Math & Numbers

Inverse-Time Overcurrent Relay Setting (IEC 60255-151)

Compute the operating time of an inverse-time overcurrent relay per IEC 60255-151: t = TMS·(k/((I/I_s)^α − 1)). Supports Standard Inverse (SI), Very Inverse (VI), Extremely Inverse (EI) and Long-Time Inverse (LTI) curves, and samples a T-I characteristic.

json· JSON resultOpen tool

Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/relay-setting-calculator' \
  -H 'Content-Type: application/json' \
  -d '{"curveType":"SI","pickupCurrent":100,"timeMultiplier":0.2,"faultCurrent":500,"curvePoints":21,"decimalPlaces":4}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST https://api.elysiatools.com/en/api/tools/relay-setting-calculator

Parameters

Name	Type	Required	Description
curveType	select	No	—
pickupCurrent	number	Yes	Relay pickup (setting) current, primary side.
timeMultiplier	number	Yes	Time multiplier setting, typical 0.05 – 1.0.
faultCurrent	number	Yes	Applied fault current. Must exceed pickup (I > I_s) for the relay to operate.
curvePoints	number	No

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-relay-setting-calculator": {
      "name": "relay-setting-calculator",
      "description": "Compute the operating time of an inverse-time overcurrent relay per IEC 60255-151: t = TMS·(k/((I/I_s)^α − 1)). Supports Standard Inverse (SI), Very Inverse (VI), Extremely Inverse (EI) and Long-Time Inverse (LTI) curves, and samples a T-I characteristic.",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=relay-setting-calculator",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "relay-setting-calculator",
    "arguments": {
  "curveType": "SI",
  "pickupCurrent": 100,
  "timeMultiplier": 0.2,
  "faultCurrent": 500,
  "curvePoints": 21,
  "decimalPlaces": 4
}
  }
}

Chain multiple tools in one session with a comma-separated toolId list, e.g. /mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp (max 20).

Questions or issues? Contact [email protected]

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