Description of the User Interface SCT5xxx
The SCT5xxx have three user selectable parameters, for each of which 3-5 different values can be selected. The simple and intuitive user interface is located on the top of the device and is used to configure the transformer with three buttons located below the interface. These buttons can only be operated with a tool that prevents unintentional and unauthorized access in accordance with the applicable product standards. The interface also has a test button and a status LED for visual indication.
1. Power-on/ Status LED
The LED lights up green with heartbeat characteristic*) during normal operation with low residual currents. If the color changes to red with heartbeat characteristic, the measured TRMS residual current is higher than the rated RC limit.
The LED flashes green during start-up. Continuous red light in combination with several flashing green LEDs of the "Rated RC limit" group indicates an error state.
*) The light intensity of the status LED changes continuously with a heartbeat characteristic to signal the correct execution of the software and to indicate that the SCT is in correct operational mode. |
2. Error codes
LEDs (flashing), left group | Diagnosis |
|---|---|
2x | Input voltage outside permissible range |
3x | Relay activated too often |
4x | Overtemperature |
5x | Internal error |
3. Test button
The test button is used to activate the test sequence for testing the operation of the SCT. If the test is successful, the relay is activated and the LED lights up red.
If the relay is locked due to too many activations, pressing the button for 3 seconds will reset the state when the differential current is normal.
4. Rated RC limit (RL)
The rated RC limit (RL) refers to the measured TRMS value of the residual current that will trip the relay output. Additionally, selecting the three lower trip limits (30-100-300 mA) changes the analog output range to 0 - 0.4 Arms, while selecting the two upper trip limits (500 - 1000 mA) changes the analog output range to 0 - 2 Arms.
Notes:
- Set the RL low if necessary to get early warning of increasing residual current values.
- To avoid false alarms, set RL to higher values that correspond to the residual current levels the user can tolerate in the electrical power system before system testing or maintenance is required.
5. Frequency range (FR)
Refers to the measurement bandwidth for the differential current.
Notes:
- If only DC and low frequency AC (50 / 60 Hz) are of interest, use the 100 Hz setting.
- If protection of frequency converters in switching mode is mandatory, increase FR towards 2 kHz, 20 kHz or even full bandwidth 100 kHz.
6. Integration time (IT)
Refers to the time window for the calculation of the TRMS value.
Notes:
- A longer IT makes the SCT less sensitive to short peaks during start-up; better for low-frequency operation
- Shorter integration times result in a faster response of the SCT, especially when short residual current pulses are of interest.