Biological Effects of Power Frequency Electric Field Shielding

As a rule, the conductive suit is the main personal protective means (PPM) from power frequency electric field exposure at switchyards and overhead transmission lines. PPM should ensure reduction the high intensity power frequency (PF) EF (50/60 Hz) lower than permissible limit values. Actual problem is to assess the protective properties of typical modern PPM taking into account biological significance study of the shielding coefficient (Ks). Ks value must comply with requirements, established in normative documents. According to Russian standards GOST 12.4.172-2014 “Occupational safety standards system. Individual screen set for protection from power frequency fields. General technical requirements and test methods” and TR TS 019/2011 “On the safety of personal protective means” currently minimum permissible screening factor is 30dB. According to IEC 60895-2002 “Live working. Conductive clothing for use at nominal voltage up to 800 kV a.c. and ±600 kV d.c.” for class 1 the minimum value prescribed for screening efficiency is 40 dB and for class 2 is 50dB. The task of this study was laboratory animals' functional state assessment after different PF EF exposure conditions, shielded and non-shielded. The experiment exposure condition were simulated using the software product SEMCAD X v.14.8 (“SPEAG AG”, Switzerland). The developed models included setup (plane-parallel capacitor) with required PF EF levels, shielding material and rat phantoms, were developed. The capacitor consists of two metal plates and provide the required homogeneous PF EF intensity in the work area. The RMS PF EF strength was 50 kV/m, the screening factor was 50dB. Three experimental groups were formed from laboratory male rats (200 ± 10g weight, 36 laboratory animals). One group was under screening conditions (50dB), another group was in PF EF (50 kV/m) and the third group was sham-exposed. All groups consisted of 12 laboratory rats. For estimation of laboratory rats' behavior parameters was used the open field method. After first day of the experiment the behavior parameters were different in control group and the group in PF EF with p <; 0.05. Lipid peroxidation was assessed by indicators of diene conjugates and ketodienes. After fifth experimental day the behavior parameters were different in control group and the group in PF EFwith p <; 0.01.