SF6 Leak Detection System - 3731

Detecting and quantifying Sulfur Hexafluoride (SF6) leakages in the T&D and Power industry

The SF6 Leak Detection products from LumaSense offer an unmatched combination of performance and convenience. Based on the company’s Photoacoustic Spectroscopy (PAS) technology, they offer highly accurate, repeatable, and reliable quantitative gas analysis and detection. The growing environmental requirements and pressures regarding the use of SF6 make LumaSense’s leak monitors a coveted tool designed for routine testing or continuous monitoring at minimal costs.

SF6 Leak Detection System - 3731
SF6 Leak Detection System - 3731

Application Area

  • Leak detection for enclosed Gas-Insulated Switchgear (GIS) substation
  • Leak detection on SF6 distribution and handling circuits in manufacturing facilities

Key features

  • Stationary standalone multipoint monitoring for direct leak detection in large enclosed volume
  • Ultra-sensitive, with a limit of detection at 6ppb
  • Available in 12 or 24 channels, with sampling lines that can extend to 75m.
  • High reliability with self-test routines
  • Low maintenance need, calibration only required once a year
  • Analog output for detection trending, and 12 configurable zone alarm relays
  • Measurements stored in internal memory, with easy export to remote PC via user-friendly software


Leak Detection for Enclosed GIS substations

New regulatory frames, like the F-Gas Directive (EC 517/2014), are mandating the use of leak detection systems in the vast majority of high-voltage SF6-GIS installation in order to better mitigate the risk of SF6 emissions in particular when the existing gas instrumentation is not accurate enough to provide early detection: Pressure/density switches used for safety considerations (to prevent catastrophic failure) lack of sensitivity, and manual leak checks only provide discrete check points. Instead, stationary leak detection systems enable a permanent monitoring and early warning in the case of a leakage event occurring.

Our 3731 system leverages 20-years of leadership on the ultra-sensitive photoacoustic sensing technique to provide a direct and integral leak detection solution capable of monitoring large switchgear rooms. The system verifies that the GIS Equipment operates below the industrial target of 0.5% yearly leakage rate or better.

The 3731 system can detect within a short response time any excessive increase in the leak rate, enabling to decrease the number – hence the cost – of periodic leak checks while providing early leak detection.

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The SF6 leak detection system – INNOVA 3731 – features ultra-high sensitivity with its state-of-the-art photoacoustic monitor. It draws air samples from up to 24 locations for maximum coverage of the GIS substation. Tubing lines can easily run into existing control cable trays, or trenches. Analog and alarm relay outputs can be connected to local RTU.


Technical Data

Measurement Technique 
Photoacoustic infrared spectroscopy.
Measurement Specifications1
Detection Limit: 6 ppb (standard)
Dynamic Range: 5 - 50,000 ppb (50 ppm) Standard;
1 - 4,000 ppm Optional
Zero Drift:

Typically ± Detection limit4 per 3 months1

Influence of temperature2 : +/- 10 % of detection limit4 /°C.

Influence of Pressure3 : +/-0.5 % of detection limit 4 /mbar.

Repeatability: 1 % of measured value1
Range Drift: +/- 2.5 % of measured value per 3 months1

Influence of temperature2 : +/- 0.3 % of measured value/°C.

Influence of pressure3 : -0.01 % of measured value/mbar.

Response Time
Standard Mode 27 s
Fast Mode 13 s
The monitor has three interfaces, USB, Ethernet, and RS-232, for data exchange and remote control of the 3730. The software communicates using the USB, Ethernet, or RS-232 interface.
Reference Conditions:
1 Measured at 20 °C , 1013 mbar, and relative humidity (RH): 60%. (A concentration of 100x detection limit4 was used in determining these specifications.)

2 Measured at 1013 mbar, and RH: 60 %.

3 Measured at 20 °C and RH: 60 %.

4 Detection limit is @5s S.I.T

Interference: The 3730 automatically compensates for temperature and pressure fluctuations in its analysis cell and can compensate for water vapor in the air sample. If an optical filter is installed to measure a known interferent, the 3730 can cross compensate for the interferent.
Pumping Rate: 30 cm3/s (flushing sampling tube) and 5 cm3/s (flushing measurement chamber).
Power Requirement: 100-240 VAC +/- 10%, 50-60 Hz.
Power Consumption: 135 VA (SF6 detector + sampler)
Total Internal Volume: The total Internal Volume of the measurement system: 60 cm3
Air Volume per sample:
Flushing Settings Volume of Air
Auto: Tube Length: 1m 140 cm3 /sample
Fixed time: Chamber 2s, Tube 3s 100 cm3 /sample
Fixed time: Chamber 2s,Tube “OFF” 10 cm3 /sample
Alarm Relay Socket: for connection to one or two alarm relays (visual/audio). Alarm levels for each gas are user-defined. Max. 25 VDC, max.100 mA.

SF6 Detector: 175 mm (H) x 483 mm (W) x 375mm (D) (6.9 in x 19 in x 14.8 in)

1409 rack version: 155 mm (H) x 483 mm (W) x 260 mm (D) (6.10 in x 19 in x 10.2 in)


SF6 Detector: 14 kg (30.81lbs)

1409 with 6/12/24 channels:
6.6/7.9/10.3 kg (14.6/17.4/22/7 lbs)

Compliance with Standards
The 3730 has the following certifications:
  • CE-mark (for compliance with EMC and Low Voltage Directives),

The detailed Certificate of Conformity documents are available in our download section.

Detection Limits

Converting concentration units

The detection limits in the Detection Limit Chart are given in "parts per million" by volume (ppm) at 20°C and 1 atmosphere of pressure. These values can be converted into the concentration unit "mg/m3" by using the equation below:

For a gas at 20°C and at 1 atmosphere of pressure:
Concentration (mg/m3)= [Concentration(ppm) * Molec. weight (g/mol)] / [24.04 l/mol]

Detection Limit (for SF6):
Gas Detection limit (ppm) Filter number
SF6 0.006 UA0988

 INNOVA Detection Limits Chart (1.12 mb)

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