UL 2748-2017 pdf download – Arcing Fault Quenching Equipment.
9 Grounding 9.1 There shall be provision for grounding all non-current carrying metal parts of the equipment. In addition, the following parts shall be grounded: a) The metal case of a frame or instrument transformer; b) The metal case of an instrument, meter or relay; or c) The secondary circuit of a current or voltage transformer. 9.2 The case of an instrument, relay, meter, or similar device, if mounted on a grounded metal surface and secured thereto by means of metal screws, is considered to be grounded. 10 Control and Secondary Wiring 10.1 An insulated conductor provided as part of a control circuit or secondary wiring shall be rated for the particular application and shall have an ampacity not less than the continuous current rating of the circuit in which it is connected. Where loads are of an intermittent nature, such as in trip and closing circuits, conductors shall be sized to provide their intended function with respect to voltage drop and mechanical strength. 11 Creepage and Clearance Distance 11 .1 Section 12, Spacings, of the Standard for Metal-Enclosed Low-Voltage Power Circuit Breaker Switchgear, UL 1558 applies to the power circuits of low-voltage quenching equipment, other than as noted in 11.3. 11.2 No minimum creepage or clearance distances are specified for medium-voltage circuits in quenching equipment, other than distances sufficient to meet the dielectric requirements specified in this standard for the voltage rating of the equipment.
11.5 The pollution degree 2 microenvironment specified in 11 .3 need not be maintained during or after the quenching of an arcing fault if servicing of the quenching means is required after an arcing fault event, and the quenching means is marked in accordance with 21.5. 11.6 For printed wiring boards, the creepage and clearance distances shall comply with requirements of the Standard for Insulation Coordination Including Clearance and Creepage Distances for Electrical Equipment, UL 840. For the purpose of determining required creepage and clearance distances, quenching devices shall be considered to be located within circuits of overvoltage category 3. All quenching devices are considered to be installed in pollution degree 3 environments, except for portions of the device located in a pollution degree 2 microenvironment. 11.7 Pollution Degree 2 shall be considered to exist on a printed-wiring board where a coating provides an uninterrupted covering of the conductive material for at least one of two conductive materials and covers the entire space between the two conductive materials for which the spacing is being evaluated. 12 Wiring 1 2.1 Insulated conductors provided as part of a quenching device shall be rated for the particular application and shall have an ampacity no less than the maximum current rating of the circuit to which they are connected. 12.2 Wiring shall be located or protected to prevent contact with any sharp edge or moving part that could damage the insulation. 12.3 Insulated conductors shall be separated from wiring and uninsulated live parts connected to other circuits, unless both circuits are provided with insulation rated for the highest voltage. 13 Operation 13.1 Quenching devices with adjustable sensitivity shall comply with the requirements of this standard over the entire range of possible settings.