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6.3
Determination of Delta Computation
Delta Computation Type, Sampled Data, and Measurement Function of Delta
Computation
Sampled Data Substituted into the
Delta
Voltage U and Current I Equations
Computation
Type
difference
3P3W
3V3A
u1 –
u2 –
Delta
Star
–
Star
Delta
* Voltage U and current I equations in appendix 1, "Symbols and Determination of Measurement
Functions" in the User's Manual IM WT3001E-01EN.
IM WT3001E-51EN
The sampled data in the table are substituted in the equations of the voltage U and current I,
and the computed result is determined. The synchronization source for the delta computation
is the synchronization source (Sync Src) that is assigned to the first input element (smallest
number) of the wiring unit on which delta computation is to be performed.
u(n)
i(n)
u1 – u2
i1 – i2
u1 – u2
– i1 – i2
(u1+u2)
—
3
(u1+u2)
—
3
(u1+u2)
—
3
—
i1 + i2 + i3
—
u1 – u2
—
u2 – u3
—
u3 – u1
—
i1 + i2 + i3
Note
• The wiring unit on which to perform delta computation can be selected from ΣA and ΣB. The
input element that is assigned to the selected element is the element on which delta computation
is performed. The numbers 1, 2, and 3 that are attached to sampled data u and i in the above
table indicate that elements 1, 2, and 3 are target elements on which delta computation is
performed. If the target elements of delta computation are 2, 3, and 4, replace the numbers 1, 2,
and 3 that are attached to sampled data u and i with 2, 3, and 4, respectively.
•
u1, u2, u3 denote the sampled data of voltage of elements 1, 2, and 3, respectively. i1, i2,
and i3 denote the sampled data of current of elements 1, 2, and 3, respectively.
•
The number (1, 2, 3, and 4) that is attached to the measurement function symbol of the delta
computation has no relation to the element number.
•
It is recommended that the measurement range and scaling (transformation ratio and
coefficients) of the elements on which delta computation is performed be set the same as much
as possible. Using a different measurement range or scaling causes the measurement resolution
of the sampled data to be different. In effect, the computation result will have errors.
Data Determined with the Delta
*
Computation and Their
Measurement Function Symbols
ΔF1[UdiffA]
Differential voltage
Differential current
ΔF2[IdiffA]
Line voltage between
ΔF1[UrsA]
phase R and S
ΔF2[ItA]
Line current of phase T
ΔF1[UrA]
Phase voltage of
ΔF2[UsA]
each phase
ΔF3[UtA]
Line current of
ΔFΣ[InA]
the neutral line
ΔF1[UrsA]
Line voltage of
ΔF2[UstA]
each phase
ΔF3[UtrA]
Line current of
ΔFΣ[InA]
the neutral line
1
2
*
3
4
Note
—
5
Assumptions
i1 + i2 + i3 = 0
Assumptions
6
The centroid of the
delta connection is
computed as the
neutral point of the
7
star connection.
8
—
9
10
11
12
13
Index
6-5
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