In-Service Testing and Diagnosis of Gapless Metal Oxide Surge Arresters According to IEC60099-5
Title 2 2 Overview of presentation • Motivation for condition monitoring of metal oxide surge arresters (MOSA) • “The Surge arrester life” • Service experience • Examples of arrester failures • Characteristic properties of MOSA (ZnO)- arrester • Aging and causes of failure • Consequences of failure – transformer failures
Title 3 3 Overview of presentation contd. • Surge arrester condition assessment • IEC 60099- 5 about “Diagnostic indicators of metal oxide surge arresters in service” • Monitoring equipment and field application for third harmonic analysis with compensation • Testing strategy and risk assessment • Case studies
Title 4 4 Background and Motivation • The Metal Oxide Surge Arrester (MOSA) is a cheap and passive component, but protecting crucial apparatus. • Overlooked despite severe consequences if it fails. • MOSAs can age and fail due for a number of different reasons. • May offer inadequate overvoltage protection, especially if the rated voltage is selected too low. • Diagnostic indicator: Resistive leakage current increases with time increasing risk for failure.
Title 5 5 Power System Overview – Typical Location of Surge Arresters Typical location of surge arresters: In substations At the end of transmission lines At cable ends At transformers, generators, capacitors etc Location depending on voltage level, equipment and local conditions
Title 6 6 The Surge Arrester Life The normal destiny of the surge arrester is to be: specified, purchased, installed - and forgotten… Most common maintenance practice: No testing of surge arresters – Only replacement after breakdown. “surge arresters are inexpensive no big deal to replace !!!” Is this really an acceptable practice?