Test instruction process of relay protection tester

 Transformer compound voltage blocking (direction) overcurrent protection

This is one of the common backup protections of current large-capacity transformers. When using the "Exchange Test" to simulate, the following points should be noted:

— How to output composite voltage

Compound voltage refers to low voltage and negative sequence voltage. When the overcurrent is blocked, these two voltages are in an "OR" relationship. In other words, it can be understood as a combination of two sets of protections: "low voltage blocking (direction) overcurrent" and "negative sequence voltage blocking (direction) overcurrent". General protection provides two sets of voltage input terminals, one set is used to input low voltage (positive sequence voltage), and the other is used to input negative sequence voltage. Therefore, the voltage wiring is different during the test.

In the protection setting list, "low voltage" and "negative sequence voltage" often refer to line voltage, which can be divided by 1.732 and converted into phase voltage. The tester outputs three-phase voltage for testing. In the low voltage test, set the three-phase voltage phase in the "AC test" as: 0°, -120°, 120°; in the negative sequence voltage test, set the three-phase voltage phase in the "AC test" as: 0°, 120°, -120°;

2. How to match the voltage and current with the output

If three-phase voltage output is used at the same time, one of the current phases can be arbitrarily output during the test.

If two-phase voltage output is used, you need to read the protection manual to see what wiring method is used for the protection. For example, if you use 90° wiring, you can output according to "UAB, IC", "UBC, IA", "UCA, IB"; if you use 0° wiring, you often press "UAB, IA", "UBC, IB", " UCA, IC" method for output.

3. How to test the direction easier

Assuming that a certain protection adopts a 90° connection method, and the low voltage is set to 60V, the following settings can be made in the "AC test" during the test: UA=60V, the phase is 0°; UB=0V, the phase is 0°. In this way, UAB is 60V, 0°. Then fix the voltage and change the phase of the current IC to test the two action boundaries.

4. How to define the "positive" and "negative" of the most sensitive angle

Protection definition: the angle of the voltage leading the current is positive, and vice versa. Assuming that the IC shown in the shaded part on the right is the sensitive angle and UAB is the reference direction of 0°, the sensitive angle of the protection is -45°, and the two action boundaries are 45° and -135° (the shaded part is the action Area).