© 2011 Eaton Corporation. All rights reserved.

Eaton Air Circuit BreakersArc Flash Reduction Maintenance System

An overview of Eaton’s Arc Flash Reduction Maintenance System for Eaton ACB’s equipped with Digitrip Trip Units

2 2© 2011 Eaton Corporation. All rights reserved.

ARMS Technology TM Overview

Arc Flash

Reduction

Maintenance

System

ARMS is a separate integral analog circuit that when enabled in the Maintenance Mode, ARMS TechnologiesTM provides an accelerated instantaneous trip to reduce arc flash (system can trip as fast as 18ms!)

The operator can pre-select from 5 levels of protection to facilitate the maximum arc flash reduction while avoiding nuisance tripping during planned start-up and maintenance operations without disturbing the normal operational trip unit settings

Local and remote enabling and indication capabilities are provided as well as consideration for Lock-out/Tag-out procedures

ARMS is available on Magnum Digitrip 520MC & 1150, as well as Series NRX Digitrip 520M and 1150

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ARMS features in white area of trip unit to separate it from normal trip unit settings

Blue LED indicated in “Maintenance Mode”

2 Position Selector Switch: • ON = Local ON• O/I = OFF or External Control

5 Position Arc Flash Reduction Setting:

• From R5 (Max) …. To R1 (Min) Reduction• Curves available on-line for each setting

Remote Indication:• Power Relay Module Maintenance Mode Contact • Communications

Remote Enable:• Switchgear Mounted Logic Level Selector Switch• Switchgear Mounted Logic Level Relay• Remote Mounted Control Switch• Via Communications: PowerNet, Modbus, Profibus

Lock-out/Tag-out

Digitrip 520MC ARMS Features

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Maintenance Mode ApplicationTypical application: Magnum breaker equipped with ARMS feeding multiple Molded Case Circuit Breakers.

If an MCCB needs to be serviced you can work on the breaker live or you can shut the power down via the Magnum, thus shutting down power to all circuits.

With ARMS, you can activate the Maintenance Mode and service the MCCB live, without shutting down all circuits, and in the event there is a fault in the system the Magnum will trip faster reducing the amount of Arc Flash to provide maximum protection to the service personnel.

This activation can be performed locally or remotely. Externally wired BLUE Lighting via a contact in the trip unit can offer visual indication that Maintenance Mode is enabled and should be reset once work is complete.

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Maintenance Mode SchematicBlue Light

Mounted on Panel

Communications:Indication & Activation

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Circuit Breaker

Output =Arc Flash Energy

Lab OutputTerminals

Cable Connection to Downstream Test Enclosure

18 AWG Shorting Wire between 3

Phase ElectrodesCreates Arcing

Fault

7 Calorimeter

ArraySimulates

Body Torso

Open Side of Enclosure20 ”x 20” x 20”

Downstream Test Enclosure

With Open Front

3/4” Diameter Copper Electrodes

Arc Flash Hazard Area

Arc Flash TestingIEEE 1584 Test Setup for Power Circuit Breakers

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Beaver High Power Test Laboratory

Example of Magnum DS breaker configured per IEEE 1584 Test Setup for Power Circuit Breakers

Magnum DS Arc Flash Test Program

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As Described in NFPA 70E 2004

Category 2 PPE

Hazard Risk Category

Clothing Description(Typical Number of Clothing Layers in Parenthesis)

Required Minimum Arc Rating PPE

Cal/cm2

0Non-melting, Flamable Materials

(i.e Untreated Cotton, Wool, Rayon, Silk, or Blends of These Materials)

With a Fabric Weight of at Least 4.5 oz/yd2 (1)N/A

1 FR Shirt and FR Pants or FR Coverall (1) 4

2Cotton Underware - Conventional Short Sleeve and Brief/Shorts

Plus FR Shirt and FR Pants (1 or 2)8

3Cotton Underware Plus FR Shirt and FR Pants Plus FR Coverall

or Cotton Underware Plus Two FR Coveralls (2 or 3)25

4Cotton Underware plus FR Shirt and FR Pants

With Full Multi-Layer Flash Suit (3 or more)40

Category 4 PPE

Personnel Protective Equipment (PPE)

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Magnum DS Standard & Narrow Frames Non-Current Limiting Construction Tests @ 480 Vac

0.1

1

10

100

10 40 70 100Available Fault Current (kA)

Inc

ide

nt

En

erg

y (

ca

l/c

m2)

IEEE 1584 Equations using T/C Data Arc Flash Test Measured Values ARMs Maint Mode

Published Magnum Trip Unit Curves with Proper Instantaneous Trip Settings

Category 1=4 cal/cm2

Category 2 = 8 cal/cm2

ARMS Maintenance Mode Accelerated Trip

(Minimum Setting, Approximately 2X)

Test Values for Magnum with Proper

Trip Unit Instantaneous Settings

(7.3) (48)IEEE Calculated Arcing Current (kA)(21) (35)

Arc Flash Testing Confirms ARMS Accelerated Instantaneous Trip at the Maximum Protection Setting Can Reduce Incident Energy Up to 30%

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Time Current Curves for Magnum & Series NRX Digitrip’s with ARMS

feature can be found at:www.eaton.com/magnumwww.eaton.com/seriesnrx

Located under the ‘Trip Curves’ Tab

ARMS Time Current Curves

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Competitor Solutions & Comparisons

Schneider Electric –

Alternate Maintenance Setting (AMS) Switch• What is it? Simply put, this is a switch in the Zone Selective Signal to the breaker. 

In the Schneider solution the "AMS" switch is wired in series with the Zone Selective Input wiring to the breaker (Recall that Magnum & NRX offer ZSI as a standard option on all models of Digitrips).  When the switch is "armed" it opens the Zone Selective Signal to the breaker from the downstream breaker.  This puts the trip unit into a ‘quick trip’ mode if the fault is above the Short Time pick-up setting. 

The Digitrips analog circuit is much faster than Schneider's modified ZSI (40ms vs 80ms maximum clearing time).  Timing is everything, the faster the trip the less arc energy and the less chance for harm to personnel.  Eaton’s ARMS circuit will pick-up at 2.5X (peak sensing), this modified ZSI system from Schneider will only pick up at the Short Time Setting level. 

For example, if a Schneider TU short delay pick-up is set at 8X at 300ms and the fault was at a 7X level it would not even trip until Long Delay took it out.  In addition Eaton has a contact output from the trip unit that is positive feedback that you are in the ARMS mode (contact that can be wired out to a blue stack light or other notification system) the Schneider solution does not offer this additional indication.

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Competitor Solutions & ComparisonsSchneider – LD/SD Curve EATON – ARMS Curve

80ms

v.

40ms

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Competitor Solutions & Comparisons

Siemens Electric –

Dynamic Arc Flash Reduction System (DAS)

• What is it?