Calculating Settings For Four Step Residual Overcurrent Protection Hv-Side Ef4Ptoc - ABB Relion 650 Series Applications Manual

1MRK 504 124-UEN B
This current is smaller than the required minimum setting to avoid unwanted trip at large
load current. This means that the 22 kV phase overcurrent protection cannot serve as
complete back-up protection for the 22 kV feeders out from the substation.
2. Set
The feeder short circuit protections have the following setting:
I>: 300 A.
I>>: 6 000 A.
Characteristic: IEC Normal Inverse with k-factor = 0.25
The setting of the k-factor for the 22 kV phase overcurrent protection is derived from
graphical study of the inverse time curves. It is required that the smallest time difference
between the inverse time curves is 0.4 s. With the setting
between the characteristics is about 0.4 s as shown in figure 17.
IEC09000453 V1 EN-US
Figure 17:
3.1.8 Calculating settings for four step residual overcurrent
protection HV-side EF4PTOC
The protection is fed from the 145 kV neutral point of the current transformer.
The residual overcurrent protection is more difficult to set as the earth-fault current is highly
dependent of the switching state in the power system. In order to achieve setting that assure
selective fault clearance a large number of calculations have to be made with different fault
Transformer protection RET650
Application manual
k4 to 0.15
Inverse time operation characteristics for selectivity
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RET650 setting examples
k4 = 0.15 the time margin
GUID-10261D4A-12EE-44C7-9638-DDB40A52F6EF v2
Section 3
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