Toshiba GRT100 Series Instruction Manual page 14

Protection by DIF and HOC can perform instantaneous three-phase tripping of up to five
breakers. Any of the five breaker tripping signals DIFT-1 to DIFT-5 are enabled or disabled by
the scheme switch [DIF1] to [DIF5] settings.
Setting
Scheme
Sensitivity of 2F and 5F element
Scheme logic
Response against magnetizing
inrush
Detection at internal fault
Application
DIFT
HOC-A
HOC-B
HOC-C
DIF-A
DIF-B
DIF-C
&
2f-A
2f-B &
2f-C
&
5f-A &
5f-B
&
5f-C
&
2f-Lock
+
"ON"
5f-Lock
+
"ON"
phases of 2F element.
Table 2.3.1 Blocking Scheme during Magnetising inrush
2PAND
Even if 2F or 5F element operates during
manetising inrush, the trip by DIF element is
allowed when any two phases or more of DIF
element operate.
No problem:
When second or fifth hartmonic component
of any two phases is lower than their
sensitivity setting, the DIF may operate.
No problem
The "2PAND" is recommended for a
transformer with small or midium capacity
whose second harmonic component in
inrush current is genarally higher than that of
transformer with large capacity.
1
&
&
&
1
1
1
1
1
1
DIFTPMD
+
1
1
&
1
1
Figure 2.3.2 Scheme Logic of Current Differential Protection
 13 
When any one phase of 2F or 5F element
operates during manetising inrush, the trip by
DIF element is blocked.
 10 to 50% or I
I /I /I
2f 1f 5f
Refer to Figure 2.3.2
No problem:
When second or fifth hartmonic component of
any one phase is higher than their sensitivity
setting, the DIF is surely blocked.
No problem
The "3POR" is recommended for a transformer
with large capacity whose second harmonic
component in inrush current is generally lower.
This block function is stronger than that of the
"2PAND".
&
&
&
&
&
&
& &
&
&
&
&
3POR
1
&
2PAND
6 F 2 S 0 7 8 9
3POR
 10 to 50%
1f
TRIP
&
1
DIF1
+
"ON"
&
DIF2
+
"ON"
1 1
&
DIF3
+
"ON"
&
DIF4
+
"ON"
1
&
DIF5
+
"ON"
DIFT-1
DIFT-2
DIFT-3
DIFT-4
DIFT-5