some power plants may produce both power and process steam as output products and may be referred to as cogeneration power plants . this type of power plant may include at least one extraction type steam turbine in order to conveniently output process steam . sometimes the available power plant steam supply is insufficient to satisfy both load demand and process steam requirements whereupon it may be desirable to prefer load demand over process steam requirements . the present invention is a control system for electronically implementing that preference .