Limb Voltage Conversion - Hitachi Relion 650 Series Technical Manual

1MRK 511 557-UEN Rev. A
UT3P
IEC21000983 V1 EN-US
Figure 146: Overall block diagram of TRAFOSWT functionality
TRAFOSWT continuously reads the three-phase transformer load voltage samples from its UT3P
input (usually received from SMAI, possibly through 3PHSELECT) and multiplies them by a
conversion matrix (the matrix elements are usually obtained from SST) to obtain the respective limb
voltages (elaborated in
for visualization (DREC) and combined into a group signal for accurate detection of making instants
(ACBMSCBR). Upon activation of the CB opening indication, the function integrates the limb voltages
to obtain the magnetic fluxes in the respective transformer core; the integrated voltage samples are
also made available on analog outputs. The final integration values, taken after a specified
integration time, are considered the residual fluxes. This integration method is elaborated in
12.20.7.2. The function further evaluates target making or closing angles using the estimated
residual fluxes as explained in
The next subsections describe the functionality of TRAFOSWT in detail.
12.20.7.1

Limb Voltage Conversion

The load voltages received at the UT3P input are grouped into vectors UT of three-phase concurrent
samples. Each vector is multiplied by a conversion matrix LimbVConv to obtain the respective limb
voltages,
LIMBU = UT·LimbVConv
The coefficients of LimbVConv are taken from the LimbVConvXY settings; these values are derived
considering the following parameters:
Technical Manual
TRAFOSWT
 
Matrix Limb
elements voltages
CBSTSCFLx
OPNDETECT
VOLTGON
RESETFLUX
FALLBACK
BLOCKINT
Section 12.20.7.1). The three calculated limb voltages are directly published
Section
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Limb & Differential
Voltage Calculator
Limb voltage
angles
Residual Flux
Calculator
Closing Angle
Calculator
12.20.7.3.
LIMBUx
 
Trafo
CLANGLx
Type
VALIDSTGY
FLUXSNAP
INTEND
INVFLUX
FLUXRESET
GUID-FBA30874-C04E-47DF-989A-062D080E2998 v1
Section 12
Monitoring
Section
323