Medium voltage load break switches control power to circuits with voltage ratings from 1kV to 52kV. These devices can be designed for both indoor and outdoor use and are used to interrupt the flow of power under both normal and emergency situations.

As their name suggests, load break switches differ from non-load break switches because they can safely be opened while power flows through the circuit that they are installed in.

In general, most common load break switches from 2.4kV through 15kV have a continuous rating of 600 amps. However, they are typically fused well below that. These parts are most often operated manually, but some models are also equipped with a motor driven mechanism with a shunt trip which allows them to be opened and closed remotely.

Common Applications for Medium Voltage Load Break Switches

There are a variety of applications that utilize these devices, including:

• Selector Switches - Sometimes called A-B switches, these parts select the power source that will be used to energize the primary of a transformer.
• Power Distribution - A group of switches, can be with or without a main, which direct power to various locations in a factory or other large facility.
• Primary - For a single transformer powering a secondary switchgear.
• Isolation - To de-energize equipment not being used or so that the switchgear can safely be serviced.

Load Break Switch Components

The components of a medium voltage load break switch include the switch body and housing, contacts and mechanism and arc extinguishing medium. The arc extinguishing medium can be air, vacuum of SF6 (sulfur hexafluoride) gas. Vacuum and SF6 gas are used when a medium is needed to provide effective current interruption with minimal contact wear. Air is a cost effective option, especially if the switches will see minimum cycling.

Maintenance Best Practices for Medium Voltage Load Break Switches

As with any mechanical or electromechanical device, regular scheduled maintenance is required. An ideal maintenance process includes:

• Visual inspection
• Lubrication of mechanism and contact joints
• Testing of insulators
• Conductivity testing of the closed switch to ensure minimum internal resistance

The frequency of this maintenance will vary depending on factors including frequency of operation and environmental considerations. Failure to properly maintain these switches can and will result in non-scheduled power outages with damage to surrounding property and can injure or kill personnel in the area.

With proper maintenance, many switchgear installations are still in service well past the time that the OEM stopped supporting them. The problem is that a lack of OEM support or a need for items with long lead times can extend the time of unintended outages, causing loss of production that run into tens or hundreds of thousands of dollars. This makes the support of local used equipment dealers like National Power Equipment invaluable.

Replace Your Load Break Switches with NPE

NPE not only has switches and parts in stock and available for quick shipment but also the experience and knowledge to guide you through pitfalls in things like parts interchangeability that wouldn't otherwise be apparent in the field.

As always, knowledge and information are critical. By gathering the following information, NPE can help you find the right part at the right price:

• Nameplate information
• Photos of the overall switch
• Details of the parts in question

Give us a call at (800) 647-0815 or contact us online for your switchgear and circuit breaker needs.