GE T35 UR Series

GE Multilin T35 Transformer Protection System 5-187
5 SETTINGS 5.9 TRANSDUCER INPUTS AND OUTPUTS
5
DCMA OUTPUT H1 SOURCE: “SRC 1 P”
DCMA OUTPUT H1 RANGE: “–1 to 1 mA”
DCMA OUTPUT H1 MIN VAL: “–1.247 pu”
DCMA OUTPUT H1 MAX VAL: “1.247 pu”
With the above settings, the output will represent the power with the scale of 1 mA per 20.65 MW. The worst-case error for
this application can be calculated by superimposing the following two sources of error:
• ±0.5% of the full scale for the analog output module, or
• ±1% of reading error for the active power at power factor of 0.9
For example at the reading of 20 MW, the worst-case error is 0.01 × 20 MW + 0.207 MW = 0.407 MW.
EXAMPLE: CURRENT MONITORING
The phase A current (true RMS value) is to be monitored via the H2 current output working with the range from 4 to 20 mA.
The CT ratio is 5000:5 and the maximum load current is 4200 A. The current should be monitored from 0 A upwards, allow-
ing for 50% overload.
The phase current with the 50% overload margin is:
(EQ 5.47)
The base unit for current (refer to the FlexElements section in this chapter for additional details) is:
(EQ 5.48)
The minimum and maximum power values to be monitored (in pu) are:
(EQ 5.49)
The following settings should be entered:
DCMA OUTPUT H2 SOURCE: “SRC 1 Ia RMS”
DCMA OUTPUT H2 RANGE: “4 to 20 mA”
DCMA OUTPUT H2 MIN VAL: “0.000 pu”
DCMA OUTPUT H2 MAX VAL: “1.260 pu”
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
• ±0.25% of reading or ±0.1% of rated (whichever is greater) for currents between 0.1 and 2.0 of nominal
For example, at the reading of 4.2 kA, the worst-case error is max(0.0025 × 4.2 kA, 0.001 × 5 kA) + 0.504 kA = 0.515 kA.
EXAMPLE: VOLTAGE MONITORING
A positive-sequence voltage on a 400 kV system measured via source 2 is to be monitored by the DCmA H3 output with a
range of 0 to 1 mA. The VT secondary setting is 66.4 V, the VT ratio setting is 6024, and the VT connection setting is
“Delta”. The voltage should be monitored in the range from 70% to 110% of nominal.
The minimum and maximum positive-sequence voltages to be monitored are:
(EQ 5.50)
The base unit for voltage (refer to the FlexElements section in this chapter for additional details) is:
(EQ 5.51)
The minimum and maximum voltage values to be monitored (in pu) are:
(EQ 5.52)
The following settings should be entered:
0.005± 11–()–()20.65 MW×× 0.207 MW±=
I
max
1.5 4.2 kA× 6.3 kA==
I
BASE
5 kA=
minimum current
0 kA
5 kA
------------
0 pu, maximum current
6.3 kA
5 kA
-----------------
1.26 pu====
0.005 20 4–()6.3 kA××± 0.504 kA±=
V
min
0.7
400 kV
3
------------------ -
× 161.66 kV, V
max
1.1
400 kV
3
------------------ -
× 254.03 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====