Load

Load objects present a method for taking power out of the system in controlled, known amounts. While implemented as a constant load, player objects can be used to vary the load with time. load objects provide a means to implement constant current, constant power, and constant impedance losses or generation into the system. The convention is a load is a positive quantity, so generation would need to be represented as a negative number.

For technical details on load modeling, see Component Modeling Theory.

Loads can be a mixture of the constant current, constant impedance, and constant power types. A typical, mixed load would be implemented as

object load {
    phases "ABCD";
    name 841;
    constant_current_C -0.586139+9.765222j;
    constant_impedance_B 221.915014+104.430595j;
    constant_power_A 42000.000000+21000.000000j;
    nominal_voltage 4800;
    }

Load Parameters

load objects are derived from node objects, so any parameters of the node object are available as well.

The I/O column indicates whether a property is user-settable input (I), simulation-computed output (O), or both (IO).

General Properties

Table 1: load table 1
Property Name	Type	Unit	I/O	Description
load_class	enumeration	N/A	I	Describes the type of load the object represents. Used for informational purposes only. Valid types may be referenced by keyword or number 0 - `U` - Unknown load type 1 - `R` - Residential load 2 - `C` - Commercial load 3 - `I` - Industrial load 4 - `A` - Agricultural load
load_priority	enumeration	N/A	I	Load classification based on priority. Valid values: `DISCRETIONARY`, `PRIORITY`, `CRITICAL`.
phase_loss_protection	bool	N/A	I	Trip all three phases of the load if a fault occurs.

ZIP Load Properties

These properties define constant power, constant current, and constant impedance loads directly. The _A, _B, _C variants automatically map to wye (A–N, B–N, C–N) or delta (A–B, B–C, C–A) depending on the object's phase configuration. The _real and _reac suffixed variants provide access to the real and imaginary components individually.

Table 2: load table 2
Property Name	Type	Unit	I/O	Description
constant_power_A	complex	VA	IO	Constant power load on phase A (wye A–N, delta A–B).
constant_power_B	complex	VA	IO	Constant power load on phase B (wye B–N, delta B–C).
constant_power_C	complex	VA	IO	Constant power load on phase C (wye C–N, delta C–A).
constant_power_A_real	double	W	IO	Constant power load on phase A, real only.
constant_power_B_real	double	W	IO	Constant power load on phase B, real only.
constant_power_C_real	double	W	IO	Constant power load on phase C, real only.
constant_power_A_reac	double	VAr	IO	Constant power load on phase A, imaginary only.
constant_power_B_reac	double	VAr	IO	Constant power load on phase B, imaginary only.
constant_power_C_reac	double	VAr	IO	Constant power load on phase C, imaginary only.
constant_current_A	complex	A	IO	Constant current load on phase A (wye A–N, delta A–B).
constant_current_B	complex	A	IO	Constant current load on phase B (wye B–N, delta B–C).
constant_current_C	complex	A	IO	Constant current load on phase C (wye C–N, delta C–A).
constant_current_A_real	double	A	IO	Constant current load on phase A, real only.
constant_current_B_real	double	A	IO	Constant current load on phase B, real only.
constant_current_C_real	double	A	IO	Constant current load on phase C, real only.
constant_current_A_reac	double	A	IO	Constant current load on phase A, imaginary only.
constant_current_B_reac	double	A	IO	Constant current load on phase B, imaginary only.
constant_current_C_reac	double	A	IO	Constant current load on phase C, imaginary only.
constant_impedance_A	complex	Ohm	IO	Constant impedance load on phase A (wye A–N, delta A–B).
constant_impedance_B	complex	Ohm	IO	Constant impedance load on phase B (wye B–N, delta B–C).
constant_impedance_C	complex	Ohm	IO	Constant impedance load on phase C (wye C–N, delta C–A).
constant_impedance_A_real	double	Ohm	IO	Constant impedance load on phase A, real only.
constant_impedance_B_real	double	Ohm	IO	Constant impedance load on phase B, real only.
constant_impedance_C_real	double	Ohm	IO	Constant impedance load on phase C, real only.
constant_impedance_A_reac	double	Ohm	IO	Constant impedance load on phase A, imaginary only.
constant_impedance_B_reac	double	Ohm	IO	Constant impedance load on phase B, imaginary only.
constant_impedance_C_reac	double	Ohm	IO	Constant impedance load on phase C, imaginary only.

Explicit Wye-Connected Load Properties

These properties specify ZIP loads on an explicit wye (phase-to-neutral) connection, regardless of the object's phase configuration. They are input only. The _real and _reac suffixed variants provide access to the real and imaginary components individually.

Table 3: load table 3
Property Name	Type	Unit	I/O	Description
constant_power_AN	complex	VA	I	Constant power load on phase A.
constant_power_BN	complex	VA	I	Constant power load on phase B.
constant_power_CN	complex	VA	I	Constant power load on phase C.
constant_power_AN_real	double	W	I	Constant power load on phase A, real only.
constant_power_BN_real	double	W	I	Constant power load on phase B, real only.
constant_power_CN_real	double	W	I	Constant power load on phase C, real only.
constant_power_AN_reac	double	VAr	I	Constant power load on phase A, imaginary only.
constant_power_BN_reac	double	VAr	I	Constant power load on phase B, imaginary only.
constant_power_CN_reac	double	VAr	I	Constant power load on phase C, imaginary only.
constant_current_AN	complex	A	I	Constant current load on phase A.
constant_current_BN	complex	A	I	Constant current load on phase B.
constant_current_CN	complex	A	I	Constant current load on phase C.
constant_current_AN_real	double	A	I	Constant current load on phase A, real only.
constant_current_BN_real	double	A	I	Constant current load on phase B, real only.
constant_current_CN_real	double	A	I	Constant current load on phase C, real only.
constant_current_AN_reac	double	A	I	Constant current load on phase A, imaginary only.
constant_current_BN_reac	double	A	I	Constant current load on phase B, imaginary only.
constant_current_CN_reac	double	A	I	Constant current load on phase C, imaginary only.
constant_impedance_AN	complex	Ohm	I	Constant impedance load on phase A.
constant_impedance_BN	complex	Ohm	I	Constant impedance load on phase B.
constant_impedance_CN	complex	Ohm	I	Constant impedance load on phase C.
constant_impedance_AN_real	double	Ohm	I	Constant impedance load on phase A, real only.
constant_impedance_BN_real	double	Ohm	I	Constant impedance load on phase B, real only.
constant_impedance_CN_real	double	Ohm	I	Constant impedance load on phase C, real only.
constant_impedance_AN_reac	double	Ohm	I	Constant impedance load on phase A, imaginary only.
constant_impedance_BN_reac	double	Ohm	I	Constant impedance load on phase B, imaginary only.
constant_impedance_CN_reac	double	Ohm	I	Constant impedance load on phase C, imaginary only.

Explicit Delta-Connected Load Properties

These properties specify ZIP loads on an explicit delta (phase-to-phase) connection, regardless of the object's phase configuration. They are input only. The _real and _reac suffixed variants provide access to the real and imaginary components individually.

Table 4: load table 4
Property Name	Type	Unit	I/O	Description
constant_power_AB	complex	VA	I	Constant power load on phases AB.
constant_power_BC	complex	VA	I	Constant power load on phases BC.
constant_power_CA	complex	VA	I	Constant power load on phases CA.
constant_power_AB_real	double	W	I	Constant power load on phases AB, real only.
constant_power_BC_real	double	W	I	Constant power load on phases BC, real only.
constant_power_CA_real	double	W	I	Constant power load on phases CA, real only.
constant_power_AB_reac	double	VAr	I	Constant power load on phases AB, imaginary only.
constant_power_BC_reac	double	VAr	I	Constant power load on phases BC, imaginary only.
constant_power_CA_reac	double	VAr	I	Constant power load on phases CA, imaginary only.
constant_current_AB	complex	A	I	Constant current load on phases AB.
constant_current_BC	complex	A	I	Constant current load on phases BC.
constant_current_CA	complex	A	I	Constant current load on phases CA.
constant_current_AB_real	double	A	I	Constant current load on phases AB, real only.
constant_current_BC_real	double	A	I	Constant current load on phases BC, real only.
constant_current_CA_real	double	A	I	Constant current load on phases CA, real only.
constant_current_AB_reac	double	A	I	Constant current load on phases AB, imaginary only.
constant_current_BC_reac	double	A	I	Constant current load on phases BC, imaginary only.
constant_current_CA_reac	double	A	I	Constant current load on phases CA, imaginary only.
constant_impedance_AB	complex	Ohm	I	Constant impedance load on phases AB.
constant_impedance_BC	complex	Ohm	I	Constant impedance load on phases BC.
constant_impedance_CA	complex	Ohm	I	Constant impedance load on phases CA.
constant_impedance_AB_real	double	Ohm	I	Constant impedance load on phases AB, real only.
constant_impedance_BC_real	double	Ohm	I	Constant impedance load on phases BC, real only.
constant_impedance_CA_real	double	Ohm	I	Constant impedance load on phases CA, real only.
constant_impedance_AB_reac	double	Ohm	I	Constant impedance load on phases AB, imaginary only.
constant_impedance_BC_reac	double	Ohm	I	Constant impedance load on phases BC, imaginary only.
constant_impedance_CA_reac	double	Ohm	I	Constant impedance load on phases CA, imaginary only.

Base Power and ZIP Fraction Properties

These properties provide an alternative way to specify ZIP loads using a base power value with fraction and power factor breakdowns per phase, following the same conventions as the ZIPload object. When base_power is nonzero for a phase, it overrides the corresponding constant_power, constant_current, and constant_impedance values for that phase.

Table 5: load table 5
Property Name	Type	Unit	I/O	Description
base_power_A	double	VA	I	Nominal power on phase A before applying ZIP fractions.
base_power_B	double	VA	I	Nominal power on phase B before applying ZIP fractions.
base_power_C	double	VA	I	Nominal power on phase C before applying ZIP fractions.
power_pf_A	double	pu	I	Power factor of the phase A constant power portion of load.
current_pf_A	double	pu	I	Power factor of the phase A constant current portion of load.
impedance_pf_A	double	pu	I	Power factor of the phase A constant impedance portion of load.
power_pf_B	double	pu	I	Power factor of the phase B constant power portion of load.
current_pf_B	double	pu	I	Power factor of the phase B constant current portion of load.
impedance_pf_B	double	pu	I	Power factor of the phase B constant impedance portion of load.
power_pf_C	double	pu	I	Power factor of the phase C constant power portion of load.
current_pf_C	double	pu	I	Power factor of the phase C constant current portion of load.
impedance_pf_C	double	pu	I	Power factor of the phase C constant impedance portion of load.
power_fraction_A	double	pu	IO	Constant power fraction of base power on phase A. May be overwritten if ZIP fractions do not sum to 1.
current_fraction_A	double	pu	I	Constant current fraction of base power on phase A.
impedance_fraction_A	double	pu	I	Constant impedance fraction of base power on phase A.
power_fraction_B	double	pu	IO	Constant power fraction of base power on phase B. May be overwritten if ZIP fractions do not sum to 1.
current_fraction_B	double	pu	I	Constant current fraction of base power on phase B.
impedance_fraction_B	double	pu	I	Constant impedance fraction of base power on phase B.
power_fraction_C	double	pu	IO	Constant power fraction of base power on phase C. May be overwritten if ZIP fractions do not sum to 1.
current_fraction_C	double	pu	I	Constant current fraction of base power on phase C.
impedance_fraction_C	double	pu	I	Constant impedance fraction of base power on phase C.

Measurement Properties

These properties are computed by the simulation and are output only. Note that the measured_voltage properties lag by one powerflow iteration; for the most current values, read the corresponding voltage_* properties from the parent node object directly.

Table 6: load table 6
Property Name	Type	Unit	I/O	Description
measured_voltage_A	complex	V	O	Measured voltage on phase A.
measured_voltage_B	complex	V	O	Measured voltage on phase B.
measured_voltage_C	complex	V	O	Measured voltage on phase C.
measured_voltage_AB	complex	V	O	Measured voltage on delta-phase AB.
measured_voltage_BC	complex	V	O	Measured voltage on delta-phase BC.
measured_voltage_CA	complex	V	O	Measured voltage on delta-phase CA.
measured_power_A	complex	VA	O	Measured power on phase A.
measured_power_B	complex	VA	O	Measured power on phase B.
measured_power_C	complex	VA	O	Measured power on phase C.
measured_power	complex	VA	O	Total measured power.

Deltamode / In-Rush Properties

These properties control the numerical integration method used for in-rush current calculations during deltamode simulation. If left as UNDEFINED, the object inherits the global integration method setting.

Table 7: load table 7
Property Name	Type	Unit	I/O	Description
inrush_integration_method_capacitance	enumeration	N/A	I	Selected integration method to use for capacitive elements of the load. Valid values: `NONE`, `UNDEFINED`, `TRAPEZOIDAL`, `BACKWARD_EULER`.
inrush_integration_method_inductance	enumeration	N/A	I	Selected integration method to use for inductive elements of the load. Valid values: `NONE`, `UNDEFINED`, `TRAPEZOIDAL`, `BACKWARD_EULER`.

Load State of Development

Load is considered a well developed and validated model, with a number of features. Additional features may be included as needed.