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Pad-mounted Transformer

Image of an unobstructed pad-mount transformer in a yard.A transformer is a device that reduces the high level voltage found on Ameren Missouri's distribution system, to the more useable voltage levels found inside homes and businesses. 

A pad-mounted transformer is the underground equivalent of the overhead transformer. In residential areas they look like forest green colored boxes. The dimensions are approximately 32" tall x 34" wide x 34" deep. All cables come into the transformer below ground, and all connections are made inside and kept out of view. 

Note: All pictures are free of obstructions on all sides, and top of our equipment. 

Junction Box

A junction box is a simple piece of pad-mounted equipment, used for splitting high voltage circuits into multiple directions. As with pad-mounted transformers, junction boxes are forest green in color. Two sizes of junction boxes are used on the Ameren Missouri system. The smaller one is approximately 3' x 2' x 3' (H x W x L), and the larger one is approximately 3' x 2' x 6' (H x W x L). Crews inspect junction box equipment once every four years, and open and test this equipment once every eight years.


Pad-mounted switchgears are used to provide switching points, and fuse protection for Ameren Missouri's underground facilities. As with pad-mounted transformers, switchgears are forest green in color. They are approximately four feet tall, and sit on a 6' x 6' pad. They are more common in commercial and industrial areas, but can be found in some residential areas. Crews inspect switchgear once every four years, and open and test this equipment once every eight years. 
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