GE c60 Instruction Manual

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5-278 C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUALTRANSDUCER INPUTS/OUTPUTS CHAPTER 5: SETTINGS5DCMA OUTPUT H1 MAX VAL — This setting allows setting the maximum limit for the signal that drives the output. This settingis used to control the mapping between an internal analog value and the output current. The setting is entered in per-unitvalues. The base units are defined in the same manner as the FlexElement base units.Three application examples follow.Example: Power monitoringA 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. 5-27The three-phase power with 20% overload margin is:Eq. 5-28The base unit for power (refer to the FlexElements section in this chapter for additional details) is:Eq. 5-29The minimum and maximum power values to be monitored (in pu) are:Eq. 5-30The following settings are 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: Current monitoringThe 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, allowingfor 50% overload.The phase current with the 50% overload margin is:Eq. 5-31The base unit for current (see the FlexElements section in this chapter for additional details) is:Eq. 5-32The minimum and maximum power values to be monitored (in pu) are:Eq. 5-33NOTEThe 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).P 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= == =