YOKOGAWA WT500 User Manual page 323

Measurement Functions
Used in Normal
Measurement
Wiring system
WP
WP [Wh]
WP+
WP–
q
q [Ah]
q+
q–
WS [VAh]
WQ [varh]
[°]
IM 760201-01E
Appendix 1 Symbols and Determination of Measurement Functions
Methods of Computation and Determination
For information about the symbols in the equations see the notes.
Single-phase, Three-phase,
three-wire three-wire
1P3W 3P3W
WP1 + WP2
When the watt-hour integration method for each polarity is
Charge/Discharge
WP+1 + WP+2
When the watt-hour integration method for each polarity is Sold/Bought
WP+ is the sum of the positive active power WPS values at each data
update interval.
When the watt-hour integration method for each polarity is
Charge/Discharge
WP–1 + WP–2
When the watt-hour integration method for each polarity is Sold/Bought
WP- is the sum of the negative active power WPS values at each data
update interval.
q1 + q2
q+1 + q+2
q–1 + q–2
S (n) is the nth apparent power
The unit of time is hours.
Q (n) is the nth reactive power
The unit of time is hours.
Note
• u(n) denotes the instantaneous voltage. i(n) denotes the instantaneous current.
th
• n denotes the n measurement period. The measurement period is determined by the
synchronization source setting.
• AVG[ ] denotes the simple average of the item in brackets determined over the data
measurement interval. The data measurement interval is determined by the synchronization
source setting.
• PΣ denotes the active power of wiring unit Σ. Input elements are assigned to wiring unit Σ
differently depending on the number of input elements that are installed in the WT500 and
the selected wiring system pattern. For details, see section 2.3.
• The numbers 1, 2, and 3 used in the equations for UrmsΣ, UmnΣ, UrmnΣ, UdcΣ, UacΣ,
IrmsΣ, ImnΣ, IrmnΣ, IdcΣ, IacΣ, PΣ, SΣ, QΣ, WPΣ, and qΣ indicate the case when input
elements 1, 2, and 3 are set to the wiring system shown in the table.
• Equation Type 3 for SΣ and QΣ can only be selected on models with the harmonic
measurement option.
• On the WT500, S, Q, λ, and f are derived through the computation of the measured values
of voltage, current, and active power (however, when Type 3 is selected, Q is calculated
directly from the sampled data). Therefore, for distorted signal input, the value obtained on
the WT500 may differ from that obtained on other instruments that use a different method.
• For Q [var], when the current leads the voltage, the Q value is displayed as a negative
value; when the current lags the voltage, the Q value is displayed as a positive value. The
value of QΣ may be negative, because it is calculated from the Q of each element with the
signs included.
Three-phase, three-wire with
three-voltage, three-current
method. 3P3W(3V3A)
N
1
S (n) Time
•
N
n = 1
function. N is the number of data updates.
N
1
Q (n) Time
•
N
n = 1
function. N is the number of data updates.
P
S
( )
P
-1
COS
S
(Table 3/3)
Three-phase,
four-wire
3P4W
WP1 + WP2 + WP3
WP+1 + WP+2 + WP+3
WP–1 + WP–2 + WP–3
q + q + q
1 2 3
q + q + q
+1 +2 +3
q + q + q
–1 –2 –3
App
Index
App-3
1
2
3
4
5
6
7
8
9
10
11
12
13
14