JPH01243835A - Shortcircuit detection device in excitation circuit of rotating electric machine - Google Patents

Abstract

PURPOSE:To prevent an earth detection device from being subjected to insulation breakdown and to improve reliability, by connecting a line shortcircuit detection resistance of a line shortcircuit detection device to the earth side of a limiting resistance of the earth detection device. CONSTITUTION:A line shortcircuit detection device 40 connects series circuits of a voltage dividing resistance R1 and a line shortcircuit detection resistance r1, which is a variable resistance, respectively to a three-phase circuit of an AC excitation circuit 37. These series circuits are formed into a three-phase bridge in a Y-connection. An earth side of a limiting resistance R2 is connected to the neutral point of this three-phase bridge to complete the constitution. Both terminals of the line shortcircuit detection resistance r1 and the earth detection circuit resistance r2 are introduced to a detection section 6 respectively. Since the line shortcircuit detection resistance r1 is connected to the earth side of the limiting resistance R2, no potential of an isolation amplifier of the line shortcircuit detection device 40 will be so high against the earth as before that the occurrence of shortcircuit there can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an excitation circuit short-circuit detection device for a rotating electric machine that detects a short-circuit in an excitation circuit that excites a rotor winding with alternating current.

[Conventional technology]

As a rotary N machine equipped with an excitation circuit that excites the rotor winding with alternating current, a variable speed generator is known that excites a secondary circuit with alternating current so that the frequency of the system is constant. The alternating current voltage that AC excites the secondary circuit of this variable speed generator is very high compared to a conventional synchronous generator, and may exceed 10 kV for example, in a large-capacity 480 OMVA class generator. Therefore, compared to conventional synchronous generators and induction machines, ground faults and line-to-line short circuits are more likely to occur in the secondary circuit, and the damage caused when short circuits occur is greater. Therefore, it is extremely important to promptly detect short circuits and the like in order to protect the equipment, and an excitation circuit short circuit detection device has been proposed as a protection device.

As a conventional excitation circuit short circuit detection device, for example,
The current detection type disclosed in Publication No. 7-142164 is known, but it is not effective in a power generation system where the secondary current is controlled by ACR, such as a variable speed electric machine, because the current does not change. A voltage detection type excitation circuit short circuit detection device as shown in the figure is used.

An alternating current excitation current is supplied to the rotor winding 3 of the variable speed generator 1 shown in FIG. 4 via the cycloconverter 4 and the alternating current excitation circuit 37. A line-to-line short circuit in the AC excitation circuit 37 causes the phase voltage between the N-U phase, N-■ phase and N-W phase, and the line-to-line voltage between the U-V phase, N-W phase and W-U phase to be divided. Piezoresistor R1 and line short detection resistor r1
The line-to-line short-circuit detection device detects the resulting voltage using the detection logic 7. On the other hand, a ground fault detection device for detecting a ground fault in the AC excitation circuit 37 is provided with a DC power supply 12 that applies a DC voltage to the neutral point of the AC excitation circuit 37 via a limiting resistor Rz for ground fault detection. The current flowing at the time of occurrence is detected by a ground fault detection resistor r2, and the detection logic 35 makes a determination. This earth fault detection device and line short circuit detection device constituted an excitation circuit short circuit detection device.

[Problem to be solved by the invention]

However, in the conventional excitation circuit short circuit detection device, the isolation amplifiers 13 and 20 of the line short circuit detection device are directly affected by the voltage of the AC excitation circuit 37. When [ is 10 kV or more, isolation amplifier 13.20
As the line-to-line short circuit detection device became larger, there was a risk that the line-to-line short circuit detection device itself would cause a short circuit.

It is also conceivable to detect line-to-line short circuits using only the phase voltages based on the neutral point, excluding the P section in FIG. However, for example, U
When a phase causes a ground fault, the related circuit becomes as shown in Figure 5, the potential of the N phase rises to the phase-to-phase voltage, and the isolation amplifier 13゜20 is required to have a very high #@ edge. There was a risk of causing a ground fault.

The present invention solves the above problems, and its purpose is to solve the above problems by itself! An object of the present invention is to provide an excitation rotation short-circuit detection device for a rotating electrical machine that prevents fim destruction and improves reliability.

[Means to solve the problem]

In order to achieve the above object, the present invention is characterized in that a line short circuit detection resistor of a line short circuit detection device is connected to the ground side of a limiting resistor of a ground fault detection device connected to an AC excitation circuit. .

[Effect]

Since the excitation circuit short circuit detection device of the present invention has the above-described configuration, even if a ground fault occurs in the AC excitation circuit, the potential on the earth side of the limiting resistor can be suppressed to a low level. It becomes easy to insulate the isolation amplifier that has a connection relationship with the line-to-line short circuit detection resistor connected to the line-to-line short circuit detection resistor, and it is possible to easily prevent #fAa destruction such as a ground fault in the same part and improve reliability.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic circuit diagram showing an excitation circuit short circuit detection device for a variable speed generator.

The variable repeating electric machine 1 is driven by the prime mover 2 and supplies electric power to the grid 36. From the system 36, a cycloconverter transformer 5. An AC excitation current is supplied to the three-phase rotor winding 3 via the cycloconverter 4 and the AC excitation circuit 37 . Since this AC excitation circuit 37 is a high-voltage circuit, there is a risk of line-to-line short circuits or ground faults. Therefore, an excitation circuit short-circuit detection device for detecting these abnormalities is connected to the AC excitation circuit 3. .

This excitation circuit short-circuit detection device includes a line-to-line short-circuit detection device [40] that detects a line-to-line short circuit, and a ground fault detection device 1i that detects a ground fault.
It consists of 41. The ground fault detection device 41 is.

It has a DC power supply 12 connected to the neutral point N of the AC excitation circuit 37 via a limiting resistor R2, and a ground fault detection resistor rz connected between the DC power supply 12 and the ground. In addition, the line short circuit detection device r1140 connects a series circuit of a voltage dividing resistor R1 and a line short circuit detection resistor r1, which is a variable resistance, to the three-phase circuit of the AC excitation circuit 37, respectively, and connects these series circuits with a Y connection. This is a sum bridge, and the ground side of the limiting resistor R2 is connected to the neutral point of this three-phase bridge. Both terminals of the line short circuit detection resistor r1 and the ground fault detection resistor r2 are respectively introduced into a detection section 6, and this detection section 6 is connected to the line short circuit detection section of FIG. 2 which constitutes the line short circuit detection device 4o. , and the ground fault detection section shown in FIG. 3, which constitutes the ground fault detection device 1241.

Each voltage dividing resistor R1 shown in FIG. 1 is manufactured in the same lot to minimize individual differences in temperature coefficient and resistance value. Similarly, line-to-line short circuit detection resistors ri with small individual differences are used, but during calibration, the DC power supply 12 and AC voltage are applied to the AC excitation circuit 37, and line-to-line short circuits are applied to balance the three-phase bridge. Adjust the detection resistor r1 in advance. In addition, the voltage dividing resistor R1 is 50 to 50 of the line short circuit detection resistor rl depending on the excitation voltage.
The resistance value is selected to be about 1000 times higher, but the limiting resistance R2
is selected to be sufficiently smaller than the voltage dividing resistor R1, for example, at a resistance value of about 10%. Since a balanced three-phase voltage is applied to the AC excitation circuit 37 in a normal state, the current flowing through the limiting resistor Rz is zero, and the terminals u, Vy Wg
A balanced voltage that is rx/(Rt+rt) times the excitation voltage is applied to n.

As shown in FIG. 2, these voltages are separately input to the line-to-line short detecting section of the detecting section 6 as each phase voltage and each line voltage by isolation amplifiers 13 and 20. Of these, the phase voltage is determined by the low-pass filter 14
．． The signal is inputted to comparators 18 and 19 via an absolute value circuit 15° smoothing circuit 16 and a 6x amplifier 17.

The line voltage is also controlled by the low pass filter 21. Absolute value circuit 2
The signal is input to comparators 24 and 25 via a 2° smoothing circuit 23. Here, the comparators 18 and 24 input ONL to the OR logic 26 when the input voltage is greater than the voltage v2. Further, the comparator 19.degree. 25 turns on when the input voltage is lower than the voltage v1, and inputs the voltage to the OR logic 27. These two OR logics 26 and 27 are both AND
It is connected to the logic 28, and the occurrence of a short circuit between lines can be detected by the output of the AND logic 28. In steady state, OR logic 26 is ONL, OR logic 27 is 0FFL, and therefore AND logic 28 is OFF.
It becomes.

Now, if a short circuit occurs between phases N and 'U of the AC excitation circuit 37 shown in FIG. nu comparator 19 is ONL, OR logic 27 is ON
Then, the AND logic 28 turns ON, and this output detects that a short circuit has occurred.

In addition, if a line short circuit occurs between the U and V phases, the limiting resistor R2
is smaller than the voltage dividing resistor R1, the mold pressure between u and v becomes extremely small, and the comparator 25 becomes O as in the previous case.
N, the OR logic 27 turns ON, the AND logic 28 outputs an ON signal, and a line short circuit is detected. The comparator voltage v1 at this time is the maximum value of the excitation voltage V2m
against ax.

Select so that Here, G is the ratio (equivalent gain) between the comparator input voltage and the excitation voltage.

The reason why the voltage v1 is selected in this manner is that even if there is a short circuit between the N and U phases, strictly speaking, the voltage between U and N is not zero, but is approximately Rz/Rx times higher.

On the other hand, if a ground fault occurs in the AC excitation circuit 37, for example, U
When a ground fault occurs in a phase, the circuit related to this ground fault is
It will look like the figure. As you can see from this circuit, DC power supply 1
If the voltage of 2 is eo and the N-U interphase voltage is V2, then a voltage of Va-b= ('Vz+eo) rz/Rz is generated between a and b. This voltage is applied to the isolation amplifier 29 and the low-pass filter 30 of the ground fault detection section shown in FIG. It passes through the absolute value circuit 31 and is compared with the threshold voltage v3. When a ground fault occurs, the ground fault is detected by an AND logic 33 using a combination of a comparator 32 and a timer 34.

According to the above embodiment, since the line short circuit detection resistor r1 is connected to the ground fault of the limiting resistor R2, the line short circuit detection device 1
The potential of the isolation amplifier 13.20 of 140 does not become higher than the ground as in the conventional case, and it is possible to prevent the occurrence of a ground fault in this part. This can be seen from the fact that while the line short detection resistor r1 was connected to point A in FIG. 5, the line short detection resistor rl is connected to point B in this embodiment. Furthermore, since the line short circuit detection device 40 and the ground fault detection device 11241 can be treated at the same potential, they can be combined into one excitation circuit short detection device.

The overall size can be made smaller.

FIG. 6 is a circuit diagram of an excitation circuit short-circuit detection device according to another embodiment of the present invention, and is an example of application to machine 1, a variable continuous T, in which the neutral point of the AC excitation circuit 37 is not exposed to the stationary side. U-V
The line-to-line short circuit detection resistor 21 that detects the voltage between the phases and between the v-W phases is connected, and this connection point is connected to the ground side of the limiting resistor RZ. Components that are equivalent to those in Fig. 1 are given the same reference numerals. I'm wearing it.

In this embodiment, when a ground fault occurs in the W phase, the voltage of the ■ phase increases to the voltage of the AC excitation circuit 37, but since the limiting resistor Rz is connected to the ■ phase, the voltage of the isolation amplifier of the detection unit 6 is connected to the ground. It is possible to suppress the voltage to a low level, prevent dielectric breakdown in the same part as in the conventional case, and improve reliability.

FIG. 7 is a circuit diagram showing an excitation circuit short circuit detection device according to still another embodiment of the present invention, in which an AC excitation circuit 3 without a neutral point is shown.
A three-phase bridge is constructed for the variable series '7B with 7% and 1%. Each U, V, and W phase of the AC excitation circuit 37 includes a limiting resistor/voltage dividing resistor R1 and a line short circuit detection resistor r1.
Which series circuits are connected to each other to form a Y-connected three-phase bridge.

The neutral point of this three-phase bridge is the ground fault detection"!Arl1.
It is grounded via the DC power supply 12 of 41 and the ground fault detection resistor r2. Therefore, the limiting resistor of the ground fault detecting device 41 is also used as a limiting resistor/voltage dividing resistor Rx, and the line short circuit detecting resistor rl is connected to the ground side of the limiting resistor as in the other embodiments.

However, in this embodiment, the relationship between the resistance values of the limiting resistor and the voltage dividing resistor Rr is different from that in the embodiment shown in FIG. Since the line short circuit is detected as if it had occurred, the threshold voltage V! of the line short circuit detection section E'Z40 shown in FIG. It is necessary to make the level sufficiently small.

〔Effect of the invention〕

As explained above, the present invention connects the line-to-line short-circuit detection resistor of the line-to-line short-circuit detection device to the ground side of the limiting resistor of the ground fault detection device. An excitation circuit short-circuit detection device can be obtained in which the voltage to ground of the isolation amplifier in the detection section can be suppressed to a low level, and dielectric breakdown in the detection section can be suppressed, thereby improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an excitation circuit short-circuit detection device according to an embodiment of the present invention, and FIGS. Figure, 4th
FIG. 5 is a circuit diagram of a conventional excitation circuit short-circuit detection device, FIG. 5 is a circuit diagram when a ground fault occurs, and FIGS. 6 and 7 are circuit diagrams of excitation circuit short-circuit detection devices according to other different embodiments of the present invention. It is a diagram. 1... variable speed generator, 4... cycloconverter,
6... Detection unit, 12... DC power supply, 37... AC excitation circuit, 4o... Line short circuit detection device, 41... Ground fault detection device, R1... Voltage dividing resistor, R2 ...Limiting resistance, rt...Line short circuit detection resistance, r2...Ground fault detection resistance. 2nd tea 3 figure broom 5 wide

Claims (1)

[Scope of Claims] 1. A line-to-line short-circuit detection device having a line-to-line short-circuit detection resistor whose one end is connected via a voltage dividing resistor to an AC excitation circuit that AC excites the rotor winding, and a limiting resistor in the excitation circuit. In the excitation circuit short-circuit detection device for a rotating electric machine, which has a ground fault detection device connected to a DC power source through Features: Excitation circuit short-circuit detection device for rotating electric machines. 2. In the product as described in claim 1 above, the series circuit of the voltage dividing resistor and the line short circuit detection resistor is a three-phase bridge, and the line short circuit detection resistor is a variable resistor. An excitation circuit short-circuit detection device for a rotating electrical machine, characterized in that the limiting resistor is connected between a neutral point of a phase bridge and a neutral point of the AC excitation circuit.