11.11.5.7 Single transformer
SEMOD175185-669 v2
Load drop compensation
SEMOD175185-672 v5
1. Confirm that OperationLDC is set to Enabled.
2. Confirm settings for Rline and Xline.
3. Calculate the expected load voltage V
L
(displayed as a measured value on the local HMI) based on
secondary injection of transformer secondary voltage (VB = VSet) and rated load current (I
L
=
I1Base), in accordance with equation
122.
V
L
= VB - (Rline + jXline) . I
L
EQUATION2081-ANSI V2 EN-US (Equation 122)
where:
V
L
, I
L
= Re(I
L
) + jlm(I
L
) are complex phase quantities
When all secondary phase-to-ground voltages are available, use the positive-sequence
components of voltage and current. By separation of real and imaginary parts:
, , , ,vl re vb re rline il re xline il im= - × + ×
EQUATION2083-ANSI V1 EN-US (Equation 123)
, , , ,vl im vb im xline il re rline il im= - × - ×
EQUATION2085-ANSI V1 EN-US (Equation 124)
where:
vb is the complex value of the busbar voltage
il is the complex value of the line current (secondary side)
rline is the value of the line resistance
xline is the value of the line reactance
For comparison with the set-point value, the modulus of U
L
are according to equation 125.
¦ V
L
¦ = (vl , re)
2
+ (vl , im)
2
EQUATION2087-ANSI V2 EN-US (Equation 125)
4. Inject voltage for V
B
equal to setting VSet.
5. Inject current equal to rated current I2Base.
6. Confirm on the local HMI that service values for bus voltage and load current are equal to injected
quantities.
7. Confirm that the calculated value for load voltage, displayed on the local HMI, is equal to that
derived through hand calculations.
Section 11 1MRK 504 165-UUS Rev. J
Testing functionality by secondary injection
258 Transformer protection RET670
Commissioning manual
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