This part of IEC 60664 deals with insulation coordination for equipment having a rated voltage up to AC 1 000 V or a rated voltage up to DC 1 500 V connected to low voltage supply systems. This document applies to frequencies up to 30 kHz. NOTE 1 Insulation coordination for equipment within low-voltage supply systems with rated frequencies above 30 kHz is given in IEC 60664-4. NOTE 2 Higher voltages can exist in internal circuits of the equipment. It applies to equipment for use up to 2 000 m above sea level, and provides guidance for use at higher altitudes. It provides requirements for technical committees to determine clearances, creepage distances and criteria for solid insulation. It includes methods of electric testing with respect to insulation coordination. The minimum clearances specified in this document do not apply where ionized gases are present. Special requirements for such situations can be specified at the discretion of the relevant technical committee. This document does not deal with distances: through liquid insulation; through gases other than air; through compressed air. This basic safety publication is primarily intended for use by technical committees in the preparation of standards in accordance with the principles laid down in IEC Guide 104 and lSO/lEC Guide 51. It is not intended for use by manufacturers or certification bodies. One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. The requirements, test methods or test conditions of this basic safety publication will not apply unless specifically referred to or included in the relevant publications. However, in case of missing specified values for clearances, creepage distances and requirements for solid insulation in the relevant product standards, or even missing standards, this document can be used.