Contacts and not collisions with electrical equipment: a new approach of the electric risk assessment

An IEC main protection against electric hazards by shock or burns or fire is the “active” measure. It is based on preventing the persistence of the electrical hazards limiting the time duration of the risk exposure to the contact for shock and fire and to the fault consequences. The active protection of detecting the hazardous fault and disconnecting automatically the supply is named in the paper "π-protection" to highlight the characteristic profile of the risk exposure. For studying the near miss incidents, complying with the Heinrich theory, characteristic parameters are introduced that allow dealing with the various classes of the "π -protection" like with dynamical collision problems. Considering the components of an electric hazard like massparticles in motion, the protection practice in IEC standards solves:- avoiding the 'collision', limiting the fault exposure time (probable protection);- controlling the 'collision', limiting the risk “weight” (safe conventional protection) or at the least limiting the colliding time (additional protection). In particular, the IEC approach recognizes the " -protection": - against indirect contact, coordinated with grounding, as acceptable, considering improbable the simultaneous operator contact (probable protection), and more as safe, if the limited exposure time guarantees also the prospective touch voltage lower than the safe admissible value (conventional protection), - against direct contact with the supply voltage to ground, as an additional protection (no-guaranteed safe), in spite of using residual current devices RCD up to 30 mA . The paper would highlight as uncovering the protection roots aids improving the safety culture .