To represent the physical grid components, and the calculation results, this library uses a graph data model. In this document, the graph data model is presented with the list of all components types, and their relevant input/output attributes.
The components types are organized in an inheritance-like hierarchy. A sub-type has all the attributes from its parent type. The hierarchy of the component types is shown below.
graph LR
base-->node
base-->branch
branch-->line
branch-->link
branch-->transformer
base-->branch3
branch3-->three_winding_transformer
base-->appliance
appliance-->generic_load_gen
generic_load_gen-->sym_load
generic_load_gen-->sym_gen
generic_load_gen-->asym_load
generic_load_gen-->asym_gen
appliance-->source
appliance-->shunt
base-->sensor
sensor-->generic_voltage_sensor
generic_voltage_sensor-->sym_voltage_sensor
generic_voltage_sensor-->asym_voltage_sensor
sensor-->generic_power_sensor
generic_power_sensor-->sym_power_sensor
generic_power_sensor-->asym_power_sensor
classDef green fill:#9f6,stroke:#333,stroke-width:2px
class node,line,link,transformer,three_winding_transformer,source,shunt,sym_load,sym_gen,asym_load,asym_gen,sym_voltage_sensor,asym_voltage_sensor,sym_power_sensor,asym_power_sensor green
The type names in the hierarchy are exactly the same as the component type names in
the {py:class}`power_grid_model.power_grid_meta_data`, see [Native Data Interface](../advanced_documentation/native-data-interface.md)
This library uses a graph data model with three generic component types: node
, branch
, branch3
and appliance
. A
node is similar to a vertex in the graph, a branch is similar to an edge in the graph and a branch3 connects three nodes
together. An appliance is a component which is connected (coupled) to a node, it is seen as a user of this node.
The figure below shows a simple example:
node_1 ---line_3 (branch)--- node_2 --------------three_winding_transformer_8 (branch3)------ node_6
| | |
source_5 (appliance) sym_load_4 (appliance) node_7
- There are four nodes (points/vertices) in the graph of this simple grid.
- The
node_1
andnode_2
are connected byline_3
which is a branch (edge). - The
node_2
,node_6
, andnode_7
are connected bythree_winding_transformer_8
which is a branch3. - There are two appliances in the grid. The
source_5
is coupled tonode_1
and thesym_load_4
is coupled tonode_2
.
It should be emphasized that the symmetry of components and calculation are two independent concepts in the model. For
example, a power grid model can consist of both sym_load
and asym_load
. They are symmetric or asymmetric load
components. On the other hand, the same model can execute symmetric or asymmetric calculations.
- In case of symmetric calculation, the
asym_load
will be treated as a symmetric load by averaging the specified power through three phases. - In case of asymmetric calculation, the
sym_load
will be treated as an asymmetric load by dividing the total specified power equally into three phases.
The sign of active/reactive power of the {ref}user_manual/components:Appliance
and
{ref}user_manual/components:Sensor
depends on the reference direction.
- For load reference direction, positive active power means the power flows from the node to the appliance/sensor.
- For generator reference direction, positive active power means the power flows from the appliance/sensor to the node .