JPH03178600A - No-load detector for generator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a generator no-load detection device that is applied when disconnecting a generator connected to a system bus.

[Conventional technology]

Figure 2 is a block diagram showing the configuration of a conventional generator no-load detection device. In the figure, 1 is a generator connected to the grid bus, 2 is a breaker, and 3 detects the output current of generator 1. A current transformer 4 is a generator no-load detection device, which is composed of a current zero detector 5 and a relay 6.

Next, the operation will be explained. First, the generator 1 is connected to the grid bus through the breaker 2 and supplies electric power.

In order to disconnect the generator 1 from the system bus, it is necessary to operate the generator 1 after confirming that its output is zero.

A common method for detecting the output of the generator 1 is to detect and confirm the current.

The current flowing between the generator 1 and the system bus, that is, the current flowing through the breaker 2, is detected by the current transformer 3 and input to the generator no-load detection device 4. Next, an operation operation is performed to reduce the output as a process of disconnecting the generator and electric machine 1 from the system bus. Therefore, when the output current of the generator 1 decreases and reaches zero, the current zero detector 5 operates, energizes the relay 6, releases the breaker 2, and disconnects the generator 1 from the system bus.

[Problems to be Solved by the Invention] Since the conventional generator no-load detection device is configured as described above, if a current transformer with a large AC ratio is used to control the rated output of the generator, However, since the accuracy of generator no-load detection deteriorates, a dedicated current transformer must be installed, which is expensive.

This invention was made in order to solve the above-mentioned problems, and in addition to zero detection of the output current of the generator, a condition of the generator field current is added, and it is possible to detect the generator no-load at low cost and with high precision. The purpose is to obtain equipment.

[Means for Solving the Problems] A generator no-load detection device according to the present invention includes a field current sensor that detects a field current, and a no-load field sensor in which the field current generates a rated voltage during standalone operation. It is composed of a no-load field current detector that detects a magnetic current, and an AND circuit that detects the zero output current of the generator and detects the no-load field m current.

[Operation] The generator no-load detection device of the present invention uses a no-load field current detector to detect that the field current of the generator is a no-load field current that generates the rated voltage during independent operation of the generator. At the same time, the generator is disconnected based on the AND condition with the generator output current detected by the zero current detector.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as in FIG. 2 are shown with the same reference numerals.
8 is an AND circuit, 9 is a transformer that detects the output voltage of generator 1, 10 is an automatic voltage regulator, 11 is a field current sensor that detects the no-load field current, and 12 is the generator 1's output voltage. This is a field winding.

Next, the operation will be explained.

First, the current zero detector 5 detects via the current transformer 3 that the output current of the generator l is near zero.

Normally, in the case of standalone operation, the output voltage of the generator 1 is input to the automatic voltage regulator 10 through the transformer 9, and is controlled to a constant value by adjusting the field current of the field winding 12. has been done. However, when connected to the grid bus through the breaker 2, the output voltage of the generator 1 becomes the voltage of the grid bus, and the automatic voltage regulator 10 operates as a reactive power regulator. When the generator 1 is disconnected from the grid bus, the reactive power is also reduced to zero. At this time, the field current of the field winding 12 generates a value based on the V-curve characteristic that expresses the relationship between the field current and output of the generator 1, that is, the rated voltage when the generator 1 is operated independently. This becomes a no-load field current. Therefore, if the no-load field current is detected by the no-load field current detector 7 via the field current sensor 11, it is possible to detect that the output of the power generation tj11 is zero.

The AND circuit 8 indicates that both the conditions for the output of the current zero detector 5 and the output of the no-load field current detector 7 are satisfied as described above.
The generator 1 outputs more power, excites the relay 6, and detects that the output of the generator 1 is zero.

In addition, in the above embodiment, an example was shown in which zero detection of the output current of the generator was used as the breaker switching condition, but it is also possible to use zero detection of active power, zero detection of reactive power, or a detection method that combines these. However, the same effect as in the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, there is provided a no-load field current detector that detects that the field current of a generator is a no-load current, and a current detector that detects that the generator output current is zero. Since the generator no-load detection device is configured with a zero detector and an AND circuit that operates a relay under the AND condition of the rain detector, the accuracy of the load current when the generator is disconnected is closer to zero. The breaker can be opened by detecting a high level of , which prevents damage, and also has the effect of providing an inexpensive device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a generator no-load detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional generator no-load detection device. In the figure, 1 is a generator, 2 is a breaker, 5 is a current zero detector, 6 is a relay, 7 is a no-load field current detector, 8 is an AND circuit, and 11 is a field current sensor. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] It has a current zero detector that detects that the output current of the generator is near zero, and the output of the current zero detector operates a relay to release the breaker between the generator and the system bus to generate electricity. In the generator no-load detection device for disconnecting the generator, a field current sensor detects the field current of the generator, and the field current detected by the field current sensor determines the rated voltage when the generator is operated alone. A no-load field current detector detects the generated no-load field current, and the relay is controlled by satisfying both the output of the current zero detector and the output of the no-load field current detector. A generator no-load detection device characterized by comprising an AND circuit that generates an output.