Dissolved Gas Analysis (DGA) is one of the most powerful diagnostic tools available for assessing the internal condition of oil-filled electrical equipment such as power transformers. By analysing the types and concentrations of gases dissolved in the insulating oil, engineers can detect developing faults — including partial discharge, thermal hotspots, arcing, and insulation degradation — long before catastrophic failure occurs.
However, the accuracy and reliability of DGA results depend entirely on sample quality and repeatability. A compromised or contaminated sample can produce misleading results, leading to incorrect fault diagnoses, unnecessary maintenance, or worse — missed warnings of a genuine fault.
One of the most significant and often overlooked sources of error in field DGA sampling is cross contamination. This occurs when residual oil or dissolved gases from a previous sample or from the sampling equipment itself are carried into a new sample. The consequences can be subtle but serious: artificially elevated gas concentrations, false positive fault indications, or masking of real fault gases.
Cross contamination commonly arises from:
- Reuse of sampling syringes or bottles without adequate purging
- Shared sampling valves or couplings used across multiple assets
- Residual oil left in hoses or adapters between sampling events
- Improper purging procedures in the field
Trans-Sample dedicated oil sampling couplings are specifically engineered to eliminate these risks. Each coupling is permanently installed on a single asset and provides a dedicated, sealed sampling interface that is never shared between transformers. This means there is no pathway for cross contamination between assets.
The Trans-Sample coupling uses a precision ball valve with PTFE seals to maintain a clean, isolated oil column at the sample point between sampling events. When a technician connects the sampling syringe or bottle, they access only the oil from that specific transformer — with no exposure to residual fluids from other equipment or shared tools.
Beyond contamination prevention, the fixed installation of Trans-Sample couplings also improves repeatability. Samples are always taken from the same location on the transformer, at the same depth, eliminating variability introduced by different access points or connection methods.
For power utilities and asset managers seeking to maximise the diagnostic value of their DGA programmes, investing in dedicated, asset-specific sampling infrastructure is a straightforward and cost-effective measure. The integrity of the sample is the foundation of the entire analysis — and Trans-Sample couplings are designed from the ground up to protect that integrity.