GE Multilin N60 Network Stability and Synchrophasor Measurement System 5-219
5 SETTINGS 5.7 CONTROL ELEMENTS
5
8 BIT COMP 1 ARG B0: “DIGITIZER 1 BIT 0" 8 BIT COMP 1 ARG B4: “DIGITIZER 1 BIT 4”
8 BIT COMP 1 ARG B1: “DIGITIZER 1 BIT 1" 8 BIT COMP 1 ARG B5: “DIGITIZER 1 BIT 5”
8 BIT COMP 1 ARG B2: “DIGITIZER 1 BIT 2" 8 BIT COMP 1 ARG B6: “DIGITIZER 1 BIT 6”
8 BIT COMP 1 ARG B3: “DIGITIZER 1 BIT 3" 8 BIT COMP 1 ARG B7: “DIGITIZER 1 BIT 7”
3. The two power values are to be added, therefore set
8BIT COMP 1 ADD/SUB to “On”.
4. The alarm should be established when the total power in either direction (import or export) is above the threshold,
therefore set
8BIT COMP 1 INPUT MODE to “Absolute”.
5. The alarm should also be established when the total power is above the threshold, therefore set the
8BIT COMP 1 DIREC-
TION to “Over”.
6. The digitized power values should be scaled to meaningful values. Assuming that MW are to be used for comparison
and display, set 8BIT COMP 1 SCALE FACTOR to “11.81”. In this way, the 8BIT COMP 1 A, 8BIT COMP 1 B, and 8BIT COMP 1
Out actual values represent the remote (UR-1), local (UR-2), and total power values in MW.
7. The alarm should also be established when the total power is greater than 2500 MW. As such, set 8BIT COMP 1 PICKUP
to “2500.00”.
8. The alarm should be cleared when the total power is less than 2000 MW. As such, the hysteresis setting should be
2500 – 2000 = 500 MW. Set 8BIT COMP 1 HYSTERESIS to “500”.
9. Using the timing requirements, set 8BIT COMP 1 PICKUP DELAY to “0.050” and 8BIT COMP 1 RESET DELAY to “1.000”. The
8BIT COMP 1 OP FlexLogic operand should be used to set the alarm.
10. For monitoring and telemetry purposes, the digitized power values should be scaled to meaningful values. Assuming
MW to be displayed, set 8BIT COMP 1 SCALE FACTOR to “11.81”. In this way, the actual values 8BIT COMP 1 A, 8BIT COMP
1 B and 8BIT COMP 1 Out will represent the remote (UR-1), local (UR-2), and total power values in MW.
For the User-definable displays at UR-2 (optional):
To display the remote and total power values the following screen may be set up:
DISP 1 TOP LINE: “REMOTE MW: ~”
DISP 1 BOTTOM LINE: “TOTAL MW: ~”
DISP 1 ITEM 1: “8100” (Modbus register address of 8BIT COMP 1 A)
DISP 1 ITEM 2: “8104” (Modbus register address of 8BIT COMP 1 Out)
Analysis of metering errors at UR-2:
The remote and local power values are measured with the maximum error of ±1% of reading (at power factors above 0.8).
The digitization (round up) error is 0.2% of full scale, or 0.002 2 1500 MW = 6 MW. Consequently,
• Remote power is measured at UR-2 with a worst-case error of ± (1% of reading + 6 MW).
• Total power is measured at UR-2 with a worst-case error of ± (1% of UR-1 reading + 1% of UR-2 reading + 12 MW).
For example, with a reading of 1020 MW at UR-1 and 800 MW at UR-2, the remote power is measured at UR-2 with the
worst-case error of ±(0.01 1020 MW + 6 MW) = ±16.2 MW, or ±1.6%. The reading for remote power at UR-2 is the prod-
uct of the digitized value sent from UR-1 and received at UR-2 and the scale factor setting; that is,
(EQ 5.23)
Therefore, the reading for the remote power at UR-2 is 1015.7 MW, versus 1020 MW at the point of origin (UR-1).
The total power is measured at UR-2 with the worst-case error of ± (0.01 1020 MW + 0.01 800 MW + 12 MW) =
±30.2MW, or ±1.7%. The reading for the total power at UR-2 is the sum of the digitized value sent from UR-1 and received
at UR-2 and the digitized value at UR-2 multiplied by the scaling factor; that is,
(EQ 5.24)
Therefore, the reading for the total power at UR-2 is 1818.7 MW, versus a true total of 1020 MW + 800 MW = 1820 MW.
Total Power at UR-1 round
1020 MW
1500 MW
--------------------------
127
11.81 MW=
86 11.81 MW= 1015.7 MW=
Total Power at UR-2 round
1020 MW
1500 MW
--------------------------
127
round
800 MW
1500 MW
--------------------------
127
+
11.81 MW=
86 68+11.81 MW= 1818.7 MW=
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