UL 67 2019 pdf download – Panelboards.
2.6 The short-circuit current available in the secondary circuit of a transformer rated 10 kilololtamperes or less is considered to be 5000 amperes or less. 2.7 For other than a plug-in meter, a current-sensing meter in a panelboard shall be a type that has been subjected to a 60 hertz rms short-circuit current of 12,000 amperes for four electrical cycles, and a peak current of 30,000 amperes for one-half electrical cycle, and shall be provided with overcurrent protection as described in 25.8.5.2. A plug-in meter such as a watt-hour meter to be plugged into a meter socket base is not considered to be a part of the panelboard. Exception No. 1: A meter need not have been tested nor provided with overcurrent protection if it is intended for use with a current transformer. Exception No.2: A meter need not have been tested nor provided with overcurrent protection if it is used across a shunt that has been subjected to a short-circuit test as specified in Section 25, Shorf-Circuit Current Test. Exception No. 3: A meter need not have been subjected to a peak current of 30,000 amperes nor provided with overcurrent protection if the short-circuit current rating of the panelboard or the available fault current of the circuit at the meter is 14,000 amperes or less. Exception No. 4: The four electrical cycle test may be reduced to 10,000 amperes if the short-circuit current rating of the panelboard is 10,000 amperes or less. 3 Units of Measurement 3.1 Values stated without parentheses are the requirement. Values in parentheses are explanatory or approximate information. 4 Undated References 4.1 Any undated reference to a code or standard appearing in the requirements of this standard shall be interpreted as referring to the latest edition of that code or standard.
5 Glossary 5.1 For the purpose of this standard, the following definitions apply. 5.2 AMBIENT TEMPERATURE – The temperature of the surrounding medium that comes in contact with the panellboard. For an enclosed panelboard, it is the temperature of the medium outside the enclosure. 5.3 AMPACITY – The current in amperes a conductor can carry continuously under the conditions of use without exceeding its temperature rating. 5.4 AVAIL ABLE SHORT-CIRCUIT CURRENT – That current which would flow in a circuit if a short-circuit of negligible impedance were to occur at a given point. 5.5 BARRIER – A partition for the insulation or isolation of electric circuits ar electric arcs. 5.6 BONDING – The permanent joining of metallic parts to form an electrical conductive path that ensures electrical continuity and the capacity to conduct safely any current likely to be imposed. 5.7 BONDING JUMPER – A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected. 5.8 BONDING SCREW- A screw that is used as a bonding jumper. 5.9 BUS – A conductor, or group of conductors, that serves as a common connection for two or more circuits.