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Chapter 3



The mission of engineer prime power units is to generate electrical power and provide advice and technical assistance on all aspects of electrical power and distribution systems in support of military operations. This mission statement encompasses military operations across the entire continuum of military operations to include disaster relief, humanitarian assistance, and other operations short of war. Engineer prime power units support sustainment engineering efforts by providing reliable power generation and power-related technical expertise.


Engineer prime power units can produce large quantities of reliable power with their organic 750-kW generators. They can also install, operate, and maintain nonstandard, portable power-generation equipment and operate and maintain some fixed commercial power plants. The units' power-generation capability allows them to --

1. Provide power to locations where another source is not available or is inadequate.

2. Replace existing power sources such as large concentrations of TACGENS.

3. Augment existing commercial power.

Organic Equipment

Each prime power team is equipped with four 750-kW generators, giving the team a 3-MW peak power-production capability. The team can configure its generators into one large power plant or two smaller plants. Table 3-1 shows the various possible configurations and the manpower requirements for continuous operation.

The team can install and operate these plants in any of three modes. Chapter 4 contains information on the three modes of power generation. Appendix A contains a discussion of power-generation concepts.

Nonstandard Portable Equipment

The prime power team can install, operate, repair, and maintain nonstandard portable generators when they are available. Nonstandard generators are nonmilitary, commercial-type generators. Once installed and operational, these generators should be turned over to the supported unit to operate and maintain, thus freeing the prime power team for additional missions. The prime power unit can train the requesting unit personnel to operate and maintain this equipment. Supported units may use contracting channels to rent or lease these generators. In some cases, nonstandard generators may already be installed as backup. An important consideration when using nonstandard equipment is the availability of service and repair parts. The prime power team can perform damage assessment of nonstandard power-generation equipment and, subject to availability of repair and service parts, repair the equipment and return it to operation. Army Regulation (AR) 700-101 precludes the purchase of nonmilitary-standard generators without the express approval of the program manager-mobile electric power (PM-MEP).

Fixed Power Plants

Prime power units have a limited capability to operate, maintain, and perform damage assessment of some fixed commercial power plants, especially diesel-engine- and gas-turbine-driven plants. Continuous operation of large fixed plants exceeds the manpower capabilities of the team. In all cases, the prime power team should work with indigenous power-plant operators or contracted technicians who are familiar with the power plant. Prime power unit personnel cannot operate nuclear and fossil-fuel steam-powered plants or hydroelectric plants.


In addition to producing power, the prime power unit performs many other technical power-related tasks. These include --

1. Conducting load surveys.

2. Performing analyses and design of distribution systems.

3. Performing construction, maintenance, and repair of distribution systems.

4. Performing damage assessment of distribution system.

5. Operating and maintaining industrial power systems and controls.

6. Providing power-related staff assistance.

7. Providing power-related technical assistance to CORs.

Load Survey

A load survey is an analysis of power requirements. The load survey is a vital preliminary step in providing prime power support. The prime power team conducts a load survey to determine the amount of power a supported unit needs and what the distribution requirements are. The load survey also determines the level of reliability required and identifies any special power requirements or problems. The recommended power source is determined based on the load survey. A thorough load survey must be completed before work can begin on the installation of a power plant or the design of a distribution system.

Distribution-System Analysis and Design

The prime power team performs analyses of existing distribution networks to determine their capacity and characteristics. This is useful in determining how much power is available on a system and whether the system is expandable or not. It is also useful in identifying potential electrical hazards that could result in damage to connected equipment, electrocution, or electrical fire. The prime power unit also designs temporary, ground-laid distribution systems. The design includes sizing of conductors, breakers, switches, transformers, load centers, and other devices. Design calculations include voltage drops as a result of line loss and grounding requirements. Systems are designed in compliance with current National Electric Code (NEC) standards. The completed design includes circuit diagram and site layout drawings or sketches, a complete bill of materials (BOM), estimated work requirements, and construction time. For more complex projects, a critical path method (CPM) diagram is also produced. The Army Facilities Components System (AFCS) construction plans contain standardized construction plans for power systems. Prime power units use these off-the-shelf designs where applicable. AFCS is discussed in Chapter 4.

Distribution-System Construction, Maintenance, and Repair

Prime power teams can construct and maintain temporary, ground-laid (or buried) primary and secondary distribution systems. All distribution systems are designed and constructed with approved material and methods and include appropriate devices. Prime power units have a limited capability to maintain overhead distribution systems. Construction and maintenance of extensive overhead distribution systems should be accomplished through use of contracts. Prime power personnel can make connections to existing distribution networks.

The manpower requirements for construction, maintenance, and repair of nonstandard distribution networks depend on a wide diversity of variables. Workload estimates for these tasks, which are provided below, are for planning and estimating purposes only and are highly dependent on controlling variables. For planning and estimating purposes, a team can --

1. Maintain 25 kilometers (km) of overhead or ground-laid primary distribution line. Maintain 10 km of buried primary distribution line. This is roughly equivalent to the distribution system of a small rural town.

2. Construct or repair 1,500 meters of ground-laid primary distribution line per day. This includes making in-line cable splices but does not include making connections to distribution transformers.

3. Make 12 connections per day to the primary side of pad-mounted distribution transformers. Make 4 connections per day to the primary side of pole-mounted transformers.

4. Maintain 25 km of overhead or ground-laid secondary distribution line. Maintain 10 km of buried secondary distribution line.

5. Construct or repair 800 meters of ground-laid secondary distribution line per day. This includes making in-line splices but does not include making connections to distribution transformers, load centers, or service equipment.

6. Make 20 connections per day to service equipment, load centers, and the secondary side of pad-mounted distribution transformers. Make 6 connections per day to the secondary side of pole-mounted transformers.

Prime power teams are not normally used to perform interior electrical work such as interior wiring. This function is performed by the vertical construction platoon of the combat-heavy, engineer-battalion line companies and by engineer utilities detachments. When installing secondary distribution, the prime power team's responsibilities end at the service entrance. The prime power team is responsible for making the connections to the service equipment. Service equipment, which is installed by interior electricians, is the main distribution panel or switched fuse box inside the structure. The prime power team does conduct a safety inspection of the interior branch circuits and connections before energizing the service equipment.

Industrial Power System Maintenance and Operation

Because the prime power teams have working knowledge of multiple power systems, they are able to repair, maintain, and operate industrial power systems and their associated controls. These power systems may be encountered in factories or other production plants where large quantities of power are required to operate heavy machinery. They may also be encountered in facilities such as ports, fuel-storage complexes, hospitals, refrigeration warehouses, and rail-switching centers. The team can also repair and maintain airfield lighting and other specialized illumination systems.

Technical Assistant to Staff

The prime power unit provides power-related technical advice to the appropriate engineer staffs. The prime power unit commander is the theater's subject-matter expert for electrical power. In this role, he acts as an electrical engineer staff officer to the theater engineer in a mature theater, or to the supported headquarters when a theater engineer is not available, providing information and recommendations on power-related issues.

Technical Assistance to CORs

The prime power unit provides power-related technical assistance to CORs. Prime power personnel can help develop specifications for electrical performance contracts and purchase contracts for electrical material. Performance contracts are needed when a power project exceeds the construction capabilities of the prime power unit or when contracted services are preferred over troop labor. In addition to developing specifications for contracts, prime power personnel also help perform the technical evaluation of the bids that are received. This assistance is available to both military engineer units and supporting USACE personnel.

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