IEC 60255-5 pdf download.Insulation coordination for measuring relays and protection equipment – Requirements and tests
1 Scope and object
This part of IEC 60255 gives general requirements for the insulation coordination of measuring relays and protection equipment. NOTE 1 Unless otherwise stated, the term “relay(s)” is used as an abbreviation for the expression “measuring relays and protection equipment” in this standard. In particular, this standard, specifies the following: – definition of terms; – guidance for the selection of clearances and creepage distances and other aspects related to the insulation of measuring relays and protection equipment; – requirements for voltage tests and insulation resistance measurement. This standard is applicable to the installation and use at altitudes up to 2 000 m of equipment having a rated a.c. voltage up to 1 000 V, with a rated frequency up to 65 Hz, or a d.c. voltage up to 1 500 V. This standard also applies to associated auxiliary devices such as shunts, series resistors, transformers, etc., used and tested together with measuring relays and protection equipment as mentioned above, except where the devices are covered by other IEC publications, for example communication interfaces. NOTE 2 Requirements for altitudes exceeding 2 000 m can be derived from table B.1 .
For the purpose of this part of IEC 60255, the following definitions together with those of IEC 60050(448), IEC 60664-1 and the relevant parts of IEC 60255 apply. 3.1 hazardous live part part at a voltage in excess of 50 V r.m.s. or 75 V d.c. 3.2 exposed conductive part conductive part which can be readily touched and is normally not hazardous live but may be at hazardous live voltage under a single fault condition NOTE 1 For relays which are not enclosed, the frame, the fixing devices, etc., form the exposed conductive parts. NOTE 2 For relays which are enclosed, the conductive parts which are accessible when the relay is mounted in its normal position of use, including those of its fixing surface, form the exposed conductive parts. Small parts such as inscription plates, screws and rivets which are isolated from the circuits are not taken into consideration. 3.3 clearance shortest distance in air between two conductive parts [IEC 60664-1 ] 3.4 solid insulation solid insulating material interposed between any two conductive parts [IEC 60664-1 ]3.5 creepage distance shortest distance along the surface of the insulating material between two conductive parts [IEV 1 51 -03-37] 3.6 rated voltage value of voltage assigned by the manufacturer to a component, device or equipment and to which operation and performance characteristics are referred [IEC 60664-1 ] 3.7 rated insulation voltage r.m.s. withstand voltage value assigned by the manufacturer to the relay or to a part of it, characterising the specified (long term) withstand capability of its insulation and to which dielectric tests and creepage distances are referred NOTE The rated insulation voltage is not necessarily equal to the rated voltage of equipment which is primarily related to functional performance. 3.8 rated impulse voltage impulse withstand voltage value assigned by the manufacturer to the relay or to a part of it, characterising the specified withstand capability of its insulation against transient over- voltages and to which clearances are referred 3.9 overvoltage any voltage having a peak value exceeding the corresponding peak value of the maximum steady-state voltage at normal operating conditions [IEC 60664-1 ] 3.1 0 overvoltage category numeral defining a transient overvoltage condition [IEC 60664-1 ] NOTE Overvoltage categories I, II, III, IV are used, see 126.96.36.199 . 3.1 1 macro-environment environment of the room or other location in which the relay is installed or used [IEC 60664-1 ] 3.1 2 micro-environment immediate environment of the insulation which particularly influences the dimensioning of the creepage distances [IEC 60664-1 ]