ABB RELION REX640 Technical Manual page 692

Protection and control

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Protection functions

Figure 393: Setting range for biased low stage

If the biasing current is small compared to the differential current of the phase

angle between the winding 1 and winding 2 phase currents is close to zero (in

a normal situation, the phase difference is 180 degrees), a fault has most likely

occurred in the area protected by TR2PTDF. Then the internal blocking signals of the

biased stage are inhibited.

Instantaneous high stage

The instantaneous high stage operation can be enabled and disabled with the

Enable high set setting. The corresponding parameter values are "TRUE" and

The operation of the instantaneous high stage is not biased. The instantaneous

stage operates and the output OPR_HS is activated when the amplitude of the

fundamental frequency component of the differential current exceeds the set

operate value or when the instantaneous value of the differential current exceeds

2.5 times the value of

maximum asymmetric short circuit current.

If the biasing current is small compared to the differential current or the phase

angle between the winding 1 and winding 2 phase currents is close to zero (in a

normal situation, the phase difference is 180 degrees), a fault has occurred in the

area protected by TR2PTDF. Then the operation value set for the instantaneous

stage is automatically halved and the internal blocking signals of the biased stage

are inhibited.

High operate value . The factor 2.5 (=1.8 × √2) is due to the

1MRS759142 F

Technical Manual