Automatic setup

The Beckhoff SCT5xxx are capable of performing automatic setup of the user selectable settings for installations in proper condition taken as baseline. This means that during automatic setup, the SCT5xxx automatically measures the residual currents at the plant site with different frequency ranges and integration time settings and selects the nominal residual current limit that is at least 50% higher than the measured value.

In this way, the SCT5xxx operate with a comfortable margin for the future development of the measured residual current towards the trip limit of the relay. The automatic setting also suggests a suitable frequency range and integration time.

Required steps:

• Activate the auto setting by pressing the "Rated RC limit" and "Integration time" buttons simultaneously for more than 3 seconds.
• The device performs a series of differential current measurements with different settings.
• Proposed settings for "Rated RC limit", "Frequency range" and "Integration time" are marked with flashing LEDs.
• The proposed change of settings should be accepted by pressing the "Test" button.
• If the change is not accepted within 10 s, the RCM returns to the old settings.

Manual setting of the 100 Hz range The frequency range of 100 Hz is not included in the automatic setting, i.e. the user must select it manually. The SCT5xxx always prefers the settings that make the instrument more sensitive, i.e. higher frequency ranges and shorter integration times.