A differential protection calculator (also called a matrix calculator)

A fault in a protection zone (a part of a network) can be detected by comparing the currents at both ends of the zone. If the currents are different, there is a fault in the zone. The comparison is not straightforward, however, if there is a transformer in the zone, because the magnitudes and often also the phases of the primary and secondary currents of a transformer are different. The measured value of either the primary or secondary current must be corrected, or compensated for the differences due to the transformer before the comparison.

This Differential Protection Calculator (program matrixpr.exe) is designed to calculate the necessary corrections. The phase difference is corrected by multiplying the measured or calculated three phase current vector by a matrix, and the magnitude is corrected by multiplying  by a constant.

In addition, some other simple operations can be done with this program to the current vector, such as the change of the sign, the calculation of the complex conjugate, and the calculation of the sequence components from the phase components, and vice versa

The principle of the correction.

The currents can be edited manually or transferred from the program Elplek (see http://pp.kpnet.fi/ijl ).  This calculator can also be started from the program Elplek, if the matrixpr.exe-file is in the same directory as elplek.exe.

The Vector sheet and the matrix sheet

There are two sheets (or windows, or forms) in the differential protection calculator: The vector sheet and the matrix editor sheet. The main calculations with the three phase current vectors are done in the vector sheet. The matrices for the phase correction (rotation of the vector) can be edited in the matrix editor sheet. The user can switch between the sheets by clicking the "Vector sheet / Matrix editor"-items in the menu bar

The Vector Sheet
 

The Matrix Editor Sheet

Download and installation instructions
Download the matrixpr.zip-file (446 kb, last updated May 30  2010, some polishing only). Unzip it and put all the files in the same directory, of your choice. If you want to start the calculator from the program Elplek, put the files in the same directory with the program elplek.exe.
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