querying a column w/ timestamp with timezone datatype

I an 9.1 PG database: I have a column which is a timestamp w/ time zone.
So the value I have as one record in table is: 15:55:24.342848+00

If i want to find records less or greater than that timestamp, how do I
construct the query?

select * from schema.table where tscol >= '15:55:24.342848+00';
select * from schema.table where tscol >= '15:55:24.342848+00'::timestamp;
select * from schema.table where tscol >= cast('15:55:24.342848+00' as
timestamp with time zone);

do not work. Do I have to convert the value to a string and substr to
15:55:24 and then convert back to a timestamp? It's been a long while since
I had to query a pg table w/ a timestamp with time zone value. Any help
here would be appreciated.