Electricity and Control December 2023

COVER ARTICLE

Proactive maintenance of transformers ensures power supply

T ransformers, a cornerstone of electrical power systems since the inception of modern grid technology in the early 20th century, represent a substantial investment in these systems. The focus has consistently been on minimising life cycle costs to ensure the reliability and longevity of transformers. To achieve this goal, it is crucial to monitor operating conditions, insulation systems, and accessory components systematically, aiming to extend transformer life and reduce associated costs. The identification and characterisation of faults and defects throughout the life cycle are essential to advance predictive techniques to minimise disruptions in the electric power supply system. The significance of power transformers in ensuring a continuous power supply underscores the need to address failures promptly, given the substantial financial and time investments required for replacements. In response to these challenges, there has been significant progress in research and development of advanced technologies and predictive maintenance techniques. Numerous studies emphasise the optimisation of maintenance processes and diagnostics for substation equipment like transformers. However, the dilemma faced by many, particularly in sub-Saharan African nations and countries such as Brazil and India, revolves around the decision to replace or maintain aging units. Proactive planning is crucial to managing stoppages effectively and making informed decisions. The objective is to prevent unplanned interruptions, ensuring uninterrupted electricity supply to critical facilities, large businesses, infrastructure, and domestic users. The term ‘stoppage’ signifies the interruption of equipment service due to defects or faults, and power transformers are particularly critical components, especially in regions where the transformers are nearing the end of their operational life. In response to the increasing pressure to reduce costs,

ArmCoil developed the On-Site Condition Analysis (OSCA) service a few years ago. Leveraging its extensive experience in transformer repairs and manufacturing across South Africa and beyond, ArmCoil aims to provide cost-effective solutions to optimise transformer performance throughout the equipment’s life cycle. The OSCA service encompasses three phases. Phase 1: Equipment assessment and identification Using non-intrusive methods, this phase involves visual inspections and oil sampling to gauge the overall health status of the transformer. The collected information helps map out substation locations, enabling prioritisation of transformers for service based on the criticality of their condition. Some oil sampling methods available are: - Dissolved Gas Analysis (DGA) – evaluating oil health and indicating possible internal faults - Breakdown Voltage Test – assessing the insulating properties of the oil - PCB Content – addressing health and environmental concerns related to polychlorinated biphenyls - Acidity Content Test – measuring acidity increase over time - Moisture Content Test – checking contamination through interaction between air and transformer oil - Furanic Testing – determining paper deterioration in the transformer. After prioritising assets from Phase 1, the OSCA service costs can be further reduced by targeting specific components or the entire asset over a period thereby increasing life expectancy. The goal is to minimise risk and increase availability. As one example, when an aged transformer is at risk of imminent failure, ArmCoil may provide a ‘drop-in replacement’ unit during the next maintenance shutdown to minimise downtime. Phase 3: Extended life cycle and reporting This phase demonstrates the extension or improvement of an aged transformer’s life cycle. Reports obtained during the on-site condition analysis indicate the reliability of assets and the exclusive service events provided by ArmCoil. Quarterly or annual recommendations for monitoring, oil sampling, and parts/asset replacement are proposed strategically, to reduce routine inspection expenditure and extend operational life expectancy. □ Phase 2: On-site condition analysis service implementation

Transformers constitute a critical component of electrical power systems.

For more information visit: www.armcoilafrika.co.za

DECEMBER 2023 Electricity + Control

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