YOKOGAWA WT1800 User Manual page 113

Measurement Functions Used in Delta Computation (Option)
Computed results are determined by substituting all of the sampled data in the table into the equations
for voltage U and current I.
as the source of the first input element (the input element with the smallest number) in the wiring unit
that is subject to delta computation.
Measurement
Function
Voltage [V]
Current [A]
Power [W]
For the 3P3W→3V3A computation, it is assumed that i1 + i2 + i3 = 0.
For the Delta→Star computation, it is assumed that the center of the delta connection is computed
as the center of the star connection.
* The equations for voltage U and current I listed in "Symbols and Determination of Measurement
Functions."
IM WT1801-03EN
Appendix 1 Symbols and Determination of Measurement Functions
*
The synchronization source used in delta computation is the same source
Data Determined with the Delta Computation and
Delta
Corresponding Symbols
Computation
The computation mode for ΔU1 to ΔU3, ΔUΣ, and
Type
ΔI can be set to rms, mean, dc, r-mean, or ac.
Difference Computed differential voltage
3P3W→3V3A Unmeasured line voltage
computed in a three-phase,
three-wire system
Delta→Star Phase voltage computed in a
three-phase, three-wire (3V3A)
system
Wiring unit voltage
(ΔU1 + ΔU2 + ΔU3)
ΔUΣ=
Star→Delta Line voltage computed in a
three-phase, four-wire system
Wiring unit voltage
(ΔU1 + ΔU2 + ΔU3)
ΔUΣ=
Difference
Computed differential current
3P3W→3V3A Unmeasured phase current
Delta→Star Neutral line current
Star→Delta Neutral line current
Difference —
3P3W→3V3A —
Delta→Star Phase power computed in a
three-phase, three-wire (3V3A)
system
Wiring unit power
ΔPΣ = ΔP1 + ΔP2+ ΔP3
Star→Delta —
ΔU1[Udiff]
ΔU1[Urs]
ΔU1[Ur]
ΔU2[Us]
ΔU3[Ut]
ΔUΣ[UΣ]
3
ΔU1[Urs]
ΔU2[Ust]
ΔU3[Utr]
ΔUΣ[UΣ]
3
ΔI[Idiff]
ΔI[It]
ΔI[In]
ΔI[In]
—
—
ΔP1[Pr]
ΔP2[Ps]
ΔP3[Pt]
ΔPΣ[PΣ]
—
1
2
Substituted
3
Sampled Data
u (t), i (t)
u1 – u2
4
u1 – u2
(u1 + u2)
5
u1 –
3
(u1 + u2)
u2 –
3
6
(u1 + u2)
–
3
—
App
u1 – u2
u2 – u3
Index
u3 – u1
—
i1 – i2
–i1 – i2
i1 + i2 + i3
i1 + i2 + i3
—
—
{ }
(u1 + u2)
i1
u1 –
•
3
{ }
(u1 + u2)
i2
u2 –
•
3
{ }
(u1 + u2)
i3
–
•
3
—
—
App-7