PowerFactory includes built-in devices to measure current (StaImea), voltage (StaVmea) and power (StaPqmea). Since PowerFactory version 2022, these devices calculate the instantaneous values, true RMS amplitudes or RMS phasor magnitudes in sequence (symmetrical) components for an automatically detectable fundamental frequency in an EMT simulation (adjusted to the actual fundamental frequency during the simulation). It is recommended to use these measurement devices in order to obtain RMS or sequence components from an EMT simulation. Refer to the Technical Reference documentation of each measurement device for more detailed information.

The following information is provided for users of PowerFactory 2021 and earlier, or for those that wish to use an open DSL model for the transformed phasor quantities.

The attached two projects (one in English and one in German) contain an EMT to RMS current and voltage signals’ converter implemented in a DSL model. This model converts instantaneous currents and voltages obtained in an EMT simulation into phasor quantities.

Both projects contain a DSL model that calculates the phasor quantities listed below from an EMT simulation.

• alpha, beta and zero components (Clarke transform):
  • instantaneous values
  • fundamental frequency phasors expressed in real and imaginary components
• Space phasor, rotating in a fixed reference frame
• d, q and zero components (Park Transform)
• Space phasor, non-rotating (i.e. in a rotating reference frame)
• Fundamental frequency phasors of the A, B, C phase quantities expressed in real and imaginary components
• Positive, negative, zero sequence component phasors in the fundamental frequency expressed in real and imaginary components
• Frequency derived from the positive sequence voltage phasor angle in the fundamental frequency (note the input parameter df_max for defining the maximum detectable rate of change of frequency -RoCoF-, which is a ramp rate limiter used as a filter for the measured frequency)

The calculations are performed by the model during the simulation and the transformed quantities are obtained directly as output signals, hence no post-processing is required.

The model has voltage and current inputs. If both are connected, the model calculates the following power quantities as well:

• Real power as instantaneous values in the phases
• Instantaneous active and reactive power of space phasors
• Fundamental frequency active and reactive power for:
  • the three phases
  • the positive, negative and zero sequence components

The model calculates the RMS phasor quantities for the frequency specified by the user (typically the nominal frequency). Therefore, the model does not calculate the full RMS signal (which results from the combination of fundamental frequency and harmonic components), but only calculates the fundamental frequency component.

The output of the calculated phasor quantities is enabled after 2 periods after the simulation has started. This is done to consider the required measurement window of at least one period and possible noise at the beginning of the simulation. The output of the calculated frequency is enabled after 4 periods after the simulation has started because the frequency is sensitive to possible noise in the measured voltage angle at the beginning of the simulation.

The model calculates the RMS phasor quantities for a fixed fundamental frequency (input parameter fn). The model does not adjust the measurement window following changes in the actual resulting fundamental frequency of the EMT simulation, but rather uses a fixed measurement window (according to fn). However, the model can calculate ("measure") the actual fundamental frequency. If the actual fundamental frequency differs from the entered fundamental frequency, the calculated RMS values may differ from the actual fundamental frequency RMS values (depending on the difference between actual and entered fundamental frequency).

The DSL model is provided for demonstration purposes and it is not recommended to use it as part of a controller.