What harmonic distortion limits should my factory meet at the supply point?
BEE's MSME guidelines adopt IEEE 519-1992 limits at the point of common coupling: total voltage distortion of 8%, with 5% for any single harmonic, at 1 kV and below, and 5% total with 3% individual from 1 kV to 69 kV. Current limits depend on the ratio of short circuit current to load current.
Voltage distortion limits
- Bus voltage up to 1.0 kV: 5.0% individual harmonic, 8.0% total harmonic distortion (THD)
- Above 1 kV up to 69 kV: 3.0% individual, 5.0% THD
Current distortion limits
- Short circuit to load current ratio below 20: total demand distortion (TDD) 5.0%, with 4.0% for odd harmonics from the 3rd up to the 9th
- Ratio from 20 to 50: TDD 8.0%, with 7.0% for odd harmonics from the 3rd up to the 9th
- Higher harmonic orders have tighter limits in the same table
Where and how often to measure
Measure at the point of common coupling, which BEE places between the plant and the supply network and between non-linear loads and other loads. Log voltage and current THD with a power analyser every month and check that filters are working.
Ways to bring distortion down
- Pulse width modulation AC drives and drives with good choke filtering
- Tuned LC filters, shunt filters or harmonic traps, and active filters
- Proper cabling and earthing
- For new low voltage systems, transformers with built-in passive harmonic filtering
Check your own supply terms
Your discom's supply code or connection agreement may set its own limits. Use those where they differ.
What Senseible does here
Senseible works from bills, so it sees the effect of harmonics only through units and power factor. Distortion itself needs a power analyser at the incomer.
Last reviewed 2026-10-24.