SmartDGA Guard® - Online 4 Gas Monitor

The SmartDGA Guard® instrument is a cost effective early warning monitoring solution for potential transformer failures. The instrument uses Non-Dispersive Infrared (NDIR) technology to measure and record fault gases Hydrogen (H2), Acetylene (C2H2), Carbon Dioxide (CO2), Carbon Monoxide (CO), and moisture found in insulating (mineral) oil.

  • Capture data 24 hours a day including gas levels, rates, and ratios to detect faults and prevent failures
  • Reduce the number and frequency of transformer maintenance cycles by implementing condition-based maintenance
  • Implement the lowest total cost to own solution in the industry with no consumables, carrier gases, or scheduled calibrations
SmartDGA Guard View

Cost-effective and accurate gas detection solution based on Non-Dispersive Infrared (NDIR) sensor technology to measure fault gases in transformers.

By monitoring these four gases, utilities can detect a wide range of developing and occurring faults including partial discharge, arcing, and thermal faults and unlock the power of diagnostic tools such as CO2/CO and C2H2/H2 ratios.

The SmartDGA Guard™ solution is a lower cost alternative for utilities to monitor transmission and major distribution substation transformers without the full cost of monitoring major transmission transformers, which require monitoring additional gases. Other solutions can require carrier gases, significantly increasing total cost to own over the lifetime of the solution.

The SmartDGA® instrument works in cycles (as often as every 3 hours) to obtain a sample of oil, detect concentrations (in PPM) of key gases, and record the values. Authorized users can then review in the DGA Viewer software or other optional communications.


SmartDGA Guard® Key Functional Features

  • The SmartDGA Guard® package includes the instrument, mounting hardware, connection cable, the SmartDGA EZHub™ unit, and DGA Viewer Software.
  • Versatile mounting configurations (including dual or single valve) with inline mounting option available for non-valve mounting.
  • Extremely cost effective – total cost of ownership is a fraction of the cost of other instruments and installation can be accomplished in just hours.
  • No consumables, carrier gases, or scheduled calibration required.
  • Sunlight visible indicators for Caution, Warning, and Alarm conditions. Has Status Relay notification and corrective action triggering to ensure optimal system operations.
  • Communications supported via all major protocols common in the electric power industry such as Modbus RTU, DNP 3.0, and IEC 61850 with the optional iCore.

Technical Data

Instrument Specifications

NDIR Gas Phase Sensor Accuracy

± 5% or ± LDL, whichever is greater

Reporting Rate Every 24 hours - default, user selectable from approximately 3 hours to 7 days. 
Measurement Range Minimum value is the lower detectable limit, maximum value is the upper limit of accurate response

Moisture Accuracy

± 3 ppm or ± 2% RS

Oil Pressure up to 45 psig (3 bar)
Enclosure Rating IP 55

Sunlight visible indicators for condition codes

Note: Indicators normally flash on for 5 seconds, off for 15 seconds

  • Green - Normal
  • Yellow - Caution
  • Blue - Warning
  • Red - Alarm
  • Red/Blue - System Status Error
  • Green/Yellow - Loss of Communication
Operating Temperature* -50 to 55 °C 
Storage Temperature  -50 to 70 °C
Storage Humidity (non-condensing) 1-99% RH
(L x H x D)
20.9” x 8.6” dia.
Weight ~18.74 lbs
Standards Compliance
The SmartDGA system underwent thorough testing and complies with the following standards.
Emissions / Immunity

EN 61000-6-5 (2001)

EN 61000-6-4 (2007) +A1

EN 61000-3-2 (2006) +A1

EN 61000-3-3 (2008)

Environmental / Vibration ETSI EN 300 019-2-4
Surge Protection 4000V (IEEE C37.90.1-2002)
SmartDGA Guard™ Gas Measurements (Min-Max)
4-50,000 ppm
(C2 H4)
Carbon Monoxide
10-10,000 ppm
5-10,000 ppm
Carbon Dioxide
10-20,000 ppm
EZHub™ & LumaSMART iCore™ Specifications 

Power Supplied to EZHub & iCore

90 ~ 264 VAC, 127 ~ 370 VDC, 47 ~ 63 Hz, 6.5 A max

Power Supplied to Instrument 48 VDC ~ 4.16 A max


Up to 40+ years worth of data storage available with optional iCore

Data Export (Available with EZHub and iCore/PC) Export of results to date in a single file onto a USB memory stick. When using iCore/PC, user can select date range; when using EZHub port, all data is exported

Available Communications (Available with EZHub)

Proprietary communications via RS485 and Ethernet connections to DGA Viewer software

Optional Communications (Modbus available with PC, others available with iCore) IEC61850 Edition 2, DNP3 IEEE Std 1815-2012, Modbus RTU V1.02, Modbus TCP/IP 1.0b protocols
EZHub Alarm Contacts  (3) programmable relay outputs (Type C, NO/NC) for caution, warning, & alarm (1) alarm relay output for system status (Type C, NO/NC)
Relay Contact Ratings Single phase alarm relays (8 A, 250 VAC; 5 A, 30 VDC)

*For operating temperatures less than -20 °C, the cold weather cable is required. Additional eating of oil transfer lines may be required for operation in cold locations. The unit will generate a system fault if the mineral oil temperature is outside of standard fluid limits of -20 and 120 °C. For operating in environments where the temperature routinely exceeds 40 °C, the high temperature accessory is recommended to prevent premature aging and reduction of component lifetime. Temperatures are based upon air temperatures for unit installation in shaded location.

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