ISF2 : Switch/circuit-breaker for the control of heavy duty furnaces

Transcription

1 Power supply to electric furnaces ISF2 : Switch/circuit-breaker for the control of heavy duty furnaces Merlin Gerin Square D Telemecanique

2 Description The ideal technology for electric furnace control Safety The SF6 breaking technique is especially well suited to making and breaking furnace currents while avoiding any overvoltages likely to damage equipment on the furnace supply line. The ratings, rated current breaking under rated voltage, are held at 0 relative bars. Each pole-unit, filled to a pressure of 0.15 MPa (i.e. 1.5 relative bars), is fitted with a safety disk and diagnostic system for continuous monitoring of the SF6 pressure. Durability suitable for heavy duty The mechanical durability of the ISF2 is 50,000 mechanical switching operations with maintenance every 10,000 operations. ISF2 Application The ISF2 is a three-phase switch/circuit-breaker for indoor use based on SF6 technology. It carries out control of electric furnaces up to 40.5 kv and complies with IEC standard publications 56 and 694. Reliability The mechanical operating mechanism, based on energy storing springs, is a key feature of the device s reliability: Schneider has 25 years of experience in these types of mechanism. Because Schneider fully masters the design and monitoring of sealing systems, the device will give you lasting performances throughout its service life. Environmentally friendly The ISF2 furnace switch has been designed for environmental protection: c the materials used, insulators and conductors, are identified, easy to separate and recyclable, c the SF6 can be recovered at the end of the device service life and reused after being treated. Quality Each switch undergoes systematic routine tests for checking quality and conformity: c pole-unit sealing tested, c correct mechanical operation of the device tested together with associated locking systems, c simultaneous contact closing tested, c power frequency insulation level tested, c main circuit resistance tested, c auxiliary circuit insulation tested, c switching operation speed tested, c switching cycle tested, c switching operation times tested. The results obtained are recorded on each device s test certificate. The entire switch creation and manufacturing process is quality controlled in compliance with the French association for quality assurance (AFAQ): ISO 9002 certification. The ISF2 switch has passed type tests in compliance with IEC 56 and 265 standards. 2 ISF2 switch/circuit-breaker

3 Device description The ISF2 is a disconnectable fixed device made up of: c 3 separate pole-units, each being built into a sealed pressure system type insulating enclosure; each pole-unit is filled with SF6 at low pressure (0.15 MPa, i.e. 1.5 bars), c a Gmh type spring stored energy operating mechanism, c a front panel with the manual operating mechanism and position indicators, c upstream and downstream terminals for power circuit connection, c a multipin socket for auxiliary circuit connection, c un dispositif d auto-diagnostic, pour le contrôle permanent du gaz SF6 sur chacun des 3 pôles, équipé de : v 1 low threshold contact, for possible pressure drop indication, v 1 high threshold contact, for indication of a rise in pressure due to abnormal overheating of the pole-unit or the arcing contact wear limit being reached. a b Principle of the breaking technique auto-compression This breaking technique has been widely tried and tested and produces high performances. The arc is blown and thus extinguished by forced convection. Fig 1: The circuit-breaker is closed. Fig 2: When the main contacts open (a), the current is sent into the breaking circuit (b). Fig 3: When the arcing contacts separate an electric arc appears: this is controlled Fig 1 Fig 2 by the insulating nozzle; a piston (c) attached to the moving contact moves downwards and compresses the gas in (d); the gas then escapes via the holes in the piston into the tubular arcing contact zone, cools down and deionizes the electric arc zone, thus extinguishing the arc when the current reaches 0 point. Fig 4: The circuit-breaker is open. c d Ratings CEI 56 rated voltage kv, 50/60 Hz Fig 3 Fig 4 insulation level r.m.s. kv, 50 Hz - 1 mn rated current Isc breaking capacity making capacity allowable short time with stand current rated switching cycle kv, 1.2/50 µs impulse A r.m.s. ka peak ka r.m.s. ka, 3 s peak ka O - 3 mn - CO - 3 mn - CO operating time ms opening breaking closing electrical durability number time total (1) (1) c c 45 to to to to to to see curve p.5 see curve p.5 (1) For voltage of 36 to 40.5 kv, suitable inter-phase barriers supplied with the device must be installed by the contractor. ISF2 switch/circuit-breaker 3

4 Application example Simplified diagram 1 HV circuit-breaker 2 HV/MV step-down transformer 3 Power factor correction device 4 Protective circuit-breaker 5 Earthing switch 6 Isolation switch 7 ISF2 for furnace control 8 Voltage transformer 9 Current transformer 10 Surge arrester 11 RC circuit 12 Furnace MV/LV transformer 13 Furnace electrodes HV MV MV LV Schneider offers complete solutions for the power supply to your furnaces: consult us. ISF2 mounting in a cubicle ISF2 switch/circuit-breaker

5 Maintenance cycles Life expectancy of pole-units The stress that the device has to withstand is variable depending on the type of installation and the operating rules. The life expectancy of the poles is essentially proportional: c to the number of load current making and breaking cycles, c to the value of the furnace supply transformer rated current. Example: for an arc furnace fed by a 100 MVA transformer at 30 kv (or 67 MVA at 20 kv) with a load cycle of 2000 A, the life expectancy of an ISF2 is 28,000 CO cycles (or 50,000 CO cycles when the set of pole-units is replaced) I (A) Fig 1 - Life expectancy of a set of pole-units (number of CO cycles) depending on the furnace load current I. Electrical durability This depends on: c the furnace load current, c the circuit configuration when the device switches: v opening v closing c the rating of the furnace transformer and in particular of the inrush current during no-load energization, c the elements inserted in the furnace supply line, saturable reactor, non-saturable reactor, etc. The electrical durability can be estimated using the graph in figure 1 based on the following operating hypotheses: 1- Protection of overload currents above 2 In is carried out by the circuit-breaker located upstream. 2 - Switching operations are carried out with the electrodes out of the bath. 3 - The no-load inrush current of the furnace transformers is below 4 In. Maintenance SF6 breaking devices do not generally require special maintenance. However, since the furnace operating mechanism undergoes heavy stress, it is advisable to carry out basic maintenace involving the following operations: c depending on the ambient environment, clean the surface of the insulating enclosures; c every 10,000 switching operations: v measure the wear on the arcing contacts without removing the pole-units during inspection and maintenance operations (the auto-diagnostic system monitors wear on the pole-units throughout the device service life); v clean the operating mechanism, grease it and check the nuts and bolts. ISF2 switch/circuit-breaker 5

6 Gmh stored energy operating mechanism Operating mechanism Gmh operating mechanism The ISF2 is fitted with a Gmh type operating mechanism based on stored energy which gives the device a closing and opening speed which is not dependent on the operator. The GMh operating mechanism is made up of: c a stored energy mechanism which stores the energy required for device closing and then opening in springs; c a manual charging mechanism using a removable lever; c an electrical charging mechanism with a motor which automatically recharges the operating mechanism as soon as the device is closed; c a mechanical opening-closing mechanism actuated by 2 pushbuttons located on the front panel; c an electrical closing mechanism including: v 1 closing release for remote control, v 1 anti-pumping relay; c an electrical opening system, including 1 shunt opening release; an optional undervoltage release can be added to this device; c a mechanical position indicator with white-black or red-green mechanical indicators; c a switching operations counter. c A 14 strong auxiliary contact block including: v 2 contacts for the electrical operating mechanism, v 1 contact for the shunt release, v 11 available contacts; c 1 closing contact for operating mechanism charged indication; c 1 open position key-lock support (lock supplied); c a multipin connector (male and female) with 36 pins and a 2 metre lead. Operating mechanism low voltage auxiliaries supply voltages charging motor closing release (1) opening release M YF YO1, YO2 YM AC (V) HZ AC (V) HZ DC (V) (2) consumption AC 700 VA 120 VA 120 VA 100 VA DC 570 W 70 W 70 W 10 W Auxiliary contacts rated current 10 A breaking capacity CA 10 A at 220 V (cos ϕ <i 0.3) (1) With anti-pumping relay. (2) For other values, please consult us. CC 3 A at 110 ou 220 V (L/R <i 0.01 s) 6 ISF2 switch/circuit-breaker

7 Operating mechanism wiring diagram J KN M M1-M2 M3 QF SE Sm1 Sm2-Sm4 Sm3 Sn SP1-SP2 YF Y01-Y02 YM Circuit-breaker. Anti-pumping relay. Charging motor. End-of-charging limit switches. Operating mechanism charged contact. Circuit-breaker auxiliary contacts. Trip hold contact. Closing pushbutton (external). Opening pushbuton for shunt release(external). Opening pushbutton for undervoltage release (external). Closing disable contact (external). Pressure switch contacts. Closing release. Shunt opening release. Undervoltage release. Sm1 Sn M1 M J QF M1 M2 KN SE Sm2 Y01 Sm3 M3 Sm4 Y02 SP1 SP2 YF YM Dimensions and weights Connection pad: Ø d Ø c e b a a: fixing lugs supplied on the frame are used to anchor the device to the ground; b: the device is fitted with rollers to facilitate handling and installation; c: multipin connector; d: inter-phase barriers delivered with the 40.5 kv version; e: removable charging lever. Approximate weight: 194 kg ISF2 switch/circuit-breaker 7

8 A few furnace switch references c Cockerill Sambre MVA - Belgium c Baotou MVA - China c Betasteel MVA - United States c Ascometal - 90 MVA - France c Usinor - 55 MVA - France c Sollac - 85 MVA - France c United Steel Mill - 85 MVA - Israel c ILSA MVA - Mexico c Taleras - 38 MVA - Mexico c Aceros DMSA de CV - 35 MVA - Mexico c Huta Batory MVA - Poland c Yamato - 96 MVA - Thailand Schneider Electric SA Postal address As standards, specifications and designs change from time to This document has been F Grenoble cedex 9 time, please ask for confirmation of the information given in this printed on ecological paper. tel : +33 (0) publication. telex : merge F Design and production: AXESS (07) Printing: AMTED397053EN ISF2 switch/circuit-breaker 1 ART / 1998