摘要:

A novel construction for a flexible, compressed SF6insulated e.h.v. power cable is proposed. The main feature of the design is the use of a trefoil spacer held by three subconductors. This arrangement has a good stress distribution, which is independent of small gaps between the spacer and conductors; it also offers a practical way of manufacturing the cable without passing spacers over the conductor or moulding them in place. Experimental results show the effect of different gas pressures and sheath diameters on the impulse flashover strength of the cable. It is necessary to assemble and test the cable under very clean conditions, but even if this is done breakdown occasionally occurs at a low voltage. This phenomenon is discussed, but a satisfactory and comprehensive explanation is not yet available. Development of the cable is in an early stage, but it is expected to be transported in lengths of 100–200 m. Some details of possible joint and termination designs are given.

DOI:10.1049/piee.1976.0032

出版商:IEE    

年代:1976

数据来源: IET

摘要:

An investigation into the parameters affecting partial discharges in liquid-nitrogen impregnated taped insulation using cylindrical-cable models is described. The inception voltage increases with pressure and for all but the thinner tapes studied little change occurs after 197.8 × 105N/m2(14 lbf/in2g.). The inception stress also decreases with increase in tape thickness. Several plastics have been used in this work. Nomex, polyethylene and polycarbonate tapes are seen to be reasonably discharge resistant whereas Tyvek, Tenax and l.l.p.p./paper are not. The effect of stress on discharge magnitude is investigated and initial work on insulation life as a function of discharge activity reported.It is postulated that the discharges occur in nitrogen gas bubbles in the butt gaps of the insulation. Possible theories for this initial formation of these bubbles are discussed but no mechanism at this stage appears pre-eminent.

DOI:10.1049/piee.1976.0033

出版商:IEE    

年代:1976

数据来源: IET

摘要:

An algorithm, based upon a functional description of system stability, is implemented in real time to detect the onset of instability in a class of nonlinear or time-varying systems. It is shown that this stability supervisor can then provide the decision policy for an adaptive controller.

DOI:10.1049/piee.1976.0036

出版商:IEE    

年代:1976

数据来源: IET

摘要:

The question of achieving decoupling and asymptotic disturbance rejection in time-invariant linear multivariable systems subject to unmeasurable arbitrary disturbances of a given class is discussed. A synthesis procedure which determines a feedback structure, incorporating an integral compensator, is presented.

DOI:10.1049/piee.1976.0037

出版商:IEE    

年代:1976

数据来源: IET

摘要:

The feasibility of solving 2-dimensional saturable eddy-current problems using an alternating-direction-implicit method to solve the finite-difference equations has been investigated. A simple single-dimensional problem has been tackled in a 2-dimensional manner, and results compared with existing single-dimensional solutions. Saturation is represented by the Fröhlich equationB=H(a+bH)−1. Only one recalculation of reluctivity per time step has been used. This gives substantial savings in computing time and cost, although the method is accurate only for mild nonlinearity. Stronger nonlinearity, representative of heavily saturated parts of the magnetic circuit of electrical machines, requires reluctivity iteration at each time step. The improvement of convergence, by suitable choice of underrelaxation factor, is demonstrated, and also the failure of two possible accelerative procedures using line-integral and surface-integral correction.

DOI:10.1049/piee.1976.0040

出版商:IEE    

年代:1976

数据来源: IET

摘要:

Experiment shows that the impulse electric strength of prestressed polythene film varies appreciably, whereas without prestress it remains constant during a period following quenching from about 100°C. The phenomenon is attributed to morphological changes which influence the density of traps and hence the space charge formed by the prestress.

DOI:10.1049/piee.1976.0041

出版商:IEE    

年代:1976

数据来源: IET