Lens Characteristic - ABB REG650 Technical Manual

Section 7
Impedance protection
7.3.7.1
154
1
SE
G
0.8
fault
relay
0.6
-
zone 2
-
0.4
-
-
-
-
X-line →
0.2 ^ ^ ^ ^ ^ ^ ^ ^ ^
-
-
- -
0
-
-
limit of
-
-
-0.2 reach
-
zone 1
-
-
- -
-0.4
-0.6
this circle forms
-0.8
the right-hand side
edge of the lens
-1
-1 -0.5
IEC10000111 V1 EN
Figure 70: A stable case where the disturbance does not make the generator to
go out-of-step
It shall be observed that in a stable case, as shown in
does not cause the generator to lose step, the complex impedance Z(R, X) exits the lens
characteristic on the same side (point 4) it entered it (point 2), and never re-enters the
lens. In a stable case, where the protected generator remains in synchronism, the
complex impedance returns to quadrant 1, and, after the oscillations fade, it returns to
the initial normal load position (point 0), or near.

Lens characteristic

A precondition in order to be able to construct a suitable lens characteristic is that the
power system in which OOSPPAM (78) is installed, is modeled as a two-machine
equivalent system, or as a single machine – infinite bus equivalent power system. Then
the impedances from the position of OOSPPAM (78) in the direction of the normal
load flow (that is from the measurement point to the remote system) can be taken as
forward. The lens characteristic, as shown in
that two equal in size but differently offset Mho characteristics are set to overlap. The
resultant lens characteristic is the loci of complex impedance Z(R, X) for which the
rotor (power) angle is constant, for example 110 degrees or 120 degrees; these are the
angles where stability problems are very likely.
lens characteristic for a power system.
RE
X [Ohm]
RE
-
- -
- -
- -
- - -
- - -
-
- - - -
- -
- - -
-
- - -
- - - 4
-
- - -
- - -
-
- - -
- - - -
- -
2
- - -
-
- - 1
- - -
-
- - -
fault →
- -
-
- - 3
- -
- -
-
^ ^ ^ ^ ^ ^ ^ ^ ^
- -
- -
-
- -
- -
Z-line →
- -
- -
- -
- -
- -
-
- -
- -
- -
- - -
- -
- -
-
relay lens → - -
- -
- -
-
- -
110° - - -
- -
-
- - -
- - -
-
- - - - - -
-
- - - - - -
- -
- - - -
- - -
- - - -
- - - -
- -
- -
- - -
SE
0 0.5
Real part (R) of Z in Ohms →
Figure 68
Figure 71
1MRK 502 043-UUS B
Z(R,X) 20 ms
after line out
pre-fault
Z(R,X)
5
0
6
R
0 → pre-fault Z(R, X)
3 → Z(R, X) under fault
5 → Z 20 ms after line out
6 → pow er line reclosed
1 1.5
IEC10000111-1-en.vsd
Figure 70, where the disturbance
and Figure 70, is obtained so
illustrates construction of the
Technical Manual