IEC 60519-1 -2020 Safety in installations for electroheating and electromagnetic processing – Part 1: General requirements.
4 Classification and subdivision of equipment and installations
4.1 Classification by processing frequency
EH and EPM installation and equipment is classified by its processing frequency. Table 1 lists the equipment types and their processing frequency ranges as well as salety relevant frequency imits. An EH or EPM installation may include more than one type of EH or EPM equipment.
4.2  Classification by voltage
The supply voltage of an installation or equipment is classified as extra low voltage (ELV) below 50 V (RMS) at mains frequency or 120 V direct current, low voltage (LV) between 50 V (RMS) at mains frequency or 120 V direct current and 1 000 V (RMS) at mains frequency or 1 500 V direct current, and high voltage (HV) above 1 000 V (RMS) at mains frequency or 1 500 V direct current.
NOTE The definitions of ELV and voltage band 1, LV and voltage band 2 and HV and voltage band 3 are identical. Voltages below 25 V mains frequency or 60 V direct current are seen as without risk for any ordinary person in most circumstances (exception is possible in wet conditions).
This distinction shall be made for the installation and for parts as defined in 4.3.1 and
a) depending on the supply and the output voltage, whichever is the higher value (internal voltages inside the electrical equipment may be higher), but
b) not depending on the process voltage or internal voltage of the installation or equipment. Different parts of one installation may be classified as ELV, LV or HV.
4.3 Subdivision of installation and equipment
4.3.1 Subdivision into parts
An EH or EPM installation consists of diverse and specific parts. Figure 1 presents a block diagram of a typical installation for reference. It determines the boundary of installations and equipment. Not all parts are found in every kind of an EH or EPM installation.
Table 2 provides references to clauses of this document or to other standards relevant to the parts identified in Figure 1. The requirements for equipment outside the processing equipment are covered by IEC or ISO standards specified in Table 2. The basic sources of safety provisions for electrical equipment of EH or EPM installations and equipment are
IEC 60204-1 for LV and IEC 60204-11 for HV.
The safety requirements for the processing equipment itself are specific because of its extraordinary environment and of conditions inside or near, where
a) extreme temperatures can interact with the equipment,
b) strong electric, magnetic or electromagnetic fields can interact with the equipment, and
c) thermal energy or electromagnetic forces can endanger the structural integrity of the equipment or of insulation and of protective means.IEC 60519-1 pdf download.