How to set the action frequency and time for frequency and high/low cycle tests of the microcomputer relay protection tester? The microcomputer relay protection tester is mainly used for testing high-voltage power equipment such as relays. It has many features such as high speed, high precision, safety and reliability. Among them, frequency and high/low cycle tests are frequently required tests for relay protection testers. This article takes the YTC1000 microcomputer relay protection tester as an example to briefly introduce how to set the action frequency and time for frequency and high/low cycle tests of the microcomputer relay protection tester.
The frequency and high/low cycle tests of the microcomputer relay protection tester include test items such as "action frequency" and "action time". According to needs, one or more of them can be selected for testing. When multiple test items are selected, after one test item is completed, a dialog box will pop up to prompt whether to proceed to the next test item.
Action frequency setting:
Action frequency test range
The start and end values of the action frequency test range should be set near the action frequency. The start value should be greater than the protection setting action value, and the end value should be less than the setting action value.
Test method for action frequency: During the test, the frequency changes in two stages: initially output at 50Hz, after the pre-change delay, first slide down (or up) uniformly according to the set df/dt to the start frequency of the test, then decrease (or increase) the frequency step by step at a certain time interval according to the set step size. During this process, if the protection operates, the action value is measured. If it does not operate, when it changes to the end value of the test, it is considered that the protection will not operate and the test of this item ends.
Here, the time interval for step-by-step frequency change is automatically determined based on the set action time. This time interval is 0.2S longer than the set action time. Therefore, the set action time should be set correctly to ensure that the protection has enough time to operate within the change time interval.
For low-cycle load shedding tests, the test range is generally less than 50Hz; for high-cycle generator tripping tests, the test range is generally greater than 50Hz.
For example: If the low-cycle action value is known to be 48.5Hz, the test range can be set to 48.7—48Hz with a step size of 0.05Hz. The start and end values of the test should not be set too small (generally not lower than 45Hz), otherwise the protection will be blocked.
Action time setting:
Test method for action time: The frequency slides down from the start value (generally 50Hz) to the end value and waits for action. The end value should be slightly less than the action frequency value to ensure the device operates, but the timer for testing the action time starts timing from the set "frequency at the start timing point", so any deviation in this value will affect the time measurement accuracy. The test process is shown in the figure on the right.
For the frequency point at which timing starts, when measuring the action time, special attention should be paid to correctly setting the "frequency at the start timing point". Generally, it is set to the action frequency set by the device, or the accurate action frequency value obtained from testing.
Before conducting frequency and high/low cycle tests with the microcomputer relay protection tester, wiring work is required. After wiring is completed, the frequency and time settings should be performed according to the above method. Once set, the test can begin. During the test, close observation is needed, records should be made in a timely manner, and test parameters should be recorded. Only when the settings fully meet the requirements can the instrument achieve the expected test accuracy.
