21955721 Selective Coordination

7/28/2019 21955721 Selective Coordination

http://slidepdf.com/reader/full/21955721-selective-coordination 1/60

© 2001 Cooper Bussmann, Inc.

Suggestion on How to Use

• Industry Trainers are encouraged to use thismaterial in their sessions

• Download both the PowerPoint file (.ppt) and script

file (.pdf)• Print the script file (.pdf) and read the script as you

view the PowerPoint presentation in the “SlideShow” view. In this way you see the slides in largeformat and have animation (if there is any)

• Must have PowerPoint and Adobe Reader application software on your system.



SelectiveCoordination




Selective Coordination

• For 600 Volts & less

• Easy concept to understand

• Hard to verify, if you do not know what to look for

• Misinterpretations or lack of understanding is veryprevalent

• People review curves (hand drawn or computer generated) and they do not know how to interpret





Definition:

The act of isolating a faulted circuit from theremainder of the electrical system, therebyeliminating unnecessary power outages. Thefaulted circuit is isolated by the selective operationof only the overcurrent protective device closest to

the overcurrent condition.



Without Selective Coordination With Selective Coordination

Selective Coordination: AvoidsBlackouts

OPENS

NOT AFFECTED

UNNECESSARY

POWER LOSS

OPENS

NOT

AFFECTED Fault Fault




Selective Coordination: NEC®

240.2 Definitions

Coordination.

The proper localization of a fault condition torestrict outages to the equipment affected,accomplished by the choice of selective

fault-protective devices.


http://slidepdf.com/reader/full/21955721-selective-coordination 7/60© 2001 Cooper Bussmann, Inc.

Selective Coordination: NEC ®

240.12 Electrical System Coordination whereorderly shutdown required to minimizehazards

620.62 Selective Coordination required wheremore than one elevator is supplied by singlefeeder.

517.17 Selective coordination between main

and feeder required for health care facilitieswhere main has GFP (feeder also required tohave GFP).




Chapter 2 VideoSelective Coordination




CoordinationCircuit Breakers



Spring Loaded ContactsLatch

Bimetal

Magnetic Element

Line

Load

Trip BarCircuit Breaker

Operation




Bimetal

Line

Load

Trip Bar Thermal OverloadOperation

Normal State




Line

Load

Trip Bar

Bimetal

Thermal OverloadOperation

Unlatch & Open




Magnetic Element

Line

Load

Trip Bar Short CircuitOperation

Normal State



Spring Loaded ContactsUnlatch

Magnetic Element

Line

Load


Unlatching




Magnetic Element

Line

Load


Opening




Magnetic Element

Line

Load


Cleared



Coordination -Thermal-Mag Circuit Breakers

Thermal Magnetic Molded

Case Circuit Breaker Time-

Current Curve

Overload Region

Instantaneous Region

Interrupting Time

Unlatching Time

Interrupting Rating



Coordination -Thermal-Mag Circuit Breakers (See SPD)




Current

T i m e

A

B

C

D

4000A Fault



OPENS

NOT AFFECTED

UNNECESSARY

POWER LOSS Fault

Lacking Coordination

S l ti C di ti



Selective Coordination -Insulated Case Circuit Breakers (SeeSPD)

2000A Insulated Case

Circuit Breaker

STD Is an Option - Allows breaker to delay opening

Instantaneous Override

built-in: may be as low as12X the breaker rating

Will often result in lack of

coordination

S l ti C di ti



Selective Coordination -Insulated Case Circuit Breakers (SeeSPD)

2000A Insulated Case with

STD and Instantaneous Override

and 100A Molded Case ThermalMagnetic Circuit breaker - NO

Coordination in Short-Circuit

Region (above 21,000A)




Selective Coordination -LV Air Power Circuit Breakers (See SPD)

Short Time Delay - Allows the fault

current to flow for up to 30 cycles.

Used to coordinate with downstream

Subjects equipment to high

mechanical and thermal stresses, often

violating 110.10

Arc Flash/ Blast Risks Much

Higher

High Cost, Larger Equipment




Selective Coordination: Fuses






S l ti C di ti F




Time CurrentCurves

Selective Coordination:Fuses(See SPD)

S l ti C di ti F




Selectivity Ratio

Guide Based on

Thermal Principle

Based on I

2

t Clear

Not Melt

I2t melting > I2t Clearing

1200 A 600 A

Selective Coordination:Fuses(See SPD)




Selective Coordination (SeeSPD )

Selectivity Ratio Table Assures Coordination!

No Plotting required!

LOW-PEAK ® : LOW-PEAK ®

2:1 Line:Load Ratio

L i n e

S i d e

F u s e

Load Side Fuse

S l ti C di ti




Example:

Main: KRP-C 1200 SP

Feeder: LPS-RK 200 SP

Branch: LPS-RK-30 SP

MSB

1200 A

200 A

30 A

480V, 3 phase

MCC

GFP

Selective Coordination -Fuses




Selective Coordination - Fuses

Use Selectivity Table

Main KRP-C 1200 SP

Feeder LPS-RK 200 SP

Branch LPS-RK 30 SP

What happens: Branch Circuit Isca = 5000 A or

50,000A or 300,000A ?




Lineside KRP-C 1200SP to Loadside LPS-RK 200SP

1200/200 = 6:1 Table only need 2:1


Lineside LPS-RK 200SP to Loadside LPS-RK 30SP

200/30= 6.67:1 Table only need 2:1


Selective Coordination- Fuses




Fault

NOT

AFFECTED

OPENS






Simple Rules for Checking

• Circuit Breakers (instantaneous trip)

• Fuses



Can you look at this

and assess whether

coordinated?

You do not even

need to draw curve!



Simple Rule: (Amp rating) x (I.T. setting) =

Isca @ which CB will unlatch:

CB IT IT

Amp Set Amp Pickup

100 5X 500

200 5X 1,000

400 10X 4,000

1600 12X 19,000

See SPD

100 A

200 A

400 A

1600 A





• You already know the simple rule for fuses.

• Simply use amp rating ratios• Typically 2:1 for

Low Peak Fuses to Low Peak Fuses





• Do coordination exercise using simple rules

– Fusible system – Circuit breaker system

• It’s simple!




Fault

10000 Amps

Low Peak KRP-C 1000 SP

Low Peak

LPJ 200 SP

Low Peak

LPJ 20 SP

Are These Selectively

Coordinated?




Fault

10000 Amps

Low Peak KRP-C 1000 SP

Low Peak

LPJ 200 SP

Low Peak

LPJ 20 SP


Coordinated?

OPENS

NOT

AFFECTED

Fault

10000 Amps

Low Peak

KRP-C 1000 SP

Low Peak

LPJ 200 SP

Low Peak

LPJ 20 SP

Selectively Coordinated





Coordinated?

Fault

10000 Amps

1000 A. CB

IT @ 10 X

200 A. CB

IT @ 10 X

20 A. CB

IT @ 10X





Coordinated?

Fault

10000 Amps

1000 A. CBIT @ 10 X

200 A. CB

IT @ 10 X

20 A. CB

IT @ 10X

Not Coordinated

OPENS

NOT

AFFECTED

Fault

10000 Amps

1000 A. CB

IT @ 10 X

200 A. CB

IT @ 10 X

20 A. CB

IT @ 10X




Unnecessary

Blackout

The Issue:

Lack of coordination

takes out other loads

OPENS Fault

10000 Amps

1000 A. CB

IT @ 10 X

200 A. CB

IT @ 10 X

20 A. CB

IT @ 10X

Ground Fault Protection 230 95




Ground Fault Protection 230-95




See SPD

GFP H lth C 517 17




GFP Health Care 517-17

Where one level of GFP is provided per 230.95 or 215.10 anadditional step of GFP on feeders required.

The Ground Fault Protection for service and feeder shallbe fully Selectively Coordinated

What does this mean ?




517-17 Health Care GFP

Main 1200 A CB

Feeder 200 A CB

GFP on Main & Feeder

Does this meet 517-17?




517-17 Health Care GFP

Main 1200 A Fuse

Feeder 200 A Fuse

GFP on Main & Feeder

Does this meet 517-17?




Following Excerpts from IEEE Standards

IEEE 242 1986 “BUFF BOOK”




IEEE 242-1986 BUFF BOOK Protection and Coordination of Industrialand Commercial Power Systems

Page 263 6.4.1 Protection (SeriesConnection). It should be noted thatselectivity will not be provided at any currentlevel where the breaker trip characteristiccurves overlap when this protection scheme isused, that is, both circuit breakers will trip.

IEEE 242-1986 “BUFF BOOK”




IEEE 242-1986 BUFF BOOK Protection and Coordination of Industrialand Commercial Power Systems

Page 528 Coordination 14.2.2

Coordination can easily be achieved with low

voltage current-limiting fuses that have fastresponse times. Manufacturer’s time currentcurves and selectivity ratio guides are used for both overload and short-circuit conditions,

precluding the need for calculating time intervals.

IEEE 141 1993 “RED BOOK” Electrical




IEEE 141-1993 “RED BOOK” Electrical

Power Distribution for Industrial Plants

Page 256 5.7.2.3 Low-voltage circuitbreakers. To achieve this level of selectivity,power circuit breakers utilize short-time delaytrips. The equipment protected by thisbreaker must be designed to handle theavailable short-circuit current for the durationof the short-time delay.





IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrialand Commercial Power Systems

Page 528 Coordination 14.1 A coordination

study should be made when the availableshort-circuit current of the source to the plantis increased.





IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrialand Commercial Power Systems

Page 528 Coordination 14.1 A coordination study

or revision of a previous study may be needed for an existing plant when new loads are added to thesystem or when existing equipment is replacedwith higher rated equipment.

IEEE 602 1996 “WHITE BOOK”




IEEE 602-1996 WHITE BOOK” Electrical Systems in Health CareFacilities

Page 57/58 3.7.1.1 Protection requirements. As total selectivity and maximum safety topersonnel are critical, a total short-circuitcoordination, and component protection studyshall be performed.

IEEE 141 1993 “RED BOOK” Electrical




IEEE 141-1993 RED BOOK Electrical

Power Distribution for Industrial Plants

Page 256 5.7.2.3 Low-voltage circuitbreakers. It should be recognized thatproviding selectivity to the load-side devices

may result in equipment bus structures beingunderprotected. The Standards for suchequipment, ANSI/UL 891-1984 [B21] for switchboards, ANSI/UL 845-1987 [B20] for motor control centers,

IEEE 1015-1997 “BLUE BOOK”




IEEE 1015-1997 BLUE BOOK

Applying Low-Voltage Circuit BreakersUsed in Industrial and Commercial Power

Systems

Page 135 5.5.4 Short-time delay

All MCCBs and most ICCBs with a short time delayhave an instantaneous override. If selectivecoordination is required for fault currents above theinstantaneous override level, a power circuit

breaker defined as an LVPCB with a short-timedelay option, as shown in Figure 5-16, should beconsidered.

IEEE 242-1986 “BUFF BOOK”




IEEE 242 1986 BUFF BOOK Protection and Coordination of Industrialand Commercial Power Systems

Page 252 6.3 Trip Unit The resulting combination of long-time delay and short-time delay characteristicsprovides delayed tripping for all levels of overcurrent

below the instantaneous response. This providestime for downstream circuit breakers to operate andclear the fault. The withstand of other electricalcomponents in the current path should be checked

to be certain they can handle the additional stressassociated with the longer clearing time.

IEEE 1015 1997 “BLUE BOOK”





Applying Low-Voltage Circuit BreakersUsed in Industrial and Commercial Power Systems

Page 62 3.38 Series-connected rating.Sometimes it is erroneously thought that series

combinations are at a disadvantage with regard tocoordination as compared to fully rated systems.The fact is that even fully rated circuit breakerswith instantaneous trips will not “coordinate” once

the fault level exceeds both circuit breakers’instantaneous trip levels.

IEEE 1015-1997 “BLUE BOOK”




Applying Low-Voltage Circuit BreakersUsed in Industrial and Commercial Power Systems

Page 134 5.5.3 Series MCCBs

Selective coordination is limited to currents

below the instantaneous pickup of the line-side circuit breaker. For any fault downstreamof the load-side MCCB having a currentgreater than the instantaneous pickup of the

line-side MCCB, both circuit breakers trip, andpower is interrupted to unfaulted circuits fed bythe line-side circuit breaker.

Documents

21955721 Selective Coordination