Negative Sequence Overcurrent Protection Scheme Logic - Toshiba GRE110 Instruction Manual

transformer energisation, and can block the NPS1 and NPS2 elements by the scheme switches
[NPS1-2F] and [NPS2-2F] respectively. See section 2.9.
79
NPS1
[NPS1-2F]
+
"Block"
&
ICD
[NPS1EN]
+
"ON"
80
NPS2
[NPS2-2F]
+
"Block" &
ICD
[NPS2EN]
+
"ON"
NPS BLOCK
Figure 2.6.1 Negative Sequence Overcurrent Protection Scheme Logic
The tripping and alarming can be disabled by scheme switches [NPS1], [NPS2] or binary input
signal NPS BLOCK.
Settings
The table below shows the setting elements necessary for the NSOP protection and their setting
ranges.
Element Range
NPS1 0.10 -10.0 A
NPS2 0.10 -10.0 A
TNPS1 0.00 – 300.00 s
TNPS2 0.00 – 300.00 s
[NPS1EN] Off / On
[NPS2EN] Off / On
Sensitive setting of NPS1 and NPS2 thresholds is restricted by the negative phase sequence current
normally present on the system. The negative phase sequence current is measured in the relay
continuously and displayed on the metering screen of the relay front panel along with the maximum
value. It is recommended to check the display at the commissioning stage and to set NPS1 and
NPS2 to 130 to 150% of the maximum value displayed.
The delay time setting TNPS1 and TNPS2 is added to the inherent delay of the measuring elements
NPS1 and NPS2. The minimum operating time of the NPS elements is around 200ms.
&
0.00 - 300.00s
&
0.00 - 300.00s
1
Step Default
0.01 A 0.40 A
0.01 A 0.20 A
0.01 s 0.00 s
0.01 s 0.00 s
Off
Off
 39 
TNPS1
0
t
TNPS2
0
t
Remarks
NPS1 threshold setting for tripping.
NPS2 threshold setting for alarming.
NPS1 definite time setting
NPS2 definite time setting
NPS1 Enable
NPS2 Enable
6 F 2 T 0 1 7 2
136
NPS1 TRIP
137
NPS2 ALARM