Dissolved Gas Analysis

Maine Technical Services, Inc offers Dissolved Gas Analysis (DGA) testing of transformer insulating fluids. Dissolved gas analysis is the most important tool in determining the condition of a transformer. It is the first indicator of a problem and can identify deteriorating insulation and oil, overheating, hot spots, partial discharge, and arcing. The health of the oil is reflective of the health of the transformer itself. We offer on-site dissolved gas collection services or we will provide syringes and sampling procedures for customers to collect their own samples and mail to our lab.

A four condition dissolved gas analysis (DGA) collection guide to classify risks to transformers with no previous problems has been published in the Standard IEEE C57-104. The guide uses a combination of individual gases and total combustible gas concentration as indicators. The condition levels are shown in the table below.

Dissolved gas concentrations

Status Dissolved key gas concentration limits
Hydrogen Methane Acetylene Ethylene Ethane Carbon monoxide Carbon dioxide TDCG
Condition 1 100 120 1 50 65 350 2500 720
Condition 2 101 - 700 121 - 400 2 - 9 51 - 100 66 - 100 351 - 570 2500 - 4000 721 - 1920
Condition 3 701 - 1800 401 - 1000 10 - 35 101 - 200 101 - 150 571 - 1400 4001 - 10000 1921 - 4630
Condition 4 > 1800 > 1000 > 35 > 200 > 150 > 1400 > 10000 > 4630

Condition 1 - TDCG below this level indicates the transformer is operating satisfactorily. Any individual combustible gas exceeding specified levels should prompt additional investigation.
Condition 2 - TDCG within this range indicates greater than normal combustible gas level. Any individual combustible gas exceeding specified levels should prompt additional investigation. See chart. Action should be taken to establish a trend. Faults may be present.
Condition 3 - TDCG within this range indicates a high level of cellulose decomposition. Any individual combustible gas exceeding specified levels should prompt additional investigation. Proceed per chart. Immediate action should be taken to establish a trend. Faults are probably present.
Condition 4 - TDCG exceeding this value indicates excessive decomposition. Continued operation could result in failure of the transformer. Proceed immediately and with caution per chart.

TDCG levels (μL/L) TDCG rate (μL/L/day) Sampling intervals and operating procedures for gas generation rates
Sampling interval Operating procedures
Condition 4 > 4630 > 30 Daily Consider removal from service.
Advise manufacturer.
10 to 30 Daily
< 10 Weekly Exercise extreme caution.
Analyze for individual gases.
Plan outage. Advise manufacturer.
Condition 3 1921 to 4630 > 30 Weekly Exercise extreme caution.
Analyze for individual gases.
Plan outage.
Advise manufacturer.
10 to 30 Weekly
< 10 Monthly
Condition 2 721 to 1920 > 30 Monthly Exercise caution.
Analyze for individual gases.
Determine load dependence.
10 to 30 Monthly
< 10 Quarterly
Condition 1 ≤ 720 > 30 Monthly Exercise caution.
Analyze for individual gases.
Determine load dependence.
Continue normal operation.
10 to 30 Quarterly
< 10 Annual
 
 

8283 Seneca Turnpike, Clinton NY 13323 : Phone: 315-272-7959 / Fax: 315-733-4474
E-mail tmaine@MaineTechnicalServices.com