UFC 3 -520-01
June 10, 2002
interior electrical systems. For purposes of this manual, high voltage refe rs to any
application rated above 15 kV.
MEDIUM VOLTAGE SWITCHGEAR .
5-4.1.1 Switchgear. Use metal-enclosed, manually operated, fusible load interrupter
switches or power circuit breakers with copper bus . Table 5 -1 indicates the most
commonly used voltages; the standard voltages shown without parentheses are
Table 5-1. Medium Voltage Switchgear Voltage Ratings
Nominal System Voltages
7.2 kV and under (in kV)
15-kV class (in kV)
5-4.1.2 Standards. Apply ratings conforming to ANSI C37.06, Preferred Ratings and
Related Required Capabilities for AC High-Voltage Circuit Breakers Rated on a
Symmetrical Current Basis, and ANSI/IEEE C37.04, American National Standard Rating
Structure for AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis,
in the selection of circuit breakers.
5-4.1.3 Voltage Rating. Determine the voltage rating in terms of three-phase, line -
to-line voltage, including the following considerations:
5-18.104.22.168 Maximum nominal system voltage for which the breaker is intended.
5-22.214.171.124 Maximum operating voltage at which the breaker will be used, taking into
consideration line voltage regulation, machine over -excitation and overspeed, and shunt