Importance

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Abstract

Protective relay apparatus is constructed of an operating unit that is withdrawable from its insulating housing through an opening at the front thereof. A plurality of sets of shorting contacts and a plurality of plug-type disconnect contacts are mounted to the rear wall of the housing and extend forward therefrom. Mounted on the drawout unit rear panel are a plurality of receptacle-type contacts that receive and cooperate with the disconnect contacts when the drawout unit is inserted fully within the housing. At that time blade means mounted in the drawout unit are interposed between contact sections of the respective sets of shorting contacts to separate contact portions of the latter. Each blade means includes an insulating layer interposed between conducting layers that are engaged with the respective contact sections of the shorting contacts to connect these contact sections in circuit with lumped elements forming part of the drawout unit. The elements of the cooperating disconnect contacts and the shorting contacts with their respective cooperating blade means are constructed and operatively positioned so that contact making and breaking is in a predetermined sequence that protects circuit elements from damage and eliminates false tripping.

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First Claim