JPH0433549A - Brushless exciter field ground-fault trouble detector - Google Patents

Abstract

PURPOSE:To eliminate an erroneous operation due to a residual magnetic flux by demagnetizing, by a demagnetizing unit, the flux remaining in a detecting winding core after a trouble is removed. CONSTITUTION:If a trouble occurs, a current flows to a rotor side detecting winding 4, and a detector 6 detects it as a trouble. Here, after a generator is excited in a no load state, the generator is stopped as remained in a constant- excited state by the exciting current of an AC exciter corresponding to the exciting current. Since a voltage induced in an auxiliary winding 2 is AC and proportional to the rotating speed of the generator, a trouble current flowing to the winding 4 is gradually reduced as the rotating speed is reduced by the stopping operation of the generator. Accordingly, a magnetic flux passing through the core of the winding 4 becomes a gradually reducing AC magnetic flux, and its residual magnetic flux is converged to zero when the generator is stopped. Thus, demagnetization of the residual flux can be automated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a protection device for a brushless exciter, and more particularly to a device for detecting a field ground fault.

(Conventional technology) A conventional field ground fault detection device is shown in FIG.

In FIG. 2, 1 is an excitation winding of an AC exciter, 2 is an auxiliary winding wound into the armature winding slot of the AC exciter, and 3 is a full-wave rectifier circuit, which together with 2 constitute a DC auxiliary power supply. The negative side of the aftermath rectifier circuit 3 is grounded, and the positive side is connected to the negative side of the main machine field winding 5 through the rotor side detection winding 4. Since the main machine field winding 5 is not grounded, in a healthy state, no current flows through the rotor-side detection winding 4 even if voltage appears in the full-wave rectifier circuit 3. Now, if a ground fault occurs in the main machine field circuit, a circuit is formed that passes through the fault point and returns to the negative side of the aftermath rectifier circuit 3, so current flows through the rotor side detection winding 4 and flows to the rotor side. Magnetic flux is generated in the detection winding 4. At this time, a voltage is generated in the stator side detection winding 5 in the stator side facing the rotor side detection winding 4 in the form of a pulse due to the electromagnetic core, and the voltage is transmitted to the field magnetic field by the detection device 6. detected as a fault.

(Problem to be Solved by the Invention) However, even after the fault has been removed, a voltage is generated in the stator side detection winding 5 in a pulse form due to the residual magnetic flux remaining in the detection winding core. Malfunctions often became a problem, and the generator main engine was stopped and the rotor was suspended due to demagnetization.
There was a need for extensive work to disassemble the AC exciter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a highly reliable brushless exciter field ground fault detection device that is free from malfunctions due to residual magnetic flux.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the object stated in item 1, in the present invention, there is a A brushless excitation device consisting of a rotor side fault detection winding electrically connected to the rotor side, a stator side detection winding that generates a voltage due to the current flowing through the detection winding, and a detection means that detects a fault based on the detection winding voltage. The field ground fault detection device is configured to include a residual magnetic flux demagnetizer for the detection winding.

(Function) The present invention is configured as described in "-", in which the residual magnetic flux remaining in the detection winding core after fault removal is demagnetized by the degaussing device inside the brushless excitation device, and field ground fault fault detection without malfunction is achieved. The device can be realized.

(Example) An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, and the same parts as in FIG. 2 are denoted by the same reference numerals, and the explanation thereof will be omitted. In this embodiment, one end of the auxiliary winding 2 of the AC exciter armature winding slot is grounded, and the other end is connected to the rotor side detection winding 4.

Now, in the above configuration, the ground fault detection circuit of this embodiment functions as follows. When in good condition, an alternating current voltage is generated in the auxiliary winding 2, but since the main machine field winding 5 is not grounded, no current flows through the rotor-side detection winding 4 as in the prior art. Now, when a main machine field circuit ground fault occurs, current flows through the rotor-side detection winding 4 as in the conventional example, and in this embodiment, it becomes an alternating magnetic flux. (An AC excitation current will flow into the main excitation winding, but this magnitude is several mA.
The effect on the generator output voltage is negligible. ) This alternating current magnetic flux generates an alternating current pulse voltage in the main machine field winding 5 by electromagnetic induction, and the voltage is converted into a direct current pulse voltage similar to the conventional technology using the single-phase aftereffect rectifier circuit 3A, and the field winding is detected by the detection device 6. detected as a fault.

According to this embodiment, the detection winding core can be demagnetized as described below without disassembling or inspecting the AC exciter. After bringing the generator into a state of non-negative and positive excitation, stop the generator while keeping it in a constant excitation state with an AC exciter excitation current equivalent to the excitation current (if constant excitation is carried out to a sufficiently low speed, the generator will stop) (The voltage induced in the auxiliary winding 2, which is the power source for the rotor detection winding 4, is alternating current and proportional to the rotational speed of the generator.) The flowing fault current becomes an alternating current that gradually decreases as the rotational speed decreases due to the generator stopping operation. Therefore, the magnetic flux passing through the iron core of the rotor detection winding 4 also becomes an alternating magnetic flux that gradually decreases, so that the residual magnetic flux converges to zero (or almost zero) when the generator is stopped. As a result, when the generator was stopped for repair of the generator main field winding 5, demagnetization of the detection winding core was completed, and after the fault was recovered, the field ground fault fault detection circuit malfunctioned due to residual magnetic flux. There will be nothing left to do.

According to this embodiment, the aftermath rectifier circuit 3, which was conventionally installed inside the rotating body and subjected to strong centrifugal force, can be relocated to the stator side.

Therefore, the reliability of the semiconductor rectifier of the full-wave rectifier circuit 3, which originally has low mechanical strength, is dramatically improved. In addition, in the conventional technology, element failure detection of semiconductor rectifiers has been ignored because the element is located inside the rotating body, but in this embodiment, if the element is located on the stator side, constant monitoring is easily possible, and it is possible to detect element failure from the viewpoint of element failure. It also improves the reliability of the equipment.

As another embodiment, the stator side single-phase full-wave rectifier circuit 3
A circuit in which A is omitted can be considered.

By doing this, it is possible to reduce the space required for installing equipment on the stator side.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a field ground fault detection device for a brushless exciter that does not cause malfunctions due to residual magnetic flux, and it greatly contributes to the reliability of the brushless exciter. Furthermore, since the residual magnetic flux can be automatically demagnetized, there is no need to spend a lot of time and effort disassembling the brushless exciter to demagnetize the magnetic flux of the detection winding.

Even if we focus on improving the reliability of field ground fault detection equipment, we can not only eliminate malfunctions caused by residual magnetic flux, but also improve the mechanical This eliminates the need to apply strong centrifugal force to the weak rectifier, eliminates the risk of malfunction of the failure detection device due to failure of the rectifier, and greatly improves reliability.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a field ground fault detection device according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional field ground fault detection device. "... Excitation winding 2 of AC exciter. Auxiliary winding 3A of AC exciter armature slot. Single-phase aftereffect rectifier circuit 4... Rotor side detection winding 5... Stator side detection winding. 6...Detection device

Claims (1)

[Claims] An auxiliary power supply provided on the rotor of the AC exciter, a rotor-side failure detection winding electrically connected between the negative or positive side of the main machine field winding and the power supply, and the current flowing through the detection winding. In a brushless exciter field ground fault detection device consisting of a stator-side detection winding that generates a voltage and a detection means that detects a failure based on the detection winding voltage, a residual magnetic flux demagnetization device for the detection winding is provided. Features: Brushless exciter field ground fault detection device.