IEEE C37.20.1a-2020 pdf free 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.
7.1.3.3 Control, secondary, and logic-level wiring Flame-retardant, 600 V insulated stranded copper wire shall be used for internal wiring between components of switchgear assemblies, and to terminals for connection to external controls, metering, or instrumentation. Wiring within components is assumed to be covered by standards applicable to those devices and is not covered by this standard. Wiring for the purpose of conveying power to external switchgear loads is not covered by this clause. The switchgear manufacturer is responsible for the performance of the wiring system provided by the manufacturer within the switchgear. This applies to the integrity of internally generated signals in the control wiring, and may require the use of special precautions such as shielded wire, twisted-pair wire, or segregation of certain wires. For LV dc switchgear, wiring used to connect instrument, meters, and relays directly on circuits up to 3200 V, and any wiring connected directly to higher voltage circuits in LV dc switchgear rated up to 3200 V, shall use wire rated for the maximum design voltage of the switchgear.
7.1.3.3.1 Wiring across a hinge Wiring that crosses a hinge shall be suitable for this use, as defined by all of the following criteria:
a) Wire shall be sized according to 7.1.3.3.2.
b) Single conductors shall be stranded wire.
c) Wire shall be sufficiently flexible to withstand repeated door movement without sustaining damage to wire strands or insulation.
d) The loop formed by the wiring as it crosses the hinge shall be secured to the equipment at both ends, in such a manner that negligible strain is transmitted to wire beyond the securements to prevent damage to the wire insulation as the door is moved.
e) Wiring shall not prevent the door from opening to the intended maximum opening, with a minimum opening of 90 degrees.
f) The wire loop is to be protected between the securements to provide a degree of protection against damage to the wire insulation as the door is moved.
g) No sharp edges or objects are allowed in the path swept by the wire loop as the door is operated.
h) If the wire is No. 14 AWG or larger wire, the wire shall be no less flexible than
Class C or D stranding.
7.1.3.3.2 Wire size Wire shall be suitable for the anticipated maximum steady-state load. The size chosen shall also accommodate voltage drop within the switchgear, including the effect of intermittent heavy loads (shunt trip coils, inrush from relays, and the like). The following criteria shall be used as minimums:
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).IEEE C37.20.1a pdf download.