GE b30, Instruction Manual

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5-274 B30 BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
TRANSDUCER INPUTS/OUTPUTS CHAPTER 5: SETTINGS
5
DCMA OUTPUT H1 MIN VAL
— This setting allows setting the minimum limit for the signal that drives the output. This setting
is used to control the mapping between an internal analog value and the output current. The setting is entered in per-unit
values. The base units are defined in the same manner as the FlexElement base units.
DCMA OUTPUT H1 MAX VAL
— This setting allows setting the maximum limit for the signal that drives the output. This setting
is used to control the mapping between an internal analog value and the output current. The setting is entered in per-unit
values. The base units are defined in the same manner as the FlexElement base units.
Three application examples follow.
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. 5-23
The base unit for current (see the FlexElements section in this chapter for additional details) is:
Eq. 5-24
The minimum and maximum power values to be monitored (in pu) are:
Eq. 5-25
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.
The minimum and maximum positive-sequence voltages to be monitored are:
Eq. 5-26
The base unit for voltage (see the FlexElements section in this chapter for additional details) is:
Eq. 5-27
The
DCMA OUTPUT H1 MIN VAL
and
DCMA OUTPUT H1 MAX VAL
settings are ignored for power factor base units (i.e. if
the
DCMA OUTPUT H1 SOURCE
is set to FlexAnalog value based on power factor measurement).