YOKOGAWA WT1800 User Manual page 109

Measurement Function
Wiring system
WPΣ [Wh]
qΣ [Ah]
WSΣ [VAh]
WQΣ [varh]
λΣ
ΦΣ [°]
Note
• u(n) denotes the instantaneous voltage.
• i(n) denotes the instantaneous current.
• n denotes the n
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 WT1800 and the selected wiring
system pattern.
• The numbers 1, 2, and 3 used in the equations for UrmsΣ, UmnΣ, UrmnΣ, UdcΣ, UacΣ, IrmsΣ, ImnΣ,
IrmnΣ, IdcΣ, IacΣ, PΣ, SΣ, QΣ, PcΣ, 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 WT1800, S, Q, λ, and Φ 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 WT1800 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.
IM WT1801-03EN
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-wire
1P3W
WPΣ WP1 + WP2
When the watt-hour integration method for each polarity is
WP+Σ
Charge/Discharge
WP+1 + WP+2
When the watt-hour integration method for each polarity is
Sold/Bought
WP+Σ is the sum of the positive active power WPΣ values at each data
update interval.
WP–Σ
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-Σ is the sum of the negative active power WPΣ values at each data
update interval.
qΣ q1 + q2
q+Σ
q+1 + q+2
q–Σ
q–1 + q–2
SΣ(n) is the nth apparent power Σ function. N is the number of data updates.
The unit of time is hours.
QΣ(n) is the nth reactive power Σ function. N is the number of data updates.
The unit of time is hours.
PΣ
SΣ
COS
th measurement period. The measurement period is determined by the synchronization
Three-phase, three-wire
Three-phase,
with three-voltage,
three-wire
three-current method.
3P3W
3P3W(3V3A)
N
1
SΣ(n) Time
•
N
n = 1
N
1
QΣ(n) Time
•
N
n = 1
( )
PΣ
-1
SΣ
1
(Table 3/3)
Three-phase,
2
four-wire
3P4W
WP1 + WP2 + WP3
3
WP+1 + WP+2 + WP+3
4
WP–1 + WP–2 + WP–3
5
6
q + q + q
1 2 3
q + q + q
+1 +2 +3
q + q + q
–1 –2 –3
App
Index
App-3