Current Protection: Negative Phase Sequence Overcurrent (46Nps); Figure 3.7-1 Logic Diagram: Negative Phase Sequence Overcurrent (46Nps) - Siemens 7SR224 Description & Operation

(1) Description of Operation 7SR224
3.7 C P
URRENT
The negative sequence phase (NPS) component of current (I2) is derived from the three phase
currents. It is a measure of the quantity of unbalanced current in the system.
Two NPS current elements are provided – 46IT and 46DT.
The 46IT element can be configured to be either definite time lag (DTL) or inverse definite minimum
time (IDMT),
46IT Setting sets the pick-up current level for the element.
A number of shaped characteristics are provided. An inverse definite minimum time (IDMT)
characteristic is selected from IEC and ANSI curves using 46IT Char. A time multiplier is applied to the
characteristic curves using the 46IT Time Mult setting. Alternatively, a definite time lag delay (DTL)
can be chosen using 46ITChar. When Delay (DTL) is selected the time multiplier is not applied and
the 46IT Delay (DTL) setting is used instead.
The 46IT Reset setting can apply a, definite time delayed or ANSI (DECAYING) reset.
The 46DT element has a DTL characteristic. 46DT Setting sets the pick-up current and 46DT Delay
the follower time delay.
Operation of the negative phase sequence overcurrent elements can be inhibited from:
Inhibit 46IT
Inhibit 46DT
46IT Element
Enabled
Disabled
Inhibit 46IT
IL1
IL2 NPS
IL3
46DT Element
Enabled
Disabled
Inhibit 46DT
Figure 3.7-1
Page 32 of 66
: N
ROTECTION EGATIVE
A binary or virtual input.
A binary or virtual input.
46IT Setting
46IT Char
46IT Time Mult
46IT Delay (DTL)
46IT Reset
c
&
I2
&
c
Logic Diagram: Negative Phase Sequence Overcurrent (46NPS)
P S
HASE EQUENCE
Pickup
trip
46DT Setting
46DT Delay
>
c
©2009 Siemens Protection Devices Limited
O (46NPS)
VERCURRENT
General Pickup
46IT
General Pickup
46DT