ANSI HV & MV Breaker Ratings
ANSI HV & MV Breaker Ratings
(OP)
The Australian Standard for HV circuit-breakers AS 62271.100 is based on the IEC Standard.
The SKM-PTW software breaker library has following ANSI parameters which I do not understand :
- "Rated SC Rating (kA)" - Is this the symmetrical or asymmetrical current at instant of contact parting ?
- "Parting Time (Cyc.)" - Is this the time between receipt of trip signal at the breaker and the first contact parting "?
- "Speed (Cyc.)" - Is this the total clearing time including arcing time ?
The SKM-PTW software breaker library has following ANSI parameters which I do not understand :
- "Rated SC Rating (kA)" - Is this the symmetrical or asymmetrical current at instant of contact parting ?
- "Parting Time (Cyc.)" - Is this the time between receipt of trip signal at the breaker and the first contact parting "?
- "Speed (Cyc.)" - Is this the total clearing time including arcing time ?






RE: ANSI HV & MV Breaker Ratings
But in general:
1. symmetrical (since 1964 or so - definitely if made after 1970)
2. Time from start of fault to contact parting
3. Yes
As with IEC, the ANSI breaker short circuit ratings are complicated. Conrad St. Pierre's "A Practical Guide to Short Circuit Calculations" covers both ANSI and IEC breaker standards in great detail.