JP3774838B2 - Accident detection and protection method when starting motor mode of synchronous generator motor, and synchronous generator motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor mode starting method of a synchronous generator motor (hereinafter simply referred to as a generator motor device) and a generator motor device to which the method is applied.
[0002]
[Prior art]
Generally, the generator motor is widely used in a pumped storage power plant. In the pumped storage power plant, according to the operation plan, the water turbine is driven by flowing water from the upper pond to the lower pond during the day when power consumption is large, and the generator motor is operated in the generator mode by this water turbine. To supply. On the other hand, at night, the generator motor is operated in the motor mode by using the surplus power of the power system, and the water wheel is pumped from the lower pond to the upper pond by using the shaft output to drive the water turbine.
[0003]
As examples of other generator-motor apparatuses, flywheel generator-motor apparatuses and synchronous phase adjusters are known. The flywheel generator-motor unit operates the generator motor in the motor mode to store the surplus power of the system as the rotational energy of the flywheel, or operates in the generator mode to release the stored power of the flywheel to the system. To do.
[0004]
When such a generator motor is used in the motor mode, since the generator motor is a synchronous machine, it cannot be suddenly connected to the power system and driven. Therefore, usually, the generator motor is driven by the starter, and the speed is increased to a synchronous rotational speed synchronized with the frequency of the power system, and then is inserted into or put into the power system. As this starting device, there are known a synchronous starting method using another synchronous generator or a generator motor as a starting device, and a static starting method using a static starting device such as a thyristor power converter.
[0005]
In the synchronous start method, for example, one of a plurality of generator motors provided in a pumped storage power plant is driven by a water turbine to start in a power generation mode, and the generator motor to be started is started by the generated power. In this synchronous start method, the generator motor that operates in the power generation mode is referred to as a parent device, and the generator motor that is to be started is referred to as a slave device. Then, after gradually increasing the power generation voltage and frequency of the master unit to accelerate the slave unit to the synchronous rotation speed, the slave unit is inserted into the power system to complete the start-up.
[0006]
On the other hand, in the static start method, the power of the power system is converted into variable voltage and variable frequency power using a thyristor power converter or the like, and the output voltage and frequency are gradually increased to accelerate the generator motor to the synchronous rotational speed. After that, it is inserted into the power system to complete the start-up.
[0007]
As another example, when starting a gas turbine generator, the generator is operated as an electric motor to start the gas turbine. In this case, the gas turbine generator is generally started by a thyristor starting method.
[0008]
[Problems to be solved by the invention]
In the conventional technology as described above, there is a problem that no consideration is given to protection against a ground fault or a short circuit accident of the main circuit of the generator motor at the time of starting.
[0009]
First, as the main circuit protection on the armature side of the generator motor, an overcurrent relay that detects the current of the main circuit with an alternating current CT (current transformer) and performs a protection operation when the detected current exceeds the set value is used. is set up. Since this overcurrent relay mainly protects during normal commercial frequency operation in parallel with the system, the AC CT characteristics are also set in accordance with the commercial frequency. Therefore, it is impossible to detect an overcurrent at a low frequency such as during starting.
[0010]
By the way, the magnitude of the accident current in the main circuit is basically proportional to the value obtained by dividing the generator electromotive force by the circuit impedance, but both the generator electromotive force and the circuit impedance increase in proportion to the frequency. The frequency component is cancelled. As a result, the magnitude of the accident current during start-up is approximately the same as the magnitude of the accident current such as a short-circuit accident at the commercial frequency.
[0011]
However, when starting at a low frequency immediately after the start of acceleration of the generator motor, the overcurrent cannot be detected by the AC CT. Therefore, the conventional overcurrent relay cannot protect the short circuit accident of the main circuit of the generator motor, and the armature winding and the start bus cable may be burned out.
[0012]
On the other hand, it is conceivable to detect a low-frequency accident current during start-up of the generator motor using, for example, DC CT. However, DC CT is not practical because it is expensive. For example, even if a low-frequency accident current is detected by DC CT, a protection method similar to the conventional one that trips a circuit breaker inserted in the main circuit based on the detection and removes the accident cannot be applied. That is, since the accident current at the beginning of the start is a low-frequency current, the breaker capability at the commercial frequency of the breaker is not sufficient, and the breaker may be damaged.
[0013]
An object of the present invention is to solve the above-described problems of the prior art, and more specifically, to detect an accident in the main circuit during start-up of the motor mode of the generator motor.
[0014]
Another object of the present invention is to prevent burning of the main circuit due to an accident of the main circuit during the motor mode start of the generator motor in addition to the above-described problem.
[0015]
[Means for Solving the Problems]
The present invention basically uses the starting device that generates a variable voltage of a variable frequency, and at the time of starting the motor mode in which the synchronous generator motor to be started is accelerated from a stopped state to a predetermined rotational speed, the synchronous generator motor detecting a current flowing through the field winding, when it exceeds a determined value the detected value is determined in advance, more detects that the ground fault or short-circuit fault occurs in the main circuit of the synchronous generator motor, The above-described problems are solved.
[0016]
In other words, if a ground fault or short circuit accident occurs in the armature of the synchronous generator motor or the main circuit bus connected to the armature at the start of the motor mode, the synchronous generator or the synchronous power A large low-frequency accident current flows at the accident point from the synchronous generator motor of the motor and the slave unit, and from the synchronous generator motor to be started in the case of the static start system. By the way, the synchronous machine includes an armature winding and a field winding, and these windings can be considered as an electromagnetically coupled rotary transformer. Therefore, when a large low-frequency accident current flows in the armature winding, a current corresponding to the accident current also flows in the field winding, so when the field current of the synchronous generator motor exceeds the predetermined fluctuation range It is possible to detect that a ground fault or a short circuit accident has occurred in the main circuit bus.
[0017]
Here, the field current of the synchronous generator motor can be directly detected by the direct current CT, but since the direct current CT is not very practical, instead of this, the current flowing through the field winding is changed to the field current. corresponding also encompasses a physical quantity, for example, the power to be output to the field current for supplying excitation device, the field winding to convert the AC to control the firing angle of the semiconductor switching elements in a predetermined field current for transducers, an input AC power Nagaremata the exciter can be detected based on any one of the firing angle of the exciter.
[0018]
The present invention can be applied to both a synchronous start method and a static start method. In particular, when applied to a synchronous start system, that is, a synchronous generator or a synchronous generator motor is a master unit, a synchronous generator motor to be started is a slave unit, both armature windings are connected via a circuit breaker, If you start the handset by machine, when detecting a current flowing in at least one of the field windings of the master unit and the slave unit, beyond the determination value to which the detected value is determined in advance, the master unit and the slave unit It is possible to detect that a ground fault or short circuit accident has occurred in the main circuit.
[0019]
In addition, when an accident is detected by the above-described accident detection method, by exciting the field circuit of the synchronous generator motor via a resistor, the excitation is released and energy corresponding to the accident current is consumed by the resistor. Accident current can be quickly attenuated.
[0020]
A synchronous generator-motor apparatus to which the above-described accident detection method and protection method are applied includes a synchronous generator-motor having an armature winding and a field winding, and an excitation for supplying a field current to the field winding. A device, a field breaker inserted between the field winding and the excitation device, a resistor connected in parallel to the field winding via a switch, and the field winding Field current detecting means for detecting a flowing current, and for determining a ground fault or a short circuit accident in the main circuit in the process of increasing the detected value of the current and the synchronous generator motor from a stopped state to a predetermined rotational speed. Protective means for comparing with a predetermined determination value , and opening the field breaker and outputting a command signal to turn on the switch when the detected value exceeds the determination value Composed.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a generator motor apparatus in which the accident detection method and the protection method of the present invention are applied to a synchronous start type pumped-storage power generation system. As illustrated, the pumped-storage power generation system includes a plurality of generator motors 1a and 1b, and only two units are shown in the figure. The generator motors 1a and 1b include armature windings 2a and 2b and field windings 3a and 3b. The armature windings 2a and 2b are connected to the power system 6 via synchronous circuit breakers 4a and 4b and main transformers 5a and 5b. Further, the rotors of the generator motors 1a and 1b around which the field windings are wound are connected to water turbines 7a and 7b which are prime movers. The armature windings 2 a and 2 b of the generator motors 1 a and 1 b are connected to each other via a synchronous start circuit breaker 8. Currents flowing through the armature windings 2a and 2b (input / output currents of the generator motor) are detected by the AC CTs 9a and 9b, respectively, and input to the overcurrent relays 10a and 10b.
[0022]
On the other hand, the field windings 3a and 3b are connected to excitation devices 12a and 12b via field breakers 11a and 11b, respectively, and short-circuit resistors 14a and 14b are connected via switches 13a and 13b, respectively. Connected in parallel. The excitation devices 12a and 12b are each configured using an AC / DC power converter. That is, AC power is taken in from the on-site power systems 15a and 15b via the excitation transformers 16a and 16b and the circuit breakers 17a and 17b, and the AC is converted into a predetermined field current by the firing angle control of the semiconductor switch element and output. Is configured to do. The firing angle of the semiconductor switch element is generally controlled by the field current control circuits 18a and 18b so as to keep the field current at a constant value.
[0023]
Here, the structure which concerns on the characteristic part of this invention is demonstrated. Input AC currents of the excitation devices 12a and 12b are detected by the AC CTs 21a and 21b, and are input to the field current detection circuits 22a and 22b. The field current detection circuits 22a and 22b are obtained by converting the field current output from the excitation devices 12a and 12b based on the relationship between the input AC current and the output field current of the excitation devices 12a and 12b. is there. Since the relationship between the input AC current and the output field current is theoretically determined as is well known, detailed description thereof is omitted. The field current detection value thus obtained is input to the field overcurrent detection circuits 23a and 23b. The accident detection circuits 23a and 23b compare the detection value of the input field current with a predetermined determination value related to the accident determination or a determination range with a constant dead zone, and exceed the determination value or the determination range. In the case of an accident. When the field overcurrent detection circuits 23a and 23b determine that there is an accident, an opening command is output to the field breakers 11a and 11b, and a closing command is output to the switches 13a and 13b.
[0024]
Next, the operation of the pumped storage power generation system configured as shown in FIG. 1 will be described. When operating the generator motors 1a and 1b in the power generation mode, the synchronous circuit breakers 4a and 4b and the synchronous start circuit breaker 8 are opened, the guide vanes of the turbines 7a and 7b are gradually opened, and the rotational speed is set to the commercial frequency. Gradually increase to the corresponding sync speed. Then, when the field current is supplied by the excitation devices 12a and 12b, and the generated voltage and frequency of the generator motors 1a and 1b match the voltage and frequency of the power system 6 and the phases match, the synchronous circuit breakers 4a and 4b To complete parallel processing.
[0025]
Next, the operation when the generator motor 1a is operated in the motor mode will be described. As described above, since the generator motor 1a is a synchronous machine, the synchronous circuit breaker 4a cannot be suddenly turned on and driven by the electric power of the power system 6. In this embodiment, the synchronous start method is adopted. ing. That is, the other generator motor 1b is used as a master unit, thereby driving the generator motor 1a of the slave unit. After the speed is increased to the synchronous rotation speed, the synchronous circuit breaker 4a is inserted and paralleled to the power system 6. Specifically, first, the synchronous start circuit breaker 8 is turned on, the master unit and the slave unit are connected by the start bus, and the guide vanes of the master unit's turbine are gradually opened to start the speed increase. Accordingly, the slave unit is accelerated while being synchronized with the master unit. After the slave unit reaches the synchronous operation, the synchronous circuit breaker 4 a is closed and parallel to the power system 6. At the same time, after the synchronous start circuit breaker 8 is opened, the generator motor 1b which is the master unit is disconnected and stopped. The generator motor 1a, which is a slave unit subject to synchronous start, is started by applying an internal pressure to the water turbine 7a and pushing the water surface down to a level below the impeller in order to minimize or no load at the time of start.
[0026]
Here, the accident detection and protection operation at the time of an accident according to the feature of the present invention will be described. Now, a case where an accident occurs at point A of the synchronous start bus will be described as an example. When the generator motors 1a and 1b are operated in a normal state in the motor mode, if an accident occurs at point A, the synchronous start circuit breaker 8 is opened, and therefore the generator motor 1a and the power system 6 have an accident. The fault current is supplied to the point. Since this accident current is a commercial frequency current, it is detected by the AC CT 9a, the overcurrent relay 10a is operated, the synchronous circuit breaker 4 is opened, the field breaker 11a is opened, and the excitation is stopped, Further, the switch 13a is closed and the field winding 3a is short-circuited via the short-circuit resistor 14a to quickly attenuate the accident current and protect the main circuits such as the armature winding and the synchronous start bus from burning. . When an accident occurs at point B of the synchronous start bus, the overcurrent relay 10a operates and is similarly protected.
[0027]
Here, the accident detection and protection method when starting the motor mode of the generator motor, which is a feature of the present invention, will be described. At the time of synchronous start, when the synchronous circuit breaker 8 is turned on with the synchronous circuit breakers 4a and 4b opened, and the synchronous motor 1b is used as a parent machine and the synchronous generator 1a is used as a child machine, the point A is When an accident occurs, as described above, an accident current having the same magnitude as that in the normal state is supplied from the master unit and the slave unit. Incidentally, since the rotation frequency is low at the initial stage of the start and the accident current is also low, the AC CTs 9a and 9b cannot detect the accident current, and the protection by the overcurrent relay 10a does not operate. However, when a low-frequency fault current flows through the armature windings 2a and 2b, the field windings 3a and 3b are caused to flow into the field windings 3a and 3b according to the principle of the rotary transformer as shown in FIG. A low frequency current If corresponding to the accident current flows as an overcurrent superimposed on the current Ie. That is, the field windings (d-axis windings) 3a and 3b are rotated in the rotating coordinate system of the rotor with respect to the three-phase armature windings (U, V and W-phase windings) 2a and 2b. . Therefore, with respect to the armature current and field current, a model of a rotary transformer through mutual inductance can be considered. Here, the frequency component of the low frequency current If is predominantly the same frequency component as the generator frequency at the time of the accident, and the same frequency component and twice the frequency component. The double frequency component occurs when the accident at point A is an unbalanced accident. In view of the relationship between the armature current and the field current, the present invention detects an accident based on a change in the field current.
[0028]
Here, the field current including the low frequency current corresponding to the accident current may be directly detected by the DC CT, but it is not practical in consideration of the accuracy and cost of the DC CT. Therefore, in the embodiment of FIG. 1, the field current detection circuits 22a and 22b take in the AC input current on the primary side of the excitation devices 12a and 12b detected by the AC CTs 21a and 21b, and convert it into the field current ie. To the accident detection circuits 23a and 23b. The accident detection circuits 23a and 23b compare the input field current ie with a determination value iref corresponding to the field current under constant current control, and determine that an accident has occurred when ie exceeds iref. Here, a fixed dead zone may be provided for the determination value iref and set as a range. When the field overcurrent detection circuits 23a and 23b determine that there is an accident, an opening command is output to the field breakers 11a and 11b, and a closing command is output to the switches 13a and 13b. Thereby, the field currents of the generator motors 1a and 1b flow into the field short circuit having the short-circuit resistors 14a and 14b and are quickly attenuated. The attenuation constant at this time is reduced to Rf / (Rf + Rdr) compared to the normal circuit time constant, where Rf is the resistance of the field winding and Rdr is the resistance of the field circuit short-circuit resistor. . As a result, the fault current on the armature side of the generator motor at the time of a system fault is attenuated, and the starting bus and the armature winding are protected from burning. It is possible to protect the main circuit of the generator motor by coordinating the accident determination value iref with the overcurrent capability of the starting bus and the armature winding.
[0029]
As described above, according to the embodiment shown in FIG. 1, it is possible to quickly and accurately detect an accident during low frequency operation during start-up of a generator motor without providing additional equipment such as DC CT. Moreover, it is possible to prevent the main circuits such as the armature winding and the starting bus of the generator motor from being burned out.
[0030]
The field current detection circuits 22a and 22b convert the field current into a field current by multiplying the average value or effective value of the input AC current by a predetermined conversion coefficient to convert it into a field current. The field current may be obtained by synthesizing the DC side current of the excitation device from the 120 ° energization type AC input current.
[0031]
FIG. 3 shows a configuration diagram of an embodiment in which the present invention is applied to a generator motor system provided with a thyristor starter. In the figure, the same components as those in FIG. The difference from the embodiment of FIG. 1 is that a system using a thyristor starter comprising a thyristor power converter is used instead of the synchronous start system in which the generator motor 1a to be started is started by another generator motor. That is, as shown in the figure, the thyristor power converter branches power from the connection bus of the main transformer 5a and the synchronous circuit breaker 4a, and converts the electric power of the power system 6 through the input circuit breaker 31 and the starting transformer 32 of the starting circuit. 33. The output of the thyristor power converter 33 is connected to the main circuit bus of the armature of the generator motor 1a via the output circuit breaker 34. The thyristor power converter 33 includes a converter and an inverter. The thyristor power converter 33 temporarily converts the alternating current supplied from the starting transformer 32 into direct current, converts the direct current into alternating current having a desired frequency and a desired voltage, and generates the generator motor 1a. The armature winding 2a is supplied. The field excitation circuit of the generator motor 1a and the accident detection / protection circuit at the start of the motor mode are the same as those in FIG.
[0032]
The operation of the embodiment of FIG. 3 configured as described above will be described. When starting the generator motor 1a in the motor mode, the input circuit breaker 31 and the output circuit breaker 34 of the starting circuit are turned on with the synchronous circuit breaker 4a opened, and the thyristor power converter 33 is activated. Then, by controlling the thyristor power converter 33, the voltage and frequency supplied to the generator motor 1a are gradually increased, and the generator motor 1a is gradually increased from the stopped state to the synchronous rotational speed. When the speed of the generator motor 1a reaches almost the synchronous speed, the voltage, phase and frequency of the armature of the generator motor 1a and the power system 6 are matched, the input circuit breaker 31 and the output circuit breaker 34 are opened, and the synchronous circuit breaker 4a is input and the start-up is completed.
[0033]
In this embodiment, when an accident such as a short circuit occurs at point A of the starting bus during startup, the accident is detected based on a change in the field current as in the case of FIG. An opening command is output to 11a, and a closing command is output to the switch 13a. As a result, the field current of the generator motor 1a flows through the field short circuit having the short-circuit resistor 14a and is quickly attenuated, thereby protecting the starting bus, the armature winding and the like from burning.
[0034]
FIG. 4 shows a configuration diagram of still another embodiment of the present invention. In the present embodiment, the present invention is applied to the same synchronous start method as in FIG. The difference from FIG. 1 is that, instead of detecting the field current, the control angle α of the excitation device, which is a physical quantity corresponding to the field current, is detected, and an accident during the motor mode start based on the detected α. Detect and protect.
[0035]
That is, generally, during start-up, the field current control circuits 18a and 18b control the gate pulse control angle α of the semiconductor switching elements of the field excitation devices 12a and 12b, so that the actual field current and the set value are The deviation is set to zero. Therefore, the control angle α is a substantially constant value. In this state, when an accident occurs on the starting bus side, the field current fluctuates due to the influence, and as a result, the control angle α also varies. Therefore, in the present embodiment, the control angle α output from the field current control circuits 18a and 18b is taken into the accident detection circuits 35a and 35b and compared with the control angle αref corresponding to the normal field current. Is determined to be an accident when the value exceeds a predetermined setting range. The protection operation based on this determination result is the same as in FIG.
[0036]
【The invention's effect】
As described above, according to the present invention, it is possible to detect an accident in the main circuit during the start of the motor mode of the generator motor, and to perform a protective operation based on this, thereby enabling the armature winding of the generator motor to It is possible to prevent the main circuit such as the start bus and the like from being burned out.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an embodiment in which the present invention is applied to a pumped-storage power generation system that starts a generator motor by a synchronous start method.
FIG. 2 is a diagram showing a waveform of a field current corresponding to a low-frequency accident current.
FIG. 3 is a configuration diagram of an embodiment in which the present invention is applied to a generator motor system that starts a generator motor by a thyristor start method.
FIG. 4 is a configuration diagram of an embodiment of a pumped storage power generation system showing a modification of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a, 1b Generator motor 2a, 2b Armature winding 3a, 3b Field winding 4a, 4b Synchronous circuit breaker 7a, 7b Water wheel 8 Start circuit breaker 11a, 11b Field circuit breaker 12a, 12b Excitation device 13a, 13b Opening and closing 14a, 14b Short-circuit resistors 18a, 18b Excitation control circuits 21a, 21b AC CT
22a, 22b Field current detection circuit 23a, 23b Accident detection circuit 33 Thyristor power converter 35 Accident detection circuit

Claims (6)

  A current flowing in the field winding of the synchronous generator motor is detected in the process of increasing the speed of the synchronous generator motor to be started from a stopped state to a predetermined number of revolutions using a starting device that generates a variable voltage of a variable frequency. An accident detection method at the time of starting the motor mode of the synchronous generator motor, which detects that a ground fault or a short-circuit accident has occurred in the main circuit of the synchronous generator motor when the detected value exceeds a predetermined determination value.   Synchronous generator or synchronous generator motor is the master unit, the synchronous generator motor to be started is the slave unit, both armature windings are connected via a circuit breaker, and the master unit is accelerated to generate variable voltage of variable frequency. In the process of generating and speeding up the slave unit from a stopped state to a predetermined rotational speed by the power generation output of the master unit, the current flowing in at least one field winding of the master unit and the slave unit is detected, and the detected value is An accident detection method at the time of starting a motor mode of a synchronous generator motor that detects that a ground fault or a short-circuit accident has occurred in a main circuit of a master unit and a slave unit when a predetermined determination value is exceeded.   A current flowing in the field winding of the synchronous generator motor is detected in the process of increasing the speed of the synchronous generator motor to be started from a stopped state to a predetermined number of revolutions using a starting device that generates a variable voltage of a variable frequency. When the detected value exceeds a predetermined determination value, it is detected that a ground fault or short circuit accident has occurred in the main circuit of the synchronous generator motor, and based on the detection of the accident, the synchronous generator motor A protection method when starting a motor mode of a synchronous generator motor in which a field circuit is short-circuited through a resistor.   Synchronous generator or synchronous generator motor is the master unit, the synchronous generator motor to be started is the slave unit, both armature windings are connected via a circuit breaker, and the master unit is accelerated to generate variable voltage of variable frequency. In the process of generating and speeding up the slave unit from a stopped state to a predetermined rotational speed by the power generation output of the master unit, the current flowing in at least one field winding of the master unit and the slave unit is detected, and the detected value is When a predetermined judgment value is exceeded, it is detected that a ground fault or short-circuit accident has occurred in the main circuit of the master unit and the slave unit, and the field winding of the master unit and the slave unit is detected based on the detection of the accident. A protection method when starting a motor mode of a synchronous generator motor in which a wire is short-circuited through a resistor. A synchronous generator motor having an armature winding and a field winding, an excitation device for supplying a field current to the field winding, and inserted between the field winding and the excitation device A field breaker; a resistor connected in parallel to the field winding via a switch; a field current detection means for detecting a current flowing in the field winding; a detected value of the current; Compared with a predetermined judgment value for judgment of ground fault or short circuit accident of the main circuit in the process of increasing the speed of the synchronous generator motor from the stopped state to a predetermined number of revolutions , and the detected value exceeds the judgment value And a protection means for outputting a command signal for opening the field breaker and turning on the switch. The excitation device is a power converter that controls an ignition angle of a semiconductor switch element, converts alternating current into a predetermined field current, and outputs the field current.
6. The field current detecting means obtains a current flowing through the field winding based on any one of an input AC current of the exciter and an ignition angle of the exciter. The synchronous generator-motor apparatus described.

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