Medium-voltage switchgear

Remote racking and control options for metal-clad switchgear

Racking or opening and closing a circuit breaker outside of the arc flash boundary helps improve operator safety. Customers have several options for remote racking of circuit breakers. Understanding the difference between remote racking and integral remote racking is important to ensure optimal safety and operational goals are met. Controlling your circuit breakers remotely presents many choices as well. The controls can be hardwired, networked, or done via an operator pendant.

The arc flash boundary around switchgear is the approach limit from an arc source at which incident energy equals 1.2 cal/cm². Remote and integral remote racking capability for medium voltage switchgear is becoming a common requirement to allow operators to be outside of the arc flash boundary for these operations. Understanding the differences between solutions is important for creating maintenance and operating plans.

External remote racking mechanisms

External remote racking devices move the operator outside of the arc flash boundary when connecting or disconnecting the circuit breaker but require the operator to be within the arc flash boundary during setup and potentially opening or closing of the breaker. When opening and closing a circuit breaker from in front of the switchgear, operators are required to wear the appropriate level of PPE.

Steps for installing and using an external remote racking mechanism:

Put on appropriate PPE to enter arc flash boundary
Open the circuit breaker via control switch (switchgear controls can be remote)
Remove cover to extend tool through door into the breaker cubicle to interface with the breaker pan
Physically mount (bolt) external remote racking device to breaker door
Check alignment of remote racking device on breaker door
Connect power to remote racking device
Move outside of the arc flash boundary
Operate remote racking device to move breaker from disconnected or connected position
Reenter the arc flash boundary to remove external remote racking device

Images are for demonstration only. Equipment was not energized.

Integral remote racking mechanisms

While external remote racking devices offer benefits of moving the operator away from the breaker when connecting or disconnecting, it still requires personnel to be directly in front of the switchgear for some time to set the device up. Integral remote racking operations can be performed via a control pendant, remotely via networks and dashboards. To setup the integral remote racking via pendant control would require the operator to enter the arc flash boundary, connect the pendant to its auxiliary port and then exit the arc flash boundary.

Benefits of integral remote racking:

Nothing to interface or insert through the door of a live breaker cell while inside the arc flash boundary
Internally powered by CPT or customer supplied 120vac. No external power for operator to connect
Feedback from the handheld pendant or operator work station on breaker position and status
Provides error feedback to prevent damaging of racking mechanisms
Ability to stop in TEST position. Allows testing capability of breaker controls prior to being fully connected to live bus
Can connect to a network and be controlled through an operator work station

Eaton's integral remote racking provides remote racking and remote control from a single, common operator pendant or across a communication network.

Circuit breaker remote control options:

As previously mentioned, control of a medium voltage circuit breaker can be mounted on the breaker door, a remote operator panel, performed via an integral remote racking pendant or done over a network from an operator work station. Three of the four options presented above allow the operator to be outside the arc flash boundary to open or close the circuit breaker. However, there are differences between the solutions from an installation standpoint.

A hard-wired remote operator panel mounted outside of the arc flash boundary or in an adjacent room to the medium voltage switchgear requires more installation time for terminating wires in the field. The additional wiring during installation can lead to issues during startup if a wire is incorrectly terminated.

In contrast, if a networked solution for breaker operation or a dashboard is used a single cable is used between network switches. While this requires additional programming or setup on the front end it would allow the operator to see circuit breaker status in one or multiple screens. Redundant network switches could be used to create a ring topology if required by the customer.

Eaton’s MR2 system can be used over a network for circuit breaker control in addition to the circuit breaking remote racking.

Eaton’s motorized remote racking (MR2) system has several safety interlock features built in:

When manual racking tool is inserted, power is removed from the MR2 control board preventing pendant or networked operations
Lock out provisions are included on the BPI pan to prevent racking

The video shows a breaker being connected while using the MR2 system. The automatic shutters are mechanically linked to the BPI pan and open when the breaker is in the proper position.

Support for both new and existing equipment

Whether you are installing new equipment or have existing metal-clad switchgear that you are looking to upgrade, there could be unique requirements for your system that should be considered. When applying a remote racking solution to either scenario Eaton’s Electrical Engineering Services and Systems team offers support for customers including arc flash studies and retrofit capabilities.

See how it was done at Ash Grove Cement

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