JPH0638090B2 - Improved ground fault detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Object of the Invention) The present invention relates to a ground fault detection apparatus for detecting occurrence of a ground fault at one different place.

In a field circuit of a synchronous machine, when a ground fault occurs at two different parts, a large short-circuit current flows and the field circuit components (exciter, field breaker, field resistance, etc.) ) Is
Receive serious damage.

Similarly, in the transformer, if a ground fault occurs in the primary winding, the secondary winding, or between the primary winding and the secondary winding, a large short circuit current damages the transformer. At the same time, the action peculiar to the transformer for converting the magnitude of the voltage cannot be performed. For this reason, it is essential to detect two ground fault phenomena in electrical equipment in advance.

Since there is no suitable detection method for directly detecting such a ground fault at two locations, one location of the circuit is grounded in advance via a relay, and when a ground fault occurs at another location of the circuit, this is detected. However, measures are being taken.

Then, in order to detect the one-point ground fault as described above, (1). As shown in FIGS. 1 (a) and 1 (b), respectively, an end portion for grounding an earth is provided in a circuit of an electric device, and a DC voltage source or an AC voltage source is provided between the end portion and the earth. And detecting a one-point ground fault by causing a detection current to flow when a ground fault occurs in another part of the circuit.

(2). As shown in FIG. 1 (c), an end portion that uses the internal power source 2 (for example, the exciter voltage in the field circuit of the synchronous machine, the terminal voltage in the transformer, etc.) in the electrical equipment and grounds it. 5
When the resistors R ₁ and R ₂ are connected between the voltage and the voltage and the relay 1 is provided between the end 5 and the ground, and a ground fault occurs in another portion of the circuit, When current flows through relay 1, 1
A method for detecting a point-to-ground fault is used.

In the method (2), the resistors R ₁ and R ₂ are connected between the end 5 and the power source, respectively, as shown in FIG. 1 (c). When a ground fault occurs, a bridge circuit is formed via the ground (E is the voltage value of the voltage power supply 2, and R ₃ and R ₄ are the ones of the circuit that has a one-point ground fault. Each resistance value between the part and the power supply 2), relay 1
Since this corresponds to the connecting portion of the bridge, the short-circuit current does not flow directly to the relay 1, but the current according to the following formula flows, and the relay is not destroyed by the short-circuit current and can detect a one-point ground fault. That is, in order to prevent the breakdown of the relay, the resistors R ₁ and R ₂ are used to form a bridge circuit as shown in FIG. 1 (c).

E (R ₂ R ₃ −R ₁ R ₄ ) / {R ₁ R ₃ (R ₂ + R ₄ ) + R ₂ R ₄ (R ₁ + R ₃ )} By the way, in the method of (1), a separate power source is used. It is complicated to provide, and especially when a DC voltage source is used, a high voltage is usually used, so it is necessary to consider insulation breakdown and electric shock accidents in the circuit inside the electrical equipment. When a source is used, for example, when it is used in a field circuit of a synchronous machine, a distributed current existing between the field coil and the bearing of the synchronous machine causes a constant current to flow through the bearing. If this continues for many years, the surface of the bearing will be damaged, and there is a risk of an accident.

The above method (2) does not have the above danger, but in this method, in the case of a one-point ground fault as described above, a balanced current due to a bridge current will flow.
In the figure (c), when R ₃ / R ₄ = R ₁ / R ₂ is in the vicinity, the current flowing through the relay is extremely small, so the relay is extremely sensitive. Will be required.

By the way, in recent years, in a synchronous machine exciter, a brushless system is used in which an output from a rotating electric element of an exciter machine is directly flowed to a rotor of a synchronous machine without using a brush.

However, in such a brushless system, since the field circuit itself is rotating, in the systems of (1) and (2), the first (a), (b), ( c) Since it is impossible to read the indication of the voltmeter or the ammeter or the relay while the rotating armature rotates by installing the detection circuit shown in the figure,
After all, in the brushless method, it was impossible to use the conventional detection method.

The present invention detects the ground fault current applicable to not only the synchronous machine adopting the brushless method but also the rotating armature of the synchronous machine adopting the brushless method while relying on the method (2). It is also an object to provide a method of doing so.

(Structure of the Invention) As shown in FIG. 2, the present invention provides an end portion 5 connected to the ground in a field circuit of a rotating armature of a synchronous machine, and supplies power to both sides of the end portion and to the field circuit. The light emitting devices 11 and 12 are respectively connected between the two ends connected to, and photoelectric conversion devices 31 and 32 for detecting the light amount from each of the light emitting devices 11 and 12 are provided in an external stationary state. This is an improved ground fault detection device that detects the output difference between the photoelectric conversion devices 31 and 32 by the detection unit 41, and thereby determines whether or not the current is conducted to the end portion 5 connected to the ground.

In FIG. 2, the end 5 in the rotating field circuit is connected to the ground by connecting the end 5 to the rotating armature of the synchronous machine,
The armature will be connected to earth via a bearing and a spindle for it.

Further, the power supply 2 for the rotating armature of the brushless synchronous machine corresponds to the field circuit of the rotating armature of the exciter machine.

On the other hand, the photoelectric conversion devices 31 and 32 are installed in a stationary state outside the rotary armature.

In the structure shown in FIG. 2, when one portion 6 of the field circuit of the rotating armature is grounded through the rotor and a supporting shaft for the same, a ground is provided between the end 5 which is connected to the ground in advance. Since the fault current is conducted, a difference occurs between the current i ₁ flowing through the light emitting device 11 and the current i ₂ flowing through the light emitting device 12 by the amount of the ground fault current i _g flowing. That is, i ₁ −i ₂ = i _g holds.

Since the luminous flux generated by the light emitting device is related to the energy consumed for light emission, the luminous flux generated by the light emitting devices 11 and 12 is the current i.
₁ and i ₂ , the luminous flux is larger as each current is larger.

Therefore, when there is no ground fault in the field circuit in the rotating armature of the synchronous machine, i ₁ = i ₂ holds, and the light fluxes from the light emitting devices 11 and 12 are equal, so that the photoelectric conversion device Since the voltages E ₁ and E ₂ generated at 31 and 32 are also equal, the detection value remains at 0 in the detection unit 41.

On the other hand, when a ground fault occurs at the one end 6 of the field circuit in the rotating armature of the synchronous machine, the ground fault current I _g is conducted through the rotating armature and its supporting shaft. , Light emitting device 1
Since the current i 1 which conducts ₁ and i ₂ which conducts the light emitting device 12 are equal, the luminous fluxes received by the photoelectric conversion devices 31 and 32 are also not equal, and the voltage E generated thereby is generated.
_{Since 1} and E ₂ are also equal to each other, the detection unit 41 displays E ₁ −E ₂
Is detected.

That is, the output difference between the photoelectric conversion devices 31 and 32 appears in the differential detection unit 41 as the ground fault occurs, and the ground fault is detected and displayed on the display unit 42.

In this case, as shown in FIG. 3, the light emitting devices 11 and 12 are rotating together with the rotating armature 10, and the photoelectric conversion device 3
1, 32 are in a stationary state.

The photoelectric conversion devices 31 and 32 do not always receive the light from the rotating light emitting devices 11 and 12. For example, as shown in FIGS.
Light is often received when 2 is in a specific rotational position.

In such a case, the light from the light emitting device 11 is transmitted to the photoelectric device 31.
Similarly, it is desirable that the light from the light emitting device 12 is synchronized so that the light from the light emitting device 12 is received by the light emitting device 32. (It is necessary to separately provide a circuit for averaging the output values from 31, 32 or averaging the output from the detection unit 41).

In the above light emitting device, a light emitting diode (LED) has high sensitivity, emits light with a small current, and the luminous flux amount is proportional to the current value. Therefore, in the device of the present invention, the currents i ₁ and i
It is convenient in that the difference of ₂ is easy to detect.

However, the light emitting device is not limited to the light emitting diode, and a tungsten lamp can be used, for example.

Also in the device of the present invention, as in the case of FIG. 1 (c), the end portion 5 previously connected to the ground and the portion 6 having a one-point ground fault constitute a connecting portion of the bridge circuit. Also for this purpose, it is necessary to have resistances or impedances Z ₁ and Z ₂ between both sides of the end portion 5 and both ends of the power source 2.

In particular, when the light emitting device itself has a constant resistance or impedance, a bridge circuit can be formed by this, so as shown in FIG. 1 (c), particularly connect a resistance (impedance). Is unnecessary.

That is, in the present invention, it is often better to connect a resistance or an impedance between both sides of the end 4 and both ends of the power source 2, but this is not an essential requirement for the configuration of the invention.

Further, particularly in FIG. 2, when Z ₁ / Z ₃ = Z ₂ / Z ₄ (Z: impedance including resistance value) is established, the circuit in the circuit is the same as in the case of FIG. 1 (c). be at fault locations Te occurs at the site 6, the photoelectric conversion device 31 bridges not conduct becomes grounding current i _g an equilibrium that constitutes the ground fault circuit, since equal voltages E _1, E ₂ by the same 32, the end The detector 41 is also 0
May be displayed and eventually the ground fault may not be detected.

However, this point generally applies to the rotating armature of the synchronous machine when the light emitting device is designed so that the magnitudes of the currents i ₁ and i ₂ change and the internal resistance also changes. The voltage value of the field circuit of the exciter, which is the power source for the field circuit, always changes in a sine wave state, and the state where the above equilibrium equation is established is immediately established even if it is established momentarily. Since the balance is lost due to such a change in the power source and the above balance equation is not established, it is possible to prevent detection omission due to the balance of the bridge circuit.

(Effects of the Invention) In the present invention, the current from the power supply is once converted into optical energy, and this is detected by the light emitting element. Therefore, the ground fault phenomenon in the field circuit in the rotating armature of the synchronous machine is detected. Can be detected by the detector on the stator side through photoelectric conversion.

Moreover, if the amplification factor of the photoelectric conversion device is increased and the sensitivity is increased, even if the ground fault current i _g (= i ₁ −i ₂ ) is minute, a sufficiently large display value is displayed in the detection unit 41. It can be obtained, and the labor of obtaining a highly sensitive relay like a conventional device is unnecessary.

Moreover, in the ground fault detection device using the relay shown in FIG. 1 (c), when the relay 1 fails and does not operate, the relay 1 does not normally operate even if a one-point ground fault occurs, so it is as if It is easy to illusion that there is no 1-point ground fault. In other words, with the detection device using the relay shown in FIG. 1 (c), it is difficult to determine whether the relay can operate normally or has failed.

On the other hand, in the device of the present invention, the light emitting devices 11 and 12 have already been turned on and the outputs E ₁ and E ₂ proportional to the light emitting devices 11 and 12 have been detected, so that the device operates normally. Whether or not it can always be determined.

Furthermore, as described above, since the voltage generated by the field circuit in the armature of the exciter fluctuates in a limited manner, when a light emitting device whose internal resistance changes as the input current changes is used, Therefore, it is possible to prevent detection omission due to the balance of the bridge circuit.

As described above, since the ground fault detection device of the present invention has various advantages as compared with the conventional ground fault detection device, the present invention can be evaluated as extremely valuable.

[Brief description of drawings]

1 (a), 1 (b), 1 (c): Circuit diagram of conventional ground fault device FIG. 2: Circuit diagram of ground fault detection device of the present invention FIG. 3: Rotating armature Top view showing the positional relationship between the light emitting device provided on the side of the photoelectric conversion device and the photoelectric conversion device provided on the side of the stator FIG. 4: Graph showing the output of each photoelectric conversion device 1 ... Relays 11, 12, ... ... Light emitting device 2 ... power supply, 31, 32 ... photoelectric conversion device 41 ... detection part, 42 ... display part 5 ... end part where ground is installed 6 ... part where one point ground fault occurs in circuit 7 ... Block diagram of the entire electric equipment circuit 8 ... Voltmeter or ammeter, 9 ... Switch 10 ... Rotating armature

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-60-178371 (JP, A) JP-A-55-80067 (JP, A)

Claims (3)

[Claims] 1. A rotary armature of a synchronous machine, wherein an end connected to ground is provided in a field circuit, and the light emitting device is provided between both sides of the end and both ends connected to a power source for the field circuit. In the external stationary connection, each is provided with a photoelectric conversion device that senses the amount of light from each of the above-mentioned light emitting devices, and the output difference between both photoelectric conversion devices is detected. Improved ground fault detector for determining whether or not there is continuity 2. An improved ground fault detecting device according to claim 1, wherein a light emitting diode is used as the light emitting device. 3. An improved ground fault detecting device according to claim 1, wherein a tungsten lamp is used as the light emitting device.