Increasingly, the Industry is having to deal with the consequences of performance drivers seeking both high reliability levels and the minimization of outage times. In the case of power transformers, best practice currently is initially to take an oil or Buchholz gas sample and send it to a laboratory for dissolved gas analysis and reporting.
The move toward an exemplary Industry-driven stewardship of SF6 gas in the power industry is a major concern to the Industry internationally, especially as greenhouse gas issues have rapidly elevated in public awareness over the past year. Although only responsible for managing some 1.5% of the world’s SF6 gas resource, the power industry cannot operate without this gas. Other uses of the gas (such as blanketing magnesium and aluminium castings) have been widely noted for wastage and caused already an unbelievable level of environmental damage which the power industry is racing to distance itself from.
Ergon Energy in Queensland is committed to environmental responsibility in serving its customers and the community. As operator of Australia’s largest and most diverse electricity distribution network infrastructure, Ergon has an international ISO 14001 environmental certification and has been a signatory to the Australian Greenhouse Challenge since 1997. Aware of the major potential greenhouse impact following any losses of the switchgear insulant gas, SF6, Ergon Energy have long-established gas management practices that seek to minimise and track and loses of the gas. Such initiatives pre-date much of the SF6 gas tightness and handling initiatives from the European sector of the Industry, only now being finalised as Cigre Guidelines under Committee B3 AA2 WG18.
Dissolved gas analysis (DGA) is widely used to monitor the condition of transformers and other pieces of oil-filled equipment in service. Wrong diagnoses may be drawn, however, if the DGA results coming from the lab are not accurate. For instance, an electrical fault may be mistaken as a thermal fault, which may have serious consequences for the equipment. Several CIGRE and IEC round robin tests (RRTs) have shown that the repeatability (precision) of DGA labs is generally good, but that their accuracy (deviation from true value) is often poor.
LTC position monitors are IEDs that are used for monitoring a transformer’s tap position and changing it remotely based on fluctuations in the power load. The device converts the output of an electromagnetic position or displacement sensor (synchro transmitter) to a user-definable panel display and electrical output. The INCON Model 1250 for example employs a proprietary synchro conversion technique that is performed entirely in preprogrammed software. This approach uses few electrical components, thus ensuring a more stable and reliable output at a very reasonable cost.
From a number of perspectives the active devices in an electric power delivery system, the circuit breakers, can be characterized as the weakest links in the network, as opposed to the passive components such as lines and transformers. That said, the unerring action of switching devices is critical to power delivery quality and reliability.