Analogue Protection, Digital Insight: keeping transformer protection simple while feeding information to the monitoring system

As substations go digital, more transformer protection and control functions are moving from analogue devices to electronic and software-driven devices. For the alarm and trip decisions that protect the asset, simple self-powered instruments remain hard to beat. They need no auxiliary supply, firmware or network to act. This talk shows how temperature indicators, Buchholz relays, pressure relief devices, oil level indicators and dehydrating breathers can keep proven mechanical protection while sending 4–20 mA or SCADA-ready data to monitoring and asset-management systems. It ends with five questions specifiers should ask. Aruna Janardhanan leads Precimeasure, which has made transformer protection and monitoring instruments since 1984.