TRANSFORMERS WITH NO-LEAK GUARANTEE

Mr. Swapan Kumar Datta, General Manager – Technology

Of Nu-Cork Products (P) Ltd., Gurgaon, Haryana, India    

It is generally agreed that moisture in the insulation of Power Transformers is un desirable because of various long term adverse effects on dielectric integrity:

n Reduction in dielectric strength of oil

n Accelerated ageing of insulation

n Bubble generation in the solid insulation    during overloads

n Ageing factor 

MAIN SOURCES OF WATER CONTAMINATION

nIn Service 

 

nMoisture ingress through breathing system

 

nMoisture ingress through poor gaskets

 

nMoisture ingress from water cooling system

 

nResult of aging

MAIN SOURCES OF WATER CONTAMINATION

nDuring Repair

 

nMoisture adsorption when tank is open

 

nMoisture condensation on the tank during improper drying

 

nUse of inadequately dried materials

 

nIngress of residual moisture from oil-filling equipment

 

Atmospheric water is the main source of transformer contamination. Ingress of moisture into the tank in the form of molecular (kundsen) flow due to the difference in water concentration in atmospheric and the oil in the tank, and viscous flow of wet air into the transformer under the action of difference in pressure (atmospheric and inside the tank)

 

nA good gasket hardly costs 0.3 % cost of the transformer. Bad gasket may consume 50 % life of a transformer. It is therefore prudent to include gasket testing in the quality assurance programme.    

DANGEROUS EFFECT OF DEGRADATION FACTORS

                 

EFFECT OF WATER AND OXYGEN ON AGING

CASE STUDIES

T1 – Transformer oil preservation system well maintained with no-leak.

 

T2 – Transformer oil preservation system            not properly maintained and with very heavy leak due to poor gasket.  

Conclusion

nA gasket must create a seal and hold it over a long period of time.

nIt is prudent to include gasket testing in the quality assurance programme.

nIt is not only good gasket but proper installation techniques are key requirements.

nCareful DGA analysis, oxygen and moisture is precursor to gasket problem.

nIf moisture in transformer is doubled, life is reduced by half.

nConsequence of bad gasket in your transformer would give unpleasant reading in books of accounts.