Section 409.501 - Filing office(1) FILING OFFICES. Except as otherwise provided in sub. (2), if the local law of this state governs perfection of a security interest or agricultural lien, the office in which to file a financing statement to perfect the security interest or agricultural lien is:(a) The office designated for the filing or recording of a record of a mortgage on the related real property, if:1. The collateral is as-extracted collateral or timber to be cut; or2. The financing statement is filed as a fixture filing and the collateral is goods that are or are to become fixtures; or(b) The office of the department of financial institutions or any office duly authorized by the department, in all other cases, including a case in which the collateral is goods that are or are to become fixtures and the financing statement is not filed as a fixture filing.(2) FILING OFFICE FOR TRANSMITTING UTILITIES. The office in which to file a financing statement to perfect a security interest in collateral, including fixtures, of a transmitting utility is the office of the department of financial institutions. The financing statement also constitutes a fixture filing as to the collateral indicated in the financing statement which is or is to become fixtures.