From the Encylopaedia Judia 14:365
A more problematical use of the term Ru'ah ha-Kodesh is when in some way hypostatized, or used as a syonym for G-d.
This tendency toward hypostatization is already apparent in such expressions as "Ru'ah ha-Kodesh resting" on a person or place, or someone "receiving Ru'ah ha-Kodesh". But it is pronounced in descriptions of the Ru'ah ha-Kodesh speaking (Pes. 117a), or acting as defense counsel on Israel's behalf (Lev. R. 6:1), or leaving Israel and returning to G-d (Eccles. R. 12:7). This hypostationization is essentially the product of free play of imagery, and does not have the connotations of Ru'ah ha-Kodesh as an entity separate from G-d. Neither are there any over tones of the Ru'ah ha-Kodesh somehow forming as part of the Godhead, as found in the Christian concept of the Holy Ghost which was a translation of Ru'ah ha-Kodesh.
The problems centering around this use of the term Ru'ah ha-Kodesh are the product of it's different shading into one another. Sometimes it is used merely as a synonym for G-d, and at others it refers to the power of prophecy through divine inspiration. In order to maintain a perspective on the matter, the monotheistic background and the image character od rabbinic thinking must always be kept in mind.