Alstom MiCOM P54 Series, Техническое руководство, Страница: 221 / 1024

Operation P54x/EN OP/La4
MiCOM P543, P544, P545 & P546
(OP) 5-47
OP
Other setting possibilities are:

Selection of PSB as “Indication” only will raise an alarm, without blocking any zones.

The
PSB Unblock Dly
function allows for any power swing block to be removed after a
set period of time. For a persistent swing that does not stabilize, any blocked zones will
be made free to trip once the timer has elapsed. In setting which relays will unblock, the
user should consider which relay locations are natural split points for islanding the power
system.

The
PSB Reset Delay
is a time delay on drop-off timer, which maintains the PSB
detection even after the swing has apparently stabilized. It is used to ensure that where
the swing current passes through a natural minimum and delta I detection might reset,
that the detection does not drop out/chatter. It can therefore be used to ensure a
continual Power Swing indication when pole slipping (an unstable out of step condition)
is in progress.
A simplified logic diagram showing operation of the power swing blocking is attached as
Figure 26 which follows.
I Pickup
Any Distance Start
P1654ENa
&
t
0
t
0
3 Cycles
PSB Reset
Delay
&
Fault during swing logic
t
0
Blocking of
selected
distance
zones
PSB Timeout
D
Figure 26 Power swing blocking (Distance option only)
1.20 Out of step detection and tripping (Distance option only)
Out of Step protection is used to split the power system into possibly stable areas of
generation and load balance during unstable power oscillations. The points at which the
system should be split are determined by detailed system stability studies.
The P54x Out of Step function has 4 different setting options:
1. Disabled
2. Predictive OST
3. OST
4. Predictive OST or OST
When set ‘Disabled’, Out of Step function is not operational. The P54x also provides an
option to split the system in advance by selecting the ‘Predictive OST’ (sometimes called an
early OST) in order to minimize the angle shift between two ends and aid stability in the split
areas. The third setting option is to split the system on detection of the out of step condition
i.e. when a pole slip occurs. The fourth option is a combination of the two.
1.20.1 Out of step detection (Distance option only)
The Out of Step detection is based on the well proven ∆ Z/ ∆ t principle associated with two
concentric polygon characteristic, as presented in Figure 27.