GE G60 Instruction Manual page 479

5 SETTINGS
The base unit for power (refer to the FlexElements section in this chapter for additional details) is:
The minimum and maximum power values to be monitored (in pu) are:
minimum power
=
The following settings should be entered:
DCMA OUTPUT H1 SOURCE
: "–1 to 1 mA"
DCMA OUTPUT H1 RANGE
DCMA OUTPUT H1 MIN VAL
DCMA OUTPUT H1 MAX VAL
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:
The base unit for current (refer to the FlexElements section in this chapter for additional details) is:
The minimum and maximum power values to be monitored (in pu) are:
minimum current
The following settings should be entered:
DCMA OUTPUT H2 SOURCE
: "4 to 20 mA"
DCMA OUTPUT H2 RANGE
DCMA OUTPUT H2 MIN VAL
DCMA OUTPUT H2 MAX VAL
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:
V 0.7
=
min
The base unit for voltage (refer to the FlexElements section in this chapter for additional details) is:
GE Multilin
× ×
P 115 V 120
=
BASE
20.65 MW
–
------------------------------
1.247 pu,
= –
16.56 MW
: "SRC 1 P"
: "–1.247 pu"
: "1.247 pu"
×
I 1.5 4.2 kA
=
max
I
=
BASE
0 kA
----------- -
0 pu, maximum current
= =
5 kA
: "SRC 1 Ia RMS"
: "0.000 pu"
: "1.260 pu"
400 kV
× ------------------ -
161.66 kV,
=
3
G60 Generator Protection System
5.9 TRANSDUCER INPUTS AND OUTPUTS
1.2 kA 16.56 MW
=
20.65 MW
-------------------------- -
maximum power
=
16.56 MW
± × ( – ( ) ) ×
0.005 1 1 20.65 MW
–
6.3 kA
=
5 kA
6.3 kA
---------------- -
1.26 pu
= =
5 kA
± × ( ) 6.3 kA ×
0.005 20 4
– =
400 kV
× ------------------ -
V 1.1 254.03 kV
= =
max
3
(EQ 5.57)
1.247 pu
(EQ 5.58)
=
±
0.207 MW
=
(EQ 5.59)
(EQ 5.60)
(EQ 5.61)
±
0.504 kA
(EQ 5.62)
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5