摘要:

Travelling waves on e.h.v. transmission lines often cause considerable distortion of relaying measurands, and, in this paper, modern methods of digital simulation are used to examine the performance of crosspolarised mho relays under more realistic conditions than have hitherto been possible using conventional conjunctive test methods. It is shown that travelling-wave effects can cause a significant delay in the fault-detection process and that, in this respect, the bandwidth of the voltage transformers (v.t.s) is an important influencing factor. The extensively used block-average comparator arrangement is examined in detail, and it is shown that a recently developed processing technique can provide faster fault-clearance times when coupled with a small degree of overreach. The paper concludes with a brief consideration of the performance of the block-average comparator mho relay in a long-line application.

DOI:10.1049/piee.1977.0136

出版商:IEE    

年代:1977

数据来源: IET

摘要:

Functional iteration has been very widely used for the solution of nonlinear system equations. Although sufficient conditions have been given for the iteration sequence to converge, a method to determine the precise number of iterations that are required is not to be found in the literature. The availability of such information would enhance, considerably, the utility of the method. Using the concept of ‘stop-growing terms’, an algorithm is now proposed which enables one to determine precisely the number of iterations that are required for the solution to converge to a predetermined degree of approximation.

DOI:10.1049/piee.1977.0139

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The paper deals with the dynamic performance of permanent-magnet stepping motors as affected by various kinds of practical load torques. The constant component of load torque, including coulomb friction, results in stable and unstable equilibrium regions, while the viscous torque component is analogous to the damping-factor increase. The technique of generating phase trajectories for a 2-phase permanent-magnet motor, using a digital-computer program, can take into account the actual static torque/angle characteristic of the motor. Pull-in and pull-out stepping rates, obtained from the phase planes, change significantly on account of the variation in motor damping. The technique can also be applied to other types of stepping motors.

DOI:10.1049/piee.1977.0140

出版商:IEE    

年代:1977

数据来源: IET

摘要:

An electronic switching scheme is outlined that can scanNooutputs in step acrossNiinputs (Ni≥Nomuch more economically than the conventionalNi.Noswitch matrix. It thus reduces the relative advantage of a mechanical solution reported previously. Applications include instrumentation, scanning beam-formers, and possible spatiallymultiplexed slip rings.

DOI:10.1049/piee.1977.0141

出版商:IEE    

年代:1977

数据来源: IET

摘要:

The penetration of leakage flux into a laminated machine or transformer core is governed by the currents induced in the steel, and poses an anisotropic and 3-dimensional field problem which is also severely nonlinear. It is shown that the differential equations can be formulated in terms of an electric vector potentialT, and magnetic scalar potential Ω, and that the solution can be expressed in the form of three different characteristic modes, two associated with the core surfaces and the third describing the flux penetration into the interior. This form of solution provides both a qualitative and quantitative picture of the 3-dimensional flux paths, and eddy current loss distribution, and also a practicable means of allowing for saturation. The result can be expressed in the form of a simple network model that is well suited to numerical solution by computer.

DOI:10.1049/piee.1977.0142

出版商:IEE    

年代:1977

数据来源: IET