Efficiency of insulating link for protection of crane workers (from power overhead lines)

The protection efficiency of insulating links under different operating conditions is analyzed. Both a steady-state model and a transient model have been developed for simulation of the system. The models simulate the electrical supply, the crane insulator link, the body impedance of the worker, and the grounding resistance. The MICROCAP AC, DC, and transient analysis program was used to calculate the current and voltages which endanger the crane worker. The results show that the insulating link in clean conditions reduces the current under the harmless let-go level. However, polluting and wetting the insulating link may increase the current above the dangerous ventricular fibrillation level. The contact between the power line and crane causes a short-duration high-amplitude transient current which, in adverse conditions, can cause heart fibrillation. Based on the experimental evidence, it is concluded that in spite of the shortcomings, the insulator link increases the safety of crane operation. Furthermore, the model and calculation method can be used for the evaluation of new crane insulator systems.<
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