How to convert Big5 to UTF8

Hi, All,
I create a database which encoding is UTF8, and create a table test
create table test ( name varchar);
I insert a data '\244\350' encoding is Big5, I wish translate them to
UTF8, so I use
insert into test values ('convert('\244\350' using big5_to_utf_8));
I got an error:
ERROR: invalid byte sequence for encoding "UNICODE": 0xe8;

How could I do for this problem? any ideas.

Alex CS Huang