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Safety BASIC s TM. Fuseology For Safety & Protection. B ussmann’s A wareness of S afety I ssues C ampaign. Available Short Circuit Current. Over Current Protection Device. Load to be Protected. Load Current. Safety BASICs TM Fuseology . Interrupting Rating (NEC 110-9).

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Presentation Transcript
slide1
SafetyBASICsTM

Fuseology

For Safety & Protection

Bussmann’s

Awareness of

Safety

Issues

Campaign

slide2
Available Short Circuit Current

Over Current Protection Device

Load to be Protected

Load Current

Safety BASICsTM

Fuseology

Interrupting Rating(NEC 110-9)

Safety & Protection

Reservoir Analogy

slide3
FAILURE of

Over Current Protection Device

Available Short Circuit Current

Short Circuit Current

Load (Equipment) Damaged,

Possible Personnel Injury

Safety BASICsTM

Fuseology

Interrupting Rating(NEC 110-9)

Safety & Protection

Reservoir Analogy

slide4
Available Short Circuit Current

Proper Operation of

Over Current Protection Device

If the device opens in less than 1/4 cycle it’s considered Current Limiting

Short Circuit Current

Safety BASICsTM

Fuseology

Current limitation(NEC 240-11)

Safety & Protection

Reservoir Analogy

slide5
Available Fault Current

Reduced Fault Current

Non-Current Limiting

Current Limiting

Safety BASICsTM

Fuseology

Current limitation(NEC 240-11)

Safety & Protection

A Current-Limiting Overcurrent Protection Device

slide6
Available Fault Current

Reduced Fault Current

Non-Current Limiting

Current Limiting

Safety BASICsTM

Fuseology

Current limitation(energy reduction)

Safety & Protection

  • Consider that:
    • Magnetic Forces -- varies with the square of the Peak Current
    • Thermal Energy -- varies with the square of the RMS Current
slide7
Reduced Fault Current

Current Limiting

Safety BASICsTM

Fuseology

Current limitation(ex.: LPJ_SP)

Safety & Protection

slide8
Example of Type”1”

Motor Starter protection

Safety BASICsTM

Fuseology

Component Protection

  • Type “1” protection allows for significant damage to motor starters requiring replacement. (similar to UL 508)
  • Type “2” coordinated “No Damage” protection provides for minimal damage and ability to reuse the starter.

Safety & Protection

slide9
Barrier, Wall or

Isle with an

Combination

obstruction

Controller

While this is not required (because the

Switch is

switch ahead of the controller can be

capable of

locked in the off position) it is

being locked

desirable for the situation where

in the open

someone accidentally gets “caught

position

up” in the motor/machine.

M

Supplementary Motor Disconnect

Safety BASICsTM

Fuseology

“Supplementary” Disconnecting Means

  • The disconnect at the controller may be difficult to quickly reach in an emergency

Safety & Protection

slide10
Safety BASICsTM

Fuseology

Definition -- “Selective Coordination”

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.

Safety & Protection

slide11
OPENS

OPENS

NOT AFFECTED

NOT AFFECTED

FAULT

FAULT

UNNECESSARY

POWER LOSS

Safety BASICsTM

Fuseology

Selective Coordination

Without Selective CoordinationWith Selective Coordination

Safety & Protection

slide12
Thermal Magnetic
  • MC Circuit Breaker
  • Time-Current Curve
  • Overload Region
  • Instantaneous Trip
  • Instantaneous Region
    • Unlatching Time
    • Interrupting Time
  • Interrupting Rating

Safety BASICsTM

Fuseology

Selective Coordination

Safety & Protection

slide13
Safety BASICsTM

Fuseology

Selective Coordination

Blackout Condition

  • 90A & 400A Molded Case Circuit Breakers
  • Inherent long delay between unlatching and interrupting due to mechanical means of breaking current
  • Upstream breaker can unlatch before the downstream breaker can clear the fault
  • Lack of Selective Coordination in the Short-Circuit Region

Safety & Protection

slide14
Insulated Case CB
  • 2000A Insulated Case Circuit Breaker
  • STD is an Option - allowing the breaker to delay opening
  • Instantaneous Override built-in: may be as low as 12X the breaker rating
  • Will often result in lack of coordination

Safety BASICsTM

Fuseology

Selective Coordination

Safety & Protection

slide15
Safety BASICsTM

Fuseology

Selective Coordination

Insulated Case CB

  • 2000A Insulated Case Circuit Breaker with Short Time Delay, Instantaneous Override and 100A Molded Case Thermal Magnetic Circuit breaker - NO Coordination in Short-Circuit Region (above 21,000A)

Safety & Protection

slide16
LV Air Power CB
  • Low Voltage Power Circuit Breakers
  • Short Time Delay - Allows the fault current to flow for up to 30 cycles.
  • Can be used to selectively coordinate with downstream devices.
  • Subjects equipment to high mechanical and thermal stresses, often violating 110-10.
  • High Cost, Larger

Safety BASICsTM

Fuseology

Selective Coordination

Safety & Protection

slide17
Safety BASICsTM

Fuseology

Selective Coordination

  • Fuses Coordinate in Overload AND Short-Circuit Regions
    • Overload - Time Current Curves
    • Short Circuit - Selectivity Ratio Guide (based on I2t)

Safety & Protection

slide18
Safety BASICsTM

Fuseology

Selective Coordination

  • Short Circuit Region
  • Coordination in the Overload region

Safety & Protection

slide19
Safety BASICsTM

Fuseology

Selective Coordination

  • Short Circuit Region
  • Selectivity Ratio
  • Guide (based on I2T)

Safety & Protection

slide20
Safety BASICsTM

Fuseology

Selective Coordination

Safety & Protection

Ratio Guide assures selective fuse coordination

slide21
Safety BASICsTM

Fuseology

Arch-Flash test set-up

Test conducted at the Paul P. Gubany Center for High Power Technology

Safety & Protection

slide22
Protected with a 601 Amp. Current Limiting Class L fuse.

(Slight splatter of molten metal)

Protected with a 1600 Amp. Non-Current Limiting Circuit Breaker set at 640 Amps. with short time delay of 12 cycles.

Safety BASICsTM

Fuseology

Benefits of “Current-Limitation”

*Tests with 22,600 Amperes of fault current

Safety & Protection

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