Power and Voltage Quality Trainer
AD 2
– MI 3399
130
Since swells usually last for a short period, there is no significant impact on equipment.
However, light bulbs can burn out and safety problems may arise.
Figure 2-2: voltage swell
2.5 Voltage interruptions
An interruption is classified as a network’s isolation from any source of supply. Because
of energy stored in a network, a specific voltage above zero, exists for a short period
after the interruption commences. For this reason an interruption is detected as a
U
rms(1/2)
drop below an interruption threshold. The interruption threshold can vary but is
usually set to 1%, 5% or 10% of the declared voltage. The duration of an interruption
is measured in the same manner as a measurement of dip duration after setting an
interruption threshold.
Because of the measurement technique a short circuit fault can appear as a short
interruption in one section of the network and a dip in another. Interruptions are
classified in two groups:
short interruptions
long interruptions.
Origin
Short interruptions are introduced by a fault condition in a network, which causes
switchgear to operate. The duration of a short interruption is limited to 1 minute or 3
minutes.
Long interruptions are interruptions in excess of the short interruption duration limit.
They arise when a fault condition cannot be terminated with a control sequence and
the final tripping of a circuit breaker occurs.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
-800
-600
-400
-200
0
200
400
600
800
Summary of Contents for MI 3399
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