VEGA
76
EN - 49
16. APPENDIX 3 – THEORETICAL OUTLINES
16.1. VOLTAGE ANOMALIES (VOLTAGE SAG AND SURGE)
VEGA 76 is able to record as voltage anomalies all those rms values, calculated every
10ms, beyond the percentage thresholds of the Voltage Reference (Vref) set during the
programming from
±
1% to
±
30 % (with step of 1%).
The Reference must be set to:
Nominal Voltage Phase to Neutral:
for Single Phase and 4-wire three phase system
Nominal Voltage Phase to Phase:
for 3-wire three phase system
Example1: Three Phase System 3-wire.
Vref = 400V, LIM+= 6%, LIM-=10% =>
High Lim = 400 x (1+6/100) = 424,0V
Low Lim = 400 x (1-10/100) = 360
Example2: Three Phase System 4-wire.
Vref = 230V, LIM+= 6%, LIM-=10% =>
High Lim = 230 x (1+6/100) = 243,08V
Low Lim = 230 x (1-10/100) = 207,0V
The Instrument will detect Voltage Anomalies if the RMS Voltage Values (calculated every
10ms) are beyond the above calculated thresholds. These limits remain unchanged
throughout the recording period.
When a Voltage anomaly occurs the instrument records:
•
The number corresponding to the phase where the anomaly occurred.
•
The “direction” of the anomaly: “UP” and “DN” identify respectively voltage drops (sag)
and peaks (Surge).
•
The date and time of the beginning of the event in the form day, month, year, hour,
minutes, seconds, hundredths of second.
•
The duration of the event, in seconds with a resolution of 10ms.
•
The minimum (or maximum) value of voltage during the event.
16.2. VOLTAGE AND CURRENT HARMONICS
16.2.1. Theory
Any periodical non-sinusoidal wave can be represented as a sum of sinusoidal waves
having each a frequency that corresponds to an entire multiple of the fundamental,
according to the relation:
)
t
sin(
V
V
v(t)
k
k
1
k
k
0
ϕ
ω
+
+
=
∑
∞
=
(1)
where:
V
0
= Average value of v(t)
V
1
= Amplitude of the fundamental of v(t)
V
k
= Amplitude of the k
th
harmonic of v(t)
In the mains voltage, the fundamental has a frequency of 50 Hz, the second harmonic has
a frequency of 100 Hz, the third harmonic has a frequency of 150 Hz and so on.
Harmonic
distortion is a constant problem and should not be confused with short events such as
sags, surges or fluctuations.
Summary of Contents for VEGA 76
Page 1: ...Copyright HT ITALIA 2004 Release EN 2 00 08 06 2004 VEGA 76 User s Manual...
Page 2: ......
Page 59: ...YAMUS0003HT0...
