8-12 B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
ENHANCING RELAY PERFORMANCE CHAPTER 8: APPLICATION OF SETTINGS
8
The lower breakpoint (LOW BPNT) could be increased to 4.58 pu (fifth column of the Limits of Linear Operations of the CTs
table). The higher slope (
HIGH SLOPE) could be decreased as no AC saturation is possible for the South bus CTs (see the
external fault calculation tables for each circuit).
The concept could be implemented by using:
• FlexLogic to process the status signals in order to identify the weakest CT
• Setting Groups to switch dynamically from one setting group to another (adaptive settings)
This approach can be extended for buses that do not require the dynamic bus replica mechanism. This can include
approximation of the total bus fault current using positions of all switches and breakers and optimizing the settings
depending on the amount of stress imposed on the CTs in any particular bus configuration.
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