Article

Electrical distribution system

Visual Observations

Equipment

Definition

Observations

Cables
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
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 breaker
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
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 deenergize 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

Annually

Visual inspect/clean/adjust 

3 years

Switchgear

Infrared thermography

Annually

Visual inspect/clean/adjust 

3 years

Contact resistance test      

3 years

Circuit breakers

Infrared thermography

Annually

Visual inspect/clean/adjust

3 years

Contact resistance, breaker trip, relay calibration

3 years

Transformers

Infrared thermography

Annually

Visual inspect-

Annually

Power factor, turns ratio

5 years

In addition:
Dry-type
Power and distribution


Insulation resistance test


3 years

Dissolved gas analysis, oil screen tests

Yearly

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


This material is provided for informational purposes only and does not provide any coverage or guarantee loss prevention. The examples in this material are provided as hypothetical and for illustration purposes only. The Hanover Insurance Company and its affiliates and subsidiaries (“The Hanover”) specifically disclaim any warranty or representation that acceptance of any recommendations contained herein will make any premises, or operation safe or in compliance with any law or regulation. 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)