Alstom MiCOM P545 - 2.3.15 Power swing alarming and blocking (Distance option only)

Application Notes P54x/EN AP/La4
MiCOM P543, P544, P545 & P546
(AP) 6-23
AP
Figure 5 shows the typical application of the Basic scheme.
Typical application
A
B
Z
Z
Zone 1
Zone 2
Zone 3
Zone 1
Zone 2
Zone 3
TZP
TZ2
TZ3
TZ4
Z1
ZP
Z2
Z3
Z4
Relay A
1
Trip A
TZP
TZ2
TZ3
TZ4
Z1
ZP
Z2
Z3
Z4
Relay B
1
Trip B
Note: All timers can be set instantaneous
TZ1
TZ1
P1144ENb
Figure 5 Basic time stepped distance scheme (Distance option only)
2.3.15 Power swing alarming and blocking (Distance option only)
The PSB technique em
ployed in the MiCOM P54x has the significant advantage that it is
adaptive and requires no user-set thresholds in order to detect swings faster than 0.5 Hz.
The PSB relies on the delta techniques internal to the relay, which automatically detect
swings. During the power oscillations slower than 0.5 Hz the continuous ∆I phase current
integral to the detection technique for swing conditions may fall below the sensitive threshold
of ∆I=0.05 In therefore may not operate. These slow swings will usually occur following
sudden load changes or single pole tripping on the weaker systems where the displacement
of initial power transfer is not severe. The slow swings of up to 1 Hz are by its nature
recoverable swings but the swing impedance may stay longer inside the distance
characteristics until the oscillations are damped by the power system. Therefore, to
guarantee system stability during very slow swings it is recommended to set a blinder to
complement the automatic, setting free detection algorithm. Zone 5 is used as a blinder for
slow swing detection as well as for the Out of Step (OST) protection described in the next
section. Zone 5 settings are therefore visible even if OST protection is disabled. The slow
swing condition will be declared if positive sequence impedance is detected inside zone 5 for
more than a cycle without phase selection operation. The slow swing detection operates in
parallel to automatic swing detection mechanism.
No system calculation is needed for zone 5 setting, it is only important to set zone 5 smaller
than the minimum possible load impedance with a security margin: