Power Distribution Systems 1.0-1 August 2017 Sheet 01 001 Contents i Power Distribution Systems System Protection Considerations System Design Overcurrent Protection ii Basic Principles. 1.1-1 and Coordination . 1.5-1 Trends in Systems Design . 1.1-1 Grounding/Ground Fault Protection Goals of System Design . 1.1-2 Grounding—Equipment, 1 Designing a Distribution System System, MV System, Development of a System LV System . 1.6-1 One-Line . 1.2-1 Typical Power System Components 2 Importance of a System Typical Power System One-Line . 1.2-2 Components . 1.7-1 3 Power System One-Line . 1.2-4 Transformers . 1.7-4 Standardized Drawing Generators and Symbols . 1.2-6 Generator Systems . 1.7-13 4 Types of Systems Generator Short-Circuit Types of Systems . 1.3-1 Characteristics. 1.7-16 Power System Analysis Generator Set Sizing 5 Systems Analysis . 1.4-1 and Ratings. 1.7-20 Short-Circuit Currents— Generator Set Installation 6 General . 1.4-1 and Site Considerations . 1.7-21 Fault Current Waveform Capacitors and Relationships . 1.4-3 Power Factor . 1.7-22 7 Fault Current Calculations Motor Power Factor and Methods Index . 1.4-4 Correction . 1.7-23 Typical Application by Facility Type Systems Fault Current Calculations 8 for Specific Equipment— Healthcare Facilities . 1.8-1 Exact Method . 1.4-5 Quick Connect Generator Application Quick Check and Load Bank 9 Table . 1.4-8 Capabilities . 1.8-7 Medium-Voltage Fuses— Power Quality Fault Calculations . 1.4-11 10 Low-Voltage Power Power Quality Terms Technical Circuit Breakers— Overview. 1.9-1 Fault Calculations . 1.4-12 Other Application Considerations 11 Molded-Case Breakers Seismic Requirements . 1.10-1 and Insulated Case Reference Data Circuit Breakers— 12 Fault Calculations . 1.4-13 Codes and Standards . 1.11-1 Low-Voltage Circuit Breaker Suggested IEEE Designations 13 Interrupting Derating for Suffix Letters. 1.11-6 Factors . 1.4-13 Ampacities for Conductors Short-Circuit Calculations— Rated 0–2000 V. 1.11-12 14 Shortcut Method . 1.4-14 Determining X and R Values from Transformer 15 Loss Data . 1.4-17 Voltage Drop . 1.4-20 16 17 18 19 Power Distribution Power 20 21 CA08104001E For more information, visit: www.eaton.com/consultants 1.0-2 Power Distribution Systems August 2017 Sheet 01 002 This page intentionally left blank. i ii 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 For more information, visit: www.eaton.com/consultants CA08104001E Power Distribution Systems 1.1-1 August 2017 System Design Sheet 01 003 Basic Principles Trends in Systems Design The growing impact of adverse weather conditions such as hurricanes and i The best distribution system is one There are many new factors to flooding is now driving incoming that will, cost-effectively and safely, consider in the design of power service and distribution equipment supply adequate electric service to distribution systems. rooms to be located out of basements ii both present and future probable and other low lying areas. Regions loads—this section is intended to aid Federal and state legislation has been prone to these storms often experience in selecting, designing and installing introduced to reduce the output of downed utility power lines and/or 1 such a system. carbon emissions into the environment; flooded manholes, resulting in a loss the intent being the reduction of their of power to thousands of customers. The function of the electric power impact on climate change. In order to In order to quickly return power to 2 distribution system in a building or address the subsequent need for clean these facilities, additional on-site an installation site is to receive power power, there has been an accelerating backup generation is being included in at one or more supply points and trend toward the incorporation of solar both new designs and as upgrades to 3 to deliver it to the lighting loads, and other sustainable energy sources existing sites. This trend for resiliency motors and all other electrically into existing and new building designs. is increasing among grocery stores, operated devices. The importance Energy storage systems (ESS) are now large chain stores and other distribution 4 of the distribution system to the making renewable energy a more facilities requiring refrigeration to keep function of a building makes it viable option by helping to stabilize products from spoiling as well as large imperative that the best system be power output during transient dips or multifamily dwelling complexes in low 5 designed and installed. interruptions to power production. lying flood plain areas. In order to design the best distribution Utility deregulation has also provided Building costs continue to rise and 6 system, the system design engineer financial incentives for building rentable or usable space is now at a must have information concerning the owners and facility managers to premium. To solve both problems, loads and a knowledge of the types participate in peak demand load many design and construction firms 7 of distribution systems that are shaving programs. These programs are looking at off-site prefabrication applicable. The various categories of are intended to reduce load on the of key elements. Forest City Ratner’s buildings have many specific design utility grid in response to a 1 hour or 32-story residential complex adjacent 8 challenges, but certain basic principles 1 day ahead signal from the utility. to Barclay's Arena in Brooklyn, NY, are common to all. Such principles, The users shedding or cycling of non- advanced the modular concept if followed, will provide a soundly essential loads is generally initiated by with individual building sections 9 executed design. a building management system (BMS) constructed at a factory off-site and in conjunction with power monitoring The basic principles or factors requiring erected by crane into place. Resiliency and lighting control equipment. To from storms and floods involving the 10 consideration during design of the ensure uninterrupted operation of key power distribution system include: relocation of electrical equipment out customer loads, incorporation of other of flood prone areas is costly, time ■ Functions of structure, present types of distributed generation such as consuming and takes up precious floor 11 and future fuel cells and diesel or natural gas fired space in a building. Electro Centers or reciprocating generator sets may be ■ Life and flexibility of structure Integrated Power Assemblies (IPA) can desired or required. ■ Locations of service entrance and be fitted out with a variety of electrical 12 distribution equipment, locations Hospital complexes and college distribution equipment and shipped to and characteristics of loads, campuses are increasingly adopting the the site in preassembled modules for locations of unit substations design of central utilities plants (CUPs). mounting on elevated foundation 13 piles, building setbacks or rooftops. ■ Demand and diversity factors In lieu of a separate boiler plant, of loads cogeneration is used to produce Finally, the need to have qualified electricity and the wasted heat from 14 ■ Sources of power; including building electrical operators, the combustion process is recaptured normal, standby and emergency maintenance departments and facility to provide hot water for the campus. (see Ta b 4 0 ) engineers has collided with growing 15 Large cogeneration plants (3 MW and expectations for improved productivity ■ Continuity and quality of power above) often include large turbines or available and required (see Ta b 3 3 ) and reduced overall operating costs. reciprocating engines as their prime The increasing proliferation of smart ■ 16 Energy efficiency and management movers for the generators. To enhance devices and enhanced connectivity ■ Distribution and utilization voltages service continuity, these generators with power distribution equipment ■ Busway and/or cable feeders use a continuous source of natural has expanded facility owner’s 17 (see Tab 24) gas as their fuel supply. Cogen plants options. These capabilities allow for generally have higher power conver- ■ Distribution equipment and automated communication of vital sion efficiencies and produce lower motor control power system information including carbon emissions. 18 ■ Power and lighting panelboards energy data, equipment wellness and and motor control centers predictive diagnostics, and electrical (see Tabs 22, 23 and 29) equipment control. 19 ■ Types of lighting systems ■ Installation methods 20 ■ Power monitoring systems (see Tabs 2 and 3) ■ Electric utility requirements 21 CA08104001E For more information, visit: www.eaton.com/consultants 1.1-2 Power Distribution Systems System Design August 2017 Sheet 01 004 The future “Internet of Things” provided, for speeding up the OSHA has qualified a number of i promises to add millions of more clearing time of a circuit breaker Nationally Recognized Testing sensors and other devices to collect that can be set to trip at 1200 A or Laboratories (NRTL) to demon- operational data and send it through above. Eaton’s Arcflash Reduction strate and certify “product ii the Internet to “cloud-based” comput- Maintenance System™ is avail- conformance to the applicable ing services. There, information from able in various electronic trip product safety test standards.” multiple devices can be analyzed and units for molded-case and power Among the oldest and most 1 actions can be taken to optimize circuit breakers to improve clear- respected of these electrical performance and reduce downtime. ing time and reduce the incident product testing organizations is energy level. Underwriters Laboratories (UL), 2 Various sections of this guide cover which was founded in 1894. the application and selection of such The National Electrical Code® systems and components that may (NEC®), NFPA® 70 and NFPA 70E, It is the responsibility of the design 3 be incorporated into the power as well as local electrical codes, engineer to be familiar with the equipment being designed.