In May 2021, a 12-channel BMS was installed on a step-up transformer at a large Imperial County, CA solar installation (using 6 C1 test taps, 3 low-side PTs, and 3 high-side CCVTs for robust phasor measurements).

ZTZ’s Technical Expertise

ZTZ’s ZVCM-1001 active bushing monitoring system flagged the H1 high-side bushing as “unstable” (power factor at ~3x nameplate), classifying it beyond “watch list” status despite heavy “rough service” loads. Our analysis of stable capacitance and imbalance currents suggested the defect existed since commissioning (undetected by offline tests), guiding a nighttime bushing swap to avoid revenue loss (estimated 10x transformer value).

Active Monitoring Results

Within days, PF plots showed H1 at ~0.9% (vs. H2/H3 at ~0.3% nameplate; see 3-month high-side PF chart). Imbalance currents and C1 were stable, isolating the issue. Replacement in August confirmed high PF via offline tests, with no incident—highlighting the BMS’s high signal-to-noise ratio for early intervention.