A coordination study evaluates the impacts of short circuit and equipment failures within a facility and determines the effects on the facility operation. How to use selective coordination in ptw knowledge base. Introduction with the inclusion of new language in the 2005 national electrical code nec, the requirements for selective coordination of electrical power systems are, at present, more stringent than. Now, get the job done in no time with onetouch automation from smartpdc the. Easypower ansi shortcircuit software delivers intelligent, easytouse tools to.
Using a commercial software package that plots the curves. How to achieve selective coordination of circuit breakers. Selective coordination is a design requirement newly added by both the 2005 and 2008 national electrical code to article 700 emergency systems see 700. This includes tested combinations of bussmann series fuses with upstream eaton circuit breakers that provide designers greater flexibility in creating efficient selective coordination solutions for their projects. Nec 2017 requirements for generator set overcurrent. Selective coordination generally describes the design of an electrical system in which the upstream protective device fuse or circuit breaker nearest to the system fault clears the fault without affecting the protective devices that are upstream from it. Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings or settings selective coordination is required for emergency. Oneline diagram a power system diagram that shows how all components are electrically connected is created, or, if one already exists, updated. Calculate momentary close and latch, interrupting duty and relay currents for. Nec rule 6 x i fl 6 x i fl 6 x i fl timecurrent curves transformers 29.
Nec 2017 requirements for generator set overcurrent protection. Lighting circuit 94 tube 4, 50vatube 115v fluorescent circuits. This breaker type is available in four aic rating models, the fd6 3535 kaic at 240480v, the hfd6 10065 kaic, the hhfd6 200100 kaic, and the cfd6 200200 kaic refer to the speedfax product catalog for the correct circuit breaker. Load rated switches, circuit breakers, or other devices specifically designed as. The protective device is a lowvoltage power circuit breaker with a solidstate trip unit that is equipped with longtime, shorttime, and instantaneous functions. In this post i will address some frequently asked questions and misconceptions regarding means for achieving high levels of selective coordination with molded case circuit breakers mccbs q. Why eaton now you can use fuses and circuit breakers. The circuit breaker will open as quickly as possible. A circuit breaker coordination study is used to analyze the tripping times for the series of overcurrent devices being compared, generally from the source through the largest branch circuit device. Selective coordination is often referred to simply as coordination. If a fault above 1500 amperes occurs on the load side of the 90 ampere breaker, both breakers could open. Lv circuit breaker ratings, characteristics, and settings.
Some circuit breaker manufacturers provide tested coordination tables that may be used in place of or in addition to method 2 or 3 above. Designing for circuit breaker instantaneous selectivity robert p. With the national electrical code nec putting greater emphasis on both power continuity and selective coordination, todays engineers. The selective coordination to meet the 2008 nec will only apply to the. What are the requirementsguidelines for coordination. In the uncoordinated system there is overlap of the circuit breaker trip curves, and in some instances the main circuit breaker will trip before the feeder circuit breaker.
Today, more than ever, one of the most important parts of any facility is the electrical distribution system. This paper specifically addresses how to comply with these requirements for lowvoltage circuit breakers. Today, more than ever, one of the most important parts of any facility is the. In the past, prior to the adoption of selective coordination in articles 700 and 701 of the nec, selective coordination was required in nfpa 99 nec 517 systems for ground fault protection for a minimum of 6 cycles. With selective coordination requirements more prevalent in the nec, in recent years.
The 50hp induction motor is the largest horsepower motor of the mcc, and its protection was covered in part 1. Overcurrent coordination page 3 qualtech engineers, inc. What will cause the upstream circuit breaker to open is the peak letthrough current i p of the downstream circuit breaker. Shortcircuit, coordination, and arcflash studies for data centers fig. Understanding time current curves maverick technologies. If the level of selective coordination between the two circuit breakers initially selected is insufficient for the available fault current at that point in the system, the tables may be used to find an alternate upstream circuit breaker that will allow a higher level of coordination. Selective coordination what is selective coordination. Selective coordination is a design requirement added by 2005 national electrical code to article 700 emergency systems see 700. It is used to detect failures and encapsulates the logic of preventing a failure from constantly recurring, during maintenance, temporary external system failure or unexpected system difficulties. Overcurrent coordination setting guidelines conductors. The example on the left lacks breaker coordination. Coordination study goes in hand in had with short circuit study and nec 110.
Our selective coordination lookup tables are quick and easy to use. Timecurrent curves circuit breakers no action to left of curve trip or clear on and to right of curve all devices should be. Selective coordination is a design requirement newly added by both the 2005 and. The selective coordination analysis tool provides you with the ability to select combinations of circuit breakers that provide total selective coordination. Selective coordination requires that only circuit breaker one clear the fault, allowing the other breakers in the switchboard identified as nsg to continue normal operation. Selective coordination tables published by the circuit breaker manufacturer indicate the maximum level of available fault current to which pairs of circuit breakers achieve selective coordination for all values of time even below 0. When a short circuit or overload occurs, upstream breakers are tripped, unnecessarily knocking out circuits and equipment, which also makes it more difficult for maintenance personnel to locate the source of the fault. A feeder supplying a specific fixed motor loads and consisting of conductor sizes based on 430. The use of the term now suggests that only the overcurrent device closest to the fault will open, which will allow other circuits to operate without interruption. As stated in the nec requirements above, selective coordination is not just between the branch circuit. Available fault current selective coordination spreadsheet. Electrical engineers use powertools to perform harmonic analysis, transient stability analysis, short circuit analysis, and to determine demand load, voltage drop, arcflash hazard analysis and protective device coordination. With builtin data for over 2,000 individual devices already builtin, all you have to do is select the devices you want from the list and youre ready to go.
Comply with ansi, nfpa 70e, nema, and nec standards and regulations. Computer analysis using computer software, the system data is input and. The code adds a new definition to article 100 for coordination selective. Circuit breakers database volts electrical design software.
Shortcircuit, coordination, and arcflash studies for. Mar 15, 2016 selective coordination requires that only circuit breaker one clear the fault, allowing the other breakers in the switchboard identified as nsg to continue normal operation. Nothing will stop all activity, paralyze production, inconvenience and disconcert people, and possibly cause a panic, more than a major power failure. They comprise multiple tables for main or upstream and branch breakers. Selective coordination selective coordination cooper bussmann. Now, get the job done in no time with onetouch automation from smartpdc the revolutionary productivity tool from easypower. Shortcircuit, coordination, and arcflash studies for data. Guide to power system selective coordination 600v and below. Selective coordination of lowvoltage circuit breakers.
Selective coordination tools and spreadsheets part three. For consulting and plant engineers, protective device coordination software is absolutely critical for ensuring personnel safety and maximizing system uptime. As can be seen in the figure the available single line to ground fault is about 105% of the available three phase. This is inclusive of its image that is used in volts circuit layout screen and the panel layout report. But tccs dont tell you anything about letthrough current, so in such an instance the coordination tables provided by the circuit breaker manufacturers must be consulted.
The nec speaks about the importance of coordination study in articles 1109, 11010, 240, and 517. Verify equipment duty ratings instantly on the oneline. Etap short circuit software makes it easy to go from selecting elements, from the comprehensive library of short circuit current ratings, to performing dozens of different types of short circuit analysis. Healthcare facilities in nec 2014 have established a different level of coordination from that found in other sections of the nec. Volts circuit breaker database is 100% user defined and allows entry of any type or size of circuit breaker. How to use selective coordination in ptw nec 2005 definition of coordination selective. Ecoord gets the job done right when it comes to analyzing timecurrent curves for overcurrent protection devices. Analyzers, plots and reports allow for quick determination of the worstcase fault current device duty. The curve below shows a 90ampere circuit breaker and an upstream 400ampere circuit breaker with an instantaneous trip setting of 5 5 times 400 a 2000 a.
Ecoord fuse and breaker coordination huge builtin library of devices. The other circuit breakers in the switchgear would not see the fault. Designing for circuit breaker instantaneous selectivity. You overlay the two curves, and you can verify coordination. Selective coordination is required for systems related to life safety as defined in nfpa 70 the nec, and is achieved when an overcurrent on a circuit is interrupted and only the closest upstream device opens such that only the section of the electrical system with a problem is taken offline. Guide to power system selective coordination 600v and below document number 0100db0603 2. In the example on the right with breaker coordination, the breaker. Ecoord fuse and breaker coordination elite software. The curves are a logarithmically graphical representation of the performance characteristics of the devices at a base voltage of 480 volts. For example, if a short circuit occurs on a downstream branch circuit cable as shown in figure 1 below, the branch circuit breaker feeding that cable circuit breaker a should open first to isolate the fault, rather than the main breaker in the panel which would interrupt service to all branch circuits. Selective coordination tools and spreadsheets part two. Other times, the design engineer will use the software with which he or she is. Provides guidance to engineers regarding the national electrical code nec requirements for selective coordination. Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their rating or settings.
For heavily loaded andor long circuits to confirm operation within nec recommendations min skm ptw dapper. Selective coordination time current curve charts electric arc. Home download center electrical software available fault current selective coordination spreadsheet. Ansi shortcircuit short circuit calculation software. Circuit breaker is a design pattern used in modern software development. Generally speaking, it is implemented by means of a dialogue between.
National electrical code nec does allow mv circuit breaker trip settings up to 600% of the ampacity of the conductors. Selective coordination for critical systems per the 2014 nec. This is much larger than the typical 125a to 150a moldedcase circuit breaker used for protection of a 75kva transformer. Circuit breaker and fuse sizing to size circuit breakers and fuses per nec tables, hand calcs x x 60 and 90 conduit filltray size. That has since been removed, and nec 700701 are now recognized by both nfpa 99 and nec 517 as requiring full. Short circuit analysis short circuit software etap.
Selective coordination is required for systems related to life safety as defined in the nec, and is achieved when an overcurrent on a circuit is interrupted and only the closest upstream device opens such that only the section of the electrical system with a problem is taken offline. During the 2011 cycle of the national electrical code nec, a new requirement was introduced pertaining to circuit breakers 1200 amp and above, which was meant to also capture those breakers in a 900a frame that could adjust to 1200a, with noninstantaneous trip. How to achieve selective coordination of circuit breakers eep. Selective coordination what the inspector needs to know iaei. A similar term, coordination, was previously used in 240. The transformers are assumed to be close coupled to the switchgear. Selective coordination requires that only circuit breaker one clear the fault. Although the definition has changed slightly over the years, nec. Available fault current selective coordination siemens. Ratios interactive guide under application info software. Simply match the required main and branch circuit current ratings and select the combination based on the available short circuit current. The minimum instantaneous unlatching current for the 400 a circuit breaker could be as low as 2000 a times. Make sure you specify the correct version or required aic level in the specifications or by schedule. Ge energy industrial solutions ge overcurrent device.
Selective coordination is required for systems related to life safety as defined in the nec, and is achieved when an overcurrent on a circuit is interrupted and. Apr 19, 2011 in order to ensure coordination between, for example, a branch panels feeder breaker on the distribution panel upstream and a branch circuit breaker, all you need to know is the choice of breaker models and their settings. This tool provides circuit breaker selections that are fully rated and fully selective. Data collection information on all the components is obtained during a field visit and from electrical utility and manufacturers, and then tabulated. The proper localization of a fault condition to restrict outages to the equipment affected, accomplished by the choice of selective faultprotective devices. Eaton is the only manufacturer that offers both fuse and circuit breaker solutions. Low voltage breaker fuse coordination requires a minimum 0. Selective coordination with circuit breakers iaei magazine. What are the requirementsguidelines for coordination studies. Frequently asked questions about selective coordination. Where coordination of moldedcase circuit breakers proves to be unwieldy or impossible, there are other options available for selective coordination. This type of coordination is a further evolution of time coordination and can be direct or indirect.
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