IEEE Std C37.20.1a-2020 pdf download – IEEE Standard for Metal-Enclosed Low-Voltage (1000 V ac and below, 3200 V dc and below) Power Circuit Breaker Switchgear Amendment 1: Control and Secondary Circuits and Devices, and All Wiring.
EXCEPTION: Multiple-conductor cable (two or more insulated wires inside a common insulated jacket) used in logic-level and/or supervisory circuits may use wire sized as required by the circuit. Wiring for control loads over 40 A shall be applied using ampacities from the 75 °C column of Table 310.15(B)(16) (formerly Table 310.16) in the National Electric Code ® (NEC ® )(NFPA 70). Wiring for current transformer and shunt trip circuits shall be no less than No. 14 AWG, regardless of load. Thermocouple wiring is specifically excluded from the above ampacity requirements. It shall meet the voltage, current, and temperature requirements of the circuit in which it is used and the location where it is installed. When required for connection to a specific component, low-energy signaling, and communication wiring is specifically excluded from the above ampacity requirements. The wire shall meet the voltage, current, and temperature requirements of the circuit in which it is used and the location where it is installed. Wire connected directly to the main power circuit of the dc traction power switchgear bus system shall be at least No. 14 AWG. NOTE—Where long connections to the control source are necessary, the cable must be large enough to prevent excessive voltage drop.
7.1.3.3.3 Wire protection and support Bushings, grommets, or other mechanical protection shall be provided for wiring where it passes through a metal sheet, barrier, or raceway. Wiring shall be adequately supported to prevent stress from causing damage of any kind to the conductors or the insulation. Wiring for circuits operating at different voltages shall be separated unless all wiring is insulated for the highest operating voltage of all the circuits intended to be bundled or closely grouped. Except for wires connected directly to the main power circuit, wiring shall be adequately supported to prevent contact with the switchgear bus system. 7.1.3.3.4 Wire type Wiring shall be rated for 600 V, 90 °C, be flame-retardant, and shall meet the requirements of NEMA WC70 / ICEA S-95-658. Preferred wire is type SIS as listed in NFPA 70 (NEC ® ) or an equivalent such as XHHW, RFHH-2, RFHH-3, or the like. Other wires that meet the requirements of this clause are also acceptable. Wiring used for connection directly on circuits above 600 V shall be rated for the voltage involved (or higher), 90 °C, and shall be flame-retardant.