KR200201999Y1 - Insulation detector for ac furnace - Google Patents

Abstract

The present invention relates to an alternating current (AC) furnace insulation detection device for detecting the insulation of the secondary circuit of the alternating current (AC) furnace to ensure safety at all times during the operation of the furnace. The insulation detection device of the present invention generates a high voltage and high frequency pulse for each of the R, S, and T phases according to the supplied power and converts the input AC power into the required operating power. The pulse generator to measure, the pulse output unit to press the generated pulse to the insulation resistance of the transformer secondary circuit, and the leakage current of the insulation resistance measured when the insulation detection selection switch is "ON" by the inspector Operational amplifier that amplifies to a certain size by input and amplifies the insulation state through the leakage current, and insulation state is poor according to the meter and judgment result that indicates the insulation detection selection switch and the leakage current amount as a guide so that the inspector can know. It is composed of an operation display unit having a buzzer light for generating an alarm to notify.

Description

AC Furnace Insulation Detection Device

1 is a partial cross-sectional actual view of a typical AC furnace.

2 is a block diagram showing an AC furnace insulation detection apparatus according to a preferred embodiment of the present invention.

(A) is a front view of the set which shows the insulation detection apparatus of FIG. 2, (b) is a rear view.

4 is an equivalent circuit diagram of the insulation detection device of FIG.

* Explanation of symbols for main parts of the drawings

21: electric furnace 22: secondary insulation resistance

23: disconnector 24: vacuum breaker

25: furnace transformer 26: auxiliary relay

27: power supply 28: pulse generator

29: pulse output section 30: operational amplifier section

31: operation display unit

The present invention relates to an AC (electric furnace) insulation detection device, and more specifically, to detect the insulation state by measuring the leakage current of the insulation resistance located on the secondary side of the transformer to monitor the electrical insulation state of the secondary circuit of the furnace The present invention relates to an AC electric furnace insulation detection device that can be displayed.

In general, electric furnaces for use in the manufacture of electrothermal chemicals, refining, melting, and heat treatment of metals utilize the thermal effect of current. The furnace transformer secondary circuit of an alternating current furnace using alternating current (AC) current is electrically insulated. The furnace transformer is a specially designed transformer (TR) for supplying arc power to the electric furnace. However, scale and dust penetrate into the insulator due to the vibration of the mast caused by the electromagnetic force generated during the operation of the electric furnace, thereby lowering the electric insulation and causing the breakdown of the insulator during operation. This causes damage to the furnace transformer secondary circuit, which reduces the productivity and risks of safety accidents. In addition, the trend of electric furnace facilities is to promote energy and sexual energy and pursue long life of equipment, and the method of regular inspection is rapidly developed into an on-line condition monitoring system. Considering the importance of facilities due to the weak surrounding conditions of the secondary circuit of the furnace, the development of a device for checking the insulation state of the furnace was required.

Therefore, the object of the present invention is to insulate by using the leakage current measured in the electrical insulation resistance of the secondary circuit of the furnace transformer in order to ensure the safety and check the condition of the insulation through regular checks during the operation of the furnace. An object of the present invention is to provide an insulation detection apparatus for alternating current (AC) electricity that can detect a condition and notify it.

The AC furnace insulation detection device of the present invention for achieving the above object is a device for detecting the electrical insulation state of the secondary circuit of the furnace transformer of the AC furnace, to supply the input AC power supply to the required operating power of each configuration Pulses for three phases according to the power supply unit and the power supplied from the power supply unit, and the leakage current flowing through the three-phase insulation resistors (R _R , R _S , R _T ) located at the secondary side of the furnace transformer. A pulse generator to measure, a pulse output unit to press the pulse generated from the pulse generator to the three-phase insulation resistances R _R , R _S , and R _T , and in the insulation detection selection state, the pulse generator Amplification of the leakage currents for the three phases measured by a predetermined magnitude, the operation amplifier to determine the insulation state by comparing with the reference value, and the insulation detection selection, the insulation state determination result of the operation amplifier It includes an operation display unit for displaying.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a partial cross-sectional view of a typical AC furnace. The furnace transformer, the periphery transformer 1 used in the electric furnace, supplies arc (ARC) power into the electric furnace. The furnace transformer generates 22KV of the primary side voltage and 500 ~ 800V of the secondary side, so that a large voltage difference occurs between the primary side and the secondary side, and has a large current capacity of 30-100 MVA. Arc power in the electric furnace refers to the electrical energy generated by the electrical circuit configuration between the scrap metal in the electric furnace and the electrode. Secondary bus bar (Bus Bar) (2) is a transformer (1) secondary bus is a connection point with the insulation detection device of the present invention. The wall insulator 3 electrically insulates the wall bracket 4 supporting the transformer 1 secondary bus 2 and the water cooling cable 5. Here, the water cooling cable 5 is a cable for supplying power to the electric furnace. In addition, the intermediate insulator 7 is an electrical insulator between a mast, which is an electrode elevating device, and a copper pipe 6. The copper pipe 6 supplies power to the electrode holder 8 that supports the arc power electrode 9 in the electric furnace.

The apparatus of the present invention for detecting the electrical insulation state of the electric furnace as shown in FIG. 1 is shown in FIG.

2 is a configuration diagram showing an AC electric furnace insulation detection apparatus according to the present invention. As shown in the drawing, the insulation detection device of the present invention has an insulation resistance (R _R , R _S , R _T ) with respect to three-phase (R, S, T) of the AC power source of the electric furnace 21. A vacuum circuit breaker for protecting a load circuit below the secondary side of the transformer 25 by breaking the circuit in the event of an accident due to the load current by disconnecting the secondary side insulation resistance 22, the disconnection switch 23, and the load current; VCB) 24 is provided. The insulation detection device of the present invention also includes an auxiliary relay 26 that is "ON" and "OFF" depending on whether the vacuum circuit breaker 24 is operated, and a power supply unit 27 that is an operating power supply source of each configuration. Equipped with. The power supply unit 27 includes a power supply controller 271 for converting an input AC power into a required operating power and outputting the same, a transformer 272 for transmitting an input AC power from a primary side to a secondary side, and two of the transformers 272. A silicon controlled rectifier 273 is connected to the vehicle side and adjusts the voltage to the pulse voltage required by the power supply controller 271. The power supply 27 is connected to a pulse generator 28 consisting of three pulse generators 281, 282, 283 to generate respective pulses for the three phases of the AC power. The pulse generator 28 supplies the generated pulses to the insulation resistors R _R , R _S , and R _T located in the secondary circuit 22 of the furnace transformer 25 of the electric furnace 21. ) Is connected. The pulse output unit 29 includes four diodes D1 to D4 arranged in line with the circuit protection fuse F connected to each pulse generator, and a resistor R and a capacitor C connected in parallel. Between the pulse generator 28 and the power supply 27 receives the necessary operating power from the power supply controller 271 of the power supply 27, each phase of the pulse generator 28 in accordance with the insulation detection selection by the inspector The operational amplifier 30 that receives the output current and amplifies and calculates the insulation state is connected. The operational amplifier 30 is turned on and off by the inspector to generate a test switch 311 for selecting insulation detection, an instrument panel 312 and an alarm for informing the inspector of the insulation state. The operation display unit 31 made of a buzzer 313 or the like is connected.

The operation of the AC furnace insulation detection device of the present invention configured as described above will be described in more detail with reference to FIGS. 3 to 4.

FIG. 3 (a) is a front view of the set showing the insulation detection device of FIG. 2, (b) is a rear view, and FIG. 4 is an equivalent circuit diagram of the insulation detection device of FIG.

First, power is supplied to the primary side of the furnace transformer 25 through the disconnector 23 and the vacuum circuit breaker 24. The furnace transformer 25 transfers the power applied to the primary side to the secondary side. Power transmitted to the secondary side of the furnace transformer 25 is supplied to the secondary side insulation resistance 22 and the electric furnace 21. On the other hand, the inspector attempts to detect the electrical insulation state of the electric furnace 21, the transformer 25, the secondary circuit 22 from time to time after the operation of the furnace 21 before or after the operation so that the equipment can operate in a safe state. When appropriate, the buttons having the functions mentioned in Table 1 on the insulation detection apparatus according to the disclosed design are properly operated.

TABLE 1

When the inspector intends to detect insulation, first, the test switch 311 on the operation display unit 31 is turned "ON". On the other hand, the power supply unit 27 supplies a predetermined input AC power supply to the operating power required for the insulation state detection in the pulse generator 28 and the operational amplifier 30. The power supply unit 27 supplies AC 220V / 440V input AC power to the silicon controlled rectifier 273 through the transformer 272. The silicon controlled rectifier 273 is turned on by the power supply controller 271 by rectifying the AC power transmitted to the anode A side through the transformer 272 to the DC power of DC0-220V required by the pulse generator 28. To the pulse generator 28 connected to the cathode K side. The power supply controller 271 of the power supply unit 27 converts the input AC power into DC 12V DC power required by the operational amplifier 30 and supplies it to the operational amplifier 30. The three pulse generators 281,282, and 283 constituting the pulse generator 28 generate predetermined pulses according to DC power of DC0-220V applied from the silicon controlled rectifier 273. The pulses generated by each pulse generator 281, 282, 283 generally have high voltage, high frequency pulse of 60-600 pulse and current limit of maximum 1A. The pulses output for each phase from the respective pulse generators 281, 282, and 283 are output to the secondary side insulation resistance 22 of the furnace transformer 25 through the pulse output unit 29. That is, the pulse output unit 29 is output to the insulation resistances R _R , R _S , R _T of the corresponding phases of the secondary circuit through four diodes arranged in a line through the circuit protection fuse F. FIG. Here, the diode serves to prevent the reverse voltage to protect the power supply 27, the pulse generator 28 and the operational amplifier 30 and the like. The resistor (R) and the capacitor (C) connected in parallel to the final output terminal of the pulse output unit 29 serves as a surge interruption. The three-phase high frequency high voltage pulses output from the pulse output unit 29 through the auxiliary relay 26 that is reversed "on" as the vacuum circuit breaker 24 is "off", the furnace transformer 25 It is applied to the insulation resistances R _R , R _S and R _{T of} each of the secondary phases. The current flows in each phase by the voltage pressed between the secondary insulation resistance 22 and the ground. The three-phase pulse generators 281, 282, 283 of the pulse generator 28 measure leakage currents of the three phases of the secondary resistance 22 of the furnace transformer 25, and apply the measured current component to the operational amplifier 30. . The operational amplifier 30 receives the leakage current of each phase measured by the three-phase pulse generators 281, 282, and 283 when the test switch 311 on the operation display unit 31 is "on", and amplifies the amplifier to a predetermined size. The leakage current amounts of the three phases detected by the meters (AR, AS, AT) 312 on the operation display unit 31 as shown in FIG. When the amount of leakage current exceeds the reference value, the operational amplifier 31 generates an alarm through the buzzer 313 on the operation display unit 31 to recognize the inspector that the insulation state is not good. As shown in FIG. 4, the vacuum circuit breaker 24 is provided on an equivalent circuit composed of the furnace resistance 25 such as the resistance resistance Z _T , the auxiliary transformer equivalent resistance Z _A , and the secondary circuit insulation resistance R. Is opened and the furnace transformer 25 is " off ", and when the test switch 311 is " on ", the pulse generator 28 generates a high voltage and high frequency pulse voltage (V _R , V _S ,). V _T ) is generated and pressurized to the secondary circuit of the furnace transformer 25. The pulse currents I _R , I _S , I _T flow through the respective phases R, S, and T by the pulse voltages V _R , V _S , V _T applied to the secondary circuit. At this time, when the secondary circuit insulation resistance (R _R , R _S , R _T ) is infinite, the current of each phase is detected as a normal value and transmitted to the operational amplifier unit 30. The operational amplifier unit 30 indicates that the insulation state is good when the current of each phase is detected as a normal value through the meter 312 on the operation display unit 31. However, when the secondary circuit insulation resistance (R _R , R _S , R _T ) is lowered and a leakage current is generated, the current of each phase increases. The operational amplifier unit 30 indicates that the insulation state is poor in the meter 312 of each phase when the current of each phase increases by more than a normal value. Then, the buzzer 313 is driven to generate an alarm.

As described above, the present invention relates to an AC furnace insulation detection device, which measures the leakage current of the electrical insulation resistance of the secondary circuit of the furnace transformer to check the insulation state from time to time to check the electrical insulation state of the secondary circuit of the furnace. It has an effect that can be monitored.

Claims (7)

An apparatus for detecting an electrical insulation state of a secondary transformer of a furnace transformer of an alternating current electric furnace, the apparatus comprising: a power supply for supplying an input alternating current power to a required operating power of each component; Pulse generation unit for generating pulses for three phases in accordance with the power supplied from the power supply unit, and measuring the leakage current flowing through the three-phase insulation resistance (R _R , R _S , R _T ) located on the secondary side of the furnace transformer ; A pulse output unit configured to press the pulse generated by the pulse generator to the three-phase insulation resistances R _R , R _S , and R _T ; An operational amplification unit configured to amplify the leakage currents for the three phases measured by the pulse generator in a predetermined size and to determine an insulation state by comparing with a reference value in an insulation detection selection state; And an operation display for selecting insulation detection and displaying a result of determining the insulation state of the operational amplifier. The power supply controller of claim 1, wherein the power supply unit comprises: a power supply controller configured to output an input AC power to a power corresponding to the operational power of the operational amplifier unit; A transformer for receiving the input AC power to the primary side and transferring the input AC power to the secondary side; And a silicon controlled rectifier having an anode connected to the secondary side of the transformer, the power being supplied to the anode to be turned on to adjust the voltage to the required pulse voltage of the pulse generator connected to the cathode. Detection device. The circuit of claim 1, wherein the pulse output unit comprises: a fuse for protecting a circuit; Diodes for preventing reverse voltage; And a resistor and a capacitor connected in parallel for surge protection. The auxiliary relay according to claim 1 or 3, wherein an auxiliary relay is connected between the secondary side of the furnace transformer and the pulse output unit when the furnace transformer is “OFF” to enable insulation detection. AC furnace insulation detection device, characterized in that the. The method of claim 1, wherein the operational amplifier compares the leakage current flowing through the three-phase insulation resistances R _R , R _S , and R _T measured by the pulse generator with a reference value, and determines that the insulation state is bad when the reference value is higher than the reference value. AC furnace insulation detection device, characterized in that. The AC furnace insulation detection apparatus according to claim 1, wherein the operation display unit includes a meter for displaying leakage currents for the three phases measured by the pulse generator as an indication of a guideline. 6. The AC furnace insulation detection apparatus according to claim 5, wherein the operation display unit comprises a buzzer for generating an alarm when it is determined that the insulation state is poor as a result of the determination of the operational amplifier.