JP2007323913A - Vacuum breaker fault detector for arc furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum breaker fault detector which can be easily mounted on a power supply circuit for an existing arc furnace to assuredly prevent electrical shock or any other accidents caused by faulty contact opening of a vacuum breaker. <P>SOLUTION: Voltage monitor meters 8a to 8c for detecting the voltage to ground for each phase are attached to secondary-side power feeding lines 5a to 5c of vacuum breakers 3a to 3c respectively mounted on a power supply circuit for an arc furnace 1. The voltage monitor meters determine whether the voltage to ground for each phase of the power feeding lines 5a to 5c in the event of opening of the vacuum breaker exceeds the fixed reference value, thereby detecting faulty contact opening of the vacuum breaker. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a detection device for detecting a contact opening failure of a vacuum circuit breaker and preventing an electric shock accident or the like in an arc furnace provided with a vacuum circuit breaker for opening and closing a power source.

  Generally, a vacuum circuit breaker is provided in the power circuit of the arc furnace to open and close the high voltage and large current. However, the vacuum circuit breaker breaks down during use and the electric circuit breaks down. There was a risk of electric shock during maintenance.

On the other hand, the vacuum failure detection device disclosed in Patent Document 1 below analyzes a discharge waveform detected at the time of a vacuum failure to determine a vacuum failure, but is an advanced calculator for analyzing and determining a discharge waveform. Was necessary.
Moreover, the vacuum failure detection device for a vacuum switch shown in the following Patent Document 2 determines a vacuum failure by determining a current change when the vacuum switch is shut off, but determines a current change, In order to compare the number of times, an advanced CPU is required.
In addition, the invention of the vacuum failure detection device disclosed in Patent Document 3 relates to a method for improving the sensitivity when a vacuum circuit breaker is inspected for a product, but a special connection is required for its implementation. There is a problem that it cannot be applied to the power distribution equipment of the existing arc furnace.
JP-A-6-12949 JP-A-5-128944 JP-A-10-12459

  Therefore, the invention of the arc furnace vacuum circuit breaker defect detection device according to the present invention can be easily installed in the existing arc furnace power supply circuit, and can reliably prevent electric shock accidents due to vacuum circuit breaker contact failure. It is intended to provide a device to obtain.

  For this purpose, the vacuum furnace circuit breaker defect detecting device according to claim 1 is a voltage for detecting the ground voltage of each phase on the secondary power supply line of the vacuum circuit breaker provided in the power circuit of the arc furnace. Provide a monitoring meter, and the voltage monitoring meter determines whether the ground voltage of each phase of the power supply line exceeds a certain reference value when the vacuum circuit breaker is opened. Is detected.

  According to the invention described in claim 1, since it can be additionally provided in the power circuit of the existing arc furnace, the installation is easy, and when the vacuum circuit breaker is opened, the ground voltage of each phase of the feeder line is By being monitored, it is possible to reliably prevent an electric shock accident due to poor contact opening of the vacuum circuit breaker.

  FIG. 1 is a power supply circuit diagram of an arc furnace showing an embodiment of the present invention. 1 is an arc furnace in which three electrodes 1a to 1c are suspended in the furnace, and 2a to 2c are each an electrode for raising and lowering each of the electrodes. Fig. 6 shows an electrode support device that allows the to be adjusted. In addition, 3a to 3c are vacuum circuit breakers provided to open and close the high-voltage current in the electric power circuit of the arc furnace, and a main transformer 4 is provided on the secondary side of the vacuum circuit breaker. Three-phase alternating current reduced from 22000 V to 1000 V is applied to the electrodes 1 a to 1 c through the feeder lines 5 a to 5 c, causing arc discharge between the electrodes, and melting the metal such as iron in the furnace by the heat generated at that time To do.

  6 is a transformer provided so as to be branched from the power supply lines 5a to 5c, and further reduces the voltage of the power supply line to 250V. The transformer is connected to the arc furnace 1 by the ground line 7 having a common primary side and secondary side. Wiring is conducted to the ground, and voltage monitoring meters 8a to 8c are provided for each phase on the secondary side of the transformer 6. The voltage monitoring meters 8a to 8c detect the ground voltages of the feeder lines 5a to 5c. To be.

  When the vacuum circuit breakers 3a to 3c are opened, the opening signal is transmitted to the alarm device 9 via the signal line 11, and the phases of the power supply lines 5a to 5c when the vacuum circuit breakers 3a to 3c are opened. Whether or not the ground voltage exceeds a certain reference value is determined by the voltage monitoring meters 8a to 8c. If the voltage monitoring meter exceeds the certain reference value, the vacuum circuit breakers 3a to 3c are activated by operating the alarm device 9. The contact opening failure is detected so that an electric shock accident does not occur.

  In addition, 10 is an electrode raising / lowering control apparatus, The secondary side of the transformer 6 is connected to this control apparatus, a control signal is transmitted to the said electrode support apparatuses 2a-2c from this control apparatus, and the support height of the electrodes 1a-1c , And the arc length is automatically adjusted.

The power circuit diagram of the arc furnace which shows embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Arc furnace 1a-1c Electrode 2a-2c Electrode support apparatus 3a-3c Vacuum circuit breaker 4 Main transformer 5a-5c Feeding line 6 Transformer 7 Ground line 8a-8c Voltage monitor 9 Alarm apparatus 10 Electrode raising / lowering control apparatus 11 Vacuum Breaker open signal line

Claims (1)

  A voltage monitor for detecting the ground voltage of each phase is provided on the secondary power supply line of the vacuum circuit breaker provided in the power circuit of the arc furnace, and the ground of each phase of the power supply line when the vacuum circuit breaker is opened An arc furnace vacuum circuit breaker failure detection device that detects a contact open failure of a vacuum circuit breaker by determining whether the voltage exceeds a certain reference value by the voltage monitor.

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