ÇUKUROVA UNIVERSITY INSTITUTE OF NATURAL AND APPLIED ...

2. POWER QUALITY Mustafa İNCİ
2.2.6. Transients
A transient is “that part of the change in a variable that disappears
during transition from one steady state operating condition to another”. Another
word in common usage that is often considered synonymous with transient is
“surge” (Dugan et al, 2003). Transients can be be classified into two categories:
“impulsive” and “oscillatory”:
• Impulsive transients: Sudden, non-power frequency change in the steady
state condition of the voltage, current or both
• Oscillatory transients: Voltage or current whose instantaneous value
changes polarity rapidly.
2.2.7. Interruption
In the European standard EN 50160 two terms are used (Nielsen et al., 2002):
• Long interruptions: longer than three minutes.
• Short interruptions: up to three minutes.
Interruptions are typically caused by different types of faults e.g. malfunction
of protection equipment or lightning. In a system without redundancy a fault often
leads to a long interruption, which requires manual intervention. Short interruptions
are often caused by automatic reclosing after a fault. Short interruptions below three
minutes are normally considered a voltage quality problem. Interruptions are a severe
power quality problem, but in a wide range of industrial countries interruptions occur
very rare, because of redundancy and high maintenance of the grid (Nielsen et al.,
2002).
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