This reports how many modules in this AC group have genuinely failed, the group-scoped equivalent of tsiPhaseNbModKO, useful for spotting whether failures cluster within modules sharing a specific AC circuit rather than being independently distributed across the site. A concentration of failures within one AC group, rather than spread evenly, points toward a problem with that specific circuit's feed quality, a voltage sag or surge on that particular feed, rather than coincidental individual module defects. An admin seeing this count elevated in only one AC group, with other groups reporting near-zero failures, would investigate that group's specific AC feed quality rather than assume a general fleet-wide module reliability issue.