diff --git a/web/src/components/CaseBuilder/CaseBuilder.tsx b/web/src/components/CaseBuilder/CaseBuilder.tsx
index 16aed1b..1650953 100644
--- a/web/src/components/CaseBuilder/CaseBuilder.tsx
+++ b/web/src/components/CaseBuilder/CaseBuilder.tsx
@@ -23,6 +23,7 @@ import { preprocess } from "../../core/Operations/preprocessing";
 import Toast from "../Common/Forms/Toast";
 import ProfiledUnitsComponent from "./ProfiledUnits";
 import ThermalUnitsComponent from "./ThermalUnits";
+import TransmissionLinesComponent from "./TransmissionLines";
 
 export interface CaseBuilderSectionProps {
   scenario: UnitCommitmentScenario;
@@ -121,6 +122,11 @@ const CaseBuilder = () => {
           onDataChanged={onDataChanged}
           onError={setToastMessage}
         />
+        <TransmissionLinesComponent
+          scenario={scenario}
+          onDataChanged={onDataChanged}
+          onError={setToastMessage}
+        />
         <Toast message={toastMessage} />
       </div>
       <Footer />
diff --git a/web/src/components/CaseBuilder/ProfiledUnits.test.ts b/web/src/components/CaseBuilder/ProfiledUnits.test.ts
index 1939219..81c63f7 100644
--- a/web/src/components/CaseBuilder/ProfiledUnits.test.ts
+++ b/web/src/components/CaseBuilder/ProfiledUnits.test.ts
@@ -104,7 +104,7 @@ test("generateTableColumns", () => {
     headerSort: false,
     headerWordWrap: true,
     hozAlign: "left",
-    minWidth: 60,
+    minWidth: 75,
     resizable: false,
     title: "00:00",
   });
diff --git a/web/src/components/CaseBuilder/ProfiledUnits.tsx b/web/src/components/CaseBuilder/ProfiledUnits.tsx
index 162b66e..4029bb6 100644
--- a/web/src/components/CaseBuilder/ProfiledUnits.tsx
+++ b/web/src/components/CaseBuilder/ProfiledUnits.tsx
@@ -55,12 +55,12 @@ export const ProfiledUnitsColumnSpec: ColumnSpec[] = [
   {
     title: "Maximum power (MW)",
     type: "number[T]",
-    width: 60,
+    width: 75,
   },
   {
     title: "Minimum power (MW)",
     type: "number[T]",
-    width: 60,
+    width: 75,
   },
 ];
 
diff --git a/web/src/components/CaseBuilder/ThermalUnits.test.ts b/web/src/components/CaseBuilder/ThermalUnits.test.ts
index 0d2aa97..a5b4a02 100644
--- a/web/src/components/CaseBuilder/ThermalUnits.test.ts
+++ b/web/src/components/CaseBuilder/ThermalUnits.test.ts
@@ -36,7 +36,7 @@ test("generateTableColumns", () => {
     headerSort: false,
     headerWordWrap: true,
     hozAlign: "left",
-    minWidth: 60,
+    minWidth: 75,
     resizable: false,
     title: "1",
   });
diff --git a/web/src/components/CaseBuilder/ThermalUnits.tsx b/web/src/components/CaseBuilder/ThermalUnits.tsx
index eb5286d..e7af112 100644
--- a/web/src/components/CaseBuilder/ThermalUnits.tsx
+++ b/web/src/components/CaseBuilder/ThermalUnits.tsx
@@ -51,19 +51,19 @@ export const ThermalUnitsColumnSpec: ColumnSpec[] = [
     title: "Production cost curve (MW)",
     type: "number[N]",
     length: 10,
-    width: 60,
+    width: 75,
   },
   {
     title: "Production cost curve ($)",
     type: "number[N]",
     length: 10,
-    width: 60,
+    width: 75,
   },
   {
     title: "Startup costs ($)",
     type: "number[N]",
     length: 5,
-    width: 60,
+    width: 75,
   },
   {
     title: "Startup delays (h)",
diff --git a/web/src/components/CaseBuilder/TransmissionLines.tsx b/web/src/components/CaseBuilder/TransmissionLines.tsx
new file mode 100644
index 0000000..7291743
--- /dev/null
+++ b/web/src/components/CaseBuilder/TransmissionLines.tsx
@@ -0,0 +1,186 @@
+/*
+ * UnitCommitment.jl: Optimization Package for Security-Constrained Unit Commitment
+ * Copyright (C) 2020-2025, UChicago Argonne, LLC. All rights reserved.
+ * Released under the modified BSD license. See COPYING.md for more details.
+ */
+
+import SectionHeader from "../Common/SectionHeader/SectionHeader";
+import SectionButton from "../Common/Buttons/SectionButton";
+import {
+  faDownload,
+  faPlus,
+  faUpload,
+} from "@fortawesome/free-solid-svg-icons";
+import DataTable, {
+  ColumnSpec,
+  generateCsv,
+  generateTableColumns,
+  generateTableData,
+  parseCsv,
+} from "../Common/Forms/DataTable";
+import { UnitCommitmentScenario } from "../../core/fixtures";
+import { ColumnDefinition } from "tabulator-tables";
+import FileUploadElement from "../Common/Buttons/FileUploadElement";
+import { useRef } from "react";
+import { ValidationError } from "../../core/Validation/validate";
+import { CaseBuilderSectionProps } from "./CaseBuilder";
+import {
+  changeTransmissionLineData,
+  createTransmissionLine,
+  deleteTransmissionLine,
+  renameTransmissionLine,
+} from "../../core/Operations/transmissionOps";
+import { offerDownload } from "../Common/io";
+
+export const TransmissionLinesColumnSpec: ColumnSpec[] = [
+  {
+    title: "Name",
+    type: "string",
+    width: 100,
+  },
+  {
+    title: "Source bus",
+    type: "busRef",
+    width: 100,
+  },
+  {
+    title: "Target bus",
+    type: "busRef",
+    width: 100,
+  },
+  {
+    title: "Susceptance (S)",
+    type: "number",
+    width: 60,
+  },
+  {
+    title: "Normal flow limit (MW)",
+    type: "number",
+    width: 60,
+  },
+  {
+    title: "Emergency flow limit (MW)",
+    type: "number",
+    width: 60,
+  },
+  {
+    title: "Flow limit penalty ($/MW)",
+    type: "number",
+    width: 60,
+  },
+];
+
+const generateTransmissionLinesData = (
+  scenario: UnitCommitmentScenario,
+): [any[], ColumnDefinition[]] => {
+  const columns = generateTableColumns(scenario, TransmissionLinesColumnSpec);
+  const data = generateTableData(
+    scenario["Transmission lines"],
+    TransmissionLinesColumnSpec,
+    scenario,
+  );
+  return [data, columns];
+};
+
+const TransmissionLinesComponent = (props: CaseBuilderSectionProps) => {
+  const fileUploadElem = useRef<FileUploadElement>(null);
+
+  const onDownload = () => {
+    const [data, columns] = generateTransmissionLinesData(props.scenario);
+    const csvContents = generateCsv(data, columns);
+    offerDownload(csvContents, "text/csv", "transmission.csv");
+  };
+
+  const onUpload = () => {
+    fileUploadElem.current!.showFilePicker((csv: any) => {
+      const [newLines, err] = parseCsv(
+        csv,
+        TransmissionLinesColumnSpec,
+        props.scenario,
+      );
+      if (err) {
+        props.onError(err.message);
+        return;
+      }
+      const newScenario = {
+        ...props.scenario,
+        "Transmission lines": newLines,
+      };
+      props.onDataChanged(newScenario);
+    });
+  };
+
+  const onAdd = () => {
+    const [newScenario, err] = createTransmissionLine(props.scenario);
+    if (err) {
+      props.onError(err.message);
+      return;
+    }
+    props.onDataChanged(newScenario);
+  };
+
+  const onDelete = (name: string): ValidationError | null => {
+    const newScenario = deleteTransmissionLine(name, props.scenario);
+    props.onDataChanged(newScenario);
+    return null;
+  };
+
+  const onDataChanged = (
+    name: string,
+    field: string,
+    newValue: string,
+  ): ValidationError | null => {
+    const [newScenario, err] = changeTransmissionLineData(
+      name,
+      field,
+      newValue,
+      props.scenario,
+    );
+    if (err) {
+      props.onError(err.message);
+      return err;
+    }
+    props.onDataChanged(newScenario);
+    return null;
+  };
+
+  const onRename = (
+    oldName: string,
+    newName: string,
+  ): ValidationError | null => {
+    const [newScenario, err] = renameTransmissionLine(
+      oldName,
+      newName,
+      props.scenario,
+    );
+    if (err) {
+      props.onError(err.message);
+      return err;
+    }
+    props.onDataChanged(newScenario);
+    return null;
+  };
+
+  return (
+    <div>
+      <SectionHeader title="Transmission Lines">
+        <SectionButton icon={faPlus} tooltip="Add" onClick={onAdd} />
+        <SectionButton
+          icon={faDownload}
+          tooltip="Download"
+          onClick={onDownload}
+        />
+        <SectionButton icon={faUpload} tooltip="Upload" onClick={onUpload} />
+      </SectionHeader>
+      <DataTable
+        onRowDeleted={onDelete}
+        onRowRenamed={onRename}
+        onDataChanged={onDataChanged}
+        generateData={() => generateTransmissionLinesData(props.scenario)}
+      />
+      <FileUploadElement ref={fileUploadElem} accept=".csv" />
+    </div>
+  );
+};
+
+export default TransmissionLinesComponent;
diff --git a/web/src/components/Common/Forms/DataTable.tsx b/web/src/components/Common/Forms/DataTable.tsx
index 992ebac..67b652c 100644
--- a/web/src/components/Common/Forms/DataTable.tsx
+++ b/web/src/components/Common/Forms/DataTable.tsx
@@ -288,7 +288,10 @@ export const floatFormatter = (cell: CellComponent) => {
   if (v === "") {
     return "&mdash;";
   } else {
-    return parseFloat(cell.getValue()).toFixed(1);
+    return parseFloat(cell.getValue()).toLocaleString("en-US", {
+      minimumFractionDigits: 1,
+      maximumFractionDigits: 1,
+    });
   }
 };
 
diff --git a/web/src/core/Operations/commonOps.ts b/web/src/core/Operations/commonOps.ts
index e0cf187..e3af76c 100644
--- a/web/src/core/Operations/commonOps.ts
+++ b/web/src/core/Operations/commonOps.ts
@@ -234,3 +234,10 @@ export const changeData = (
   }
   throw Error(`Unknown field: ${fieldName}`);
 };
+export const assertBusesNotEmpty = (
+  scenario: UnitCommitmentScenario,
+): ValidationError | null => {
+  if (Object.keys(scenario.Buses).length === 0)
+    return { message: "Profiled unit requires an existing bus." };
+  return null;
+};
diff --git a/web/src/core/Operations/generatorOps.ts b/web/src/core/Operations/generatorOps.ts
index 10ee096..56fef26 100644
--- a/web/src/core/Operations/generatorOps.ts
+++ b/web/src/core/Operations/generatorOps.ts
@@ -8,6 +8,7 @@ import { Generators, UnitCommitmentScenario } from "../fixtures";
 import { generateTimeslots } from "../../components/Common/Forms/DataTable";
 import { ValidationError } from "../Validation/validate";
 import {
+  assertBusesNotEmpty,
   changeData,
   generateUniqueName,
   renameItemInObject,
@@ -15,14 +16,6 @@ import {
 import { ProfiledUnitsColumnSpec } from "../../components/CaseBuilder/ProfiledUnits";
 import { ThermalUnitsColumnSpec } from "../../components/CaseBuilder/ThermalUnits";
 
-const assertBusesNotEmpty = (
-  scenario: UnitCommitmentScenario,
-): ValidationError | null => {
-  if (Object.keys(scenario.Buses).length === 0)
-    return { message: "Profiled unit requires an existing bus." };
-  return null;
-};
-
 export const createProfiledUnit = (
   scenario: UnitCommitmentScenario,
 ): [UnitCommitmentScenario, ValidationError | null] => {
diff --git a/web/src/core/Operations/transmissionOps.test.ts b/web/src/core/Operations/transmissionOps.test.ts
new file mode 100644
index 0000000..1300e2c
--- /dev/null
+++ b/web/src/core/Operations/transmissionOps.test.ts
@@ -0,0 +1,75 @@
+/*
+ * UnitCommitment.jl: Optimization Package for Security-Constrained Unit Commitment
+ * Copyright (C) 2020-2025, UChicago Argonne, LLC. All rights reserved.
+ * Released under the modified BSD license. See COPYING.md for more details.
+ */
+
+import { TEST_DATA_1 } from "../fixtures.test";
+import assert from "node:assert";
+import {
+  changeTransmissionLineData,
+  createTransmissionLine,
+  deleteTransmissionLine,
+  renameTransmissionLine,
+} from "./transmissionOps";
+import { ValidationError } from "../Validation/validate";
+
+test("createTransmissionLine", () => {
+  const [newScenario, err] = createTransmissionLine(TEST_DATA_1);
+  assert(err === null);
+  assert.equal(Object.keys(newScenario["Transmission lines"]).length, 2);
+  assert("l2" in newScenario["Transmission lines"]);
+});
+
+test("renameTransmissionLine", () => {
+  const [newScenario, err] = renameTransmissionLine("l1", "l3", TEST_DATA_1);
+  assert(err === null);
+  assert.deepEqual(newScenario["Transmission lines"]["l3"], {
+    "Source bus": "b1",
+    "Target bus": "b2",
+    "Susceptance (S)": 29.49686,
+    "Normal flow limit (MW)": 15000.0,
+    "Emergency flow limit (MW)": 20000.0,
+    "Flow limit penalty ($/MW)": 5000.0,
+  });
+  assert.equal(Object.keys(newScenario["Transmission lines"]).length, 1);
+});
+
+test("changeTransmissionLineData", () => {
+  let scenario = TEST_DATA_1;
+  let err: ValidationError | null;
+  [scenario, err] = changeTransmissionLineData(
+    "l1",
+    "Source bus",
+    "b3",
+    scenario,
+  );
+  assert.equal(err, null);
+  [scenario, err] = changeTransmissionLineData(
+    "l1",
+    "Normal flow limit (MW)",
+    "99",
+    scenario,
+  );
+  assert.equal(err, null);
+  [scenario, err] = changeTransmissionLineData(
+    "l1",
+    "Target bus",
+    "b1",
+    scenario,
+  );
+  assert.equal(err, null);
+  assert.deepEqual(scenario["Transmission lines"]["l1"], {
+    "Source bus": "b3",
+    "Target bus": "b1",
+    "Susceptance (S)": 29.49686,
+    "Normal flow limit (MW)": 99,
+    "Emergency flow limit (MW)": 20000.0,
+    "Flow limit penalty ($/MW)": 5000.0,
+  });
+});
+
+test("deleteTransmissionLine", () => {
+  const newScenario = deleteTransmissionLine("l1", TEST_DATA_1);
+  assert.equal(Object.keys(newScenario["Transmission lines"]).length, 0);
+});
diff --git a/web/src/core/Operations/transmissionOps.ts b/web/src/core/Operations/transmissionOps.ts
new file mode 100644
index 0000000..6e90f21
--- /dev/null
+++ b/web/src/core/Operations/transmissionOps.ts
@@ -0,0 +1,89 @@
+/*
+ * UnitCommitment.jl: Optimization Package for Security-Constrained Unit Commitment
+ * Copyright (C) 2020-2025, UChicago Argonne, LLC. All rights reserved.
+ * Released under the modified BSD license. See COPYING.md for more details.
+ */
+
+import { TransmissionLine, UnitCommitmentScenario } from "../fixtures";
+import {
+  assertBusesNotEmpty,
+  changeData,
+  generateUniqueName,
+  renameItemInObject,
+} from "./commonOps";
+import { ValidationError } from "../Validation/validate";
+import { TransmissionLinesColumnSpec } from "../../components/CaseBuilder/TransmissionLines";
+
+export const createTransmissionLine = (
+  scenario: UnitCommitmentScenario,
+): [UnitCommitmentScenario, ValidationError | null] => {
+  const err = assertBusesNotEmpty(scenario);
+  if (err) return [scenario, err];
+  const busName = Object.keys(scenario.Buses)[0]!;
+  const name = generateUniqueName(scenario["Transmission lines"], "l");
+  return [
+    {
+      ...scenario,
+      "Transmission lines": {
+        ...scenario["Transmission lines"],
+        [name]: {
+          "Source bus": busName,
+          "Target bus": busName,
+          "Susceptance (S)": 1.0,
+          "Normal flow limit (MW)": 1000,
+          "Emergency flow limit (MW)": 1500,
+          "Flow limit penalty ($/MW)": 5000.0,
+        },
+      },
+    },
+    null,
+  ];
+};
+
+export const renameTransmissionLine = (
+  oldName: string,
+  newName: string,
+  scenario: UnitCommitmentScenario,
+): [UnitCommitmentScenario, ValidationError | null] => {
+  const [newLine, err] = renameItemInObject(
+    oldName,
+    newName,
+    scenario["Transmission lines"],
+  );
+  if (err) return [scenario, err];
+  return [{ ...scenario, "Transmission lines": newLine }, null];
+};
+
+export const changeTransmissionLineData = (
+  line: string,
+  field: string,
+  newValueStr: string,
+  scenario: UnitCommitmentScenario,
+): [UnitCommitmentScenario, ValidationError | null] => {
+  const [newLine, err] = changeData(
+    field,
+    newValueStr,
+    scenario["Transmission lines"][line]!,
+    TransmissionLinesColumnSpec,
+    scenario,
+  );
+  if (err) return [scenario, err];
+  return [
+    {
+      ...scenario,
+      "Transmission lines": {
+        ...scenario["Transmission lines"],
+        [line]: newLine as TransmissionLine,
+      },
+    },
+    null,
+  ];
+};
+
+export const deleteTransmissionLine = (
+  name: string,
+  scenario: UnitCommitmentScenario,
+): UnitCommitmentScenario => {
+  const { [name]: _, ...newLines } = scenario["Transmission lines"];
+  return { ...scenario, "Transmission lines": newLines };
+};
diff --git a/web/src/core/fixtures.test.ts b/web/src/core/fixtures.test.ts
index 7c049a9..916ae9a 100644
--- a/web/src/core/fixtures.test.ts
+++ b/web/src/core/fixtures.test.ts
@@ -45,6 +45,16 @@ export const TEST_DATA_1: UnitCommitmentScenario = {
       "Minimum power (MW)": [0, 0, 0, 0, 0],
     },
   },
+  "Transmission lines": {
+    l1: {
+      "Source bus": "b1",
+      "Target bus": "b2",
+      "Susceptance (S)": 29.49686,
+      "Normal flow limit (MW)": 15000.0,
+      "Emergency flow limit (MW)": 20000.0,
+      "Flow limit penalty ($/MW)": 5000.0,
+    },
+  },
 };
 
 export const TEST_DATA_2: UnitCommitmentScenario = {
@@ -60,6 +70,7 @@ export const TEST_DATA_2: UnitCommitmentScenario = {
     b3: { "Load (MW)": [0, 30, 0, 40] },
   },
   Generators: {},
+  "Transmission lines": {},
 };
 
 export const TEST_DATA_BLANK: UnitCommitmentScenario = {
@@ -71,6 +82,7 @@ export const TEST_DATA_BLANK: UnitCommitmentScenario = {
   },
   Buses: {},
   Generators: {},
+  "Transmission lines": {},
 };
 
 test("fixtures", () => {});
diff --git a/web/src/core/fixtures.tsx b/web/src/core/fixtures.tsx
index 9130245..dcd3b66 100644
--- a/web/src/core/fixtures.tsx
+++ b/web/src/core/fixtures.tsx
@@ -38,6 +38,15 @@ export interface ThermalUnit {
   "Must run?": boolean;
 }
 
+export interface TransmissionLine {
+  "Source bus": string;
+  "Target bus": string;
+  "Susceptance (S)": number;
+  "Normal flow limit (MW)": number;
+  "Emergency flow limit (MW)": number;
+  "Flow limit penalty ($/MW)": number;
+}
+
 export interface UnitCommitmentScenario {
   Parameters: {
     Version: string;
@@ -47,6 +56,9 @@ export interface UnitCommitmentScenario {
   };
   Buses: Buses;
   Generators: Generators;
+  "Transmission lines": {
+    [name: string]: TransmissionLine;
+  };
 }
 
 const getTypedGenerators = <T extends any>(
@@ -81,6 +93,7 @@ export const BLANK_SCENARIO: UnitCommitmentScenario = {
   },
   Buses: {},
   Generators: {},
+  "Transmission lines": {},
 };
 
 export const TEST_SCENARIO: UnitCommitmentScenario = {
@@ -176,4 +189,14 @@ export const TEST_SCENARIO: UnitCommitmentScenario = {
       "Must run?": false,
     },
   },
+  "Transmission lines": {
+    l1: {
+      "Source bus": "b1",
+      "Target bus": "b2",
+      "Susceptance (S)": 29.49686,
+      "Normal flow limit (MW)": 15000.0,
+      "Emergency flow limit (MW)": 20000.0,
+      "Flow limit penalty ($/MW)": 5000.0,
+    },
+  },
 };