Rectifying power supply system and monitoring and early warning system for direct-current submerged arc furnace

Abstract

The invention discloses a DC submerged arc furnace rectification power supply system, monitoring and early warning system. The system comprises a high-voltage wire inlet unit used for introducing high voltage of a high-voltage transformer substation; the rectifier transformer unit is used for inputting alternating current to the high voltage introduced by the high-voltage wire inlet unit through a high-voltage network side, adjusting the alternating current into voltage required by smelting through a rectifier transformer, and outputting the voltage through an alternating current flexible connection copper bar; the rectifier cabinet unit is used for receiving the alternating current output by the rectifier transformer unit, converting the alternating current into direct current, and switching positive and negative polarities of an electrode of the direct-current submerged arc furnace through a positive group thyristor and a negative group thyristor in turn at different moments; the secondary bus unit is used for transmitting the direct current output by the rectifier cabinet unit; the electrode unit is used for receiving the current which is received and output by the secondary bus unit and is required by smelting of the direct-current submerged arc furnace, heating the direct-current submerged arc furnace and realizing direct-current flowing-into-furnace adjustment of the submerged arc furnace; power supply early warning of the rectification system of the direct-current submerged arc furnace is realized.

Description

Technical Field

[0001] The present invention belongs to the field of monitoring and early warning, and relates to a DC ore-fired furnace rectification power supply system, a monitoring and early warning system. Background Art

[0002] Currently, DC smelting technology, in which both positive and negative electrodes are arranged perpendicular to the furnace, is increasingly being used in industry. While some related smelting technologies are still under development, this arrangement of DC submerged arc furnaces has already shown initial success on existing production lines, offering significant energy-saving and environmental advantages. Compared to AC submerged arc furnaces, it offers advantages such as high power factor, no skin effect, flexible power transmission, and high arc temperature. Compared to bottom-electrode DC submerged arc furnaces, it offers advantages such as high thermal efficiency, high powder utilization, low failure rate, and easy maintenance. Because there is no bottom electrode consumption, regular bottom electrode overhaul is not required, ensuring continuous smelting production.

[0003] During the smelting process of an industrial ferroalloy smelting DC submerged arc furnace in which both the positive and negative electrodes are arranged vertically in the furnace, the transmission current from the low-voltage side of the rectifier device to the smelting electrodes can reach up to 200kA or even greater, resulting in relatively large capacities for the rectifier transformer and rectifier cabinet. The rectifier transformer generally uses a voltage-regulating transformer (referred to as the regulator) with two main transformers (referred to as the main transformer). The three transformers are combined in a box to form a rectifier transformer. Because the two main transformers are symmetrically arranged in the box, monitoring and early warning of the various components of the rectifier device that power the submerged arc furnace electrodes are particularly important. This can also provide process operators with quantitative data to ensure the smooth progress of smelting production.

[0004] DC submerged arc furnaces are expensive and require extensive maintenance, resulting in significant economic losses from downtime and production interruptions. With the advancement of science and technology, equipment maintenance methods have also gradually evolved, from reactive maintenance to intelligent predictive maintenance, reducing production losses and equipment maintenance costs caused by unplanned downtime.

[0005] Therefore, we have developed a DC submerged arc furnace power supply monitoring system, which can be used to monitor and warn the power supply of each component of the DC submerged arc furnace rectifier device, thereby improving the overall intelligence level of the submerged arc furnace. Summary of the Invention

[0006] In order to solve the technical problem that the existing technology cannot accurately grasp the DC submerged arc furnace power supply system, the technical solution adopted by the present invention is: a DC submerged arc furnace rectification power supply system, comprising: High-voltage incoming line unit: used to introduce high voltage from the high-voltage substation; Rectifier transformer unit: used to input AC power from the high voltage grid side into the high voltage input unit, adjust the voltage to the voltage required for smelting through the rectifier transformer, and output the voltage through the AC flexible copper busbar; Rectifier cabinet unit: used to receive the AC power output by the rectifier transformer unit and convert it into DC power, adjust it to the voltage flow required for smelting, and use the positive group thyristors and the negative group thyristors in turn at different times to switch the positive and negative polarity of the DC submerged arc furnace electrodes; A secondary bus unit, used for transmitting the DC power output by the rectifier cabinet unit; Electrode unit: used to receive the current required for smelting of the DC submerged arc furnace output by the secondary bus unit and heat the DC submerged arc furnace.

[0007] Furthermore: the rectifier transformer unit adopts a double reverse star type in-phase anti-parallel structure; A bracket is provided under the rectifier cabinet unit for raising the rectifier cabinet unit; The neutral point of the low-voltage side of the rectifier transformer unit is connected to the lower part of the rectifier transformer body as far as possible, and the AC bus of the low-voltage side of the rectifier transformer unit is connected to the upper part of the rectifier transformer body and is directly connected to the elevated rectifier cabinet unit horizontally; The secondary busbar unit passes horizontally through the bracket set under the rectifier cabinet unit, and is connected to the contact elements attached to the electrode unit without passing through the busbar, ensuring that the length of the connecting copper bars and copper pipes of each part is the shortest, so as to ensure the lowest total loss during system operation.

[0008] Further: the rectifier transformer unit includes a rectifier transformer body; The rectifier transformer body includes a voltage regulating transformer, two phase-shifting rectifier transformers and an on-load tap-changing switch; A rectifier transformer box is provided outside the rectifier transformer body; A high-voltage bushing is provided on the upper part of the rectifier transformer box, and the internal conductor core of the high-voltage bushing is connected to the three phase lines of the high-voltage incoming line terminal of the voltage regulating transformer; A high-voltage neutral point is provided on the upper part of the rectifier transformer box. The internal conductor core of the high-voltage neutral point is connected to the neutral point line of the high-voltage incoming line terminal of the voltage-regulating transformer and is externally connected to a dedicated neutral point grounding device to achieve grounding protection for the rectifier transformer unit. A rectifier transformer low-voltage side AC output line bar is provided on the upper part of the side of the rectifier transformer box, which is connected to the valve side three-phase line of the main transformer inside the rectifier transformer; A rectifier transformer low-voltage side neutral point outlet bar is provided at the lower part of the side of the rectifier transformer box, and is connected to the valve side neutral point of the main transformer inside the rectifier transformer; An extended cross copper busbar is used inside the rectifier transformer body, with the four left terminals having the same polarity M and the four right terminals having the same polarity N. The outgoing copper busbar is led out from the lower part of the long side of the transformer box.

[0009] Furthermore: the rectifier cabinet main unit includes a main cabinet body, the main cabinet body is a magnetic-proof structure, and is made of high-quality cold-rolled steel plate as the main material and stainless steel with magnetic removal treatment; The support member is made of high-strength epoxy resin, which prevents the magnetic flux from forming a loop, thereby preventing local vibration and heating caused by the possible high current magnetic field; A fuse and a thyristor are arranged inside the main cabinet body; One side of the fuse is attached to the fuse busbar, and the other side of the fuse is attached to the single connecting bar; the top of the fuse busbar is connected to the AC flexible connecting copper bar; The fuse elements and fuse copper bars are arranged close to each other using in-phase anti-parallel copper bars, so that the magnetic fluxes in opposite directions cancel each other out. One side of the thyristor is attached to the positive group thyristor bus bar or the negative group thyristor bus bar, and the other side of the thyristor is attached to a single connecting bar; The positive polarity rows and negative polarity rows of the positive group thyristor busbars are alternately arranged in the depth direction, the positive polarity rows are connected to the negative ends of the positive group thyristors, and the negative polarity rows are connected to the positive ends of the positive group thyristors. The upper or lower end of the positive group thyristor bus is connected to the negative group thyristor bus, the lower end of the positive polarity bus is connected to the DC output bus M, and the lower end of the negative polarity bus is connected to the DC output bus N, and fixed with anti-magnetic stainless steel bolts; The negative polarity rows and the positive polarity rows of the reversed thyristor busbars are alternately arranged in the depth direction, the negative polarity rows are connected to the negative ends of the reversed thyristors, and the positive polarity rows are connected to the positive ends of the reversed thyristors.

[0010] Furthermore: it also includes a rectifier trolley body, the fuses, thyristors, fuse busbars, single-branch connecting bars, positive-group thyristor busbars, and negative-group thyristor busbars are all fixed on the rectifier trolley body, and the fuses, thyristors, fuse busbars, single-branch connecting bars, positive-group thyristor busbars, and negative-group thyristor busbars are fixed to the rectifier trolley body using insulating elements and antimagnetic stainless steel bolts to form an integrated structural component that can be disassembled as a whole during maintenance; A plurality of wheels are provided on the bottom bracket of the rectifier element trolley body for carrying the rectifier element as a whole after disassembly.

[0011] Furthermore, the process of switching the positive and negative polarities of the DC ore-fired furnace electrodes by taking turns using the positive group thyristors and the negative group thyristors at different times is as follows: When the positive group thyristors are put into use, the output of the positive group thyristor bus and the DC output bus M is positive polarity, and the output of the negative group thyristor bus and the DC output bus N is negative polarity; When the reverse group of thyristors is put into use, the output of the positive group of thyristor busbars and the DC output busbar M is negative polarity, and the output of the reverse group of thyristor busbars and the DC output busbar N is positive polarity; The positive group thyristors and the reverse group thyristors are not put into use at the same time to ensure that under any circumstances when the positive group thyristors work in parallel, the reverse group thyristors are in a blocked state; similarly, when the reverse group thyristors work, the positive group thyristors are in a blocked state, and a reverse current is obtained on the electrode. The positive and negative polarity switching of the electrode is realized by switching the output of the positive and reverse groups.

[0012] A monitoring and early warning system for a DC ore-bearing furnace rectification power supply system, comprising: Pressure gauge, used to collect the pressure at the cooling pure water inlet inside the rectifier cabinet unit; Thermometer: used to collect the temperature of the cooling pure water outlet inside the rectifier cabinet unit; Multiple temperature measurement modules: used to collect the temperature of multiple bridge arm busbars in the rectifier cabinet unit; Insulation monitoring device: used to monitor insulation damage on the AC side and DC side of the main circuit in the rectifier cabinet unit; DC high current measuring instrument: used to measure the current of the neutral point outgoing line of each rectifier transformer low voltage side; The first current transformer is used to detect the actual current on the primary side of the rectifier transformer unit; The second current transformer is used to detect the actual current on the secondary side of the rectifier transformer unit; The third current transformer is used to detect the actual values ​​of the eight DC high currents on the neutral point outgoing line bar on the low-voltage side of the rectifier transformer; Central control room host computer: receives the pressure gauge, temperature gauge, multiple temperature measurement modules, insulation monitoring device, DC high current measuring instrument, first current transformer, second current transformer and third current transformer transmitted through the DCS control system and the judged alarm signals, realizing information interaction with process operators.

[0013] The alarm signals of the first current transformer, the second current transformer, and the third current transformer are used to perform differential protection on the rectifier system through three-position differential joint protection. That is, current transformers are installed at three locations: the primary side of the modulation transformer, the primary side of the main transformer, and the low-voltage side of the rectifier transformer to perform current differential protection at three locations. The specific process is as follows: The nameplate ratings of the modulated primary current, modulated secondary current, and DC current at different switch positions are marked as I TBi , I ZBi , I di , where i=1, 2…31, the 20th gear is the rated gear of the rectifier system; S201. Calculate the proportional coefficient rating K between the modulated primary current and the modulated secondary current. i1 =I ZBi / I TBi , K i2 =I di / I ZBi , K i3 =I di / I TBi ; S202, calculate the actual value of the proportional coefficient between the modulated primary current and the modulated secondary current K1=I ZBA / I TBA , K2=I dA / I ZBA , K3=I dA / I TBA ; where i = 1, 2…31; S203, based on the rated value of the proportional coefficient between the modulated primary current and the modulated secondary current and the actual value of the proportional coefficient between the modulated primary current and the modulated secondary current, calculate the three-digit operation difference degrees respectively: = (K1-K i1 ) / K i1 , = (K2-K i2 ) / K i2 , = (K3-K i3 ) / K i3 S204: Calculate the comprehensive difference based on the three-digit operation difference ; S205, make early warning judgment, when the difference comprehensive difference degree When the temperature is higher than 1.5%, an early warning signal will be output. >2.5% when outputting alarm signal; At the same time, the imbalance monitoring method is used to carry out early warning monitoring of the rectifier system. Specifically, the actual values ​​of the 8 DC large currents on the neutral point output line of the rectifier transformer low voltage side are marked as I dNi , S301, calculate the average value of neutral point current I dNav = (I dN1 +I dN2 +…+ I dN8 ) / 8 S302. Calculate the unbalance degree of each neutral point current difference based on the average value of the neutral point current: ζ1= (I dN1 -I dNav) / I dNav ,ζ2= (IdN2 -I dNav ) / I dNav ,…,ζ8= (I dN8 -I dNav ) / I dNav S303. Calculate the comprehensive difference imbalance ζ based on the current difference imbalance of each neutral point:

[0014] S304. Based on the comprehensive difference imbalance, a warning judgment is made. When the comprehensive difference imbalance ζ is greater than 1%, a warning signal is output; when ζ is greater than 2%, an alarm signal is output.

[0015] The present invention provides a DC ore-bearing furnace rectification power supply system, monitoring, and early warning system, particularly a DC ore-bearing furnace rectification power supply monitoring system. This system can be used to monitor the power supply to each component of the ore-bearing furnace rectification device, implement three-position differential combined protection, and provide early warning of equipment operation imbalance. The proposed DC ore-bearing furnace rectification power supply monitoring system provides early warning of the power supply to each component of the DC ore-bearing furnace rectification device, providing reliable and effective data support for DC ore-bearing furnace production. It has the following advantages: Realize the DC current input regulation of the ore-fired furnace; Achieve power supply early warning for the DC submerged arc furnace rectifier system, improve efficiency, reduce costs, and ensure safe and continuous production; Avoid "excessive maintenance", while reducing maintenance time and reducing labor intensity; The application of rectifier power supply and its early warning technology enhances our company's technical reserves for intelligent practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0017] Figure 1 This is a schematic diagram of the DC ore-fired furnace rectification power supply system I; Figure 2 This is the schematic diagram II of the DC ore-fired furnace rectification power supply system; Figure 3 This is a schematic diagram of the rectifier cabinet body; Figure 4 This is the working flow diagram of three-position differential combined protection; Figure 5 This is the neutral point imbalance work flow chart.

[0018] Figure 1: 101, incoming cable, 102, cable terminal, 103, copper busbar, 104, resistance-capacitance absorption device, 105, cross arm, 106, support insulator, 107, steel column, 108, line card, 109, jumper, 110, rectifier transformer body, 111, high-voltage bushing, 112, high-voltage neutral point, 113, oil storage cabinet, 114, current transformer terminal box, 115, signal terminal box, 116, oil outlet pipeline, 117, oil inlet pipeline, 118, rectifier transformer low-voltage side AC outlet line bar, 119, rectifier transformer low-voltage side neutral point outlet line bar, 120, AC soft connection copper busbar, 121, rectifier cabinet body, 122, rectifier cabinet body, 123, rectifier cabinet body, 124, rectifier transformer body, 125, rectifier transformer body, 126, rectifier transformer body, 127, rectifier transformer body, 128, rectifier transformer body, 129, rectifier transformer body, 130, rectifier transformer body, 131, rectifier transformer body, 132, rectifier transformer body, 133, rectifier transformer body, 134, rectifier transformer body, 135, rectifier transformer body, 136, rectifier transformer body, 137, rectifier transformer body, 138, rectifier transformer body, 139, rectifier transformer body, 140, rectifier transformer body, 141, rectifier transformer body, 142, rectifier transformer body, 143, rectifier transformer body, 144, rectifier transformer body, 145, rectifier transformer body, 146, rectifier transformer body, 147, rectifier transformer body, 2. Fuse, 123. Thyristor, 124. Fuse busbar, 125. Single connecting bar, 126. Positive group thyristor busbar, 127. Reverse group thyristor busbar, 128. Rectifier element trolley, 129. DC output busbar M, 130. DC output busbar N, 131. Water inlet pipe, 132. Water outlet pipe, 133. Maintenance platform, 134. Cabinet bracket, 135. Neutral point connecting copper plate, 136. Rectifier cabinet outgoing line connecting copper plate, 137. Water-cooled hard copper tube, 138. Insulation bracket, 139. Water-cooled flexible copper tube, 140. Electrode body, 141. Electrode water-cooling copper tube, 142. Contact element. DETAILED DESCRIPTION

[0019] It should be noted that, unless there is any conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] The DC ore-fired furnace rectifier power supply system consists of a high-voltage incoming line unit, a rectifier transformer unit, a rectifier cabinet unit, a secondary bus unit, and an electrode unit. High-voltage incoming line unit: used to introduce high voltage from the high-voltage substation; Rectifier transformer unit: used to input AC power from the high voltage grid side into the high voltage input unit, adjust the voltage to the voltage required for smelting through the rectifier transformer, and output the voltage through the AC flexible copper busbar; Rectifier cabinet unit: used to receive the AC power output by the rectifier transformer unit and convert it into DC power, adjust it to the voltage flow required for smelting, and use the positive group thyristors and the negative group thyristors in turn at different times to switch the positive and negative polarity of the DC submerged arc furnace electrodes; A secondary bus unit, used for transmitting the DC power output by the rectifier cabinet unit; Electrode unit: used to receive the current required for smelting of the DC submerged arc furnace output by the secondary bus unit and heat the DC submerged arc furnace.

[0022] The rectifier power supply system adopts a double reverse star type in-phase anti-parallel structure A bracket is provided under the rectifier cabinet unit for raising the rectifier cabinet unit. The neutral point of the low-voltage side of the rectifier transformer unit is connected to the lower part of the rectifier transformer body and as low as possible. The AC bus of the low-voltage side of the rectifier transformer unit is connected to the upper part of the rectifier transformer body and is directly connected to the raised rectifier cabinet unit horizontally. The secondary busbar unit passes horizontally through the bracket set under the rectifier cabinet unit, and is connected to the contact elements attached to the electrode unit without passing through the busbar, ensuring that the length of the connecting copper bars and copper pipes of each part is as short as possible to ensure the lowest total loss during system operation.

[0023] Both forward and reverse thyristor groups are installed in the rectifier cabinet unit to achieve the switching of the positive and negative polarity of the electrodes. AC power is input from the high-voltage grid side of the rectifier transformer and adjusted to the voltage required for smelting by the rectifier transformer. The valve side and neutral point of the rectifier transformer are connected to the rectifier cabinet, and the rectifier cabinet outputs two sets of positive and negative copper busbars. Each set of copper busbars and the neutral point of the rectifier transformer are connected to the positive and negative electrodes through water-cooled hard copper tubes, water-cooled flexible copper tubes, and contact elements. Each rectifier transformer and the subsequent rectifier cabinet, secondary busbar, and positive and negative electrodes form a power supply system, and each power supply system is independently powered. Each DC ore-fired furnace is equipped with at least one power supply system. When two or more power supply systems are installed, the positive and negative electrodes are arranged alternately in the furnace.

[0024] like Figure 1 and Figure 2As shown in the figure, the high-voltage incoming line unit is composed of an incoming line cable 101, a cable terminal 102, a copper busbar 103, a resistance-capacitance absorption device 104, a crossbeam 105, a support insulator 106, a steel column 107, a jumper card 108, etc.; the rectifier transformer unit is composed of a rectifier transformer body 110, a high-voltage bushing 111, a high-voltage neutral point 112, an oil conservator 113, a current transformer terminal box 114, a signal terminal box 115, an oil outlet pipeline 116, an oil inlet pipeline 117, and an AC outlet on the low-voltage side of the rectifier transformer. The rectifier cabinet unit is composed of a rectifier cabinet body 121, fuses 122, thyristors 123, fuse busbars 124, single-branch connecting bars 125, positive thyristor busbars 126, negative thyristor busbars 127, rectifier component trolleys 128, DC output busbars M129 and N130, water inlet pipes 131 and 132, maintenance platforms 133, and cabinet supports 134. The secondary busbar unit is composed of a water-cooled hard copper tube 137, an insulating bracket 138, a water-cooled flexible copper tube 139, etc. The electrode unit consists of an electrode body 140, an electrode water-cooling copper tube 141, a contact element 142, etc. The high voltage incoming line unit is connected to the rectifier transformer unit via a jumper 109. The rectifier transformer unit is connected to the rectifier cabinet unit through the AC soft connection copper bus 120, the rectifier transformer unit is connected to the secondary bus unit through the neutral point connection copper plate 135, the rectifier cabinet unit is connected to the secondary bus unit through the rectifier cabinet outlet connection copper plate 136, and the end of the water-cooled flexible copper tube 139 of the secondary bus unit is connected to the end of the electrode water-cooling copper tube 141 of the electrode unit.

[0025] Incoming cable 101: A high-voltage cable introduced from a high-voltage substation outside the factory. It is introduced individually, with a total of three cables for each rectifier transformer. The voltage level is mostly 110kV, sometimes 35kV.

[0026] Cable terminal 102: Connected at the end of the incoming cable 101 to ensure the normal introduction of high voltage power supply.

[0027] Copper busbar 103: A copper conductor connected to the head of the cable terminal 102, the upper part of the RC absorber 104, and the upper part of the support insulator 106, with a jumper card 108 set at the end.

[0028] RC absorption device 104: fixed on the cross arm 105, with the upper end connected to the copper busbar 103; used to absorb the impact of high voltage closing moment, protecting the rectifier transformer and subsequent units.

[0029] Cross arm beam 105 : connected to the bottom of the RC absorber 104 and the support insulator 106 , provides support force, and is also used to fix the incoming cable 101 .

[0030] Support insulator 106: The bottom is fixed on the cross arm beam 105, and the top is connected to the middle part of the copper busbar 103 to provide support for it, while also providing insulation capability for high voltage to the ground.

[0031] Steel column 107: The top is welded to the middle of the crossbeam 105, and the bottom is fixed to the ground, providing height for the components in the high-voltage incoming line unit so that the high-voltage electricity can be normally connected to the rectifier system.

[0032] Jumper card 108 : provided at the end of the copper busbar 103 and the top of the high-voltage bushing 111 .

[0033] Jumper 109: It is set between the two jumper cards 108 and connects the high-voltage incoming line unit and the rectifier transformer unit.

[0034] Rectifier transformer 110: Utilizing a "main transformer and regulator integrated" design, each rectifier transformer's oil tank houses a voltage-regulating transformer (regulator), two phase-shifting rectifier transformers (main transformer), and a 31-level on-load tap changer. Wiring is for modulation without phase shifting, ensuring the operating current of the on-load tap changer is controlled within the rated current range with ample safety margin. The regulator features a 9.5kV compensating winding. Three sets of current transformers are installed per phase near the neutral point on the primary side of the regulator for metering, measurement, and protection. A single current transformer is installed in the neutral point circuit for comprehensive protection against three-phase unbalanced current. The main transformer's primary side utilizes a zigzag star phase-shifting configuration, while the secondary adopts a double reverse star configuration. Both windings and outputs utilize a common-phase anti-parallel connection to balance the valve-side lead reactance and improve the power factor. Each main transformer's primary side utilizes two sets of current transformers per phase near the neutral point for measurement and protection. The winding current density is less than 3.5A / mm²; the valve-side / neutral-point terminal current density is less than 1.5A / mm². The transformer core is made of Baowu Group's 27Q110 high-permeability cold-rolled grained silicon steel sheet. The transformer flux density is less than 1.6T for the modulation transformer and less than 1.65T for the main transformer. This ensures that the core is not over-magnetized even when the grid voltage fluctuates by +5%, and that the rated voltage is maintained even when the grid voltage fluctuates by -5%. The core structure is a flat-plate structure with no punching holes and 45° fully beveled joints, secured with imported TENAX polyester tape. The core clamps are strong and well-insulated. The core and fuel tank utilize a dual-positioning mechanism, ensuring that the transformer will not shift due to vibration during transportation or operation. The core is reliably grounded to the fuel tank via the clamps, with a clear grounding coil marking the grounding point. The coil structure utilizes a tightly wound construction, with insulation added where the conductors are transposed. Several wire segments at the coil ends are horizontally tied to enhance coil strength. The spacers on the transformer coils are made of high-strength cardboard with chamfered corners. The coils utilize a state-of-the-art kerosene vapor-phase drying process, ensuring consistent reactance and even ampere-turn distribution across all coils. During assembly, hydraulic jacks are used to compress the coils, ensuring the specified clamping force is achieved. The low-voltage and voltage-regulating coils utilize internal and external bracing and are securely tied with heat-shrink tape. The bracing and spacers are arranged vertically and evenly, and auxiliary bracing is added to ensure coil stability and improve short-circuit resistance. The main insulation utilizes a molded cardboard tube structure for enhanced mechanical strength. The ends utilize molded hard angle rings to enhance insulation strength and prevent overvoltage at the ends. Shielding measures are implemented at all high-voltage lead joints to reduce partial discharge. The high-voltage leads are externally insulated, and all winding leads are secured with sufficiently strong wire clamps.The main oil tank of the transformer adopts a core-free structure, a streamlined structure, and a microcomputer gray color; the mechanical strength of the oil tank is that all accessories can withstand the mechanical strength test of 133Pa vacuum pressure and 98kPa positive pressure, and the oil tank has no damage and permanent deformation exceeding twice the thickness of the tank wall; the sealing degree of the transformer oil tank can withstand a 50kPa oil pressure leakage test, and there is no leakage for 36 hours. The secondary outlet terminals adopt an epoxy resin casting structure and a magnetic isolation double pressure plate to ensure that there is no leakage at the outlet terminals; the sealing gasket is made of nitrile rubber gasket, which is resistant to oil temperature, oil, and oxidation, and ensures that there is no leakage at the sealing surface of the transformer; a fixed ladder is welded on the oil tank, and its position is convenient for taking gas samples and observing gas relays. A sufficiently large oil drain valve is provided at the bottom of the transformer oil tank; a manhole is set near the load switch of the transformer oil tank for easy installation and maintenance. To reduce additional losses in the oil tank, magnetic shielding is installed at the winding ends and outlets, along the tank walls, at all points where leakage magnetic fields are concentrated. The valve-side outlet frame is integrally formed from 20Mn23Al antimagnetic steel sheet to eliminate additional losses caused by eddy currents. To facilitate gas collection within the gas relay, the oil pipe from the transformer top cover to the oil conservator is set at a 1.5% elevation gradient from the horizontal surface. The transformer foundation is designed to be horizontal, and the structure meets the requirement for a 15° allowable inclination. The voltage regulator is an M-type on-load tap-changer with 31 levels of on-load tap changer, equipped with a ZD motor mechanism, remote control, position display, reliable overload protection, and BCD code position signal output contacts. The switch has a mechanical life of at least 800,000 cycles and an electrical life of at least 200,000 cycles.

[0035] High-voltage bushing 111: A jumper clip 108 is installed at the top, and the bottom is fixed to the upper part of the rectifier transformer box. The internal conductor core is connected to the three phase wires at the high-voltage input terminal of the voltage-regulating transformer. The high-voltage side is connected through the top. The bushing is a 126kV outdoor type with three-level anti-fouling reinforced type.

[0036] High-voltage neutral point 112: The bottom is fixed on the upper part of the rectifier transformer box, the internal conductor core is connected to the neutral point line of the high-voltage incoming line terminal of the voltage-regulating transformer, and is connected to a dedicated neutral point grounding device on the outside to achieve grounding protection for the rectifier transformer unit.

[0037] Oil conservator 113: Secured to the upper portion of the rectifier transformer housing via a bracket, it ensures that the interior of the rectifier transformer housing is filled with transformer-specific oil. A fully sealed capsule-type oil conservator is used, with a capacity that prevents oil overflow under full load at ambient temperatures up to 40°C. The conservator also maintains sufficient oil at -15°C when not in operation. The conservator capacity is no less than 10% of the transformer's total oil capacity, and a magnetic needle oil level gauge is installed at the end. The conservator is equipped with a drain device for filling and draining oil, as well as a desiccant with an oil seal. The desiccant and the oil inlet and outlet pipes are positioned as close to the main housing edge as possible, ensuring easy maintenance.

[0038] Current transformer terminal box 114: fixed on the upper side of the rectifier transformer box, all current transformer cables inside the transformer are introduced into this terminal box.

[0039] Signal terminal box 115: fixed in the middle of the side of the rectifier transformer box, it leads the output contacts of the oil temperature controller, main body gas relay, load tap gas relay, pressure relief valve, oil level signal, etc. to the transformer terminal box. The terminals are arranged neatly to facilitate secondary wiring.

[0040] The oil outlet pipe 116 is provided at the lower side of the rectifier transformer box body, connected to the oil inlet of the external oil-water cooling unit, and provides an interface for cooling the oil inside the box body.

[0041] Oil inlet pipe 117: It is set at the lower part of the side of the rectifier transformer box, connected to the oil outlet of the external oil-water cooling unit, and provides an interface for cooling the oil inside the box.

[0042] Rectifier transformer low-voltage side AC output busbar 118: Located on the upper side of the rectifier transformer housing, it connects to the valve-side three-phase lines of the main transformer inside the rectifier transformer. Twenty-four AC output copper busbars extend from the upper long side of the transformer, 12 per side.

[0043] Neutral point busbar 119 on the low-voltage side of the rectifier transformer: Located at the lower side of the rectifier transformer housing, it connects to the valve-side neutral point of the main transformer inside the rectifier transformer. An extended cross-copper busbar is used inside the rectifier transformer, with the four left terminals connected to the same polarity (M) and the four left and right terminals connected to the same polarity (N). This busbar extends from the lower long side of the transformer.

[0044] AC flexible copper busbar 120: Connects the AC outgoing busbar 118 on the low-voltage side of the rectifier transformer to the fuse busbar 124 of the rectifier cabinet unit and is secured with stainless steel bolts. The cross-sectional area is selected to ensure a dielectric density of ≤1.0. The hard portion of the cabinet transformer connection bar is nickel- or tin-plated. Molecular diffusion welding is used for the flexible and hard connections to ensure smooth welds.

[0045] The rectifier panel main body 121 includes fuses 122, thyristors 123, busbars, and a cabinet. The main cabinet body features a magnetic-proof construction, constructed primarily of high-quality cold-rolled steel with stainless steel treated for magnetic demagnetization. Support components are constructed of high-strength epoxy resin, preventing magnetic flux from looping and localized vibration and heating caused by potentially high-current magnetic fields. All components within the rectifier panel are shockproof, effectively reducing equipment noise, extending equipment life, and improving equipment stability. During stable operation, the noise level is ≤ 60 dB (above 1 meter). The water-cooling copper busbars within the panel utilize double-holes, with the contact surfaces planed and polished using a lathe to ensure level contact and reduce contact resistance. This improves current sharing among components in the same arm and reduces losses in fuses 122 and thyristors 123. The main rectifier panel is maintenance-free, with RC and overvoltage absorbers installed nearby to avoid magnetic field interference and improve absorption efficiency. The AC side uses high-energy zinc oxide varistors in a delta connection for operational overvoltage protection, and a resistor-capacitor star connection to suppress electrostatically induced overvoltage. Commutation overvoltage protection consists of a capacitor and resistor connected in parallel across the components to absorb overvoltage generated by commutation and protect their safe operation. The main water pipe and fittings are made of plastic-steel PPR, while branch water pipes use TOYOX transparent pipe imported from Japan, and the fittings are made of 304 stainless steel, ensuring the overall water system is resistant to pressure, cold, and corrosion. The rectifier cabinet is equipped with maintenance lighting. The supports and inter-arm insulation plates for the conductive busbars in the main cabinet are made of high-strength epoxy resin insulation boards, sprayed with flame-retardant insulating varnish. Components are required to withstand surge voltages at least 3.5 times the AC side voltage. The main rectifier circuit must withstand a voltage of at least 3kV to ground, and the main rectifier circuit must withstand a voltage of at least 3kV to any unconnected auxiliary circuits. The rectifier cabinet's controller utilizes a fully digital DSP-based control core, with a single output 12-pulse triggering and regulation system. The main and individual boards operate in hot standby mode. In the event of a failure on the active control board, operation switches seamlessly to the backup board, with minimal output current fluctuations during the switchover process. Overvoltage protection is implemented within the cabinet: zinc oxide varistor protection and RC overvoltage absorption are installed on the AC input side; DC RC absorption and varistor protection are installed on the DC output side of the rectifier bridge. RC devices are used to bypass overvoltages generated by switching and disconnection of bridge arm components.

[0046] Fuse 122: One side is attached to fuse busbar 124, and the other side is attached to single-branch connection bar 125, secured with antimagnetic stainless steel bolts. It uses a fast-acting component with a breaking capacity of 200kA (RMS), a water-cooled heat sink, and is cooled with purified water.

[0047] Thyristor 123: One side is attached to the positive thyristor bus 126 or the negative thyristor bus 127, and the other side is attached to the single connecting bar 125, secured with antimagnetic stainless steel bolts. Low-loss, high-power single thyristors are press-fitted to a water-cooled heat sink and cooled with purified water. The component current margin is set to ≥3.5 to ensure optimal component performance. When selecting components for the same bridge arm, select a group with the closest performance parameters, such as threshold voltage (UTO), forward voltage drop (UF), operating junction temperature (TJM), and reverse recovery time (Trr). This ensures that the forward voltage drop difference between all components under full load is no more than 0.04V. Component press-fitting utilizes the elastic single-pressing method used in electric locomotives. This method provides uniform pressing force, reduces contact resistance, and effectively improves current distribution and stability among components in the same arm. The press-fit structure incorporates multiple insulation layers for easy maintenance. The integrated water-cooled radiator ensures excellent contact with the components, uniform pressure across the surface, and seamless welds, effectively preventing galvanic corrosion and water leakage caused by dissimilar materials and extending service life. The neatly arranged components within the main cabinet, with a compact structure, facilitates current sharing among the components and reduces the distance between conductive traces within the cabinet, improving overall efficiency. The rectifier current sharing coefficient is ≥0.9, and the overall efficiency is ≥0.99.

[0048] Fuse busbar 124 is attached to the front of fuse 122 and connected to the AC flexible copper busbar 120 at its top, secured with antimagnetic stainless steel bolts. Each busbar has a vertical hole running the entire length of the busbar and water taps at both ends. During operation, the busbar is connected to the circulating cooling water supply for cooling the busbar and fuses. This busbar is arranged in the same-phase, anti-parallel configuration and exits from the long side of the transformer. The water-cooled busbars utilize dual-hole cooling, with a current density of ≤3.5A / mm², strictly controlling heat generation and minimizing losses. All copper busbars within the rectifier cabinet are nickel-plated for enhanced wear and oxidation resistance and reduced contact resistance. The fuse elements and fuse busbars are arranged in close proximity using the same-phase, anti-parallel configuration. The opposing magnetic fluxes cancel each other out, minimizing magnetic leakage and eddy current losses.

[0049] Single connecting bar 125: Attached to the back of fuse 122, to the positive or negative side of the positive thyristor group, and to the negative or positive side of the negative thyristor group. The positive and negative thyristors are arranged in tandem on the same bar and secured with antimagnetic stainless steel bolts. The water-cooled copper busbar utilizes a double-hole water bag, which is attached to the thyristors, and the water bag lead bar is attached to the fuse. The current density of the component copper busbar is ≤3.0A / mm². The contact surface of the connecting copper busbar is CNC-machined to a surface finish better than Ra1.6 to reduce contact resistance.

[0050] Positive thyristor busbars 126: Positive and negative busbars are arranged alternately in the depth direction. The positive busbars are attached to the negative ends of the positive thyristors, while the negative busbars are attached to the positive ends of the positive thyristors. They are connected to the negative thyristor busbars 127 at either the top or bottom. The bottom ends of the positive busbars are connected to the DC output busbar M129, while the bottom ends of the negative busbars are connected to the DC output busbar N130. They are secured with antimagnetic stainless steel bolts. Each busbar has a vertical hole running through its length, and water nozzles are installed at both ends. During equipment operation, circulating cooling water is connected to the internal cooling system to cool the busbars and the positive thyristors. The water-cooled busbars use dual-hole cooling, and the current density of the busbars is ≤3.5A / mm², strictly controlling heat generation and reducing losses.

[0051] Reverse thyristor busbars 127: Negative and positive busbars are arranged alternately in the depth direction. The negative busbars are attached to the negative ends of the reverse thyristors, while the positive busbars are attached to the positive ends. They are connected to the positive thyristor busbars 126 at either the top or bottom and secured with antimagnetic stainless steel bolts. Each busbar has a vertical hole running through its length, and water nozzles are located at both ends. During operation, circulating cooling water is connected to the busbars and reverse thyristors. The water-cooled busbars utilize dual-hole cooling, with a current density of ≤3.5A / mm². This strictly controls heat generation and reduces losses.

[0052] Rectifier component trolley 128: fuse 122, thyristor 123, fuse bus 124, single connecting bar 125, positive group thyristor bus 126, and negative group thyristor bus 127 are all fixed on the trolley, fixed with insulating elements and anti-magnetic stainless steel bolts, and made into an integrated structural component, which can be disassembled as a whole during maintenance. The bottom bracket of the trolley is provided with multiple wheels to facilitate the overall transportation after disassembly; after being installed in the rectifier cabinet, it is fixed to the shell with anti-magnetic stainless steel bolts.

[0053] DC output busbar M129: Connects to the positive polarity busbar of the positive thyristor busbar 126 and connects to the secondary busbar unit through the rectifier cabinet's outgoing copper plate 136. Inside the rectifier cabinet, use a water-cooled copper busbar to route the M-polarity busbar to the left side of the cabinet. The water-cooled busbar uses dual-hole water cooling, and the current density of the busbar is ≤3.5A / mm², strictly controlling heat generation and minimizing losses.

[0054] DC output busbar N130: Connects to the negative polarity of the positive group thyristor busbar 126, and is connected to the secondary busbar unit through the rectifier cabinet outlet copper plate 136. When the positive group thyristors are put into use, the output of the positive group thyristor busbar 126 and the DC output busbar M129 is positive, and the output of the reverse group thyristor busbar 127 and the DC output busbar N130 is negative; when the reverse group thyristors are put into use, the output of the positive group thyristor busbar 126 and the DC output busbar M129 is negative, and the output of the reverse group thyristor busbar 127 and the DC output busbar N130 is positive; Figure 3 As shown, the positive and negative thyristors are not operated simultaneously. A logical control method ensures that when the positive thyristors are operating in parallel, the negative thyristors are always blocked. Similarly, when the negative thyristors are operating, the positive thyristors are blocked, resulting in a reverse current flowing through the electrodes. This switching of the positive and negative polarity of the electrodes is achieved by switching the outputs of the positive and negative groups. Inside the rectifier cabinet, a water-cooled copper busbar is used to route the N-polarity busbar to the right side of the cabinet. The water-cooled busbar uses dual-hole water cooling, and the current density of the busbar is ≤3.5A / mm², strictly controlling heat generation and reducing losses.

[0055] Water inlet pipe 131: set at the bottom of the inner side of the rectifier cabinet, connected to the water outlet of the external water-pure water cooling unit, providing an interface for cooling the oil inside the cabinet.

[0056] Water outlet pipe 132: It is set at the bottom of the inner side of the rectifier cabinet and connected to the water inlet of the external water-pure water cooling unit to provide an interface for cooling the oil inside the cabinet.

[0057] Maintenance platform 133: A platform composed of multiple anti-magnetic stainless steel plates is set in front of the rectifier cabinet body 121, which is fixed with anti-magnetic stainless steel bolts. When repairing the equipment, the fastening bolts of the platform at the part that needs to be repaired are removed and targeted maintenance is carried out.

[0058] Cabinet bracket 134: The cabinet bracket is made of anti-magnetic stainless steel channel steel and angle steel. The rectifier cabinet body 121 is raised to align the AC output line bar 118 on the low-voltage side of the rectifier transformer with the top of the fuse busbar 124. The shortest length of AC flexible copper busbar 120 is used to connect and fix the two.

[0059] Neutral point connection copper plate 135: The upper end is connected to the neutral point outlet bar 119 on the low-voltage side of the rectifier transformer and fixed with anti-magnetic stainless steel bolts, and the lower end is welded to the water-cooled hard copper tube 137.

[0060] Rectifier cabinet outgoing line connection copper plate 136: The upper end is connected to the DC output busbar M129 or DC output busbar N130 and fixed with anti-magnetic stainless steel bolts, and the lower end is welded to the water-cooled hard copper tube 137.

[0061] Water-cooled hard copper tube 137: It is welded to the neutral point connection copper plate 135 or the rectifier cabinet outlet connection copper plate 136 on the rectifier side, and supported by the insulating bracket 138. It is plugged and fixed to the water-cooled flexible copper tube 139 at the end with a Haver sleeve, and the inner diameter of this copper tube is consistent with the inner diameter of the water-cooled flexible copper tube 139.

[0062] Insulating bracket 138: Use an insulating bracket to fix the water-cooling hard copper tube 137.

[0063] The water-cooled flexible copper tube 139 is connected and fixed to the water-cooled hard copper tube 137 at the rectifier end and is connected and fixed to the electrode water-cooled copper tube 141 at the electrode end.

[0064] Electrode body 140: A component that injects electrical energy into the DC submerged arc furnace, provides support for the electrode water-cooled copper tube 141, and is connected to the side of the contact element 142 in an arc shape.

[0065] The electrode water-cooling copper tube 141 has one end connected and fixed to the water-cooling flexible copper tube 139 through a Haversian sleeve, and the other end is welded to the contact element 142 .

[0066] Contact element 142: The upper end is welded to the electrode water-cooling copper tube 141, and the side surface is connected to the electrode body 140 shell in an arc shape. It is compressed by a pressure spring to maintain a certain contact force to reduce contact resistance.

[0067] The rectifier system utilizes a double-reverse star-type, in-phase, anti-parallel configuration with either a balancing reactor or a three-phase, five-column rectifier transformer equipped with an on-load tap changer. Two rectifier power supply systems are installed for each of the four electrodes, each providing DC power to two electrodes and considered a single unit. Each unit consists of a rectifier transformer, two six-pulse rectifier panels, a control panel, an oil-water cooler, a pure water cooler, sensors, a connecting busbar, and other necessary accessories. The valve-side outputs of each rectifier transformer in a single unit are staggered by 30°, resulting in a 12-pulse output from two six-pulse rectifiers for each electrode pair. For a single furnace system, the valve-side outputs of the two rectifier transformers are staggered by 15°, resulting in an equivalent 24-pulse output from the two rectifier systems. Voltage regulation utilizes 31-stage on-load tap changers for coarse regulation and thyristors within the rectifier panels for fine regulation. The rectifier transformer and rectifier cabinet are compactly installed in the area next to the DC submerged arc furnace. The rectifier transformer oil-water cooler is installed next to the rectifier transformer, and the rectifier cabinet pure water-water cooler is installed next to the rectifier cabinet.

[0068] like Figure 3As shown, the positive and negative thyristors are not operated simultaneously. A logical control method ensures that, under all circumstances, when the positive thyristors are operating in parallel, the negative thyristors are blocked. Similarly, when the negative thyristors are operating, the positive thyristors are blocked, resulting in a reverse current flowing through the electrodes. This allows the electrodes to switch between positive and negative polarity by switching the outputs of the positive and negative groups. The thyristor triggering system utilizes a logic-free, non-circulating current control method. The positive thyristors are active (trigger pulses are applied) while the negative thyristors are blocked (no trigger pulses are applied). To ensure reliable switching between the positive and negative groups, the actual output current must reach zero and a certain delay must have elapsed (to ensure that the previously on thyristors have completely turned off) before switching between the positive and negative groups is allowed. The thyristor control system of this device utilizes zero-crossing triggering. This control mode uses a set time period to determine the number of thyristor conduction cycles within the operating cycle. The duration of the variable cycle is used to control the output power. The electrode current setpoint can be arbitrarily selected through parameter design, such as 0-10V or 4-20mA. The trigger unit's synchronization signal is derived from the high-voltage side PT (AC100V). The gates of the parallel thyristors utilize active strong trigger control units, one for each arm. The strong trigger pulse has a leading edge amplitude of 3-4A, a leading edge rise time of less than 1 microsecond, and a flat-top pulse amplitude of 1A, thereby reducing the output power of the gate trigger unit. The output current and voltage are fed into the DCS control system and into the microcomputer-based integrated automated monitoring and protection system for remote control and telemetry.

[0069] Fuse 122 component fault protection: The fast-acting fuse microswitch contacts of each component arm are centrally collected and sent to the unit DCS control system. A component working status simulation diagram is created in the software according to the main circuit of the rectifier cabinet. When a component fast-acting fuse is actuated, a rectifier cabinet simulation diagram of the faulty rectifier unit is automatically displayed on the display screen of the host computer, and the damaged component flashes. When one component is damaged, an alarm signal is issued. When two components are damaged, the output contacts act to trip the unit.

[0070] A monitoring and early warning system for a DC ore-bearing furnace rectification power supply system, comprising: Pressure gauge, used to collect the pressure at the cooling pure water inlet inside the rectifier cabinet unit; Thermometer: used to collect the temperature of the cooling pure water outlet inside the rectifier cabinet unit; Multiple temperature measurement modules: used to collect the temperature of multiple bridge arm busbars in the rectifier cabinet unit; Insulation monitoring device: used to monitor insulation damage on the AC side and DC side of the main circuit in the rectifier cabinet unit; DC high current measuring instrument: used to measure the current of the neutral point outgoing line of each rectifier transformer low voltage side; The first current transformer is used to detect the actual current on the primary side of the rectifier transformer unit; The second current transformer is used to detect the actual current on the secondary side of the rectifier transformer unit; The third current transformer is used to detect the actual values ​​of the eight DC high currents on the neutral point outgoing line bar on the low-voltage side of the rectifier transformer; Central control room host computer: receives the pressure gauge, temperature gauge, multiple temperature measurement modules, insulation monitoring device, DC high current measuring instrument, first current transformer, second current transformer and third current transformer transmitted through the DCS control system and the judged alarm signals, realizing information interaction with process operators.

[0071] A pressure gauge with contact output is installed at the cooling pure water inlet of the rectifier cabinet. When the water inlet pressure is lower than 0.1MPa, the output is a contact signal that causes the unit to trip. At the same time, the signal is communicated to the host computer in the central control room through the unit DCS control system.

[0072] A temperature gauge with contact output is set at the cooling pure water outlet of the rectifier cabinet. When the cooling return water temperature is higher than 50℃, the unit DCS control system outputs a signal to the host computer in the central control room, and an audible and visual alarm signal is issued.

[0073] The rectifier cabinet is equipped with a bridge arm busbar temperature detection system. Each busbar is equipped with a set of temperature measuring devices. The signals are input into the unit DCS control system. The DCS control system monitors the temperature of each busbar online and creates a busbar working status simulation diagram based on the actual rectifier cabinet in the software. When the temperature of a busbar is higher than 55℃, the faulty rectifier unit dynamic rectifier cabinet simulation diagram is automatically displayed on the upper computer screen in the central control room. At the same time, an audible and visual alarm signal is output, and a tripping signal is output with a delay to trip the unit. At the same time, the signal is output to the upper computer in the central control room through the unit DCS control system.

[0074] The metal casing of the rectifier cabinet is installed using an insulated method. An insulation monitoring device is installed inside the rectifier cabinet to detect insulation damage on the AC side and DC side of the main circuit. When the insulation between the AC side and ground in the rectifier cabinet is damaged, an alarm signal is generated, which is output to the central control room host computer via the unit's PLC. When the insulation between the DC side and ground in the rectifier cabinet is degraded, an alarm signal is generated, which is also output to the central control room host computer via the unit's DCS control system.

[0075] The DCS control system provides relay operation, signal protection, status monitoring, and information transmission for the rectifier cabinet, rectifier transformer, and ancillary equipment. Each unit in this system is equipped with a programmable controller (PLC), each with a communication interface, which transmits information to the central microcomputer control system via a communication network.

[0076] The rectifier cabinet body 121 has a safety margin of more than 3.5 times when it meets normal operation during actual operation. When a rectifier element fuse 122 or thyristor 123 of a parallel arm is damaged, the rectifier cabinet can safely operate in n-1 operation mode and still meet the normal current output requirements.

[0077] When the rectifier equipment is in operation, the harmonic current injected into the grid connection point by the rectifier system shall not exceed the distortion range specified in the national standard GB / T14549-93 "Power Quality Public Grid Harmonics".

[0078] A DC Hall detection type industrial DC high current measuring instrument is installed on the neutral point outlet bar 119 on the low-voltage side of each rectifier transformer. A total of 8 instruments are configured for each rectifier transformer. The instrument adopts an open structure to facilitate installation after the rectifier system is in place and connected. The instrument uses Hall elements as detection elements and can be used to measure 0-700kA DC high current. The measured DC high current is converted into a Hall current signal proportional to the measured DC through multiple Hall elements. The electronic circuit performs summing, amplification and linearization processing to convert it into a rated DC voltage signal of 0-5V and a rated DC current signal of 4-20mA for output, so as to facilitate the user's use with various secondary instruments and protection.

[0079] like Figure 3 As shown, the actual current value detected by the first current transformer on the primary side of the modulator is marked as ITBA. The sum of the current values ​​measured by the second and third current transformers on the primary sides of the two main transformers is equal to the current value on the secondary side of the modulator, marked as IZBA. The sum of the actual values ​​of the eight DC high currents on the neutral point output bus 119 on the low-voltage side of the rectifier transformer is marked as IdA. Table 1 shows the nameplate data of the rectifier transformer. Table 1 is the nameplate data of the rectifier transformer

[0080] In Table 1, the primary current, modulated secondary current, and DC current are Figure 3 The detection positions in the table correspond to ITBA, IZBA, and IdA respectively. In actual operation, ITBA, IZBA, and IdA should be smaller than the nameplate data of the corresponding gear in Table 1. However, the proportional relationship between the three is fixed. If it is detected that the proportional relationship is no longer fixed, a short circuit or ground fault may have occurred inside the system, and an early warning signal needs to be issued. When the corresponding deviation is too large, an alarm signal is directly output to trip the upper high-voltage circuit breaker.

[0081] The rectifier system is differentially protected using three-position differential combined protection, that is, current transformers are installed at the primary side of the modulation transformer, the primary side of the main transformer, and the low-voltage side of the rectifier transformer to perform current differential protection at three locations. The flow chart is as follows: Figure 4As shown in Table 1, the nameplate rated values ​​of the primary current, modulated secondary current, and DC current at different switch positions are marked as I TBi , I ZBi , I di , where i=1, 2…31, and the 20th gear is the rated gear of the rectifier system.

[0082] S201. Calculate the rated value of the proportional coefficient K i1 =I ZBi / I TBi , K i2 = I di / I ZBi , K i3 = I di / I TBi ; S202, calculate the actual value of the proportional coefficient K1=I ZBA / I TBA , K2= I dA / I ZBA , K3= I dA / I TBA ; S203, calculate the three-digit running difference values: = (K1-K i1 ) / K i1 , = (K2-K i2 ) / K i2 , = (K3-K i3 ) / K i3 S204, calculate the comprehensive difference degree

[0083] S205, make early warning judgment, when the difference comprehensive difference degree When the value is greater than 1.5%, an early warning signal will be output. When the value is greater than 2.5%, an alarm signal will be output.

[0084] At the same time, the imbalance monitoring method is used to carry out early warning monitoring of the rectifier system. The actual values ​​of the 8 DC large currents on the neutral point output line 119 on the low-voltage side of the rectifier transformer are marked as I dNi , where i=1, 2…8. When the 8 groups of current are balanced, it indicates that the entire system is running well. When the operation is unbalanced, it indicates that there may be a short circuit or grounding fault inside the system. Early warning and alarm are issued according to the imbalance.

[0085] The specific process of the imbalance monitoring method is as follows: Figure 5 As shown, S301, calculate the average value of neutral point current I dNav = (I dN1 +I dN2 +…+ I dN8 ) / 8 S302, calculate the current difference imbalance of each neutral point ζ1= (I dN1 -I dNav ) / I dNav ,ζ2= (I dN2 -I dNav ) / I dNav ,…,ζ8= (I dN8 -I dNav ) / I dNav S303, calculate the comprehensive difference imbalance

[0086] S304: Make a warning judgment. When the comprehensive difference imbalance degree ζ is greater than 1%, a warning signal is output; when ζ is greater than 2%, an alarm signal is output.

[0087] Predictive maintenance tests the condition of equipment to determine if a failure is imminent in the foreseeable future, allowing changes to be made to the relevant process at the most appropriate time. Although monitoring equipment alone cannot prevent component failures, plant maintenance personnel can extend the life of assets at the lowest cost by more accurately predicting potential failures and replacing components before they fail. The advantages of predictive maintenance include reduced downtime, lower repair and spare parts inventory costs, and the avoidance of secondary damage. This strategy is particularly effective for critical assets with high downtime costs, assets with a history of failures, or those that are difficult to reach and make routine inspections difficult or dangerous.

[0088] We have designed and developed a DC submerged arc furnace rectification power supply monitoring and early warning system, some of the related technologies of which can be partially applied and extended to AC submerged arc furnace control systems. This part of the technology is also within the scope of protection of this plan and is subject to the constraints of this technical plan.

[0089] The newly developed DC submerged arc furnace rectifier power supply monitoring and early warning system implements DC submerged arc furnace rectifier power supply monitoring. It can be used for three-position differential combined protection of the power supply system and early warning of equipment imbalance. This system improves efficiency and reduces costs, ensures safe and continuous production, avoids "excessive maintenance," reduces maintenance time, and reduces labor intensity. It provides reliable and effective data support for DC submerged arc furnace production, stabilizes production, improves economic benefits, and enhances the overall intelligence level of submerged arc furnaces. Furthermore, the system's unique intelligent technology, with independent intellectual property rights, is gradually integrating with cutting-edge control technologies, significantly enhancing the competitive advantage of general contractors.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A DC ore-fired furnace rectification power supply system, characterized by: include: High-voltage incoming line unit: used to introduce high voltage from the high-voltage substation; Rectifier transformer unit: used to input AC power from the high voltage grid side into the high voltage input unit, adjust the voltage to the voltage required for smelting through the rectifier transformer, and output the voltage through the AC flexible copper busbar; Rectifier cabinet unit: used to receive the AC power output by the rectifier transformer unit and convert it into DC power, adjust it to the voltage flow required for smelting, and use the positive group thyristors and the negative group thyristors in turn at different times to switch the positive and negative polarity of the DC submerged arc furnace electrodes; A secondary bus unit, used for transmitting the DC power output by the rectifier cabinet unit; Electrode unit: used to receive the current required for smelting of the DC submerged arc furnace output by the secondary bus unit and heat the DC submerged arc furnace.

2. A DC ore-bearing furnace rectification power supply system according to claim 1, characterized in that: The rectifier transformer unit adopts a double reverse star type in-phase anti-parallel structure; A bracket is provided under the rectifier cabinet unit for raising the rectifier cabinet unit; The neutral point of the low-voltage side of the rectifier transformer unit is connected to the lower part of the rectifier transformer body as far as possible, and the AC bus of the low-voltage side of the rectifier transformer unit is connected to the upper part of the rectifier transformer body and is directly connected to the elevated rectifier cabinet unit horizontally; The secondary busbar unit passes horizontally through the bracket set under the rectifier cabinet unit, and is connected to the contact elements attached to the electrode unit without passing through the busbar, ensuring that the length of the connecting copper bars and copper pipes of each part is the shortest, so as to ensure the lowest total loss during system operation.

3. The DC ore-generating furnace rectification power supply system according to claim 1, characterized in that: The rectifier transformer unit includes a rectifier transformer body; The rectifier transformer body includes a voltage regulating transformer, two phase-shifting rectifier transformers and an on-load tap-changing switch; A rectifier transformer box is provided outside the rectifier transformer body; A high-voltage bushing is provided on the upper part of the rectifier transformer box, and the internal conductor core of the high-voltage bushing is connected to the three phase lines of the high-voltage incoming line terminal of the voltage regulating transformer; A high-voltage neutral point is provided on the upper part of the rectifier transformer box. The internal conductor core of the high-voltage neutral point is connected to the neutral point line of the high-voltage incoming line terminal of the voltage-regulating transformer and is externally connected to a dedicated neutral point grounding device to achieve grounding protection for the rectifier transformer unit. A rectifier transformer low-voltage side AC output line bar is provided on the upper part of the side of the rectifier transformer box, which is connected to the valve side three-phase line of the main transformer inside the rectifier transformer; A rectifier transformer low-voltage side neutral point outlet bar is provided at the lower part of the side of the rectifier transformer box, and is connected to the valve side neutral point of the main transformer inside the rectifier transformer; An extended cross copper busbar is used inside the rectifier transformer body, with the four left terminals having the same polarity M and the four right terminals having the same polarity N. The outgoing copper busbar is led out from the lower part of the long side of the transformer box.

4. The DC ore-bearing furnace rectification power supply system according to claim 1, characterized in that: The main unit of the rectifier cabinet includes a main cabinet body, which is an anti-magnetic structure and is made of high-quality cold-rolled steel plate as the main material and stainless steel with magnetic treatment; The support member is made of high-strength epoxy resin, which prevents the magnetic flux from forming a loop, thereby preventing local vibration and heating caused by the possible high current magnetic field; A fuse and a thyristor are arranged inside the main cabinet body; One side of the fuse is attached to the fuse busbar, and the other side of the fuse is attached to the single connecting bar; the top of the fuse busbar is connected to the AC flexible connecting copper bar; The fuse elements and fuse copper bars are arranged close to each other using in-phase anti-parallel copper bars, so that the magnetic fluxes in opposite directions cancel each other out. One side of the thyristor is attached to the positive group thyristor bus bar or the negative group thyristor bus bar, and the other side of the thyristor is attached to a single connecting bar; The positive polarity rows and negative polarity rows of the positive group thyristor busbars are alternately arranged in the depth direction, the positive polarity rows are connected to the negative ends of the positive group thyristors, and the negative polarity rows are connected to the positive ends of the positive group thyristors. The upper or lower end of the positive group thyristor bus is connected to the negative group thyristor bus, the lower end of the positive polarity bus is connected to the DC output bus M, and the lower end of the negative polarity bus is connected to the DC output bus N, and fixed with anti-magnetic stainless steel bolts; The negative polarity rows and the positive polarity rows of the reversed thyristor busbars are alternately arranged in the depth direction, the negative polarity rows are connected to the negative ends of the reversed thyristors, and the positive polarity rows are connected to the positive ends of the reversed thyristors.

5. The DC ore-generating furnace rectification power supply system according to claim 1, characterized in that: It also includes a rectifier element trolley body, on which the fuses, thyristors, fuse busbars, single-branch connecting bars, positive thyristor busbars, and negative thyristor busbars are all fixed. The fuses, thyristors, fuse busbars, single connecting bars, positive thyristor busbars, and negative thyristor busbars are fixed to the rectifier element trolley body using insulating elements and anti-magnetic stainless steel bolts to form an integrated structural component that can be disassembled as a whole during maintenance; A plurality of wheels are provided on the bottom bracket of the rectifier element trolley body for transporting the rectifier element as a whole after disassembly.

6. The DC ore-generating furnace rectification power supply system according to claim 1, characterized in that: The process of switching the positive and negative polarities of the DC submerged arc furnace electrodes by taking turns using the positive group thyristors and the negative group thyristors at different times is as follows: When the positive group thyristors are put into use, the output of the positive group thyristor bus and the DC output bus M is positive polarity, and the output of the negative group thyristor bus and the DC output bus N is negative polarity; When the reverse group of thyristors is put into use, the output of the positive group of thyristor busbars and the DC output busbar M is negative polarity, and the output of the reverse group of thyristor busbars and the DC output busbar N is positive polarity; The positive group thyristors and the reverse group thyristors are not put into use at the same time to ensure that under any circumstances when the positive group thyristors work in parallel, the reverse group thyristors are in a blocked state; similarly, when the reverse group thyristors work, the positive group thyristors are in a blocked state, and a reverse current is obtained on the electrode. The positive and negative polarity switching of the electrode is realized by switching the output of the positive and reverse groups.

7. A monitoring and early warning system for a DC submerged arc furnace rectification power supply system according to any one of claims 1 to 6, characterized in that: include: Pressure gauge, used to collect the pressure at the cooling pure water inlet inside the rectifier cabinet unit; Thermometer: used to collect the temperature of the cooling pure water outlet inside the rectifier cabinet unit; Multiple temperature measurement modules: used to collect the temperature of multiple bridge arm busbars in the rectifier cabinet unit; Insulation monitoring device: used to monitor insulation damage on the AC side and DC side of the main circuit in the rectifier cabinet unit; DC high current measuring instrument: used to measure the current of the neutral point outgoing line of each rectifier transformer low voltage side; The first current transformer is used to detect the actual current on the primary side of the rectifier transformer unit; The second current transformer is used to detect the actual current on the secondary side of the rectifier transformer unit; The third current transformer is used to detect the actual values ​​of the eight DC high currents on the neutral point outgoing line bar on the low-voltage side of the rectifier transformer; Central control room host computer: receives the pressure gauge, temperature gauge, multiple temperature measurement modules, insulation monitoring device, DC high current measuring instrument, first current transformer, second current transformer and third current transformer transmitted through the DCS control system and the judged alarm signals, realizing information interaction with process operators.

8. The monitoring and early warning system for a DC ore-bearing furnace rectification power supply system according to claim 7, characterized in that: The alarm signals of the first current transformer, the second current transformer, and the third current transformer are used to perform differential protection on the rectifier system through three-position differential joint protection. That is, current transformers are installed at three locations, namely, the primary side of the modulation transformer, the primary side of the main transformer, and the low-voltage side of the rectifier transformer, to perform current differential protection at the three locations. The specific process is as follows: The nameplate ratings of the modulated primary current, modulated secondary current, and DC current at different switch positions are marked as I TBi , I ZBi , I di , where i=1, 2…31, the 20th gear is the rated gear of the rectifier system; S201. Calculate the proportional coefficient K between the modulated primary current and the modulated secondary current. i1 =I ZBi / I TBi , K i2 =I di / I ZBi , K i3 =I di / I TBi ; where i = 1, 2…31; S202, calculate the actual value of the proportional coefficient between the modulated primary current and the modulated secondary current K1=I ZBA / I TBA , K2 =I dA / I ZBA , K3 =I dA / I TBA； S203, based on the rated value of the proportional coefficient between the modulated primary current and the modulated secondary current and the actual value of the proportional coefficient between the modulated primary current and the modulated secondary current, calculate the three-digit operation difference degrees respectively: = (K1 -K i1 ) / K i1 , = (K2 -K i2 ) / K i2 , = (K3 -K i3 ) / K i3 S204: Calculate the comprehensive difference based on the three-digit operation difference ; S205, make early warning judgment, when the difference comprehensive difference degree When the temperature is higher than 1.5%, an early warning signal will be output. When the value is greater than 2.5%, an alarm signal will be output.

9. The monitoring and early warning system for a DC ore-bearing furnace rectifier power supply system according to claim 7, characterized in that: The alarm signals of the first current transformer, the second current transformer and the third current transformer are used to perform differential protection on the rectifier system through the three-position differential joint protection. That is, current transformers are installed at three locations, namely, the primary side of the modulation transformer, the primary side of the main transformer and the low-voltage side of the rectifier transformer, to perform current differential protection at the three locations. The process also includes the following: At the same time, the imbalance monitoring method is used to carry out early warning monitoring of the rectifier system. Specifically, the actual values ​​of the 8 DC large currents on the neutral point output line of the rectifier transformer low voltage side are marked as I dNi , S301, calculate the average value of neutral point current I dNav = (I dN1 +I dN2 +…+ I dN8 ) / 8 S302. Calculate the unbalance degree of each neutral point current difference based on the average value of the neutral point current: ζ1= (I dN1 -I dNav ) / I dNav ,ζ2= (I dN2 -I dNav ) / I dNav ,…,ζ8= (I dN8 -I dNav ) / I dNav S303. Calculate the comprehensive difference imbalance ζ based on the current difference imbalance of each neutral point: S304. Based on the comprehensive difference imbalance, a warning judgment is made. When the comprehensive difference imbalance ζ is greater than 1%, a warning signal is output; when ζ is greater than 2%, an alarm signal is output.

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