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What is the fault rating and momentary withstand capability of HVLCC switchgear

Issue:
What is the fault rating and momentary withstand capability of HVLCC switchgear?

Product Line:
HVL/cc Switch

Environment:
Application

Cause:
Specification

Resolution:
Current ANSI standards for metal-enclosed switchgear and the components are rated individually in
rms symmetrical amperes. The integrated rating may also be expressed this way (the asymmetrical
rating is obtained by multiplying the symmetrical value by 1.6). For convenience when comparing to
older equipment, the integrated rating is also expressed in “MVA.” The MVA ratings are calculated at
the nominal system voltage and with the rms symmetrical amperes, for example, MVA = Nominal
System Voltage, kV x Amperes rms sym kA x √3.
The integrated equipment rating combines the following ratings:
1. Switchgear—momentary and short-time (bus bracing)
2. Load Interrupter Switch—momentary, fault-closing and short-time,
3. Fuses—interrupting and energy let-through characteristics (current-limiting fuses limit the energy
during a short circuit, thereby allowing higher integrated ratings than the switches and switchgear
would have if unfused)
4. Other components that may have limited capabilities.



NOTE: The testing procedures used to establish the symmetrical interrupting rating set the following maximum withstand ratings for the first half cycle associated with each protective device(1) maximum instanttaneous peak let through current (2) maximum single phase rms asymmetrical current at half cycle,and (3) average 3 phase rms asymmetrical current at half cycle.

 
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