5-196 G60 Generator Management Relay GE Multilin5.8 TRANSDUCER INPUTS/OUTPUTS 5 SETTINGS5EXAMPLE 1:A three phase active power on a 13.8 kV system measured via UR-series relay source 1 is to be monitored by the dcmA H1output of the range of –1 to 1 mA. The following settings are applied on the relay: CT ratio = 1200:5, VT secondary 115, VTconnection is delta, and VT ratio = 120. The nominal current is 800 A primary and the nominal power factor is 0.90. Thepower is to be monitored in both importing and exporting directions and allow for 20% overload compared to the nominal.The nominal three-phase power is:(EQ 5.46)The three-phase power with 20% overload margin is:(EQ 5.47)The base unit for power (refer to the FlexElements section in this chapter for additional details) is:(EQ 5.48)The minimum and maximum power values to be monitored (in pu) are:(EQ 5.49)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 forthis 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 0.9For example at the reading of 20 MW, the worst-case error is 0.01 × 20 MW + 0.207 MW = 0.407 MW.EXAMPLE 2: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 5.50)The base unit for current (refer to the FlexElements section in this chapter for additional details) is:(EQ 5.51)The minimum and maximum power values to be monitored (in pu) are:(EQ 5.52)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 nominalP 3 13.8 kV 0.8 kA× 0.9×× 17.21 MW= =P max 1.2 17.21 MW× 20.65 MW= =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 MW16.56 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 kA5 kA------------ 0 pu, maximum current 6.3 kA5 kA----------------- 1.26 pu= == =0.005 20 4–( ) 6.3 kA××± 0.504 kA±=
