JPS6346680B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a generator.

In recent years, the main circuit systems of underwater areas such as thermal power plants and nuclear power plants have been constructed between the generator 1 and the main transformer 4 for step-up, as shown in Figure 1, with the intention of omitting the starting transformer (not shown). A power plant is being constructed that employs a circuit system in which a generator circuit breaker 3 with a large current capacity and an in-station transformer 5 are directly installed in the circuit of a phase-separated bus 2.

In the case of this main circuit configuration, the generator breaker 3 is responsible for interrupting fault current in the event of an accident on either the low voltage side of the main transformer 4, that is, the generator main circuit or the high voltage side of the main transformer 4. Don't sleep.

On the other hand, when an accident such as a short circuit or ground fault occurs in a power system, the fault current in each phase of the system generally has a waveform that is a superimposition of AC and DC currents, and further Depending on the state and the aspect of the accident, the current waveform immediately after the accident may continue to be unipolar for several cycles without reaching the current zero point, as shown in FIG. In the figure, the curve indicated by the broken line d indicates the DC component,
t ₀ indicates the time when the accident occurred. This phenomenon in which the current waveform becomes unipolar (sometimes negative) is called a current shift phenomenon.

Therefore, in the circuit system shown in Fig. 1, the generator circuit breaker 3
In this case, it may be necessary to interrupt a fault current accompanied by a current deviation phenomenon as shown in FIG. 2 described above.

By the way, when a fault accompanied by such a current deviation phenomenon occurs, a protective relay device installed in the system detects the fault, issues a trip command to the circuit breaker 3, and interrupts the fault current. However, the current interruption by the circuit breaker 3 is normally completed when the current reaches zero point after the contact is opened. However, each type of circuit breaker has a predetermined effective extinguishing time determined by its type, so in order to interrupt the current,
the current zero point is at least once during the effective arc extinguishing time;
times must exist. Therefore, in the case where a current deviation phenomenon as shown in FIG. 2 described above occurs, it becomes impossible to shut off in this state. Therefore, it is necessary to postpone the tripping command to circuit breaker 3 until just before the current reaches the zero point, but in some cases it may take a considerable amount of time to reach near the zero point, which may affect system stability. Unilateral extension of the shutdown also poses problems in terms of surface area and equipment capacity.

The current deviation phenomenon has recently come into focus due to the increased capacity of generators and special operating conditions, and there are not many known countermeasures for this phenomenon in the prior art.

The present invention solves the above-mentioned problems caused by the current deviation phenomenon, and in order to ensure that the generator circuit breaker can cut off the fault current, the present invention is designed to identify the operating state of the generator and the area in which the current deviation phenomenon occurs. In comparison, it is an object of the present invention to provide a generator control device for forcibly shifting the operating state of the generator to a region where the current deviation phenomenon does not occur as much as possible.

The present invention will be described below with reference to an embodiment shown in FIG. The terminal voltage of the generator 1 is detected by a potential transformer (hereinafter referred to as PT) 11 connected to the phase-separated bus 2 of the output circuit of the generator 1, and this voltage is applied to the field winding 16 of the generator 1. Automatic voltage regulator (hereinafter referred to as AVR) that controls the excitation device 15 that supplies excitation current to maintain it at a preset generator terminal voltage.
In addition to the normal excitation control circuit having PT 12, a current transformer 13 is further provided in the generator 1 or the phase separation bus 2 to detect the current of the generator 1, and to detect the voltage of the PT 11 as well as a current deviation limiter (hereinafter referred to as ZML). )
Add to 14. The output signal of this ZML14 is
Adder circuit inside AVR12 or voltage setting device 9
It is configured to be applied to an 0R drive circuit.

Next, a control method for the generator configured as shown in FIG. 3 for suppressing the current deviation phenomenon of the present invention will be explained.

The current deviation phenomenon shown in FIG. 2 is also related to the attenuation rate of the AC component and the attenuation rate of the DC component, but it can be said that the degree of deviation is almost determined from the magnitude relationship between the two immediately after a failure occurs. Therefore, for example, if we consider the case where a one-wire grounding fault occurs on the high voltage side of the main transformer 4 and a current deviation phenomenon occurs, the active power P and reactive power Q before the fault occur as shown in Figure 4. A pattern of the region where the current shift phenomenon occurs is obtained with the coordinates as . Here, the above P and Q are the values at the fault point, and are different from the active power P ₀ and reactive power Q ₀ seen from the terminals of the generator, so they can be corrected accordingly. Figure 4 shows the main transformer 4 where the generator circuit breaker 3 is installed.
This is an example showing on the P and Q coordinates a region where the DC component is larger than the AC component immediately after a one-wire grounding accident on the high voltage side of the main transformer 4, as seen from the low voltage side of the main transformer 4. In the figure, a circle 17 indicates a range in which the DC component of the faulty phase is larger than the AC component, and a circle 18 indicates a range in which the DC component of the phase lagging behind the faulty phase is larger than the AC component. Each yen 17,1
In the range where the DC component is larger than the AC component inside 8,
The closer you get to the center of the circle, the larger the difference between the DC and AC components becomes, indicating that a severe current deviation phenomenon occurs.

Therefore, in order to limit the current deviation phenomenon at the time of the above-mentioned accident, it is necessary to forcibly set the operating points P and Q before the failure to be outside the circles 17 and 18 shown in FIG. It is only necessary to control the transition to .

Therefore, the operating status of generator 1 is set to PT11 and CT1.
By inputting 3, it is identified with ZML14, and this and
Compare the current deviation phenomenon occurrence pattern stored in advance as shown in FIG. , by outputting to the drive circuit of the voltage setting device, the terminal voltage of the generator 1 is changed so that the operating point is forced to be outside each circle 17, 18 in advance, and the reactive power is controlled.

Note that the current deviation phenomenon occurrence pattern is based on the main transformer 4.
Patterns corresponding to various failures on the high-voltage side and low-voltage side of the system are calculated in advance from the system configuration and stored.
In addition, the active power and reactive power P ₀ and Q ₀ seen from the terminals of the generator 1 and the active power and reactive power P and Q at the fault point are corrected by ZML14.

Therefore, according to the present invention, by installing the ZML 14, the operating point is forcibly controlled in advance to be outside the current deviation phenomenon occurrence area indicated by the P-Q coordinates before the failure occurs. Even if a system fault occurs, the operating state of the generator 1 that would cause a current deviation phenomenon can be avoided, so the occurrence of the current deviation phenomenon can be prevented, and the generator circuit breaker 3 can prevent the accident from occurring. The current can be cut off easily.

In the above embodiment, the operating point was controlled by reactive power control by the AVR 12, but although not shown, the drive device of the generator 1 (for example, a steam turbine)
It is also possible to control the active power using a speed governor. Although not shown, the main transformer 4
If PT and CT are installed on the high voltage side of the main transformer 4, it is also possible to more accurately identify the active power and reactive power P and Q on the high voltage side of the main transformer 4. Furthermore, regarding the comparison between the occurrence pattern of the current deviation phenomenon shown in Fig. 4 and the operating point, since no large current deviation phenomenon occurs near the circumference of each circle 17 and 18, It is also possible to prevent excessive output of ZML 14 by providing an appropriate setting width.

As described above, the generator control device according to the present invention prevents the generator circuit breaker from being unable to shut off due to current deviation phenomena and from harsh operating conditions.
Since it requires only a simple configuration of providing an auxiliary signal to the AVR, it has the advantage of being extremely inexpensive, compact, and highly effective.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the main circuit configuration adopted in hydro, thermal, and nuclear power plants, etc. Figure 2 is a waveform diagram showing an example of a fault current accompanied by a current deviation phenomenon, and Figure 3 is a diagram showing an example of a fault current accompanied by a current deviation phenomenon. FIG. 4 is a block diagram showing an embodiment of the generator control device according to the present invention, and is a diagram showing a range in which the DC component is larger than the AC component. 1... Generator, 2... Phase separation bus, 3... Generator circuit breaker, 4... Main transformer, 5... Station transformer,
11... Potential transformer (PT), 12... Automatic voltage regulator (AVR), 13... Current transformer (CT), 14
... Current deviation limiter (ZML), 15 ... Excitation device, 16 ... Field winding.

Claims (1)

[Claims] 1. In a power plant consisting of a generator driven by a water wheel or a steam turbine, and a main transformer connected to the generator via a generator circuit breaker to boost the output voltage of the generator, the output voltage of the generator and output current as input to identify the current operating state,
This operating state is compared with the current deviation phenomenon occurrence region pattern indicated by the active power (P) and reactive power (Q) of the generator, and if the above operating state is within the current deviation phenomenon occurrence region, A current deviation limiting device outputs a signal proportional to the degree of penetration of the Q axis, and the output signal of this current deviation limiting device is input to force the operating point to be outside the current deviation phenomenon region. A generator control device consisting of an AVR that controls the terminal voltage of the generator.