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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 A
, while selecting the two upper trip limits (500 - 1000 mA) changes the analog output range to 0 -
rms
2 A
.
rms
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.
SCT5xxx
Version: 1.0
Commissioning
35
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