Test method for verifying harmonic braking coefficient of relay protection calib

Harmonic braking coefficient verification (transformer differential protection part) test wiring

Wiring method 1 (applying current on both high and low voltage sides simultaneously):

The microcomputer relay protection calibrator IA is connected to phase A on the high voltage side, IB is connected to phase A on the low voltage side, and the neutral wires on the high and low voltage sides are short circuited before being connected to the tester IN.

Wiring method 2 (only adding current on the high-voltage side):

The microcomputer relay protection calibrator IA is connected to phase A on the high-voltage side, and the neutral line on the high-voltage side is connected to the tester IN test method.

Test steps:

Start the experiment

After confirming that the connection is correct, click the "Start Test" button or the F2 shortcut key on the keyboard to start the test;

If the "Manual Control" mode is selected in the experimental operation mode, the "Output Increase" and "Output Decrease" keys can be used;

The test data set before the experiment may have changes in the amplitude and phase of certain quantities during the experiment. After the experiment is completed, selecting "Operation" ->"Restore Setting Values" on the menu can restore the data to the initial values before the experiment, which greatly facilitates repetitive testing;

Click the 'Exit Test' button or the F3 shortcut key on the keyboard to exit the test.

Taking wiring method 2 as an example (applying current on both high and low voltage sides simultaneously):

Assuming that the second harmonic braking coefficient of a certain transformer is 20%.

First, select "Calculate as a percentage of fundamental wave" in the "Harmonic Calculation Method" menu, then select IA, set the fundamental wave amplitude to 2A (note: this value must be greater than the action threshold of differential protection), and set the second harmonic to 25% (greater than 20% of the harmonic braking coefficient, so that the protection will not act at the beginning of the test) in the harmonic parameter table. Then, set the amplitude step to 1%, and select the "manual control" method.

To start the test, the protection should be in a closed state. Slowly reduce the variable to the protection action by step. The second harmonic value of IA during operation is compared with the adjusted braking coefficient.

Test reminder

When using wiring method 1 for testing, it is not possible to choose 'calculated as a percentage of fundamental wave'.