Single-phase Network Research Articles

Single-phase bicomponent network by random crosslinking of hydroxyl-terminated polyisobutylene/polytetrahydrofuran mixtures

Random bicomponent networks were prepared from 50/50 wt % mixtures of hydroxyl-terminated polyisobutylene (HO-PIB-OH) and polytetrahydrofuran (HO-PTHF-OH) by the use of triphenylmethane triisocyanate (TTI) endlinking agent. Differential scanning calorimetry (DSC) and dynamic mechanical techniques were employed to study the networks. The glass transition temperature (Tg) of HO-PIB-OH was found to increase upon network formation. This Tg increment was used to estimate the molecular weight between crosslinking points (Mc). HO-PIB-OH/HO-PTHF-OH mixtures are immiscible and exhibit an upper critical solution temperature, however, the 50/50 network in a two-phase regime for the precursors gives a single Tg situated between the Tgs of the component networks. The single-phase network may be due to rapid nondiscriminatory endlinking and to an increase of the single-phase region of the phase diagram because of crosslinking.

GEORDNETE EPOXIDNETZWERKE AUS 4‐GLYCIDYLPHENYL‐4‐GLYCIDYL‐BENZOAT und 3‐ BZW. 4‐AMINOPHENYL‐4‐AMINOBENZOAT

AbstractThe introduction of mesogenic groups in main‐ and sidechains of epoxy thermosets results in an ordered multiphase network with cellular structure, if gelation occurs below the maximal cure temperature Tmax. Tmax is individual for a given combination of monomers. The multiphase network consists of relatively soft anisotropic cell nuclei and hard isotropic cell walls. If gelation occurs above Tmax single phase networks are obtained. The size of the cell nuclei strongly depends on the used monomers and varies up to two orders of magnitude. The multiphase structure was found to have no impact on the tensile elastic modulus.

Minimizing network harmonic voltage distortion with an active power line conditioner

Active power line conditioner (APLC) is a type of active filter that compensates for power system waveform distortion. The objective is to develop and illustrate a procedure for calculating the APLC injection current needed to minimize voltage harmonic distortion throughout a power network. The procedure is intended for use with APLC frequency domain correction in networks that are experiencing periodic harmonic distortion. The injection currents are determined using nonlinear optimization theory. The chief contribution lies in developing a simple procedure for finding the Fourier series of the optimum APLC injection current waveform. The procedure is intended to apply in any of the following situations: (1) one single-phase APLC in a single-phase network; (2) one single-phase APLC in a three-phase network; or (3) one three-phase APLC in a balanced three-phase network.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

System Analysis and Application Concerning with Single Phase Spot Network (SNW)

Household use of microcomputer-based equipment now requires that the power supply to dwellings be highly reliable without momentary failures. Three-phase power supply networks have previously been used to distribute single-phase loads to dwellings. Single-phase networks have a better cost performance compared with the three-phase network system. However, due to the complicated current analysis in the case of faults and to the difficulty in developing relays based on the analytical results, single-phase networks have not yet been put into practical use. We have now succeeded in developing a single-phase network using the following five processes: (1) System analysis (2) Verification using a simulated circuit (3) Determination of the relay characteristics based on the analytical results (4) Development of a static single-phase network relay to satisfy with the complicated voltage-current relationship (5) Actual field test This system has been operating since 1983.

System analysis and application concerning with single phase spot network (SNW)

Household use of microcomputer-based equipment now requires that the power supply to dwellings be highly reliable without momentary failures. Three-phase power supply networks have previously been used to distribute single-phase loads to dwellings. Single-phase networks have a better cost performance compared with the three-phase network system. However, due to the complicated current analysis in the case of faults and to the difficulty in developing relays based on the analytical results, single-phase networks have not yet been put into practical use. We have now succeeded in developing a single-phase network using the following five processes: (1) System analysis (2) Verification using a simulated circuit (3) Determination of the relay characteristics based on the analytical results (4) Development of a static single-phase network relay to satisfy with the complicated voltage-current relationship (5) Actual field test This system has been operating since 1983.

Equivalent Circuits for Cylindrical-Rotor, Reluctance, and Salient-Rotor Synchronous Machines

This paper presents a unified approach to the steady-state analysis of polyphase synchr-onous machines of three major types: cylindrical rotor, reluctance, and salient rotor. The major magnetic parameters of the machines are derived. Single-phaseequivalentcircuits are developed for each of the machine types. These equivalent circuits may be incorporated directly into the single-phase network representing a power system.

Transient analysis of three-phase power systems, part II

The difficulties encountered with symmetrical components, as discussed in Part I, B, are eliminated when Clarke components are used. It is possible to investigate transient phenomena in three-phase systems by studying single-phase networks with the transient analyzer.The basic relationships between the three-phase problem and its equivalent representation in Clarke components are established in the first section (C) of this paper. The last section (D) of this study contains the component-network connections and the switching arrangements which are representative of the more frequent types of disturbances in three-phase systems.

Two-phase co-ordinates of a four-phase network

SUBSTITUTION of variables (voltage, current, impedance, and so forth) in order to simplify solution of problems on polyphase networks is a well-established practice. A polyphase network may be regarded as several single-phase networks which are coupled to one another in many places and all of which contain power sources. Simplification of network problems results from the replacement of the original phase networks by an equal number of single-phase substitute networks which are not coupled to one another or are coupled in fewer places or in a simpler manner than the phase networks, and which, preferably, have fewer power sources. In these substitute networks, the substitute currents and voltages exist.

Two-Phase Co-ordinates or a Four-Phase Network

SUBSTITUTION of variables (voltage, current, impedance, and so forth) in order to simplify solution of problems on polyphase networks is a well-established practice. A polyphase network may be regarded as several single-phase networks which are coupled to one another in many places and all of which contain power sources. Simplification of network problems results from the replacement of the original phase networks by an equal number of single-phase substitute networks which are not coupled to one another or are coupled in fewer places or in a simpler manner than the phase networks, and which, preferably, have fewer power sources. In these substitute networks, the substitute currents and voltages exist.

Equivalent single-phase networks for calculating short-circuit currents due to grounds on three-phase star grounded systems

H. M. Trueblood: The question of the degree of precision worth while in estimating short-circuit currents in power networks presents itself as of immediate importance as soon as consideration of the problem of the induetive effects of these currents in exposed communication circuits is undertaken; for it is necessary only to glance over a single-line diagram of a large modern power system to realize that an exact calculation of the distribution of residual current due to an arbitrarily located fault to ground will be a lengthy, difficult and expensive proceeding.

Equivalent single-phase networks for calculating short-circuit currents due to grounds on three-phase star grounded systems

This paper presents a method for calculating the steady state value of the short-circuit current in a fault to ground on a power system operated with grounded neutral, and the distribution of this current throughout the system. Constant impedances and electromotive forces in the system, and electrically short lines, are assumed, and line capacitance is neglected. If, at the time the fault to ground occurs, the distribution of the load current in the system is known, the total current in any portion of the system under the short circuit condition may be calculated by means of this method. By “total current” is meant here the sum of that part of the fault current which appears in the branch considered, and the normal current in the branch due to the loads. The latter current, of course, does not appear in the fault. Formulas and equivalent circuits for the usual three-phase transformer and generator connections used in practise, are given. The use of such circuits permits the calculation of the fault current and its distribution in the power system from an equivalent single-phase network. Since currents in a three-phase network under balanced conditions may also be calculated from a single-phase network, it is accordingly possible to calculate, entirely on a single-phase two-wire basis, the total current in any branch of a star grounded network for a ground on any phase. The setting up of equivalent 2-wire single-phase networks similar to those for the three-phase case is not generally possible where the number of phases exceeds three. The value of the method lies in its enabling one to calculate on a single-phase two-wire basis the short circuit current (steady state) due to a ground on a three-phase grounded neutral system, as regards both magnitude and distribution and taking into account all system loads. In the usual approximate method of making short-circuit calculations, a single-phase-to-neutral network is substituted for the actual network. While this method involves less labor than that proposed in the paper, the results obtained by it are inexact, the effect of non-grounded loads being usually ignored. The method of the paper involves much less work than that required by three-phase calculations giving equal accuracy. An illustrative example is given.

Equivalent Single-Phase Networks for Calculating Short-Circuit Currents Due to Grounds on Three-Phase Star Grounded Systems

This paper presents a method for calculating the steady state value of the short-circuit current in a fault to ground on a power system operated with grounded neutral, and the distribution of this current throughout the system. Constant impedances and electromotive forces in the system, and electrically short lines, are assumed, and line capacitance is neglected. If, at the time the fault to ground occurs, the distribution of the load current in the system is known, the total current in any portion of the system under the short circuit condition may be calculated by means of this method. By ``total current'' is meant here the sum of that part of the fault current which appears in the branch considered, and the normal current in the branch due to the loads. The latter current, of course, does not appear in the fault. Formulas and equivalent circuits for the usual three-phase transformer and generator connections used in practise, are given. The use of such circuits permits the calculation of the fault current and its distribution in the power system from an equivalent single-phase network. Since currents in a three-phase network under balanced conditions may also be calculated from a single-phase network, it is accordingly possible to calculate, entirely on a single-phase two-wire basis, the total current in any branch of a star grounded network for a ground on any phase.