On-site applications of advanced diagnosis methods for quality assessment of insulation of power transformers

On-site diagnosis methods for quality assessment of large power transformers rise in importance, as deregulation of the energy market demands an improved life time management for expensive equipment. Here, the three complementing methods in use in Switzerland are discussed: Off-line partial discharge diagnosis (PD), frequency response analysis (FRA) and polarisation/depolarisation current measurements (PDC). For PD and for FRA noteworthy experience exists already. However, the PDC method became only recently available as an user-friendly method; its aptitude is described in detail and it is shown how to obtain information on the integral condition of the oil-cellulose insulation system from PDC measurements.

[1]  A. Jonscher.  Dielectric relaxation in solids , 1983 .

[2]  W. S. Zaengl,et al.  Development and application of new condition assessment methods for power transformers , 1998 .

[3]  A. J. Kachler.  On-site diagnosis of power and special transformers , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).

[4]  W. Zaengl,et al.  On-site diagnosis of power transformers by means of relaxation current measurements , 1998, Conference Record of the 1998 IEEE International Symposium on Electrical Insulation (Cat. No.98CH36239).

[5]  E.P. Dick,et al.  Transformer Diagnostic Testing by Frequuency Response Analysis , 1978, IEEE Transactions on Power Apparatus and Systems.

[6]  V. Der Houhanessian,et al.  Application of relaxation current measurements to on-site diagnosis of power transformers , 1997, IEEE 1997 Annual Report Conference on Electrical Insulation and Dielectric Phenomena.

[7]  W. Zaengl,et al.  A novel, compact instrument for the measurement and evaluation of relaxation currents conceived for on-site diagnosis of electric power apparatus , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).

[8]  Vahe Der Houhanessian,et al.  Measurement and analysis of dielectric response in oil-paper insulation systems , 1998 .

[9]  M. Webb,et al.  Polarisation spectrum analysis for diagnosis of insulation systems , 1992 .

[10]  T. Aschwanden,et al.  Assessment of insulation condition of large power transformers by on-site electrical diagnostic methods , 2000, Conference Record of the 2000 IEEE International Symposium on Electrical Insulation (Cat. No.00CH37075).