Rated Phase-To-Phase Voltage; Rated Apparent Power; Phase Shift Between Windings - Siemens 7UT51 Instruction Manual

7UT51 v3
4.2.4 Rated Phase
Voltage
The rated phase-to-phase voltage ( V
winding of the protected transformer is specified in
addresses 1102, 1122, and 1142.
1102 Vn WIND 1
1122 Vn WIND 2
1142 Vn WIND 3 (7UT513 only)
- -
Rated phase to phase voltage (Vn) of each winding of
the protected transformer.
-
Range: 0.4 800.0 kV
Default: 110.0 kV for Winding 1, 11.0 kV for windings
2 and 3
×
Vmax Vmin
×
----------------------------------
2
Vn =
Vmax
+
where V is the highest winding-voltage rating and
max
V is the lowest winding-voltage rating. This is not a
min
critical calculation, but rather a better fit than using the
mid-tap nominal value.
4.2.5

Rated Apparent Power

The rated apparent power of each winding of the
protected transformer must be specified in addresses
1103, 1123, and 1143.
1103 VA WIND 1
1123 VA WIND 2
1143 VA WIND 3 (7UT513 only)
Rated apparent power of each winding of the protected
transformer.
–
Range: 0.2 5000.0 MVA
Default: 38.1 MVA for windings 1 and 2, 10.0 MVA for
winding 3
For three-winding transformers with different MVA
ratings of the windings, the relay automatically
references all currents to the power base of the largest
winding.
PRIM-2330C
to Phase
- -
) of each
n
2
---------------------------------- -
=
Vmin
1 1
------------ - --------------
+
Vmin Vmax
Transformer Differential Protection (87T and 87HS)
Note that for FOA transformers, choosing the lowest
rating will provide the most sensitive protection;
however, there is a possibility the relay will be
continuously "picked up" if the load approaches the
maximum FOA rating.
4.2.6 Phase Shift Between
Windings
The phase shift from the first winding to the second
winding (and, if the transformer has three windings,
from the first winding to the third winding) must be
specified in addresses 1121 and 1141. The phase shift
is described by a vector group number, which is an
integer n in the range 0 to 11 such that the phase shift
is a lag angle of
and Table 4.2 on page 47).
(4.6)
1121 VECTOR GR2
1141 VECTOR GR3 (7UT513 only)
Phase shift from Winding 1 to winding 2 (Address 1121)
and from Winding 1 to winding 3 (Address 1141) of the
protected transformer. An integer vector group number n
specifies the phase shift as a lag angle of n ×30°.
–
Range: 0 11 (unitless)
Default: 0
Table 4.1 on page 46 (for a delta reference winding) and
Table 4.2 on page 47 (for a wye reference winding) show
for each vector group the corresponding phase shift in
degrees, a diagram of the transformer wiring that would
result in that phase shift, the phase diagram.
Example: A two-winding delta-wye transformer
connected according to ANSI standards
has the low-side (secondary) winding
lagging the high-side by 30°. So
Address 1121 should usually be set to 1
(not the default value of 0).
Note: The relay assumes a phase-angle rotation
order of A-B-C. If the order is instead C-B-A,
connect the CTs so the relay sees an A-B-C
rotation order and use the vector group
corresponding to 360° minus the lag-angle of
the C-B-A order. (For example, a C-B-A order
lag-angle of 30° corresponds to an A-B-C order
advance-angle of 30°. But since the vector
group setting must describe a lag-angle,
specify vector group 11, corresponding to 330°
(360° – 30°).
×
(see Table 4.1 on page 46
n 30°
4
45