IEEE C37.20.2a-2020 pdf free download – IEEE Standard for Metal-Clad Switchgear Amendment 1: Control and Secondary Circuits and Devices, and All Wiring.
Overcurrent protection of current transformer secondary circuits shall not be provided. Open circuit protection should be considered where current transformer wiring connects to devices external to the switchgear assembly.
Primary and secondary protective devices may be omitted from voltage-dividing devices such as capacitive and resistive voltage dividers.
7.3.2 Voltage transformer fusing The following requirements shall be met:
a) Primary circuits of all voltage transformers shall include current-limiting fuses.
b) Secondary circuits of all voltage transformers shall include fuses or their equivalent. EXCEPTION: Fuses may be omitted from secondary circuits of voltage transformers if the secondary burden includes voltage regulators, protective relays, or other devices considered sufficiently essential to the operation of the installation to make it preferable to incur the hazards associated with the possible destruction of the voltage transformer by a sustained secondary short-circuit rather than to risk interruption of the voltage supply to such devices as a result of a momentary secondary short-circuit. 7.3.3 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.
7.3.3.1 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 7.3.3.2.
b) Single conductors shall be stranded wire.IEEE C37.20.2a pdf download.