過去完成進行時用於描述在過去某一特定時間或動作之前已經開始的動作，一直持續到該時間或動作發生。這種時態強調過去的持續性或同時性。以下是一些使用過去完成進行時的例句：
I had been studying for days before I found the answer to the problem.（我在找到問題的答案之前已經研究了好幾天。）
He had been working for three hours before he took a break.（他在休息前已經工作了三個小時。）
They had only been waiting for the bus a few minutes when it came.（他們只等了一會兒車就來了。）
I had been watching TV before you called me.（你叫我之前，我一直在看電視。）
She had been reading a book when she realized she left her glasses on the table.（她正在看書時，突然意識到她把眼鏡落在桌子上了。）
這些例句展示了過去完成進行時如何描述在特定時間點或動作之前已經開始，並持續到該時間點或動作的動作。