ABB Relion 670 series, Technical Manual

Page: 384 / 1432

7.11.6 Monitored data
PID-3539-MONITOREDDATA v7
Table 169: OOSPPAM (78) Monitored data
Name Type Values (Range) Unit Description
CURRENT REAL - A Magnitude of the measured positive-
sequence current, in A
VOLTAGE REAL - kV Magnitude of the measured positive-
sequence voltage, in V
R REAL - % Real part of measured positive-sequence
impedance % of VBase/(sqrt(3)*IBase)
X REAL - % Imaginary part of measured positive-seq
impedance % of VBase/(sqrt(3)*IBase)
SLIPFREQ REAL - Hz Slip frequency in Hz
ROTORANG REAL - deg Rotor angle as estimated by the out-of-
step function
VCOSPHI REAL - kV Estimated Ucos(Phi) voltage during pole
slip, in V
7.11.7 Operation principle
GUID-787EEB01-B760-4D4B-AB4E-1DCD6ABFFF5E v6
General
Under balanced and stable conditions, a generator operates with a constant rotor angle (power
angle), delivering active electrical power to the power system, which is approximately equal to the
input mechanical power on the generator axis.The currents and voltages are constant and stable.
An out-of-step condition is characterized by periodic changes in the rotor angle, that leads to a
wild flow of the synchronizing power; so there are also periodic changes of rotational speed,
currents and voltages. When displayed in the complex impedance plane, these changes are
characterized by a cyclic change in the complex load impedance Z(R, X) as measured at the
terminals of the generator, or at the location of the instrument transformers of a power line
connecting two power subsystems. This is shown in Figure 200 .
Section 7 1MRK 502 066-UUS B
Impedance protection
378
Technical manual