1. Eaton Air Circuit Breakers Arc Flash Reduction Maintenance System
An overview of Eaton’s Arc Flash Reduction Maintenance System for Eaton ACB’s equipped with Digitrip Trip Units

2. 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

3. Digitrip 520MC ARMS Features
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

4. Maintenance Mode Application
Typical 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.

5. Maintenance Mode Schematic
Blue Light Mounted on Panel
Communications:
Indication & Activation

6. Arc Flash Testing IEEE 1584 Test Setup for Power Circuit Breakers
Lab Output Terminals
Cable Connection to Downstream Test Enclosure
Circuit Breaker
3/4” Diameter Copper Electrodes
7 Calorimeter Array
Simulates Body Torso
18 AWG Shorting Wire between 3 Phase Electrodes
Creates Arcing Fault
Arc Flash
Hazard Area
Output = Arc Flash Energy
Open Side of Enclosure
20 ”x 20” x 20”
Downstream Test Enclosure
With Open Front

7. Magnum DS Arc Flash Test Program
Beaver High Power Test Laboratory Example of Magnum DS breaker configured per IEEE 1584 Test Setup for Power Circuit Breakers

8. Personnel Protective Equipment (PPE)
Category
2 PPE
Category
4 PPE
As Described in NFPA 70E 2004

9. Magnum DS Standard & Narrow Frames
Arc Flash Testing Confirms ARMS Accelerated Instantaneous Trip at the Maximum Protection Setting Can Reduce Incident Energy Up to 30%
Magnum DS Standard & Narrow Frames
Non-Current Limiting Construction 480 Vac
100
Published Magnum Trip Unit Curves with
Proper Instantaneous Trip Settings ) 2 10
Category 2 = 8 cal/cm 2
Category 1=4 cal/cm 2
Incident Energy (cal/cm 1
Test Values for
Magnum with Proper
ARMS Maintenance
Trip Unit Instantaneous Settings
Mode Accelerated Trip
(Minimum Setting, Approximately 2X)
0.1 10 40
Available Fault Current (kA) 70
100
(7.3)
(21)
IEEE Calculated Arcing Current (kA)
(35)
(48)
IEEE 1584 Equations using T/C Data
Arc Flash Test Measured Values
ARMs Maint Mode

10. Located under the ‘Trip Curves’ Tab
ARMS Time Current Curves
Time Current Curves for Magnum & Series NRX Digitrip’s with ARMS feature can be found at:
Located under the ‘Trip Curves’ Tab

12. Competitor Solutions & Comparisons
FOR INTERNAL USE ONLY
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.

13. Competitor Solutions & Comparisons
FOR INTERNAL USE ONLY
Schneider – LD/SD Curve
EATON – ARMS Curve
80ms v.
40ms

14. Competitor Solutions & Comparisons
FOR INTERNAL USE ONLY
Siemens Electric –
Dynamic Arc Flash Reduction System (DAS)
What is it?