Line

The line object represents power lines in a distribution system. The line object has two implementations: overhead_line, and underground_line. Each line must be called appropriately. Information about the particular line type will be contained in other objects called line_configuration.

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

line-based objects inherit properties from the link object just covered. Two new properties are also added: configuration and length.

Typical usage of an overhead line would be

object overhead_line {
    name Node1toNode2;
    phases ABC;
    from Node1;
    to Node2;
    length 5280;
    configuration Best_overhead_line_cfg;
    }

and the typical usage of the underground line would be

object underground_line {
    name Node1toNode2;
    phases ABC;
    from Node1;
    to Node2;
    length 5280;
    configuration An_underground_line_cfg;
    }

Line Parameters

Properties

line objects are derived from link objects, so any parameters of the link 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).

Table 1: line table 1
Property Name	Type	Unit	I/O	Description
configuration	object	N/A	I	Name or reference to the particular configuration object that describes the properties of the line object.
length	double	ft	I	Length of the line object.

Line State of Development

Line is considered a highly developed and validated model in terms of powerflow solutions, however, models may be developed to include more advanced features in the future.

Line Configuration

Both underground_line and overhead_line objects take line configuration information to describe the particular line being implemented, or they can be described in their raw z-matrix values. A typical line_configuration object would be implemented as

object line_configuration {
    name line_config_A;
    conductor_A overhead_line_conductor_100;
    conductor_B overhead_line_conductor_100;
    conductor_C overhead_line_conductor_100;
    conductor_N overhead_line_conductor_101;
    spacing line_spacing_200;
    }

or

object line_configuration {
       name line_config_B;
       z11 0.45+1.07j;
       z12 0.15+0.50j;
       z13 0.15+0.38j;
       z21 0.15+0.50j;
       z22 0.46+1.04j;
       z23 0.15+0.42j;
       z31 0.15+0.38j;
       z32 0.15+0.42j;
       z33 0.46+1.06j;
       }

If you want to factor in line capacitance effects, the line_configuration can be extended to:

object line_configuration {
       name line_config_B;
       z11 0.45+1.07j;
       z12 0.15+0.50j;
       z13 0.15+0.38j;
       z21 0.15+0.50j;
       z22 0.46+1.04j;
       z23 0.15+0.42j;
       z31 0.15+0.38j;
       z32 0.15+0.42j;
       z33 0.46+1.06j;
       c11 198.52;
       c22 198.52;
       c33 198.52;
       }

Note that for capacitance calculations to be included in the powerflow, the module-level directive must be included:

module powerflow {
   line_capacitance true;
}

It is highly recommended to use the line_spacing and overhead_line_conductor or underground_line_conductor objects and let the internal equations calculate the capacitance (and impedance) for the user.

Line Configuration Parameters

Properties

line_configuration does not declare inherited parent classes.

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

Table 2: line table 2
Property Name	Type	Unit	I/O	Description
conductor_A	object	N/A	I	Object describing the conductor of phase A in the overhead or underground line object. (`overhead_line_conductor` or `underground_line_conductor`)
conductor_B	object	N/A	I	Object describing the conductor of phase B in the overhead or underground line object. (`overhead_line_conductor` or `underground_line_conductor`)
conductor_C	object	N/A	I	Object describing the conductor of phase C in the overhead or underground line object. (`overhead_line_conductor` or `underground_line_conductor`)
conductor_N	object	N/A	I	Object describing the conductor of phase N in the overhead or underground line object. (`overhead_line_conductor` or `underground_line_conductor`)
spacing	object	N/A	I	`line_spacing` object describing how the conductors are physically oriented on the pole or in the bundle.

Z-matrix and Capacitance Matrix Properties

Describes the z-matrix and c-matrix directly for either underground or overhead lines instead of using the geometric configurations (This will over-write geometric configurations). For this notation, index 1 is phase A, 2 is phase B, and 3 is phase C. So element z12 represents the mutual/cross coupling impedance between phase A and phase B of this line configuration.

Table 3: line table 3
Property Name	Type	Unit	I/O
z11	complex	Ohm/mile	I
z12	complex	Ohm/mile	I
z13	complex	Ohm/mile	I
z21	complex	Ohm/mile	I
z22	complex	Ohm/mile	I
z23	complex	Ohm/mile	I
z31	complex	Ohm/mile	I
z32	complex	Ohm/mile	I
z33	complex	Ohm/mile	I
c11	double	nF/mile	I
c12	double	nF/mile	I
c13	double	nF/mile	I
c21	double	nF/mile	I
c22	double	nF/mile	I
c23	double	nF/mile	I
c31	double	nF/mile	I
c32	double	nF/mile	I
c33	double	nF/mile	I

Ampere Rating Properties

Table 4: line table 4
Property Name	Type	Unit	I/O	Description
rating.summer.continuous	double	A	I	Amp rating in summer, continuous
rating.summer.emergency	double	A	I	Amp rating in summer, short term
rating.winter.continuous	double	A	I	Amp rating in winter, continuous
rating.winter.emergency	double	A	I	Amp rating in winter, short term

Line Spacing

The line spacing object describe how the individual conductors of a distribution line are arranged underground or on the support pole. A typical implementation of a line_spacing object is

object line_spacing {
    name line_spacing_200;
    distance_AB 2.5;
    distance_BC 4.5;
    distance_AC 7.0;
    distance_AN 5.656854;
    distance_BN 4.272002;
    distance_CN 5.0;
    }

Line Spacing Parameters

Properties

line_spacing does not declare inherited parent classes.

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

Table 5: line table 5
Property Name	Type	Unit	I/O	Description
distance_AB	double	ft	I	Distance between conductors of phase A and phase B.
distance_BC	double	ft	I	Distance between conductors of phase B and phase C.
distance_AC	double	ft	I	Distance between conductors of phase C and phase A.
distance_AN	double	ft	I	Distance between conductors of phase A and the neutral phase.
distance_BN	double	ft	I	Distance between conductors of phase B and the neutral phase.
distance_CN	double	ft	I	Distance between conductors of phase C and the neutral phase.
distance_AE	double	ft	I	Distance between conductor of phase A and the earth (ground).
distance_BE	double	ft	I	Distance between conductor of phase B and the earth (ground).
distance_CE	double	ft	I	Distance between conductor of phase C and the earth (ground).
distance_NE	double	ft	I	Distance between conductor of the neutral phase (phase N) and the earth (ground).

Line Spacing State of Development

Line Spacing is considered a highly developed and validated model in terms of powerflow solutions, however, models may be developed to include more advanced features in the future.

Overhead Line

Overhead lines are one of three specific line types incorporated into the powerflow distribution-level module. The overhead_line object will take spacing and conductor parameters and translate those values to appropriate impedance matrices based for the specific overhead transmission line configuration. A typical overhead line would be written as

object overhead_line{
    phases "ABCN";
    name 701-802;
    from node_701;
    to load_802;
    length 125960;
    configuration line_config_A;
    }

overhead_line objects inherit from the line object and inherit all of its properties. overhead_line objects primarily translate the configuration options specified into a circuit equivalent, so not further properties than those provided by line are required.

Overhead Line State of Development

Overhead Line is considered a highly developed and validated model in terms of powerflow solutions, however, models may be developed to include more advanced features in the future.

Overhead Line Conductor

For overhead lines, the line_configuration object must specify the overhead line conductor types used in the particular setup. A typical overhead_line_conductor would be implemented as

object overhead_line_conductor {
    name overhead_line_conductor_100;
    geometric_mean_radius .00446;
    resistance 1.12;
    }

Overhead Line Conductor Parameters

Properties

overhead_line_conductor does not declare inherited parent classes.

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

Table 6: line table 6
Property Name	Type	Unit	I/O	Description
geometric_mean_radius	double	ft	I	The GMR of the wire.
resistance	double	Ohm/mile	I	The resistance of the particular conductor, incorporating size and material effects.
diameter	double	in	I	Diameter of the conductor - used for capacitance calculations.
rating.summer.continuous	double	A	I	The continuous rating for the conductor during summer month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.summer.emergency	double	A	I	The emergency (short time) rating for the conductor during summer month usage. TODO - Status - This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.winter.continuous	double	A	I	The continuous rating for the conductor during winter month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.winter.emergency	double	A	I	The emergency (short time) rating for the conductor during winter month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality

Overhead Line Conductor State of Development

Overhead Line Conductor is considered a highly developed and validated model.

Underground Line

Underground lines represent burial distribution cables in a powerflow system. In terms of GridLAB-D™ implementation, they are nearly identical to the overhead_line objects. A typical underground_line object would be written as

object underground_line {
    phases "ABC";
    name 703-727;
    from node_703;
    to load_827;
    length 240;
    configuration line_config_7241;
    }

As with overhead_line objects, underground_line objects inherit all of their properties from the line object. The underground_line object again serves as a method to choose the appropriate translation algorithms to take the physical parameters of the system and create an equivalent model. As such, it has no new properties either.

Underground Line State of Development

Underground Line is considered a highly developed and validated model in terms of powerflow solutions, however, models may be developed to include more advanced features in the future.

Underground Line Conductor

Underground lines often contain concentric shielding layers around the central conductor. As a result, they require more parameters than the overhead_line_conductor objects to fully describe them. A typical underground_line_object is:

object underground_line_conductor { 
    name ug_conduct_7210;
    outer_diameter 1.980000;
    conductor_gmr 0.036800;
    conductor_diameter 1.150000;
    conductor_resistance 0.105000;
    neutral_gmr 0.003310;
    neutral_resistance 5.903000;
    neutral_diameter 0.102000;
    neutral_strands 20.000000;
    shield_gmr 0.000000;
    shield_resistance 0.000000;
    }

Underground Line Conductor Parameters

Properties

underground_line_conductor does not declare inherited parent classes.

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

Table 7: line table 7
Property Name	Type	Unit	I/O	Description
outer_diameter	double	in	I	Diameter of the outside of the cable, including jacketing and shielding.
conductor_gmr	double	ft	I	Geometric mean radius of the conductor at the center of the concentric cable.
conductor_diameter	double	in	I	Diameter of the conductor at the center of the concentric cable.
conductor_resistance	double	Ohm/mile	I	Resistance of the conductor at the center of the concentric cable.
neutral_gmr	double	ft	I	Geometric mean radius of the concentric neutral of the cable.
neutral_diameter	double	in	I	Diameter of the concentric neutral of the cable.
neutral_resistance	double	Ohm/mile	I	Resistance of the concentric neutral of the cable.
neutral_strands	int16	N/A	I	Number of strands composing the concentric neutral conductor.
shield_thickness	double	in	I	The thickness of Tape shield in inches
shield_diameter	double	in	I	The outside diameter of Tape shield in inches
insulation_relative_permitivitty	double	unit	I	Permitivitty of insulation, relative to air
shield_gmr	double	ft	I	Geometric mean radius of the shielding of the cable.
shield_resistance	double	Ohm/mile	I	Resistance of the cable shielding.
rating.summer.continuous	double	A	I	The continuous rating for the conductor during summer month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.summer.emergency	double	A	I	The emergency (short time) rating for the conductor during summer month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.winter.continuous	double	A	I	The continuous rating for the conductor during winter month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality
rating.winter.emergency	double	A	I	The emergency (short time) rating for the conductor during winter month usage. This parameter is unused at this point. Future versions of GridLAB-D™ may implement this functionality

Underground Line Conductor State of Development

Underground Line Conductor is considered a highly developed and validated model.