UNE-EN IEC 60255-27:2025

This part of the IEC 60255 series describes the product safety requirements for measuring

relays and protection equipment having a rated AC voltage up to 1 000 V, or a rated DC voltage

up to 1 500 V. Above these limits, IEC 60664-1 is applicable for the determination of clearance,

creepage distance and withstand test voltage.

This standard specifies essential safety requirements to minimize the risk of fire and hazards

caused by electric shock or injury to the user and property, and this standard is intended to

describe only product safety requirements, functional performance of the equipment is not

covered.

This standard covers all the ways in which the equipment may be mounted and used in cabinets,

racks and panels. This standard also applies to auxiliary devices such as shunts, series

resistors, transformers, etc., that are used in conjunction with measuring relays and protection

equipment and are tested together.

Ancillary equipment such as network switches used in conjunction with measuring relays and

protection equipment may need to comply with additional safety requirements.

This standard does not specify the implementation of individual equipment, circuits and

components. Equipment shall be designed to meet the requirements of all relevant clauses of

the standard and tested to prove compliance where necessary. Type testing alone (as section

9 type tests) does not form a complete safety assessment and does not guarantee that the

correct components / materials have been used, this can only be achieved by assessment

against all clauses of this standard.

This standard applies to equipment designed to be safe at least under the following

environmental conditions

indoor use;

altitude up to 2 000 m, in accordance with IEC 60255-1;

rated ambient temperature range, in accordance with IEC 60255-1;

maximum external relative humidity, in accordance with IEC 60255-1;

operating range of auxiliary energizing voltage in accordance with IEC 60255-1;

applicable overvoltage category;

applicable pollution degree of the intended environment (pollution degree 2 in most cases).