GAP Generator assessment process

The life of a generator is mainly dependent on the life of its insulation. Therefore the aging process of the generator has to be very closely monitored. Just like the pulse rate, the blood pressure, sugar level etc., of a human are indicative of his health condition, the capacitance, leakage current, dissipation factor, polarization index, surge voltage with standing strength and partial discharge factors are indicative of the insulation condition of an electric rotating machine.

Estimation of the remaining life of a generator is based on the following information:

• The life history of the generator
• A diagnostic evaluation of the generator’s condition
• The operation mode planned in the future

On an average, the lifetime of the stator and rotor winding of a base loaded generator is about 35 and 25 years respectively. The lifetime will get reduced due to peak load or abnormal operating conditions. Other factors, such as, insulation abrasion, loose end- windings support and contamination may reduce the lifetime expectancy even more.

alfanar Technical Services now offers GAP – a solution to lifetime assessment of generators – addresses the problems faced during the lifetime of a generator with an aim of increasing reliability and availability. Moreover, GAP is designed to perform generator assessment linked to the planned outage of the plant and thereby minimizing downtime.

The past study and experience has shown that the availability of generator is determined largely by stator winding system, and thereby GAP methodology focus more on the stator winding compared to the rotor and other parts of the generator.

Why Assessment ?

Sudden breakdown of the stator winding in a generator under operation can result in significant financial losses to utilities due to unplanned downtime. Failures in generator stator windings occur as a result of insulation deterioration initiated by voids created in the insulation material from the combined effects of TEAM – Thermal, Electrical, Ambient and Mechanical – of stresses during long-term operation. Therefore, GAP analyze deterioration characteristics and, ultimately, to use the analysis results for evaluating the insulation condition and remaining life of the generators.

Benefits : 

• Increases availability and reliability
• Increases profitability by less unplanned  downtime and minimum interruptions
• Enhances safety
• Gives you accurate information for  maintenance plans and actions
• Evaluates the condition of your generator  and its components, identifies most  critical parts
• Helps you to manage assets more  efficiently
• Prevents accidents that can harm people  and the environment

 

GAP1 : On-line Assessment

Assessment based on historical,˝ˇ maintenance and operational data˝ˇ and of similar units. Perform thermal˝ˇ life assessment

GAP2 : 1-2 Days Assessment

GAP1 assessment with diagnostic˝ˇ tests in assembled condition. Assess˝ˇ healthiness of stator and rotor˝ˇ windings and perform diagnostic life˝ˇ assessment.

GAP3 : 3 -4 Days Assessment

GAP1 and GAP2 assessment with˝ˇ rotor-in and partial dismantling.˝ˇ Perform visual examination and tests˝ˇ to the extent feasible. Life estimation

GAP4 : 7 -10 Days Assessment

GAP1 and GAP2 assessments with˝ˇ rotor-out. Perform ELCID, wedge˝ˇ tightness, bump, corona and other˝ˇ special tests. Perform condition and˝ˇ life assessment.

Planned Outage  – Reference

• SEC Tabuk Power Plant 2
• SEC Duba Power Plant
• SEC AL Wajh Power Plant
• SEC Makkah Power Plant
• SWCC Jubail Power Plant
• MARAFIQ Yanbu Power Plant
• Mass Global, Iraq-Kurdistan
• SABIC – SAUDI KAYAN
• SABIC – SAFCO
• SABIC – IBN AL-BAYTAR