JPS6173598A - Voltage rising system of synchronous generator - Google Patents

Abstract

PURPOSE:To suppress the exciting rush current of a transformer by interrupting the output side of a transformer, accelerating a synchronous generator to a rated speed, and then gradually rising the output voltage of the generator. CONSTITUTION:When a bus power interruption is detected, a transformer breaker 6 and a field breaker 17 are opened, a generator breaker 8 is closed, and a synchronous generator 10 is driven by a prime mover. When a generator speed arrives at the rated value, the breaker 17 is closed to start operating an automatic voltage regulator. At this time, since a control signal output from the voltage regulator 23 is limited by a limiter 33 to the output signal of a function generator 32, the output voltage of the generator 10 gradually rises. Accordingly, the exciting current of a main transformer 7 gradually increases to avoid the generation of an exciting rush current. When the voltage of the generator arrives at the rated value, the breaker 6 is closed to start supplying power to a load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a voltage startup system for a synchronous generator that can suppress excitation inrush current when exciting a transformer.

[Prior art and its problems]

FIG. 4 is a single-line system diagram showing a conventional example of a power system including a synchronous generator. In the conventional example shown in this FIG.
Through A, 4B, 4C, respective loads 5A, 5B
, AC power is now supplied to 5C,
At this time, it is assumed that the transformer circuit breaker 6 is open ◇ While the power system is operating in this state, if an accident such as a drop in the voltage of the AC power supply 1 or a power outage occurs, the power supply circuit breaker 2 will open. Therefore, bus 3 has a power outage, and loads 5A, 5B,
Power supply to 5C is stopped.

When a power outage on the bus 3 is detected, AC power is sent from the emergency power supply to the bus 3 to minimize the power outage period for the loads 5A, 5B, and 5C. That is, when a power outage of the bus 3 is detected, the prime mover (for example, a diesel engine) 9A starts and drives the synchronous generator 10A.
The output voltage and output frequency of A are connected to bus 3 through rating 7.
Send power to restart loads 5A and 5B5C. If the power from the synchronous generator 10A is insufficient, start the prime mover 9B and turn on the generator circuit breaker 8B when the voltage, frequency, and phase output by the synchronous generator 10B match those of the synchronous generator 10A. When the circuit is closed, the two synchronous generators 10A and IOB operate in parallel to supply power.

In the above operation, a problem arises when the AC power supply 1 starts the synchronous generator 10A and excites the main transformer 7 after a power outage. In other words, it is driven by the prime mover 9A and the synchronous generator 10A
When the synchronous generator 10A reaches its rated speed, the synchronous generator 10A is energized to generate a rated voltage at a rated frequency. Therefore, when the generator circuit breaker 8A is closed, the rated voltage is applied to the main transformer 7, which had been without voltage, so at that moment, the main transformer 7 has a current that is several times to ten times higher than the rated current. Since a large current, so-called excitation inrush current, flows, the synchronous generator 10
For A, the shock is equivalent to a sudden short circuit.

In addition, as shown in FIG. 4, the main transformer 7 is connected to two synchronous generators 10.
In the case of a circuit configuration in which power is received from A and IOB, when only the synchronous generator 10A bears this excitation inrush current, the responsibility of this generator becomes even more severe.

Fig. 5 is a graph showing the status of magnetizing inrush current, in which Fig. 5 [Yes] shows changes in the voltage ■7 applied to the main transformer 7, and Fig. 5 ■ shows the change in the voltage ■7 applied to the main transformer 7. 5 shows the change in current F, and the horizontal axis is the time axis. In this figure, when the generator circuit breaker 8A closes at the instant of time T, the rated voltage is applied to the main transformer 7. This indicates that a large excitation inrush current flows at that time.

If such a magnetizing inrush current repeatedly flows from the synchronous generator 10A or IOB to the main transformer 7, it will adversely affect the life of the generator. Furthermore, since this magnetizing inrush current includes a DC component, the protective relay operates and trips the generator circuit breaker 8A, cutting off the power supply to the load and serving as an emergency power source. This may cause inconveniences such as not being able to do so. In addition, if this synchronous generator is a self-excited generator, sufficient excitation power cannot be obtained due to the voltage drop due to this excitation inrush current, resulting in inconveniences such as the generator voltage not starting up smoothly. 0
Therefore, in order to eliminate these problems, conventionally a dedicated generator was installed for emergency load power supply, but a current limiting resistor was installed between the transformer and the generator, and a switch was installed to short-circuit this current limiting resistor. Measures have been taken to reduce the excitation inrush current by installing magnets, but all of them are extremely expensive.

[Purpose of the invention]

An object of the present invention is to provide a voltage startup method for a synchronous generator that can suppress excitation inrush current in an inexpensive manner when a transformer is excited by a synchronous generator. This method focuses on the fact that the excitation inrush current decreases by lowering the voltage applied to the transformer, and the transformer is disconnected from the load and the synchronous generator is sped up to the rated speed without excitation. At this time, the speed is increased with the synchronous generator and transformer connected, or the synchronous generator is connected to the transformer after reaching the rated speed, and then the synchronous generator is excited. The purpose is to suppress the excitation inrush current by gradually increasing the current and eliminating the output voltage. ◇ [Embodiment of the Invention] Fig. 1 shows an embodiment of the present invention. FIG. 1 (4) is a circuit diagram, and FIG. 1 (4) shows a control block diagram, and FIG. 1 (03) shows a control sequence part.

7 is supplied to the primary side of the generator 10, and after being transformed to a desired voltage by the main transformer 7, it is supplied to the load via the transformer circuit breaker 6. The excitation current flowing through the line 11 is supplied via an excitation transformer 15 as a power source and an excitation thyristor 16 and a field circuit breaker 17, thus forming a so-called self-excited synchronous generator. Further, the output voltage of this synchronous generator 10 is detected by an instrument transformer 21, and a voltage regulator 2 outputs a control signal that makes the deviation between this detected voltage and the voltage set by a voltage setting device 22 zero.
3, and an ignition pulse generator 24 which receives the output signal of the voltage regulator 23 and outputs a signal for controlling the excitation thyristor 16, controls the excitation current flowing through the field winding 11, and controls the generator 10. maintain the output voltage at the desired value. Further, in the present invention, the signal set by the auxiliary setting device 31 is inputted to the voltage regulator 23 mentioned above via the function generator 32 and the limiter 33.

When the f& line stoppage is detected, the transformer circuit breaker 6 and the field circuit breaker 17 are opened, and the generator circuit breaker 8 is closed, and a synchronous generator (not shown) drives the generator 10. However, since the field circuit breaker 17 is open, the generator IO is not energized and the output voltage is zero or only a slight residual voltage. In this state, when the generator speed reaches the rated value, the field circuit breaker 17 is turned on and the automatic voltage regulator starts operating. In other words, the generator residual voltage
A setting signal is generally output from the voltage regulator 23 between 80% and 100% of the rated voltage, and this signal is sent to the ignition pulse generator 24 and input to the voltage regulator 23. Since it is converted into an ignition pulse signal, the AC power from the excitation transformer 15 becomes the required excitation power by the excitation thyristor 16 and flows to the field winding 1.

The output voltage of the synchronous generator 10 is built up by this excitation power, but in order to obtain AC power from the excitation transformer 15, the generator 10 is excited by a pre-excitation device (not shown) to a very low voltage. In some cases, it may be output.

In the present invention, an auxiliary setting device 31 is separately provided, and the setting value of this setting device is set to a value slightly higher than the setting value of the voltage setting device 22. In addition, the output of the function generator 32#i is zero at the beginning of use, but the output increases at a constant rate of change, and after a predetermined time has elapsed, it reaches the setting value of the auxiliary setting device 31 mentioned above. For example, the control signal output from the voltage regulator 23 is the output signal Kf! of the function generator 32 due to the action of the IJ transmitter 33. Since I11 is limited, synchronous generator 10
Since the output voltage of the function generator 32 gradually increases as the signal output from the function generator 32 changes, the voltage applied to the main transformer 7 also gradually increases, and therefore the excitation current of the main transformer 7 also gradually increases. 0, which can avoid the generation of excitation inrush current.
When the generator output voltage reaches the rated value, the transformer circuit breaker 6
Close the circuit and start supplying power to the load. If the supplied power is insufficient, the 20th generator (not shown) may be started and operated in parallel with the synchronous generator 10, but since the main transformer 7 is already in operation, the second generator Of course, the engine can be started using a normal starting method. Note that a cross-current compensator for parallel operation and the like are not shown because they are irrelevant to the present invention.

FIG. 1(B) shows the control sequence. When a bus power outage occurs, the bus power outage relay contact 27 is in the opposite state to that shown in the figure, so the generator can be activated even if the synchronization verification switch 28 is not turned on. By operating the generator circuit breaker closing switch 8SS, the generator circuit breaker closing coil 8CC can be energized and closed. When the generator circuit breaker 8 is closed, the generator circuit breaker auxiliary contact 8XX is closed, so operate the field circuit breaker closing switch 1788 at a desired time to excite the field circuit breaker closing coil 17CC. However, in this control sequence, various interlocks are not shown because they are irrelevant to the present invention.

FIG. 2 is a control block diagram showing a second embodiment of the present invention, and this second embodiment is a case where the time constant of the synchronous generator field winding is large. In this FIG. 2, a transformer circuit breaker 6, a main transformer 7, a generator circuit breaker 8, and a synchronous generator 1
0, the codes, names, uses, and functions of the excitation transformer 15, excitation thyristor 16, field breaker 17, instrument transformer 21, voltage setting device L22, voltage regulator 23, and ignition pulse generator 24 are as follows. Since they are the same as those shown in FIG. (4), their explanation will be omitted.

In the second embodiment shown in the second example, the generator IO was increased to the rated speed with the transformer circuit breaker 6 and the field circuit breaker 17 open and the generator circuit breaker 8 closed. Afterwards, by turning on the field circuit breaker 17 and then closing the initial excitation switch 35, the DC power from the initial excitation power source 36 is applied to the field winding 41.
flows to However, since the time constant of the field winding a41 is large, the excitation current flowing through this winding changes gradually, and therefore the output voltage of the generator 10 also increases gradually.
No excitation inrush current flows through the main transformer 7.

FIG. 3 is a graph showing changes in the voltage and current of the main transformer in the embodiment shown in FIG. 1 or FIG. Figure 3 (6
) shows changes in the current F flowing through the main transformer 7, and both horizontal axes are time axes. In FIG. 3, the rated applied voltage v7 of the synchronous generator 10 gradually increases, and the current flowing through the main transformer also gradually increases, and at time T2
This shows that when the rated voltage is reached, the current F also becomes a constant excitation current, and a large excitation inrush current does not occur as in the conventional example.

〔Effect of the invention〕

According to this invention, when exciting a transformer with a synchronous generator, the output side of the transformer is cut off, and the synchronous generator is connected to the transformer without being energized and the speed is increased to the rated speed. Alternatively, connect it to the transformer after increasing the speed without excitation. If the output voltage of the synchronous generator is then gradually increased by using a function generator, the voltage applied to the transformer will also gradually increase, and the voltage applied to the transformer will increase.
The transformer excitation current gradually increases with this voltage, so no large excitation inrush current occurs. Therefore, a large current will not flow through the synchronous generator and shorten its life, and the protective relay will not malfunction. Therefore, these generators and transformers can be protected reliably, but the above-mentioned excitation inrush current suppression can be achieved by only making slight changes to the control sequence and adding a few circuit elements such as function generators and limiters. Although the cost required for this is small, it can be expected to have a large effect as mentioned above.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the invention, FIG. 2 is a control block diagram showing a second embodiment of the invention, and FIG. 3 is a circuit diagram showing a second embodiment of the invention. It is a graph showing changes in voltage and current of the main transformer. FIG. 4 is a single-line system diagram showing a conventional example of a power system including a synchronous generator), and FIG. 5 is a graph showing the state of magnetizing inrush current. 1...AC power supply, 2...Power circuit breaker,
3...Bus bar, 4A, 4B, 4C...
・Load breaker, 5-5B, 5C...Load, 6-
......Transformer circuit breaker, 7...Main transformer,
8゜8n8B... Generator circuit breaker, 8CC...
..... Breaker closing coil for generator, 8ss...1 Breaker closing switch for generator, 8Xx...... Breaker auxiliary contact for generator, 9A. 9B... Prime mover, 10. IOA, IOB・
...Same generator, 11...Field winding, 1
5... Excitation transformer, 16... Excitation thyristor, 17... Field breaker, 17CC...
... Field breaker closing coil, 17SS... Field breaker closing switch, 21... Instrument transformer, 22... Voltage setting device, 23... ... Voltage regulator, 24... Ignition pulse generator, 27...
... Bus bar power failure relay contact, 28 ... Surface synchronization verification switch, 31 ... Auxiliary setting device, 32 ...
Function generator, 33...Limiter, 35...
...Initial excitation switch, 36...Initial excitation power supply,
41... Field winding (large time constant).

Claims (1)

[Claims] In a power system that supplies alternating current power of a predetermined voltage output from a synchronous generator to a load via a transformer, the synchronous generator is operated by disconnecting the transformer from the load and connecting the synchronous generator to the transformer. When the machine is driven without excitation and the speed is increased to the rated speed, or the synchronous generator is driven without excitation and the rated speed is reached, the synchronous generator and the transformer are connected, and then A voltage start-up method for a synchronous generator, characterized in that the excitation current is gradually increased until the output voltage of the synchronous generator reaches a rated voltage.