This page contains a Flash digital edition of a book.
ELECTRICAL SERVICES WHOLE-LIFE COSTS


of losses and and cut in CO2 emissions. As these losses are normally attributed as business energy use that are not subject to Building Regulations constraints, it is strongly recommended that electrical building services engineers develop and implement the WLTOC solution for new- build or rennovation projects. The simplified example of a three- transformer scheme is used above to illustrate the principle of WLTOC, engineers can also consider a two- transformer design option for such a building. This option can provide added advantages whereby the resulting changeover control system is less complicated, and less space is required in the substation. These advantages were not included in the comparison tables and they can be a significant factor contributing to the final decision taken by the project team. One small drawback of applying the two-transformer option is that it will necessitate a substantial increase in the full-load power rating of the transformers. This will impose a much higher fault


www.cibsejournal.com


current rating to the transformers, as well as to the rest of the electrical system in the building. To aid engineers in checking the maximum fault level in electrical systems, an article was published the September 2010 issue of CIBSE Journal that presented a Fault MVA calculation method to help verify fault level calculations done to comply with BS7671:2008 and BS EN 60909-0:2001. Finally, although the transformer purchase prices (which include a professional fee for the electrical building services engineer) were based on assumptions made by the authors, the WLTRC and CO2 emissions results are based on typical building operating hours and EN50464-1. Therefore the outputs of this article are well within acceptable accuracy limits for real world practical applications.


l Dr Tony Sung is from the CIBSE Electrical Services Group, Dr ya Ping Du is at the Hong Kong Polytechnic University, MarTy BarreTT is from Dublin Institute of Technology, and Laurie BraDy is at Liverpool John Moores University


The ‘whole-life total ownership cost’ approach can deliver the best value electrical supply design scheme


References 1.


Rau, NS., 2003, Optimisation Principles – Practical applications to the operation and markets of the electric power industry, Wiley – Interscience, IEEE


2. EN50464-1:2007, Three-phase oil-immersed distribution transformers 50 Hz. from 50 kVA to 2 500 kVA with highest voltage for equipment not exceeding 36 kV - Part 1: General requirements EN50464-1, CEN, CENELEC and ETSI


3. British Standards Institution (1991) BS 7450:1991 Method for Determination of Economic Optimisation of Power Cable Size, Milton Keynes, BSI


June 2011 CIBSE Journal


51


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72