Wis. Stat. § 111.55

If a conciliator named under s. 111.54 is unable to effect a settlement of a labor dispute between a public utility employer and its employees within a 15-day period after the conciliator’s appointment, the conciliator shall report that fact to the commission. The commission, if it believes that a continuation of the dispute will cause or is likely to cause the interruption of an essential service, shall submit to the parties the names of either 3 or 5 persons from the panel provided for in s. 111.53. Each party shall alternately strike one name from such list of persons. The person or persons left on the list shall be appointed by the commission as the arbitrator or arbitrators to hear and determine such dispute.