for track haulage, etc. Also, the topology of the dc network is constantly changing due to the movement of locomotives along the track. Methods are described that can be used to carry out load-flow and short-circuit analyses of such a system.

Analysis Techniques in AC/DC Power Systems

A mathematical-physical model of corona current pulses from voltage surges on HV lines is presented. Distributed representation of corona along infinitely long transmission lines is suggested. The surge corona current pulse flows through the transmission line as a series of successive generations of electron avalanches, which develop in the ionization zone around the HV conductor. The initiatory electrons for triggering the current pulse under a positive applied surge are those available in the atmosphere surrounding the HV conductor. The two corona current components, the image component due to the presence of charge carriers (electrons and ions), and the convection component due to the motion of charge carriers in the interelectrode spacing were calculated. The calculated corona current pulse and the charge flow voltage curve agreed reasonably with those measured experimentally for a coaxial transmission line.

E. Keith Stanek

Papers

Field Optimization of High-Voltage Insulators

Analysis Techniques in AC/DC Power Systems

Mathematical-Physical Model of Corona from Surges on High-Voltage Lines