Arc Resistant Switchgear

Class 6055 / Refer to Handouts 6055HO0101 and 6055HO0901

Active, Arc-Resistant
Arc Terminator™ Arc Extinguishing System

Arc Terminator ™
Arc Extinguishing System

Active system detects and controls the effects of internal arcing faults. It complies with ANSI C37.20.7 requirements for arc-resistant switchgear for Type 1, Type 2B, and Type 2C enclosures, even with the switchgear doors open.

In the event of a confirmed arcing fault inside a Masterclad switchgear or Motorpact equipment lineup containing an Arc Terminator (AT) system, the AT system provides a low impedance parallel path to effectively transfer the fault current from the arc to the 3-phase main bus assembly of the switchgear.

The AT system consists of the following components:

  • A high-speed closing, or shorting, switch is designed to close on the main bus of the switchgear. This creates a three-phase short circuit fault confined to the main bus. Upstream protective device must clear fault within allowed time per applicable standard.

  • The controller box is the central processing device that responds to the signals given by the current sensors and the optical sensors. The current sensor module and the control logic process incoming current and optical signals and send a signal to the output triggering circuit. The output triggering circuit releases stored energy to initiate closing of the mechanical switch and provides optical isolation to prevent false triggering

  • Optical sensors are located in each medium voltage compartment within switchgear structures. A dedicated, properly sized set of current transformers is located at the incoming power source(s).


  • Prevents pressure buildup

  • Reduces release of toxic materials

  • Eliminates need for reinforced switchgear

  • Elimnates special requirements for buildings or plenums

  • Minimizes equipment damage

  • Reduces operating downtime

Passive, Arc-Resistant
Masterclad™ Medium Voltage Switchgear

Two-high, Masterclad 5–15 kV
Metalclad, Arc-Resistant Switchgear

This switchgear and all its components meet the IEEE C37.20.7 arc-resistant test guideline for Type 2B enclosures as well as all other applicable ANSI, UL, and CSA standards for metalclad switchgear.

Switchgear Construction:

  • Arc exhaust options: vented, arc shield, arc planum and duct

  • High-speed operation—3–cycles

  • Removable (draw-out) circuit breaker

  • Fully compartmentalized construction

  • Grounded metal barriers enclose all live parts

  • Automatic shutters driven by breaker racking mechanism

  • Closed door breaker position indication

  • Closed door breaker racking mechanism

  • Insulated copper main bus

  • Standard glass polyester supports

  • Mechanical interlocks

  • Disconnect type CPT and VT trucks

  • Grounded breaker truck in and between test/disconnected and connected positions

  • Low voltage instrument/control compartment isolated from primary voltage areas

  • Compliance to ANSI standards C37.06, C37.09, C37.013, C37.54 and C37.55 (designed and tested to comply with or exceed ANSI and IEEE standards)


  • Up to 63 kA arc containment for 0.5 seconds

  • Voltage ratings from 2.4 kV to 15 kV up to 4,000 A

  • Type 2B construction, one- and two-high structures

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