JPH0398499A - Speed detection method for water-wheel generator - Google Patents

Abstract

PURPOSE:To detect the speed based on an output voltage surely even in the case of low-speed operation of a water-wheel generator by supplying the exciting circuit of the generator with a low-level exciting current at the time of starting and stopping a water wheel and by obtaining the speed detection signal of the water-wheel generator based on the output voltage signal of the generator. CONSTITUTION:At the time of starting a water wheel, a detection control circuit 14 closes a switch 12 by a speed-governing command and an exciting current is supplied from a battery 8 to an AC exciter 2. A water-wheel generator 1 is also excited by the exciting current so that a generating output voltage is obtained even in the state of low-speed operation of the generator at the time of starting of the water wheel. The resistance of a resistor 13 is set in such manner that the exciting current at that time has a low-level. At the time of stopping of the water wheel, the ON-control of the switch 12 is again performed by the detection control circuit 14 and a speed-detecting operation similar to that at the time of starting the water wheel is carried out when the output voltage of the generator 1 is lower than a given value.

Description

[Detailed description of the invention] A. Industrial application field The present invention relates to a method for detecting the speed of a water turbine generator.

R. Summary of the Invention The present invention provides a speed detection method for obtaining a speed detection signal of a water turbine generator from an output voltage signal of the generator, by supplying a low-level excitation current to the excitation circuit of the generator when starting and stopping the water turbine. , which ensures reliable speed detection when starting and stopping the water turbine.

C. Conventional technology To detect the speed of water turbine generators, etc., a tacho generator is installed on the shaft connecting the prime mover and the generator. There are known methods in which a speed detector such as a permanent magnet generator or a pulse pickup is provided, and a method in which the output voltage of the generator is detected by a transformer. Detection signals from these speed detection methods are used to control the speed of the water wheel or turbine that serves as the prime mover of the generator, thereby keeping the output frequency of the generator constant.

D. Problems to be Solved by the Invention Among the conventional speed detection methods, the former requires a large-scale detection device because the speed detector is axially coupled to a generator or the like. In this respect, the latter method can utilize a transformer for excitation control of the generator, etc., and can reduce the cost of the device.

However, the latter method detects a weak voltage due to the residual magnetism of the generator during low-speed operation when the prime mover starts and stops, which has the problem of erroneous detection or unstable detection due to noise. In particular, for water turbine generators, the water turbine is started gradually to prevent the water hammer phenomenon that occurs when the water turbine's penstock or waterway closes rapidly. There is a problem in that it makes it difficult to detect the speed at the time of starting and stopping.

An object of the present invention is to provide a speed detection method that can reliably detect the speed from the output voltage even when a water turbine generator is operating at low speed.

E. Means and Effects for Solving the Problems In order to achieve the above object, the present invention supplies a low-level excitation current to the excitation circuit of the generator when starting and stopping the water turbine of the water turbine generator, and reduces the output voltage of the generator. The speed detection signal of the water turbine generator is obtained from the signal, and when the water turbine is started or stopped, the generator output voltage is made to exceed a certain level suitable for detection by supplying exciting current.

F. Example FIG. 1 is a circuit diagram showing an embodiment of the present invention.

An excitation current is supplied to the field winding of the water turbine generator (1) through a rectifier 3 from an AC exciter 2 which is axially coupled to the generator (1). Excitation of the AC exciter 2 is carried out from the output of the generator 1 to the transformer 4.
The current of the AC power obtained is adjusted by the Cyrisk converter 5,
This current adjustment is performed by automatic voltage control using the generator output voltage signal obtained by the transformer 6 as a feedback signal of the automatic voltage regulator 7. Further, an initial excitation current is supplied to the AC exciter 2 from a battery 8 through a field breaker 9, a current limiting resistor 10, and a rectifier ll.

In a water turbine generator equipped with an excitation device using such an AC exciter, an excitation circuit from the battery 8 to the rectifier 1l through the control switch 12 and current limiting resistor 13 is used as a speed detection means for controlling the speed of the water turbine. a detection control circuit l4 which turns on a control switch l2 in response to a speed control start command to a water turbine speed governor (not shown) of the generator l and turns off the control switch l2 when the transformed output of the transformer 6 reaches a certain value; , a frequency-to-voltage converter l5 that converts the frequency of the transformed output of the transformer 6 into a voltage signal to obtain a detected speed signal.

In the above configuration, when the water turbine is started, the detection control circuit 14 closes the switch 12 based on the speed governor command, and the battery 8
An exciting current is supplied from the switch 12 to the AC exciter 2 through the path of the resistor I3 and the diode I1. The water turbine generator 1 is also excited by this exciting current, and the generator 1 can obtain a generated output voltage even in a low-speed operating state when the water turbine is started. The resistance value of the resistor l3 is set so that the excitation current at this time is a low level excitation current, and the output voltage of the generator l is set so that a speed detection signal of a certain value or more is obtained from the frequency-voltage detector l5. be done. This excited state continues until the switch l2 is turned off by the detection control circuit l4 when the output voltage of the generator 1 exceeds a certain value, and the generator 1
When the output main pressure exceeds a certain value, a continuous speed detection signal is obtained from the converter 15 through initial excitation and steady operation after voltage establishment.

Further, when the water turbine is stopped, when the output voltage of the generator 1 falls below a certain value, the detection control circuit 14 turns on the switch 12 again, obtaining the same speed detection operation as when starting.

Therefore, a certain amount of excitation current is supplied to the water turbine generator 1 even during low-speed operation when the water turbine starts and stops, so that the output voltage exceeds a certain value, and the converter 15 has a high resistance to the voltage detected by conventional residual magnetism. It is possible to obtain a detection voltage with excellent noise and stability, and it is possible to prevent water hammer, etc. when starting and stopping a water turbine. Further, in terms of the configuration, it is sufficient to simply add a switch I2, a resistor I3, and a detection control circuit l4.

In addition, in the embodiment, the excitation method of the water turbine generator is not limited to the AC exciter method, but it goes without saying that it can be applied to a cyrisk excitation method, etc. Further, the speed detection signal is not limited to analog detection using a frequency-voltage converter, but can be detected as a digital signal.

G. Effects of the Invention As described above, according to the present invention, a low-level excitation current is supplied to the generator when starting and stopping the water turbine, and a speed detection signal is obtained from the generator output voltage. Compared to detection from the generator output, this method eliminates malfunctions and unstable detection due to noise, resulting in more reliable detection, and provides speed detection that reliably prevents the sagging phenomenon of water turbines.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. G... Water turbine generator, 2... AC exciter, 7... Automatic voltage regulator, 8... Battery, 9... Field switch,
l2... Control switch, I3... Current limiting resistor, 14.
...Detection control circuit, I5...Frequency-to-voltage converter. Figure 1 Circuit diagram of the embodiment!・Hydrogen generator 2 ・AC exciter 7...Automatic voltage regulator 8...Battery 9...Field switch! 2・Control switch l3・Current limiting low resistance l4...Detection control circuit 15...+r*Kenichi voltage converter

Claims (1)

[Claims] (1) A low-level excitation current is supplied to the excitation circuit of the generator when the water turbine of the water turbine generator is started or stopped, and a speed detection signal of the water turbine generator is obtained from the output voltage signal of the generator. How to detect the speed of a water turbine generator.