Alstom MiCOM P546 - 1.31 Negative sequence overcurrent protection (NPS)

Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546 (OP) 5-87
OP
CTS Block
IN> Protection
Inhibit
IN Derived/Measured
> Setting
NPS Polarizing
Voltage V2>
Slow VTS
Block
EF Timer Block
IDMT/DT
EF Start
EF Trip
P1630ENb
&
&
&
NPS Polarizing
Current I2>
Directional
Check
&
Figure 58 Directional EF with negative sequence polarization (single stage)
The directional criteria with negative sequence polarization is given below:
Directional forward
-90° < (angle(I2) - angle(V2 + 180°) - RCA) < 90°
Directional reverse
-90° > (angle(I2) - angle(V2 + 180°) - RCA) > 90°
1.31 Negative sequence overcurrent protection (NPS)
The n
egative phase sequence overcurrent protection included in the P54x relays provides
four-stage non-directional/ directional overcurrent protection with independent time delay
characteristics. The first two stages of overcurrent protection have time-delayed
characteristics which are selectable between inverse definite minimum time (IDMT), or
definite time (DT). The third and fourth stages have definite time characteristics only. The
inverse time delayed characteristics support both IEC and IEEE curves and please refer to
section 1.25 for a detailed description. The user may choose to directionalize operation of
the elements, for either forward or reverse fault protection for which a suitable relay
characteristic angle may be set. Alternatively, the elements may be set as non-directional.
For the negative phase sequence directional elements to operate, the relay must detect a
polarizing voltage above a minimum threshold, 2> V2pol Set. When the element is
selected as directional, a VTS Block option is available. When the relevant bit is set to 1,
operation of the Voltage Transformer Supervision (VTS), will block the stage if
directionalized. When set to 0, the stage will revert to non-directional upon operation of the
VTS.
When enabled, the following signals are set by the negative sequence O/C logic according to
the status of the monitored function.
I2> Inhibit (DDB 562) - Inhibit all 4 stages when high
I2>1 Tmr. Block (DDB 563) - Block timer on 1st stage when high
I2>2 Tmr. Block (DDB 564) - Block timer on 1st stage when high
I2>3 Tmr. Block (DDB 565) - Block timer on 1st stage when high
I2>4 Tmr. Block (DDB 566) - Block timer on 1st stage when high
I2>1 Start (DDB 567) - 1st stage started when high