JP3081709B2 - Apparatus and method for detecting field ground fault of variable speed generator motor - Google Patents

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 ground fault in a variable speed generator motor whose rotation speed can be adjusted.

[0002]

2. Description of the Related Art A conventional constant speed machine (synchronous machine) having a constant rotation speed.
2 will be described with reference to FIG. In the figure, 11 is an exciting winding of a 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 is detected by the DC field ground relay Ry3. For example,
If 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
, The ground fault can be detected by the ground fault relay Ry3. When a field ground fault occurs at a 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 , The ground fault can be detected by the ground fault relay Ry3. In the case of a constant speed machine, most of the field circuit has a direct current of 1000 V or less, and an internal field ground fault is hardly a problem in terms of insulation technology.

[0003]

By the way, the field circuit of the variable speed generator-motor passes an alternating current (including direct current) in a certain 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, and requires higher insulation than the conventional constant speed machine, and the structure of the rotating body is complicated. Therefore, the recovery work differs greatly depending on whether the field ground fault has occurred internally or externally.However, the fault can only occur with a ground fault relay that collectively monitors the field ground fault current based on the same concept as before. 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 perform the recovery work.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object the field of a variable speed generator motor which can easily determine whether the ground fault point of the variable speed generator motor is inside or outside the generator motor. An object of the present invention is to provide a ground fault detecting device and method.

[0005]

In order to achieve the above object, a first aspect of the present invention relates to a variable speed generator motor capable of adjusting the rotation speed, wherein a ground brush attached to the generator motor shaft, A first ground fault relay for detecting a current flowing between the brush and the ground; and a second ground fault relay for detecting a current flowing between a neutral point of the excitation circuit of the generator motor and the ground. And According to a second aspect of the present invention, there is provided a method of detecting a field ground fault of a variable speed generator motor capable of adjusting a rotation speed, wherein a current flowing between a ground brush attached to the generator motor shaft and the ground and an excitation of the generator motor
When a current flowing between the neutral point of the circuit and the ground is detected, it is determined that an internal accident has occurred in the generator motor, and the current flowing between the neutral point and the ground of the excitation circuit of the generator motor is It is detected
Between the ground brush attached to the generator motor shaft and the ground
When no current flowing through the generator motor is detected, it is determined that an external accident has occurred in the generator motor.

[0006]

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

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an embodiment of the present invention, and shows a field circuit diagram of a cycloconverter system of a variable speed generator motor. In the figure, 1 is an exciting winding of a generator motor, 2 is a shaft of the generator motor, 3 is a ground brush,
9 is a hole CT, 5 is a brush, 6 is a cable, 7 is a power supply, 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.
Now, when a field ground fault occurs outside the variable speed generator motor as shown at point A, in FIG.
Since an accident current flows through the path of the hall CT9, the neutral point resistor 8, and the power supply 7, the field ground detection relay Ry2 operates, but the field ground detection relay Ry1 does not operate.

In the case where an internal ground fault has occurred at the variable speed generator-motor at the point B, as shown in FIG. 1, the excitation winding 1-the fault point B-the shaft 2-the ground brush 3-hole CT
Since the fault current flows on the path of 4-hole CT 9 -neutral resistor 8 -power supply 7 -cable 6 -brush 5 -excitation winding 1, the field ground fault detection relays Ry 1 and Ry 2 operate together.

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

Instead of providing Ry1, instead of recording Ry2 operation as a trigger, the waveform of the ground brush current is recorded and Ry2 is recorded.
2. Not only can the change before and after the operation be confirmed, but also the magnitude of the internal fault can be confirmed by the magnitude of the fault current.
Further, the present invention can be applied to a GTO type excitation circuit.

[0012]

As described above, according to the present invention, the current flowing through the grounding brush and the current flowing through the neutral point of the field circuit are simultaneously monitored, whereby the internal and external accidents of the generator motor can be clearly distinguished. As a result, it is possible to expedite the response at the time of accident recovery.

[Brief description of the drawings]

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

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

[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)

(57) [Claims] 1. A variable speed generator motor whose rotation speed is adjustable, a ground brush attached to the generator motor shaft, a first ground fault relay for detecting a current flowing between the ground brush and the ground, and A field ground fault detecting device for a variable speed generator motor, comprising: a second ground fault relay for detecting a current flowing between a neutral point and an earth of an excitation circuit of the generator motor. 2. A method for detecting a field ground fault of a variable speed generator motor capable of adjusting the number of revolutions, wherein a current flowing between a ground brush attached to the shaft of the generator motor and the ground, and
When a current flowing between the neutral point of the excitation circuit of the generator motor and the ground is detected, it is determined that an internal accident has occurred in the generator motor, and the neutral point between the excitation circuit of the generator motor and the ground is determined. The flowing current is detected and the connection attached to the generator motor shaft is detected.
A method for detecting a field ground fault of a variable speed generator motor, comprising determining that an external accident has occurred in the generator motor when a current flowing between the ground brush and the ground is not detected .