Continuous humidity measurement in gas-insulated switchgear

by T Jung, WIKA

 

Published in: Transformers and Substations Handbook: 2014

Chapter 4: Maintenance - page 72

Enquiries: Wika Instruments South Africa. Tel. 011 621 0000 or email sales@wika.co.za

 

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Switchgear within power transmission systems has a service life of over 30 years. To guarantee lasting operational safety over such a time span represents a major challenge. For the network operators and equipment manufacturers, the topics of smart grid and online monitoring are therefore gaining more and more importance. Particularly in the area of gas-insulated switchgear within power transmission systems, the interest in continuous and digital monitoring has risen strongly. Here, attention is turning to the loss rate as well as the humidity content of the sulphur hexafluoride (SF6) used. If the critical phases of both parameters are not identified in good time, the operational safety can be compromised.

So that SF6-filled equipment is always optimally insulated, its gas content must be monitored permanently. For this, in most cases, the operators use mechanical gas density monitors with switching functions. When the SF6 volume has dropped to a particular level, the measuring instrument sends an alarm signal and automatically shuts down the equipment using a second contact.

The round-the-clock monitoring also has an ecological basis: The specific global warming potential of SF6 is 22 000 to 24 000 greater than that of CO2. The F-gas regulation limits, or even prohibits, the use of the gas in most applications. However, the power industry cannot operate without SF6 due to its phenomenal insulation properties. The European switchgear manufacturers have therefore signed a voluntary commitment. Within it are defined limit values for leak rates for the systems, which are binding and must be documented.

 

Take note

  • In the area of Gas-insulated Switchgear (GIS), the interest in continuous and digital monitoring has risen.
  • So that SF6-filled equipment is always optimally insulated, its gas content must be monitored permanently.
  • The round-the-clock monitoring also has an ecological basis.