Annual Report 2011-2012

Annual Research Report 2011-2012
Project Title:
An Investigation on Grounding Transformer Failures in
Zanjan Regional Electric Company (ZREC) Substations and
Presenting Applicable Solutions for Prevention of this
Problem
Department: Transmission & Substation Dept.
Employer: Zanjan Regional Electric Company
Project Manager: S. J. A. Vaseai
Project Code: CTQBZ01
Project Staff: S. Farzalizadeh, M.R. Shariati, A. Bashghareh, O. Alizadeh, P. Khazaee
Project Summary:
Grounding transformers are one of the substation’s equipments that their failure could
lead to direct costs such as purchase, installation and maintenance cost as well as
indirect costs such as outages and decrease of network reliability. Several grounding
transformers are damaged in the electrical networks every year, therefore investigating
these failures and presenting the applicable solutions is very important.
For investigation the probable events that may had led to failure in grounding
transformers, five substations on ZREC have been studied in this project: Gazvin
230/63/20 kV, Bidestan 63/20 kV, Geydar 63/20 kV, Sorb-o-Roy 63/20 kV and Abhar3
63/20 kV substations. In two of these substations the grounding transformer failure had
been occurred before.
According to this issue the factors that were more likely to cause failure in transformers
have been studied, comprising Lightning and arresters, Switching transients,Ferro
resonance,Short circuit calculations,Operational and maintenance history,Grounding
system,High impedance fault, Leakage current,resonance, Relay and protection. Finally
after precise study for assessing major cause or causes in grounding transformers
failures on ZREC practical solutions have been accomplished.
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