Real World article
(written from a Production point of view)

Sector 815 was a sector mentioned in the script of the Star Trek: The Next Generation episode "The Defector", but not seen in the final version of the episode.

In the script, during an interrogation conducted by Commander William T. Riker aboard the USS Enterprise-D, he tested the credibility of the Romulan logistics officer Setal with a ploy where he deliberately misidentified the sector he was assigned to as Sector 815. Setal, recoginizing the ploy, corrected Riker by stating he was assigned to Sector 814.