By: Ken Gilmore, Alabama Power Company
Alabama Power Company is impacted by the Underground Damage Prevention State Law in two very important ways: as an excavator and as an underground facility operator. Not only are we digging trenches, installing new anchors, and installing new poles everyday, but we also have over 10,000 miles of buried electrical facilities that need protecting. When underground power cables are damaged, people can be injured or killed by electric shock, arcing current, or an explosion. Underground power cable damage is the result of cable insulation being penetrated by a sharp object such as a digging tool or being crushed by a derrick truck auger or the bucket of a backhoe. Resulting electrical fires can be catastrophic, especially when damage spreads to other nearby underground facilities such as gas pipelines. In some cases, the difference maker between safe digging and an electrical facility damage event can be: 1) the application of a general understanding of electrical facilities, 2) the visual inspection of above ground electrical facilities and 3) the use of effective communication between the excavator and the electrical facility operator.
- Underground Power Conduit and Cable – Depending on the application and type of soil, Alabama Power Company underground cables are installed with or without conduit. Concrete encased conduit is utilized for critical main line cables. Voltages of Alabama Power Company underground cables range from 120 volt street light cable to 115,000 volt transmission cable. Provided below are pictures of the more commonly installed Alabama Power Company underground conduit and cables:
- 3” PVC Conduit – The PVC conduit utilized with Alabama Power Company underground cable is gray in color. The conduit diameter ranges from 1-1/4” to 6” depending on the type and size cable required inside the conduit.
- #1/0 Insulated Aluminum 15,000 Volt Primary Cable – This is Alabama Power Company’s most common medium voltage (primary) underground cable with other primary cable sizes ranging from #2 AWG to #1000 kCM aluminum (or copper) for Distribution applications.
- 2 #4/0 and 1 #1/0 Insulated Aluminum 600 Volt Secondary Cable – This is Alabama Power Company’s most common low voltage (secondary/service) underground cable. The cable consists of three insulated cables bundled together to provide 120/240 volt residential service.
- 2 #6 Insulated Aluminum 600 Volt Secondary Cable – The main purpose of this low voltage bundled cable is to provide 120 volt service to street lights.
- #6 Bare Copper – For system grounding improvement, bare copper conductor is installed for enhanced grounding applications at new equipment poles and also in the same trench with specified underground cables.
- Visual Above Ground Indicators – In addition to contacting AL811 and non-AL811 members as appropriate, it is highly recommended to perform an inspection of your proposed excavation site for evidence of underground electrical facilities. The following are typical clues that indicate Alabama Power Company underground electrical facilities are located nearby.
Overhead Power Lines – At first glance, it may appear that all electrical facilities are located above the ground. However, “risers” are commonly attached to poles for the purpose of transitioning from an overhead system to an underground system. In addition to overhead power facilities, “riser poles” provide a clear indication of underground power facilities as well.
Electrical Equipment – Electrical equipment not only includes the obvious padmounted transformers and switchgear (“large green boxes”), but also includes smaller above ground equipment such as secondary pedestals. Such equipment will always have associated underground power facilities nearby.
Meters – Electric metering facilities may be attached to the side of a house, building, or a customer-owned pole. If there are no overhead electric utility facilities to the meter, the utility service to the meter is provided underground. It is important to remember that metering locations for residential services indicate electric utility ownership transfer points. Privately-owned lines such as electric service lines past a residential meter should be identified by the property owner. Please remember that Alabama Power Company will not mark these underground facilities. In other words, when digging on the customer side of a residential meter, a private facility locator will be needed to locate buried electrical facilities.
Manholes and Pull Boxes – Similar to other type utilities such as communication, water, and sewer, Alabama Power Company electric facilities may also be located in manholes. In addition, below ground enclosures such as pull boxes and street light junction boxes are used for a smaller size or quantity of underground power cables.
Street Light Poles – Unless overhead power lines are directly attached to a street light pole, the power cables are buried to the street light pole from equipment such as a padmounted transformer or an adjacent street light pole.
Grounding Applications – Not all buried power cables are for street light applications and customer service. To improve system reliability, enhanced grounding is utilized at new Alabama Power Company equipment poles. Enhanced grounding may include ground rods and ground wire installations outside the pole hole in undisturbed earth for improved grounding.
An “Enhanced Grounding Installed” sign is generally attached to the pole at eye level to provide additional notice to the excavator of these below ground electrical facilities. The grounding facilities should be marked with red paint by Alabama Power Company locators, where applicable.
- Communication – A key factor with safe digging practices is effective communication between excavators and underground facility operators. Even though positive response is not currently required by Alabama State Law, Alabama Power Company uses the Voluntary Positive Response Program offered by AL811. This program allows an excavator to know the status of their locate request by viewing the online AL811 WebPortal. Therefore, the potential for miscommunication between excavators and Alabama Power Company underground facility locators can be eliminated and utility cost savings can be achieved since the number of second locate requests are reduced. Provided below is an example application using the AL811 Voluntary Positive Response Program.
POSITIVE RESPONSE STATUS AS OF TUESDAY, AUGUST 21, 2018 4:49 PM Utility replies to the Positive Response System are VOLUNTARY. There may not be an electronic positive response from all utility members posted on-line.
Whenever there is just a possibility that an Alabama Power Company underground facility is damaged, it is critical that AL811 or Alabama Power Company be notified as soon as possible to ensure that prior to reburial of the facility, it is restored and in good condition. Numerous major power outages across the nation have occurred because minor nicks, cuts, or scrapes to electrical facilities were not initially reported but were later determined to be the root cause of the power outage. Please keep in mind that underground power line dig-ins are not only costly to repair but are extremely dangerous. In addition, loss of power can be much more than an inconvenience. The damage can potentially result in loss of power to vital health and safety facilities such as hospitals, law enforcement, fire departments, water treatment facilities and customers on life support.
Ken Gilmore is a Team Leader at Alabama Power Company and serves on the Alabama 811 Board of Directors. Ken has over 35 years of experience in the field of Distribution operations and damage prevention. For questions or comments, Ken can be reached at firstname.lastname@example.org.