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ANNED SF6 Gas Density Monitor Features

Special solutions to meet the highest demands for operational safety and reliability have been developed by ANNED for the power generation, transmission, and distributor sectors.  ANNED has specially developed temperature-compensated pressure gauges for use in switchgears that ensure safe operation of SF6 gas-insulated equipment.  Because of its exceptional properties, sulphur hexafluoride (SF6) is used as an insulating, quenching, and cooling gas in manifold applications.  Main applications for SF6 gas in electrical engineering are:

  • high-voltage air-insulated substations (AIS)
    - life tank breakers
    - dead tank breakers
  • high-voltage gas-insulated substations (GIS)
  • gas-insulated high-voltage cables
  • instrument transformers
  • transformers

Normal pressure gauges are not suitable for this monitoring operation because with the same gas density, the gas pressure is dependent on the gas temperature in closed gas systems.  This dependency is is specific to the used gas and is shown in a vapor pressure diagram with lines of identical density, the so-called isochores.  Therefore the temperature must also be registered by suitable monitoring systems working on the pressure measuring principle.  This enables the monitoring unit to correct the measured pressure value according to the isochores.  Such special pressure gauges/transmitters are the gas density monitors as described herein.

ANNED produces mechanical SF6 gas density monitors which is identical to the specs of SF6 gas density monitors from WIKA in a variety of versions.

Gas Density Monitors with Local Indicator and Alarm Contacts
Gas density monitors with local indicator and alarm contacts combine the indicator and switching function.  Each gas density monitor is adjusted individually to its calibration pressure.  In order to define the bimetal compensation exactly, ANNED uses a computer-controlled adjustment equipment to make the job precisely.  Apart from considering the calibration pressure, this equipment also takes into account different factors influencing the instrument.  For example, the Bourdon tube and the characteristic data of the bimetal used for temperature compensation.  The class accuracy is ±2.5% within the temperature range -40°C...60°C.  The switching accuracy is ±2.5%.  The information concerning the switching accuracy refers to the calibration pressure.  For further information, please refer to the e-catalog, which can be downloaded at SF6 Home.