# What harmonic distortion limits should my factory meet at the supply point?

Canonical: https://senseible.earth/answers/harmonic-distortion-limits-factory-thd

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.

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- [Power factor rebates and penalties](https://senseible.earth/answers/power-factor-rebate-and-penalty)

Sources: [BEE, Energy Conservation Guidelines for MSME Sector (2019): section 5.9, Tables 5.18 and 5.19 (from IEEE 519-1992)](https://beeindia.gov.in/WriteReadData/L45218/1734411984.pdf)

Last reviewed 2026-10-24.