Resumen
The present invention relates to a method of electrical protection of a synchronous machine, for example a generator, and an electric power generation plant for powering an electric network comprising an electrical protection for synchronising a synchronous machine to an electric network. The method of protection according to the invention establishes a period in which the electrical protection is active and also the instant in which said protection ceases to be active to offer the necessary protection and at the same time not prevent the correct synchronisation.
Reivindicaciones
1. A method of electrical protection of a synchronous machine (1) in the synchronization when said synchronous machine (1) is coupled with an electric network (2), at least the following elements intervening in the synchronization: • mechanical driving means (3), preferably a turbine, connected to the synchronous machine (1) through a movement drive shaft (4) where this synchronous machine (1) has a synchroniser (1.1) and a voltage regulator (1.2), • control means (5) for controlling the mechanical driving means (3) to regulate the amount of power delivered by the mechanical driving means (3), • a switch (6) for electrically connecting the synchronous machine (1) and the electric network (2), • an actuator (7) suitable for opening the switch (6), • a process control unit (9), • measuring means (8) for measuring the intensity delivered from the synchronous machine (1) to the electric network (2) arranged at least in one of the phases with an intensity reading signal output connected to the process control unit (9); and in turn, the process control unit (9) has an output connected to the actuator (7) to command opening the switch (6), • detection means (10) for detecting the closing of the switch (6) the output of which is connected to the process control unit (9), where the synchronisation process for synchronising the synchronous machine (1) to the electric network (2) comprises the following steps carried out sequentially: a) activating the mechanical driving means (3) with the switch (6) open so that the synchronous machine (1) reaches the nominal rotation speed, b) powering the excitation winding of the synchronous machine (1) by connecting its voltage regulator (1.2), c) starting the synchroniser (1.1) once the nominal voltage is reached in the armature of the synchronous machine (1) such that once synchronism is reached, the synchroniser (1.1) commands closing the switch (6), characterised in that • steps a) to d) are additionally carried out by means of the central processing unit (9): a) setting an adjustment intensity threshold value I<SET> less than the value of the assigned intensity of the synchronous machine (1), b) providing overcurrent protection in at least the phase having measuring means (8) for measuring the intensity and where this overcurrent protection is suitable for being activated and deactivated by means of the central processing unit (9), and where it is further suitable for opening the switch (6) when there is an overcurrent value greater than I<SET> aborting the synchronisation process, c) assuring that the protection is active before the instant of closing the switch (6) by means of the central processing unit (9), d) once the closing of the switch (6) is detected by the central processing unit (9), determining a time T<SET> verifying that, in a start-up process with intensity increase up to the nominal value without synchronisation faults, the intensity I<SET> is reached in an instant T>T<SET> , and where during the time interval T<SET> overcurrent protection is maintained active, being deactivated once the instant T<SET> is exceeded; and, • increasing the power in the mechanical driving means to reach the assigned intensity by means of regulating the control means (5) for controlling the mechanical driving means (3). 2. The method according to claim 1, characterised in that the overcurrent protection is an inverse time protection. 3. The method according to claims 1 or 2, characterised in that the overcurrent protection is implemented by means of the central processing unit (9). 4. An electric power generation plant for powering an electric network (2) comprising the following elements: • synchronous machine (1) comprising a synchroniser (1.1) and a voltage regulator (1.2), • mechanical driving means (3) connected to the synchronous machine (1) through a movement drive shaft (4), • control means (5) for controlling the mechanical driving means (3) to regulate the amount of power delivered by the mechanical driving means (3), • a switch (6) for electrically connecting the synchronous machine (1) and the electric network (2), • an actuator (7) suitable for opening the switch (6), • a process control unit (9), • measuring means (8) for measuring the intensity delivered from the synchronous machine (1) to the electric network (2) arranged at least in one of the phases with an intensity reading signal output in communication with the process control unit (9); and in turn, the process control unit (9) has an output in communication with the actuator (7) to allow opening the switch (6), • detection means (10) for detecting the closing of the switch (6) the output of which is connected to the process control unit (9), characterised in that it additionally comprises an overcurrent protection in at least the phase having measuring means (8) for measuring the intensity where: • the protection is configured with a trigger intensity value I<SET> less than the value of the assigned intensity of the synchronous machine (1), • the protection is configured for being activated and deactivated by means of the central processing unit (9), and in that the central processing unit (9) is suitable for carrying out a method according to steps c) and d) of claim 1. 5. The plant according to claim 4, characterised in that the overcurrent protection is an inverse time protection. 6. The plant according to claims 4 or 5, characterised in that the central processing unit (9) is suitable for carrying out the overcurrent protection function. 7. The plant according to any of claims 4 to 6, characterised in that the central processing unit (9) comprises processing means implemented as a set of logic gates where the inputs are: • the output of the detection means (10) for detecting the closing of the switch (6), • the output of the measuring means (8) for measuring the intensity in at least one of the phases, where the output towards the actuation means (7) is the logical product (AND) of two signals: • the comparison of the signal coming from the measuring means (8) for measuring the intensity with a threshold I<SET> ; and, • the signal coming from the detection means (10) for detecting the closing of the switch (6) delayed for a time T<SET> .
