How many hours or days of autonomy should I specify?
It is set by criticality and restoration time, not by convention, but Australian specifications give real benchmarks worth quoting:
|
Application |
Published requirement |
|---|---|
|
Rail, active level crossing |
48 hours with 10% residual capacity (ARTC ESC-03-01) |
|
Substation DC, system black duty |
10 hours (AusNet AMS 20-80) |
|
Mobile base station, hardened |
At least 12 hours (Commonwealth Mobile Network Hardening Program) |
|
Traffic signals / ITS roadside |
4 hours at full load (TMR MRTS213; NZTA 1–8 h site-determined) |
|
HV water utility installation |
4 hours minimum (Sydney Water DOC0008) |
|
Stand-alone power system |
2 days with auto generator, 4–5 days without (AS/NZS 4509.2) |
Nobody else has these numbers assembled in one place, and each maps to a Valen product line.