P.3.166
SEL-411L Relay Protection Manual Date Code 20151029
Protection Functions
Out-of-Step Logic (Zero Settings)
The purpose of the starter zone is to reduce the sensitivity of the power-swing
detector by allowing the PSB elements to assert only for those trajectories of
the positive-sequence impedance (Z1) that could possibly move into the
characteristic of any distance element during a power swing. The area of the
starter zone is a rectangle that encompasses all the distance characteristics that
must be blocked during a power swing, as shown in Figure 3.103.
Furthermore, if the out-of-step tripping (OST) is enabled, the starter zone also
encompasses the largest relay characteristic set for the OST logic (Zone 7; see
Out-of-Step Tripping (OST)—Zero Settings Element). The algorithm
automatically calculates the Starter Zone from the Z2MP–Z5MP, XP2–XP5,
and RP2–RP5 Group settings, using the following equations:
R_SZ = max (2 • 2P, OOSB2, 1.5 • Z3P, OOSB3, 1.5 • Z4P, OOSB4, 1.5 •
Z5P, OOSB5)
X_SZ = max (3 • Z2P, OOSB2, 2 • Z3P, OOSB3, 2 • Z4P, OOSB4, 2 • Z5P,
OOSB5)
Figure 3.103 Starter Zone Characteristic
The slope detector typically detects the majority of power-swing conditions.
However, there are some system conditions for which the slope detector may
not operate. To ensure correct relay power-swing operation, the OSB function
also includes two additional detectors: a swing signature detector and a
dependable PSB detector.
The Swing Signature
Detector
The swing signature detector (SSD) complements the slope detector and
supplements the dependable PSB logic. To distinguish a power swing from a
system fault, the swing signature detector uses the combination of a step
change in the system voltage and the assertion of distance-element-based
protection elements (see Figure 3.104).
Figure 3.104 Swing Signature Detector Logic
AND 1
SSD
Swing Signature Based
on Values of | dSCV1 |
Stored in a Memory Buffer
Distance-Element-Based
Fault Detection
To Next Page
Loading...
