Desing and Selectivity LV_GE

8/17/2019 Desing and Selectivity LV_GE

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Guide to Low VoltageSystem

Design and Selectivity


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UnaffectedOpens

imagination at work


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Contents

Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . .1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 National Electric Code

Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

.3 Selective System Design ConsiderationsGround Fault Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .4MCCB Layer Limitations - Riser / Feed Through Lug Panels . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . .5Automatic Transfer Switch (ATS) Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . .7Switchboard Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .7

Transformer / Current Limiting Reactor Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .7

Design Tips Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .7 Selectivity for Existing Systems . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Arc Flash Considerations . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Selective Low Voltage Circuit Breaker Pairings Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . .9 Popular GE Selective Circuit Breaker Pairings - Summary TableGE Circuit Breaker / Equipment Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . .10 AppendixSelective Time Current Curve Templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .1315 kVA with FB Primary & TEY Secondary Mains . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . .1430 kVA with FB Primary & TEY Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . .16

30 kVA with FG Primary & FG Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .18



112.5 kVA with FG Primary & FG Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . .24112.5 kVA with FG Primary & S7 Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .26150 kVA with FG Primary & FG Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .28

150 kVA with S7 Primary & S7 Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .30

225 kVA with FG Primary & S7 Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .32

300 kVA with S7 Primary & S7 Secondary Mains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .34

Typical GE Dry Type, 480 – 120/208V Transformer Impedances . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . .36Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .


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. . . . . . . . . . . . . . .37

Information provided herein may be subject to change without notice. Products in this publication are designed and manufactured in accordance

with applicable industry standards. Proper application and use o f these products is the responsibility of GE's customers or t heir agents inaccordance with the standards to which they were built . GE makes no warranty or guarantee, expressed or implied, beyond those offered in our

standard Terms and Conditions, in effect at the time of sale. Any questions about the information provided in this document s hould be referred to

GE.


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Foreword

GE's first application publication on instantaneous selectivity, GE Overcurrent InstantaneousSelectivity Tables (DET-537, available in the Publications Library at www.geelectrical.com) lists GE low voltage circuit breakers and the short circuit current to which they are selective.

Since that was published, product innovation, rigorous selectivity testing and real-world

experience with selectivity requirements have improved GE's selectivity solutions.

The 2008 National Electric Code® (NEC) included some refinement and additions to theoriginally published “Coordination” requirements for selectivity. While there is still nouniform interpretation of these requirements, many Authorities Having Jurisdiction (AHJs) inthe United States are enforcing instantaneous selectivity requirements for “Emergency” and“Required and Standby” systems. It can be expected that, once an AHJ has accepted these

requirements, they will accept later versions of the NEC articles, including NEC Article 708 – Critical Operations Power Systems.

Following the introduction of coordination requirements in Articles 700 and 701 in the 2005

edition of the NEC, “caution” was the operative word as users, designers and suppliers

adjusted their traditional design and procurement patterns to meet the new NEC selectivityrequirements. Because the regulations are interpreted differently by different AHJs, allinvolved responded to a variety of interpreted requirements. Today, GE will confidently

provide design assistance and selective solution quotations for the majority of customerapplications, regardless of the local AHJ interpretations.

This publication does not replace our original selectivity publication, but provides supplemental

information for those involved in the layout, design and quotation processes. The data inDET-537 continues to be the most comprehensive representation of selective circuit breaker

pairings that GE offers. In this publication, we convey the essentials of selective systemapplications in a more easily used context. When using DET-537, make sure you are using thelatest version available. The most current version can be found on GE's website.

http://www.geelectrical.com/http://www.geelectrical.com/http://www.geelectrical.com/http://www.geelectrical.com/


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IntroductionWhat is selectivity?

The electrical design industry has historically required electrical system circuit breakerselections and settings be validated with a short circuit and coordination study performed by alicensed engineer. These studies assure that circuit breakers are capable of interrupting the

available current and would operate “selectively.” Traditionally, “selectivity” in a low voltageelectrical system meant that the long time and short time portions of time-current curves (TCCs)

would be selective, i.e. the circuit breaker closest to the fault would trip first, maximizing theamount of the electrical distribution system left in service. In most cases, the circuit breaker

instantaneous overcurrent (IOC) TCCs would not be selective “on paper,” as they typicallyoverlap.

In Figure 1A, there is no “instantaneous selectivity” apparent on the TCC, as the instantaneous portion (below 0.1 seconds) of the curves show all three breaker characteristics overlapping.The long time and short time characteristics (above 0.1 seconds) do not overlap and are

therefore selective. In Figure 1B, the 1600 amp AKR and Spectra F200 circuit breakers areselective, as the instantaneous function of the AKR is not used, so there is no overlap of these

two characteristics.

Traditionally, selectivity between molded case circuit breakers (MCCBs) and insulated casecircuit breakers (ICCBs) was considered effective, even if there was an overlap of TCCs in theinstantaneous region. The most prevalent type of fault, the line to ground arcing fault, oftenlimits the fault current magnitude enough that the upstream circuit breaker IOC function does

not operate. If the fault is removed promptly, the likelihood of it escalating into a multi-phase, bolted type fault is very low. As a result, for a large majority of faults, the traditional long time,short time selectivity has been sufficient to produce selective operation of circuit breakers.

The 2005 and 2008 NEC extend the selectivity requirement to all possible fault types andmagnitudes for certain critical electrical circuits, i.e., those typically fed from automatictransfer switches (ATS). These circuits and requirements are those discussed in the following

NEC articles:Article 700: Emergency Systems (Legally Required), 700.28 Coordination

Article 701: Legally Required Standby Systems, 701.17 CoordinationArticle 708: Critical Operations Power Systems, 708.54 Coordination

CURRENT IN AMPERES CURRENT IN AMPERES


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10000.100.011001011Spectra F 200AA P TEY

TCCs are “selective” TCCs are not “selective” 1K 10K 100KSK 1000ATIME IN SECONDS1 10 100 1K 10K 100K10000.100.01100101Spectra F 200A20A 1P TEY

TCCs are “selective” 000/1600A AKRTIME IN SECONDS


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Curve 5.tcc Ref. Voltage: 480 Current Scale x10^0 Curve 5.tcc Ref. Voltage: 480 Current Scale x10^0

Figure 1A Figure 1B


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These requirements state that overcurrent protective devices (OCPD) must be “fully selective.”In other words, given the range of available interrupting currents, any given pair of overcurrent

devices covered by the NEC Articles referenced above must behave in a coordinated fashion asdefined in NEC Article 100:

“Coordination (Selective). Localization of an overcurrent condition to restrictoutages to the circuit or equipment affected, accomplished by the choice ofovercurrent protective devices and their r atings or settings.”

The NEC requirements are desirable design goals, given the adverse consequences of largerthan necessary power outages within critical circuits. However, there are other design

considerations that these requirements seem to preclude, i.e., arc flash and the specifics of phase and ground fault overcurrent coordination. The ability of fully selective designs to provide sufficient protection to such important, sensitive equipment as generators or automatic

transfer switches may be affected.

This publication uses the information on instantaneously selective breaker pairings contained

in DET-537 as a base, and goes on to discuss specific tactics for developing fully selectiveelectrical distribution designs. Though instantaneous selectivity is possible in many cases, it is

not always easily accomplished with the considerations mentioned above. It has long been theresponsibility of the licensed engineer of record to assess all performance requirements and

produce a balanced, practical design.

National Electric Code (NEC) Requirements

The 2008 NEC Articles 700.27, 701.18 and 708.54 requirements for Coordination say:

“... overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.”

This wording does not exempt ground fault protection from selectivity, nor does it exempt

selectivity with the normal side supply sources. Even though this requirement is found in theSpecial Conditions chapter of the NEC dealing with Emergency Systems, Legally Required

Systems and Critical Operations Power Systems (COPS), it states the emergency overcurrent

protective devices must be selectively coordinated with all supply side overcurrent

protective devices. This terminology implies that selectivity with both normal and emergencysupply sources is required for both phase and ground fault OCPDs. (Note: The local AHJ has

the final word on interpretation of the NEC and other applicable code language. It isimportant to use their interpretation when designing and quoting selective systems.) Fullselective coordination in systems with ground fault protection can be difficult and is beyondthe intended scope of this publication.

To date, a large variety of interpretations of the NEC requirements have been made. Numerous

state and local AHJs have excluded these “Coordination” requirements from their enforcementcodes, or have modified them. At the time this publication was written, the most mentionedalternative to the NEC “full selectivity” requirements is the “0.1 second rule.” This definition

of selectivity has been adopted by some AHJs, including, most notably, Florida's Agency forHealth Care Administration (AHCA). This selectivity requirement preceded the 2005 NEC

requirements by decades.

The AHCA requirements are broader than those in the NEC as they apply to the entire facility,not just critical circuits. Therefore, faults on non-critical portions of the system will not result in


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an unwanted shutdown of critical circuits because of non-selective breaker operations. Thisstandard is often criticized because it only requires selectivity down to 0.1 seconds. However, it

represents the long-standing design practices employed be electrical systems designers. TheAHCA requirements, which allow the overlap of OCPD IOC functions, result in reducedclearing times and associated arc flash hazards and require selective coordination for the entirefacility.

The AHCA 0.1 second allowance does have sound engineering basis. It is probable that most

system faults are line to ground arcing faults on branch circuits. These faults will probably fall beneath the IOC threshold of the larger circuit breakers above the branch circuit breaker

nearest the fault. Ground faults in parts of a system with high short circuit currents may bequite high in magnitude. Sensitive ground fault protection is often sufficient to sense and cleararcing ground faults well below IOC levels of upstream devices. Two levels of selective

ground fault protection have been required in certain hospital systems by NEC Article 517 formany years.

It is important to note that “full selectivity” is often facilitated by increasing trip time delaysand increasing pickup thresholds in upper tier OCPDs. Allowing instantaneous protection to be

applied throughout the system improves protection and decreases arc flash hazard. The impactof designing for full selectivity in systems that require “live work” should be studied andunderstood so optimized design decisions can be made and hazards identified.


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The first words of NEC, Article 90.1, Purpose, are: “(A) Practical Safeguarding. The purpose

of this Code is the practical safeguarding of persons and property from hazards arising from

the use of electricity.” Historically, the NEC started by establishing protection requirements forlow voltage loads, cables, transformers, etc. This has always been and continues to be the

Code's first priority. While Articles requiring “fully selective” systems are consistent with the“Practical Safeguarding” requirements, these Articles do not take precedence over competing

protection and design needs.

In the absence of specific language in NEC Articles 700, 701 and 708 for coordination,interpretations of the NEC code vary significantly. Some interpretations require full selectivity

through the critical circuits, to both the normal and emergency supplies. Others require criticalcircuit breakers to be selective to the automatic transfer switch (ATS) using the normal supply

short circuit current, then continue the selectivity only to the emergency supply above the ATSusing the emergency source short circuit current. A third popular interpretation requires

selectivity through critical circuits to the emergency supply only. (Please note that the shortcircuit current from the emergency source is often much less in magnitude than the normalsupply.) Where this is the case, designers have more selective breaker pair choices and the

potential ability to reduce the size and cost of a selective system solution.

Some AHJ's and the State of Massachusetts require selectivity of critical circuits to beaddressed, but leaves the extent of the requirement to the discretion of the licensed professionalengineer of record. This allows the engineer to balance other design requirements, such as arcflash, with selectivity needs.

When designing a system for selectivity per NEC requirements, it is important to knowexactly how the AHJ has defined selectivity requirements and how they are verified and

enforced.

Selective System Design Considerations

Ground Fault Protection

Some selectivity requirement interpretations of the Code exclude ground fault

protection because it is not specifically addressed in Article 700, 701 or 708. Article 100

defines “Coordination” as:

“Localization of an overcurrent condition to restrict outages to the circuit orequipment affected, accomplished by the choice of overcurrent protective devicesand their ratings or settings.”

“Overcurrent” is defined as:

“Any current in excess of the rated current of equipment or the ampacity of aconductor. It may result from overload, short circuit, or ground fault.”

Even though ground fault selectivity is not expressly mentioned in Articles 700, 701, and 708,it is implied through the overriding NEC definitions of “selectivity” and “overcurrent.”

Traditionally, the shape of a ground fault protection characteristic applied on low voltagecircuit breakers would be called a “definite time” or “L-shaped” characteristic. (Note: Often,ground fault relays or ground fault protection integrated with circuit breaker trips will offer a

way to cut off the bottom left corner of the “L.” This cut -off corner is usually in the shape ofan I2t=K diagonal line on the TCC.)


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Typical GF protection characteristics are illustrated in the low voltage circuit breaker phase andground protection characteristics below. Their dissimilar shapes make selective coordination

difficult at best. The NEC (Article 230.95) requires thatground fault protection be applied on solidly grounded 480 volt service entrances, 1000amperes and larger.

Hospitals and other healthcare facilities with critical care or life support equipment arerequired to have a second level of ground fault protection beneath the service entrance (NEC

Article 517.17(B)). The NEC-stipulated maximum ground fault pick-up setting is 1200amperes and clearing time is limited by a requirement that a 3000A fault must be cleared in

one second or less (Article 230.95(A)). Emergency system supply sources are exempted fromthese requirements.


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Figure 2A is a one line diagram with two levels of ground fault protection as required by NECArticle 517. Figure 2B diagrams the selective device settings for this one-line diagram. Ground

fault relay settings for the 4000A main and 1200A branch feeder are selective and at themaximum allowed by the NEC. The next device below the 1200A branch is a 250A OCPD.

Note that there is significant overlap between the ground fault relays and the 250A deviceTCCs.

Traditional system designs would size the 250A OCPD to 600A or possibly 800A, making this

non-selective situation worse. In this and many similar situations involving phase and groundfault protection, this system would not be fully selective for ground faults, as an upstreamOCPD could trip sooner than the downstream OCPD.

MCCB Layer Limitations - Riser / Feed Through Lug PanelsSome traditional electrical system designs have utilized a “waterfall” of electrical distribution

panels of declining ampacities, i.e., a series of progressively smaller electrical distribution panels connected to larger upstream panels. This concept is popular because it allows the size

and cost of the distribution panels and feeder cables to be reduced further from the serviceentrance point. While this has been a satisfactory practice when long time and short timeselectivity is considered, the practice increases the difficulty of achieving “fully selective”solutions.

For “fully selective” designs, it is desirable to limit the number of selective circuit breakerlayers as there are a limited number of selective molded case circuit breaker (MCCB) pairingsavailable. If you consult GE's (or other manufacturers') circuit breaker instantaneous selectivitytables, you will usually find three or, in some circumstances, four layers of molded case circuit

breakers that can be made fully selective.

With a limited number of fully selective MCCB layers in mind, the best electrical distribution

design strategy is to limit the number of selective layers by utilizing feed-through lugs or riser panels of the same ampacity when sub-panels are required. When feeder cables and panels areall the same ampacity, only one layer of protection is required to protect them.

In doing so, the tradeoff is the elimination of a local main circuit breaker. Some designs willutilize a main disconnect at each panel to allow local isolation of a panel. Care must be

exercised if a molded case switch (MCS) is used as a main disconnect. The MCS will have anIOC override in the switch to protect it from damage resulting from high magnitude fault

currents. This instantaneous override must be considered as part of the selectively coordinatedsystem.

CURRENT IN AMPERES


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10000.100.0110010

Swbd feed14000A250 RK5

120020A TEY20A JMain GF Aer GFTIME IN SECONDS

4000AGF GF

1200AGF GF

20A250A


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10 100 1K 10K 100K


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1600A.tcc Ref. Voltage: 480 Current Scalex10^0

Figure 2A Figure 2B


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In Figure 3, the 400 ampere feeder is feeding three downstream panels. With the use of riser panels of the same ampacity, only two layers of selective breakers would be needed. If a

traditional design strategy of progressively smaller sub-panels had been used, four layers offully selective circuit breakers would be required for the waterfall of declining ampacities.

Fully Selective

Circuit Breaker

Options For

Systems with 65

kAI C or less

SOURCE

480V

LVPCB w/o instantaneous

LEG REQD ATS-1**

30-300 KVA

208V

FG

LIGHTING PANEL

FB*

65 kAIC maximum

MAIN SWBD

S7 - ICCB or MCCB req'd to protect 3cy ATS rating

MLO PANEL

FG or FB set to protect xfmr

FG600 600 AT Max

FG600

400 AT

PNL

PNL

PNL-2PNL-3

PNL

PNL-1

MLO w/ FTL or Riser panels, all equally rated w/ FB* branch breakers

* TEY or THQ MCCBs may be used, but only if the maximum AIC

specified in DET-537 is not exceeded. ** See selectivty templates

for details of transformer

Figure 3


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Automatic Transfer Switch (ATS) Protection

Most ATSs built for use in North America are manufactured in accordance with the UL 1008standard, which references UL 489 for molded case circuit breakers. Furthermore, many ATS

manufacturers provide application data specifying which MCCBs are appropriate for protecting the ATS ampacity and short circuit withstand ratings. In general, most ATSs aredesigned to be protected with circuit breakers that have integral IOC protection functions.

In some fully selective protection schemes, it may be necessary to protect an ATS with a lowvoltage power circuit breaker (LVPCB) applied without an IOC function. This may be anon-conforming application, which might require special consideration by the ATSmanufacturer. Some ATS manufacturers have published withstand data on such applications,

while others are considering future products with higher withstand time ratings in view of thenew selectivity requirements.

Switchboard Protection

Switchboards, distribution panels and lighting panels utilize MCCBs, ICCBs or LVPCBs withIOC functions. Therefore, the withstand ratings of these boards and panels are usually based on3 cycles. Similar to the ATS ratings discussed above, LVPCBs without an IOC function should

not be used to protect a switchboard unless special application consideration has been given toits withstand rating. Some manufacturers have 30 cycle withstand ratings for specificswitchboard designs. If selectivity requirements result in the use of LVPCBs without an IOCfunction or very high IOC settings, it is important to know the withstand ratings of thedownstream equipment.

GE has introduced UL Listed Spectra Series Switchboards rated for 30 cycles of short circuit

withstand. Since UL 891 does not have standard requirements for 30 cycle ratings, ANSI 37.20was used to validate the switchboard performance. These switchboard designs enable them towithstand longer duration faults.

Transformer / Current Limiting Reactor Applications

Considerations for NEC “fully selective” applications focus on the selective performance ofcircuit breaker pairs in the IOC regions of their TCCs. Usually, higher short circuit currentslimit the options for pairs of selective breakers. Consequently, some electrical designs useone-to-one ratio transformers or current limiting reactors to restrict fault current magnitudes.

This works well where one of these devices can provide a small amount of series reactance tocontrol the short circuit current to a magnitude where more options for selective breaker

pairings are available. It may not be effective if two-to-one or three-to-one reductions in shortcircuit current magnitude would be required to make selectivity possible.

Design Tips Summary

Note the actual calculated short circuit currents for the critical circuit buses on the bid drawings.Define the circuits and sources that must be made selective, according to the local AHJ

(preferable), the end customer or the engineer of record.

Limit service entrance short circuit current to less than 65 kA whenever possible.Limit the “critical” feeder sizes in the service entrance gear to 1200A maximum. Limit the number of MCCB selective layers below an ATS to two if using a 1200A frame

MCCB to protect the ATS.If ATS or switchboards are protected by an LVPCB without IOC, this equipment will

require a 30 cycle short circuit withstand rating.

Utilize main lug only (MLO) with FTL or riser panels to minimize required layers of fullyselective circuit breakers.


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Increasing the frame size of an ICCB or MCCB may increase maximum short circuit currentselectivity with a downstream breaker.

Small lighting transformer impedance can be used to limit the secondary short circuit current,with resulting full selectivity (secondary main IOC set above the secondary short circuitcurrent).

For systems with 35kA short circuit current or less:

– Utilize an LVPCB without IOC as the service entrance main as the fifth andtop layer of selective protection. – Utilize PB II as the fourth layer of selective

protection. – Utilize S7 MCCB as the third layer of selective protection. – Utilize FG MCCB as the second layer of selective protection. – Utilize FB, TEY, THQB MCCBs (depending on short circuit current requirement and

voltage at this level) as the bottom branch device layer of selective protection system.For systems with 65kA short circuit current or less,

– Utilize an LVPCB without IOC as the service entrance main as the fifth andtop layer of selective protection. – Utilize an LVPCB without IOC as the fourth

layer of selective protection. – Utilize S7 MCCB as the third layer of selective protection.

– Utilize FG MCCB as the second layer of selective protection. – Utilize FB, TEY, THQB MCCBs (depending on short circuit current requirement and

voltage at this level) as the bottom branch device layer of selective protection system.

Utilize lighting transformer TCC templates to define breaker applications for transformer protection and fully selective protection.Contact GE Specification Engineers in Florida for assistance with 0.1 second selectivity

requirements.


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Selectivity for Existing Systems

Several projects have been reviewed where NEC requirements for selectivity on criticalcircuits have been stipulated for add-on systems within pre-existing power distributionsystems. Interpretations of requirements for these situations have varied significantly.

Assuming that the critical circuits in the original system were designed to the “traditional”selective coordination requirements, adding new critical circuits under the existing system

would probably result in a non-selective system. Under fault conditions in the new portion ofthe circuit, the upstream, pre-existing breakers would probably be non-selective, resulting in a

potential shutdown of the entire new system for some faults. Where devices with instantaneous

trips from different manufacturers are mixed, it is unlikely that there is enough data todetermine the selectivity capability between them. The one application

exception to this would be the addition of a new sub-system under an ANSI circuit breakerthat was applied without an IOC function or a circuit breaker with an IOC threshold largerthan the AIC.

In some cases, a variance from the Code requirement has been requested and granted based onconsiderations of the difficulty in analyzing or achieving selectivity for systems involving a

mix of manufacturers. If absolute adherence to the new NEC requirements for add-on systemsis required, this will probably result in costly replacement of existing circuit breakers and

possibly equipment. Often, fully selective circuit breaker pairings and associated equipmentmay be larger and more expensive than breakers and equipment designed around traditionalselectivity definitions. Therefore, an expansion of the space allocated to original equipment

may be required.

Arc Flash Considerations

At the core of fully selective designs based on NEC Coordination (fully selective) requirements

is the concept of coordination of circuit breaker OCPD time-current characteristics. Practically,this means that the circuit breaker immediately upstream of the breaker closest to the fault will

be set (delayed or desensitized) to prevent it from operating until the downstream breaker clearsthe fault.

Considering that a typical 1500 kVA service entrance and associated power distributionsystem designed for full selectivity may have five layers of coordinated circuit breakers, the

time delayed response of the service entrance main breaker may be considerable. This timedelay could correspond to high arc flash incident energy and a correspondingly high HazardRisk category classification.

The Standard for Electrical Safety in the Workplace, NFPA70E, requires that all electricalhazards be identified by qualified personnel before work on electrical equipment is

undertaken. Usually, this requires assessment of arc flash hazard. Ideally, an Arc Flash Studyof the electrical system should be considered during design so that the consequences of design

decisions, including those made for selectivity purposes, are understood.

Increasing OCPD pickup settings, increasing IOC settings and adding time delays to obtainsfully selective design can have a significant impact on available incident energy. For systemslikely to be serviced while energized, these time delays may cause serious risk to personnel.

High incident energy levels may force the system to be shut down before any work can be


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performed. Additionally, excessive energy levels and time delayed (slow) protective deviceresponse may allow extensive fault related damage, requiring extensive down time and repair.


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THQ 35-60A

Selective Low Voltage Circuit Breakers Pairing Diagram-P2,3

4kATHQ 15-30-P2,36kATHQ 15-30A-P114kATEYF 15-30A-P1,2,314kAFE 250A-PTEY 15-30A2,3-PFE 250AFE 250A-P-P14.21,2,32,3

2,3 100kA10kA65kA

Maximum Short Drag Rating for CBs Listed Below

100kA 65kA 200kA 150kA 65kA 200kA 200kA 100kA 65kA 10kA 22kA208VFB 15-100

FB 15-100A1,2,3-P

-PFE 25-150A1,2,3

35.0kA

100kA 65kA150kA 100kA 65kA200kA 100kA 100kA 14kASF 250A

2,3-P-P2,3-P 2,3-P430V

2,310kA 10kA 22kA 22kA 2.5kA 2.5kA 2.5kA 14kA 14kA 65kA65kA 100kA65kA 65kAFrame Range500-3200A2000-800A4000-3000A 2000-800A1200-1000A 600-250A600-150A

100A 100A 125A 125AFE 250AFE 250A-P-P

All Other MCCB's 800A and Less2,3 71.3kA2,3 100kA

-PTEY 15-30A

1-PSE 150

2,3 12.8kA1-P 1,2,3-P 1,2,3-P 1-P

1,2,3-P 1,2,3-P 1-P 1,2,3-PFB 100A 1,2,3-PSE 150A1,2,3-P 1,2,3-P 1,2,3-P800A

Wave Pro Wave Pro PE111PE11157FG 599SE, SF, SGFBTEY THQ THHQPB2,WP, ENTELLIGUARD

(w/ INST.)TypeS7 1000/1200A-PTEYF 15-100A

SK w/MVT orMET 1200A

2,3-P1,2,3TEYF 15-100A10.8kA-PTHQ 15-100A3-P1,2,3

FB 100A 1,2,3-PTHQ 100A1,2,3-P 1,2,3-P 1,2,3-P-P27kA14kA21.6kA

1,2,322kA6kA 10kA 10kA 14kA 22kA65kA100kA15-100A1,2,3-P

SG w/MVT orMET 600A

2,3-PSF 250ATEY 70-100A-PFB 15-100A

All Other MCCB's 400A and Less


26/105

TEY/THQ2,3 40.0kA

TEY 15-30A28.3kATHQ 100A10.8kA1-P 1,2,3-P-P

1,2,365kA22kAFG 250-400A-P-P-PTEY 35-60ASE 150TEY 15-100ASE 150-P

2,3 40kATEY 15-30ATEY 35-60A

2,3 71.2kA2,3 10.8kA

1600A2,3-P 1-P1,2,32,3-P 1-P 1,2,3-P1,2,3-P 1-P-P5.4kA

1,2,3PB2,WP, ENTELLIGUARD 3200-5000A14kA14kAPB2,WP, ENTELLIGUARD(w/ INST.)FG 250-600(WITHOUT INST.)-P-PTEY 35-60ATEYF 15-100ASF 250TEY 35-60ATEY 35-60A2,3

2,3 25kA67.4kA-P

1,2,3100kA14kA10kA 10kA57 1000/1200AFG 250-600A2,3-P 3-P

3-PTHQ 15-30ATEY 70-100ATEY 35-60A-P-P-P27kA2,3

1,2,32,365kAFG 600ATHQ 15-30ATEY 70-100ATEYF 15-100A

1-P 1-P

1-P44.0kA2000A-P-P

1,2,31,2,314kA4kAPB2,WP, ENTELLIGUARD

(w/ INST.)FG 400A-PTHQ 35-60ATEYF 15-100A2,32,3-P 1-P44.0kA-P

1,2,314kA100kAFG 250A-PTHQ 35-60A

2,3 44.0kA

THQ 70-100A

-P1,2,32.5kA

Figure 4


27/105

Maximum AIC Ratings for Popular, Fully Selective Circuit Breaker Pairs

Instantaneous selectivity AIC values in these tables are for 277/480V and 120/208V ratings.THQB breakers listed are rated for 120/208V. SF, SE, FB, TEY and THQB breakers will

probably not be selective with any breakers applied downstream from them.


28/105

TCC

Table 1A

Selectivity to be determined via TCC overlay method using

specific OCPD settings Selectivity probably not achievable

Main

Breaker

Bra

nch

Brea

ker

(ABB) S7H

** Record Plus

FG

Spec

tra

SF

Spect

ra

SE

Recor

d

Plus

FE

Recor

d

Plus

FB

Fra

me

TE

YF

No.

Poles3 3

3,2 3,2 3,2 3,23,2

3,23,2,1 3,2,1

Max

Sensor

or Trip*

12

001000

600 400 250 250

150

250

100 30

WavePro

(LSTrip)

5000 65.0

65.0

100.0

100.0 100.0 100.0

100.0

100.0

100.0 14.0

4000 65.0 65.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 14.0

3200 65.0 65.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 14.0

2000 65.0 65.0 65.0 65.0 65.0 65.0 65.0 65.0 65.0 14.0

1600 65.0 65.0 65.0 65.0 65.0 65.0 65.0 65.0 65.0 14.0

800 NIS 65.0 65.0 65.0 65.0 65.0 65.0 14.0

WavePro(LSI

Trip)

5000 31.5

31.5

64.7

64.7 64.7 97.5

100.0

100.0

100.0 14.0

4000 32.4 32.4 69.0 69.0 69.0 100.0 100.0 100.0 100.0 14.0

3200 37.437.4

100.0100.0 100.0 100.0

100.0100.0

100.0 14.02000 27.0 27.0 44.0 44.0 44.0 67.4 71.2 100.0 100.0 14.0

1600 21.6 21.6 25.0 25.0 25.0 40.0 40.0 71.3 100.0 14.0

800 NIS 11.0 11.0 11.0 13.0 14.2 35.0 14.0

PowerBreak II

4000 32.432.4

69.069.0 69.0 100.0

100.0100.0

100.0 14.0

3000 35.1 35.1 85.0 85.0 85.0 100.0 100.0 100.0 100.0 14.0

2500 29.3 29.3 54.0 54.0 54.0 81.6 90.0 100.0 100.0 14.0

2000 27.0 27.0 44.0 44.0 44.0 67.4 73.0 100.0 100.0 14.0

1600 21.6 21.6 25.0 25.0 25.0 40.0 40.0 71.3 100.0 14.0

800 11.0 11.0 11.0 13.0 14.2 35.0 14.0

S7H (ABB) 1200 65.0 65.0 65.0 65.0 65.0 65.0 14.0

1000 65.0 65.0 65.0 65.0 65.0 65.0 14.0Record PlusFG

600 TCCTCC

TCC100.0

65.0 14.0

400 TCC TCC TCC TCC 65.0 14.0

250TCC TCC TCC 65.0 14.0

14.0

Record PlusFE

250


29/105

* For Record Plus FG & FE and ABB

S7, maximum IOC is based on sensorsize

** S7 LTPU is 0.4-1.0 x sensor size

and does not use rating plugs


30/105

Table 1B

Main

Breaker

Branc

h

Break

er

Frame TEY Q-Line THQB

No. Poles 3,2 1 3,2 1 3,2 1 2 3, 2 3, 2, 1 3 1

Max

Sensor orTrip

100

100

60 60

30 30

125 100

60 30

30

WavePro(LS

Trip)

5000 14.0

14.0

14.0 14.0 14.0

14.0

22.0 22.0

22.0 22.0

22.0

4000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

3200 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

2000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

1600 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

800 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

Wave

Pro

(LSITrip)

5000 14.0

14.0

14.0 14.0 14.0

14.0

22.0 22.0

22.0 22.0

22.0

4000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

3200 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

2000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

1600 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

800 12.8 12.8 12.8 12.8 12.8 12.8 18.1 18.1 18.1 18.1 18.1

Power BreakII

4000 14.014.0

14.0 14.0 14.014.0

22.0 22.022.0 22.0

22.0

3000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

2500 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

2000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

1600 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0800 12.8 12.8 12.8 12.8 12.8 12.8 18.1 18.1 18.1 18.1 18.1

S7H (ABB) 1200 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

1000 14.0 14.0 14.0 14.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

Record PlusFG

600 6.06.0

10.0 10.0 14.014.0

22.0 22.022.0 22.0

22.0

400 4.0 4.0 10.0 10.0 14.0 14.0 22.0 22.0 22.0 22.0 22.0

250 2.5 2.5 2.5 2.5 14.0 14.0 2.5 2.5 10.0 22.0 22.0

Record PlusFE

250 TCCTCC

TCC TCC 10.010.0

TCC TCC4.0 6.0

14.0

Table 1C

120/240V breaker ratingsFor 120/240V breaker pairs not listed below, use selective values from the

208 & 480V table above.

Main

Breaker

Bran

ch

Brea

ker

Record Plus FG

Spect

ra

SF

Spect

ra

SE

Recor

d

Plus

FB

No. Poles 3,2 3,2 3,2 3,2 3,2 3,2,1

Max 600 400 250 250 150 100


31/105

Sensor

or Trip

WavePro(LSI

Trip)

5000 130

130

130

130

130

100

4000 130 130 130 130 130 100

3200 130 130 130 130 130 100

2000 130 65 65 130 130 65

1600 130 65 65 130 130 65

800 TCC 10 10 130 130 65

Power Break

II4000 100

100100

100100

100

3000 100 100 100 100 100 100

2500 92 92 92 100 100 100

2000 75 75 75 85 85 85

1600 42 42 42 72 72 85

800 TCC 10 10 14 17 32


32/105

Table 2

GE Circuit Breaker / Equipment Combinations

Breakers Equipment

Enclos

ure

Mount

ed

A-Series II

PanelboardsA-Series

II

Powerpa

nel

Spectra

Powerpan

els

Switchboard

sSwitchgear

A

Q

A

E

A

D

AV-1,

2,5

AV

-3

PB

II

AKD

10

Entellis

ys

AKD

20

Mai

n

WavePro without

IOC

WavePro with

IOC

EntelliGuard

without IOC

EntelliGuard with

IOC

EntelliGuard G

without IOC

EntelliGuard Gwith IOC

Power Break II

ABB S7

Record Plus FG8/0

8

Record Plus FE200

9

200

9

Feed

er

WavePro without

IOC

WavePro with

IOC

EntelliGuardwithout IOC

EntelliGuard with

IOC

EntelliGuard G

without IOC

EntelliGuard G

with IOC

Power Break II

ABB S7 ABB

Record Plus FG

Record Plus FE 2009 8/08

Record Plus FB 3 8/08

TEY / TEYF 3

THQ 3


33/105

Appendix

Selective Time– Current Curve TemplatesThe followed time-current curves were composed with the following objectives:

1. Achieve full selectivity (LT, ST and IOC) between each pair of circuit breakersapplied

2. Provide required NEC transformer protection3. Provide recommended ANSI through fault protection of transformers4. Provide the secondary power panel protection in accordance with its ampacity

(Note: To be “fully selective,” there must be no overlap of the long time and short timecharacteristics of an upstream and downstream circuit breaker pair. If the IOC function of this

pair of breakers overlap, then their instantaneous selectivity must be identified as selective in

the manufacturer's instantaneous overcurrent selectivity application literature.)

While it may be desirable to have the primary and secondary main circuit breakers selectivewith one another, it is not usual when applying MCCBs to protect transformers. In the 2008

NEC, a specific exception was added to exempt selectivity requirements from the primary and

secondary mains. The branch circuit breakers shown are the largest possible breakers and tripsthat will be fully selective with both the upstream primary and secondary main transformercircuit breakers. If selectivity between the branch breakers and the upstream secondary main isnot apparent because of IOC TCC overlap, the application is fully selective based on the

tabular pairing cited in DET-537, GE Overcurrent Device Instantaneous Selectivity Tables.

One other item of note is that the maximum AIC values shown in DET-537 are symmetrical

values. All analysis and testing done to validate these numbers were done with the appropriatestandard based X/R value and corresponding asymmetrical offset. The equivalent symmetricalvalue was placed in the tables. It has long been standard practice to terminate the IOC functionon a TCC at the maximum asymmetrical value of fault current, as IOC functions are oftenresponsive to the peak value of current.

The partial system templates diagrammed on the following TCCs were laid out and modeled based on a maximum fault current of 65 kA at 480V, with an X/R ratio of 4.9. Transformerimpedances used are the minimum for which a full selectivity solution could be achieved. Also

noted on the TCCs are the typical GE transformer impedances for aluminum wound, 150°Crated transformers. In every case, the impedance diagrammed is equal to or less than thetypical GE value. To make the solution as conservative as possible, no or negligible cableimpedances were included in the short circuit calculations.

While Article 450 of the NEC requires that transformers be properly protected fromovercurrent conditions, it allows several alternative approaches to achieve protection. For480V to 120/208V lighting transformers, 15 kVA and larger, the protection requirements are

described in Table 450.3B of the NEC. The two options described are to use a circuit breaker

as the primary main rated at no more than 250% of the primary ampere rating and a secondarymain circuit breaker rated at no more than 125% of the secondary. (Note: See NEC Table450.3 and associated notes for additional application allowances and restrictions.) It is also

permissible to use only a primary main circuit breaker rated at no more than 125% of the

primary ampacity.

In general, since the ANSI “through” fault protection criteria is a recommendation, it is

desirable to have the ANSI protection characteristic to the right of the primary and secondarycircuit breaker TCCs. However, it is the standard practice that adequate protection is still


34/105

provided if most of the ANSI characteristic is to the right of the secondary main TCC.

In the TCCs that follow, A is always the transformer primary main and B is the secondary main

circuit breaker.


35/105

A

B

C

480V

BUS-115 KVA

3.5%

65 KAIC (SYM)

A

B C*

208V

BUS-2

GE Record Plus MCCB Frame Type: FBN Frame Size: 100A Trip: 25A

GE TEY MCCB

Frame Type: TEY Frame Size: 100A Trip: 50A

* GE Q-Line MCCB Frame Type: THQB Frame Size: 100A Trip: 20A


36/105

Notes:

Where an overlap of the time-current curve, instantaneous overcurrent characteristics seem to indicate

non-selectivity, GE Overcurrent Instantaneous Selectivity Tables, DET-537, were used to validate

selective operation.

Unless otherwise noted, overcurrent protective devices shown are for all available pole

configurations.

GE typical transformer impedance: 150°C rise, aluminum winding, Z = 6.1%

This Z% is equal to or greater than the minimum allowed on this coordination plot

* Base layer circuit breaker settings are “not to exceed” values


37/105

15.6.81234678

9102346789100234678910002346789

10000.55555

Time-current CurveFully Selective Solution for 15 kVA TransformerCURRENT IN AMPERES X 10 AT 208 VOLTS8007001000 1000900 900600500400300200100908070605040302010 987654321.9.8.7.6.5.4.3

.2.1

.09

.08

.07

.06

.05

.04

.03

.02

.01 .01TIME IN SECONDS

K

V


38/105

A

15

F

L

A

AGE

Re

cor

d

P

l

u

s

F

B

N

T

ri

p

Fr

a

m

e

=

=

10

0A25

A

15

KVA

3.5%

C

*

GETHQ

Q

Li

ne


39/105

B

Fr

a

m

e

Tr

ip

=

20

A

=

10

0A

B GE

E1

50

T

E

Y

T

ri

p

Fr

a

m

e

=

5

0

A

=

1

0

0

A

1

5

K V

A

I

N

R

U

S

H

B12

17

A

8007001

0090

600


40/105

50040030020080706050403020

10 98765432

1.9

.8

.7

.6

.5

.4

.3

.2.1

.09.08.07.06

.05.04

.03

.02TIME IN SECONDS

The following parameters are the basis of the above selective coordination plot:Minimum allowable Z% = 3.5%65 kA (X/R=4.9) @ 480V; 1.2 kA @ 208V


41/105

B

C

A

D

BUS-1

480V

65 KAIC (SYM)

A

30 KVA 4%

B 208V

BUS-2

C* D*GE Record Plus MCCB Frame Type: FBN Frame Size: 100A Trip Plug: 70A

GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 250A

Rating Plug: 100AIOC Setting: 11X (2750A)

* GE Q-Line MCCB

Frame Type: THQB Model C Frame Size: 100A-1,2P Trip: 50A



42/105

Notes:





configurations.





43/105

CURRENT IN AMPERES X 10 AT 208 VOLTS23456789

100234.5.6.81234567891056789

10002345678910000

Time-current CurveFully Selective Solution for 30 kVA Transformer.5.8123468

1023467910034678100023467910000.6

579585958800800700700

30 KVA FLA600


44/105

600500500

BG

400400

E RecordPlus300300

200200

Trip =

100A

Inst = 11X (27

50A)1

0090

100908080707060605050

30 KVA4040

4%3030202010

910 98877665544332

21.9

1.9.8.8.7.7

Trip =

35A.6.6.5.5.4.4.3.3.2.2

C *30 KVA INRUSH

.1.09

.1

.09

.08

.08

.07

.07

Trip = 50A.06.06.05.05.04


45/105

.04

.03

.03

.02

.02

B

2126ATIME IN SECONDS

1000 10900 900.01 .01

GE Q LineTHQB Model C - 1,2P Frame = 100A

D *

GE Q Line THQB

Frame = 100A

FGN

Frame = 250A

A

GE Record Plus FBN

Frame = 100A Trip = 70ACURRENT IN AMPERES X 10 AT 208 VOLTS


TIME IN SECONDS


46/105

BUS-1

BUS-2

B 208V

65 KA (SYM)

480V

A

30 KVA 4%

A

B

C


47/105

D

GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 250ARating Plug: 100AIOC Setting: 11X (2750A)

GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 250ARating Plug: 100AIOC Setting: 11X (2750A)


* GE Q-Line MCCB

Frame Type: THQB Model C Frame Size: 100A - 1, 2P Trip: 60A


48/105

C* D*


49/105

Notes:





configurations.





50/105

19.5.6.812345

6789102345678910023467891000

2345678910000

Time-current CurveFully Selective Solution for 30 kVA Transformer

TIME IN SECONDS1000 1000900 900400800700600500300

2001.1

.09

.08

.07

.06

.05

.04

.03

.02

.01 .010090

807060504030201

1.9

.8

.7

.6

.5

.4

.3

.209

8654327


51/105

4%

30 KVA

GE Q Line THQB

Frame = 100A Trip = 50A

C*

THQB Modlel C - 1,2P

Frame = 100A

Trip = 60AD* GE Q

Line30 KVA FLA30 KVA INRUSHA

GE RecordP

Trip = 100A

Inst = 11X (2750A)FGN Frame =

2126A

B

250A

lus

Trip = 100A

Inst = 11X (2750A)B GE

FGN

Fra

RecordPlus

me = 250A8006005004003002001009080605040302010 9

8765432700701.9.8.7.6.5.4.3.2.1.09.08.07.06

.05

.04

.03

.02

CURRENT IN AMPERES X 10 AT 208 VOLTSTIME IN SECONDS

The following parameters are the basis of the above selective coordination plot:Minimum allowable Z% = 4.0%

65 kA (X/R=4.9) @ 480V; 2.1 kA @ 208V


52/105

45 kVA Transformer Template(with Record Plus Type FG Primary Main)


53/105

480V

A

45 KVA

3.5%

B208VA

B

C

D

BUS-1

BUS-265 KA (SYM)C* D*

GE Record Plus MCCB Frame Type: FGNFrame Size: 600A

Sensor: 250ATrip: 100AIOC Setting: 11X (2750A)

GE Record Plus MCCB Frame Type: FGN

Frame Size: 600A

Sensor: 250ATrip: 150A

IOC Setting: 11X (2750A)


* GE Q-Line MCCB

Frame Type: THQB Model C Frame Size: 100A - 1, 2P Trip: 60A


54/105

Notes:





configurations.





55/105


34.5.6.812345678910567891000234

5678910000.6.8123467891024678910023467891000234678910000.55555

Time-current CurveFully Selective Solution for 45 kVA TransformerCURRENT IN AMPERES X 10 AT 208 VOLTS800700800700

TIME IN SECONDS

1000 10900 9004002006005003001.01 .0140

00


56/105

9080706050302014

09

8

76532

45

KVA

FLA

A

GE

F

G

N

Reco

rd

Pl

us

T

ri

p

I

n

st

F

=

1

1

X

10

0A

25

0A

(

2

7

5

0

A

)

B

GE

R

e

c

o

r

d

P

lu

s

FGNF

=

250A


57/105

rame

T

ri

p

I

n

st

=

15

0A

=

11

X

(2750A

)

45

KV

A

3.5

%

C

*

G

EQ

Li

ne

T

H

Q

B

Fr

a

m

e

=1

0

0

A

T

ri

p

=

50

A

4

5

K

V

A

I

N

R


58/105

U

S

H

D

*

G

E

T

H

Q

B

Q

Li

ne

M

od

el

C

F

ra

m

e =

10

0A

-

1,2P

T

ri

p

=

60

A

B

3627A

4002004020426005003001009080706050

3010 987653

TIME IN SECONDS1.9

.8

.7

.6

.5

.4

.3

.2


59/105

.1.09

.08

.07

.06

.05

.04

.03

.021.9.8

.7

.6

.5

.4

.3

.2

.1

.09

.08

.07

.06

.05

.04

.03

.02



60/105

BUS-2

B 208V

65 KA (SYM)

BUS-1

480V

A

75 KVA

4.5%

C* D*

B

C

D


Frame Size: 600A

Sensor: 250A

Trip: 110AIOC Setting: 11X (2750A)


61/105


Frame Size: 600A




* GE Q-Line MCCB

Frame Type: THQB Model C Frame Size: 100A – 1, 2P Trip: 60A


62/105

Notes:





configurations.





63/105

23

Time-current CurveFully Selective Solution for 75 kVA Transformer.5.6.812345678910234567891002345678910002345678910000800800700700

75 KVA600600

FLA500500400

4003003002002001

0090

10090808070706060

= 11X (2750A)

Inst50504040

75 KVA4.5%3030202010910 9887766


64/105

554433

Trip

= 100A22

1.91.9.8.8.7.7.6.6.5.5.4.4.3.3.2.2

D*GE

75 KVAINRUSH

0A).1

.09.1.09.08.08.07.07.06.06.05.05.04.04.03.03.02.02

B


TIME IN SECONDS1000 10900 900.01 .01

Q Line

THQB Model C

Frame = 100A - 1,2P

Trip = 60A

C*

GE Q Line THQB

Frame = 100A

A

GE RecordPlus FGNFrame = 250A Trip = 110A

B

GE RecordPlus FGN Frame = 400A Trip = 225A Inst = 11X (440

CURRENT IN AMPERES X 10 AT 208 VOLTSThe following parameters are the basis of the above selective coordination plot:

Minimum allowable Z% = 4.5%

65 kA (X/R=4.9) @ 480V; 4.7 kA @ 208V


65/105

112.5 kVA Transformer Template(with Record Plus Type FG Secondary Main)


66/105

65 KA (SYM)

BUS-1 480V

A

112.5 KVA

4.2%

A




B


Frame Size: 600A



C



67/105

208V

BUS-3

B

C* D*

D * GE TEY MCCB

Frame Type: TEY, 3P Frame Size: 100A Trip: 60A


68/105

Notes:





configurations.





69/105

25


9100234.5.6.8123456789105678

910002345678910000

Time-current CurveFully Selective Solution for 112.5 kVA Transformer.6.8123467810234679100234678100023467

910000.559585958800800700700


70/105

112.5 KVAFLA

600600500500400400300300

A GERecordPlus200200

B GE

RecordPlus

Trip =

22

5A

11X (4400A)

Inst =1

0090

10090808070706060505040403030202010

910 9887766554

43322

D*GE

E1501.9

1.9

TEY Frame =.8.8

100A.7.7.6.6

Trip = 60A.5.5.4.4.3.3.2.2

C* GE Q

Line

THQB.1

.09.1.09


71/105

112.5 KVA.08.08.07.07

INRUSH.06.06.05.05

.04

.04

.03

.03

.02

.02

B


1000 10900 900.01 .01

Trip = 350A

Inst = 11X (4400A)

FGN

Frame = 400A

112.5 KVA

4.2%

Frame = 100A

Trip = 100A

FGN

Frame = 400ACURRENT IN AMPERES X 10 AT 208 VOLTS

The following parameters are the basis of the above selective coordination plot:

Minimum allowable Z% = 4.2%65 kA (X/R=4.9) @ 480V; 7.5 kA @ 208V

TIME IN SECONDS


72/105

A

B

C

D

112.5 kVA Transformer Template (with ABBS7 Secondary Main)


73/105

BUS-2

208V

B

CA

112.5 KVA

4.2%

65 KVA (SYM)

BUS-1

480V

BUS-3

D* E*


Frame Size: 600A



ABB S7 MCCB

Frame Type: ISOMAX Frame Size: 1200A

Sensor: 1000ALT Trip: 0.4X (400A)LT Delay: AST Trip: 10X (10000A)

ST Delay: DI2t: Out







74/105

E * GE TEY MCCB

Frame Type: TEY Frame Size: 100ATrip: 60A

Notes:





configurations.





75/105

Time-current CurveFully Selective Solution for 112.5 kVA Transformer

TIME IN SECONDS1000 10900 900400800

7006005003002001

.1.09.08.07.06.05.04.03.02.01 .01

0090

8070605040

302010

1.9

.8

.7

.6

.5

.4

.3

.286429753

Trip = 225AC GE

FGNFrame = 250A

Inst = 11X

RecordPlus

4.2%

112.5 KVA

(2750A)

E*

GE E150 TEY

Trip = 60A

Frame= 100A

THQB

Frame = 100A Trip = 100A

D*GE Q Line112.5 KVA FLA

112.5 KVA

INRUSH

A

GE RecordPlus

TripBABB


76/105

Tap =

Sensor =Cur Set = 0.4X (400A)LT Band =

STPU = 10X (10000A)

ST Delay

STPU I2t = Out

FGN

Frame = 400A

Inst =

Inst =

= 2

PR212

1000A

11X

12X (12000A)

25A

C

7507A

S7 (1000ACT)

= D

A

(4400A)4004048007006005003002001009080706050302098765

321.9.8.7.6.5.4.3.2.1.09.08.07.06.05.04.03.0210

TIME IN SECONDS



77/105

150 kVA Transformer Template(with Record Plus Type FG Primary Main)


78/105

480V

A

150 KVA

4.4%

AB

C

D

BUS-1

BUS-3

208V

65 KVA (SYM)

B

C* D*

GE Record Plus MCCB Frame Type: FBN

Frame Size: 600A

Sensor: 400ATrip: 250AIOC Setting: 11X (4400A)

GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 600ARating Plug: 450A


* GE Q-Line MCCB Frame Type: THQ Frame Size: 100A Trip: 100A

* GE Q-Line MCCB

Frame Type: THQB Model C Frame Size: 100A – 1, 2P Trip: 60A


79/105

Notes:





configurations.





80/105

TIME IN SECONDS

CURRENT IN AMPERES X 10 AT 208 VOLTS

.5

.81234567810234567910023456781000234567910000.69898

TIME IN SECONDS1000 10900 900400800700600500300200100

90.1

.09

.08

.07

.06

.05

.04

.03

.02

.01 .01408070605030201

1.9

.8

.7

.6

.5

.4

.3

.209

8765432

Trip = 450A

Inst = 11X (6600A)

B


81/105

GE RecordPlFGNFrame =

4.4%

150 KVATHQB Frame

Trip = 100AC*

GETHQB Model C Frame = 100A - 1,2P Trip = 60A

D* GE Q

600A

Q LineusLine

= 100A150 KVA FLA

150 KVA

INRUSHA

GE RecordPlus

Trip = 250AFGN Fram

Inst = 11X (4400A)e =400A

9806A

B40020040204280070060050030010090807060503010 9876531.9.8.7.6.5.4.3.2.1.09.08.07.06

.05

.04

.03

.02

.5 .6 .8 1 2 3 4 5 67 8 9 10 2 3 4 5 67 8 9 100 2 3 4 5 67 8 9 1000 2 3 4 5 67 8 9 10

Time-current CurveFully Selective Solution for 150

kVA Transformer


82/105

The following parameters are the basis of the above selective coordination plot:Minimum allowable Z% = 4.4%

65 kA (X/R=4.9) @ 480V; 9.8 kA @ 208V



83/105

150 kVA Transformer Template (with ABB S7 Primary Main)


84/105


85/105

A

B

C

D

A150 KVA

4.4%

65 KA (SYM)

BUS-1

480V

BUS-2

B

C*

208V

BUS-3

D* E*ABB S7 MCCB


Sensor: 1000ALT Trip: 0.4X (400A)LT Delay: AST Trip: 8X (80000A)

ST Delay: DI

2t: Out


ABB S7 MCCB


Sensor: 1200ALT Trip: 0.4X (480A)

LT Delay: BST Trip: 8X (9600A)ST Delay: C

I2t: Out



Frame Size: 600A

Sensor: 400A

Trip: 350AIOC Setting: 11X (4400A)



86/105

E * GE TEY MCCB

Frame Type: TEY FrameSize: 100A Trip: 60A

Notes:

Where an overlap of the time-current curve, instantaneous overcurrent characteristics seem

to indicate non-selectivity, GE Overcurrent Instantaneous Selectivity Tables, DET-537, were

used to validate selective operation.


configurations.





87/105

31.6.812346 78

9102346 7891002346 78910002346 789

10000.55555

Time-current CurveFully Selective Solution for 150 kVA TransformerCURRENT IN AMPERES X 100 AT 208 VOLTS87800700

TIME IN SECONDS

18 ;8

6543

.09..

.

.

.

.01 .01

000000

150

K

V

A

00 FL

A00ABBPR212

00 ensorTap=1200A

=

S7

(

1

2

0

0

A

C


88/105

T

)00 15

0

4.4

%

K

VA

Cur

Set

LT

Ban

d

STP

U =

=

0.

4

X

=

B

8

X

(9

60

0

A

)

(4

80

A)

00

ST

Dela

y

= C

90

80STP

U I2t

=

Ou

t

Inst

=

12X

(

1

4

4

0

0

A

)60

30

4020

8

6

5

4

3

21

A

A

B

BPR212

GEE150

GE

9Sensor= S7 (1


89/105

0

0

0

A

C

T

)

8

7

Fram

e =

10

0A

T

a

p

=

1000A

6

Trip

= 60A

C

u

r

Set =

0.4X

(4

0

0

A

)5 L

T

Band

= A4

ST

PUST

=

3 C

*

GE

Re

cor

dPl

us

STP t=

U I

2 FG

N

Fra

meTri

p =

=

40

0A

35

0A

1

50

K

VA

I

n

st

= 12X

(12000

A)

1 Inst =

11

X

(

4

4

0

0

A

)

I

N

R

U

SH

*

GE

Li

ne


90/105

T

H

Q

B

Fr

am

e=

10

0

A

Trip =

10

0A

B A

9806A 82

17

9A

60040020010090

60

40206425003008070503010987531.9.8.7.6.5

.4

.3

.2TIME IN SECONDS

21

.

.

.1

.09

.08

.07

.06

.05

.04

.03

.02

The following parameters are the basis of the above selective coordination plot:

Minimum allowable Z% = 4.4%65 kA (X/R=4.9) @ 480V; 9.8 kA @ 208V


91/105

225 kVA Transformer Template (with ABB S7 Secondary Main)


92/105

A

B

C

D

480VA

208V

B

BUS-1

BUS-2

65KA (SYM)225 KVA

4.1%

C

1BUS-3

D*GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 600ARating Plug: 450A


ABB ISOMAX MCCB Frame Type: S7

Frame Size: 1200A

Sensor: 1000ALT Setting: 0.7X (700A)

LT Delay: B

ST Setting: 10X (10000A)ST Delay: D

I2t: OutIOC Setting: 12X (12000A)

1 GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 600ARating Plug: 400A




93/105

Notes:





configurations.




1 FG400 and FG600 are selective with all THQB MCCBs. Certain THQBs not selective with FG250

MCCBs.


94/105

TIME IN SECONDS


.5

.81234567810234567910023456781000234567910000.69898

TIME IN SECONDS

1000 10900 9004002008007006005003001

.1.09

.08

.07

.06

.05

.04

.03

.02

.01 .0140

0090

8070605030201.9.8.7.6.5

.4.3

.24

09

8765321

Tap = 1000A Cur Set = 0.7XB ABB

Sensor = S7


95/105

LT Band = B STPU = 10X

(10000A)

ST Delay = D

STPU I2t = Out

Inst = 12

PR212

X (12000A)

(1000ACT)4.1%

225

(700A)

Trip = 400A

Inst = 11X (6600A)C GE

FG

Fram

KVA

N

RecordPlus

D*

GE Q Line

THHQB

Frame = 100ATrip = 100A

e = 600A225 KVA FLA

225 K

INRU

VA

SH

Trip

A

GE RecordPlus

FGN

Frame = 600A

Inst = 11X (6600A)

= 450A

B16319A800600400200806050402010 9865432700500300100

90703071.9.8.7.6.5.4.3.2.1.09.08.07


96/105

.06

.05

.04

.03

.02.5 .6 .8 1 2 3 4 5 67 8 9 10 2 3 4 5 67 8 9 100 2 3 4 5 67 8 9 1000 2 3 4 5 67 8 9 10

Time-current CurveFully Selective Solution for 225

kVA Transformer




97/105

A

B

300 kVA Transformer Template (with ABB S7 Secondary Main)


98/105

65KAIC (SYM)

BUS-1

480V

A

300 KVA

4.0%

BUS-2

B

C

208V1

BUS-3

D*, 2 E*C

D

E


Frame Size: 1200A


LT Delay: BST Setting: 10X (10000A)

ST Delay: DI2t: Out



Frame Size: 1200A


LT Delay: AST Setting: 10X (1000A)

ST Delay: DI2t: Out


1 GE Record Plus MCCB Frame Type: FGN Frame Size: 600A Sensor: 600ARating Plug: 500AIOC Setting: 11X (6600A)


99/105

*2 GE Q-Line MCCB Frame Type: THHQB Frame Size: 100ATrip: 100A

* GE Record Plus MCCBFrame Type: FBNFrame Size: 100A

Trip: 100

A

Notes:


non-selectivity, GE Overcurrent Instantaneous Selectivity Tables, DET-537, were used to validate selectiveoperation.

Unless otherwise noted, overcurrent protective devices shown are for all available pole configurations.



* Base layer circuit breaker settings are “not to exceed” values 1 FG400 and FG600 are selective with all THQB MCCBs. Certain THHQBs not selective with FG250 MCCBs.2 THHQB can only be used if AIC is less than 22 kA at the THHQB MCCB


100/105

3510


89100234.5.6.81234567895678

910002345678910000.5.6.812345678

9102345678910023456789100023

45678910000

Time-current CurveFully Selective Solution for 300 kVA TransformerCURRENT IN AMPERES X 10 AT 208 VOLTS

TIME IN SECONDS1000 1900 9


101/105

4002008007006005003001

.1.09.08.07.06.05.04.03.02.01 .014020

0090

80706050301

1.9

.8

.7

.6

.5

.4

.3

.242

09

87653

GE Q Line

THHQB

Frame = 1

Trip = 100A

D*

FGN

Frame = 600A

Trip = 500A

Inst = 11X (6600A)

FBNFrame = 100A

Trip = 100A

CGE RecordPlusE*

GE Record Plus

00A

4%

300 KVA

300 KVA

FLAA

AB

Sensor = S7 (1000ACT)

Tap = 1000A

Cur Set = 0.5X (500A)

LT Band = B

STPU = 10X (10000A)

ST Delay = D

STPU I

2

t = Out

Inst = 12 X (12000A)

300 KVA

INRUSH

B PR212

B

ABB PR212

Sensor = S7 (1000ACT)

Tap = 1000A

Cur Set = 1X (1000A)

LT Band =

STPU = 10 X (10000A)

ST Delay = D

STPU I2t =

Inst = 12X (12000A)


102/105

C

22434A

Asymmetrical

A

Out40020040204

280070060050030010090

807060503010 9876531.9.8.7

.6

.5

.4

.3

.2

.1

.09

.08

.07

.06

.05

.04

.03

.02TIME IN SECONDS



103/105

Typical GE Dry Type Transformer Data

Table 3

480V Delta to 208/120V Wye, TP-1 Transformers

kVA °C Rise Aluminum Copper

Cat. No.%

R

%

X

%

Z

X/

RCat. No. %R

%X %Z X/

R

15 150 9T83B3871 5.1 3.3 6.1 0.6 9T83C9871 4.3 2.2 4.8 0.5

115 9T83B3871G15 5.13.3

6.10.6 9T83C9871G1

54.3

2.24.8 0.5

80 9T83B3871G80 5.13.3

6.10.6 9T83C9871G8

01.3

2.12.5 1.6

30 150 9T83B3872 3.7 4.2 5.6 1.1 9T83C9872 2.8 4.3 5.1 1.8

115 9T83B3872G15 3.74.2

5.61.1 9T83C9872G1

52.8

4.35.1 1.8

80 9T83B3872G80 2.12.7

3.41.3 9T83C9872G8

01.9

2.33 1.2

45 150 9T83B3873 3.5 4.1 5.4 1.2 9T83C9873 3 3.5 4.6 1.2

115 9T83B3873G15 3.54.1

5.41.2 9T83C9873G1

53 3.5 4.6 1.2

80 9T83B3873G80 1.33.1

3.42.4 9T83C9873G8

0 1 2.5 2.7 2.5

75 150 9T83B3874 3.9 4.5 6.0 1.2 9T83C9874 3.4 4 5.2 1.2

115 9T83B3874G15 2.84.7

5.51.7 9T83C9874G1

52.7

3.54.4 1.3

80 9T83B3874G80 1.13.5

3.73.2 9T83C9874G8

01 2.6 2.8 2.6

112.5 150 9T83B3875 3.1 5.0 5.9 1.6 9T83C9875 2.7 3.8 4.6 1.4

115 9T83B3875G15 2.34.1

4.71.0 9T83C9875G1

52.5

4.85.4 1.9

80 9T40G0005G81 1.82.2

2.81.2 9T45G0005G8

11.5

1.92.4 1.3

150 150 9T40G0006 2.4 3.7 4.4 1.5 9T45G0006 2 3.1 3.7 1.6

115 9T40G0006G51 2.43.7

4.41.5 9T45G0006G5

12 3.1 3.7 1.6

80 9T40G0006G81 2.43.7

4.41.5 9T45G0006G8

12 3.1 3.7 1.6

225 150 9T40G0007 4.3 5.6 7.0 1.3 9T45G0007 3.7 4.6 5.9 1.2

115 9T40G0007G51 2.45.0

5.51.9 9T45G0007G5

12 3.8 4.3 1.9

80 9T40G0007G81 2.64.9

5.61.9 9T45G0007G8

12 3.8 4.3 1.9

300 150 9T40G0008 4.0 6.2 7.4 1.6 9T45G0008 3.3 4.6 5.7 1.4

115 9T40G0008G51 1.85.2

5.52.9 9T45G0008G5

11.6

3.23.5 2.0


104/105

Glossary

AbbreviationsAHJ Authority having jurisdictionAIC Amperes interrupting currentATS Automatic transfer switch

FTL Feed through lugsICCB Insulated case circuit breaker (UL Standard 489 rated)

IOC Instantaneous overcurrentkA Kilo-amperes

LVPCBLow Voltage Power Circuit Breaker (ANSI Standard C37. rated)MCCBMolded Case Circuit Breaker (UL Standard 489 rated)

MCS Molded Case Switch

NEC National Electric Code

OCPD Overcurrent Protective Device

V Volts

xfmr Transformer

Terms As Used in This Publication0.1 second selectivity

Two adjacent OCPDs are selective with one another over the full range of AIC, but only downto 0.1 seconds on the TCC. This suggests that their long time and short time characteristics areselective with one another, but that their instantaneous characteristics (that portion of the TCC

below 0.1 seconds) may not be selective

Code

National Electrical Code

Downstream / Upstream

A circuit breaker's or OCPDs location relative to the power source. For example, a main circuit

breaker in a panel is closer to the power source than a (smaller sized) branch breaker in thesame panel is upstream of the branch breaker. Correspondingly, the branch breaker isdownstream of the main breaker in this example.

Full Selectivity

In the context of NEC Articles 700, 701 and 708, this means two adjacent OCPDs are selective

with one another over the full range of available fault current magnitudes and for all types offault current.

Layer

On a one-line diagram, circuit breaker or OCPD layers are counted from a load back to a power

source. Each circuit breaker placed above another on the circuit back to the source is anotherlayer.


105/105

GE

41

Wood

ford

Aven

ue,

Plain

ville,

CT

06062

www.

geele

ctrica

l.com

© 2010 General Electric Company

imagination at

workDET-
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Documents

Desing and Selectivity LV_GE