Unique SF6 monitoring: Combined mechanical AND electronic monitoring
The Hybrid Gas Density Monitor combines the advantages of the proven mechanical monitor based on the superior reference chamber with the unique electronic gas density sensor. The combined technology has local switches / read-out and allows remote surveillance and trend analysis. The compact all-in-one-device with a single pressure port operates reliably and maintenance-free under harsh conditions indoors and outdoors. It is accurate over a wide range of temperatures and altitudes.
Advantages
- Mechanical switches AND continuous output signal usable for trend analysis (analogue output signal)
- High resistance against vibration and shock
- No bouncing of electrical contacts
- Very high electromagnetic compatibility (EMC) compatible with EN/IEC 61850
- No false alarms at low temperatures
- Maintenance-free, no recalibration of switchpoints
- Facilitates compliance with greenhouse gas regulations mandated by EPA (USA), SGCC (China) or F-Gas Regulation (Europe)
Operating principle of the reference chamber
The gas density of SF6 compartments is compared via a bellows system with the gas density in a reference gas chamber in the monitor. If the density of the gas alters, the bellows system actuates one or more micro switches. If the gas temperature and therefore its pressure changes, the same pressure difference occurs also in the reference chamber. No false alarm is triggered due to temperatureinduced pressure changes. Up to three galvanically isolated micro switches actuate different alarm signals. An optional SF6 indicator provides visual inspection of the SF6 gas density as gas pressure at 20°C.
Operating principle of the electronic gas density sensor
The constant resonant frequency of a quartz oscillator under vacuum is compared with the resonant frequency of an identical quartz situated in the sample gas. The difference in the resonant frequency is proportional to the density of the sample gas. This difference is processed into an analogue output signal.
Technical Data
