SF6 Leak Testing
Photoacoustic SF6 Leak Detectors are market-leading instruments to perform integral leak testing on gas-insulated switchgear and to check compliance against international standards.
With the global trend moving toward more high-voltage and ultra-high-voltage infrastructures in the Transmission and Distribution industry, more and more SF6 gas-insulated switchgears (GIS) are being used.
Since SF6 is the most potent greenhouse gas with an extremely high global warming potential, emission standards are being enforced by regulating authorities. At the same time, no viable alternative to SF6 exists in the short term for the power industry, so stakeholders have been proactive and set in place voluntary action plans to define more stringent emission standards for the design, manufacturing, and operation of SF6 GIS.
Highly sensitive gas monitors have become necessary components of integral leak tests, which are required to verify the conformity of switchgears with the low permissible leakage rates as defined in those international standards, and to enable self declarations by OEMs.
These integral leak tests, also known as cumulative sealing tests or tightness tests, are the preferred test method for type testing of medium-voltage and high-voltage GIS according to the IEC 62271-1.
Some GIS manufacturers have chosen to use integral leak tests, not only for type testing, but also for their routine testing in order to reduce their overall manufacturing cycle time.
To meet this short cycle objective, while also meeting the low SF6 leakage rates defined by industry standards, a highly sensitive, stable, and accurate gas analyzer is needed in the ppb to sub-ppm range.
Based upon state-of-the-art photoacoustic IR spectroscopy (PAS), the INNOVA 1512 has a low detection limit of 6 ppb. The gas samples are drawn directly from the test chamber and are automatically compensated for spectroscopic interference from water vapor IR absorption, as well as the pressure and temperature effects.
Where applicable, the SF6 leak detector can be bundled with an INNOVA 1409 Multipoint Sampler enabling either the parallel monitoring of multiple test chambers from a unique PAS analyzer, or enabling the sampling from multiple locations in a unique chamber.
The LumaSoft 7820 (single channel) or 7880 (multiple channel) application software completes the system with user-friendly graphical interfaces to setup and supervise the leak monitor. Finally, the design of the PAS sensing platform offers great analytical flexibility: the simple addition of optical filters make it possible to measure alternative gas or insulating gas mixtures.
Within a test cycle of 30 to 45 minutes, the SF6 concentration will not increase more than a few tens of ppb. The INNOVA 1512 is accurate enough to measure true quantitative values at this low detection limit. It leverages the photoacoustic technique to feature a strong accuracy and linearity over a high dynamic range (minimum 4 decades with a 1-point span calibration). As a result, the test procedure can be applied with the same efficiency and quality on the results as long as the “zero” offset (initial background concentration) is properly measured.
Operational advantages: fast and reliable integral leakage monitoring
Minimal operation & maintenance costs: no consumable, “zero” calibration
Easily expandable to other / additional gas(es) by selecting a different optical filter
- Best-in-class quantitative leak detection method in a reference document of the industry: the SF6 Tightness Guide issued by CIGRE
- Highly selective measurement of SF6 with minimal cross-interferences
Schematic of the SF6 multipoint monitoring solution: A local computer (or remote computer) is connected to the SF6 Gas Monitor, it synchronizes the monitoring and the sampling devices. The same application software operates on either of the computers which enable online supervision with the OPC interface allowing remote access to the same data. The two (2) Alarm relays can be connected to a local warning device (bell, buzzer, or alarm light) or be connected to a local RTU device for remote alarm signals.