Selective Coordination

Suggestion on How to Use • Industry Trainers are encouraged to use this material 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 “Slide Show” view. In this way you see the slides in large format and have animation (if there is any) • Must have PowerPoint and Adobe Reader application software on your system.

© 2001 Cooper Bussmann, Inc.

Selective Coordination

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

© 2001 Cooper Bussmann, Inc.

Selective Coordination Definition: The act of isolating a faulted circuit from the remainder of the electrical system, thereby eliminating unnecessary power outages. The faulted circuit is isolated by the selective operation of only the overcurrent protective device closest to the overcurrent condition.

© 2001 Cooper Bussmann, Inc.

Selective Coordination: Avoids Blackouts Without Selective Coordination

With Selective Coordination

OPENS NOT AFFECTED

OPENS

UNNECESSARY POWER LOSS

NOT AFFECTED

Fault

Faul t

Selective Coordination: NEC

®

240.2 Definitions Coordination. The proper localization of a fault condition to restrict outages to the equipment affected, accomplished by the choice of selective fault-protective devices.

© 2001 Cooper Bussmann, Inc.

Selective Coordination: NEC

®

240.12 Electrical System Coordination where orderly shutdown required to minimize hazards 620.62 Selective Coordination required where more than one elevator is supplied by single feeder. 517.17 Selective coordination between main and feeder required for health care facilities where main has GFP (feeder also required to have GFP).

© 2001 Cooper Bussmann, Inc.

Selective Coordination

Chapter 2 Video Selective Coordination

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Selective Coordination

Coordination Circuit Breakers

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Magnetic Element Bimetal Trip Bar

Circuit Breaker Operation

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Bimetal Trip Bar

Thermal Overload Operation Normal State

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Bimetal Trip Bar

Thermal Overload Operation Unlatch & Open

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Magnetic Element

Trip Bar

Short Circuit Operation Normal State

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Magnetic Element

Trip Bar

Short Circuit Operation Unlatching

Load Line Unlatch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Magnetic Element

Trip Bar

Short Circuit Operation Opening

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Magnetic Element

Trip Bar

Short Circuit Operation Cleared

Load Line Latch

Spring Loaded Contacts © 2001 Cooper Bussmann, Inc.

Coordination Thermal-Mag Circuit Breakers Thermal Magnetic Molded Case Circuit Breaker TimeCurrent Curve ◆

Overload Region

◆Instantaneous

Region ◆Interrupting Time ◆Unlatching Time

◆Interrupting Rating © 2001 Cooper Bussmann, Inc.

Coordination Thermal-Mag Circuit Breakers (See SPD)

© 2001 Cooper Bussmann, Inc.

Selective Coordination D

Time

C

B A

4000A Fault

Current © 2001 Cooper Bussmann, Inc.

Lacking Coordination

OPENS NOT AFFECTED UNNECESSARY POWER LOSS

Fault

© 2001 Cooper Bussmann, Inc.

Selective Coordination Insulated Case Circuit Breakers (See SPD) 2000A Insulated Case Circuit Breaker ◆ STD Is an Option - Allows breaker to delay opening ◆ Instantaneous Override built-in: may be as low as 12X the breaker rating ◆ Will often result in lack of coordination ◆

© 2001 Cooper Bussmann, Inc.

Selective Coordination Insulated Case Circuit Breakers (See SPD) 2000A Insulated Case with STD and Instantaneous Override and 100A Molded Case Thermal Magnetic Circuit breaker - NO Coordination in Short-Circuit Region (above 21,000A) ◆

© 2001 Cooper Bussmann, Inc.

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 © 2001 Cooper Bussmann, Inc.

Selective Coordination: Fuses

© 2001 Cooper Bussmann, Inc.

© 2001 Cooper Bussmann, Inc.

Selective Coordination:Fuses (See SPD)

Time Current Curves

© 2001 Cooper Bussmann, Inc.

Selective Coordination:Fuses (See SPD) Selectivity Ratio Guide Based on Thermal Principle Based on I2t

Not Melt

Clear

I2t melting > I2t Clearing 1200 A 600 A © 2001 Cooper Bussmann, Inc.

Selective Coordination (See SPD ) Line Side Fuse

Load Side Fuse

LOW-PEAK® : LOW-PEAK® 2:1 Line:Load Ratio Selectivity Ratio Table Assures Coordination! No Plotting required! © 2001 Cooper Bussmann, Inc.

Selective Coordination Fuses 480V, 3 phase

Example: Main: KRP-C 1200 SP Feeder: LPS-RK 200 SP Branch: LPS-RK-30 SP

1200 A MSB

GFP

200 A

MCC

30 A © 2001 Cooper Bussmann, Inc.

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 ?

© 2001 Cooper Bussmann, Inc.

Selective Coordination- Fuses

Lineside KRP-C 1200SP to Loadside LPS-RK 200SP 1200/200 = 6:1 Table only need 2:1 Selective Coordination Lineside LPS-RK 200SP to Loadside LPS-RK 30SP 200/30= 6.67:1 Table only need 2:1 Selective Coordination

© 2001 Cooper Bussmann, Inc.

Selective Coordination

NOT AFFECTED OPENS

Fault

© 2001 Cooper Bussmann, Inc.

Selective Coordination Simple Rules for Checking • Circuit Breakers • Fuses

(instantaneous trip)

© 2001 Cooper Bussmann, Inc.

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

1600 A 400 A 200 A 100 A

Selective Coordination • You already know the simple rule for fuses. • Simply use amp rating ratios • Typically 2:1 for Low Peak Fuses to Low Peak Fuses

© 2001 Cooper Bussmann, Inc.

Selective Coordination • Do coordination exercise using simple rules – Fusible system – Circuit breaker system

• It’s simple!

© 2001 Cooper Bussmann, Inc.

Are These Selectively Coordinated? Low Peak KRP-C 1000 SP Low Peak LPJ 200 SP Low Peak LPJ 20 SP Fault 10000 Amps © 2001 Cooper Bussmann, Inc.

Are These Selectively Coordinated?

Selectively Coordinated

Low Peak KRP-C 1000 SP

Low Peak KRP-C 1000 SP

Low Peak LPJ 200 SP Low Peak LPJ 20 SP Fault 10000 Amps

Low Peak LPJ 200 SP NOT AFFECTED OPEN S

Low Peak LPJ 20 SP Fault 10000 Amps © 2001 Cooper Bussmann, Inc.

Are These Selectively Coordinated? 1000 A. CB IT @ 10 X 200 A. CB IT @ 10 X 20 A. CB IT @ 10X Fault 10000 Amps © 2001 Cooper Bussmann, Inc.

Are These Selectively Coordinated?

Not Coordinated

1000 A. CB IT @ 10 X

1000 A. CB IT @ 10 X

200 A. CB IT @ 10 X

200 A. CB IT @ 10 X

20 A. CB IT @ 10X Fault 10000 Amps

NOT AFFECTED OPEN S

20 A. CB IT @ 10X Fault 10000 Amps © 2001 Cooper Bussmann, Inc.

The Issue: Lack of coordination takes out other loads

1000 A. CB IT @ 10 X 200 A. CB IT @ 10 X

Unnecessary Blackout OPEN S

20 A. CB IT @ 10X Fault 10000 Amps © 2001 Cooper Bussmann, Inc.

Ground Fault Protection 230-95

© 2001 Cooper Bussmann, Inc.

See SPD

© 2001 Cooper Bussmann, Inc.

GFP Health Care 517-17

Where one level of GFP is provided per 230.95 or 215.10 an additional step of GFP on feeders required. The Ground Fault Protection for service and feeder shall be fully Selectively Coordinated

What does this mean ?

© 2001 Cooper Bussmann, Inc.

517-17 Health Care GFP

Main Feeder

1200 A CB 200 A CB

GFP on Main & Feeder Does this meet 517-17?

© 2001 Cooper Bussmann, Inc.

517-17 Health Care GFP

Main Feeder

1200 A Fuse 200 A Fuse

GFP on Main & Feeder Does this meet 517-17?

© 2001 Cooper Bussmann, Inc.

Following Excerpts from IEEE Standards

© 2001 Cooper Bussmann, Inc.

IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrial and Commercial Power Systems Page 263 6.4.1 Protection (Series Connection). It should be noted that selectivity will not be provided at any current level where the breaker trip characteristic curves overlap when this protection scheme is used, that is, both circuit breakers will trip.

© 2001 Cooper Bussmann, Inc.

IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrial and Commercial Power Systems Page 528 Coordination 14.2.2 Coordination can easily be achieved with low voltage current-limiting fuses that have fast response times. Manufacturer’s time current curves and selectivity ratio guides are used for both overload and short-circuit conditions, precluding the need for calculating time intervals.

© 2001 Cooper Bussmann, Inc.

IEEE 141-1993 “RED BOOK” Electrical Power Distribution for Industrial Plants Page 256 5.7.2.3 Low-voltage circuit breakers. To achieve this level of selectivity, power circuit breakers utilize short-time delay trips. The equipment protected by this breaker must be designed to handle the available short-circuit current for the duration of the short-time delay.

© 2001 Cooper Bussmann, Inc.

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

Page 528 Coordination 14.1 A coordination study should be made when the available short-circuit current of the source to the plant is increased.

© 2001 Cooper Bussmann, Inc.

IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrial and 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 the system or when existing equipment is replaced with higher rated equipment.

© 2001 Cooper Bussmann, Inc.

IEEE 602-1996 “WHITE BOOK” Electrical Systems in Health Care Facilities Page 57/58 3.7.1.1 Protection requirements. As total selectivity and maximum safety to personnel are critical, a total short-circuit coordination, and component protection study shall be performed.

© 2001 Cooper Bussmann, Inc.

IEEE 141-1993 “RED BOOK” Electrical Power Distribution for Industrial Plants Page 256 5.7.2.3 Low-voltage circuit breakers. It should be recognized that providing selectivity to the load-side devices may result in equipment bus structures being underprotected. The Standards for such equipment, ANSI/UL 891-1984 [B21] for switchboards, ANSI/UL 845-1987 [B20] for motor control centers,

© 2001 Cooper Bussmann, Inc.

IEEE 1015-1997 “BLUE BOOK” Applying Low-Voltage Circuit Breakers Used in Industrial and Commercial Power Systems Page 135 5.5.4 Short-time delay All MCCBs and most ICCBs with a short time delay have an instantaneous override. If selective coordination is required for fault currents above the instantaneous override level, a power circuit breaker defined as an LVPCB with a short-time delay option, as shown in Figure 5-16, should be considered.

© 2001 Cooper Bussmann, Inc.

IEEE 242-1986 “BUFF BOOK” Protection and Coordination of Industrial and Commercial Power Systems Page 252 6.3 Trip Unit The resulting combination of long-time delay and short-time delay characteristics provides delayed tripping for all levels of overcurrent below the instantaneous response. This provides time for downstream circuit breakers to operate and clear the fault. The withstand of other electrical components in the current path should be checked to be certain they can handle the additional stress associated with the longer clearing time.

© 2001 Cooper Bussmann, Inc.

IEEE 1015-1997 “BLUE BOOK” Applying Low-Voltage Circuit Breakers Used 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 to coordination as compared to fully rated systems. The fact is that even fully rated circuit breakers with instantaneous trips will not “coordinate” once the fault level exceeds both circuit breakers’ instantaneous trip levels.

© 2001 Cooper Bussmann, Inc.

IEEE 1015-1997 “BLUE BOOK” Applying Low-Voltage Circuit Breakers Used 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 lineside circuit breaker. For any fault downstream of the load-side MCCB having a current greater than the instantaneous pickup of the line-side MCCB, both circuit breakers trip, and power is interrupted to unfaulted circuits fed by the line-side circuit breaker. © 2001 Cooper Bussmann, Inc.