25-07-2012, 03:28 PM
Line Voltage Stability Calculations in Power Systems
Line Voltage Stability.pdf (Size: 473.82 KB / Downloads: 54)
INTRODUCTION
Modern power systems have been recently
operating close to network stability limits due to
deregulation in the electricity market and the complex
nature of establishing new transmission lines, causing
violation in system voltage profile limits. Operating power
systems under such condition initiates a sequence of voltage
instability points leading power system to voltage collapse
events. Inadequate reactive power supplies may also
contribute to system voltage collapse and, then to electricity
blackouts. Several electricity blackouts were registered
globally. Examples include France in 1978, Sweden in
1983, in Japan in 1987 [1], in the USA in 1996 and 2003
[2,3], Italy in 2003[3], and England in 2003[3].
REVIEW ON LINE STABILITY INDEX
This section briefly discusses line stability index,
Lmn [15] which is used as a base method for comparison
purposes with the proposed method, VQILine.
Lmn is a line power index used to calculate line voltage
stability. This index detects the stressed condition of power
system lines and determines the weak areas susceptible to
voltage collapse, providing online system stability
prediction.
CONCLUSIONS
This paper presented a novel voltage stability analysis
based on transmission line system, accurately determining
voltage stability analysis at each line and precisely
predicting the points of voltage collapse on power systems.
The proposed method, VQILine, indicates how far the line is
from a severe load condition or collapse point, permitting
separate analysis if one line is highly stressed. VQILine is
designed to have a direct association between sending line
voltages and line receiving reactive powers, giving more
efficient stability analysis, particularly when a power
system is subjected to an unexpected increase in load
reactive powers. The accuracy of VQILine to carry out line
voltage stability analysis and predict voltage collapse were
tested, showing almost identical voltage stability margins
and the same system voltage collapse points when
compared to the existing methods.