CIM Issues #4917
Documenation of LoadResponseCharacteristic exponents Sugg
Description
Documenation of LoadResponseCharacteristic exponents
Suggest improvement to documenation of LoadResponseCharacteristic.pVoltageExpoent on its intended usage and mathematical equation.
Voltage exponents are only used if the LoadResponseCharacteristic.exponentModel is "true". If so, then the voltage exponents are specified and used to compute load as cim:SvFlow.p = Pnominal * (cim:SvVoltage.v/cim:BaseVoltage.nominalVoltage)**cim:LoadResponseCharacteristic.voltageExponent
where:- is "raised to power of"
cim:SvFlow object is the flow at the terminal of the EnergyConsumer (See CIM definition)
cim:LoadResponseCharacterisitic is from EnergyConsumer.LoadResponseCharacteristic
cim:SvVoltage is from the connected TopologicicalNode
- is "multiply"
/ is divide
I think that Pnominal should correspond to an EnergyConsumer attribute, but I don't know which one, possible pFixed? Note UCTE profile does not exchange the nominal value, just the solved value.
Simlar description needed for qVoltageExponent, pFrequencyExponent, and qFrequencyExponent
SvFlow.p = pNominal * (frequency/(nominal frequency))**pFrequencyExponent
Note that both voltage and frequency exponents could be used together so the full equation would be:
SvFlow.p = Pnominal * (voltage/(base voltage))**pVoltageExponent * (frequency/(base frequency))**pFrequencyExponent
I think all these calculations flow from the basic definitions, but documenting how they work together make is much clearer. We could even do this in a diagram instead of as documentation on the attributes themselves.
Proposed Solution
WG 13 to discuss if we are changing the description to include the part below. All the rest seems covered.
The following text should be added to the class comments of the LoadResponseCharacteristic class. The following text should be append at the end of existing comments:
SvFlow.p = pNominal * (frequency/(nominal frequency))**pFrequencyExponent
Note that both voltage and frequency exponents could be used together so the full equation would be:
SvFlow.p = pNominal * (voltage/(base voltage))**pVoltageExponent * (frequency/(base frequency))**pFrequencyExponent
This equation covers calculation of SvFlow.p
Note, the voltage and frequency expressed in the equation are values obtained from solved power flow. Base voltage and base frequency are those derived from the connectivity of the static network model.
Decision
Reviewed on 17-Feb-2023 in Richland in-person. The text of the proposed solution was updated slightly and the decision was made to add in CIM18v04
Release Notes
The description of LoadResponseCharacteristic was updated with
pInjection = Pnominal* (Frequency/(Nominal frequency))**cim:LoadResponseCharacteristic.pFrequencyExponent
qInjection = Qnominal* (Frequency/(Nominal frequency))**cim:LoadResponseCharacteristic.qFrequencyExponent
Note that both voltage and frequency exponents could be used together so the full equation would be:
pInjection = Pnominal* (Voltage/(cim:BaseVoltage.nominalVoltage))**cim:LoadResponseCharacteristic.pVoltageExponent * (Frequency/(base frequency))**cim:LoadResponseCharacteristic.pFrequencyExponent
qInjection = Qnominal* (Voltage/(cim:BaseVoltage.nominalVoltage))**cim:LoadResponseCharacteristic.qVoltageExponent * (Frequency/(base frequency))**cim:LoadResponseCharacteristic.qFrequencyExponent
The voltage and frequency expressed in the equation are values obtained from solved power flow. Base voltage and base frequency are those derived from the connectivity of the static network model.