IEC 61892-1 contains provisions for electrical installations in mobile and fixed offshore units including pipeline, pumping or 'pigging' stations, compressor stations and exposed location single buoy moorings, used in the offshore petroleum industry for drilling, processing and storage purposes. This International Standard applies to all installations, whether permanent, temporary, transportable or hand-held, to AC installations up to and including 35 000 V and DC installations up to and including 1 500 V (AC and DC voltages are nominal values). This standard does not apply either to fixed equipment for medical purposes or to the electrical installations of tankers. This edition includes the following significant technical changes with respect to the previous edition: a) The general requirement to harmonic distortion has been changed from IEC 61000-2-4 Class 2 to Class 1. b) The voltage tolerance for a DC system has been changed from +-10 % to +10 %, -15 %. c) Annex C (informative) regarding specification of surface treatment and protective painting system has been added.