Original scientific paper
CASE STUDY ON TRANSFORMER MODELS FOR CALCULATION OF HIGH FREQUENCY TRANSMITTED OVERVOLTAGES
Bruno Jurišić
; EDF R&D, France
Ivo Uglešić
; University of Zagreb, Croatia
Alain Xemard
; EDF R&D, France
Françoise Paladian
; Université Blaise Pascal, France
Philippe Guuinic
; EDF R&D, France
Abstract
Events such as lightning, switching of vacuum circuit breaker or switching operations in gas
insulated substation (GIS) generate high frequency overvoltages. An equipment in a transmission or a
distribution system has to be protected against such phenomena.
Unfortunately, the traditional transformer models available in Electromagnetic transient simulations
program (EMTP-like) software packages are not capable of representing transformer behavior in a transient
state, which includes high frequencies. Moreover, high frequency transformer models are often too complex
or require confidential information on transformer geometry. However, in the design stage of insulation
coordination it is particularly important to accurately calculate transmitted overvoltages through
transformers.
In the scope of this paper two different transformer models for high frequency, are developed in an
EMTP-type software program. The first model named “Black box” derives solely from the values measured
on the transformer terminals and does not require any knowledge of the transformer inner geometry. The
second model named “Grey box”, is based on a lumped RLC parameters network, whose values are
derived from the simple geometry of the transformer window and from the nameplate data. Furthermore,
the models’ capabilities to characterize a transformer at high frequencies are analyzed. The case study is
done on a distribution transformer which is to be located inside a power plant. The transmitted overvoltages
calculated with the models in the EMTP-type software program are compared with measurements.
Keywords
“Black box”; EMTP-type software; “Grey box”; high frequency transients; lightning; rational approximation; transformer modelling
Hrčak ID:
199261
URI
Publication date:
15.8.2017.
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