1 Scope
1.1 Description of Fuse Enclosure Packages Using
Current-Limiting Type Indoor Distribution and
Power Class Fuses
2 References
2.1 Referenced American National Standards
2.2 Other Referenced Standards
3 Background Information
4 Fuse Operation and Theory
4.1 Introduction
4.2 Thermal Characteristics
4.3 Interrupting Characteristics
4.4 Comparison of Power Fuses versus Distribution
Fuses
4.5 Comparison of Current-Limiting versus Expulsion
and Other Types of Non-Current-Limiting Fuses
4.6 Circuit Interruption and Recovery
4.7 Fuse Construction and Operation
5 Current-Limiting Fuse Types, Definitions, and
Classifications
5.1 Introduction
5.2 Fuse Class
5.3 Types of Current-Limiting Fuses
5.4 Current Rating Conventions
6 Application Considerations/Cautions
6.1 Electrical Aspects
6.2 Physical Application Considerations for
Current-Limiting Fuses
7 Current-Limiting Fuses Coordination
7.1 Tap-Line Coordination
7.2 Finding the Maximum Current Carrying Rating of
Current-Limiting Fuses (Reach)
7.3 Selecting Minimum Fuse Current Ratings
7.4 Time Margins Between Time-Current Characteristics
7.5 Coordinating Current-Limiting Fuses With Other
Protective Devices
7.6 Coordinating with Back-up Current-Limiting Fuses
7.7 Coordinating Current-Limiting Fuses with
Arresters
8 Bibliography and References
Figure 1: Typical CL Fuse
Figure 2A: Typical Minimum Melting Curves
Figure 2B: Typical Total Clearing Curves
Figure 3: Simplified Fault Current Circuit
Figure 4A: Low Arc Voltage and earc(t)
Figure 4B: High Arc Voltage and earc(t)
Figure 5A: Fault Circuit
Figure 6A: Load and Overload Circuit
Figure 5B & 6B: Voltage Drop Along Circuit When Current
Zero Is Reached
Figure 5C & 6C: Current Interruption and Recovery Voltages
Figure 7: High Current Operation of a Current-Limiting
Fuse, With Resulting Circuit Modification
Figure 8A: Symmetrical Short Circuit Current
Figure 8B: Asymmetrical Short Circuit Current
Figure 9: Operation of Commutating Current-Limiters
Figure 10: Typical CL Fuse
Figure 11: Construction Features Typical of Various
Types of CL Fuse Elements
Figure 12: Curves Comparing Three Different 40 Ampere
"E" Rated Fuses
Figure 13: Withstand Test Sequence
Figure 14: Reach Example
Figure 15: Block Diagram of Protection Scheme
Figure 16: CL - CL Example
Figure 17: CL - CL TCC Curve Example
Figure 18: CL Fuse - Expulsion Fuse Example
Figure 19: CL Fuse - Expulsion Fuse TCC Curve Example
Figure 20: Expulsion Fuse - CL Fuse Example
Figure 21: Expulsion Fuse - CL Fuse TCC Curve Example
Figure 22: Recloser CL Fuse Example
Figure 23: Recloser - CL Fuse TCC Curve Example
Figure 24: CL Fuse Recloser Example
Figure 25: CL Fuse - Recloser TCC Curve Example
Figure 26: Schematic of Motor Protection System
Figure 27: Matched Melt Coordination TCC Curve Example
Figure 28: Time-Current Curve Crossover Coordination
Example
Table 1: Comparison of ANSI Fuse Specifications
Table 2: Fuse Characteristics and Types of Fuses
Table 3: Maximum Permissible Overvoltages for
Distribution CL Fuses
Table 4: Nominal System Voltages, Motor and Fuse
Table 5: Multiplying Factors for Given Sequence
("K" factors)