Line¶

The Line components represent power transmission and distribution lines. They connect a bus0 to a bus1. They can connect to buses with carrier "AC" or "DC". Power flow through lines is not directly controllable, but is determined passively by their impedances and the nodal power imbalances according to Kirchhoff's voltage law. To see how the impedances are used in the power flow, see the line model.

When to use Link instead?

Use the Link for power lines with controllable power flow, such as point-to-point HVDC links.
Use the Link for any connection between buses with different carrier.

attribute	type	unit	default	description	status
name	string	nan	nan	Unique name	Input (required)
bus0	string	nan	nan	Name of origin bus to which branch is attached.	Input (required)
bus1	string	nan	nan	Name of destination bus to which branch is attached.	Input (required)
type	string	nan	nan	Name of line standard type. If this is not an empty string "", the line standard type impedance parameters are multiplied with the `length` and divided/multiplied by `num_parallel` to compute `x`, `r`, etc. This will override any values set in `r`, `x, and`b`. If the string is empty, values manually provided for`r`,`x`, etc. are taken.	Input (optional)
x	float	Ohm	0	Series reactance, must be non-zero for AC branch for linearised power flow equations. If the line has series inductance \(L\) in Henries then \(x = 2\pi f L\) where \(f\) is the frequency in Hertz. Series impedance \(z = r + jx\) must be non-zero for non-linear power flow calculations. Ignored if `type` defined.	Input (required)
r	float	Ohm	0	Series resistance, must be non-zero for DC branch for linearised power flow equations. Series impedance \(z = r + jx\) must be non-zero for the non-linear power flow. Ignored if `type` defined.	Input (required)
g	float	Siemens	0	Shunt conductivity. Shunt admittance is \(y = g + jb\).	Input (optional)
b	float	Siemens	0	Shunt susceptance. If the line has shunt capacitance \(C\) in Farads then \(b = 2\pi f C\) where \(f\) is the frequency in Hertz. Shunt admittance is \(y = g + jb\). Ignored if `type` defined.	Input (optional)
s_nom	float	MVA	0	Limit of apparent power which can pass through branch in either direction. Ignored if `s_nom_extendable=True`.	Input (optional)
s_nom_mod	float	MVA	0	Modular unit size of line expansion of `s_nom` (e.g. fixed rating of added circuit). Introduces integer variables.	Input (optional)
s_nom_extendable	boolean	nan	False	Switch to allow capacity `s_nom` to be extended in optimisation.	Input (optional)
s_nom_min	float	MVA	0	If `s_nom_extendable=True`, set the minimum value of `s_nom_opt`.	Input (optional)
s_nom_max	float	MVA	inf	If `s_nom_extendable=True`, set the maximum value of `s_nom_opt`.	Input (optional)
s_nom_set	float	MVA	nan	If `s_nom` is extendable in optimization, set the value of `s_nom_opt`.	Input (optional)
s_max_pu	static or series	per unit	1	The maximum allowed absolute apparent power flow per unit of `s_nom` for the optimisation (e.g. can set `s_max_pu<1` to approximate \(N-1\) contingency factor, or can be time-varying to represent weather-dependent dynamic line rating for overhead lines).	Input (optional)
capital_cost	float	currency/MVA	0	Fixed period costs of extending `s_nom` by 1 MVA (e.g. annuitized investment costs). Used directly unless `overnight_cost` is specified. Any `length` factor must already be included.	Input (optional)
overnight_cost	float	currency/MVA	nan	Overnight (upfront) investment cost per MVA. If specified, PyPSA calculates annuity using `discount_rate` and `lifetime`. Takes precedence over `capital_cost`.	Input (optional)
discount_rate	float	per unit	nan	Discount rate for annuity calculation when using `overnight_cost`. Supports 0% rate (simple depreciation).	Input (optional)
fom_cost	float	currency/MVA	0	Fixed period operation and maintenance cost per MVA, added to annuitized investment cost.	Input (optional)
active	boolean	nan	True	Whether to consider the component in optimisation or not	Input (optional)
build_year	int	year	0	Build year of line.	Input (optional)
lifetime	float	years	inf	Lifetime of line.	Input (optional)
length	float	km	0	Length of line used when `type` is set. Also useful for calculating `capital_cost`.	Input (optional)
carrier	string	nan	nan	Type of current. "AC" is the only valid value for lines.	Input (optional)
terrain_factor	float	per unit	1	Terrain factor for increasing `length` for `capital_cost` calculation.	Input (optional)
num_parallel	float	nan	1	When `type` is set, this is the number of parallel circuits. Can also be fractional. If `type` is empty "" this value is ignored.	Input (optional)
v_ang_min	float	degrees	-inf	Minimum voltage angle difference across the line. Placeholder attribute not currently used.	Input (optional)
v_ang_max	float	degrees	inf	Maximum voltage angle difference across the line. Placeholder attribute not currently used.	Input (optional)
sub_network	string	nan	nan	Name of sub-network to which lines belongs, as calculated by `n.determine_network_topology()`. Do not set by hand.	Output
p0	series	MW	0	Active power at `bus0` (positive if branch is withdrawing power from `bus0`).	Output
q0	series	MVar	0	Reactive power at `bus0` (positive if branch is withdrawing power from `bus0`).	Output
p1	series	MW	0	Active power at `bus1` (positive if branch is withdrawing power from `bus1`).	Output
q1	series	MVar	0	Reactive power at `bus1` (positive if branch is withdrawing power from `bus1`).	Output
x_pu	float	per unit	0	Per unit series reactance calculated by `n.calculate_dependent_values()` from `x` and `n.buses.v_nom`.	Output
r_pu	float	per unit	0	Per unit series resistance calculated by `n.calculate_dependent_values()` from `r` and `n.buses.v_nom`.	Output
g_pu	float	per unit	0	Per unit shunt conductivity calculated by `n.calculate_dependent_values()` from `g` and `n.buses.v_nom`.	Output
b_pu	float	per unit	0	Per unit shunt susceptance calculated by `n.calculate_dependent_values()` from `b` and `n.buses.v_nom`.	Output
x_pu_eff	float	per unit	0	Effective per unit series reactance for linear power flow, calculated by `n.calculate_dependent_values()` from `x` and `n.buses.v_nom`	Output
r_pu_eff	float	per unit	0	Effective per unit series resistance for linear power flow, calculated by `n.calculate_dependent_values()` from `r` and `n.buses.v_nom`	Output
s_nom_opt	float	MVA	0	Optimised nominal capacity for apparent power.	Output
mu_lower	series	currency/MVA	0	Shadow price of lower `s_nom` limit \(-F \leq f\). Always non-negative.	Output
mu_upper	series	currency/MVA	0	Shadow price of upper `s_nom` limit \(f \leq F\). Always non-negative.	Output