ACFT X UNAUTH CLB THROUGH OCCUPIED ALT HAD LTSS FROM CPR Y. SYS ERROR PLTDEV.

Narrative

ACFT X TOOK A CLB CLRNC INTENDED FOR ACFT Z. X; WHO WAS AT FL180; CLBED THROUGH THE ALT OF CPR Y; WHO WAS AT FL190. BEFORE I COULD CATCH AND CORRECT THE INCORRECT READBACK; X HAD LOST SEPARATION WITH Y. I CONTINUED THE CLB OF X TO REESTABLISH SEPARATION. I ATTEMPTED TO RECORRECT THE READBACK. LOSS OF SEPARATION WAS APPROX 3.5 MI HORIZLY. THIS HAS BEEN CLASSIFIED AN OPERROR BY MY FACILITY. AS A CONTRIBUTING FACTOR; ALL ACFT ON FREQ WERE BEING CLBED TO FL200. X WAS STOPPED AT FL180 AND TFC HAD BEEN ISSUED TO X THAT Y (MUZ) WAS HIS TFC. LATER X RPTED Y IN SIGHT. TFC HAD BEEN CALLED TO Y THAT AN MD80 WOULD BE OVERTAKING HIM AND HE WOULD SEE THE MD80 COME UNDERNEATH HIS R LOWER SIDE. THE MUZ RPTED THE MD80 IN SIGHT. THE NEXT CLRNC WAS FOR ACR Z DEPARTING FROM RDU; NC; TO CLB TO FL200. X TOOK THE READBACK. X AND Z COULD BE CONSIDERED SIMILAR CALL SIGNS. X HEARD THE MUZ CALL HIM IN SIGHT; ASSUMED THE NEXT CLRNC WOULD BE FOR HIM (SIMILAR CALL SIGNS) AND THAT VISUAL SEPARATION WAS BEING APPLIED; 'CHOMPING AT THE BIT' TO CLB HIGHER -- X ASSUMED THIS WAS HIS CLRNC. UNFORTUNATELY; THE CLRNC I GAVE Z THAT X TOOK WAS AN 'EXPEDITIOUS' CLRNC. X WENT FROM FL180 TO FL186 IN 1 HIT OF THE RADAR. THE NEXT HIT BY THE RADAR WAS GREATER THAN 5 MI AWAY. (A LEGAL HIT). X WAS ABOUT 150 KTS FASTER AND IN FRONT OF Y WHEN HE CLBED THROUGH HIS ALT.