GE UR T60, Instruction Manual

Page: 430 / 724

5-292 T60 Transformer Protection System GE Multilin
5.9 TRANSDUCER INPUTS AND OUTPUTS 5 SETTINGS
5
(EQ 5.64)
The minimum and maximum voltage values to be monitored (in pu) are:
(EQ 5.65)
The following settings should be entered:
DCMA OUTPUT H3 SOURCE
: “SRC 2 V_1 mag”
DCMA OUTPUT H3 RANGE
: “0 to 1 mA”
DCMA OUTPUT H3 MIN VAL
: “0.404 pu”
DCMA OUTPUT H3 MAX VAL
: “0.635 pu”
The limit settings differ from the expected 0.7 pu and 1.1 pu because the relay calculates the positive-sequence quantities
scaled to the phase-to-ground voltages, even if the VTs are connected in “Delta” (refer to the
Metering conventions section
in chapter 6), while at the same time the VT nominal voltage is 1 pu for the settings. Consequently the settings required in
this example differ from naturally expected by the factor of
.
The worst-case error for this application could be calculated by superimposing the following two sources of error:
• ±0.5% of the full scale for the analog output module, or
• ±0.5% of reading
For example, under nominal conditions, the positive-sequence reads 230.94 kV and the worst-case error is
0.005 x 230.94 kV + 1.27 kV = 2.42 kV.
V
BASE
0.0664 kV 6024 × 400 kV
= =
minimum voltage
161.66 kV
400 kV
---------------------------
0.404 pu, maximum voltage
254.03 kV
400 kV
---------------------------
0.635 pu
= = = =
3
0.005 1 0
–
( ) ×
254.03 kV
× ±
1.27 kV
±
=