This paper presents the development of a protocol converter software (gateway) between two standards used by monitoring and control tasks in power electrical systems. At one side the legacy protocol IEC (International Electro-technical Commission) 60870-5-101 and on the other side the new protocol IEC 61850, which introduces a number of new concepts for the automation of substations, taking advantage of the advances in the field of telecommunications as well as in the hardware of protection devices. The integration of a conventional SCADA (Supervisory Control and Data Acquisition) is proposed with an electrical substation upgraded with the new standard. For the development, free and open libraries were used, implementing a few basic monitoring and control functions. The protocol converter has been tested in a simulation environment and tests were carried out with devices from different manufacturers, verifying the correct mapping between both standards.