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Digital IDMT Overcurrent Relay: Time-Current Characteristics

Approx. component budget: Rs. 6,000 - 10,000

Objective

Build a digital overcurrent relay and check how well its trip times follow the standard IDMT curves for different plug and time settings.

What you will build

A microcontroller-based relay with a current transformer input, selectable standard inverse, very inverse and extremely inverse curves, a trip output and a test load with adjustable fault current.

Results you can expect

• Trip time vs current curves for 3 characteristics
• Comparison with IEC formulas
• Effect of time multiplier setting
• Grading between two relays

What you will learn

Power system protection, relay characteristics and coordination, important for substation and plant engineers.

Tools and notes

Arduino/ESP32, current transformer, relay output, Excel. Fault tests are done at low current with a rheostat or resistive load, never with real short circuits.

Resume points from this project

• Built and tested Digital IDMT Overcurrent Relay: Time-Current Characteristics; objective: build a digital overcurrent relay and check how well its trip times follow the standard IDMT curves for different plug and time settings.
• Measured and analysed trip time vs current curves for 3 characteristics and comparison with IEC formulas; wrote the report and presented the results in a viva. Add your own numbers: [x].

Replace [x] with your own measured results. Write only what you really did.

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