Tap Changer Activity Signature Analysis

After performing a TASA® analysis on your tapchanger, you will receive a condition rating. The recommended sampling interval ranges from ‘immediately’ to ‘annually’, depending on the condition of your unit. Please refer to the scoring methodology or reach out to TJ|H2b for further explanation on recommended intervals.

TASA® condition codes, in general, indicate the following+:

• Code 1: All parameters within acceptable limits. Retest within 12 months.
• Code 2: Onset of fault activity or oil degradation is evident. Retest within 6 months.
• Code 3: Substantial development of fault and/or deteriorating oil quality. Retest within 3 months.
• Code 4: Serious fault activity and/or very poor oil quality. Further investigative action required. Retest within 14 days.
• Code 4:* Urgent action required. Retest immediately. Subject to confirmation via repeat sample, an internal inspection may be required, proceed immediately and with caution.

+Some variations of the recommended mitigations or retest intervals may occur at the discretion of the laboratory based on information provided. With tapchangers, we are dealing with a complex subject involving a number of variables. As such, general “rules of thumb” with regard to sampling intervals cannot be applied in every case. A number of other factors must be taken into consideration, such as:

• Service history 
• Maintenance history
• Model type
• Age
• Number of operations
• Criticality

As such, the appropriate action is up to the discretion of the Asset Manager who is best placed to take other influencing factors into account according to established internal procedures. Our codes and recommendations, while based on a vast amount of experience as well as guidelines published by IEEE and other standards bodies, are to be taken only as useful guides.

A Tapchanger Activity Signature Assessment (TASA®) includes a condition rating, diagnostics, and potential remediation actions where applicable. Upon receipt of the report from TJ|H2b, we recommend that results and diagnostics are reviewed promptly, following internal procedures. If further support is needed, TJ|H2b offers free, 24/7 consultation services to help you understand reports and provide guidance.

TJ|H2b recommends following the latest revision of ASTM D923 (Standard Practices for Sampling Electrical Insulating Liquids) or an equivalent standard in order to ensure consistent, high-quality sampling practices. TJ|H2b has developed a tool to help you meet the standard and take a proper, representative sample every time: Turbulent Flush Sampling System.