diff --git a/.gitignore b/.gitignore
index 60f82c6..7fb1547 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,7 +4,7 @@ octave-workspace
 # Local
 tests/results/*.xlsx
 tests/results/**/*.xlsx
-
+data/*.xlsx
 
 # Playground
 playground.ipynb
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 841ea7e..b6554db 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -30,7 +30,6 @@ Optionally, if you want to test matlab compatibility, you can install `matlabeng
 uv pip install matlabengine
 ```
 
-
 ## Install in development mode
 
 ```shell
diff --git a/data/case9_reduced.m b/data/case9_reduced.m
new file mode 100644
index 0000000..44bb5e1
--- /dev/null
+++ b/data/case9_reduced.m
@@ -0,0 +1,41 @@
+function mpc = case9_reduced
+%CASE9_REDUCED  6-bus reduced of power flow data from 9 bus, 3 generator case.
+%   Derived from the standard CASE9 test case data from Joe H. Chow's book, p. 70.
+%   by removing the three branch without BR_R and move the generator.
+%
+%   Original Bus 1 (Gen 1) merged into Bus 4  (slack)
+%   Original Bus 2 (Gen 2) merged into Bus 8  (PV)
+%   Original Bus 3 (Gen 3) merged into Bus 6  (PV)
+
+mpc.version = '2';
+mpc.baseMVA = 100;
+
+%% bus data
+%  bus_i  type  Pd    Qd  Gs  Bs  area  Vm        Va          baseKV  zone  Vmax  Vmin
+mpc.bus = [
+    4      3     0     0   0   0   1     1.040000  -2.216788   345     1     1.1   0.9;
+    5      1     90    30  0   0   1     1.019544  -3.599309   345     1     1.1   0.9;
+    6      2     0     0   0   0   1     1.025000   2.208471   345     1     1.1   0.9;
+    7      1     100   35  0   0   1     1.012276   0.912347   345     1     1.1   0.9;
+    8      2     0     0   0   0   1     1.025000   3.885641   345     1     1.1   0.9;
+    9      1     125   50  0   0   1     1.005122  -3.900271   345     1     1.1   0.9;
+];
+
+%% generator data
+%  bus  Pg          Qg          Qmax  Qmin   Vg     mBase  status  Pmax  Pmin
+mpc.gen = [
+    4    71.730424   38.076988   300   -300   1.040  100    1       250   10;
+    8    163.000000  -11.552844  300   -300   1.025  100    1       300   10;
+    6    85.000000   -26.910102  300   -300   1.025  100    1       270   10;
+];
+
+%% branch data
+%  fbus  tbus  r       x       b       rateA  rateB  rateC  tap  shift  status  angmin  angmax
+mpc.branch = [
+    4     5     0.0170  0.0920  0.158   250    250    250    0    0      1       -360    360;
+    5     6     0.0390  0.1700  0.358   150    150    150    0    0      1       -360    360;
+    6     7     0.0119  0.1008  0.209   150    150    150    0    0      1       -360    360;
+    7     8     0.0085  0.0720  0.149   250    250    250    0    0      1       -360    360;
+    8     9     0.0320  0.1610  0.306   250    250    250    0    0      1       -360    360;
+    9     4     0.0100  0.0850  0.176   250    250    250    0    0      1       -360    360;
+];
diff --git a/matpowercaseframes/core.py b/matpowercaseframes/core.py
index 336629c..edf4c9f 100644
--- a/matpowercaseframes/core.py
+++ b/matpowercaseframes/core.py
@@ -1023,15 +1023,48 @@ def _get_dataframe(self, attribute, data, n_cols=None, columns_template=None):
 
     def _update_index(self, allow_any_keys=False):
         """
-        Update the index of the bus, branch, and generator tables based on naming.
+        Update the index of the bus, branch, generator, etc tables based on naming.
 
+        For buses, prefer:
+        1) bus_name (if available)
+        2) BUS_I column (if available)
+        3) a 1-based RangeIndex fallback
 
         Args:
             allow_any_keys (bool):
                 Whether to update index for any keys beyond standard attributes.
         """
+
         for attribute, attribute_name in zip(["bus", "branch", "gen"], ATTRIBUTES_NAME):
             attribute_data = getattr(self, attribute)
+
+            if attribute == "bus":
+                try:
+                    attribute_name_data = getattr(self, attribute_name)  # bus_name
+                    attribute_data.set_index(
+                        attribute_name_data, drop=False, inplace=True
+                    )
+                    continue
+                except AttributeError:
+                    pass
+
+                if (
+                    isinstance(attribute_data, pd.DataFrame)
+                    and "BUS_I" in attribute_data.columns
+                ):
+                    attribute_data.set_index(
+                        attribute_data["BUS_I"].astype(int), drop=False, inplace=True
+                    )
+                    attribute_data.index.name = "bus"
+                    continue
+
+                attribute_data.set_index(
+                    pd.RangeIndex(1, len(attribute_data.index) + 1, name="bus"),
+                    drop=False,
+                    inplace=True,
+                )
+                continue
+
             try:
                 attribute_name_data = getattr(self, attribute_name)
                 attribute_data.set_index(attribute_name_data, drop=False, inplace=True)
diff --git a/notebooks/from_extract_islands.ipynb b/notebooks/from_extract_islands.ipynb
new file mode 100644
index 0000000..6750cff
--- /dev/null
+++ b/notebooks/from_extract_islands.ipynb
@@ -0,0 +1,1600 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "63b62eba",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%load_ext autoreload\n",
+    "%autoreload 2"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "bc1b26ff",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import os\n",
+    "\n",
+    "from matpower import path_matpower, start_instance\n",
+    "\n",
+    "from matpowercaseframes import CaseFrames"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "277fe1e3",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "path = os.path.join(path_matpower, \"data/case9.m\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2ac3ec42",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "m = start_instance()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "a6c06b62",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>F_BUS</th>\n",
+       "      <th>T_BUS</th>\n",
+       "      <th>BR_R</th>\n",
+       "      <th>BR_X</th>\n",
+       "      <th>BR_B</th>\n",
+       "      <th>RATE_A</th>\n",
+       "      <th>RATE_B</th>\n",
+       "      <th>RATE_C</th>\n",
+       "      <th>TAP</th>\n",
+       "      <th>SHIFT</th>\n",
+       "      <th>BR_STATUS</th>\n",
+       "      <th>ANGMIN</th>\n",
+       "      <th>ANGMAX</th>\n",
+       "      <th>PF</th>\n",
+       "      <th>QF</th>\n",
+       "      <th>PT</th>\n",
+       "      <th>QT</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>branch</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>1</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0576</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>71.641021</td>\n",
+       "      <td>27.045924</td>\n",
+       "      <td>-71.641021</td>\n",
+       "      <td>-23.923127</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>4</td>\n",
+       "      <td>5</td>\n",
+       "      <td>0.0170</td>\n",
+       "      <td>0.0920</td>\n",
+       "      <td>0.158</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>30.703670</td>\n",
+       "      <td>1.030006</td>\n",
+       "      <td>-30.537263</td>\n",
+       "      <td>-16.543365</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>5</td>\n",
+       "      <td>6</td>\n",
+       "      <td>0.0390</td>\n",
+       "      <td>0.1700</td>\n",
+       "      <td>0.358</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-59.462737</td>\n",
+       "      <td>-13.456635</td>\n",
+       "      <td>60.816586</td>\n",
+       "      <td>-18.074836</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>3</td>\n",
+       "      <td>6</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0586</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>300</td>\n",
+       "      <td>300</td>\n",
+       "      <td>300</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>85.000000</td>\n",
+       "      <td>-10.859709</td>\n",
+       "      <td>-85.000000</td>\n",
+       "      <td>14.955327</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>5</th>\n",
+       "      <td>6</td>\n",
+       "      <td>7</td>\n",
+       "      <td>0.0119</td>\n",
+       "      <td>0.1008</td>\n",
+       "      <td>0.209</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>24.183414</td>\n",
+       "      <td>3.119508</td>\n",
+       "      <td>-24.095417</td>\n",
+       "      <td>-24.295823</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6</th>\n",
+       "      <td>7</td>\n",
+       "      <td>8</td>\n",
+       "      <td>0.0085</td>\n",
+       "      <td>0.0720</td>\n",
+       "      <td>0.149</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-75.904583</td>\n",
+       "      <td>-10.704177</td>\n",
+       "      <td>76.379866</td>\n",
+       "      <td>-0.797331</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7</th>\n",
+       "      <td>8</td>\n",
+       "      <td>2</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0625</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-163.000000</td>\n",
+       "      <td>9.178149</td>\n",
+       "      <td>163.000000</td>\n",
+       "      <td>6.653660</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>8</th>\n",
+       "      <td>8</td>\n",
+       "      <td>9</td>\n",
+       "      <td>0.0320</td>\n",
+       "      <td>0.1610</td>\n",
+       "      <td>0.306</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>86.620134</td>\n",
+       "      <td>-8.380817</td>\n",
+       "      <td>-84.320163</td>\n",
+       "      <td>-11.312751</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>9</th>\n",
+       "      <td>9</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.0100</td>\n",
+       "      <td>0.0850</td>\n",
+       "      <td>0.176</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-40.679837</td>\n",
+       "      <td>-38.687249</td>\n",
+       "      <td>40.937352</td>\n",
+       "      <td>22.893121</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "        F_BUS  T_BUS    BR_R    BR_X   BR_B  RATE_A  RATE_B  RATE_C  TAP  \\\n",
+       "branch                                                                     \n",
+       "1           1      4  0.0000  0.0576  0.000     250     250     250    0   \n",
+       "2           4      5  0.0170  0.0920  0.158     250     250     250    0   \n",
+       "3           5      6  0.0390  0.1700  0.358     150     150     150    0   \n",
+       "4           3      6  0.0000  0.0586  0.000     300     300     300    0   \n",
+       "5           6      7  0.0119  0.1008  0.209     150     150     150    0   \n",
+       "6           7      8  0.0085  0.0720  0.149     250     250     250    0   \n",
+       "7           8      2  0.0000  0.0625  0.000     250     250     250    0   \n",
+       "8           8      9  0.0320  0.1610  0.306     250     250     250    0   \n",
+       "9           9      4  0.0100  0.0850  0.176     250     250     250    0   \n",
+       "\n",
+       "        SHIFT  BR_STATUS  ANGMIN  ANGMAX          PF         QF          PT  \\\n",
+       "branch                                                                        \n",
+       "1           0          1    -360     360   71.641021  27.045924  -71.641021   \n",
+       "2           0          1    -360     360   30.703670   1.030006  -30.537263   \n",
+       "3           0          1    -360     360  -59.462737 -13.456635   60.816586   \n",
+       "4           0          1    -360     360   85.000000 -10.859709  -85.000000   \n",
+       "5           0          1    -360     360   24.183414   3.119508  -24.095417   \n",
+       "6           0          1    -360     360  -75.904583 -10.704177   76.379866   \n",
+       "7           0          1    -360     360 -163.000000   9.178149  163.000000   \n",
+       "8           0          1    -360     360   86.620134  -8.380817  -84.320163   \n",
+       "9           0          1    -360     360  -40.679837 -38.687249   40.937352   \n",
+       "\n",
+       "               QT  \n",
+       "branch             \n",
+       "1      -23.923127  \n",
+       "2      -16.543365  \n",
+       "3      -18.074836  \n",
+       "4       14.955327  \n",
+       "5      -24.295823  \n",
+       "6       -0.797331  \n",
+       "7        6.653660  \n",
+       "8      -11.312751  \n",
+       "9       22.893121  "
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "cf = CaseFrames(path, load_case_engine=m)\n",
+    "\n",
+    "mpc = m.runpf(cf.to_mpc(), verbose=False)\n",
+    "cf = CaseFrames(mpc)\n",
+    "cf.infer_numpy()\n",
+    "cf.branch"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "fa4362cd",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>F_BUS</th>\n",
+       "      <th>T_BUS</th>\n",
+       "      <th>BR_R</th>\n",
+       "      <th>BR_X</th>\n",
+       "      <th>BR_B</th>\n",
+       "      <th>RATE_A</th>\n",
+       "      <th>RATE_B</th>\n",
+       "      <th>RATE_C</th>\n",
+       "      <th>TAP</th>\n",
+       "      <th>SHIFT</th>\n",
+       "      <th>BR_STATUS</th>\n",
+       "      <th>ANGMIN</th>\n",
+       "      <th>ANGMAX</th>\n",
+       "      <th>PF</th>\n",
+       "      <th>QF</th>\n",
+       "      <th>PT</th>\n",
+       "      <th>QT</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>branch</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>1</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0576</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>71.641021</td>\n",
+       "      <td>27.045924</td>\n",
+       "      <td>-71.641021</td>\n",
+       "      <td>-23.923127</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>4</td>\n",
+       "      <td>5</td>\n",
+       "      <td>0.0170</td>\n",
+       "      <td>0.0920</td>\n",
+       "      <td>0.158</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>30.703670</td>\n",
+       "      <td>1.030006</td>\n",
+       "      <td>-30.537263</td>\n",
+       "      <td>-16.543365</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>5</td>\n",
+       "      <td>6</td>\n",
+       "      <td>0.0390</td>\n",
+       "      <td>0.1700</td>\n",
+       "      <td>0.358</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-59.462737</td>\n",
+       "      <td>-13.456635</td>\n",
+       "      <td>60.816586</td>\n",
+       "      <td>-18.074836</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>3</td>\n",
+       "      <td>6</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0586</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>300</td>\n",
+       "      <td>300</td>\n",
+       "      <td>300</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>85.000000</td>\n",
+       "      <td>-10.859709</td>\n",
+       "      <td>-85.000000</td>\n",
+       "      <td>14.955327</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>5</th>\n",
+       "      <td>6</td>\n",
+       "      <td>7</td>\n",
+       "      <td>0.0119</td>\n",
+       "      <td>0.1008</td>\n",
+       "      <td>0.209</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>24.183414</td>\n",
+       "      <td>3.119508</td>\n",
+       "      <td>-24.095417</td>\n",
+       "      <td>-24.295823</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6</th>\n",
+       "      <td>7</td>\n",
+       "      <td>8</td>\n",
+       "      <td>0.0085</td>\n",
+       "      <td>0.0720</td>\n",
+       "      <td>0.149</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-75.904583</td>\n",
+       "      <td>-10.704177</td>\n",
+       "      <td>76.379866</td>\n",
+       "      <td>-0.797331</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7</th>\n",
+       "      <td>8</td>\n",
+       "      <td>2</td>\n",
+       "      <td>0.0000</td>\n",
+       "      <td>0.0625</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-163.000000</td>\n",
+       "      <td>9.178149</td>\n",
+       "      <td>163.000000</td>\n",
+       "      <td>6.653660</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>8</th>\n",
+       "      <td>8</td>\n",
+       "      <td>9</td>\n",
+       "      <td>0.0320</td>\n",
+       "      <td>0.1610</td>\n",
+       "      <td>0.306</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>86.620134</td>\n",
+       "      <td>-8.380817</td>\n",
+       "      <td>-84.320163</td>\n",
+       "      <td>-11.312751</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>9</th>\n",
+       "      <td>9</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.0100</td>\n",
+       "      <td>0.0850</td>\n",
+       "      <td>0.176</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-40.679837</td>\n",
+       "      <td>-38.687249</td>\n",
+       "      <td>40.937352</td>\n",
+       "      <td>22.893121</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "        F_BUS  T_BUS    BR_R    BR_X   BR_B  RATE_A  RATE_B  RATE_C  TAP  \\\n",
+       "branch                                                                     \n",
+       "1           1      4  0.0000  0.0576  0.000     250     250     250    0   \n",
+       "2           4      5  0.0170  0.0920  0.158     250     250     250    0   \n",
+       "3           5      6  0.0390  0.1700  0.358     150     150     150    0   \n",
+       "4           3      6  0.0000  0.0586  0.000     300     300     300    0   \n",
+       "5           6      7  0.0119  0.1008  0.209     150     150     150    0   \n",
+       "6           7      8  0.0085  0.0720  0.149     250     250     250    0   \n",
+       "7           8      2  0.0000  0.0625  0.000     250     250     250    0   \n",
+       "8           8      9  0.0320  0.1610  0.306     250     250     250    0   \n",
+       "9           9      4  0.0100  0.0850  0.176     250     250     250    0   \n",
+       "\n",
+       "        SHIFT  BR_STATUS  ANGMIN  ANGMAX          PF         QF          PT  \\\n",
+       "branch                                                                        \n",
+       "1           0          1    -360     360   71.641021  27.045924  -71.641021   \n",
+       "2           0          1    -360     360   30.703670   1.030006  -30.537263   \n",
+       "3           0          0    -360     360  -59.462737 -13.456635   60.816586   \n",
+       "4           0          1    -360     360   85.000000 -10.859709  -85.000000   \n",
+       "5           0          1    -360     360   24.183414   3.119508  -24.095417   \n",
+       "6           0          1    -360     360  -75.904583 -10.704177   76.379866   \n",
+       "7           0          1    -360     360 -163.000000   9.178149  163.000000   \n",
+       "8           0          0    -360     360   86.620134  -8.380817  -84.320163   \n",
+       "9           0          1    -360     360  -40.679837 -38.687249   40.937352   \n",
+       "\n",
+       "               QT  \n",
+       "branch             \n",
+       "1      -23.923127  \n",
+       "2      -16.543365  \n",
+       "3      -18.074836  \n",
+       "4       14.955327  \n",
+       "5      -24.295823  \n",
+       "6       -0.797331  \n",
+       "7        6.653660  \n",
+       "8      -11.312751  \n",
+       "9       22.893121  "
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "cf.branch.loc[[3, 8], \"BR_STATUS\"] = 0\n",
+    "cf.branch"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "b1cb7954",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "(Cell([[array([[2., 3., 6., 7., 8.]]), array([[1., 4., 5., 9.]])]],\n",
+       "       dtype=object),\n",
+       " array([], shape=(1, 0), dtype=float64))"
+      ]
+     },
+     "execution_count": null,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "[groups, isolated] = m.find_islands(cf.to_mpc(), nout=2)\n",
+    "groups, isolated"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "6fad4a6a",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
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+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>F_BUS</th>\n",
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+       "      <th>BR_R</th>\n",
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+       "      <th>RATE_C</th>\n",
+       "      <th>TAP</th>\n",
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+       "      <th>BR_STATUS</th>\n",
+       "      <th>ANGMIN</th>\n",
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+       "    <tr>\n",
+       "      <th>branch</th>\n",
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+       "      <th>1</th>\n",
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+       "      <td>0.0586</td>\n",
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+       "      <td>-85.000000</td>\n",
+       "      <td>14.955327</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>6</td>\n",
+       "      <td>7</td>\n",
+       "      <td>0.0119</td>\n",
+       "      <td>0.1008</td>\n",
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+       "      <td>-24.295823</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>7</td>\n",
+       "      <td>8</td>\n",
+       "      <td>0.0085</td>\n",
+       "      <td>0.0720</td>\n",
+       "      <td>0.149</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-75.904583</td>\n",
+       "      <td>-10.704177</td>\n",
+       "      <td>76.379866</td>\n",
+       "      <td>-0.797331</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>8</td>\n",
+       "      <td>2</td>\n",
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+       "      <td>0.0625</td>\n",
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+       "      <td>163.000000</td>\n",
+       "      <td>6.653660</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "        F_BUS  T_BUS    BR_R    BR_X   BR_B  RATE_A  RATE_B  RATE_C  TAP  \\\n",
+       "branch                                                                     \n",
+       "1           3      6  0.0000  0.0586  0.000     300     300     300    0   \n",
+       "2           6      7  0.0119  0.1008  0.209     150     150     150    0   \n",
+       "3           7      8  0.0085  0.0720  0.149     250     250     250    0   \n",
+       "4           8      2  0.0000  0.0625  0.000     250     250     250    0   \n",
+       "\n",
+       "        SHIFT  BR_STATUS  ANGMIN  ANGMAX          PF         QF          PT  \\\n",
+       "branch                                                                        \n",
+       "1           0          1    -360     360   85.000000 -10.859709  -85.000000   \n",
+       "2           0          1    -360     360   24.183414   3.119508  -24.095417   \n",
+       "3           0          1    -360     360  -75.904583 -10.704177   76.379866   \n",
+       "4           0          1    -360     360 -163.000000   9.178149  163.000000   \n",
+       "\n",
+       "               QT  \n",
+       "branch             \n",
+       "1       14.955327  \n",
+       "2      -24.295823  \n",
+       "3       -0.797331  \n",
+       "4        6.653660  "
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+    },
+    {
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+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>BUS_I</th>\n",
+       "      <th>BUS_TYPE</th>\n",
+       "      <th>PD</th>\n",
+       "      <th>QD</th>\n",
+       "      <th>GS</th>\n",
+       "      <th>BS</th>\n",
+       "      <th>BUS_AREA</th>\n",
+       "      <th>VM</th>\n",
+       "      <th>VA</th>\n",
+       "      <th>BASE_KV</th>\n",
+       "      <th>ZONE</th>\n",
+       "      <th>VMAX</th>\n",
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+       "    <tr>\n",
+       "      <th>bus</th>\n",
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+       "      <th></th>\n",
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+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>2</td>\n",
+       "      <td>2</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
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+       "      <td>9.280005</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
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+       "    <tr>\n",
+       "      <th>3</th>\n",
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+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
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+       "    <tr>\n",
+       "      <th>6</th>\n",
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+       "      <td>1</td>\n",
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+       "      <td>1</td>\n",
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+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7</th>\n",
+       "      <td>7</td>\n",
+       "      <td>1</td>\n",
+       "      <td>100</td>\n",
+       "      <td>35</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.015883</td>\n",
+       "      <td>0.727536</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>8</th>\n",
+       "      <td>8</td>\n",
+       "      <td>1</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.025769</td>\n",
+       "      <td>3.719701</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     BUS_I  BUS_TYPE   PD  QD  GS  BS  BUS_AREA        VM        VA  BASE_KV  \\\n",
+       "bus                                                                            \n",
+       "2        2         2    0   0   0   0         1  1.025000  9.280005      345   \n",
+       "3        3         2    0   0   0   0         1  1.025000  4.664751      345   \n",
+       "6        6         1    0   0   0   0         1  1.032353  1.966716      345   \n",
+       "7        7         1  100  35   0   0         1  1.015883  0.727536      345   \n",
+       "8        8         1    0   0   0   0         1  1.025769  3.719701      345   \n",
+       "\n",
+       "     ZONE  VMAX  VMIN  \n",
+       "bus                    \n",
+       "2       1   1.1   0.9  \n",
+       "3       1   1.1   0.9  \n",
+       "6       1   1.1   0.9  \n",
+       "7       1   1.1   0.9  \n",
+       "8       1   1.1   0.9  "
+      ]
+     },
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+       "      <th>RAMP_Q</th>\n",
+       "      <th>APF</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>gen</th>\n",
+       "      <th></th>\n",
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+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
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+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>2</td>\n",
+       "      <td>163</td>\n",
+       "      <td>6.653660</td>\n",
+       "      <td>300</td>\n",
+       "      <td>-300</td>\n",
+       "      <td>1.025</td>\n",
+       "      <td>100</td>\n",
+       "      <td>1</td>\n",
+       "      <td>300</td>\n",
+       "      <td>10</td>\n",
+       "      <td>...</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>3</td>\n",
+       "      <td>85</td>\n",
+       "      <td>-10.859709</td>\n",
+       "      <td>300</td>\n",
+       "      <td>-300</td>\n",
+       "      <td>1.025</td>\n",
+       "      <td>100</td>\n",
+       "      <td>1</td>\n",
+       "      <td>270</td>\n",
+       "      <td>10</td>\n",
+       "      <td>...</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "<p>2 rows × 21 columns</p>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     GEN_BUS   PG         QG  QMAX  QMIN     VG  MBASE  GEN_STATUS  PMAX  \\\n",
+       "gen                                                                        \n",
+       "1          2  163   6.653660   300  -300  1.025    100           1   300   \n",
+       "2          3   85 -10.859709   300  -300  1.025    100           1   270   \n",
+       "\n",
+       "     PMIN  ...  PC2  QC1MIN  QC1MAX  QC2MIN  QC2MAX  RAMP_AGC  RAMP_10  \\\n",
+       "gen        ...                                                           \n",
+       "1      10  ...    0       0       0       0       0         0        0   \n",
+       "2      10  ...    0       0       0       0       0         0        0   \n",
+       "\n",
+       "     RAMP_30  RAMP_Q  APF  \n",
+       "gen                        \n",
+       "1          0       0    0  \n",
+       "2          0       0    0  \n",
+       "\n",
+       "[2 rows x 21 columns]"
+      ]
+     },
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+       "      <th></th>\n",
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+       "      <th>BR_R</th>\n",
+       "      <th>BR_X</th>\n",
+       "      <th>BR_B</th>\n",
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+       "      <th>RATE_B</th>\n",
+       "      <th>RATE_C</th>\n",
+       "      <th>TAP</th>\n",
+       "      <th>SHIFT</th>\n",
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+       "      <th>ANGMIN</th>\n",
+       "      <th>ANGMAX</th>\n",
+       "      <th>PF</th>\n",
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+       "      <th>PT</th>\n",
+       "      <th>QT</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>branch</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
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+       "      <th></th>\n",
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+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>1</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.000</td>\n",
+       "      <td>0.0576</td>\n",
+       "      <td>0.000</td>\n",
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+       "      <td>250</td>\n",
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+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>71.641021</td>\n",
+       "      <td>27.045924</td>\n",
+       "      <td>-71.641021</td>\n",
+       "      <td>-23.923127</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>4</td>\n",
+       "      <td>5</td>\n",
+       "      <td>0.017</td>\n",
+       "      <td>0.0920</td>\n",
+       "      <td>0.158</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>30.703670</td>\n",
+       "      <td>1.030006</td>\n",
+       "      <td>-30.537263</td>\n",
+       "      <td>-16.543365</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>9</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.010</td>\n",
+       "      <td>0.0850</td>\n",
+       "      <td>0.176</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "      <td>-40.679837</td>\n",
+       "      <td>-38.687249</td>\n",
+       "      <td>40.937352</td>\n",
+       "      <td>22.893121</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "        F_BUS  T_BUS   BR_R    BR_X   BR_B  RATE_A  RATE_B  RATE_C  TAP  \\\n",
+       "branch                                                                    \n",
+       "1           1      4  0.000  0.0576  0.000     250     250     250    0   \n",
+       "2           4      5  0.017  0.0920  0.158     250     250     250    0   \n",
+       "3           9      4  0.010  0.0850  0.176     250     250     250    0   \n",
+       "\n",
+       "        SHIFT  BR_STATUS  ANGMIN  ANGMAX         PF         QF         PT  \\\n",
+       "branch                                                                      \n",
+       "1           0          1    -360     360  71.641021  27.045924 -71.641021   \n",
+       "2           0          1    -360     360  30.703670   1.030006 -30.537263   \n",
+       "3           0          1    -360     360 -40.679837 -38.687249  40.937352   \n",
+       "\n",
+       "               QT  \n",
+       "branch             \n",
+       "1      -23.923127  \n",
+       "2      -16.543365  \n",
+       "3       22.893121  "
+      ]
+     },
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+    {
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+       "  <thead>\n",
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+       "      <th></th>\n",
+       "      <th>BUS_I</th>\n",
+       "      <th>BUS_TYPE</th>\n",
+       "      <th>PD</th>\n",
+       "      <th>QD</th>\n",
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+       "      <th>ZONE</th>\n",
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+       "    <tr>\n",
+       "      <th>bus</th>\n",
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+       "      <th></th>\n",
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+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
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+       "      <th>1</th>\n",
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+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
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+       "      <td>0.000000</td>\n",
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+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
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+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>4</td>\n",
+       "      <td>1</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.025788</td>\n",
+       "      <td>-2.216788</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>5</th>\n",
+       "      <td>5</td>\n",
+       "      <td>1</td>\n",
+       "      <td>90</td>\n",
+       "      <td>30</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.012654</td>\n",
+       "      <td>-3.687396</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>9</th>\n",
+       "      <td>9</td>\n",
+       "      <td>1</td>\n",
+       "      <td>125</td>\n",
+       "      <td>50</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>0.995631</td>\n",
+       "      <td>-3.988805</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     BUS_I  BUS_TYPE   PD  QD  GS  BS  BUS_AREA        VM        VA  BASE_KV  \\\n",
+       "bus                                                                            \n",
+       "1        1         3    0   0   0   0         1  1.040000  0.000000      345   \n",
+       "4        4         1    0   0   0   0         1  1.025788 -2.216788      345   \n",
+       "5        5         1   90  30   0   0         1  1.012654 -3.687396      345   \n",
+       "9        9         1  125  50   0   0         1  0.995631 -3.988805      345   \n",
+       "\n",
+       "     ZONE  VMAX  VMIN  \n",
+       "bus                    \n",
+       "1       1   1.1   0.9  \n",
+       "4       1   1.1   0.9  \n",
+       "5       1   1.1   0.9  \n",
+       "9       1   1.1   0.9  "
+      ]
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+       "      <th>QG</th>\n",
+       "      <th>QMAX</th>\n",
+       "      <th>QMIN</th>\n",
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+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>gen</th>\n",
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+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>1</td>\n",
+       "      <td>71.641021</td>\n",
+       "      <td>27.045924</td>\n",
+       "      <td>300</td>\n",
+       "      <td>-300</td>\n",
+       "      <td>1.04</td>\n",
+       "      <td>100</td>\n",
+       "      <td>1</td>\n",
+       "      <td>250</td>\n",
+       "      <td>10</td>\n",
+       "      <td>...</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "<p>1 rows × 21 columns</p>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     GEN_BUS         PG         QG  QMAX  QMIN    VG  MBASE  GEN_STATUS  PMAX  \\\n",
+       "gen                                                                             \n",
+       "1          1  71.641021  27.045924   300  -300  1.04    100           1   250   \n",
+       "\n",
+       "     PMIN  ...  PC2  QC1MIN  QC1MAX  QC2MIN  QC2MAX  RAMP_AGC  RAMP_10  \\\n",
+       "gen        ...                                                           \n",
+       "1      10  ...    0       0       0       0       0         0        0   \n",
+       "\n",
+       "     RAMP_30  RAMP_Q  APF  \n",
+       "gen                        \n",
+       "1          0       0    0  \n",
+       "\n",
+       "[1 rows x 21 columns]"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "mpcs = m.extract_islands(cf.to_mpc(), groups)\n",
+    "\n",
+    "cfs = {}\n",
+    "for isl, mpc in enumerate(mpcs.flatten()):\n",
+    "    cfs[isl] = CaseFrames(mpc)\n",
+    "    cfs[isl].infer_numpy()\n",
+    "    display(cfs[isl].branch)\n",
+    "    display(cfs[isl].bus)\n",
+    "    display(cfs[isl].gen)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "3d46a433",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "env",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}
diff --git a/notebooks/load_case9_reduced.ipynb b/notebooks/load_case9_reduced.ipynb
new file mode 100644
index 0000000..ac8c319
--- /dev/null
+++ b/notebooks/load_case9_reduced.ipynb
@@ -0,0 +1,538 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "2b722971",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%load_ext autoreload\n",
+    "%autoreload 2"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "5bc6d51a",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "from matpowercaseframes import CaseFrames"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "9a804fba",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
+       "        vertical-align: middle;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe tbody tr th {\n",
+       "        vertical-align: top;\n",
+       "    }\n",
+       "\n",
+       "    .dataframe thead th {\n",
+       "        text-align: right;\n",
+       "    }\n",
+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>F_BUS</th>\n",
+       "      <th>T_BUS</th>\n",
+       "      <th>BR_R</th>\n",
+       "      <th>BR_X</th>\n",
+       "      <th>BR_B</th>\n",
+       "      <th>RATE_A</th>\n",
+       "      <th>RATE_B</th>\n",
+       "      <th>RATE_C</th>\n",
+       "      <th>TAP</th>\n",
+       "      <th>SHIFT</th>\n",
+       "      <th>BR_STATUS</th>\n",
+       "      <th>ANGMIN</th>\n",
+       "      <th>ANGMAX</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>branch</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
+       "      <td>4</td>\n",
+       "      <td>5</td>\n",
+       "      <td>0.0170</td>\n",
+       "      <td>0.0920</td>\n",
+       "      <td>0.158</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>5</td>\n",
+       "      <td>6</td>\n",
+       "      <td>0.0390</td>\n",
+       "      <td>0.1700</td>\n",
+       "      <td>0.358</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>6</td>\n",
+       "      <td>7</td>\n",
+       "      <td>0.0119</td>\n",
+       "      <td>0.1008</td>\n",
+       "      <td>0.209</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>150</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>7</td>\n",
+       "      <td>8</td>\n",
+       "      <td>0.0085</td>\n",
+       "      <td>0.0720</td>\n",
+       "      <td>0.149</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>5</th>\n",
+       "      <td>8</td>\n",
+       "      <td>9</td>\n",
+       "      <td>0.0320</td>\n",
+       "      <td>0.1610</td>\n",
+       "      <td>0.306</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6</th>\n",
+       "      <td>9</td>\n",
+       "      <td>4</td>\n",
+       "      <td>0.0100</td>\n",
+       "      <td>0.0850</td>\n",
+       "      <td>0.176</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>250</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>-360</td>\n",
+       "      <td>360</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "        F_BUS  T_BUS    BR_R    BR_X   BR_B  RATE_A  RATE_B  RATE_C  TAP  \\\n",
+       "branch                                                                     \n",
+       "1           4      5  0.0170  0.0920  0.158     250     250     250    0   \n",
+       "2           5      6  0.0390  0.1700  0.358     150     150     150    0   \n",
+       "3           6      7  0.0119  0.1008  0.209     150     150     150    0   \n",
+       "4           7      8  0.0085  0.0720  0.149     250     250     250    0   \n",
+       "5           8      9  0.0320  0.1610  0.306     250     250     250    0   \n",
+       "6           9      4  0.0100  0.0850  0.176     250     250     250    0   \n",
+       "\n",
+       "        SHIFT  BR_STATUS  ANGMIN  ANGMAX  \n",
+       "branch                                    \n",
+       "1           0          1    -360     360  \n",
+       "2           0          1    -360     360  \n",
+       "3           0          1    -360     360  \n",
+       "4           0          1    -360     360  \n",
+       "5           0          1    -360     360  \n",
+       "6           0          1    -360     360  "
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<div>\n",
+       "<style scoped>\n",
+       "    .dataframe tbody tr th:only-of-type {\n",
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+       "\n",
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+       "</style>\n",
+       "<table border=\"1\" class=\"dataframe\">\n",
+       "  <thead>\n",
+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>BUS_I</th>\n",
+       "      <th>BUS_TYPE</th>\n",
+       "      <th>PD</th>\n",
+       "      <th>QD</th>\n",
+       "      <th>GS</th>\n",
+       "      <th>BS</th>\n",
+       "      <th>BUS_AREA</th>\n",
+       "      <th>VM</th>\n",
+       "      <th>VA</th>\n",
+       "      <th>BASE_KV</th>\n",
+       "      <th>ZONE</th>\n",
+       "      <th>VMAX</th>\n",
+       "      <th>VMIN</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>bus</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "    </tr>\n",
+       "  </thead>\n",
+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>4</th>\n",
+       "      <td>4</td>\n",
+       "      <td>3</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.040000</td>\n",
+       "      <td>-2.216788</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>5</th>\n",
+       "      <td>5</td>\n",
+       "      <td>1</td>\n",
+       "      <td>90</td>\n",
+       "      <td>30</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.019544</td>\n",
+       "      <td>-3.599309</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>6</th>\n",
+       "      <td>6</td>\n",
+       "      <td>2</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
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+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>7</th>\n",
+       "      <td>7</td>\n",
+       "      <td>1</td>\n",
+       "      <td>100</td>\n",
+       "      <td>35</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.012276</td>\n",
+       "      <td>0.912347</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>8</th>\n",
+       "      <td>8</td>\n",
+       "      <td>2</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.025000</td>\n",
+       "      <td>3.885641</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>9</th>\n",
+       "      <td>9</td>\n",
+       "      <td>1</td>\n",
+       "      <td>125</td>\n",
+       "      <td>50</td>\n",
+       "      <td>0</td>\n",
+       "      <td>0</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.005122</td>\n",
+       "      <td>-3.900271</td>\n",
+       "      <td>345</td>\n",
+       "      <td>1</td>\n",
+       "      <td>1.1</td>\n",
+       "      <td>0.9</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     BUS_I  BUS_TYPE   PD  QD  GS  BS  BUS_AREA        VM        VA  BASE_KV  \\\n",
+       "bus                                                                            \n",
+       "4        4         3    0   0   0   0         1  1.040000 -2.216788      345   \n",
+       "5        5         1   90  30   0   0         1  1.019544 -3.599309      345   \n",
+       "6        6         2    0   0   0   0         1  1.025000  2.208471      345   \n",
+       "7        7         1  100  35   0   0         1  1.012276  0.912347      345   \n",
+       "8        8         2    0   0   0   0         1  1.025000  3.885641      345   \n",
+       "9        9         1  125  50   0   0         1  1.005122 -3.900271      345   \n",
+       "\n",
+       "     ZONE  VMAX  VMIN  \n",
+       "bus                    \n",
+       "4       1   1.1   0.9  \n",
+       "5       1   1.1   0.9  \n",
+       "6       1   1.1   0.9  \n",
+       "7       1   1.1   0.9  \n",
+       "8       1   1.1   0.9  \n",
+       "9       1   1.1   0.9  "
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    },
+    {
+     "data": {
+      "text/html": [
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+       "    <tr style=\"text-align: right;\">\n",
+       "      <th></th>\n",
+       "      <th>GEN_BUS</th>\n",
+       "      <th>PG</th>\n",
+       "      <th>QG</th>\n",
+       "      <th>QMAX</th>\n",
+       "      <th>QMIN</th>\n",
+       "      <th>VG</th>\n",
+       "      <th>MBASE</th>\n",
+       "      <th>GEN_STATUS</th>\n",
+       "      <th>PMAX</th>\n",
+       "      <th>PMIN</th>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>gen</th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
+       "      <th></th>\n",
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+       "  <tbody>\n",
+       "    <tr>\n",
+       "      <th>1</th>\n",
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+       "      <td>250</td>\n",
+       "      <td>10</td>\n",
+       "    </tr>\n",
+       "    <tr>\n",
+       "      <th>2</th>\n",
+       "      <td>8</td>\n",
+       "      <td>163.000000</td>\n",
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+       "      <td>300</td>\n",
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+       "      <td>300</td>\n",
+       "      <td>10</td>\n",
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+       "    <tr>\n",
+       "      <th>3</th>\n",
+       "      <td>6</td>\n",
+       "      <td>85.000000</td>\n",
+       "      <td>-26.910102</td>\n",
+       "      <td>300</td>\n",
+       "      <td>-300</td>\n",
+       "      <td>1.025</td>\n",
+       "      <td>100</td>\n",
+       "      <td>1</td>\n",
+       "      <td>270</td>\n",
+       "      <td>10</td>\n",
+       "    </tr>\n",
+       "  </tbody>\n",
+       "</table>\n",
+       "</div>"
+      ],
+      "text/plain": [
+       "     GEN_BUS          PG         QG  QMAX  QMIN     VG  MBASE  GEN_STATUS  \\\n",
+       "gen                                                                         \n",
+       "1          4   71.730424  38.076988   300  -300  1.040    100           1   \n",
+       "2          8  163.000000 -11.552844   300  -300  1.025    100           1   \n",
+       "3          6   85.000000 -26.910102   300  -300  1.025    100           1   \n",
+       "\n",
+       "     PMAX  PMIN  \n",
+       "gen              \n",
+       "1     250    10  \n",
+       "2     300    10  \n",
+       "3     270    10  "
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "CASE_NAME = \"../data/case9_reduced.m\"\n",
+    "cf = CaseFrames(CASE_NAME)\n",
+    "cf.infer_numpy()\n",
+    "display(cf.branch)\n",
+    "display(cf.bus)\n",
+    "display(cf.gen)"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "c7bfe67c",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# cf.to_excel(\"../data/case9_reduced.xlsx\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "0031003f",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "env",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}
diff --git a/tests/test_core.py b/tests/test_core.py
index e88f8c6..215e003 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -304,3 +304,21 @@ def test_reset_index_and_infer_numpy_case9():
     cf_reset.reset_index()
     cf_reset.reset_index()
     assert_frames_struct_equal(cf, cf_reset)
+
+    # removing first row of bus and gen, converting to mpc, then back to cf:
+    # bus index is preserved (via BUS_I), but generator index is not (no named ID column)
+    cf2 = CaseFrames(CASE_PATH_CASE9)
+    cf2.bus = cf2.bus.iloc[1:]  # drop first bus row, so bus.index starts at 2
+    cf2.gen = cf2.gen.iloc[1:]  # drop first gen row, so gen.index starts at 2
+
+    assert cf2.bus.index[0] == 2
+    assert cf2.gen.index[0] == 2
+
+    mpc = cf2.to_mpc()
+    cf2_rt = CaseFrames(mpc)
+
+    # BUS_I is explicit so it survives the round-trip
+    assert np.array_equal(cf2_rt.bus["BUS_I"].values, cf2.bus["BUS_I"].values)
+
+    # gen has no named index column — round-trip resets to 1-based RangeIndex
+    assert cf2_rt.gen.index.tolist() == list(range(1, len(cf2_rt.gen) + 1))