Link

The link object is a connection between nodes in a distribution system. The link object is not directly useful, but is the basis for objects associated with overhead lines, underground lines, triplex lines, transformers, regulators, switches, and fuses.

For technical details on link modeling, see Lines and Transformers Theory.

Example Link

A link only requires three parameters to be specified by default. Most of the actual functionality comes through derived objects such as lines, transformers, and switches.

object link {
    name Node1toNode2;
    phases ABC;
    from Node1;
    to Node2;
}

Link Object Parameters

link 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 Configuration Properties

These properties define the basic topology and operating state of the link.

Table 1: link table 1

Property Name	Type	Unit	I/O	Description
status	enumeration	N/A	IO	Operating status of the link. Primarily used for switches and fuses, but may be used to remove any link from service. In the FBS solver, this directly controls forward/back sweep participation. Valid values: OPEN, CLOSED.
from	object	N/A	I	Source-side node of the link. Must reference a node-based powerflow object.
to	object	N/A	I	Load-side node of the link. Must reference a node-based powerflow object.
mean_repair_time	double	s	I	Time after a fault has cleared before the object will be restored to service. Used by the reliability module.

Power Flow Measurements

These properties are computed by the simulation during postsync and are output only. They represent power flowing through the link with respect to the from and to node designations.

Table 2: link table 2

Property Name	Type	Unit	I/O	Description
power_in	complex	VA	IO	Total three-phase power flowing into the link from the from node.
power_out	complex	VA	IO	Total three-phase power flowing out of the link toward the to node.
power_out_real	double	W	IO	Real component of power_out.
power_losses	complex	VA	IO	Total three-phase power loss across the link.
power_in_A	complex	VA	IO	Power flowing into the link on phase A.
power_in_B	complex	VA	IO	Power flowing into the link on phase B.
power_in_C	complex	VA	IO	Power flowing into the link on phase C.
power_out_A	complex	VA	IO	Power flowing out of the link on phase A.
power_out_B	complex	VA	IO	Power flowing out of the link on phase B.
power_out_C	complex	VA	IO	Power flowing out of the link on phase C.
power_losses_A	complex	VA	IO	Power loss on phase A.
power_losses_B	complex	VA	IO	Power loss on phase B.
power_losses_C	complex	VA	IO	Power loss on phase C.

Current Measurements

These properties are computed by the simulation during postsync and are output only. They represent the current flowing through the link. Note: these have not been fully validated for every derived link type.

Table 3: link table 3

Property Name	Type	Unit	I/O	Description
current_in_A	complex	A	O	Current flowing into the link on phase A, with respect to the from node.
current_in_B	complex	A	O	Current flowing into the link on phase B, with respect to the from node.
current_in_C	complex	A	O	Current flowing into the link on phase C, with respect to the from node.
current_out_A	complex	A	O	Current flowing out of the link on phase A, with respect to the to node.
current_out_B	complex	A	O	Current flowing out of the link on phase B, with respect to the to node.
current_out_C	complex	A	O	Current flowing out of the link on phase C, with respect to the to node.

Fault Current and Voltage Properties

These properties are populated by the fault analysis subsystem (via the reliability module or eventgen object) and are output only.

Table 4: link table 4

Property Name	Type	Unit	I/O	Description
fault_current_in_A	complex	A	IO	Fault current flowing into the link on phase A.
fault_current_in_B	complex	A	IO	Fault current flowing into the link on phase B.
fault_current_in_C	complex	A	IO	Fault current flowing into the link on phase C.
fault_current_out_A	complex	A	IO	Fault current flowing out of the link on phase A.
fault_current_out_B	complex	A	IO	Fault current flowing out of the link on phase B.
fault_current_out_C	complex	A	IO	Fault current flowing out of the link on phase C.
fault_voltage_A	complex	V	O	Fault voltage on phase A.
fault_voltage_B	complex	V	O	Fault voltage on phase B.
fault_voltage_C	complex	V	O	Fault voltage on phase C.

Dispatch Properties

These properties support scheduled power dispatch through the link. When set_pdispatch is set to true, the simulation computes pdispatch as the average of power_in and power_out real components and resets pdispatch_offset to zero. The set_pdispatch flag is automatically cleared after triggering.

Table 5: link table 5

Property Name	Type	Unit	I/O	Description
pdispatch	double	W	IO	Scheduled real power flow from from to to. Overwritten when set_pdispatch is triggered.
pdispatch_offset	double	W	IO	Offset applied to the scheduled power flow. Reset to zero when set_pdispatch is triggered.
set_pdispatch	bool	N/A	IO	When set to true, triggers computation of pdispatch as the average of real power in and out. Automatically reset to false after triggering.

Flow Direction and Overload Status

Table 6: link table 6

Property Name	Type	Unit	I/O	Description
flow_direction	set	N/A	IO	Per-phase flag indicating the direction of power flow relative to the from and to designations. Computed during postsync from power flow results. Multiple flags are combined as a set. 0x000 - UNKNOWN - Flow direction is indeterminate. 0x001 - AF - Phase A power flows from from to to. 0x002 - AR - Phase A power flows from to to from (reverse). 0x003 - AN - No power flow on phase A. 0x010 - BF - Phase B power flows from from to to. 0x020 - BR - Phase B power flows from to to from (reverse). 0x030 - BN - No power flow on phase B. 0x100 - CF - Phase C power flows from from to to. 0x200 - CR - Phase C power flows from to to from (reverse). 0x300 - CN - No power flow on phase C.
overloaded_status	bool	N/A	O	Indicates whether the link has exceeded its thermal rating. Set to true if any phase current exceeds its continuous rating, or if transformer power exceeds its kVA rating.

Thermal Rating Properties

These properties define the current (for lines) or power (for transformers) limits of the link. They are input only. Limit checking is only active when the global use_link_limits flag is enabled and the link is a line or transformer (switches, fuses, regulators, and sectionalizers are excluded). Default values are 1000 A continuous and 2000 A emergency.

Table 7: link table 7

Property Name	Type	Unit	I/O	Description
continuous_rating_A	double	A	I	Continuous current rating for phase A.
continuous_rating_B	double	A	I	Continuous current rating for phase B.
continuous_rating_C	double	A	I	Continuous current rating for phase C.
emergency_rating_A	double	A	I	Emergency current rating for phase A.
emergency_rating_B	double	A	I	Emergency current rating for phase B.
emergency_rating_C	double	A	I	Emergency current rating for phase C.

Transient Simulations / In-Rush Properties

These properties control the numerical integration method and convergence tolerance used for in-rush current calculations during transient (deltamode) simulation. If the integration method is left as UNDEFINED, the object inherits the global integration method setting. These properties are only used when both transient and in-rush calculations are enabled.

Table 8: link table 8

Property Name	Type	Unit	I/O	Description
inrush_convergence_value	double	V	I	Convergence tolerance for transient in-rush completion, measured as the change in line voltage drop magnitude between iterations. Default is 0.0001 V.
inrush_integration_method_capacitance	enumeration	N/A	I	Integration method for capacitive elements of the link. Valid values: NONE, UNDEFINED, TRAPEZOIDAL, BACKWARD_EULER.
inrush_integration_method_inductance	enumeration	N/A	I	Integration method for inductive elements of the link. Valid values: NONE, UNDEFINED, TRAPEZOIDAL, BACKWARD_EULER.

Internal Properties

These properties are published with PA_HIDDEN and are intended for internal or developer use. They support triplex line neutral current calculations.

Table 9: link table 9

Property Name	Type	Unit	I/O	Description
triplex_neutral_1_value	complex	N/A	O	Internal triplex neutral coupling coefficient for phase 1.
triplex_neutral_2_value	complex	N/A	O	Internal triplex neutral coupling coefficient for phase 2.

Link State of Development

Link is considered a highly developed and validated model.