Laxmi Associates


“Today the concept has changed and efforts are being directed to explore new approaches/techniques of monitoring.”

Residual Life Assessment & Residual Life Extension

Today the concept has changed and efforts are being directed to explore new approaches/techniques of monitoring, diagnosis, life assessment and condition evaluation, and possibility of extending the life of assets such as Power transformers, Circuit breakers, CTs, Cables, Generator, Motors etc
Our service team undertaken RLA (Residual Life Assessment) and RLE (Residual Life Extension) studies for entire sub-stations and MV Switchgears. We carry out testing of various types of test objects such as Transformers, Circuit Breakers, Isolators, CT/CVT, Motors etc using reliable and accurate test and measuring instruments
The RLA & condition assessment process ranges from assessing equipment design specifications, factory test data, operating and maintenance history information and on-site test data during service life of the equipment.
RLA & condition assessment process is a three stage approach and explained here below with the example of Power Transformer:

Stage 1- On line tests & Operational, design & historic information

This would be a review of all engineering design and operational documents, past test data including regular scans with on-line test methods. New oil tests would be undertaken. This should identify the common problems and prioritize which offline tests are more important in second phase for detail review Activities: External inspection, IR/UHF surveys, and oil tests for main tank and LTC including DGA and FURAN,
Checking of pump operation and fans.

Stage 2 – Off-line test on all units

Focus on those that indicate risk from Sage 1. Undertake a range of outage tests to investigate issues, and correlate with assessment from stage 1. Activities: Off line tests- PF/Cap, Winding and insulation resistance, SFRA, Turns Ratio , Leakage Reactance,

Bushing, surge arrester testing, OLTC operation and dynamic contact resistance measurement, Moisture analysis of paper insulation by dielectric method (PDC+ FDS).

Stage 3 – Classification of Transformer and recommendation for future test:

All units will be assessed in terms of design groups with problems, overall condition, thermal mechanical and dielectric condition. Assessment will be based on
  • Operational problems and design group history
  • Oil condition of main tank & selectors
  • Thermal ageing and hot spots in winding and connection
  • Dielectric condition
  • Mechanical condition
The test frequency and recommended test will be modified after each cycle of measurement depending upon the condition of Transformer.
We create a detailed analysis report and submit our recommendations for further maintenance activity or service/repair/replace parts or equipment. Actions taken on our recommendations lead to a drastic reduction of equipment break-downs and increase in the availability of sub-station equipment.
In general, such as Generator Transformers, Station Transformers and Inter-connecting Transformer, Generators are required to be highly reliable so that operational as well as safety risks at site are minimized. In order to ensure transformer reliability, it is vital to assess the extent of ageing and early identification of emerging faults. We offer a suite of tests referred to as Residual Life Assessment which helps in assessing remaining useful life of a given transformer.

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