Line

Create Function

Lines can be either created from the standard type library (create_line) or with custom values (create_line_from_parameters).

pandapower.create_line(net, from_bus, to_bus, length_km, std_type, name=None, index=None, geodata=None, df=1.0, parallel=1, in_service=True, max_loading_percent=<Mock name='mock.nan' id='140428840819960'>)

Creates a line element in net[“line”] The line parameters are defined through the standard type library.

INPUT:

net - The net within this line should be created

from_bus (int) - ID of the bus on one side which the line will be connected with

to_bus (int) - ID of the bus on the other side which the line will be connected with

length_km (float) - The line length in km

std_type (string) - The linetype of a standard line pre-defined in standard_linetypes.

OPTIONAL:

name (string) - A custom name for this line

index (int) - Force a specified ID if it is available

geodata (array, default None, shape= (,2L)) - The linegeodata of the line. The first row should be the coordinates of bus a and the last should be the coordinates of bus b. The points in the middle represent the bending points of the line

in_service (boolean) - True for in_service or False for out of service

df (float) - derating factor: maximal current of line in relation to nominal current of line (from 0 to 1)

parallel (integer) - number of parallel line systems

max_loading_percent (float) - maximum current loading (only needed for OPF)

OUTPUT:
line_id - The unique line_id of the created line
EXAMPLE:
create_line(net, “line1”, from_bus = 0, to_bus = 1, length_km=0.1, std_type=”NAYY 4x50 SE”)
pandapower.create_line_from_parameters(net, from_bus, to_bus, length_km, r_ohm_per_km, x_ohm_per_km, c_nf_per_km, max_i_ka, name=None, index=None, type=None, geodata=None, in_service=True, df=1.0, parallel=1, max_loading_percent=<Mock name='mock.nan' id='140428840819960'>, **kwargs)

Creates a line element in net[“line”] from line parameters.

INPUT:

net - The net within this line should be created

from_bus (int) - ID of the bus on one side which the line will be connected with

to_bus (int) - ID of the bus on the other side which the line will be connected with

length_km (float) - The line length in km

r_ohm_per_km (float) - line resistance in ohm per km

x_ohm_per_km (float) - line reactance in ohm per km

c_nf_per_km (float) - line capacitance in nF per km

max_i_ka (float) - maximum thermal current in kA

OPTIONAL:

name (string) - A custom name for this line

index (int) - Force a specified ID if it is available

in_service (boolean) - True for in_service or False for out of service

type (str) - type of line (“oh” for overhead line or “cs” for cable system)

df (float) - derating factor: maximal current of line in relation to nominal current of line (from 0 to 1)

parallel (integer) - number of parallel line systems

geodata (array, default None, shape= (,2L)) - The linegeodata of the line. The first row should be the coordinates of bus a and the last should be the coordinates of bus b. The points in the middle represent the bending points of the line

kwargs - nothing to see here, go along

max_loading_percent (float) - maximum current loading (only needed for OPF)

OUTPUT:
line_id - The unique line_id of the created line
EXAMPLE:
create_line_from_parameters(net, “line1”, from_bus = 0, to_bus = 1, lenght_km=0.1, r_ohm_per_km = .01, x_ohm_per_km = 0.05, c_nf_per_km = 10, max_i_ka = 0.4)

Input Parameters

net.line

Parameter Datatype Value Range Explanation
name string   name of the line
std_type string   standard type which can be used to easily define line parameters with the pandapower standard type library
from_bus* integer   Index of bus where the line starts
to_bus* integer   Index of bus where the line ends
length_km* float \(>\) 0 length of the line [km]
r_ohm_per_km* float \(\geq\) 0 resistance of the line [Ohm per km]
x_ohm_per_km* float \(\geq\) 0 inductance of the line [Ohm per km]
c_nf_per_km* float \(\geq\) 0 capacitance of the line [nF per km]
max_i_ka* float \(>\) 0 maximal thermal current [kA]
parallel* integer \(\geq\) 1 number of parallel line systems
df* float 0...1 derating factor (scaling) for max_i_ka
type string
Naming conventions:
“ol” - overhead line
“cs” - underground cable system
type of line
max_loading_percent** float \(>\) 0 Maximum loading of the line
endtemp_degree*** float \(>\) 0 Short-Circuit end temperature of the line
in_service* boolean True / False specifies if the line is in service.

*necessary for executing a power flow calculation
**optimal power flow parameter
***short-circuit calculation parameter

Note

Defining a line with length zero leads to a division by zero in the power flow and is therefore not allowed. Lines with a very low impedance might lead to convergence problems in the power flow for the same reason. If you want to directly connect two buses, please use the switch element instead of a line with a small impedance!

net.line_geodata

Parameter Datatype Explanation
coords list List of (x,y) tuples that mark the inflexion points of the line

Electric Model

Lines are modelled with the \(\pi\)-equivalent circuit:

alternate Text

The elements in the equivalent circuit are calculated from the parameters in the net.line dataframe as:

\begin{align*} \underline{Z} &= (r\_ohm\_per\_km + j \cdot x\_ohm\_per\_km) \cdot \frac{length\_km}{parallel} \\ \underline{Y}&= j \cdot 2 \pi f \cdot c\_nf\_per\_km \cdot 1 \cdot 10^-9 \cdot length\_km \cdot parallel \end{align*}

The power system frequency \(f\) is defined when creating an empty network, the default value is \(f = 50 Hz\).

The parameters are then transformed in the per unit system:

\begin{align*} Z_{N} &= \frac{V_{N}^2}{S_{N}} \\ \underline{z} &= \frac{\underline{Z}}{Z_{N}} \\ \underline{y} &= \underline{Y} \cdot Z_{N} \\ \end{align*}

Where the reference voltage \(V_{N}\) is the nominal voltage at the from bus and the rated apparent power \(S_{N}\) is defined system wide in the net object (see Unit Systems and Conventions).

Note

pandapower assumes that nominal voltage of from bus and to bus are equal, which means pandapower does not support lines that connect different voltage levels. If you want to connect different voltage levels, either use a transformer or an impedance element.

Result Parameters

net.res_line

Parameter Datatype Explanation
p_from_kw float active power flow into the line at “from” bus [kW]
q_from_kvar float reactive power flow into the line at “from” bus [kVar]
p_to_kw float active power flow into the line at “to” bus [kW]
q_to_kvar float reactive power flow into the line at “to” bus [kVar]
pl_kw float active power losses of the line [kW]
ql_kvar float reactive power consumption of the line [kVar]
i_from_ka float Current at to bus [kA]
i_to_ka float Current at from bus [kA]
i_ka float Maximum of i_from_ka and i_to_ka [kA]
loading_percent float line loading [%]

The power flow results in the net.res_line table are defined as:

\begin{align*} p\_from\_kw &= Re(\underline{v}_{from} \cdot \underline{i}^*_{from}) \\ q\_from\_kvar &= Im(\underline{v}_{from} \cdot \underline{i}^*_{from}) \\ p\_to\_kw &= Re(\underline{v}_{to} \cdot \underline{i}^*_{to}) \\ q\_to\_kvar &= Im(\underline{v}_{to} \cdot \underline{i}^*_{to}) \\ pl\_kw &= p\_from\_kw + p\_to\_kw \\ ql\_kvar &= q\_from\_kvar + q\_to\_kvar \\ i\_from\_ka &= i_{from} \\ i\_to\_ka &= i_{to} \\ i\_ka &= max(i_{from}, i_{to}) \\ loading\_percent &= \frac{i\_ka}{imax\_ka \cdot df \cdot parallel} \cdot 100 \end{align*}

net.res_line_est

The state estimation results are put into net.res_line_est with the same definition as in net.res_line.

Parameter Datatype Explanation
p_from_kw float active power flow into the line at “from” bus [kW]
q_from_kvar float reactive power flow into the line at “from” bus [kVar]
p_to_kw float active power flow into the line at “to” bus [kW]
q_to_kvar float reactive power flow into the line at “to” bus [kVar]
pl_kw float active power losses of the line [kW]
ql_kvar float reactive power consumption of the line [kVar]
i_from_ka float Current at to bus [kA]
i_to_ka float Current at from bus [kA]
i_ka float Maximum of i_from_ka and i_to_ka [kA]
loading_percent float line loading [%]