Use of Excel Sheet for Calculations of Transformer Overcurrent and Earthfault Relay Settings.

Calculations of overcurrent and earthfault relay settings of transformer is monotonous and mechanized job. Hence now a days use of Excel Sheet for such calculations is very common. Here two excel sheets has been developed viz.

1)    Excel Sheet for calculations of overcurrent and earthfault relay for transformer operating separately.

2)    Excel Sheet for calculations ofovercurrent and earthfault relay for transformer operating in parallel.

For understanding the formulae used for calculations proper range names are adopted throughout the sheet as shown below for better understanding of the calculation method. Note that calculation range and setting result range are kept protected to avoid accidental changes. However no protection password is adopted for the sheet.

Readers are encouraged for downloading the Excel Sheet. Also they can experiment with the sheet; or even can change the formulae as per custom needs if required. Such study of the formulae used in sheet and experimenting with sheet will make it possible to develop own calculation sheets and also improve overall understanding of the setting methodology.

Here two practical examples calculations of overcurrent and earthfault relay settings are done using two Excel Sheet mentioned above and covered in next section. Calculation steps shown in example are self-explanatory.  Readers are requested to go through the example carefully and preferably with hand calculations before to start of using the Excel Sheet.