What is “High-Low Frequency Test”
The ‘High-Low Frequency Test’ module is an essential tool for testing various functions of frequency protection, including low frequency load reduction and high frequency generator shutting. This module is designed to ensure the reliability and accuracy of frequency protection in power systems, which is crucial for maintaining the stability and safety of the grid.
the High-Low Frequency Test Module is one of the basic functions of a relay tester
The module allows for the simulation of frequency variations to test the response of protective relays under different conditions. Here’s a breakdown of the key components and their significance:
Test Items
The module includes six test items: ‘Action Frequency’, ‘Action time’, ‘df/dt block’, ‘dv/dt block’, ‘Low Voltage block’, and ‘Low Current block’. These items are crucial for testing different types of relays, including ‘Low Cycle Protection’, ‘Frequency Relay’, ‘Beat Frequency Relay’, ‘Low Frequency Relay’, and ‘High Frequency Relay’. The selection of these items depends on the specific requirements of the test.
Testing Parameters
Parameters such as ‘Time Delay before Variety of Frequency’ and ‘Test Interval’ are essential for controlling the timing of the tests. The ‘Setting Value’ serves as a reference for comparing the ‘Test Value’ obtained during the test, providing a relative error that reflects the performance of the protection.
Action Frequency
This test mode involves varying the frequency from an initial value to a final value, ensuring that the action frequency is within this range. The frequency is varied in two stages: first, it slips down or up evenly according to df/dt to a frequency slightly above or below the setting action value, and then it descends or rises step by step in a certain time interval.
Action Time
This test mode involves slipping the frequency down or up from the original value to a final value and waiting for the protection to act. The timer for testing action time begins at the ‘Setting Action Frequency’.
df/dt Block and dv/dt Block
These tests involve varying the frequency or voltage, respectively, and measuring the rate of change (df/dt or dv/dt). The original value should be higher than the setting block value, and the final value should be lower to test the boundary value of the block.
Low Voltage Block and Low Current Locking
These tests are similar to the df/dt and dv/dt blocks but focus on voltage and current, respectively. They determine the boundary values at which the protection will block or unlock.
The process of testing involves connecting the tester to the relay, selecting the test item and testing object, setting the testing data, and starting the test. The tester outputs the current real-time frequency, and the protection’s response is observed and recorded.
This module is significant for ensuring the reliability and accuracy of frequency protection in power systems. By simulating various frequency conditions, it allows for the verification of the protective relays’ performance under different scenarios, ensuring that they will operate correctly when needed to maintain the stability and safety of the power grid.