DOI:10.1049/ree.1969.0077

出版商:IERE    

年代:1969

数据来源: IET

摘要:

The C.E.G.B. generates power to meet the instantaneous demands of the eleven Electricity Boards in England and Wales (maximum 35 800 MW in January 1968). With 230 generating stations and grid transmission at 400, 275 and 132 kV and with 700 grid switching and/or high voltage transforming stations, the C.E.G.B.'s integrated power system is the largest in the world under unified control.To control and protect this countrywide power system, the C.E.G.B. requires a correspondingly large network of more than 2000 communication links. The paper briefly describes the CE.G.B.'s three-tier control system which operates at district, area and national levels, and was arrived at over 30 years of control of the British 'Grid'. Some of the philosophy which has gone into the planning of the networks and into the design of the associated speech, remote control, general indication, telemetering and high-speed protection installations is explained.

DOI:10.1049/ree.1969.0078

出版商:IERE    

年代:1969

数据来源: IET

摘要:

It is shown that the ratio of input voltage to output voltage for any passive ladder type low-pass filter network is always a polynomial in the complex frequency s. This polynomial can always be written by inspection as a single determinant in the form of arecurrent. The recurrent determinant is then converted by elementary manipulation into an alternate form known as acontinuant. The transfer function of any passive ladder type low-pass filter network can also be written by inspection as a single determinant in continuant form. The synthesis of such networks is thus reduced to the simple procedure of writing the given transfer function in recurrent form by inspection, use of simple arithmetic operations to change the recurrent into continuant form, and reading the numerical values of the network elements directly from the continuant.

DOI:10.1049/ree.1969.0079

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Simple random number generators using integrated circuit shift registers are being employed to make random selections of points on multi-element (12 000 array points) ultrasonic planar transducers.The transducer is a 2-in (5 1 cm) diameter piezoelectric plate used to detect the scattered acoustic field caused by an object placed in an ultrasonic field. The transducer is digitally scanned to enable information from discrete points to be encoded for image reconstruction by computer processing. For unambiguous reconstruction, point spacing of one halfwavelength is required. This would require 12 000 sample points, and processing this information would be unwieldy. Removing the points randomly according to a specific density distribution enables up to 95% of the points to be removed with little deterioration in transducer performance.Computer simulations of the thinned array have been completed and these confirm that the transducer directivity patterns are satisfactory in the far-field and focused near-field.

DOI:10.1049/ree.1969.0080

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Frequency modulating (f.m.) transducers are instruments whose output frequency is proportional to the measured physical parameter, such as flow (turbine flow meter), radiation (Geiger counter), pressure, density etc. The paper deals with the advantages of using f.m. in process plants and describes some f.m. instruments which measure flow, pressure, temperature and density.

DOI:10.1049/ree.1969.0081

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Some features of radio-refractivity which are important from engineering point of view are described with reference to published data on radio-refractivity up to a height of 3 km from the surface of the Earth and radiosonde data on pressure, temperature and humidity up to 4.5 km covering a period of five years. Three broad radio-climatic areas having distinct meteorological and refractivity characteristics are delineated. Correlation between surface refractivityNsand the difference of refractivity over height-intervals of 1 km and 2 km from the surface, designated as ΔN1and ΔN2respectively, is examined. For coastal areas and islands, correlation with either ΔN1or ΔN1is found to be poor, while for landbased stations, it is observed to be good. An approximately exponential relationship relates the variation ofNsand ΔN1. Several models for height variation of refractivity are examined and compared with observed structures. A bi-exponential model for inland region and a two-part model consisting of a linear variation up to 1 km or 1.5 km followed by an exponential variation for coastal areas appear to be satisfactory. The long-term transmission loss predicted on the basis of this model and corresponding observed values in case of one trans-horizon radio circuit are found to be in fair agreement.

DOI:10.1049/ree.1969.0083

出版商:IERE    

年代:1969

数据来源: IET

摘要:

Weighing objects in motion poses problems which are quite distinct from those encountered in static weighing. Until recently no serious attempt had been made to tackle these problems.The paper discusses the weighing errors caused by the motion of the object being weighed. Methods of reducing these errors are described and an assessment is made of the effectiveness of these methods.A novel approach to this problem is outlined with graphs of performance. Results obtained by this approach are compared with those obtained by current methods.

DOI:10.1049/ree.1969.0084

出版商:IERE    

年代:1969

数据来源: IET