JPH036754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overexcitation protection device that detects the field current of a generator, compares it with an overexcitation setting value, and issues an alarm and a restriction.

A conventional device of this type is shown in FIG. In the figure, 1 is a setting device, 2 is a shunt that detects the field current of the generator, 3 is a signal proportional to the field current, 4 is a comparator, 5 is an alarm signal from the comparator,
Reference numeral 6 indicates a control signal from a comparator, 7 indicates an automatic voltage regulator (AVR), 8 indicates a field coil of a generator, and 9 indicates a generator.

The allowable value of the setting device 1 is set to a value corresponding to the allowable field current at the gas pressure of the internal cooling gas of the generator at the rated time. If the field current increases and the DC signal 3 from the shunt 2 exceeds the above-mentioned allowable value, the comparator 4 issues an overexcitation alarm signal 5 for the generator. Furthermore, by replacing the comparator 4 with an amplifier and applying its output 6 to an automatic voltage regulator, the amount of excitation is reduced and the field coil is prevented from burning out.

FIG. 2 shows the relationship between the gas pressure of the internal cooling gas of the generator and the allowable field current. The horizontal axis shows the allowable field current, and the vertical axis shows the gas pressure of the cooling gas. As shown in FIG. 2, although the allowable field current changes depending on the gas pressure of the cooling gas, in the conventional overexcitation protection device, the allowable value remains constant. As a result, the field coil may burn out due to a decrease in the gas pressure of the cooling gas, and conversely, due to an increase in the gas pressure of the cooling gas,
There was a possibility that the comparator would operate at a value lower than the allowable field current value.

This invention was made to eliminate the drawbacks of the conventional ones as described above, and by changing the allowable value in proportion to the gas pressure of the internal cooling gas of the generator, more ideal overexcitation can be achieved. It is intended to provide a protective device.

This invention will be explained below. Figure 3 is the first
The figure shows a signal generator (not shown) that generates a DC signal 1a proportional to the gas pressure of the internal cooling gas of the generator.
is added. And this DC signal 1
a to change the allowable value of the setting device 1 in proportion to the gas pressure.

In order to facilitate understanding of the present invention, an example will be given and a specific explanation will be given. FIG. 4 shows an example of the main circuit of the present invention. The DC signal 1a is a DC signal proportional to the gas pressure of the internal cooling gas of the generator, and the gas pressure is 0 at the rated value, and the negative value increases as the gas pressure decreases. The DC signal 3 is proportional to the field current, and is 0 when the current is 0.
This is a DC signal whose negative value increases as the current increases. 10 is a setting device, 11 is an output from the setting device with a positive value, 12 is a comparator, 13 is a transistor, and 14 is a relay.

Now, assuming that the output 11 of the setting device 10 is set to A (V), when the gas pressure of the cooling gas is rated, the DC signal 3 proportional to the field current will be A (V).
When the value corresponding to is reached, the output of the comparator 12 is inverted from negative to positive, the transistor 13 becomes conductive, and the relay 14 operates. The contacts of this relay 14 are used for alarm.

Next, the gas pressure of the cooling gas decreases and the DC signal 1a
If it becomes -B (V), then input 3
When becomes a value corresponding to -(A-B)(V), the output of the comparator 12 is inverted and the relay 14 is activated.
Therefore, an alarm can be generated earlier by the field current corresponding to -B (V).

Next, FIG. 5 shows an example in which the comparator 12 in FIG. 2 is replaced with an amplifier 15 and used as a limiting device. As in the case of using the comparator 12 in Fig. 2, if the output 11 of the setting device 10 is set to A(v), when the gas pressure of the cooling gas is rated, the input signal 3 will be A(v). When the deviation exceeds the corresponding value, the control signal 6, which is the output of the amplifier 15, changes from OV to a positive signal proportional to the deviation. By adding this limit signal 6 to the automatic voltage regulator 7, the field current can be limited. In addition, the gas pressure of the cooling gas decreases and the input 1a becomes -B(v).
Similarly, when the input 3 becomes a field current corresponding to -(A-B)v, the limit signal 6 becomes a positive signal, and the field current corresponding to -B(v) increases. Can be limited to a low value. Although FIGS. 1 and 3 have been explained using block diagrams of a thyristor excitation device, the present invention can also be applied to an excitation device using a brushless exciter or a DC exciter.

According to the present invention, the permissible value of the field current is changed in proportion to the change in the gas pressure of the cooling gas of the generator, so that the field coil is not burnt out due to a decrease in the gas pressure of the cooling gas. On the other hand, the automatic voltage regulator does not reduce the excitation amount when the value is lower than the allowable value due to an increase in gas pressure, and the generator is protected from overexcitation so that the generator can always make full use of its power generation function. At the same time, it is possible to easily limit overexcitation.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram showing a conventional overexcitation protection device, Fig. 2 is a diagram showing the relationship between allowable field current and gas pressure of the internal cooling gas of the generator, and Fig. 3 is an overexcitation protection device according to the present invention. Schematic configuration diagram showing the excitation protection device, No. 4
1 and 5 are circuit diagrams showing an example of the main circuit of the present invention. DESCRIPTION OF SYMBOLS 1... Setting device, 1a... DC signal proportional to the gas pressure of the cooling gas, 2... Shunt device for detecting field current, 3... DC signal proportional to field current, 4...
... Comparator, 5 ... Alarm signal, 6 ... Control signal, 7
...Automatic voltage regulator, 8...Electromagnetic coil, 9...
Generator, 10... Setting device, 11... Output signal of setting device, 12... Comparator, 13... Transistor,
14...Relay.

Claims (1)

[Claims] 1. In an overexcitation protection device for a generator, which protects against overexcitation by controlling the field current with an automatic voltage regulator according to the output voltage of the generator, the internal cooling gas pressure of the generator is detected. a detection means for setting the permissible field current, a setting device for setting the permissible value of the permissible field current, and inputting the permissible value set by this setting device, the detection signal of the above-mentioned detection means, and a signal proportional to the actual field current of the generator. , when a signal proportional to the actual field current exceeds the permissible value obtained by changing the permissible value of the setting device in proportion to the detection signal of the detection means, a DC signal proportional to these deviations is output to the automatic voltage regulator. An overexcitation protection device for a generator, characterized in that it is equipped with an amplifier that limits field current.