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Under-/overfrequency relay (application example)

WARNING
Death or severe injury can occur if the appropriate safety instructions are not observed.
  • The COMPANO 100 test set can output life-hazardous voltages and currents.
  • Before operating any such electrical equipment, carefully read the Safety Instructions chapter in this manual (see Safety instructions).

Frequency relays trip when the input frequency shifts away too far from the nominal frequency. Some of these frequency relays suppress very sudden frequency changes as these could result from transient events. Therefore, in this example the frequency relay is tested with a very slow frequency ramp.

Configuration:

  1. Turn off the output I OUT by first pressing the I OUT key, and then by pressing the "Off" soft key.

  2. Voltage output V OUT is configured to be AC by default.

  3. Configure input IN 1 to be a binary input to connect dry (potential-free) or wet contacts (carrying potential when closed), depending on the relay's contact.

  4. Connect voltage output V OUT to the voltage input of the relay, and IN 1 to the trip contact of the relay.

Running the test:

  1. As a first sequence step, in FLEX configure V OUT to nominal voltage at nominal frequency, set the timeout to 5 seconds, and the trigger to "Off".

  2. Add a second sequence step.

  3. Configure the transition from sequence step 1 to sequence step 2 as ramp with f as the value to be ramped.

  4. Set only short frequency steps of say 0.1 Hz or -0.1 Hz, and step times of, for example, 500 ms.

  5. Configure the sequence step with the target frequency, and set the trigger to IN 1.

  6. Start the test.

  7. The result will show the frequency where the trip occurred.

Take into consideration that many overfrequency relays require a certain amount of time to determine the precise frequency value. This may be a time span of up to 200 ms, or more. So make sure that the time per individual ramp sequence step is significantly longer than the time the relay needs to determine the precise frequency value. Refer to the relay's user manual for more information.