Electrical distribution system

Visual Observations	Equipment	Definition	Observations
	Cables and bus	Distributes electrical power throughout a building, connecting various components of an electrical distribution system.	No sharp bends No physical damage No signs of heat No temporary wiring Free of moisture and oil
	Switchgear	Combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to deenergize equipment to allow work to be done and to clear faults downstream.	Covers in place Labeled Accessible No signs of water Vent openings clear
	Circuit breakers	Controlling power to a circuit as well as providing protection to equipment in that circuit by interrupting fault conditions.	Enclosed Labeled Accessible No physical damage No signs of heat No signs of distress No missing knockouts
	Transformers	Device that transfers electric energy from one alternating current circuit to one or more other circuits, either increasing (stepping up) or reducing (stepping down) the voltage.	Open and accessible No dirt accumulations No physical damage No signs of overheating No leakage (oil filled) Adequately protected

Operation and maintenance	Keep it ____________
Read and follow all manufacturers' guidelines and instructions for periodic service, maintenance and inspection of equipment and systems. Caution— Always de-energize electrical equipment before testing, cleaning or performing maintenance.	COOL	All vent and air circulation openings must be clear and operational. Installed filters should be cleaned or replaced. It is important to prevent excessive heat buildup in electrical enclosures and equipment rooms.
	CLEAN	Dust and/or dirt accumulations should be removed from the equipment and surroundings. Space in switchrooms and switchgear enclosures should not be used for storing tools, supplies or other material.
	DRY	Precaution should be taken to prevent steam, chemicals, moisture or condensation from entering electrical enclosures.
	TIGHT	Clean and tighten all loose parts and replace any that are worn. Equipment should be manually exercised to establish that moving parts do not bind and are free to operate.

Electrical testing	Equipment	Testing	Frequency
Testing frequency guidelines should be tempered by the size of the equipment, the location of the equipment, the frequency of operation and the criticality it represents.	Cables and bus	Infrared thermography Visual inspect/clean/adjust	Annually 3 years
	Switchgear	Infrared thermography Visual inspect/clean/adjust Contact resistance test	Annually 3 years 3 years
	Circuit breakers	Infrared thermography Visual inspect/clean/adjust Contact resistance, breaker trip, relay calibration	Annually 3 years 3 years
	Transformers	Infrared thermography Visual inspect- Power factor, turns ratio	Annually Annually 5 years
	In addition: Dry-type Power & distribution	Insulation resistance test Dissolved gas analysis, oil screen tests	3 years Yearly

For a more detailed description on electrical maintenance and testing, consult Standard for an Electrical Preventive Maintenance (EPM) Program.

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The recommendation(s), advice and contents of this material are provided for informational purposes only and do not purport to address every possible legal obligation, hazard, code violation, loss potential or exception to good practice. The Hanover Insurance Company and its affiliates and subsidiaries ("The Hanover") specifically disclaim any warranty or representation that acceptance of any recommendations or advice contained herein will make any premises, property or operation safe or in compliance with any law or regulation. Under no circumstances should this material or your acceptance of any recommendations or advice contained herein be construed as establishing the existence or availability of any insurance coverage with The Hanover. By providing this information to you, The Hanover does not assume (and specifically disclaims) any duty, undertaking or responsibility to you. The decision to accept or implement any recommendation(s) or advice contained in this material must be made by you.

LC MAR 2019 13-349
171-1084 (3/14)

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Electrical distribution system