# Neutral earthing resistor

Outdoor neutral earthing resistor: stacks of stainless grid elements on post insulators with mica plates and series links, in a ventilated 316 stainless enclosure (louvred sides, roof with overhang) on galvanised legs. Neutral entry by a cable box with ring CT and gland or by a roof bushing; LV earth bushing to the earth bar, two enclosure earth bosses, rating plate with the resistance from kV and amps, HV warning and tag. Energy (kV, A, s) sets the number of stacks; `open` removes a side panel.

**Standards:** IEEE 32, IEC 60529 (IP23), ENA / utility NER specs

## Installation

```bash
npx -y https://decktwin.com/cli/deck-twin-0.2.2.tgz add neutral-earthing-resistor
```

Copies `electrical/neutral-earthing-resistor.tsx`, any helper files it imports and the shared `lib/` into `src/components/deck-twin/`. Needs `three`, `@react-three/fiber` and `@react-three/drei`.

## Usage

```tsx
import { Canvas } from '@react-three/fiber'
import { OrbitControls } from '@react-three/drei'
import { Stage } from './components/deck-twin/lib/stage'
import { NeutralEarthingResistor } from './components/deck-twin/electrical/neutral-earthing-resistor'

export default function Scene() {
  return (
    <Canvas shadows camera={{ position: [8, 5, 9], fov: 35 }}>
      <Stage>
        <NeutralEarthingResistor />
      </Stage>
      <OrbitControls makeDefault />
    </Canvas>
  )
}
```

## Props

| Prop | Type | Default | Range |
| --- | --- | --- | --- |
| `kv` | `3.3 \| 6.6 \| 11 \| 13.8 \| 33` | `11` |  |
| `amps` | `number (A)` | `400` | 50 – 2000 |
| `seconds` | `number (s)` | `10` | 5 – 30 |
| `entry` | `"cable" \| "bushing"` | `"cable"` |  |
| `open` | `boolean` | `false` |  |
| `tag` | `string` | `"NER-8201"` |  |
| `...group` | position, rotation, scale… |  |  |

## P&ID

Rectangle (IEC resistor) in the line from the transformer or generator star point down to the earth symbol (three shortening horizontal lines), often with a CT on the neutral.

tag NER · IEC 60617 (single-line diagram)

IEC draws resistors as rectangles; ANSI drawings use a zig-zag. A rectangle in a neutral-to-earth connection is an NER; an earthing transformer is a zig-zag winding symbol instead.

Neutral earthing resistor datasheet (IEEE 32) fields and the props they set:

| Field | Prop |
| --- | --- |
| System voltage | `kv` |
| Rated current | `amps` |
| Rated time | `seconds` |
| Neutral entry | `entry` |
| Tag number | `tag` |

## Typical suppliers

Vishay · Pestech. The geometry is generic and sized from public standards. It is not vendor CAD.

## Source

`electrical/neutral-earthing-resistor.tsx`. This is the component file only: it imports shared code, so install it with the command above rather than pasting it alone. https://decktwin.com/r/neutral-earthing-resistor.json has every file.

```tsx
// Neutral earthing resistor: stainless grid elements on insulators in a ventilated 316 enclosure on legs, HV entry bushing, CT cable box, earth bushing. IEEE 32, IEC 60529.
import * as THREE from 'three'
import { Kit, type MatKey, type V3 } from '../lib/kit'
import { paint } from '../lib/materials'
import { KitMesh, useKit, type GroupProps } from '../lib/mesh'
import { tagPlate } from '../lib/parts'
import { signMaterial } from '../lib/textures'
import { cableGland, earthBoss, louvrePanel } from './_parts'
import { ratingPlateMaterial } from './_textures'

export interface NeutralEarthingResistorProps {
  /** system line voltage, kV */
  kv?: number
  /** let-through current, A */
  amps?: number
  /** rated time, s */
  seconds?: number
  /** one side panel removed to show the resistor grids */
  open?: boolean
  /** neutral connection: cable box with ring CT, or roof bushing for an overhead / busbar connection */
  entry?: 'cable' | 'bushing'
  tag?: string
}

export const defaults = {
  kv: 11,
  amps: 400,
  seconds: 10,
  open: false,
  entry: 'cable' as 'cable' | 'bushing',
  tag: 'NER-8201',
}

export function NeutralEarthingResistor(props: NeutralEarthingResistorProps & GroupProps) {
  const { kv, amps, seconds, open, entry, tag, ...group } = { ...defaults, ...props }
  const data = useKit((k) => build(k, { kv, amps, seconds, open, entry, tag }), [kv, amps, seconds, open, entry, tag])
  return (
    <group {...group}>
      <KitMesh data={data} />
    </group>
  )
}

export default NeutralEarthingResistor

function build(k: Kit, p: typeof defaults) {
  const S: MatKey = 'stainless'
  // energy sets the grid count (stacked frames of punched stainless grids)
  const V = (p.kv * 1000) / Math.sqrt(3)
  const MJ = (V * p.amps * p.seconds) / 1e6
  const stacks = Math.max(1, Math.min(6, Math.ceil(MJ / 40))) // typical ~40 MJ per stack
  const tiers = Math.max(2, Math.min(5, Math.ceil(p.kv / 6)))
  const L = 0.4 + stacks * 0.55
  const Wd = 0.9
  const leg = 0.5
  const Hb = 0.35 + tiers * 0.32
  const y0 = leg
  const y1 = leg + Hb
  // legs and base channels
  for (const sx of [-1, 1])
    for (const sz of [-1, 1]) {
      k.box('galvanised', [0.08, leg, 0.08], [sx * (L / 2 - 0.06), leg / 2, sz * (Wd / 2 - 0.06)])
      k.box('galvanised', [0.2, 0.012, 0.2], [sx * (L / 2 - 0.06), 0.006, sz * (Wd / 2 - 0.06)])
    }
  k.box('galvanised', [L, 0.06, Wd], [0, y0 + 0.03, 0])
  // enclosure frame (hollow): corner posts, roof with overhang, mesh / louvred side panels
  for (const sx of [-1, 1]) for (const sz of [-1, 1]) k.box(S, [0.04, Hb, 0.04], [sx * (L / 2 - 0.02), y0 + Hb / 2, sz * (Wd / 2 - 0.02)])
  k.box(S, [L + 0.12, 0.03, Wd + 0.12], [0, y1 + 0.015, 0])
  k.box(S, [L + 0.12, 0.08, 0.01], [0, y1 - 0.01, Wd / 2 + 0.055])
  const qz = new THREE.Quaternion()
  const qzb = new THREE.Quaternion().setFromAxisAngle(new THREE.Vector3(0, 1, 0), Math.PI)
  const qx = new THREE.Quaternion().setFromAxisAngle(new THREE.Vector3(0, 1, 0), Math.PI / 2)
  const qxb = new THREE.Quaternion().setFromAxisAngle(new THREE.Vector3(0, 1, 0), -Math.PI / 2)
  // louvred panels on both long sides (front one removable), plain end panels with the bushings
  const sides: [V3, THREE.Quaternion, number][] = [[[0, y0 + Hb / 2, Wd / 2], qz, L - 0.08], [[0, y0 + Hb / 2, -Wd / 2], qzb, L - 0.08]]
  for (const [i, [c, q, w]] of sides.entries()) {
    if (i === 0 && p.open) continue
    louvrePanel(k, w, Hb - 0.08, c, q, '#c3c7cb')
    louvrePanel(k, w, Hb - 0.08, [c[0], c[1], c[2] * 0.98], q.clone().multiply(qzb), '#c3c7cb')
  }
  for (const s of [-1, 1]) k.box(S, [0.004, Hb - 0.04, Wd - 0.08], [s * (L / 2 - 0.002), y0 + Hb / 2, 0])
  // grid stacks on post insulators, series links, tie rods
  const porcelain = paint('#6e3420', { metalness: 0.05, roughness: 0.15, clearcoat: 0.8 })
  const grid = paint('#9aa0a3', { metalness: 0.7, roughness: 0.5, weather: 0.3 })
  for (let s = 0; s < stacks; s++) {
    const x = -L / 2 + 0.2 + 0.275 + s * 0.55
    for (const dz of [-0.25, 0.25]) for (const dx of [-0.18, 0.18]) k.cyl(porcelain, 0.035, 0.18, [x + dx, y0 + 0.15, dz], 'y', 12)
    for (let t = 0; t < tiers; t++) {
      const yt = y0 + 0.3 + t * 0.32
      for (let g = 0; g < 7; g++) k.box(grid, [0.42, 0.012, 0.55], [x, yt + g * 0.035, 0])
      for (const dz of [-0.3, 0.3]) for (const dx of [-0.2, 0.2]) k.rod(S, [x + dx, yt - 0.02, dz], [x + dx, yt + 0.25, dz], 0.008, 6)
      k.box(paint('#d9d3c0', { roughness: 0.6 }), [0.46, 0.02, 0.6], [x, yt + 0.26, 0]) // mica insulating plate
      k.box('copper', [0.03, 0.3, 0.01], [x + 0.22, yt + 0.12, 0.29])
    }
  }
  // HV neutral entry: porcelain bushing on the roof, cable box with CT underneath on the +X end
  const xb = L / 2 - 0.25
  const LB = 0.2 + p.kv * 0.012
  const prof: [number, number][] = [[0.06, 0], [0.04, 0]]
  for (let i = 0; i < 4; i++) prof.push([0.04, i * (LB / 4) + 0.02], [0.075, i * (LB / 4) + 0.04], [0.04, i * (LB / 4) + 0.07])
  prof.push([0.03, LB], [0, LB])
  if (p.entry === 'bushing') {
    k.cyl(S, 0.09, 0.02, [xb, y1 + 0.04, 0], 'y', 20)
    k.boltCircle('boltXylan', 'nut', 6, 0.075, [xb, y1 + 0.03, 0], 'y', 0.01, 0.04, [0.025])
    k.lathe(porcelain, prof, [xb, y1 + 0.05, 0], 'y', 20)
    k.cyl('aluminium', 0.012, 0.08, [xb, y1 + 0.05 + LB + 0.04, 0], 'y', 8)
    k.box('copper', [0.03, 0.12, 0.01], [xb, y1 - 0.08, 0])
  } else {
    const cb: V3 = [L / 2 + 0.2, y0 + Hb * 0.55, 0]
    k.rbox(S, [0.4, 0.5, 0.5], 0.02, cb)
    k.box('nut', [0.14, 0.04, 0.14], [cb[0], cb[1] + 0.05, 0]) // CT window (ring CT behind)
    k.plane(signMaterial('hv'), 0.24, 0.12, [cb[0] + 0.201, cb[1] + 0.12, 0], qx)
    const g = cableGland(k, [cb[0], cb[1] - 0.25, 0], '-y', 0.045)
    k.spline('cable', [g, [g[0], 0.3, 0.05], [g[0] + 0.1, 0.05, 0.15], [g[0] + 0.6, 0.03, 0.2]], 0.024, 8, 20)
  }
  // LV earth bushing on the -X end to the earth bar, two enclosure earth bosses
  k.cyl(porcelain, 0.03, 0.1, [-L / 2 - 0.05, y0 + 0.2, 0.2], 'x', 12)
  k.tube('copper', [[-L / 2 - 0.1, y0 + 0.2, 0.2], [-L / 2 - 0.2, y0 + 0.2, 0.2], [-L / 2 - 0.2, 0.02, 0.2], [-L / 2 - 0.5, 0.02, 0.2]], 0.01, 6, 0.05)
  earthBoss(k, [L / 2 - 0.06, leg * 0.6, Wd / 2 - 0.02], 'z')
  earthBoss(k, [-L / 2 + 0.06, leg * 0.6, -Wd / 2 + 0.02], '-z')
  // rating plate, warning, tag
  k.plane(ratingPlateMaterial('NEUTRAL EARTHING RESISTOR', [`Tag  ${p.tag}`, `System  ${p.kv} kV`, `Current  ${p.amps} A for ${p.seconds} s`, `Resistance  ${(V / p.amps).toFixed(1)} Ω`, 'Element  AISI 304 grid', 'Enclosure  IP23, AISI 316']), 0.3, 0.2, [-L / 2 - 0.003, y0 + Hb * 0.55, -0.15], qxb)
  k.plane(signMaterial('hv'), 0.3, 0.15, [-L / 2 - 0.003, y0 + Hb * 0.85, -0.15], qxb)
  tagPlate(k, p.tag, [-L / 2 - 0.003, y0 + Hb * 0.3, -0.15], '-x', 0.16)
}
```