H. E. Orton
IEEE Dielectric and Electrical Insulation Society
Orton Consulting Engineers International Ltd.
Harry Orton, an electrical engineering and applied science graduate of the University of New South Wales and University of British Columbia, first worked at BC Hydro in Vancouver, Canada as an electrical engineer where he helped build one of the largest utility-based research centres in North America. For over 20 years he worked as a specialist in the field of underground and submarine power transmission and distribution cables and accessories, later becoming section supervisor in charge of insulation studies and manager of technical activities.
Formerly a project manager for CEA and EPRI underground cable research projects and chair of the Cable Failure Task Force, Harry now runs Orton Consulting Engineers International Ltd., which is based in Vancouver, Canada and affiliated with the International Consulting Engineers. Harry has published over 60 technical papers and is currently working on the second edition of his book entitled “Long-life XLPE Insulated Power Cables”.
Harry is active in the IEEE ICC and the ICPADM as well as a member of CIGRE and a member of the Jicable Scientific Committee located in Paris.
Impact of Electromagnetic Fields on Current Ratings and Cable Systems
Numerous methods have been devised by electric utilities and various research organizations to manage power frequency magnetic fields levels in the vicinity of underground cable systems. Information is available in CIGRE TB 373, from Working Group C4.204, concerning considerations for implementing the various methods, their impact on construction and their cost effectiveness. However; their impact on cable rating, losses, installation and operational costs needs to be evaluated. In particular, there are differing opinions about the de-rating effects of HV transmission cables placed in ferromagnetic shielding enclosures such as pipes or casings. Past work at CIGRE and elsewhere addressed magnetic field calculation procedures (with and without ferromagnetic components); however, they do not address the current rating reduction of the magnetic field management methods or their practical applications to electric utility systems.
In most cases mitigation measures have disadvantages: either the current rating may decrease or the costs will increase. Some mitigation methods are very cost effective, for example, an optimal choice of the phase sequence for double circuits/systems. The first question to answer is where mitigation is required: to reduce the magnetic field directly above the cable circuit, or to reduce the field to a certain limit at a specified distance from the cable circuit, or to minimize the width of the corridor within which a specified field limit is exceeded.