ABB RELION REX640 Technical Manual page 1033

Protection and control

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1MRS759142 F

Figure 574: Short-circuit voltage waveform, fault occurs at time 0 seconds

In a typical impedance trajectory during a short circuit, the fault impedance remains

inside the impedance circle for a longer time, in which case the underimpedance

protection provides longer tripping delay times to maintain the time selectivity.

Technical Manual

Protection functions