NL2033395B1

NL2033395B1 - Stray-Arc Monitoring System and Method

Info

Publication number: NL2033395B1
Application number: NL2033395A
Authority: NL
Inventors: Petrus Greyling Frederik; Greyling Ruan
Original assignee: Petrus Greyling Frederik; Greyling Ruan
Priority date: 2022-10-25
Filing date: 2022-10-25
Publication date: 2024-05-14
Also published as: EP4361292A1; EP4361292B1; EP4361292C0

Abstract

A monitoring system 10 comprises a thermal imaging device 50 mounted externally of the furnace 12. The device is mounted and configured to generate data relating to heat emitted in a predetermined zone of interest 46 externally of the furnace and which may 5 result in a stray-arc. A controller 52 comprising a processor 54 executing a program is connected to the imaging device 50 to receive the generated data. At least one of the imaging device 50 and the software is configured to focus on or mask in data from the zone of interest 46 only, and to mask out or discriminate against data from adjacent zones. The processor is configured to: process the generated data into temperature 10 data; compare the temperature data to predetermined threshold temperature data which is indicative of a stary-arc forming in the zone; and to generate an output when the temperature data reaches the threshold temperature data. Figure 1 15

Description

Stray-Arc Monitoring System and Method

INTRODUCTION AND BACKGROUND

This invention relates to a system and method for monitoring stray-arcs at electric arc furnaces, more particularly furnaces comprising two or more elongate electrodes extending through a roof of the furnace.

A stray-arc is an arc that typically starts off as a small leakage current that can develop into a small arc that then rapidly develops into a full-blown arc with extremely high energy that can cause substantial damage, destroy equipment and start fires.

JP20041566865A discloses a device and method for controlling operation of a plasma arc type melting furnace comprising a single elongate electrode extending through the roof of the furnace and a furnace bottom electrode. In these furnaces, a main arc is generated between the elongate electrode and a burden, which is at the same voltage as the furnace bottom electrode, to melt the burden. Stray-arcs may result in various unpredictable places on the interior of the furnace. For example, a stray-arc may develop from the elongate electrode via conductive deposits, where they may develop on an inner surface of a wall or roof of the furnace, to the bottom electrode or melt. An infrared camera on the outside of the furnace is used to monitor, through a transmission window in the wall of the furnace, the inside of the furnace for such stray- arcs on the inside of the furnace.

A problem with furnaces comprising at least two elongate electrodes extending from support structures above the furnace roof through the roof and into the furnace is that dust and other debris may accumulate on the roof and may result in a stray-arc between the electrodes on the outside of the furnace. This stray-arc would not be detectable by the device of JP20041566865A and this arc may also result in severe damage to the furnace and extended down-times. The same may happen in other zones of interest on the outside of the furnace, for example between bus bars. On the other hand, heat and or flames escaping upwardly through electrode seals between the electrode and the roof to beyond a top surface of the roof, are not considered a serious problem in the present context and need to be distinguished from undesirable possible stray-arcs on the outside of the furnace.

OBJECT OF THE INVENTION

Accordingly, it is an object of the present invention to provide a system and a method of monitoring stary-arcs with which the applicant believes the aforementioned disadvantages may at least be alleviated or which may provide a useful alternative for the known systems and methods.

SUMMARY OF THE INVENTION

According to the invention there is provided a stray-arc monitoring system for a furnace comprising a furnace shell defining a chamber on the inside of the shell, a roof and at least a first elongate electrode and a second elongate electrode extending from a support and electrical connection structure downwardly through openings in the roof into the chamber, the monitoring system comprising: - a thermal imaging device mounted externally of the furnace, the thermal imaging device being mounted and configured to generate data relating to heat emitted in a predetermined zone of interest externally of the furnace and which may result in a stray-arc externally of the furnace; - a controller comprising a processor executing an application specific program and which controller is connected to the imaging device to receive the generated data; - at least one of the imaging device and the software being configured to focus on or mask in the zone of interest; and - the processor being configured to: process the generated data into temperature data; compare the temperature data to predetermined threshold temperature data which is indicative of a stary-arc forming; and to generate an output when the temperature data reaches the threshold temperature data.

The temperature imaging device may be an infrared imager.

The output may be connected to interrupt power to at least one of the electrodes and/or to energize an alarm. The alarm may be any one or both of a visible and an audible alarm.

The invention also includes within its scope a method of monitoring potential stray-arcs externally of a furnace comprising a furnace shell defining a chamber on the inside of the shell, a roof and at least a first elongate electrode and a second elongate electrode extending from a support and electrical connection structure downwardly through openings in the roof into the chamber, the method comprising the steps of:

- defining at least one zone of interest externally the furnace, the zone being masked from adjacent zones which are not of interest; - generating data relating to heat being emitted from the zone; - processing the generated data into temperature data; - comparing the temperature data to threshold temperature data which is indicative of a potential stray-arc developing in the zone of interest; and - in the event of the temperature data reaching the threshold temperature data, taking preventative measures.

The preventative measures may be any one or both of switching off power to the electrodes and energizing an alarm.

BRIEF DESCRIPTION OF THE ACCOMPANYING DIAGRAMS

The invention will now further be described, by way of example only, with reference to the accompanying diagrams wherein: figure 1 is a block diagram of an example embodiment of a stray-arc monitoring system for a furnace; figure 2 is a diagrammatic side view of the furnace comprising at least first and second elongate electrodes; figure 3 is a diagrammatic plan view of the furnace in figure 2; figure 4 is a diagrammatic view of a furnace power supply connected by bus bars to the electrodes; figure 5 is a diagram of an example embodiment of a typical display of a user interface of the monitoring system; and figure 6 is a flow diagram of an example method of monitoring potential stray- arcs externally of a furnace.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

5 An example embodiment of a stray-arc monitoring system 10 for a furnace 12 is shown in figure 1 and will be describe further below.

The furnace 12 is shown in figures 2 to 4. The furnace 12 comprises a furnace shell 14 defining a chamber 16 on the inside of the shell and a roof 18. The roof typically comprises a water-cooled outer section 20 circumscribing a non-conducting refractory centre region 22. At least a first elongate electrode 24 and a second elongate electrode 26 extend from a support and electrical connection structure 28 (shown in figure 4) above the furnace downwardly through respective openings 30, 32 in the centre region 22 of roof 18 into the chamber. Electrode seals 34, 36 are provided between the inner section 22 and the electrodes 24 and 26, respectively. In other embodiments, the entire roof may be water-cooled.

As best shown in figure 4, the electrodes are suspended from a support and connection structure 28. The electrodes 24, 26 are connected to a furnace power supply 38 by bus bars 40 and 42, respectively.

Certain zones externally of the furnace 12 are critical from a perspective of development of potential stray arcs, which could cause severe damage to the furnace and other equipment in the vicinity of the furnace. Such zones comprise, but is not limited to, a zone 44 (shown in figure 4) between the bus bars 40 and 42 and a zone 48

(shown in figures 2 and 3) on an upper surface of inner section 22 of the roof between the electrodes 24 and 26, where dust and debris may accumulate and contribute to the formation of undesirable stray-arcs. This zone must be distinguished from other known adjacent or nearby regions 48 which are not considered problematic in the present context, for example, where heat and/or flames from time to time may escape, in known manner, upwardly past the electrode seals 34, 36, to beyond the top surface of the inner section 22 of roof 18.

Referring to figure 1, the example embodiment of the monitoring system 10 comprises a thermal imaging device 50 mounted externally of the furnace 12. The thermal imaging device is mounted and configured to generate data relating to heat emitted in the predetermined zone of interest 44 or 46 externally of the furnace and which may result in a stray-arc externally of the furnace. A controller 52 comprising a processor 54 executing an application specific program is connected to the imaging device 50 to receive the generated data. At least one of the imaging device 50 and the software is configured to focus on or mask in data from the zone of interest 44 or 46 only, and to mask out or discriminate against data from the adjacent zones, such as zones 48. The processor is configured to: process the generated data into temperature data; compare the temperature data to predetermined threshold temperature data which is indicative of a stary-arc forming in the zone; and to generate an output when the temperature data reaches the threshold temperature data.

The output 56 is connected in known manner to a plant controller 58 and the plant controller is connected, also in known manner, to control a furnace transformer circuit breaker 60 of power supply 38.

Referring to figures 1 and 5, for purposes of installation, there is provided a computer 62 having a GUI 64 (shown in figure 5) which is connected to the controller 52.

During installation, a human installer 66 would select and define (as shown at 68 in figure 1), via the computer 64, the zone of interest 44 or 46 to be covered by the imager 50. The installer would also set (as shown at 70 in figure 1) the predetermined threshold temperature value which would be indicative of a potential stray-arc developing in the zone.

Data relating to these selections is transmitted by the computer 62 to the controller 52.

In use, the thermal imager 50 continually generates data relating to heat generated in the zone of interest. The generated data is fed to the controller 52 and the processor 54, for processing into temperature data as described above. Referring to figure 5, the focus on or masking in of the zone 46 and discriminating against adjacent zone 48 may be achieved by the software processing temperature data from pixels in a thermal image generated by the device 50 corresponding to zone 46 as described above, and not those of or ignoring the pixels corresponding to zone 48.

In a case where the temperature data reaches the threshold temperature, the output signal 56 causes the plant controller 58 to transmit a signal to the circuit breaker 60, to interrupt power to the electrodes, thereby to prevent the potential stray-arc from forming or developing further in the zone of interest.

An associated method of monitoring for potential stray-arcs in at least one zone of interest externally of a furnace is shown in figure 6, which is self-explanatory.

It will be appreciated that the monitoring system monitors the defined zones of interest 44 or 46 only and masks out adjacent or even immediately adjacent zones 48 where temperatures may from time to time, for known reasons which are not considered dangerous in the current context, rise to elevated levels.

Claims

CONCLUSIONS

CLAIMS 1. A furnace stray arc monitoring system comprising a furnace shell defining a chamber inside the shell, a roof, and at least a first elongated electrode and a second elongated electrode extending downwardly from a support and electrical interconnect structure openings extending into the roof into the room, the monitoring system consisting of: - a thermal imaging device mounted outside the oven, the thermal imaging device being mounted and configured to generate data relating to heat radiated in a predetermined zone of interest outside the oven and which may result in a stray arc outside the oven; - a controller comprising a processor that executes an application-specific program and which controller is connected to the display device to receive the generated data; - at least one of the imaging device and software is configured to focus on or mask the region of interest; and - the processor is configured to: process the generated data into temperature data; compare the temperature data with predetermined threshold temperature data indicative of the formation of a stray arc; and to generate an output when the temperature data reaches the threshold temperature data.

2. The monitoring system of clause 1, wherein the temperature imaging device is an infrared imager.

3. The clause 1 or clause 2 monitoring system where the output is connected to interrupt the current to at least one of the electrodes and/or to activate an alarm.

4. A method of monitoring potential stray arcs outside a furnace, comprising a furnace dish defining a chamber inside the dish and a roof, and at least a first elongated electrode and a second elongated electrode extending from a support and electrical connecting structure downwards through openings in the roof into the room, the method comprising the steps of: - defining or causing to be defined at least one zone of interest outside the oven, masking the zone from adjacent zones not of be important; - generating thermal image data relating to heat emitted from the zone;

- processing the generated data into temperature data; - comparing the temperature data with threshold temperature data indicative of a potential stray arc developing in the zone of interest; and - if the temperature data reaches the threshold temperature data, taking preventive measures.

5. The method of clause 4 in which the preventive measures are one or both of turning off the current to the electrodes and activating an alarm.