Saturation Detector; Ct Saturation Detection - GE B90 Instruction Manual

CHAPTER 9: THEORY OF OPERATION

SATURATION DETECTOR

Figure 9-4: Directional principle operation during external faults
Figure 9-5: Directional principle operation during internal faults
The B90 implementation calculates the maximum angle for the considered currents and compares it against a fixed
threshold of 90°. The flag indicating whether the directional protection principle is satisfied is available as the FlexLogic
operand
BUS 1(4) DIR A/B/C.
9.5 Saturation detector
9

9.5.1 CT saturation detection

The saturation detector of the B90 takes advantage of the fact that any CT operates correctly for a short period of time,
even under very large primary currents that would subsequently cause a very deep saturation. As a result, in the case of
an external fault, the differential current stays very low during the initial period of linear operation of the CTs while the
B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 9-7