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With the help of TransView it is possible to locate a fault using either the unidirectional fault locator (with oneCOMTRADE file) or the bidirectional fault locator, where the fault records from both ends of the line areneeded. This Application Note describes which actions have to be taken in order to verify the fault locationusing one or two fault records. For locating a fault with only one fault record basically the same actions haveto be taken apart from inserting a second fault.
2 Locating the Fault Using a Single Fault Record
First we try to locate a fault using only one fault record. Therefore load the fault record using the Open
To check if the channels in the fault record are correctly mapped to the network model that TransView usesfor all calculations, open the Network Configuration window using the menu entry Options -> NetworkConfiguration....
Check if signals from the COMTRADE are correctly assigned to the voltages and currents from the networkand the CT and VT ratios are correct. Also check if the CT starpoint direction is correct.
Figure 2: Configuring the first fault record
All the parameters for the calculation of the fault location must be entered in the Fault Locator tab. Pleasenote that the parameters in the Impedance Calculation tab are used for the calculation of the impedance
locus, but have no influence on the fault location.
To make the input of the line parameters most convenient you can change the input format of the data to theformat that is most suitable for you.
If your line should consist of several sections with different parameters you can add an additional section,this is most useful if you have short cable sections in your overhead line.
Now that all required data for the fault locator is specified, the fault locator can be executed.
Figure 5: Fault locator button
The fault locator view is opened and a calculated fault location displayed.
Figure 6: Evaluated single-sided fault location
The fault locator calculates the fault location at about 5.7 km distance from K1. For a line to earth fault with asingle-sided fault location calculation the k-factor defined in the relay is crucial. In order to minimize theinfluence of the k-factor and to make the fault location more precise, a double-ended fault location could beperformed.
The benefit in locating a fault with two fault records is that for the calculation of the fault location the k-factoris not taken into account. For this reason potential imprecision can be eliminated and a more precise faultlocation is possible.
For the double-ended fault location the second fault record from the opposite side of the line has to beloaded into the last calculation. Therefore navigate to the menu bar and selectInsert -> Fault Record....
Figure 7: Loading the second fault record
3.1 Configuration
This fault record is now loaded as network node K2, whereas the first fault record stands for K1. Again the signals have to be assigned for the second fault record as described before (Figure 2). Additionally check if the CT starpoint direction is correct. This information is crucial for the double-ended faultlocation. Without this information being correct, locating a fault is not possible.
In the Fault Locator tab it has to be checked if the network node at the opposite end of the line is set to K1.
The line data has already been defined when we imported the first fault record, so we don't have to changeanything there. The line data for the nodes K1 and K2 are automatically matched.
After these settings have been checked, switch back to the fault locator (Figure 5). If the double-ended faultlocation is successful, three curves should be displayed.
If you note slight changes in the synchronization of the two fault records, please do not worry. To make thecalculation more precise the fault locator algorithms in TransView automatically synchronizes the two faultrecords using the prefault state. This synchronization is far more precise than any manually performedsynchronization.
K1:Evaluation (double-ended) shows the evaluated fault location using both fault records. For this methodthe k-factor set for the line is not necessary. With a high probability the fault is located where the double-ended evaluation shows it. Another rule is that the spikier this curve is the higher is the probability of the faultlocated at that position. It's very much an interpretation of statistical data using the average and the standarddeviation. The less dependable the input data due to distortions or non-sinusoidal wave forms is, the largerthe standard deviation.
K1:Evaluation and K2:Evaluation_1 show the fault location calculated with only the signals for a singlenetwork node. For this method the k-factor of the line is very important.In our case the fault location calculated with the signals from K1 is quite far apart from the fault location
calculated with the signals from the other end of the line. This typically shows that thek-factor set for the line isn't adequate enough.
As the fault location from the two-ended fault locator is very dependable you can now try to find out what thecorrect k-factor is. If it is a lot different than the original factor it is advisable that you measure the k-Factorfor example using a CPC100, as your distance protection cannot work correctly with wrong parameters.
Therefore switch back to the Network Configuration and change the k-factor for the line until both curves getclose to each other.