10-9
IM 253710-01E
Numerical Computations
10
Explanation
In the normal measurement mode, the sum or difference of the instantaneous values
(sampled data) of the voltage or current between elements 1, 2, and 3 can be used to
determine the measurement functions,
∆
U (
∆
Urms,
∆
Umn,
∆
Udc
∆
Uac),
∆
I (
∆
Irms,
∆
Imn,
∆
Idc,
∆
Iac). This is called delta computation. For the equation, see Appendix 3. The
measurement and computation periods are the same as those described in section 1.2,
“Measurement Modes and Measurement/Computation Periods.” Select the type of delta
computation from the following list of choices.
• OFF
No delta computation is performed.
• u1-u2
Computes the difference between the voltage of element 1 and the voltage of element
2. For example,
∆
U1 (
∆
Urms1,
∆
Umn1,
∆
Udc1,
∆
Uac1) can be determined for the
circuit shown in the diagram below.
U
±
U
±
U1
U2
∆
U1
• i1-i2
Computes the difference between the current of element 1 and the current of element
2. For example,
∆
I1 (
∆
Irms1,
∆
Imn1,
∆
Idc1,
∆
Iac1) can be determined for the circuit
shown in the diagram below.
I
±
I2
∆
I1
I
±
I1
• 3P3W>3V3A
Computes various data when the wiring method is changed from a three-phase, three-
wire system (3P3W) to a three-voltage, three current system (3V3A).
∆
U1(
∆
Urms1,
∆
Umn1,
∆
Udc1,
∆
Uac1)
∆
U3(
∆
Urms3,
∆
Umn3,
∆
Udc3,
∆
Uac3)
∆
I1(
∆
Irms1,
∆
Imn1,
∆
Idc1,
∆
Iac1)
∆
I3(
∆
Irms3,
∆
Imn3,
∆
Idc3,
∆
Iac3)
±
I
U
W
V
±
U
±
U
±
I
N
I3
I4
U4
U3
∆
U3
∆
I3
±
I
R
S
T
±
U
±
U
±
I
N
I1
I2
U2
U1
∆
U1
∆
I1
Primary
Secondary
Transformer
10.2 Selecting the Delta Computation