Voltage Base Rules

With several new users since the global training in August, it is useful to review the OpenDSS voltage base rules since they are different than many other programs:

• Voltage bases are not used for the solution of the network; the per-unit system is not used internally. The solution is performed in actual volts, amps, and ohms (or siemens) .
• There must be sufficient data provided for each circuit element of the system model to formulate the model of the element in actual impedance values. So the kV value is used as a base to convert input values in pu, percent, or power to ohms.
• Since most power engineers refer to ratings of 3-phase system elements as L-L kV, OpenDSS uses L-L kV for the ratings of 3-phase elements.
• We extended that rule to include elements that are declared as 2-phase, since in the US, most 2-phase systems are 2 phases of a 3-phase system with the voltages related by sqrt(3) and displaced 120 degrees from each other. (You can do that if you have a neutral conductor).
• The kV rating of 1-phase devices is the value that appears across the two wires of each terminal at 100% rated voltage. This would apply to all Power Conversion (PC) elements and Transformer elements. Note that 1-phase LINE elements have only one conductor per terminal; LINE elements are defined in ohms and do not have a voltage base. They can be connected anywhere in the circuit without concern for matching voltage bases. (In this regard, OpenDSS is formulated more like an EMT program than the usual power flow.)
• OpenDSS can model high phase order systems (e.g., 6-phase). The kV value is generally L-L rating for these systems. However, I would recommend running a small test with a few elements that you can verify the solution by inspection to see if OpenDSS interepreted the model correctly. (We have tested both 6-phase and 12-phase models.)

[Hugo Rodrigues Torquato]

Thank you so much!!!! This was super helpful :)