30 CFR § 77.509 - Transformers; installation and guarding.
---
identifier: "/us/cfr/t30/s77.509"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "30 CFR § 77.509 - Transformers; installation and guarding."
title_number: 30
title_name: "Mineral Resources"
section_number: "77.509"
section_name: "Transformers; installation and guarding."
chapter_name: "MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR"
subchapter_number: "O"
subchapter_name: "COAL MINE SAFETY AND HEALTH"
part_number: "77"
part_name: "MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "30 U.S.C. 811."
regulatory_source: "36 FR 9364, May 22, 1971, unless otherwise noted."
cfr_part: "77"
---
# 77.509 Transformers; installation and guarding.
(a) Transformers shall be of the totally enclosed type, or shall be placed at least 8 feet above the ground, or installed in a transformer house, or surrounded by a substantial fence at least 6 feet high and at least 3 feet from any energized parts, casings, or wiring.
(b) Transformer stations shall be enclosed to prevent persons from unintentionally or inadvertently contacting energized parts.
(c) Transformer enclosures shall be kept locked against unauthorized entry.