Line In One Pole Open Condition (During Single-Pole Trip); Conditions For Isolating Lines; Power Swing Inside The Load Blinder Area; Selective Protection Blocking - GE MiCOM P40 Agile Technical Manual

Application Notes
MiCOM P40 Agile P442, P444
• The three impedance points have been in the power swing band for more than 5ms.
• At least two poles of the breaker are closed (impedance measurement possible on two
phases).
Note:
4.1.1.1

Line in one pole open condition (during single-pole trip)

In this case, the power swing occurs only on two phases. A power swing is detected if:
• At least one phase-phase impedance is within the start-up zone after having crossed
the power swing band in more than 5ms.
• The two impedance points have been in the power swing band for more than 5 ms.
Note:
4.1.1.2

Conditions for isolating lines

If there is a power swing, it may be necessary to disconnect the two out-of-step sources.
There are various tripping and blocking options available that are used to select if the line
has to be tripped for power swings or not.
The selective blocking of back up zones only allows the P44x to separate the network near
the electrical zero by tripping zone 1 only. Therefore, in the example given below, the relay D
trips out.
Figure 60: Selective protection blocking
4.1.1.3

Power Swing inside the Load Blinder Area

If the Impedance locus is located in the Load Blinder area (refer to section 4.2), either due to
a Load condition or a Power Swing (detected as previously described) and start to move, the
following alternative calculation for power swing takes place:
Simplified formula:
Power swing condition will be raised if the all three phase to phase impedance loops move
between min and max speed,
With:
Min speed (ohm/Sec) =
Max speed (ohm/sec) = 225 * ( (Delta R + 2*Delta X)/2)
Unblocking delay setting under Power Swing Setting Column in seconds
Delta R (∆R) and Delta X
During Power swing the residual compensation factors k0 are not applied in the
detection of the characteristic.(the extended limit in R gives: R1=R2=R3=RpFwd)
During an open-pole condition, the P44x monitors the power swing on the healthy
phase-phase loop. No external information is needed if the voltage transformers are
on the line side. If the voltage transformers are on the bus side, the "pole discrepancy"
signal should be used. The "pole discrepancy" input represents a "one-circuit-breaker-
pole-open" condition.
B
A
(∆X) Settings under Power Swing Setting Column in ohms
Electrical
Zero
C D
Relay set for out-of-step tripping,
zone 1.
P44x/EN AP/Hb6
(AP) 5-87
E
F
P3039ENa