(1) Parties to proceedings before the commission are known as applicants, petitioners, complainants, defendants, respondents, intervenors and protestants, identified as follows:
(a) "Applicant" means any party who files an application with the commission requesting;
(i) the issuance of a certificate and for authority to perform a service as a public utility, or
(ii) requesting authority to set, increase or lower rates
to be charged for such services.
(b) "Petitioner" means any party who files a petition with the commission requesting relief as pertains to enforcement or alteration of any act, policy, order or directive of the commission.
(c) "Complainant" means any party who complains of anything done or omitted to be done by the commission or any person over whom it has jurisdiction in violation of any law, rule, regulation or order administered or promulgated by the commission, pertaining to matters over which it has jurisdiction.
(d) "Defendant" means any party subject to the laws, rules, regulations and orders administered by the commission against whom any complaint is filed.
(e) "Respondent" means any party subject to the jurisdiction of the commission to whom the commission issues notice instituting a proceeding or investigation or inquiry of the commission; and any party in interest or person ordered before any pending proceeding of the commission.
(f) "Intervenor" means any party permitted by the commission to intervene in any proceeding.
(g) "Protestant" means any party who objects on the grounds of public or private interest to the approval, determination, consent, certification or authorization of any application or petition which the commission may have under consideration.