IEC 61472-2-2021 pdf Live working – Minimum approach distances – Part 2: Method of determination of the electrical component distance for AC systems from 1,0 kV to 72,5 kV

3.1 highest voltage of a system U s highest value of operating voltage (phase-to-phase voltage) which occurs under normal operating conditions at any time and any point in the system Note 1 to entry: Transient overvoltages and permanent induction from adjacent lines are not taken into account in the calculation formula
3.2 transient overvoltage short duration overvoltage of a few milliseconds or less, oscillatory or non-oscillatory, usually highly damped [SOURCE: IEC 60050-61 4:201 6, 61 4-03-1 4] 3.3 nominal system voltage suitable approximate value of voltage used to designate or identify a system [SOURCE: IEC 60038:2009, 3.1 ] 3.4 per unit statistical overvoltage phase-to-earth u e2 phase-to-earth per unit overvoltage that has a 2 % probability of being exceeded 3.5 per unit statistical overvoltage phase-to-phase u p2 per unit overvoltage that has a 2 % probability of being exceeded 3.6 statistical overvoltage U 2 overvoltage that has a 2 % probability of being exceeded 3.7 minimum approach distance D A minimum electrical and ergonomic distance in air to be maintained between any part of the body of a worker, or any conductive tool being directly handled, and any live conductors or equipment at different potentials 3.8 electrical distance D U electrical component of the minimum air distance between two electrodes which represent live and/or earthed conductors or equipment, required to prevent sparkover under the most severe electrical stress that will arise under the chosen conditions 3.9 ergonomic distance D E distance in air added to the electrical distance, to take into account inadvertent movement and errors in judgement of distances while performing work [SOURCE: IEC 60050-651 :201 4, 651 -21 -1 3, modified – the symbol D E has been added.]
5 Factors influencing the minimum approach distance 5.1 Control of system overvoltages The maximum amplitude of overvoltages in the work area can be reduced by the usual practice of making the circuit-breaker reclosing devices inoperative, or by using protective gaps or surge arresters.
5.5 Determination of minimum electrical distance, D U The minimum electrical distance is determined from the impulse rod-to-rod withstand voltage of IEEE 51 6-2009, Table 1 , and presented in Table 2 and Table 3. For systems using other per unit overvoltage factors the minimum electrical distance may be derived from Table 1 using linear interpolation.