H.Eisazadeh, H.Javadi, K.Abbasi, G.Ziegler

ABSTRACT
Malfunction of system protection often contributes to outages in HV-grids. Appropriate CT adoption
has sharp influence on the performance of protection system. The techniques of choosing CTs and CT
core requirement assessment will become so significant in this regard. Due to almost large size of HV
grids in addition to CTs and relays variety, manual calculation of CT core requirement is very
complicated and time consuming and, utilizing proper software is inevitable. Moreover, such calculations
require relatively huge input data which should be handled by users and may eventually lead to mistakes
in entering the data. To minimize these errors, the Siemens-provided database in Excel forms, has been
reviewed and analyzed by software in three separated stages. A special Macro inherently in Excel data
sheets is also designed to carry out the tasks and store the results in report sheets.