A hydraulic apparatus for stretching conductors for power lines comprising: a variable displacement hydraulic pump (10) that supplies by means of a hydraulic fluid a hydraulic motor (11) with a closed circuit connection; a displacement regulation system (15) of said hydraulic pump (10); a regulation system (20) of said hydraulic apparatus; characterised in that said regulation system (20) comprises: an inlet (21) that receives said hydraulic fluid that supplies said hydraulic motor (11); a first outlet (22) that supplies said displacement regulation system (15); a second discharge outlet (23); a flow limiter (30) connected to said inlet (21); a regulatable valve (31) connected to said flow limiter (30); a tap (36) connected between the outlet of said regulatable valve (31) and said first outlet (22); a measurement instrument (33) connected to the outlet of said regulatable valve (31), to measure the regulation pressure of said regulation system (20); a safety valve (34) connected to the outlet of said regulatable valve (31), the outlet of which is connected to said second discharge outlet (23).