Grid Component Modeling

Note

This document is about components not explicitly supported by PGM that can still be modeled using PGM components. For documentation on the components supported by PGM, please refer to Components.

The power grid consists of many different component types and the list is ever-increasing. As a result, it would be an impossible task to make the list of components supported by PGM exhaustive. Moreover, many grid component types share electrical attributes, so that one such grid component may be modeled as another. This document contains a non-exhaustive list of such modeling examples. New contributions and ideas for modeling grid components are very welcome!

Ideal transformer

An ideal transformer can be modeled as a link. To this end, it is explicitly allowed to place a link between two different voltage levels. Trivially, no additional electrical parameters need to be specified.

Note

The transformer component as provided by the PGM models a real transformer in the grid, i.e., with finite impedance. This directly conflicts with the properties of an ideal transformer, so the PGM transformer cannot be used to model ideal transformers.

Grounding transformer

A grounding transformer (a.k.a. earthing transformer) can be modeled as a shunt with only zero-sequence parameters (and positive-sequence parameters set to \(0\)). In particular, a grounding transformer with resistance \(r\) and reactance \(x\) can be modeled as follows.

\[\begin{split} \begin{aligned} g_1 &= 0 \\ b_1 &= 0 \\ g_0 &= \Re\left\{\frac{1}{r + j x}\right\} \\ b_0 &= \Im\left\{\frac{1}{r + j x}\right\} \end{aligned} \end{split}\]

Choke coil

A choke coil (a.k.a. reactance coil) can be modeled as a line with its shunt parameters (c1, tan1, c0, tan0) set to \(0\).

Note

A choke coil can also be modeled using a generic branch. However, at the time of writing (June 2026; see PGM issue #739), this component does not yet support zero-sequence parameters. As a result, asymmetric calculations are not supported, and this model currently only works for symmetric calculations.

Cable

A cable is equivalent to a line.