GE T60, Instruction Manual

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GE Multilin T60 Transformer Protection System 5-337
5 SETTINGS 5.9 TRANSDUCER INPUTS AND OUTPUTS
5
The base unit for power (refer to the FlexElements section in this chapter for additional details) is:
(EQ 5.59)
The minimum and maximum power values to be monitored (in pu) are:
(EQ 5.60)
The following settings should be 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
• ±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 5.61)
The base unit for current (refer to the FlexElements section in this chapter for additional details) is:
(EQ 5.62)
The minimum and maximum power values to be monitored (in pu) are:
(EQ 5.63)
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 5.64)
The base unit for voltage (refer to the FlexElements section in this chapter for additional details) is:
P
BASE
115 V 120 × 1.2 kA × 16.56 MW
= =
minimum power
20.65 MW
–
16.56 MW
------------------------------
1.247 pu, maximum power
20.65 MW
16.56 MW
---------------------------
1.247 pu
= = – = =
0.005 ± 1 1
–
( )
–
( ) 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
= = = =