YOKOGAWA WT500 User Manual page 169

Explanation
IM 760201-01E
In the normal measurement of U and I, the sum or difference of the instantaneous
values (sampled data) of the voltage or current between the elements assigned to the
target wiring unit for delta computation can be used to determine the measurement
functions, ΔU and ΔI. This operation is called delta computation. For information about
the equations involved, see appendix 10. The measurement period is the same as
that described in "Measurement Period" in section 2.2, "Measurement Functions and
Periods."
Selecting the Target Wiring Unit for Delta Computation
The wiring units for delta computation can only be selected when three input elements
are installed in the WT500 and one of the following wiring system combinations is used:
• Input elements 1 and 2 are set to 1P3W or 3P3W (Σ).
• Input elements 2 and 3 are set to 1P3W or 3P3W (Σ).
• Input elements 1, 2, and 3 are set to 3P4W or 3V3A (Σ).
Selecting the Delta Computation Type
You can select the delta computation type from the choices below. The selectable items
vary depending on the selected wiring system.
Wiring System Selectable delta computation types
1P3W Difference or 3P3W>3V3A
3P3W Difference or 3P3W>3V3A
3P4W Star>Delta
3P3W(3V3A) Delta>Star
• Difference
Computes the differential voltage and differential current between two elements.
When Difference is specified for wiring unit Σ
ΔF1rms[Udiff], ΔF1mn[Udiff], ΔF1dc[Udiff], ΔF1rmn[Udiff], ΔF1ac[Udiff]
ΔF2rms[Idiff], ΔF2mn[Idiff], ΔF2dc[Idiff], ΔF2rmn[Idiff], ΔF2ac[Idiff]
* rms, mn, dc, rmn, and ac are delta computation modes (see the next page).
• 3P3W>3V3A
The data of a three-phase, three-wire system (3P3W) is converted to the data of a
three-phase, three-wire system with a three-voltage, three-current method (3V3A).
When 3P3W>3V3A is specified for wiring unit Σ
ΔF1rms[Urs], ΔF1mn[Urs], ΔF1dc[Urs], ΔF1rmn[Urs], ΔF1ac[Urs]
ΔF2rms[It], ΔF2mn[It], ΔF2dc[It], ΔF2rmn[It], ΔF2ac[It]
* rms, mn, dc, rmn, and ac are delta computation modes (see the next page).
±
R I
I1
Urs
N
S
T
I2
±
I
It
5.17 Setting Delta Computation (Optional)
U
U1
±
U
U2
±
1
2
3
4
5
6
7
8
9
10
11
12
13
14
App
Index
5-43