test pen dimly lit on extension cable

[shiodong]

After a recent electric leak incident in which my whole aquarium set up is "energised"( tingling sensation even by touching the glass), I decided to check all my electrical outlets and extensions. I found out that my extension cables(Taiyo brand, 1yo, bought from supermarts, got safety mark, 1 connected to my PC, another to supply my aquarium power) are able to dimly light up my test pen just by touching the test tip on the cable insulation with nothing plugged into their sockets. Similar results from the cables of some other equipment. Strangely, my older extension cable doesn't light up the test pen. Is this a normal behaviour of test pen on energised cable? Safe for continued use?

 

[jtjt00]

Leakage, replace the extension cord for safety.

 

[shiodong]

Thanks for the advice. Sigh. so many pieces of junk that money can buy in recent years that don't last--branded or otherwise.