{
  "node": {
    "id": "term:arc-flash",
    "type": "Term",
    "label": "Arc flash",
    "properties": {
      "id": "arc-flash",
      "name": "Arc flash",
      "aka": [
        "DC arc flash",
        "arc-flash hazard",
        "incident energy"
      ],
      "section": "topic-hvsafety",
      "definition": "The burst of heat, light and pressure released by a fault arc. The hazard to a worker is rated as incident energy at working distance; 1.2 cal/cm² is the usual onset of second-degree burns. Large battery systems can feed fault currents of many kiloamperes, so arc flash sets protective clothing and approach limits under NFPA 70E.",
      "unit": "cal/cm²",
      "related": [
        "arcing",
        "external-short-circuit",
        "stationary-storage",
        "emergency-shutdown",
        "fuse-coordination"
      ],
      "url": "https://lemonergy.com/learn/glossary/arc-flash/",
      "mentions": []
    }
  },
  "edges": [
    {
      "id": "edge:5062",
      "source": "term:arc-flash",
      "target": "topic:topic-hvsafety",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:5063",
      "source": "term:arc-flash",
      "target": "term:arcing",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5064",
      "source": "term:arc-flash",
      "target": "term:external-short-circuit",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5065",
      "source": "term:arc-flash",
      "target": "term:stationary-storage",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5066",
      "source": "term:arc-flash",
      "target": "term:emergency-shutdown",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5067",
      "source": "term:arc-flash",
      "target": "term:fuse-coordination",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-hvsafety",
      "type": "Topic",
      "label": "High-voltage and functional safety",
      "properties": {
        "id": "topic-hvsafety",
        "name": "High-voltage and functional safety",
        "lede": "Keeping people safe from the pack’s voltage and keeping its electronics safe when they fail: insulation, switching, fusing and the functional-safety process.",
        "context": "Relate protection to faults, detection and response.",
        "example": "Normal-operation current limits do not demonstrate correct contactor behavior under a welded-contact or sensor fault.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-basics/",
        "lesson_label": "Open battery basics"
      }
    },
    {
      "id": "term:arcing",
      "type": "Term",
      "label": "Arcing",
      "properties": {
        "id": "arcing",
        "name": "Arcing",
        "aka": [
          "electric arc",
          "DC arc"
        ],
        "section": "topic-hvsafety",
        "definition": "Current continuing through ionised gas across a gap, typically between contacts as they separate. An AC arc goes out by itself at each current zero, a hundred times a second at 50 Hz; a DC arc has no zero and keeps burning until it is stretched and cooled so far that its voltage exceeds the source’s, which makes high-voltage DC far harder to interrupt.",
        "related": [
          "contactor-arc-suppression",
          "arc-flash",
          "contactor",
          "fuse",
          "direct-current",
          "electrical-breakdown"
        ],
        "url": "https://lemonergy.com/learn/glossary/arcing/",
        "mentions": []
      }
    },
    {
      "id": "term:external-short-circuit",
      "type": "Term",
      "label": "External short circuit",
      "properties": {
        "id": "external-short-circuit",
        "name": "External short circuit",
        "section": "topic-safety",
        "definition": "A low-resistance connection between the terminals outside the cell, driving currents of hundreds of amperes. Fuses, the current interrupt device and a positive-temperature-coefficient element are the layers of protection against it.",
        "related": [
          "internal-short-circuit",
          "fuse",
          "current-interrupt-device",
          "ptc",
          "short-circuit-test"
        ],
        "url": "https://lemonergy.com/learn/glossary/external-short-circuit/",
        "mentions": []
      }
    },
    {
      "id": "term:stationary-storage",
      "type": "Term",
      "label": "Stationary storage",
      "properties": {
        "id": "stationary-storage",
        "name": "Stationary storage",
        "abbr": "BESS",
        "aka": [
          "battery energy storage system",
          "ESS"
        ],
        "section": "topic-applications",
        "definition": "Batteries installed in a fixed place — a container at a solar farm, a cabinet in a home — to shift energy in time or support the grid. LFP cells dominate because cost per cycle and safety matter more than mass.",
        "related": [
          "lfp",
          "energy-management-system",
          "inverter",
          "energy-arbitrage",
          "long-duration-storage",
          "ul-9540a"
        ],
        "url": "https://lemonergy.com/learn/glossary/stationary-storage/",
        "mentions": []
      }
    },
    {
      "id": "term:emergency-shutdown",
      "type": "Term",
      "label": "Emergency shutdown",
      "properties": {
        "id": "emergency-shutdown",
        "name": "Emergency shutdown",
        "abbr": "ESD",
        "aka": [
          "emergency stop",
          "E-stop"
        ],
        "section": "topic-hvsafety",
        "definition": "A hard-wired path that takes a battery system to a safe state on command, opening contactors and stopping the power converters regardless of what the software is doing. Stationary systems have red push buttons on the enclosure and often remotely; in vehicles the crash signal and the manual service disconnect play the same role.",
        "related": [
          "contactor",
          "pyrofuse",
          "high-voltage-interlock",
          "stationary-storage",
          "power-plant-controller"
        ],
        "url": "https://lemonergy.com/learn/glossary/emergency-shutdown/",
        "mentions": [
          "enclosure"
        ]
      }
    },
    {
      "id": "term:fuse-coordination",
      "type": "Term",
      "label": "Fuse coordination",
      "properties": {
        "id": "fuse-coordination",
        "name": "Fuse coordination",
        "aka": [
          "selectivity",
          "discrimination",
          "protection coordination"
        ],
        "section": "topic-hvsafety",
        "definition": "Choosing the ratings of fuses and breakers in series so that a fault opens only the device nearest to it and the remainder of the system keeps running. For fuses, the downstream fuse’s total clearing I²t must stay below the upstream fuse’s pre-arcing I²t; in a pack, a cell or module fuse should act before the main fuse or pyrofuse.",
        "formula": "I²t_clearing(downstream) < I²t_pre-arcing(upstream)",
        "related": [
          "fuse",
          "pyrofuse",
          "battery-disconnect-unit",
          "external-short-circuit",
          "series-parallel"
        ],
        "example": {
          "title": "Compare clearing and pre-arcing energy",
          "text": "If a downstream fuse has 500 A²s clearing I²t and the upstream fuse has 1000 A²s pre-arcing I²t under the specified fault conditions, the inequality is satisfied. The full time-current curves and manufacturer coordination rules are still required."
        },
        "url": "https://lemonergy.com/learn/glossary/fuse-coordination/",
        "mentions": []
      }
    }
  ]
}