Given the increased political salience of environmental constraints on the energy sector at large, and on power generation in particular, some of the principal policy issues which impinge upon the electricity supply industry (ESI) are examined. Particular emphasis is placed on the two most prominent issues: acid rain and global warming. More emphasis is given to supply-side issues rather than demand-side responses (such as least cost planning). The paper then examines the major characteristics of the UK's stock of generating plant and some of the means available for the ESI to adjust this stock in the light of both specific environmental and wider political pressures.
A system of ‘telegrapher's’ equations for a number of long lines joined into a network is studied. Explicit formulas for Fourier transforms of current and voltage are derived. These formulas are very suitable for computer application as well as for the analytical study of processes on networks. As an example, the availability of formulas aids the derivation of explicit formulas for maxima of current amplitude over the given class of admissible external influences. These values may be used to indicate the characteristic of network robustness to excess voltage or electromagnetic impulse. The approach is based on the operational solution already proposed by the author for more general partial differential equations on graphs.
A study has been made of the feasibility of applying optical fibre sensing technology to acoustic monitoring of partial discharges within gas insulated substations (GIS). A test rig has been constructed to simulate a section of GIS in which acoustic sources could be placed. This has been used to test the optical systems which showed greatest promise of having the capability of monitoring these partial discharges. Experimental results are presented which show that acousto-optical sensing, using fibredyne interferometry, of partial discharges within GIS is feasible in principle. However, further work is needed to extend the sensitivity range to acoustical amplitudes of about 10-14 m which correspond to signals from the weakest discharges requiring detection.
This paper introduces an electro-optical target system (EOTS) covering the speed range from subsonic to supersonic. This microcomputer-based system has a novel structure and shows the capability of precisely detecting the position as well as the velocity of small calibre projectiles in real time. A prototype EOTS whose target area is 1 m2 has been constructed and tested. A speed accuracy of better than 0.3% was achieved. A position accuracy, mainly dependent on the spacing between photodiodes in EOTS, of better than 1 mm on a target area of 1 m2 was also accomplished.
The Italian Navy coherer was a receiving device used by Marconi in this first transatlantic transmission in 1901. A great controversy, which threatened to tarnish Marconi's reputation, arose concerning the invention of this coherer. The author re-examines the affair, and also includes some technical observations as to the coherer's precise mode of operation. >
Resonance substitution techniques, such as the Hartshom-Ward method provide an accurate measurement method for the determination of the dielectric properties of materials. They suffer from the disadvantage that their results depend on the accurate determination of the Q factor of a resonant circuit: a parameter that is not readily traced to national standards of impedance. The paper outlines measurements on a standard inductor and shows that modern four-terminal measurement techniques, when used with a suitable resonance adaptor, can provide more consistent values of Q than could be obtained with a Q-meter. The new four-terminal technique is shown to provide results consistent with earlier standard methods and may thus be suitable for wider application.
All-dielectric, self-supporting, optical cables can suffer from damage caused by dry-band arcing. This problem only occurs when the cables are strung on power lines whose system voltages are in excess of 150 kV, in areas which are subject to pollution which is conducting when wet, for example saline pollution. It is the aim of the paper to promote discussion, by proposing and subjecting to preliminary examination several devices which may be able to control the arcing which causes the damage. It is concluded that the study of such devices is worth pursuing.
Suitable sites for tidal power generation are mostly situated in estuaries, where with a high tidal range of 5–15 m, the construction of a barrage is proposed to impound water during tidal rise. Electricity is then generated using turbines exploiting the difference in level as the tide drops outside the impounded area. Most sites of this kind contain complex and productive ecological systems. Their importance, for example, for the migrant and over-wintering waterfowl usually supported by these estuaries, can be at an international level. The impoundment of water behind a barrage can submerge intertidal flats used as feeding areas by these waterfowl. Furthermore, by reducing tidal height, a barrage can affect the extent of saltmarshes which are not only important feeding grounds but which also have intrinsic interest for their unusual flora. The potential environmental impact of tidal power barrages can, therefore, be serious. The impoundment of an estuary can also create water quality problems, if there are sources of pollution feeding into the system. This may require major investment in effluent treatment before the project can proceed. The most important factor with respect to water quality change is the reduced tidal currents, following impoundment, acting with the additional retention time of water in the system to compound pollution problems. However, the problem may be reduced due to the larger mean volume of water in the impounded estuary. Further environmental effects of tidal power generation can include matters concerned with coast protection, flood control and groundwater. The creation of a large impounded area can lead to pressure for its development as a waterbased leisure facility. Leisure development, particularly the use of powered boats, can lead to conflict with nature conservation interests. The paper discusses all the above issues and, despite the clear fact that all the matters involved are clearly site-specific, some overall conclusions will nevertheless be drawn concerning the environmental effects of tidal power generation in relation to alternative methods of electricity generation.
Partial discharge (PD) specifications exist for all types of electrical equipment except motors and generators. Whereas specifications essentially require that the equipment is discharge-free the stator conductor bar insulation of the motors and generators under consideration is micaceous and has excellent PD resistance. Consequently, the intention in a specification would be to permit a certain level of PD. It is therefore particularly important that the problem of overcoming the attenuation between the PD site and the measurement equipment at the winding terminals be solved. Within the general context of examining the feasibility of a PD specification, the problem of PD signal attenuation is addressed. The approach adopted was to seek a region of low attenuation by examining the whole of the possible range of PD measurement frequencies. The investigations described consist of experiments on a full-size 500 MW endwinding model and on two large high-voltage motor windings. Careful screening to reduce radiative pick-up from the calibration generator simulating a PD source and a direct earthing scheme enabled the essential elements of PD pulse transfer through a winding to be determined. The frequencies investigated ranged from kHz to GHz. Pulse transmission and frequency spectrum measurements were made. It is concluded that the PD pulse transmits essentially as a travelling wave, the high-frequency components being highly attenuated. No significant crosscoupling was apparent through the end-winding region. The windings acted as a low-pass filter, the cut-off frequency being dependent on the winding length, and being below 1 MHz. Consequently, it is concluded that it should be possible to measure PD, using equipment with a passband below the low-frequency cut-off, with low attentuation.
The meeting was arranged by Professional Group S7, 'History of Technology', under the chairmanship of Dr. Arnold Lynch, to discuss the development and impact of the very earliest computing devices designed for wartime applications, the first official disclosures of which became available in the public domain during 1977. At Savoy Place were gathered together, for the first time since World War II, many of the key figures responsible for these early designs, which are now considered to represent the first digital electronic computers. The major contender among these designs was undoubtedly the code-breaking device known as Colossus, developed at Bletchley Park during the 1940s. Before introducing the speakers, the chairman for the meeting, Prof. Russell Burns, presented a brief synopsis of the technical background to the work undertaken during the early days of the War in May 1940.
The power generation industry is facing one of its greatest challenges. As the demand for energy is increasing, so is the environmental damage caused by the combustion of fossil fuels to generate electricity. The industry is now recognising the need for new, or adapted, generation technologies that limit harmful emissions of greenhouse gases. One such technology is the fuel cell, which offers the prospect of a new, silent, modular technology with few or no problems of emissions. The paper describes the principles of operation of fuel cells. Four types of fuel cell are covered: solid polymer electrolyte, phosphoric acid, molten carbonate and solid oxide. The perceived advantages of fuel cells and international and UK fuel cell development programmes are discussed.
When AC high voltage is applied in air to a cylindrical insulator with a backing electrode the polarity of generated leaderlike surface discharges depends on the contact angle. The contact angle is the angle between the insulating surface and high voltage electrode on the insulator. In the range of the angle from 60 degrees to 120 degrees the negative surface leaders appear; in the range from 120 degrees to 180 degrees the positive surface leaders appear. No negative surface leaders appear in the range of the angle from 120 degrees to 180 degrees . The onset voltage of the positive leader is higher than that of the negative one. AC flashover voltage along the surface in air also shows dependence on the contact angle, which results from the difference in the onset voltage between the positive and the negative leaders. Impulse flashover voltage, on the other hand, shows no precise contact angle dependence.
The long-time operation of a high breaking capacity fuse using notched strip elements and M-effect alloy, is governed by the interrelationship between the element current distribution, the corresponding element temperature distribution and the M-effect diffusion rate. This paper describes a new method developed to model these complex effects, and hence determine fuse pre-arcing behaviour. The method is based on modelling both temperature and diffusion as electrical analogues and the utilisation of a computer circuit analysis software package to simulate the resulting circuitry. The model enables fuse parameters to be studied to depths previously not possible, and offers considerable possibilities in the fields of fuse design and fuse applications.
Long-span, all-dielectric, self-supporting cables have been developed as a result of demand for optical fibre based communication systems on overhead power lines. After considerable experience and successful operation on towers carrying circuits whose system voltages are less than 150 kV, these cables have been installed on higher voltage lines. In such circumstances, degradation of sheathing materials has occurred and this has been attributed to gradual erosion by dry-band arcing. New results of ageing by dry-band arcing are presented and conclusions are reached which are important in the testing of materials. A new feature is added to the dry-band arc model of failure. This allows the length of an arc to be gradually reduced by the movement of moisture along the cable. It is shown experimentally that if such arc compression does take place, the cable can be severely damaged by only a few seconds of this activity. It is suggested that the lifetime of a cable might be effectively determined by the time to one such period of activity rather than the ability of a cable to withstand long periods of stable dry-band arcing.
It is shown that ultrasonic agitation of insulating oil in service (i.e. contaminated oil), as proposed prior to electrical-breakdown tests, does not affect its chemical structure. On the contrary, it homogenises particles within the sample giving it a more realistic breakdown-strength value far more representative of actual values under service conditions.
Owing to the many advantages and versatility of electricity, its share in the global demand for energy in final use is increasing. In 1990, global electricity generation amounted to 11 700 TWH and fuels for electricity production consumed 36% of the total global primary energy needs; which is more than twice their share in the 1950s. More than half of the electricity consumption occurs in OECD countries, however prospects for future demand growth are in developing countries. With increasing populations, higher economic growth, and the present modest use of electricity and energy, these countries are likely to consume a larger share of the electricity market in the future. Their demand growth rate will most likely be moderated by an acute shortage of capital. Future electricity generation technologies will aim towards improving efficiency, clean emissions, low capital cost and short lead times. Therefore, gas turbines and combined cycle plants will gradually assume a larger share of the power generating equipment market. For many decades to come, coal, because of its abundance and cheapness, will remain the world's major fuel for electricity generation. Natural gas, owing to its cleanliness, will be more in demand. However, the shares of hydro- and nuclear fuel, owing to their highly capital intensive nature and other considerations, are not likely to increase.
Electronic devices are used in five different ways in various techniques of measurement. The conditions which they have to meet are not the same in all cases; hence, they were introduced at various times when the available techniques could meet some new condition. Some innovations were possible in the era of thermionic valves, others had to await semiconductors and the logic developed for computers. Confidence in the older methods resulted from long experience. Equal confidence in electronic methods will require similarly long experience.
A method of locating discharges during breakdown tests on medium-voltage cables is described. The resistive screen of the cable attenuates the discharge pulses and the location is made by using the magnitude of the pulses recorded at each end of the cable, allowance must be made for pulse reflection. Tests on an 11 kV polyethylene insulated cable that contained large vented water trees are used to illustrate the method. Total discharge energy and location were recorded for a single discharging site. The test was stopped prior to breakdown and a volume of insulation containing a single electrical tree was cut from the cable. The computed discharge energy was compared with the eroded volume within the electrical tree.
The paper describes a novel variable time step technique for the transmission line modelling (TLM) method. The proposed method enables simple and efficient modelling of systems with widely spread time constants by allowing the time step to be changed with no loss of accuracy. The correct initial conditions and algorithms are also discussed. The principle of the method is explained and the method verified by numerical examples.
