摘要:

The paper is devoted to an evaluation in detail of the protection coverage afforded by earth- and phase-fault distance relays in terms of the range of apparent impedances presented to them for which the protection correctly operates and initiates circuit-breaker tripping. This requires a knowledge of both the effective polar characteristics of relays for specified system-fault conditions and also, for the same conditions, the apparent impedance to which the relays respond. Owing to the wide variation encountered in both of these in practice, the ordinary static characteristics of relays provide only a limited indication of the discriminative properties of distance relays in different applications, but it is shown how a comprehensive assessment may be made. In particular, investigations are described of the performance of mho relays when applied to 132kV and 400kV circuits, and the results of the investigations are summarised. The studies include the response to faults within the protected zone, the discrimination against external reverse faults, against healthy-phase relay operation and, on double-circuit-line constructions, the discrimination against healthy-circuit relay operation. The time response of comparators in impedance measurement is introduced, and it is explained how, evolving from this, the coverage afforded by the protection may be directly related to its operating time. In this way a basis is provided on which the operating time of distance relays may be systematically linked to its discriminative properties.

DOI:10.1049/piee.1968.0022

出版商:IEE    

年代:1968

数据来源: IET

摘要:

Until recent years, the problem of penetrating a pressure bulkhead with an electric cable was a simple matter, as the pressure differential was never more than a few hundred pounds per square inch. Simple packed glands were developed which served adequately at the low pressures involved, but, as the pressure differential became higher, the limitations of the simple gland became apparent. With the advent of the submarine-cable repeater, a new approach to the problem resulted in a single-core gland capable of with standing the greatest depths. The basic technique of this new approach has now been applied to multicore cables and multiway glands, and a range of glands has been developed which is being used almost exclusively by the UK Ministry of Defence (Navy) in British submarines. For oceanographic-instrumentation capsules, these glands have been tested over long periods at a pressure of 100001bf/in and are considered to be capable of withstanding the pressure on the floor of the Marianas Trench. The fundamental design of the gland is based on bonding polythene to metal and the use of polythene-insulated cables. All glands are factory- made and are tested to pressures in excess of the equivalent of the maximum usage depth; a portable moulding kit is used to join cables after installation. In many instances, a fully prefabricated cable harness has been used, wjth the assurance that on entering service the equipment is completely watertight. This method has been used to connect all the external electrical circuits in deep-diving and conventional RN submarines; it has also been applied to a number of oceanographic instruments.

DOI:10.1049/piee.1968.0023

出版商:IEE    

年代:1968

数据来源: IET

摘要:

The paper describes experimental work carried out at the Shiobara Laboratory on the performance of salt-contaminated insulators in both natural and artificial humid conditions. The purpose was to analyse, in relation to humidity, one type of flashover mechanism caused by salinity deposited on a porcelain surface and absorbed moisture in humid conditions. For natural humid conditions, dew, fog and drizzle were available. Based on experience of natural humid conditions, an artificial test with steam fog permitting the gradual formation of humid conditions, was developed. This method produced a flashover voltage of the insulators similar to that in natural conditions. An antifog-type insulator showed the best performance for the insulators that have similar flashover voltage. However, flashover voltages of the two long-term tests showed a great difference from that of the conventional short-term test. A hypothesis of ‘danger degree for flashover’, is assumed in order to explain the essential differences between the pollution- test methods and results. The danger-degree concept is a combination of two factors: transfer of salinity and humidity

DOI:10.1049/piee.1968.0024

出版商:IEE    

年代:1968

数据来源: IET

摘要:

In the last few years the theory of natural modes has become an accepted form of analysis for multiconductor systems. This theory is used in the paper for two purposes; first, to determine optimum methods of carrier coupling in vertical and horizontal conductor configurations, including the effect of coupling equipment and line traps. Numerical results are given for a number of limiting conditions relating to busbar impedances. The general conclusion is reached that, in horizontal systems, coupling should be near the centre of the conductor group, in vertical systems it should concentrate toward the top of the conductor group. Secondly, the theory is extended to a nonhomogeneous system made up of a teed-feeder arrangement with a short section of cable in one leg of the tee. Numerical results are given to show the large insertion loss which occurs at frequencies which make the cable length an odd multiple of one quarter of a wavelength in the region.

DOI:10.1049/piee.1968.0026

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0029

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0030

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0031

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0032

出版商:IEE    

年代:1968

数据来源: IET

DOI:10.1049/piee.1968.0034

出版商:IEE    

年代:1968

数据来源: IET

摘要:

Design equations are derived for a particular extremum-control system. The system has a single-input plant with input disturbances, measurement noise and an output lag; the control signal is generated by adding a sinusoidal perturbation to the plant input and demodulating the corresponding perturbations in the plant output. A linearised equivalent circuit is introduced, and a numerical measure of how accurately it approximates the system is determined experimentally. The measure of accuracy is combined with standard analytic results about the performance of the equivalent circuit to give an equation describing the performance of the system. The equation leads to design curves giving the best values of controller parameters for any given set of plant-parameter values. An experimental verification of the design procedure shows that it is valid for systems where the output lag is not the dominating factor.

DOI:10.1049/piee.1968.0035

出版商:IEE    

年代:1968

数据来源: IET