AF Solutions

V ESW Brasil 2011 Seminrio Internacional de Engenharia

Eltrica na Segurana do Trabalho

So Paulo 8 a 10 de novembro Holiday Inn Parque Anhembi

Innovative Techniques for

Mitigating Arc Flash Exposure

David Shipp

Eaton Corporation Electrical Sector

2011 IEEE The Institute of Electrical and Electronics Engineers, Inc. - Industry Applications Society - South Brazil Section

ABSTRACT

As more and more industry addresses arc flash electrical

safety concerns, they are discovering high risk associated with

what used to be normal maintenance tasks. In many cases,

the excessively high arc flash incident energies make it so all

maintenance must be done with equipment de-energized not always acceptable to the process industries. This paper will

address the multiple ways the authors have devised to

significantly lower arc flash incident energy exposure by new

system design and products, retrofits, retro-fills, equipment

modifications, alternate protection settings, etc. In most

cases, NFPA 70E Hazard Risk Category 2 or lower can be

obtained. Several real world examples will be discussed.

.

2


DEVELOPMENTS LEADING TO NFPA 70E

Large Hydro in Pacific NW

6.9kV Switchgear

Racking in Breaker

AF occurred

One worker injured

4+ years, $10+ million

3


NFPA 70E METHODS FOR SELECTING

PROTECTIVE CLOTHING AND PPE

NFPA 70E-2004 Table 130.7(C)(11) Protective Clothing Characteristics

Hazard Risk

Category

Clothing Description (Typical number of clothing layers is given in parenthesis)

Required Minimum Arc Rating of PPE [J/cm2(cal/cm2]

0

Non-melting, flammable materials (i.e., untreated cotton, wool, rayon, or silk, or blends of these materials) with a fabric weight at least

4.5 oz/yd2 (1)

N/A

1 FR shirt and FR pants or FR coverall (1) 16.74 (4)

2 Cotton underwear conventional short sleeve and brief/shorts, plus FR shirt and FR pants (1

or 2) 33.47 (8)

3 Cotton underwear plus FR shirt and FR pants

plus FR coverall, or cotton underwear plus two FR coveralls (2 or 3)

104.6 (25)

4 Cotton underwear plus FR shirt and FR pants

plus multilayer flash suit (3 or more) 167.36 (40)

4

2011 IEEE The Institute of Electrical and Electronics Engineers, Inc. - Industry Applications Society - South Brazil Section 5

INTRODUCTION

Too Much PPE is Just

as Bad as Not Enough!


PROTECTIVE CLOTHING AND PPE FOR

ARC FLASH

Multi-Layering Testing

6


Specialized Arc Flash Protective Equipment

Flash Suits / Switching Coats

Two-Layer Flash Suit,

ATPV = 42 cal/cm2

Use: Hazard/Risk Category 4

PROTECTIVE CLOTHING AND PPE FOR

ARC FLASH

7


REDUCING ARC FLASH HAZARDS

Need a Total System

Solution Approach

8


SOLUTIONS THAT REDUCE ARC

FLASH INJURIES AND DAMAGE

Label Equipment & Train Personnel

Minimize Risk with Good Safety Practices

Reduce Available Fault Current

Faster Clearing Time

Move People Further Away

Redirect Blast Energy

Prevent Fault

9


ARC FLASH SOLUTIONS

Bypass Isolation A.T.S. Arc Flash Reduction Maintenance

System for new and old (Retrofit

Kits) installations (LV and MV)

Arc Resistant MV Motor Starters MV and LV Arc Resistant Switchgear Bus Differential Schemes MV and LV Zone Selective

Interlocking

Current Limiting Reactors LV/MV Remote Racking Hi (or Low) Impedance Transformers MV / LV HRG Systems AF Power System Studies Insulated Bus in Switchgear

Infra-Red Windows Kirk Key Interlock Systems MCC Bucket & Safety Switch Viewing

Windows MCC Bucket Retrofits Partial Discharge Systems Infra-Red Sensors in Hi AF Areas

(Dont Have to Remove Covers) AF Tested Current-Limiting MCCBs Remote Monitoring, Control and

Diagnostics LV/MV Remote Operators Arc Mitigator Light Detection

Tripping (MV and LV) AFL System (No Main 2ndary

Breaker)

Examples of Arc-Flash Solutions:



Label Equipment

Train People

Wear PPE

11


Engineering Studies Arc Flash Analysis

Arc Flash Studies Standardized Data Collection

Templates

Power Systems Engineers

Labels, Training,

Recommendations

12


Provides guidance for the calculation of incident energy and arc flash protection

boundaries.

It presents formulas for numerically quantifying these values.

The IEEE 1584 Guide also includes an Excel Spreadsheet Arc-Flash Hazard Calculator which performs the actual calculations using the formulas stated

in the Guide.

13

IEEE 1584-2002: Guide for Performing Arc Flash Hazard Calculations


Personal Protective Equipment (PPE)

Cumbersome Hot Reduces Mobility Increases Fatigue

14


Arc-Flash Safety for electricians, technicians or equipment operators whose employers have

already declared them to be "qualified" according

to OSHA rules but need to be recycled or be

updated with any new revision of NFPA 70E

Electrical and Arc-Flash Safety for electricians, technicians and equipment operators who are not

"qualified" but who might be exposed to arc-flash

hazards

Understanding Arc Flash for engineers, safety managers, consultants and electricians

15

Recommended Training



De-Energize Equipment versus Working It Live unless increased hazards exist or infeasible due

to design or operational limitations.

Switching remotely (if possible)

Closing and tightening door latches or door bolts before operating a switch.

Standing to the side and away as much as possible during switching operations.

16

Practical Methods for Reducing

Arc Flash Hazards



Bad Exposed Back of Neck Good All of Body Protected

Practical Methods for Reducing

Arc Flash Hazards


INTRODUCTION

18


Reduce Available Fault Current

(Reduce Incident Energy)

Reducing Arc Flash Hazards


Lowering Isc Does not Always Lower Incident

Energy

Fuse vs Breaker

No 1 Single Answer

Must Do Arc Flash Study

Reducing Incident Energy


HRG Units

Typically Under 5 Amps

Pulsing Contactor

Many Options

LV or MV

Does Not Preclude PPE

Lowers Probability of Accident

22

High Resistance Grounding (HRG)


Faster Clearing Time

(Reduce Incident Energy)

Reducing Arc Flash Hazards


Neither circuit breaker calculation method accounts for

their current-limiting effects.

Neither based on any actual circuit breaker test data.

SIMPLE method is based upon worst case time of 4 manufacturers time/current curves. VERY conservative!

ALTERNATE method requires

manufacturer specific time/current curve

input.

Concerns with ALTERNATE method too because circuit

breaker time/current curves are very conservative in their

instantaneous region.

24

LV Circuit Breakers Issues with IEEE 1584


MCCBs Arc Flash Performance Comparison

Apply Current-Limiting Molded-Case Circuit Breakers

Min Mid Max

225 A MCCB with Thermal-Magnetic Trip Unit

Bolted fault current 3.4 kA 35 kA 100 kA

Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm2) N/A

1 1.7 4.7

Inc. Energy via IEEE 1584 & Trip Curve (Cal/cm2) 59.6 1.1 2.3

Measured Incident Energy (Cal/cm2) 0.08 0.1 0.11

1200 A MCCB with Electronic Trip Unit

Bolted fault current 20 kA 35 kA 100 kA

Inc. Energy via IEEE 1584 Table E.1 Generic (Cal/cm2) N/A

1 3.5 9.4

Inc. Energy via IEEE 1584 & Trip Curve (Cal/cm2) 218 3.5 5.8

Measured Incident Energy (Cal/cm2) 1.86 1.2 1.64

Incident Energy at

Bolted Fault Current

IEEE 1584 Generic Equation

IEEE 1584 Using Time Current Curve Input

Tested Value

1 N/A = Not Applicable

because it is outside the

range of the IEEE 1584

Generic Equation


This is only a first step in making MCCB recommendations for arc flash applications.

It is much easier for novice users to understand the needed PPE, rather than a

caloric energy value.

Its important and necessary to have arc flash application recommendations for MCCBs.

26

Comments about MCCB Application Arc Flash Performance


Zone Selectively Interlocked LV Power Circuit Breakers

provide significantly lower Arc Flash energy values:

Testing confirms that a LV Power Circuit Breaker

(4000A maximum) require Category 2 PPE (8 cal/cm2)

with proper instantaneous settings

During maintenance it is recommended to temporarily adjust

the Instantaneous and Ground Fault (if available) trip

settings to their lowest value

Unless a Low Voltage Power Circuit Breaker

operates in the Instantaneous trip mode, the

arc flash energy values will require Category

3 PPE or greater

27

LV Power Circuit Breakers


Bus Differential (87B)MV or HV

Zone Selective Interlocking a Control approach / Form of 87B MV and LV

Arc Mitigator Light (Current) Detection Systems for MV and LV Switchgear and

Controlgear

Current Limiting Fuses*

28

High Speed Clearing


SD=

0.5S

SD=

0.3S

SD=

0.3S

SD=

0.3S

M1

F1 F2 F3 X

35kA fault current

Without ZSI = 0.5 S:

43.7 Cal/cm2

Greater than Cat. 4 PPE

DANGER!

With ZSI = 0.08 S:

7.0 Cal/cm2

FR Shirt & Pants

Cat. 2 PPE

29

Zone Selective Interlocking (ZSI)

Explanation:


An Off-Shore Oil Platform in the Gulf of Mexico lowered their Incident Energy Exposure from

85 calories down to 12.7 calories by retrofitting

their 480 V Switchgear with ZSI.

30

Zone Selective Interlocking (ZSI)

Example:


Door Mounted Components

Breaker Mounted Components

Arc flash Reduction

Maintenance System

DIGITRIP

Harness

Lockout

Switch

Battery

Indicating

Light

31

Arc Flash Reduction Systems Retrofit of LV PCBs


An external over-ride switch and circuitry are

connected to a breakers trip unit, and is adjustable between 2.5X - 10X.

When a person wants to perform maintenance,

they close the switch, which automatically over-

rides all of the delay functions, and causes the

breaker to trip without any intentional delay

whenever a fault is detected. Use its lockout

features for normal lockout tag-out procedures.

32

Arc Flash Reduction Systems Retrofit of LV PCBs


Upon completion of the maintenance, the lock is

removed, the switch is manually opened, and all

previous trip unit settings are again re-activated,

without need for recalibration.

33

Arc Flash Reduction Systems

for LV PCBs


Overflow Sump Pump Location

Recommendation (Acceptable)

C0-5: XFMR protection Main and FDR: Coordination

Hazard Risk Category

= HRC = Danger (>40 Cal.)

AF Current = 5.6kA

34

Example: Existing Equipment


Overflow Sump Pump Location

Recommendation (Good)

C0-5: TXMR protection Main and FDR: Coordination New Equipment (Better)

Replace C0-5 w/ DT3000 Replace FDR trip w/ DigiTrip RMS 610, LSI trip unit.

Arc flash Reduction System (Best)

Replace C0-5 w/ DT3000 Replace FDR trip w/ DigiTrip RMS610, LSI trip unit & Arcflash Reduction

Maintenance Switch.

Replace Main with Digitrip 610 LS & Arc flash Reduction Maintenance Sw.

HRC = 1 (< 4 cal/cm2) AF Current = 5.6kA 35

Arc Flash Reduction Systems Example


High Avail Fault Current

Digitrip610 & Arc flash Reduction System

Normal settings HRC=3 (10.7 cal)

With Arc flash Reduction System: HRC= 1 (2.2 cal)

36

Arc Flash Reduction Systems Example for High Available Fault Current


2000 A fuses supplying 480V Glass Furnaces

Incident Energy =61 Cal / HRC=Danger

Retro-filled fuses with LV Power Circuit Breakers

35 cal with trip Unit/6 cal with New Breaker + Built-in Arc

Flash Reduction System

37

Arc Flash Reduction Systems Retro fill Example


Arc Flash Reduction Systems Example of replacement of old LVPCB


Has 5 user-selectable levels of protection to choose

maximum protection, while

avoiding nuisance tripping

Blue color LED indicating Maintenance mode

Can be remotely activated through IR communication

with PDA

39

Arc Flash Reduction Systems Example of Integrated Trip Unit


Computer Room PDU (Bypass Mode)

Thermal-Magnetic breaker HRC = 4 Due to Long Time

Replaced with Electronic Trip Breaker HRC = 1

40

Change to Electronic Trip Units


Multiple Settings Groups

Similar to LV maintenance

switch, only for MV applications

Used to reduce the trip delay of

medium-voltage relays while

maintenance is being performed

on equipment.

Requires relay with multiple

settings groups capability

41

Practical Methods for Reducing Arc

Flash Hazards


Switch

Indicating Light

m-Processed

Relay

42

Arc Flash Reduction using m-Processed Relay with Group Settings


Network Protectors


Any Exposure / Racking Feeder Circuit-Breakers Must be Cleared by Primary

Fuse

100 Cal Exposure

50

Substations without Main Secondaries


51


Arc Flash reduction by Retrofit


Primary Fuses Only: 594 calories

Primary Circuit-breaker Only: 289 calories

Primary Circuit-breaker + Arc Flash Reduction System:

7.5 calories

52




Retrofill Primary Fuse with Vacuum Circuit-breaker

Sense at 480V Transformer side Trip Primary

Use Protective Relay with Group Settings

Many Variations

Must Meet ANSI C37.59

53




Safety by Design: Improved Unit Substation Design

Line

LA

CPT

Load

CTs

Snubber

Bkr

Typical LV Unit Substation with Vacuum Breaker in MSB (Medium Voltage Switch over Breaker) Assembly

25H X 20W X 18 D, 330 lbs

ANSI C37.20 rated at 25 and

40kA

600, 1200 and 2000A ratings

Integral trip unit with linear trip

actuator

2-step stored energy

mechanism

56


Arc Flash solution for new installation


XXPXXX-90PXXX-P1,P2,P3,P4

4-3/C, #500kcmil

600V, TC, XHHW-2, W/GND

XXPXXX-L1,L2,L3

CABLE TRAY

100 FEET


4-3/C, #500kcmil


XXPXXX-L1,L2,L3

CABLE TRAY

100 FEET


4-3/C, #500kcmil


XXPXXX-L1,L2,L3

CABLE TRAY

100 FEET


4-3/C, #500kcmil


XXPXXX-L1,L2,L3

CABLE TRAY

100 FEET

LV Swgr Elevation Substation One-Line

VCB

ZSI ZSI ZSI ZSI

ZSI

50 51

50 51

(3) 600:5 CT

(3) 3200:5 CT

(3) 3200:5 CT

57

Safety by Design: Improved Unit Substation Design


Arc Flash solution for new installation


Light Detection System Arc Flash reduction for MV Switchgear



Move People Further Away

60


Remain physically outside the flash protection boundary.

Therefore NO ARC FLASH HAZARD protection required.

61

Arc Flash Reduction Remote Racking of MV CB 5/15/27/38 kV Switchgear


VS.

62

Arc Flash Reduction Remote Racking of MV CB 5/15/27/38 kV Switchgear

X


Without With

63

Arc Flash Reduction Remote Switching (Chicken Switch)


Accessory for Remote Operation of Isolation Switch: Increased Operator

Safety.

Temporarily mounts to front of Starter door equipped with mounting

provisions.

Operation by Control Station connected to Motor Operator via 25-

foot Cable.

64

Arc Flash Reduction Remote Operation of Isolation Switch


Arc Flash Reduction Motor Operated Isolation Switch



Redirect Fault Energy

66


Redirects Arc Energy and Particulates

67

Arc Resistant Switchgear


Arc Flaps

2000A or 3000A

breaker with Vent

1200A can be 1

high or 2 high

Control

Section

VT drawer

Manual Close/Open Push

Buttons 68

5/15 kV Arc Resistant Switchgear


Test @ 65kA / 508V

Arc initiated in breaker

compartment

Plenum Design

March 2008 - PASS

Arc out-gassing through

plenum

No arc flash out of the

front of the gear

69

LV Arc Resistant Switchgear Testing



Prevent Fault

70


LV MCC Racking buckets with front door closed


Bucket Position

Connected

Test

Withdrawn

Handle Mechanism

Device Island

Start, Stop, Auto, Man

Unit Latch

Breaker

Internal Shutter Position

Open

Closed

Racking Tool Receiver

Starter

72

LV MCC Withdrawable units with increased safety features


Racking Tool

Receiver: 3/8 Square

Internal Shutter

Position:

Open/Closed

Bucket Position:

Connected/Test/Disconnected

Stab Positive

Position Indicator:

With lockout tag out

hole

Breaker Operator

Test Position Block:

Phase Voltage,

Control, voltage,

Ground 73

LV MCC Withdrawable units with increased safety features


DC Motor Wireless Option

Attaches Easily

Minimal Torque Required

25 Foot Pendant Station

It should interfaces with other

Remote Racking Systems

74

LV MCC Racking buckets with front door closed


Infrared Scanning Windows for LV/MV Assemblies

79

Safety Related Solutions


Monitoring connecting joints on a PDU, utilizing

Plastic Bracket System

Monitoring Individual Connections

80

Continuous Thermal Monitoring


QUESTIONS?

82

V ESW Brasil 2011 Seminrio Internacional de Engenharia

Eltrica na Segurana do Trabalho

So Paulo 8 a 10 de novembro Holiday Inn Parque Anhembi

Thank you!

David Shipp

Eaton Corporation Electrical Sector

Documents

AF Solutions