JPH06313776A - Detector of ground fault current of grounding line - Google Patents

Abstract

PURPOSE:To detect a ground fault accident without being affected by noise and to send a detection signal by an optical fiber without using a power source. CONSTITUTION:A rectifier circuit 11 is connected to a current transformer CT1 for detecting a grounding line current and thereby the CT1 obtains a circuit power source Vcc simultaneously with detection of the current. A secondary current of the current transformer CT1 is detected by current transformers CT1 and CT2, outputs thereof are so inputted to filter circuits 131 and 132 as to be made reverse in polarity to each other and noise is removed. They are rectified by half-wave rectifier circuits 141 and 142 and compared with a reference voltage Vo by comparator circuits 151 and 152, a light-emitting diode PD1 is thereby made to emit a light and a ground fault current detection light signal pulse is sent to an accident point locating-monitoring device 8 through an optical fiber 5. Although a DC component is contained in addition to an AC component in a ground fault current, the ground fault current can be detected at the first wave thereof irrespective of the polarity of the DC component, since the outputs of the current transformers CT1 and CT2 are so outputted as to be reverse in the polarity and are subjected to half-wave rectification and compared with the reference voltage respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground wire ground fault current detector used for a device for locating a ground fault accident point for each gas section in a gas insulation switchgear at a ground fault accident.

[0002]

2. Description of the Related Art When an internal discharge occurs in a gas insulated switch (GIS), high frequency pulse current or voltage, ultrasonic waves, discharge light, discharge decomposition product gas, spatial harmonic electromagnetic wave, short circuit current magnetic field, etc. are generated.

An electromagnetic coupling sensor, a decomposed gas sensor, a discharge sensor, an external magnetic field sensor, an electromagnetic sensor, etc. are used for GIS failure detection and failure point localization.

Conventionally, in order to detect a ground fault accident in a GIS tank by using arc light, it is necessary to detect the ground fault current in addition to detecting the arc light. There is also a method of detecting the ground fault current by incorporating the output from the protection relay circuit, but as shown in FIG. 5, the _{one in} which the ground fault current flowing in the ground line 2 of CIS1 is directly detected by the current transformer CT1. Will make it easier to locate accident points.

[0005]

SUMMARY OF THE INVENTION When the above-mentioned conventional ground line ground fault current is detected by a current transformer, the ground line is very noisy, and the output signal line 9 of the current transformer is caused by electromagnetic noise at the time of ground fault. When noise enters, it may cause damage or malfunction of the electronic circuit for signal processing.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to detect a ground fault accident without being affected by noise and to detect it without using a power source. It is an object of the present invention to provide a ground line ground fault current detector capable of sending a signal to a fault location monitoring device through an optical fiber and having no power supply malfunction.

[0007]

In order to achieve the above object, a ground wire ground fault current detector according to the present invention comprises a rectifier circuit for rectifying the output of a current transformer for detecting the ground line current and outputting a circuit power supply. , First and second secondary current detecting current transformers which detect the secondary currents of the current transformers and output them in opposite polarities, and remove noise from the outputs of the first and second current transformers First to do
And a second filter circuit and first and second half circuits for half-wave rectifying the outputs of the first and second secondary current detecting current transformers from which noise is removed by the first and second filter circuits. A wave rectifier circuit and means for detecting that the outputs from the first and second half-wave current circuits exceed a certain value and sending a ground fault current detection signal as an optical pulse.

[0008]

When the ground line current detecting current transformer detects a ground fault current, the output is rectified and power is instantaneously supplied to a circuit element such as an IC. The first and second current transformers for secondary current detection detect the secondary currents of the current transformers for ground line detection and output them with polarities opposite to each other. If the outputs of the first and second current transformers for secondary current detection are half-wave rectified and it is not detected that the output exceeds a certain value, the DC component contained in the ground fault current will be positive or negative. Even if there is, the first wave of the AC component of the ground fault current can be detected regardless of the polarity.

Since the noise included in the outputs of the first and second secondary current detecting current transformers is absorbed and removed by the first and second filter circuits, the ground fault current can be detected without the influence of noise. . Moreover, since the detection signal is sent as an optical pulse, electromagnetic noise is not transmitted.

[0010]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of an accident location monitoring system, and FIG. 2 shows the details of the ground fault CT detector in the system.

In FIG. 1, 1 is a gas insulated switch (GI).
S) 2 is a ground wire of GIS, 3 is an optical fiber for detecting an arc light that detects an arc light generated in each gas section of GIS, 4 is a clamp type current transformer C that detects a current of the ground line 2
A ground wire CT detector connected to T ₁ , 5 is an optical fiber for transmitting the signal of the detector 4, 6 is a switch operation detector for detecting the switch operation of each gas section of GIS 1, and 7 is a detector 6
Optical fiber for transmitting the signal of
An accident point location monitoring device that receives a signal from 7 and locates an accident point is shown.

Referring to FIG. 2, 11 is a diode bridge circuit for obtaining the circuit power supply Vcc from the output of the current transformer CT ₁ .
It is composed of a zener diode ZD ₁ for constant voltage, a diode bridge for rectification, a smoothing capacitor C _V , and a power supply voltage V
cc is kept at a constant voltage by a zener diode ZD ₁ .

[0013] CT _2, CT ₃ is the secondary current I ₁ current transformer CT ₁
Is a current transformer for detecting the current and determining the current value.
_{When 1} is small, the primary side of CT ₂ and CT ₃ are used as the same N turns. Reference numerals 12 ₁ and 12 ₂ denote ground fault detection circuits for detecting positive and negative currents of the ground fault current.
₁ and 13 ₂ , ideal diode half-wave rectifier circuits 14 ₁ and 14 ₂ and voltage comparison circuits 15 ₁ and 15 ₂ .

The filter circuits 13 ₁ and 13 ₂ are current transformers C.
It is composed of a parallel circuit of capacitors C ₁ and C ₂ connected to output terminals K and L and L and K of T ₂ and CT ₃ and voltage dividing resistors R ₁ and R ₂ , and a grounding line with capacitors C ₁ and C _2. After the high frequency current noise contained in 2 is absorbed, it is output from the voltage dividing resistors R ₁ and R ₂ to the half-wave rectifier circuits 14 ₁ and 14 ₂ .

The half-wave rectifier circuits 14 ₁ and 14 ₂ are ideal diode non-inverting circuits, which are constructed by connecting diodes D ₁ and D ₂ and a resistor R ₃ to an operational amplifier A ₁ as shown in the figure, and a filter circuit 13 ₁ , 13 ₂ ideally performs half-wave rectification. The voltage value comparison circuits 15 ₁ and 15 ₂ are half-wave rectifier circuits 1
The half-wave rectified signals from 4 ₁ and 14 ₂ are compared with the reference voltage Vo and turned on or off.

PD ₁ is a light emitting diode which is connected to a power source Vcc through a resistor and emits light when the voltage value comparison circuits 15 ₁ and 15 ₂ are turned on, and its optical signal is transmitted to an accident point location monitoring device 8 through an optical fiber 5. It has become so.

Next, the operation of the above embodiment will be described with reference to FIG. When a ground fault occurs in the tank of GIS1 and a ground fault current Io flows through the ground line 2, the current transformer CT ₁ detects this ground fault current and the diode bridge circuit 11 receives the secondary current Io.
₁ is supplied, and a stable power supply Vcc voltage is output before the output voltages of the half-wave rectifier circuits 14 ₁ and 14 ₂ exceed the reference voltage Vo.

Meanwhile, the secondary current I ₁ of the current transformer CT ₁ is detected by the current transformer CT _2, CT _3, the filter 13 _1, 13 ₂ is inputted to each of the noise is removed, the current transformer CT _Since the output of ₃ is output with the opposite polarity, the output voltages a and b of the ideal diode half-wave current circuits 14 ₁ and 14 ₂ are as shown by the solid line and the broken line.

The output voltages a and b are compared by the comparison circuits 15 ₁ ,
15 ₂ is compared with the reference voltage Vo, and when it exceeds the reference voltage, it is turned on to cause the light emitting diode PD ₁ to emit light and notify the accident point location monitoring device.

As shown in FIG. 4, the ground fault current is composed of a direct current component and an alternating current component and is not a symmetrical current, but the positive and negative currents are detected by the ground fault current detection circuits 12 and 12 ₂ as described above. Therefore, the ground fault current can be detected by the first wave regardless of whether the DC component is positive or negative.

[0021]

Since the present invention is configured as described above, it has the following effects.

(1) Since the ground fault accident detection signal can be sent by the optical fiber, electromagnetic noise is not transmitted to the accident point locating and monitoring device and malfunction does not occur.

(2) Since the power supply for the detection circuit is supplied from the current transformer for detecting the ground line current, it is not necessary to bring the circuit power supply from the outside, and therefore the handling is easy.

(3) Since the noise contained in the current value measured by the current transformer is absorbed by the CR filter circuit, there is no malfunction due to the high frequency noise contained in the ground line current.

(4) The current value of the first wave of the asymmetric ground fault current including the DC component current can be detected without fail.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an accident point location monitoring system according to an embodiment.

FIG. 2 is a circuit diagram showing a ground line CT detector in the embodiment.

FIG. 3 is a waveform diagram illustrating the operation of the embodiment.

FIG. 4 is a ground fault current waveform diagram.

FIG. 5 is a configuration diagram of a conventional accident point location monitoring system.

[Explanation of symbols]

1 ... Gas insulated switchgear (GIS) 2 ... Ground wire 3 ... Arc light detection fiber 4 ... Ground wire CT detector 5, 7 ... Optical fiber 6 ... Switch operation detector 8 ... Accident point location monitoring device 9 ... Signal Line 11 ... Diode bridge circuit 12 ₁ , 12 ₂ ... Ground fault detection circuit 13 ₁ , 13 ₂ ... Filter circuit 14 ₁ , 14 ₂ ... Ideal diode half-wave rectifier circuit 15 ₁ , 15 ₂ ... Voltage value comparison circuit CT ₁ ~ CT ₃ Current transformer DB ₁ Diode bridge PD ₁ Light emitting diode ZD ₁ Zener diode

Claims (1)

[Claims] 1. A rectifier circuit for rectifying the output of a current transformer for detecting a ground wire current and outputting a circuit power supply; and first and second rectifier circuits for detecting a secondary current of the current transformer and outputting them with opposite polarities. A secondary current detecting current transformer, first and second filter circuits for removing noise from the outputs of the first and second secondary current detecting current transformers, the first and second filters First and second half-wave rectifying circuits for half-wave rectifying the first and second secondary current detecting current transformer outputs from which noise has been removed by a circuit, and the first and second half-wave current circuits And a means for sending a ground fault current detection signal in the form of an optical pulse when the output from the device exceeds a certain value, and a ground line ground fault current detector.