ABB REG650 Technical Manual page 150

Section 7
Impedance protection
144
Measured mode Measured apparent impedance
V
Z
posseq
posseq
=
I
posseq
EQUATION2051-ANSI V1 EN
There are three characteristics in LEXPDIS (40) protection as shown in figure 63.
Naimly:
• Offset mho circle for Z1
• Offset mho circle for Z2
• Directional blinder
X
IEC06000455 V2 EN
Figure 63: Three characteristics in LEXPDIS (40) protection
When the apparent impedance reaches the zone Z1 this zone will operate, normally
with a short delay. The zone is related to the dynamic stability of the generator.
When the apparent impedance reaches the zone Z2 this zone will operate, normally
with a longer delay. The zone is related to the static stability of the generator.
LEXPDIS (40) protection also has a directional blinder (supervision). See figure 63.
(Equation 31)
Underexitation protection
Underexcitation Protection
Restrain area
Restrain area
R
R
Directional
blinder
Z1, Fast zone
Z2, Slow zone
IEC06000455-2-en.vsd
1MRK 502 043-UUS B
Technical Manual