Section 91. The supreme judicial or superior court shall have jurisdiction in equity, on application of the department or of the mayor of any city or the selectmen of any town where electricity is distributed and sold under the preceding section, to compel the observance and to restrain the violation of any provision thereof and of the general laws relating to electric companies and of all lawful orders, decisions and terms made or imposed by the department or by the aldermen or selectmen under said section.