Node

The node object is equivalent to a bus of the distribution system. It provides a connection point for link-based objects and a point of known voltages on the system. Three-phase voltage is typically available in either wye-connected or delta-connected form. Wye-connected voltages are contained in voltage_A, voltage_B, and voltage_C. Delta-connected voltages are available in voltage_AB, voltage_BC, and voltage_CA.

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

Example Node

A minimalist node could be created with

object node {
    name NodeOne;
    phases ABC;
    nominal_voltage 7200.0;
}

which is the same as specifying

object node {
    name NodeOne;
    phases ABC;
    nominal_voltage 7200.0;
    voltage_A 7200.0+0d;
    voltage_B 7200.0-120.0d;
    voltage_C 7200.0+120.0d;
    bustype PQ;
}

Node Parameters

node objects are derived from powerflow_object objects, so any parameters of the powerflow_object 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

These properties control the fundamental bus configuration and solver behavior of the node.

Table 1: node table 1
Property Name	Type	Unit	I/O	Description
bustype	enumeration	N/A	I	Defines the bus type for powerflow analysis. The bus type distinction is primarily used by the Newton-Raphson solver. In Forward-Back Sweep mode, the first node initialized is automatically promoted to `SWING`. Valid values: - `PQ` — Constant power bus (default). - `PV` — Voltage-controlled (magnitude) bus. - `SWING` — Infinite bus / voltage reference for the system. - `SWING_PQ` — Swing bus that can revert to PQ behavior when used with a `fault_check` object in `grid_association` mode.
busflags	set	N/A	I	Internal flag set for topology analysis. `HASSOURCE` is set by default on all nodes and is unused at this time (the propagation logic that would clear it requires the SUPPORT_OUTAGES compile flag, which is not enabled in standard builds). ISSOURCE marks a bus as an independent source entry point for fault_check grid association mode. Valid values: `HASSOURCE`, `ISSOURCE`.
reference_bus	object	N/A	I	Reference node from which this node inherits its frequency value. Used in the Forward-Back Sweep solver during presync.
maximum_voltage_error	double	V	I	Maximum voltage error threshold for convergence checks. If left at zero, it is automatically derived from `nominal_voltage` multiplied by the global `default_maximum_voltage_error`.
mean_repair_time	double	s	I	Time after a fault clears before the object is considered back in service. Primarily used for reliability module interactions.

Voltage Properties

These properties hold the bus voltage phasors. Voltages may be specified in rectangular (7200.0+0.0j) or polar (7200.0+0.0d) format. The _A, _B, _C variants are phase-to-ground (wye) voltages and serve as both user-settable initial conditions and simulation outputs updated each powerflow iteration. The _AB, _BC, _CA variants are line-to-line (delta) voltages derived from the corresponding phase-to-ground differences; setting them directly is not recommended.

Table 2: node table 2
Property Name	Type	Unit	I/O	Description
voltage_A	complex	V	IO	Bus voltage on phase A to ground.
voltage_B	complex	V	IO	Bus voltage on phase B to ground.
voltage_C	complex	V	IO	Bus voltage on phase C to ground.
voltage_AB	complex	V	IO	Line-to-line voltage across phases AB. Computed as `voltage_A - voltage_B`.
voltage_BC	complex	V	IO	Line-to-line voltage across phases BC. Computed as `voltage_B - voltage_C`.
voltage_CA	complex	V	IO	Line-to-line voltage across phases CA. Computed as `voltage_C - voltage_A`.

Service Status Properties

These properties track whether the node is in service and how long it has been connected or disconnected. The service_status_double property provides a schedule-friendly numeric override for the enumeration-based service_status.

Table 3: node table 3
Property Name	Type	Unit	I/O	Description
service_status	enumeration	N/A	IO	Indicates whether the node is in service or disconnected. Valid values: `IN_SERVICE`, `OUT_OF_SERVICE`.
service_status_double	double	N/A	I	Double-valued override for `service_status`, intended for use with schedules. Set to `1.0` for `IN_SERVICE`, `0.0` for `OUT_OF_SERVICE`. The default value of `-1.0` disables the override. Other values cause an error.
previous_uptime	double	min	IO	Previous uptime duration between the last two disconnects of this node.
current_uptime	double	min	IO	Elapsed time since the most recent disconnect of this node. Set to `-1.0` when the node is out of service.

Frequency Measurement Properties

These properties configure and report frequency and angle measurements during transient simulation. The measurement method is selected by frequency_measure_type; if set to NONE (the default unless overridden by a module-level global setting), no measurements are performed. The SIMPLE method uses a first-order transducer model controlled by sfm_Tf. The PLL method uses a phase-locked loop controlled by pll_Kp and pll_Ki.

The four configuration properties are input only. The seven measured_* properties are output.

Table 4: node table 4
Property Name	Type	Unit	I/O	Description
frequency_measure_type	enumeration	N/A	I	Selects the frequency measurement method. Valid values: `NONE`, `SIMPLE`, `PLL`.
sfm_Tf	double	s	I	Transducer time constant for the `SIMPLE` method.
pll_Kp	double	pu	I	Proportional gain for the `PLL` method.
pll_Ki	double	pu	I	Integration gain for the `PLL` method.
measured_angle_A	double	rad	O	Measured bus voltage angle on phase A.
measured_angle_B	double	rad	O	Measured bus voltage angle on phase B.
measured_angle_C	double	rad	O	Measured bus voltage angle on phase C.
measured_frequency_A	double	Hz	O	Measured frequency on phase A.
measured_frequency_B	double	Hz	O	Measured frequency on phase B.
measured_frequency_C	double	Hz	O	Measured frequency on phase C.
measured_frequency	double	Hz	O	Measured frequency averaged across all energized phases.

Grid Friendly Appliance (GFA) Properties

These properties configure Grid Friendly Appliance-type voltage and frequency trip/reconnect logic. When GFA_enable is true, the node monitors its voltage and frequency against configurable trip thresholds. If a violation persists longer than the corresponding disconnect time, the node is tripped out of service. After the violation clears, the node remains disconnected for GFA_reconnect_time before being restored.

The first eight properties are input-only configuration parameters. GFA_status and GFA_trip_method are both input and output — they can be set initially but are updated by the simulation at runtime.

Table 5: node table 5
Property Name	Type	Unit	I/O	Description
GFA_enable	bool	N/A	I	Enables or disables GFA-type functionality on this node.
GFA_freq_low_trip	double	Hz	I	Low frequency trip point.
GFA_freq_high_trip	double	Hz	I	High frequency trip point.
GFA_volt_low_trip	double	pu	I	Low voltage trip point.
GFA_volt_high_trip	double	pu	I	High voltage trip point.
GFA_freq_disconnect_time	double	s	I	Duration a frequency violation must persist before disconnection.
GFA_volt_disconnect_time	double	s	I	Duration a voltage violation must persist before disconnection.
GFA_reconnect_time	double	s	I	Delay after a trip event before the node is restored to service.
GFA_status	bool	N/A	IO	Whether GFA considers the node in service (`true`) or tripped (`false`).
GFA_trip_method	enumeration	N/A	IO	Reason for the most recent GFA trip. Valid values: `NONE`, `UNDER_FREQUENCY`, `OVER_FREQUENCY`, `UNDER_VOLTAGE`, `OVER_VOLTAGE`.

Topology and Swing Status Properties

These properties expose the node's topological parent relationship and its runtime swing-bus behavior. Neither is meaningfully user-configurable — topological_parent is determined during initialization and behaving_as_swing is recomputed every postsync. Both are effectively output-only or informational.

Table 6: node table 6
Property Name	Type	Unit	I/O	Description
topological_parent	object	N/A	O	Topological parent of this node as determined during initialization. Reflects the object's `parent` field.
behaving_as_swing	bool	N/A	O	Whether this bus is currently acting as a reference voltage source. Only meaningful for `SWING` or `SWING_PQ` bus types.

Internal Properties

These properties are published with PA_HIDDEN and are intended for internal or developer use.

Table 7: node table 7
Property Name	Type	Unit	I/O	Description
current_A	complex	A	O	The current load on phase A (wye) or phase AB (delta) of the node. Typically handled through the load object; modification is not recommended.
current_B	complex	A	O	The current load on phase B (wye) or phase BC (delta) of the node. Typically handled through the load object; modification is not recommended.
current_C	complex	A	O	The current load on phase C (wye) or phase CA (delta) of the node. Typically handled through the load object; modification is not recommended.
power_A	complex	VA	O	The power load on phase A (wye) or phase AB (delta) of the node. Typically handled through the load object; modification is not recommended.
power_B	complex	VA	O	The power load on phase B (wye) or phase BC (delta) of the node. Typically handled through the load object; modification is not recommended.
power_C	complex	VA	O	The power load on phase C (wye) or phase CA (delta) of the node. Typically handled through the load object; modification is not recommended.
shunt_A	complex	S	O	The shunt admittance load on phase A (wye) or phase AB (delta) of the node. Typically handled through the load object; modification is not recommended.
shunt_B	complex	S	O	The shunt admittance load on phase B (wye) or phase BC (delta) of the node. Typically handled through the load object; modification is not recommended.
shunt_C	complex	S	O	The shunt admittance load on phase C (wye) or phase CA (delta) of the node. Typically handled through the load object; modification is not recommended.
prerotated_current_A	complex	A	O	Deltamode bus current injection on phase A (in = positive). Not rotated by powerflow for off-nominal frequency. Accumulator only.
prerotated_current_B	complex	A	O	Deltamode bus current injection on phase B (in = positive). Not rotated by powerflow for off-nominal frequency. Accumulator only.
prerotated_current_C	complex	A	O	Deltamode bus current injection on phase C (in = positive). Not rotated by powerflow for off-nominal frequency. Accumulator only.
deltamode_generator_current_A	complex	A	O	Deltamode direct generator current injection on phase A (in = positive). May be overwritten internally. Accumulator only.
deltamode_generator_current_B	complex	A	O	Deltamode direct generator current injection on phase B (in = positive). May be overwritten internally. Accumulator only.
deltamode_generator_current_C	complex	A	O	Deltamode direct generator current injection on phase C (in = positive). May be overwritten internally. Accumulator only.
deltamode_PGenTotal	complex	N/A	—	Deltamode power value for a diesel generator. Accumulator only.
deltamode_full_Y_matrix	complex_array	N/A	—	Deltamode full admittance matrix exposed for generator Norton equivalent interactions.
deltamode_full_Y_all_matrix	complex_array	N/A	O	Deltamode full admittance matrix (including all contributions) exposed for generator Norton equivalent interactions.
NR_powerflow_parent	object	N/A	—	Actual powerflow parent in Newton-Raphson. Used by generators accessing child objects.
current_inj_A	complex	A	O	Bus current injection on phase A (in = positive). Not rotated for off-nominal frequency. Accumulator only.
current_inj_B	complex	A	O	Bus current injection on phase B (in = positive). Not rotated for off-nominal frequency. Accumulator only.
current_inj_C	complex	A	O	Bus current injection on phase C (in = positive). Not rotated for off-nominal frequency. Accumulator only.
current_AB	complex	A	O	Bus current delta-connected injection on phases AB (in = positive). Accumulator only.
current_BC	complex	A	O	Bus current delta-connected injection on phases BC (in = positive). Accumulator only.
current_CA	complex	A	O	Bus current delta-connected injection on phases CA (in = positive). Accumulator only.
current_AN	complex	A	O	Bus current wye-connected injection on phase A (in = positive). Accumulator only.
current_BN	complex	A	O	Bus current wye-connected injection on phase B (in = positive). Accumulator only.
current_CN	complex	A	O	Bus current wye-connected injection on phase C (in = positive). Accumulator only.
power_AB	complex	VA	O	Bus power delta-connected injection on phases AB (in = positive). Accumulator only.
power_BC	complex	VA	O	Bus power delta-connected injection on phases BC (in = positive). Accumulator only.
power_CA	complex	VA	O	Bus power delta-connected injection on phases CA (in = positive). Accumulator only.
power_AN	complex	VA	O	Bus power wye-connected injection on phase A (in = positive). Accumulator only.
power_BN	complex	VA	O	Bus power wye-connected injection on phase B (in = positive). Accumulator only.
power_CN	complex	VA	O	Bus power wye-connected injection on phase C (in = positive). Accumulator only.
shunt_AB	complex	S	O	Bus shunt delta-connected admittance on phases AB. Accumulator only.
shunt_BC	complex	S	O	Bus shunt delta-connected admittance on phases BC. Accumulator only.
shunt_CA	complex	S	O	Bus shunt delta-connected admittance on phases CA. Accumulator only.
shunt_AN	complex	S	O	Bus shunt wye-connected admittance on phase A. Accumulator only.
shunt_BN	complex	S	O	Bus shunt wye-connected admittance on phase B. Accumulator only.
shunt_CN	complex	S	O	Bus shunt wye-connected admittance on phase C. Accumulator only.
residential_nominal_current_A	complex	A	O	Posted current on phase A from a residential object, if attached.
residential_nominal_current_B	complex	A	O	Posted current on phase B from a residential object, if attached.
residential_nominal_current_C	complex	A	O	Posted current on phase C from a residential object, if attached.
residential_nominal_current_A_real	double	A	O	Posted current on phase A from a residential object, real component.
residential_nominal_current_A_imag	double	A	O	Posted current on phase A from a residential object, imaginary component.
residential_nominal_current_B_real	double	A	O	Posted current on phase B from a residential object, real component.
residential_nominal_current_B_imag	double	A	O	Posted current on phase B from a residential object, imaginary component.
residential_nominal_current_C_real	double	A	O	Posted current on phase C from a residential object, real component.
residential_nominal_current_C_imag	double	A	O	Posted current on phase C from a residential object, imaginary component.
house_present	bool	N/A	O	Flag indicating whether a house object is attached to this node.
Norton_dynamic	bool	N/A	—	Flag indicating a Norton-equivalent connection is present. Used for generators and deltamode.
Norton_dynamic_child	bool	N/A	—	Flag indicating a Norton-equivalent connection is made by a childed node object. Used for generators and deltamode.
generator_dynamic	bool	N/A	—	Flag indicating a voltage-sourcing or swing-type generator is present. Used for generators and deltamode.
reset_disabled_island_state	bool	N/A	O	Deltamode/multi-island flag used to reset disabled status and reform an island.

Node State of Development

Node is considered a highly developed and validated model.