GE L90, Инструкция по эксплуатации

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CHAPTER 5: SETTINGS TRANSDUCER INPUTS/OUTPUTS
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL 5-427
5
The base unit for power (refer to the FlexElements section in this chapter for additional details) is:
Eq. 5-53
The minimum and maximum power values to be monitored (in pu) are:
Eq. 5-54
The following settings are entered:
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 ±0.005 x (1-(-1)) x 20.65 MW = ±0.207 MW
• ±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 is to be monitored from 0 A upwards, allowing
for 50% overload.
The phase current with the 50% overload margin is:
Eq. 5-55
The base unit for current (see the FlexElements section in this chapter for additional details) is:
Eq. 5-56
The minimum and maximum power values to be monitored (in pu) are:
Eq. 5-57
The following settings are 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 can be calculated by superimposing the following two sources of error:
•
±0.5% of the full scale for the analog output module, or ±0.005 x (20 - 4) x 6.3 kA = ±0.504 kA
• ±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 is to be monitored in the range from 70% to 110% of nominal.