Electrical & Electronics Engineering / IDMT Protective Relays
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LABORATORY 38 · ELECTRICAL & ELECTRONICS ENGINEERING

Inverse Definite Minimum Time (IDMT) Overcurrent and Earth-Fault Relay Characteristics

Calibrate and verify operating time-current characteristics of an induction disc / numerical IDMT overcurrent relay against standard IEC 60255 curves across variable plug settings. Explore interactive circuit analysis, electronics simulation, and electrical engineering telemetry.

CIRCUIT ANALYSIS · ANALOG · DIGITAL · MACHINES · POWER SYSTEMS · CONTROL & INSTRUMENTATION

Your virtual electrical & electronics engineering laboratory.

RELAY OPERATING TRIPPING TIME T_TRIP—
INSTRUMENTATION TELEMETRY

Ready to sample with IDMT Factor = 15.0 factor.

15.0 factor
Calibrated Secondary Current Injection Test Set & Digital Relay Workstation baseline operating point stabilized at 25.0 °C

Adjust IDMT Factor, then execute electrical instrumentation acquisition.

Electrical telemetry is sampled with calibrated high-precision instruments using 64-bit IEEE 754 precision buffers. Residuals reflect ordinary least-squares regression across successive observations. Continuous data structures support high-fidelity circuit and power system modeling.

Electrical engineering assumptions and boundary limits

Assumes ideal linear operating conditions without thermal breakdown or non-linear core saturation Calibrated using the Secondary Current Injection Test Set & Digital Relay Workstation under controlled temperature and 64-bit IEEE 754 precision instrumentation buffers. Ordinary least-squares regression yields R² > 0.99999.

Laboratory apparatus & testing equipment.

IDMT Protective Relays Precision Workstation

Provides regulated excitation, calibrated terminal access, and low-parasitic interconnects for disc driving torque, shading ring flux, time multiplier setting (tms) & discrimination.

True-RMS Digital Multimeter (6.5-digit Keysight / Fluke)

Measures terminal voltages, branch currents, and precision DC/AC parameters with ±0.0035% baseline accuracy.

Dual-Channel Digital Storage Oscilloscope (100 MHz, 1 GSa/s)

Captures time-domain waveforms, phase shifts, transient dynamics, and harmonic spectra for idmt protective relays.

Regulated Linear DC / AC Variable Power Source

Supplies low-noise, ripple-free voltage and current excitation with adjustable current limiting.

Calibrated Decade Resistance & Component Substitution Box

Provides precision 0.1% tolerance standard passive values to establish calibrated idmt factor conditions.

Four-Terminal Kelvin Lead Wire & BNC Coaxial Cable Set

Minimizes lead resistance, inductive pickup, and ambient EMI interference across all test ports.

FOLLOW THE METHOD

A reason behind every step.

Calibrate and verify operating time-current characteristics of an induction disc / numerical IDMT overcurrent relay against standard IEC 60255 curves across variable plug settings. Standardized parameter settings: 6.0, 10.0, 15.0, 20.0, 26.0, 32.0 factor.

  1. Visual Inspection & Pre-Flight Zero Tare: Inspect all circuit connections, breadboard jumpers, and terminal blocks. Verify that instrument ground planes are tied to earth and execute zero tare on all digital meters.
  2. Excitation Source & Baseline Calibration: Energize the regulated supply, set baseline operating thresholds, and calibrate the idmt factor using the precision standard reference meter.
  3. Systematic Parameter Variation & Settling: Increment the idmt factor systematically across the designated experimental range (6.0 to 32.0 factor), permitting thermal settling at each setpoint.
  4. Multi-Meter & Oscilloscope Waveform Acquisition: Record the primary output metric (Relay Operating Tripping Time t_trip) alongside auxiliary telemetry. Verify waveform symmetry, DC offset, and harmonic integrity on the oscilloscope.
  5. Cross-Validation & Redundant Trial Verification: Execute repeated forward and reverse sweeps to detect hysteresis, thermal drift, or non-linear saturation effects across the device under test (DUT).
  6. Shutdown, De-energization & Data Archival: Reduce source excitation smoothly to zero, de-energize all primary supplies, discharge residual capacitive elements, and export raw telemetry to the data buffer.
YOUR NOTEBOOK · 0 OBSERVATIONS

Turn measurements into electrical engineering insight.

See a complete example report ↗

Points are your recorded observations. The solid regression line validates IDMT Protective Relays mathematical scaling.

LINEAR REGRESSION FIT · y = mx + b
t_trip = 0.1400 · [1/(PSM⁰˙⁰² - 1)]
#IDMT Characteristic Factor 1/(PSM⁰˙⁰² - 1) (factor)Relay Operating Tripping Time t_trip (s)IDMT factor 1/(PSM⁰˙⁰² - 1)Relay operating time t_trip (s)

No readings yet. Execute an electrical trial and record it.

CHECK YOUR UNDERSTANDING

Explain what the circuit metrics mean.

Question 1: In the study of IDMT Protective Relays, the primary dependent variable measured is:

Question 2: The mathematical relationship governing IDMT Protective Relays is modeled as:

Question 3: The target benchmark parameter derived from regression analysis is:

Question 4: Which instrumentation technique effectively eliminates lead wire resistance error?

THEORY AND ELECTROMAGNETIC CONTEXT

Electrical engineering background & physical principles.

The experimental analysis of inverse definite minimum time (idmt) overcurrent and earth-fault relay characteristics investigates the electrotechnical behavior of secondary current injection test set & digital relay workstation. This university laboratory module focuses on disc driving torque, shading ring flux, time multiplier setting (tms) & discrimination, establishing accurate mathematical transfer characteristics across standard operational domains.

t_trip = 0.1400 · [1/(PSM⁰˙⁰² - 1)]

Calibrated using the Secondary Current Injection Test Set & Digital Relay Workstation under controlled temperature and 64-bit IEEE 754 precision instrumentation buffers. Ordinary least-squares regression yields R² > 0.99999.