C I R E D 20 th International Conference on Electricity Distribution Prague, 8-11 June 2009 Paper 0182 CIRED2009 Session 2 Paper No 0182 MAGNETIC FIELD RISK EVALUATION OF WORKERS IN INDOOR DISTRIBUTION SUBSTATIONS Tommi KEIKKO Rauno PÄÄKKÖNEN Tampere University of Technology – Finnish Institute of Occupational Health – Finland, tommi.keikko@tut.fi Finland, rauno.paakkonen@ttl.fi Sami KÄNNÄLÄ Reino SEESVUORI Seppo VALKEALAHTI STUK, Radiation and Nuclear Safety Tampere Power Distribution – Tampere University of Technology – Authority – Finland, sami.kannala@stuk.fi Finland, reino.seesvuori@tampere.fi Finland, seppo.valkealahti@tut.fi ABSTRACT The scope of this paper is on magnetic field exposure of workers in indoor medium to low voltage (MV/LV) distribution substations. In this paper we present magnetic field hazard evaluation based on measurements, specifications to execute them and specifications for risks assessment procedure. Action values were exceeded in several working tasks but limit values were not exceeded. 1. INTRODUCTION Due to possible health effects of electric and magnetic fields, International Commission on Non-Ionizing Radiation Protection (ICNIRP) has published guidelines, in which upper limits for occupational exposure have been presented [6,7]. Based on the guidelines European Parliament and Council have adapted a Directive on minimum health and safety requirements regarding the exposure of workers to electromagnetic fields in 2004, which will be nationally implemented in 2012 [5]. In power distribution the main source of exposure is the magnetic field induced by high currents, typically found occasionally on the low voltage side of distribution substations. To be able to comply the Directive and the forthcoming legislation power distribution companies as well as authorities are seeking for guidelines and concepts how to evaluate the risk for exposure on magnetic field in power distribution environment. General risk assessment is a part of occupational health risk protection. It includes also magnetic field risk evaluation. According to the Directive the magnetic field exposure limit value is not allowed to be exceeded at all. Therefore, if the action value is exceeded in some working environment further actions are needed to ensure that the limit value is not exceeded. Possible actions are magnetic field mitigation or dosimetry, in which induced currents in the body of the worker are evaluated. Dosimetry can be carried out with advanced calculation or measurement methods [9]. In this paper magnetic field risk evaluation is based on genuine magnetic field exposure measurements. They include broadband magnetic field and exposure measured synchronously with load currents, total harmonic distortion of the magnetic field, magnetic field exposure ratios for workers, and total harmonic distortion of the load current. Based on these results further conclusions on the risks are made by an occupational hygienist. 2. METHODS 2.1. General risk assessment Risks which are arising in working with electricity distribution are classified based on BS 8800 general risk classification procedure [1], which is a two dimensional evaluation procedure involving the health consequences and the probability of occurrence, which both have three classes. Table 1 presents the classification of the BS 8800. Table 1. General risk classification based on the British standard BS 8800 [1]. Consequence Probability of occurrence Slightly harmful Harmful Extremely harmful Highly unlikely Trivial Tolerable Moderate Unlikely Tolerable Moderate Substantial Likely Moderate Substantial Intolerable Employers are responsible for carrying out the risk evaluation. Occupational health care personnel can collaborate with them about the evaluations of the health effects of the physical inputs. Also authorities enforcing forthcoming legislation based on the directive 2004/40/EC will collaborate. Especially in cases of high and complicated risks the use of an external evaluator is recommended. Risk assessment means an objective point of view of the risk specialist. This can mean that, e.g., the magnetic field exposure can be experienced to be high, but the risk is still insignificant with respect to other risks. General risk management means all different operations, which can be executed to decrease the risks. Usually the risks cannot be removed, but the residual risk can be managed, e.g., with insuring against hazards, outsourcing the work, or using personal protective equipment. As well, anticipation, leadership, training, and development of practices are parts of the risk management. Fig. 1 presents the overall magnetic field exposure measurement and risk