Ieee std 1159-1995, ieee recommended Practice for Monitoring Electric Power Quality

Table 2ÑCategories and typical characteristics of power system 
electromagnetic phenomena
Categories
Typical spectral 
content
Typical duration
Typical voltage 
magnitude
1.0 Transients
1.1 Impulsive
1.1.1 Nanosecond
5 ns rise
< 50 ns
1.1.2 Microsecond
1 
ms rise
50 nsÐ1 ms
1.1.3 Millisecond
0.1 ms rise
> 1 ms
1.2 Oscillatory
1.2.1 Low frequency
< 5 kHz
0.3Ð50 ms
0Ð4 pu
1.2.2 Medium frequency
5Ð500 kHz
20 
ms
0Ð8 pu
1.2.3 High frequency
0.5Ð5 MHz
5 
ms
0Ð4 pu
2.0 Short duration variations
2.1 Instantaneous
2.1.1 Sag 
0.5Ð30 cycles
0.1Ð0.9 pu
2.1.2 Swell
0.5Ð30 cycles
1.1Ð1.8 pu
2.2 Momentary
2.2.1 Interruption
0.5 cyclesÐ3 s
< 0.1 pu
2.2.2 Sag 
30 cyclesÐ3 s
0.1Ð0.9 pu
2.2.3 Swell
30 cyclesÐ3 s
1.1Ð1.4 pu
2.3 Temporary
2.3.1 Interruption
3 sÐ1 min
< 0.1 pu
2.3.2 Sag 
3 sÐ1 min
0.1Ð0.9 pu
2.3.3 Swell
3 sÐ1 min
1.1Ð1.2 pu
3.0 Long duration variations
3.1 Interruption, sustained
> 1 min
0.0 pu
3.2 Undervoltages
> 1 min
0.8Ð0.9 pu
3.3 Overvoltages
> 1 min
1.1Ð1.2 pu
4.0 Voltage imbalance
steady state
0.5Ð2%
5.0 Waveform distortion
5.1 DC offset
steady state
0Ð0.1%
5.2 Harmonics
0Ð100th H
steady state
0Ð20%
5.3 Interharmonics
0Ð6 kHz
steady state
0Ð2%
5.4 Notching
steady state
5.5 Noise
broad-band
steady state
0Ð1%
6.0 Voltage ßuctuations
< 25 Hz
intermittent
0.1Ð7%
7.0 Power frequency variations
< 10 s

---

IEEE
MONITORING ELECTRIC POWER QUALITY
Std 1159-1995
13
4.4.1.1 Impulsive transient
An impulsive transient is a sudden, nonpower frequency change in the steady-state condition of voltage, cur-
rent, or both, that is unidirectional in polarity (primarily either positive or negative).
Impulsive transients are normally characterized by their rise and decay times. These phenomena can also be
described by their spectral content. For example, a 1.2/50 
ms 2000 V impulsive transient rises to its peak
value of 2000 V in 1.2 
ms, and then decays to half its peak value in 50 ms [B14].
The most common cause of impulsive transients is lightning. Figure 1 illustrates a typical current impulsive
transient caused by lightning.
Due to the high frequencies involved, impulsive transients are damped quickly by resistive circuit compo-
nents and are not conducted far from their source. There can be signiÞcant differences in the transient char-
acteristic from one location within a building to another. Impulsive transients can excite power system
resonance circuits and produce the following type of disturbanceÑoscillatory transients.
4.4.1.2 Oscillatory transient
An oscillatory transient consists of a voltage or current whose instantaneous value changes polarity rapidly.
It is described by its spectral content (predominant frequency), duration, and magnitude. The spectral con-
tent subclasses deÞned in table 2 are high, medium, and low frequency. The frequency ranges for these clas-
siÞcations are chosen to coincide with common types of power system oscillatory transient phenomena.
As with impulsive transients, oscillatory transients can be measured with or without the fundamental fre-
quency component included. When characterizing the transient, it is important to indicate the magnitude
with and without the fundamental component.
Oscillatory transients with a primary frequency component greater than 500 kHz and a typical duration mea-
sured in microseconds (or several cycles of the principal frequency) are considered high-frequency oscilla-
tory transients. These transients are almost always due to some type of switching event. High-frequency
oscillatory transients are often the result of a local system response to an impulsive transient.