Efficiency of insulating link for protection of crane workers

A crane worker can be exposed to a dangerous electrical shock when the crane touches high-voltage electrical lines, so an insulator link is used to protect workers. This paper analyses the protection efficiency of insulating links under different operating conditions. Both a steady state and 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. The paper concludes that in spite of the shortcomings, the insulator link increases the safety of the crane operation. Furthermore, the developed model and calculation method can be used for the evaluation of new crane insulator systems.