The November 17 blast was caught on CCTV, with flashes of flames seen through the building’s door for almost 20 seconds.
Police allege a man in high visibility workwear forced his way into the Fawkner Street substation and used a spanner to steal copper worth $1000.
The man can be seen exiting on to Fawkner Street and walking away shortly after the 5pm explosion.
He was last seen getting into an orange Holden Captiva on Moore Street before he drove away.
The man is perceived to be Caucasian in appearance and aged 30 to 50-years-old.
Along with the high-vis top, he wore navy blue pants and a blue hat.
Police have released CCTV as they call for the public’s help to identify him.
Anyone with information is urged to contact police.