Lens Characteristic - ABB RES670 Technical Manual

1MRK 511 408-UUS A
7.2.7.1
Phasor measurement unit RES670 2.2 ANSI
Technical manual
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
ANSI10000111 V1 EN-US
Figure 44: A stable case where the disturbance does not make the generator to
go out-of-step
It shall be observed that for a stable case, as shown in Figure 44, where the disturbance
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; if the rotor
(power) angle approaches this value, then there is a high risk to have an out of step
condition. The limit-of- reach circle is constructed automatically by the algorithm; it is
about 10% wider than the the circle that has the line SE-RE as diameter (that is the out-
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 →
Figure42
Impedance protection
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
ANSI10000111-1-en.vsd
GUID-F9BD3225-C87F-4FA6-A267-2248F0A4E707 v6
and Figure44, is obtained so
Section 7
161