JPH0622600A - Apparatus and method for detecting field ground fault of variable speed dynamotor - Google Patents

Abstract

PURPOSE:To accurately distinguish an internal accident from an external accident of a dynamotor and to rapidly cope with at the time of recovering the accident by providing two ground-fault relays for respectively monitoring a current flowing to ground brush and a current flowing to a neutral point of a field circuit. CONSTITUTION:Since a fault current flows in a circuit of a power source 7, an accident point A, a Hall CT 9, a neutral point resistor 8 and the power source 7 if a field ground fault occurs out of a variable speed dynamotor, such as, for example, at point A, a field ground-fault detection relay Ry2 is operated. Since the fault current flows in a circuit of an exciting winding 1, a fault point B, a shaft 2, a ground brush 3, a Hall CT 4, the Hall CT9, the neutral resistor 8, the power source 7, a cable 6, a brush 5 and the winding 1, if an internal ground-fault of the motor occurs at the point B, field ground-fault detection relays Ry1, Ry2 are simultaneously operated. Then, the external fault is distinguished from the internal fault from the operating states of the relays Ry1, Ry2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for detecting a field ground fault in a variable speed generator-motor capable of adjusting the number of revolutions.

[0002]

2. Description of the Related Art A conventional constant-speed machine (synchronous machine) whose rotation speed is constant
The field ground fault detection method in FIG. 2 will be described with reference to FIG. In the figure, 11 is an exciting winding of the generator motor, 12 is a shaft of the generator motor, 13 is a ground brush, 16 is a cable, 17 is a thyristor, and 18 is a power cable. Since the field circuit is a DC circuit, the field ground fault accident is detected by the DC field ground fault relay Ry3. For example,
When a field ground fault occurs at point A outside the generator motor, the fault current is thyristor 17, cable 16, fault point A, ground fault relay Ry3, cable 16, thyristor 17.
Since it flows through the closed circuit of, the ground fault can be detected by the ground relay Ry3. When a field ground fault accident occurs at point B inside the generator motor, the excitation winding 11, the fault point B, the generator motor shaft 12, the ground brush 13, the ground fault relay Ry3, the cable 16, the excitation winding 11 are included. Since it flows through the closed circuit of, the ground fault can be detected by the ground relay Ry3. In the case of a constant speed machine, most of the field circuit is DC of 1000 V or less, and the internal field ground fault does not pose a problem in terms of insulation technology.

[0003]

By the way, the field circuit of the variable speed generator-motor is flowing an alternating current (including direct current) in a constant frequency range. Therefore, the DC ground fault relay Ry3 used in the constant speed machine cannot be used. Further, the field voltage has three phases of 4000 to 5000 V, which requires high insulation and makes the structure of the rotating body complicated as compared with the conventional constant speed machine. Therefore, the recovery work will differ greatly depending on whether the field-to-ground fault has occurred internally or externally.However, the same concept as before is used to detect the fault only with a ground-fault relay that collectively monitors the field-to-ground fault current. Even if it occurred, it was not possible to identify whether this accident was an internal accident or an external accident of the generator motor, and there was a problem that it took time to restore.

The present invention has been made in view of the above circumstances, and an object thereof is a field of a variable speed generator / motor, which can easily identify whether a ground fault accident point is inside or outside of the generator / motor. An object is to provide a ground fault detection device and method.

[0005]

In order to achieve the above object, the first aspect of the present invention is to provide a variable speed generator-motor of which the number of revolutions can be adjusted, and a grounding brush attached to the generator-motor shaft and the grounding brush. A first ground fault relay that detects a current flowing between the brush and the ground, and a second ground fault relay that detects a current flowing between the neutral point of the exciting circuit of the generator motor and the ground are provided. And According to a second aspect of the present invention, there is provided a method for detecting a field ground fault of a variable speed generator-motor capable of adjusting a rotation speed, wherein an internal of the generator-motor is detected by detecting a current flowing between a ground brush attached to the generator-motor shaft and the ground. It is characterized in that it is judged as an accident, and by detecting the current flowing between the neutral point of the exciting circuit of the generator motor and the ground, it is judged as an external accident of the generator motor.

[0006]

In the field circuit of the variable speed generator / motor, a fault current flows to the neutral point in an external ground fault of the generator / motor. Also, in an internal accident of the generator motor, the current flowing from the field circuit to the shaft flows to the neutral point via the ground brush,
The inside and outside of the field-to-ground fault point can be easily identified simply by monitoring the presence or absence of current flowing in the ground brush and the presence or absence of current flowing in the neutral point of the field circuit.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention, which is a field circuit diagram of a cycloconverter system of a variable speed generator-motor. In the figure, 1 is the excitation winding of the generator motor, 2 is the shaft of the generator motor, 3 is the ground brush, 4,
Reference numeral 9 is a Hall CT, 5 is a brush, 6 is a cable, 7 is a power source, 8 is a neutral point resistor, and Ry1 and Ry2 are field ground fault detection relays.

Next, the operation of this embodiment will be described.
When a field ground fault accident occurs outside the variable speed generator motor as at point A, in FIG. 1, the power source 7-accident point A-
The field ground fault detection relay Ry2 operates, but the field ground fault detection relay Ry1 does not, because an accident current flows in the path of the Hall CT9-neutral point resistor 8-power source 7.

When an internal ground fault occurs in the variable speed generator motor at point B, the excitation winding 1-accident point B-shaft 2-ground brush 3-hole CT in FIG.
Since a fault current flows in the path of 4-hole CT9-neutral point resistor 8-power supply 7-cable 6-brush 5-excitation winding 1, the field ground fault detection relays Ry1 and Ry2 both operate.

As described above, according to the present embodiment, the operation of only the field ground fault detection relay Ry2 determines the external accident, and the field ground fault detection relays Ry1 and Ry2 both operate to clearly determine the internal accident. be able to. Therefore, by simultaneously monitoring the current of the ground brush and the current flowing through the neutral point of the field circuit, it is possible to clearly distinguish the internal accident and the external accident of the generator motor.

Instead of providing Ry1, Ry2 operation is used as a trigger to record the waveform of the ground brush current,
2 In addition to confirming the change before and after the operation, the magnitude of the internal accident can be confirmed by the magnitude of the accident current.
It can also be applied to a GTO type excitation circuit.

[0012]

As described above, according to the present invention, by simultaneously monitoring the current flowing through the ground brush and the current flowing through the neutral point of the field circuit, the internal accident and the external accident of the generator motor can be clearly distinguished. Therefore, it is possible to speed up the response at the time of accident recovery.

[Brief description of drawings]

FIG. 1 is a field circuit diagram of a cycloconverter system of a variable speed generator-motor according to an embodiment of the present invention.

FIG. 2 is a conventional constant-speed field circuit diagram.

[Explanation of symbols]

1 ... Excitation winding, 2 ... Shaft, 3 ... Ground brush, 4, 9
... current transformer, 5 ... brush, 6 ... cable, 7 ... power supply, 8 ...
Neutral point resistor, Ry1, Ry2 ... Ground fault relay.

Claims (2)

[Claims] 1. A variable-speed generator-motor of which the number of revolutions can be adjusted, a grounding brush attached to the generator-motor shaft, a first ground-fault relay for detecting a current flowing between the grounding brush and the ground, A field ground fault detector for a variable speed generator motor, comprising: a neutral point of an exciting circuit of the generator motor; and a second ground fault relay that detects a current flowing between the ground. 2. A method for detecting a field ground fault of a variable speed generator-motor capable of adjusting a rotation speed, wherein an inside of the generator-motor is detected by detecting a current flowing between a ground brush attached to the generator-motor shaft and the ground. It was judged as an accident, and again
A method for detecting a field-to-ground fault of a variable-speed generator-motor, comprising determining an external accident of the generator-motor by detecting a current flowing between a neutral point of the exciting circuit of the generator-motor and the ground.