1 00:00:19,148 --> 00:00:21,553 CT Excitation Test, Part II: 2 00:00:21,578 --> 00:00:27,539 To perform this test, the first parameter to be entered is the “CT” secondary resistance. 3 00:00:27,564 --> 00:00:34,632 This resistance is used to estimate the knee point and is selected from “Max RCT” field by default. 4 00:00:34,657 --> 00:00:40,695 But if the resistance test has already been done, this resistance is selected from “Rmeas”. 5 00:00:40,720 --> 00:00:48,101 Note that, since some users skip the resistance test and try to directly perform this test, this field can be edited manually. 6 00:00:48,126 --> 00:00:52,462 In the "Efs" field, the knee point is estimated using the formula. 7 00:00:52,487 --> 00:00:59,118 The importance of this number is in calculating "Vend" to determine the final voltage of test evaluation. 8 00:00:59,172 --> 00:01:07,172 The assessment of this test is based on the finding of the knee point, so that if the knee point is found, the test is "Passed" and otherwise "Failed". 9 00:01:07,181 --> 00:01:12,516 Once the resistance value has been specified, the test settings is entered in "State Setting". 10 00:01:12,557 --> 00:01:21,674 If "Demagnetize" option is ticked, before performing the test evaluation, the software once demagnetizes the "CT" with "AC" voltage and current. 11 00:01:21,705 --> 00:01:25,455 so that the residual flux caused by theresistance test is removed. 12 00:01:25,479 --> 00:01:31,240 In this section, you must enter the time "Demagnetize" and voltage in a percentage of "Vend". 13 00:01:31,264 --> 00:01:40,389 In the next step if “Calc. from Test Object” is checked, the software calculates the frequency and final voltage of the test by using the information entered in “Test Object” 14 00:01:40,413 --> 00:01:43,839 If you wish to enter this manually, you should uncheck this option. 15 00:01:43,863 --> 00:01:47,425 In “Excitation Time Test” field, the test time is entered. 16 00:01:47,449 --> 00:01:53,642 Note that, it is possible to show the saturation curve with less fluctuation by increasing the test time. 17 00:01:53,666 --> 00:02:05,826 In “Choose Current Measurement Mode” section, it is possible to specify the maximum current from among “Low Current” with maximum 500 milliamps and “High Current” with maximum 800milliamps. 18 00:02:05,851 --> 00:02:10,014 Note that by selecting any of these options, the wiring changes. 19 00:02:10,052 --> 00:02:13,037 Performing the test and analyzing the results 20 00:02:13,062 --> 00:02:21,912 In this test, the test information is entered is this page in accordance with the information entered in “Test Object” and the performed resistance test. 21 00:02:22,449 --> 00:02:29,404 Also, the wiring is done according to the “CT” model characteristics which are different for different models of “CTs”. 22 00:02:29,429 --> 00:02:40,592 Note that in this wiring the device voltage output is connected to the capacitor positive output and it is necessary that the two negative polarities of the capacitors are connected to each other. 23 00:02:40,789 --> 00:02:47,524 It should also be noted that series capacitors are used to filter the “DC” voltage of the device. 24 00:02:47,549 --> 00:02:56,543 By clicking on “Init Test”, the needed “States” open in “Table View” and the necessary changes are automatically applied in “Signal View”. 25 00:02:56,909 --> 00:03:06,206 Note that the voltage is displayed in “Signal View” in form of “RMS” and it is possible to change the view to sine by selecting “Instantaneous” option. 26 00:03:08,164 --> 00:03:16,902 After performing the test, in “Signal View” you can see that first the “CT” is demagnetized and then the excitation test begins. 27 00:03:21,340 --> 00:03:26,685 In “Lissajous” tab, the saturation curve can be viewed in terms of voltage and current. 28 00:03:26,710 --> 00:03:31,597 In this curve the linear area between the two plus signs is depicted in pink. 29 00:03:31,622 --> 00:03:41,964 After finishing the test, the knee point and the saturation point are depicted with green and the results and the evaluation are recorded in “Excitation Result” section. 30 00:03:41,989 --> 00:03:51,389 Since in performing this test the saturation curve points are of significance too, by selecting “Add to Report” option, the points used for the test are added to the report. 31 00:03:51,414 --> 00:03:58,780 Another important point in an excitation test is the current which passes the primary of “CT” and causes the saturation. 32 00:03:58,805 --> 00:04:02,458 Since this current is related to the “CT” connected resistance, 33 00:04:02,483 --> 00:04:11,663 in “Calculation of “Iprimary” section, the connected resistance should be entered in “RL” field and then view the current that causes the “CT” saturation in “Iprim” field. 34 00:04:11,688 --> 00:04:15,000 Here you can see the formula used to calculate this current. 35 00:04:15,025 --> 00:04:20,862 If you wish to set the wiring in a way other than the suggested way, after clicking on “Init Test”, 36 00:04:20,887 --> 00:04:25,657 check “Don’t Change Hardware Setting”, then make your desired changes and initiate the test. 37 00:04:25,682 --> 00:04:31,438 Note that if before finding the saturation and knee points, an “Overcurrent” error is displayed, 38 00:04:31,463 --> 00:04:38,595 the wiring needs to be changed from “Low Current” to “High Current” and then initiate the test after pressing “Init Test”. 39 00:04:38,620 --> 00:04:43,651 If again before finding the knee point the device is displaying an overcurrent error, 40 00:04:43,676 --> 00:04:51,274 this means that the knee point current is higher than the Range of the device and it is not possible to find the knee point using this device.