Page 179 - Power Quality in Electrical Systems

Power Quality Events 161

Voltage
Rated voltage

Normal operation
V tr

Malfunction
(restarting/rebooting)

T tr Time
Figure 11.6 Rectangular voltage-time tolerance curve of
a personal computer [11.2].
[© 2005, IEEE, reprinted with permission]

Figure 11.6 [11.2]. Depending upon the PC, the voltage V ranges from
tr
a low of 30 to 40 percent to a high of 80 to 90 percent. The test results
for a specific PC are shown in Figure 11.7 as a function of the mal-
function of the PC. For restart/rebooting, the interruption can last
380 ms, or 23 cycles. A longer voltage sag can extend down to 20 percent
of the rated voltage [11.2].
Tests of the effects of typical utility power disturbances were made on
a PC LAN test system shown in Figure 11.8 [11.5]. Disturbance signals
were introduced to the line supplying the LAN. The response of the PCs
is shown in Figure 11.9 [11.5].

100
90 Read/write operation lookup
OS blockage
80
Restart/rebooting
70
Voltage, (%) 60
50
40
30
20
10
0
0 50 100 150 200 250 300 350 400 450 500
Time, (ms)
Figure 11.7 Voltage-time tolerance curve for personal com-
puter as a function of failure mode [11.2].
[© 2005, IEEE, reprinted with permission]