| Popis: |
Methods for safely performing works on a disconnected overhead power line under induced voltage conditions in compliance with the regulatory documentation requirements are considered. According to the "Rules for Labor Protection in Operation of Electrical Installations", work under induced voltage can be performed in one of two ways: grounding the overhead line at both ends and at the workplace (using the potential equalization technology or "without de-energization" for doing work) and with the overhead power line grounded only at the workplace. It is believed that by applying these methods the voltage induced on the disconnected line can be reduced to a safe value of 25 V. It is shown that the methods for safe performance of work on a disconnected overhead line stipulated by the regulatory documents ensure a relatively low reliability of repair personnel protection against being injured by induced voltage, in view of the influence of the human factor on the electrical safety. It is proposed to enhance the safety of work on a disconnected overhead power line by applying protective grounding through the use of a grounding electrode at the workplace with resistance sufficiently low for reducing the induced voltage to acceptable values. Analytical expressions have been obtained, using which it is possible, based on the results of induced voltage measurements, to determine the required value of the workplace grounding resistance and the level to which the induced voltage level is reduced as a result of grounding the overhead power line wires at the workplace. Proposals have also been developed on introducing amendments in the regulatory documents aimed to ensure more reliable protection of repair personnel against being injured by induced voltage. |
