IEC 60079-15-2017 pdf free.Explosive atmospheres – Part 15: Equipment protection by type of protection “n”.
In normal operation and in certain regular expected occurrences specified by this standard, the equipment shall not:
a) produce an operational arc or spark unless that arc or spark is prevented from causing ignition of a surrounding explosive atmosphere by one of the methods described in Clauses 7 to 10;
b) develop a maximum surface temperature in excess of the maximum value appropriate to the temperature class of the equipment, unless the temperature of the surface or hot spot is prevented from causing ignition of a surrounding explosive atmosphere by one of the methods described in Clauses 7 to 10 as appropriate, or is otherwise shown to be safe as specified in 5.
4.3 Equipment requirements
Equipment or components which in normal operation produce arcs, sparks or hot surfaces which otherwise would be capable of igniting a surrounding atmosphere shall be protected against causing ignition by one or more of the following methods, all of which provide Equipment Protection Level Gc:
a) non-incendive component (see Clause 7);
b) hermetically sealed device (see Clause 8);
C) sealed device (see Clause 9);
d) restricted-breathing enclosure (see Clause 10).
5 Maximum surface temperatures
The maximum surface temperature shall be determined in accordance with the determination of maximum temperature classification requirements of IEC 60079-0. The surface to be considered shall be the external surface of the equipment including the surface of internal parts of non-incendive components to which the explosive gas atmosphere has access.
6.1 General
Electrical equipment with type of protection “n” shall comply with the requirements of this standard and the applicable parts of IEC 60079-0 for the method(s) of protection used.
6.2 Electric strength insulation from earth or frame
Where the electrical circuits within the equipment are not connected directly to the frame of the equipment or not intended to be connected to the frame in service, the insulation or separation distance used shall withstand without breakdown one of the following tests:
a) either as given in a relevant industrial standard for the individual items of electrical equipment; or
b) if no such test requirement exists, at the test voltage according to 1), or 2) below, and maintained for at least 1 mm without dielectric breakdown occurring.
1) for equipment supplied with voltages not exceeding 90 V peak or in which internal voltages not exceeding 90 V peak are present, 500 V r.m.s,
2) for other equipment, or where internal voltages in excess of 90 V peak are present, (2U + 1 000 V) r.m.s, % or 1 500 V r.m.s. %, whichever is the greater.
The use of a DC test voltage is allowed as an alternative to the specified AC test voltage and shall be 170 % of the specified AC r.m.s test voltage for insulated windings or 140 % of the specified AC r.m.s test voltage for situations where air or creepage distance is the insulating medium.
NOTE U is the higher of either the rated supply voltage or the maximum voltage occurring within the equipment.
For equipment with galvanically isolated parts, the test voltages shall be applied separately, at the appropriate voltage, to each part.IEC 60079-15 pdf download.