Toshiba GRZ100 B Series, Instruction Manual

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6 F 2 S 0 8 4 6
2.5.10 Fault Detector Elements
The fault detector incorporates the following six fault detection elements.
Multi-level overcurrent element OCMF
The OCMF is used as a fault detector for the out-of-step protection.
The current fluctuates in an out-of-step situation. To detect this current securely, the OCMF has
seven current level detectors. Each current level detector LD1 to LD7 operates when the current
exceeds each setting L1 to L7 and resets when the current falls below 80 % of the setting. The
settings are fixed as shown in Table 2.5.10.1 as a ratio to the rated current In.
Table 2.5.10.1 Level Detector Settings
Detector Operate Reset
LD1 0.10
×
In 0.08
×
In
LD2 0.16
×
In 0.13
×
In
LD3 0.26
×
In 0.21
×
In
LD4 0.41
×
In 0.33
×
In
LD5
0.66
×
In 0.53
×
In
LD6 1.05
×
In 0.84
×
In
LD7 1.68
×
In 1.34
×
In
(In: Rated current)
Figure 2.5.10.1 shows the characteristics of the OCMF element.
L1 L2
I 0
L7 L6 L5 L4
L3
D.O./P.U.=0.8
Figure 2.5.10.1 OCMF Element
Figure 2.5.10.2 shows the OCMF output logic. The OCMF operates and keeps operating for five
seconds when any of the level detectors operate and reset without time delay when all of the level
detectors reset.
The level detection is performed for phase-to-phase current on A- and B-phase.