# IEEE C57.21 — Which OSHA NRTL is recognized for which test standard: all 21 labs' scopes of recognition, cross-referenced

For IEEE C57.21, laboratory is UL LLC; standard title is Shunt Reactors Over 500 kVA, verified against its source on 2026-08-10.

- **Laboratory:** UL LLC _(verified: appears in the quote below)_
- **Standard number:** IEEE C57.21 _(verified: appears in the quote below)_
- **Standard title:** Shunt Reactors Over 500 kVA _(verified: appears in the quote below)_

## What the source says

> IEEE C57.21 | Shunt Reactors Over 500 kVA |

## Source

- https://www.osha.gov/nationally-recognized-testing-laboratory-program/ul

Last verified: 2026-08-10. Review by: 2026-12-08.
Part of [Which OSHA NRTL is recognized for which test standard: all 21 labs' scopes of recognition, cross-referenced](https://referencesource.org/nrtl-recognition-scopes/).