To fully understand the Passive Voice, see the example from the question linked in your post:
“…he was taken to the police station”
The words in bold are in the past passive voice.
Who took the man to the police station? Presumably one or more police officers, but it is not an important detail hence the writer chose the passive voice. The equivalent in the active voice would be
…they (the police officers) took him to the police station.
To construct the passive voice, we need the auxiliary verb "be" and the past participle of the main verb, in this case the PP of the verb take is taken.
- He is taken to the station (Simple Present)
- He is being taken to the station (Present Continuous)
- He has been taken to the station (Present Perfect)
- He was taken to the station (Simple Past)
- He had been taken to the station (Past Perfect)
- He had been being taken to the station (Past Perfect Continuous)
This last construction is rarely used, and generally found only in grammar books.
See: Active and Passive Verb Forms posted by EnglishPage.com
P.S The OP's grammatically correct sentence would be
Here is a sentence [which [I think] is an example] of the passive participle clause.