where the IN is the fault current level in the faulty phase. A high sensitivity need not to be
achieved as the two-phase fault level normally is well above base current.
tIN: The time delay for detecting that the fault is cross-country. Normal time setting is 0.1
- 0.15 s.
tVN: The time delay for a secure VN detecting that the fault is an ground-fault or double
ground-fault with residual voltage. Normal time setting is 0.1 - 0.15 s.
tOffVN: The VN voltage has a reset drop-off to ensure correct function without timing
problems. Normal time setting is 0.1 s
6.6 Power swing detection ZMRPSB (68)
6.6.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Power swing detection ZMRPSB
SYMBOL-EE V1 EN
68
6.6.2 Application
6.6.2.1 General
Various changes in power system may cause oscillations of rotating units. The most
typical reasons for these oscillations are big changes in load or changes in power system
configuration caused by different faults and their clearance. As the rotating masses strive
to find a stable operate condition, they oscillate with damped oscillations until they reach
the final stability.
The extent of the oscillations depends on the extent of the disturbances and on the natural
stability of the system.
The oscillation rate depends also on the inertia of the system and on the total system
impedance between different generating units. These oscillations cause changes in phase
and amplitude of the voltage difference between the oscillating generating units in the
power system, which reflects further on in oscillating power flow between two parts of the
system - the power swings from one part to another - and vice versa.
1MRK 506 334-UUS A Section 6
Impedance protection
157
Application manual
To Next Page
Loading...
