POWER INFRASTRUCTURE systems without disruption. 600 400 200 0 1 -200 -400 -600 Degrees/Radians 600 400 200 0 1 -200 -400 -600 Degrees/Radians
Figure 4. Top: Waveform characteristic 50hz fundemental. Below: Resultant waveform with fundamental +3rd harmonic.
46 91 136 181 226 271 316 361 46 91 136 181 226 271 316 361
n Battery Failures: Aged, warped, or leaking batteries; missing terminal insulators.
n Hazardous gas: A rotten egg smell may indicate Hydrogen sulfide (H₂S) release– highly toxic and flammable.
n Poor wiring: Misconfigurations reduce safety and performance.
n Lack of fundamental means of isolation of both UPS and its battery
A zero-phase shift transformer is required to maintain a stable neutral-earth reference. It is best installed on the UPS output, though the input or bypass may be suitable in some designs so consult the UPS manufacturer. n Recommendations: 1. Use dual battery systems for resilience. 2. Add thermal monitoring for large installations. 3. Test inverter performance annually. 4. Provide isolation at both UPS and battery ends. 5. Include remote battery trip controls outside the UPS room.
6. Fit fire/smoke dampers on UPS room ventilation. 7. Relay alarms to staff base and estates via BMS.
V1 I1
9. Medical IT systems and N+1 redundancy Medical IT systems provide essential electrical protection in Group 2 medical areas (e.g. theatres, HTU, SCBU), preventing equipment failure during earth faults and protecting patients from leakage currents. These systems use isolation transformers (typically 4–10 kVA, single- phase) without centre-tap earthing. n Key issues: n Absence in some Group 2 areas. n No N+1 resilience. n Shared earth paths. n Lack of alarm integration or visibility.
0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016
n Recommendation: Adopt modular N+1 IPS/UPS designs, verify transformer impedance, and link alarms to BMS for remote visibility to clinical and Estates staff.
V1 I1
0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016
10. Harmonics, power quality and energy monitoring Undetected issues like harmonic resonance and THD can pose serious risks. All new connections must now comply with engineering recommendations (EREC) G5 1920. The ENA guides stipulate THD limits: Voltage ≤5% (LV), ≤3% (HV); Current emissions must comply with planning levels. This waveform capture displays both the voltage and current waveform which indicates a significant presence of 5th & 7th Harmonic distortion typically found on electrical systems with significant element of frequency-controlled motors. The introduction of harmonic rich loads, for example IT loads which generate Triplen (150hz) current, the resultant distortion can be demonstrated with the 500amp 50HZ load and the subsequent distortion by adding 100amps of 3rd Harmonic current as seen in Figure 4. n Recommendation: Install PQ analysers on transformer/ generator incomers with intermediate level analysers on sub-main feeders. Trend harmonic distortion and power factor and use dashboards for threshold monitoring and appropriate pre-settings to detect transient conditions.
Figure 5. Top: Current - voltage waveform with PF connected. Below: Current - voltage waveform with PF disconnected.
62 Health Estate Journal January 2026
11. Power Factor correction Power Factor (PF) correction units were an integral part of every low voltage electrical infrastructure due to the inherent poor power factor on historic
Current
Current
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