Relay Settings in “Overcurrent” Room, Part 3

As mentioned before if the relay characteristic curve is provided as a table of points, the user needs to manually enter these points into the software. To do so, first, “Table Example 2” is selected from “Custom” folder in “Manage/Select Characteristic” window. You can see that, by default, a curve is created in this section using the points table.

To specify a new curve, by clicking on “Copy to User Define” option, this curve is copied to “User Define” folder and after selecting this curve in “User Define” folder, by clicking on “Grab” the window related to the “Grabber” opens. In this diagram the "X" axis is the current axis, and the "Y" axis is the time axis. In “Axes” section, to show the curve, the current range is specified in terms of “IPu” and the time range is specified in terms of seconds. For example, here the current range is specified between 1 “IPu” and 100 “IPu” and the current axis is displayed between 1 and 100 “IPu”. “IPu” is the CT secondary nominal current. Also, by unchecking the “Logarithmic” option, it is possible to change the diagram display from logarithmic to regular. Also, by using “Open” and “Save” options it is possible to save the created file in this section and open it again on this page and edit or use it if necessary.

Now, from the toolbar click on “New” to open a new blank page for the new curve. In “Point” section, enter the current in “Current” field and time in “Time” field and then “Add” them to the points table of the intended characteristic curve so that it is displayed in the diagram at the right side. Also, by clicking on the related diagram and selecting “Add” or by using the “Ctrl” key and clicking on the diagram, it is possible to create the characteristic curve. By using “Add” and “Insert” buttons, it is possible to add the point entered in “Point” section to the last row of the table and before the selected row respectively.

If the user has a logarithmic image of the relay characteristic curve, it is possible to “Load” it in this window by using “Load Image” option and create the relay characteristic curve for the test by adding the point on the entered curve. Now, here we enter an image of the “7UT63” relay overcurrent characteristic. Then it is necessary to equalize the “Scales” of the diagram in this page with the “Scales” of the entered diagram. To do so, first, by using Alt+left click combination key the current and time axes of the entered image are equalized with the current and time axes of the “Grabber” window. Then, the “Start” and “End” values are specified in “Current” section as 1.05Pu1 and 1.45 respectively. Also, the “Start” and “End” values are specified in “Time” section as 0.05 and 200 seconds. You can see that both diagrams are completely overlapping. Note that these numbers are different for images with different sizes and they need to be specified by the user in a way that the two diagrams overlap in terms of values and size.

Now, by holding down the “Ctrl” key and clicking on the curve with “Dial Setting=0.1”, this characteristic curve is created and approved. If you wish to save this curve in the software for future tests, you need to copy it using the “Copy” button and “Paste” it in “User Defined” folder. Now, by selecting “Save”, the intended characteristic curve is saved in this folder and is usable for next tests.

Note that if a later version of the software is installed, this saved file is removed from the “User Defined” folder. So before installing the new version of the software, it is necessary to make an output “Xml” file by using the “Export” button from “Manage Select Characteristic” page and then “Import” it to the new version. This characteristic curve is displayed in the diagram at the right side of the “Overcurrent Protection Parameters” window. Note that for the characteristic curves created using this method, the time entered in “Time” column of the characteristic table of the characteristic curve is a coefficient which is multiplied by the times entered in the characteristic points table and as a result it influences the characteristic curve time and relay operation time.