Background
An office building experienced repeated failures of lift control panel power supplies with several incidents resulting in burnt components. Notably, most failures occurred during night-time hours when building load was lower. ENERSIS was engaged to investigate the root cause and assess the quality of the electrical supply.
Initial Power Logging Assessment
The investigation began with a power logging exercise at the lift incoming panel. Voltage measurements revealed that the supply voltage was consistently high, operating close to the upper limit of the allowable range (approximately 400 V +10%). Even higher voltage levels were observed after office hours coinciding with periods of reduced load. The continuous high voltage was likely stressing the electronic components leading to repeated failures and eventual burnout of the lift panel power supplies.
The findings were documented and presented to the building management for review.
Extended Power Quality Investigation
To determine whether the elevated voltage originated from the utility supply or the building’s internal electrical system, ENERSIS was subsequently engaged to conduct a detailed power quality assessment. Power Quality Analyzers were installed at both the Medium Voltage (MV) incoming panel and the Low Voltage (LV) Main Switchboard (MSB).
The results showed that:
The MV incoming voltage from the utility supply remained compliant with relevant standards.
The LV MSB voltage levels were consistently near the upper threshold aligning with the earlier lift panel measurements.
These findings indicated that the high voltage condition was introduced downstream of the MV supply, most likely within the internal transformer configuration.
Conclusion and Recommendation
Based on the measured data and analysis, ENERSIS concluded that the elevated LV voltage was the likely contributor to the repeated lift panel power supply failures. A recommendation was submitted to the management to carry out a transformer tapping adjustment to bring the LV voltage back within an optimal operating range.
Outcome
This case highlights the importance of targeted power logging and multi-point power quality measurements in identifying the true source of electrical issues.
Malaysia
