Section 1 Introduction to the Presentation

Transcription

1 2007 Thomas & Betts

2 Section 1 Introduction to the Presentation Introduction of T&B Hi-Tech Fuses and our products Expulsion fuses vs. Current-Limiting fuses Hi-Tech s fuse construction & design features IEEE standards & testing requirements Fuse Application and Coordination

3 Section 2 Introduction to Hi-Tech Fuses & Hi-Tech s Products

4 Established in 1984, in Hickory, NC USA Recently acquired by Thomas & Betts (Aug. 2006) Focused exclusively on high-voltage, Current-Limiting fuse technology for power distribution system protection. Supplied well over 1 million fuses to the Utility Market Global leader in the Current-Limiting fuse market: Fuses sold in US, Canada, Latin America and Asia Leadership in IEEE/ANSI and IEC fuse standards bodies Award winning service levels (9 time ABB outstanding supplier of the year award winner) Active product development efforts ISO 9001:2000 certified

5 Current Product Lines Trans-Guard OS & OS Shorty (Oil-Submersible) Backup Type Current-Limiting fuses are primarily used with bayonet or protective (weak link) type expulsion fuses for "two-fuse" protection of distribution transformers. Trans-Guard EXT Trans-Guard EXT (External) Backup Type Current- Limiting fuses are primarily used for pole mounted transformer or capacitor protection in series with cutout expulsion fuses. Trans-Guard FX & SX (not shown) Full-Range Current-Limiting fuse provides both overload and fault protection for distribution equipment in a single fuse body.

6 Current Product Lines Fused Loadbreak Elbows Molded Fuse Canisters Molded CL Fuses

7 Trans-Guard OS & OS Shorty General: Oil-Submersible Backup Type Current-Limiting fuses primarily used with bayonet or protective (weak link) type expulsion fuses for "two-fuse" protection of distribution transformers. Application:! Pad mounted distribution transformers! Pole-mounted transformers Other Brands:! Cooper ELSP! GE OSP Advantages:! Highest ratings in a single fuse body available (less paralleling)! Shorter or smaller diameter! Tested to applicable standards

8 Trans-Guard OS Application Trans-Guard OS fuses installed in a 3-Phase distribution transformer

9 Trans-Guard EXT General: External Backup Type Current-Limiting fuses are primarily used for pole mounted transformer or capacitor protection in series with cutout expulsion fuses. Application:! Pole-mounted distribution transformers! Capacitors Other Brands:! Cooper NX Companion! GE ETP! AB Chance K-mate Advantages:! Lowest I 2 t let-throughs! Robust and durable design! Highest ratings available

10 Trans-Guard EXT Applications For use in high available fault current areas including:! Pole-mounted transformers! Overhead capacitors! Riser pole applications Trans-Guard EXT w ith cutout fuse Trans-Guard EXT w ith Pole-mounted Transformer Trans-Guard EXT w ith capacitor

11 Trans-Guard FX General: Full-Range Current-Limiting fuse provides both overload and fault protection for distribution equipment in a single fuse body. Application:! Distribution transformers (in dry-well canisters)! Switchgear (clip-mounted) Advantages:! Sealed design! Damage Sensor! Tested to latest standards (includes RMAT testing) Other Brands:! Cooper NX, ELX, & X-Limiter! Eaton CX

12 Trans-Guard FX Applications! Installed in dry-well canisters for oil filled transformer and oil/sf 6 switchgear protection.! Clip mounted in live-front switchgear and/or dry-type transformers! Externally mounted on overhead distribution systems. Trans-Guard FX in a clip mounting Trans-Guard FX with a dry-well canister

13 Trans-Guard SX General: Under-oil Full-Range Current-Limiting fuse provides both overload and fault protection for underground cables and distribution equipment in a single fuse body. Target Market:! Utilities! Switchgear! Manufacturers! Industrial Application:! Switchgear (in wet-well canisters) Other Brands:! Cooper SX-Limiter & ELSG! AB Chance SL

14 Trans-Guard SX Applications! Installed in wet-well canisters in switchgear

15 Elastimold Products General: Rubber encapsulated Full-Range Current-Limiting fuse provides dead-front overload and fault protection for distribution equipment in a single fuse body. Application:! Underground vaults! Dead-front transformers & switchgear

16 Section 3 Expulsion Fuses vs. Current-Limiting Fuses

17 Two Main Types of Fuses All fuses, after melting with an overcurrent, contain an arc that carries the current until interruption. Fuses can be categorized into two main types, depending on how they interact with relatively high fault currents: 1) Non Current-Limiting Fuses 2) Current-Limiting (CL) Fuses

18 1) Non Current-Limiting (Current zero awaiting) Does not introduce significant resistance into the circuit after melting. Requires natural current zero for interruption. Types: Expulsion fuse, vacuum fuse, sf 6 fuse (expulsion fuses are the most common)

19 Common types of Expulsion Fuses Power Fuse Cutout Expulsion Fuse Bayonet Expulsion Fuse

20 Role of Expulsion Fuses Very effective at interrupting low fault currents Some types can minimize the risk of equipment failure due to overloading Economical replacement Provide a variety of time-current curve (TCC) characteristics High continuous current ratings are available

21 Expulsion Fuse Selection (Choosing Type) Types of Bay-O-Net Fuse Available Manufacturer* " Current Sensing (fault sensing) C, A, E " Dual Sensing (load sensing) C, A, E " Dual Element C, A, K " High Ampere Overload C *C = Cooper (RTE ), A = ABB, E = ERMCO (GE), K = Kearney

22 2) Current-Limiting (Current zero shifting) Introduces significant resistance into the circuit after melting. At high current, forces early current zero. Types: Current-Limiting (CL) Fuse, Fault Limiter (CL fuses are the most common)

23 Types of Current-Limiting Fuses Full-Range Fuse External Fuse and Oil- Submersible Fuse

24 Role of Current-Limiting Fuses Minimizes the risk of eventful/catastrophic failure of distribution equipment by limiting the peak current and the energy let through during a fault Protects distribution equipment especially in areas where available fault currents exceed interrupting capabilities of other protection devices Addresses concerns for potential fire hazards (e.g. grassy areas) or safety issues associated with populated areas where expulsion gases are not acceptable Enhances overall power quality by reducing blink time to fractions of a cycle Improves coordination with source side devices (coordination up to 50kA) Alleviates concerns for loud noise ( bang ) during fuse operation

25 Three classes of CL fuse: How well Current-Limiting fuses handle low currents divides them into three classes: Backup General-purpose Full-Range

26 Backup Current-Limiting Fuse A fuse capable of interrupting all currents from the rated maximum interrupting current down to the rated minimum interrupting current.

27 1000s Backup Fuse TCC Time OK NO OK.01s Current Rated current - I R Minimum I/C Maximum - 50kA Fuses cannot interrupt, or may be damaged by, currents in the red zone

28 General-purpose Current-Limiting Fuse A fuse capable of interrupting all currents from its rated maximum interrupting current down to the current that causes melting of the fusible element in no less than 1 h.

29 General-Purpose TCC 1 Hour OK OK Time NO Rated current - I R Current Maximum - 50kA Fuses cannot interrupt, or may be damaged by, currents in the red zone

30 Full-Range Current-Limiting Fuse A fuse capable of interrupting all currents from it s rated interrupting current down to the minimum continuous current that causes melting of the fusible element(s), with the fuse applied at the rated maximum application temperature specified by the fuse manufacturer.

31 Full-Range Fuse TCC o o 25 O is RMAT 10,000s 1 Hour OK Time.010s I R I R Current 50kA 25 Fuse is not damaged by overloads, and can clear any current that causes it to melt with surrounding temperatures to O

32 Two Important Full-Range Fuse Concepts 1. Fuse can clear any current that melts it (At ambient temperatures up to its Rated Maximum Application Temperature - RMAT) 2. Fuse is not damaged by overloads, up to the current that causes it to melt ( self-protecting ).

33 Fundamental Differences Between Non Current-Limiting Fuses (Expulsion Fuses) & Current-Limiting Fuses

34 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction

35 How an expulsion fuse works: An expulsion fuse uses a short element When the element melts, a low resistance arc produces gas from the fuse liner An expulsion action blows the ionized gas out of the fuse At a current zero, if the gap is sufficiently de-ionized, arcing ceases

36 Expulsion Fuse Design Common designs Cutout fuse Bayonet fuse Short Fuse Element Gas Evolving liner After melting, arc produces low resistance Expulsion Action

37 How a Current-Limiting fuse works: at high fault currents: A Current-Limiting fuse uses a long element e.g. 3 (1meter) for a 15.5kV fuse. When the element melts, multiple series arcs are produced. Long elements are wound on an Inert core Restrictions initiate arcing

38 Current-Limiting Fuse Design At high currents, restrictions melt simultaneously (introducing resistance) PUNCHED ELEMENT Continued arcing causes the arcs to lengthen (resistance increases) FILLER Eventually the whole element is consumed

39 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction 2. Current Interruption

40 Expulsion Fuse - Current interruption Fuse Melting Current peak Current interruption Prospective Fault Current Fuse Current

41 Current-Limiting fuse - Current interruption Fuse Melting Current peak Current interruption Prospective Fault Current Fuse Current

42 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction 2. Current Interruption 3. Energy Let-through

43 Current let-through Expulsion Fuse 10,000A rms Symmetrical Prospective Current 25,000A Current-Limiting Fuse 7,000A Energy i 2 dt (i 2 t)

44 What is I 2 t (! i dt)? 2 R r time = t i heat = i 2 R t + i 2 r t so, i 2 t a energy

45 Illustration of I 2 t ( Fault Current 5000A rms. symmetrical I! 2 i dt) Reduction using CL Fuse rms First loop 870,000 A 2 -sec. Peak current 12kA I I 2 t is proportional to the volume of the box I i rms t T t T I 2 t let-through by Hi-Tech 80A = 31,000 A 2 -sec. (<4%) Peak current 5 ka (41%)

46 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction 2. Current Interruption 3. Energy Let-through 4. Peak Current Let-through

47 Peak Let-Through Curves 100K Peak current of asymmetrical fault Peak Current 25K 10K 7K Peak current of CL fuse 25,000A 7,000A 2.5K 1K 1K 10K 50K 100K Prospective Fault Current Amps rms symmetrical Prospective Current 10,000A Symmetrical

48 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction 2. Current Interruption 3. Energy Let-through 4. Peak Current Let-through 5. Sensitivity to Circuit & Fault Conditions

49 Prospective Fault Current (as a function of point on wave) X/R >15 Asymmetrical Current Symmetrical Current Voltage The point-on-wave where fault occurs affects asymmetry

50 Expulsion Fuse Operation at High Currents Current MELTING Expulsion fuses are sensitive to circuit X/R (fault offset) Fuse waits for current zero No significant arc voltage before current zero Voltage Expulsion fuses are sensitive to circuit Transient Recovery Voltage TRV

51 Current-Limiting Fuse Operation at High Currents Current Significant Current-Limiting action MELTING Voltage Significant arc voltage (result of current-limiting action) Current-Limiting fuses are quite insensitive to TRV and X/R

52 Expulsion Fuse Operation at Low Currents System Voltage Fuse Voltage Fuse Current Melt

53 Backup Current-Limiting Fuse Operation at Low Currents Current switching between multiple elements Voltage Current Melt

54 Fundamental Differences Between Expulsion Fuses and Current-Limiting Fuses 1. Construction 2. Current Interruption 3. Energy Let-through 4. Peak Current Let-through 5. Sensitivity to Circuit & Fault Conditions 6. Performance at Various Fault Current Levels

55 Expulsion Fuses " Must wait until a current zero to interrupt " Interruption occurs when withstand voltage exceeds recovery voltage Expulsion fuses cannot interrupt at high currents because the voltage withstand never exceeds the recovery voltage. They therefore have a maximum interrupting current

56 Backup CL Fuse - element melting = Restriction melting High current Low current Minimum I/C all restrictions melt insufficient restrictions melt sufficient restrictions melt Fuse interrupts current Fuse does not interrupt current Fuse interrupts current Backup CL fuses cannot interrupt currents less than their minimum interrupting current

57 Section 4 Hi-Tech s Fuse Construction & Design Features

58 Machined brass caps Construction of a Hi-Tech Fuse Low current section (FX Only - includes patented Damage Sensor ) High current interruption element Resin-rich filament wound glass/epoxy body Compacted quartz sand Welded element joints Epoxy joint Soldered electrical connection and sealing

59 OS & OS Shorty Features A. Cost advantages:! In some applications a single fuse can be used, where parallel fuses would normally be used! Minimize the need and extra costs associated with using parallel fuses B. Shorter overall lengths:! In many cases, OS Shorty fuses will be shorter or smaller in diameter than the alternative. C. Compliance with industry standards:! All OS designs have been tested to the applicable IEEE (ANSI) and IEC standards.

60 Trans-Guard EXT Features A. Significant design advantages:! EXT fuses have the lowest let-through energy (I 2 t) levels in the industry minimizing the potential for distribution equipment damage.! Durable design with machined brass end-caps and acrylic paint coating for minimized UV degradation.! Largest current ratings available in the industry (65K, 80K and 100K) B. Wide industry acceptance:! Our EXT fuses are approved and widely used throughout the US utility market.

61 Trans-Guard FX Features A. Sealed design:! Ensures no gases are discharged during operation! Prevents eventful failure due to leaking dry-well canisters B. Patented damage sensor :! Significantly reduces the risk of fuse failure should a current surge damage the fuse elements C. Commitment to compliance with industry standards:! All FX designs have been tested to the most current IEEE (ANSI) and IEC standards which includes short circuit testing at elevated temperatures (RMAT of 140 C for 2 fuses and 71 C for 3 fuses ). D. Low current element in center of fuse:! Eliminates the risk of fuse overheating in the MCAN or other types of enclosures E. Rugged machined end caps:! Results in less distortion and secure attachment in dry-well canisters

62 Damage Sensor Reason for the Damage Sensor A concern that: If a surge damages, but does not fully melt, a Full-Range fuse s (high current) ribbon element(s), the element(s) may subsequently melt with a current too low for the high-current element(s) to be able to interrupt.

63 - how it works FX Full-Range Fuse Damage Sensor high current section low current section high current section tin Damage Sensor time in seconds.010 low current section damage sensor current in amperes high current section

64 Damage Sensor e D 1. The whole of the fuse s melting TCC is generated in the low current section 2. A surge that could damage the ribbon element will melt, or damage to a greater extent, the damage sensor 3. If the damage sensor subsequently melts at a low current, the low current section can interrupt it.

65 Non Hi-Tech Design End Cap Comparison FX Machine Design

66 Blown Fuse Indication Note: This is not available for dry-well canister applications Fuse Indicator - before operation Fuse Indicator - after operation

67 Trans-Guard SX Features A. Patented damage sensor :! Significantly reduces the risk of fuse failure should a current surge damage the fuse elements B. Commitment to compliance with industry standards:! All FX designs have been tested to the most current IEEE (ANSI) and IEC standards which includes short circuit testing at elevated temperatures (RMAT of 140 C for 2 fuses and 71 C for 3 fuses ).

68 Section 5 IEEE/ANSI Standards & Testing Requirements

69 Latest Applicable IEEE/ANSI Standards IEEE C IEEE Standard Service Conditions and Definitions for High-Voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories IEEE C IEEE Standard Design Tests for High-voltage Fuses, Distribution Enclosed Single-Pole Air Switches, Fuse Disconnecting Switches, and Accessories ANSI C Specifications for distribution fuse disconnecting switches, fuse supports, and Current- Limiting fuses IEEE C IEEE Guide for Application, Operation, Classification, Application, and Coordination of Current-Limiting Fuses with Rated Voltages 1-38kV

70 Definitions 1. Rated Continuous Current - a current they can carry continuously without damage 2. Rated Maximum Voltage - the maximum voltage against which they are capable of interrupting current 3. Rated Maximum Interrupting Current - the maximum current they are capable of interrupting 4. Rated Minimum Interrupting Current for a backup fuse, the lowest current the fuse has been shown to be able to interrupt 5. Rated Maximum Application Temperature - the maximum application temperature at which the fuse is suitable for use

71 General Test Requirements I 1 Testing - I 2 Testing - I 3 Testing - RMAT Testing - TCC Testing - At the Rated Maximum Interrupting Current At current where approximate maximum arc energy is absorbed by the fuse At the Rated Minimum Interrupting Current for a backup fuse or at the lowest current that can cause melting for a Full-Range fuse Repeating of some of the tests above at the the Rated Maximum Application Temperature Testing in the take-over region where current interruption transfers from the low current element to the high current element (Full- Range only!)

72 Section 6 Application & Coordination

73 Coordination of Expulsion Fuse and Backup CL Fuse Hi-Tech Fuses Application Guide FS-10 This generally follows recommendations in IEEE Std.C37.48 TM application guide. Conservative recommendations.

74 Relative Fuse Characteristics Fuse Type Expulsion Fuse Backup CL Fuse Interrupting Rating Poor Excellent Low Current operation Excellent Poor

75 Two ways to get Full-Range protection Combining a Backup Current-Limiting Fuse with a series Expulsion Fuse Full-Range Fuse c

76 Selecting Oil-Submersible Backup Current-Limiting Fuse with Series Expulsion Fuse

77 Coordination of Expulsion Fuse and Backup CL Fuse: There are two types of coordination recommended by the IEEE (Standard C37.48). 1) Time-current Curve Crossover Coordination (TCC) 2) Match-melt Coordination

78 Requirements Needed to Select Fusing Transformer KVA Primary Voltage Impedance Expulsion Fuse Connection

79 Selecting an Expulsion Fuse Meeting Temporary Surge Requirements The expulsion fuse minimum melt curve should be to the right of the following points: INRUSH: COLD LOAD PICKUP: 12 x IR at 0.1 sec. 25 x IR at 0.01 sec. 3 x IR at 10 SEC. 6 x IR at 1 SEC. Where IR = transformer rated current

80 Time (sec) 10 1! Inrush/cold load pick-up points!! Expulsion Fuse Minimum Melting TCC 0.1! 0.01! ,000 Current in Amperes rms Symmetrical

81 Selecting an Expulsion Fuse Overload Requirements The fuse must be able to carry the maximum transformer load current (including acceptable overload) without melting. Protective weak link, and Current Sensing bayonet fuses are typically picked to melt at 300% - 400% I R in 300 sec. (600 sec. for fuses rated over 100A). Dual Sensing, Dual Element and High Ampere fuses respond significantly to transformer oil temperature. They provide transformer overload protection, and typically allow 200% I R for 2 hours, and 160% I R for 7 hours.

82 Selecting the Backup Fuse Basic Principles of TCC Coordination: 1) Each fuse must protect the other in its region of non-operation 2) Operation of the expulsion fuse must not melt or damage the backup fuse (when there is no fault inside the transformer) 3) Transformer overload must not damage the backup fuse by exceeding its maximum continuous current rating

83 Region where the CL fuse cannot interrupt Expulsion Fuse Total Clearing TCC CL Fuse Minimum Melt TCC Requirement 1 Region where the expulsion fuse cannot interrupt T i m e Min I/C CL Fuse Current 50kA Max I/C Expulsion Fuse

84 Requirement 2 & 3-25% Margin 100% 120% Check Bolted Secondary Fault Current Expulsion Fuse Total Clearing Curve CL Fuse Minimum Melt Curve CL Fuse No-damage Curve Check Check Coordination Area 80% 100%

85 Sample Coordination Tables 500 KVA CURRENT SENSING 353C GRDY-GRDY Transformers - CL Fuse L-N Rated (w here possible) Trans-Guard OS "Shorty" (HTSS------) Voltage L-L Link Cat # CL Fuse Minimum Impedance Alternatives Minimum Impedance Alternatives Minimum Impedance C12 4.2% 2.2% C12 4.1% 2.1% C12 3.8% 2.0% 500 KVA CURRENT SENSING 353C Delta Connected Transformers Trans-Guard OS "Shorty" (HTSS------) Voltage L-L Link Cat # CL Fuse Minimum Impedance Alternatives Minimum Impedance Alternatives Minimum Impedance C12 4.2% 2.6% C12 4.1% 2.5% C12 3.8% 2.4%

86 Basic Principles of Match-melt Coordination: 1) Each fuse must protect the other in its region of non-operation 2) Operation of the expulsion fuse must not melt or damage the backup fuse (when there is no fault inside the transformer). 3) Transformer overload must not damage the backup fuse by exceeding its maximum continuous current rating. 4) Backup fuse must always let through enough energy to cause the expulsion fuse to melt open

87 Done by comparing I 2 t of fuses What is I 2 t ( i 2 dt)? R! time = t i heat = i 2 R t so, i 2 t a energy

88 Requirement 4 2 x minimum melt I 2 t of the backup fuse must be greater than or equal to the maximum melt I 2 t of the expulsion fuse. Current MELTING Main benefit of match-melt coordination is that voltage stress is removed from the backup fuse after interruption

89 Requirement 4: How to Calculate 2 x minimum melt I 2 t of the backup fuse must be greater than or equal to the maximum melt I 2 t of the expulsion fuse. Minimum Melt I 2 t of backup fuse Published Value Maximum Melt I 2 t of expulsion fuse Must calculate from expulsion fuse curve Typically done using the following equations I.025sec x 1.2 = I max. melt (I max-melt ) 2 x.025sec = Max. Melt I 2 t (From min-melt TCC)

90 Fuse Voltage Rating Single Phase Transformers: Fuse voltage rating " maximum applied (L-N) voltage Three Phase Transformers: - For GndY-GndY connected transformers having less than 50% delta connected load Can typically use L-N rated fuses - For all other connections (i.e. delta connections) L-L rated fuses are typically required

91 Exception When match-melt coordination is used: It is usually possible to use L-N rated backup fuses and L-L rated expulsion fuses This makes it possible to fuse delta connected transformers having primary voltages as high as 34.5kV

92 Selecting External Backup Current-Limiting Fuse with Series Cutout Fuse

93 Selecting a Trans-Guard EXT Fuse EXT s have been rated to match-melt coordinate with a cutout having the same rating This means that the backup fuse always allows enough energy through during a fault to cause the cutout fuse to drop open This removes voltage stress from the backup fuse & provides visual indication of where the fault occurred

94 Selecting a Trans-Guard EXT Fuse Must always be coordinated with a series connected cutout expulsion fuse Select Voltage Rating Rated Maximum Voltage of the fuse must be greater than the maximum system L-N voltage Select Current Rating K rating of backup fuse must be greater than or equal to the K rating of the cutout fuse Select Hardware Configuration

95 Trans-Guard EXT Hardware Standard and Offset stud Integral Eyebolt Spade Parallel Groove Connector Loose Eyebolt Universal Adaptor

96 Selecting Full-Range Current-Limiting Fuses

97 Selecting a Full-Range Fuse Meeting Temporary Surge Requirements The expulsion fuse minimum melt curve should be to the right of the following points: INRUSH: COLD LOAD PICKUP: 12 x IR at 0.1 sec. 25 x IR at 0.01 sec. 3 x IR at 10 SEC. 6 x IR at 1 SEC. Where IR = transformer rated current

98 1000 Full-Range CL Fuse Minimum Melting TCC 100 Time (sec) 10 1! Inrush/cold load pick-up points!! 0.1! 0.01! ,000 Current in Amperes rms Symmetrical

99 Selecting a Full-Range Fuse Overload Requirements The fuse must be able to carry the maximum transformer load current (including acceptable overload) without melting. Full-Range fuse are typically selected to allow between % I R or % I R. NOTE: The Fuse s Melting Time-Current Curve will shift to the left with increasing oil temperature.

100 Derating of FX fuses There are certain conditions that will cause: The fuse melting characteristics move to the left (on the TCC) The fuse s continuous current to decrease Note that an FX fuse maximum continuous current rating is related to its melting TCC it is 95% of the minimum fusing current (The minimum fusing current is the lowest current that melts a fuse at a particular ambient temperature, including manufacturing tolerances)

101 Derating Factors There are two factors to consider: 1. Derating for the fuse being in an enclosure (FEP) 2. Derating with an increase in Surrounding Temperature (Ambient temperature)

102 Derating due to use in a Drywell Canister Submerged in Oil Reduction of 2.0% Example: Lowest current to melt a 30A FX fuse, in canister at 25 0 C I = lowest current to melt fuse at 25 o C... I Air = 43 A I Canister = 43A x 0.98 = 42.3A (From min-melt TCC)

103 Derating due to Elevated Surrounding Ambient Temperature Reduction of 0.2 % per degree C over 25 0 C Example: Lowest current to melt a 30A FX fuse, in oil at C I 25Canister = 42.3 A 100 o - 25 o = 75 o 75 o x 0.2% = 15% 100% - 15% = 85% (0.85) I q = lowest current to melt fuse at q o C... I 100 = 42.3A x 0.85 = 36A

104 Fuse Voltage Rating For single phase applications: The Rated Maximum Voltage of the fuse must be greater than the maximum system L-N voltage For three phase applications: The Rated Maximum Voltage of the fuse should typically be greater than the maximum system L-L voltage (some exceptions apply)

105 Selecting an Elastimold Fuse Select Voltage Rating For single phase applications: The Rated Maximum Voltage of the fuse must be greater than the maximum system L-N voltage For three phase applications: The Rated Maximum Voltage of the fuse should typically be greater than the maximum system L-L voltage (some exceptions apply) Select Current Rating Use continuous current rating Must consider derating due to elevated temperatures

106 Derating due to Elevated Surrounding Ambient Temperature Reduction of 0.2 % per degree C over 25 0 C Example: Lowest current to melt a 10A Elbow fuse at 65 0 C 65 o - 25 o = 40 o 40 o x 0.2% = 8% 100% - 8% = 92% (0.92) I q = lowest current to melt fuse at q o C... I 25 = 15 A I 65 = 15A x 0.92 = 13.5A (From min-melt TCC)