Reactors - TRENCH Group

1 ReactorsIntroductionWith 40 years of successful fieldexperience, TRENCH is therecognized world leader in the design and manufacture of air core,dry type, power Reactors for all utility and industrial unique, custom design ap-proach, along with fully integratedengineering and manufacturingfacilities in both North Americaand Europe have enabled TRENCH to become the technicalleader for high voltage deep commitment to the powerindustry, along with extensive investment in engineering, manufacturing and test capabilitygive TRENCH customers the utmost in high quality, reliableproducts which are individually designed for each application. TRENCH reactor applications havegrown from small, distributionclass, current limiting Reactors tocomplex EHV applied Reactors surpassing 300 MVA per Management systems iscertified to ISO 9001, ISO 14001and OHSAS18001. TRENCH 'shighly developed research anddevelopment program constantlyaddresses new technologies andtheir potential application inreactor welcomeschallenges fornew applications for power brochure outlines the features,capabilities and applications of TRENCH Reactors .

2 Although air-core, dry type reactorsrepresent the majority of reactorproduction volume, Trenchalso produces a highly successfulline of iron core/iron shielded andoil type Reactors for specific appli-cation (eg. Resonance Grounding/Petersen Coils). These Reactors arealso described in detail in othersections of the TRENCH product Features of Air-Core Dry Type Reactors Epoxy impregnated, fibreglassencapsulated construction Aluminum construction through-out with all current carryingconnections welded Highest mechanical and shortcircuit strength Essentially zero radial voltagestress, with uniformly gradedaxial voltage distribution between terminals Low noise levels are maintainedthroughout the life of the reactor Weatherproof construction, withminimum maintenance require-ments Design service life in excess of30 years Designs available in compliancewith ANSI/IEEE, IEC and othermajor 1 Three-phase stacked current limiting reactor2 Series ReactorsReactors connected in series withthe line or feeder.

3 Typical uses arefault current reduction, load balancing in parallel circuits, limi-ting inrush currents of capacitorbanks, ApplicationsFig. 2 Schematic diagramFig. 4 Current limiting reactorFig. 3 Single phase series reactorsTrench Reactors are utilized on transmission anddistribution systems. Although it is not possible to listall reactor applications, some of the most common aredescribed Limiting Reactors ,reduce the short circuit current tolevels within the rating of theequipment on the load side of thereactor. Applications of current limiting Reactors range from the simpledistribution feeder reactor to largebus-tie and load balancing reactorson systems rated up to 765 kV/2100 kV Reactors are designedto be installed in series with ashunt connected capacitor bank tolimit inrush currents due to switching, to limit outrush currentsdue to close in faults and to controlthe resonant frequency of the system due to the addition of thecapacitor banks. Reactors can beinstalled on system voltagesthrough 765 kV/2100 kV BIL.

4 When specifying capacitor Reactors ,the requested continuous currentrating should account for harmoniccurrent content, tolerance on capacitors and allowable Reactors forElectric Arc Furnaces (EAF).The most effective use of EAFs isachieved by operating the furnaceat low electrode current and longarc length. This requires the use ofa series reactor in the supply systemof the arc furnace transformer forstabilizing the 5 Buffer reactorfor 6 Load flow control reactorsDuplex Reactorsare current limiting Reactors which consist oftwo half coils, wound in Reactors provide a desirablelow reactance under normal con-ditions and a high reactance underfault Flow Control Reactorsareseries connected on transmissionlines up to 800 Reactors change the line impedance characteristic such thatload flow can be controlled, thusensuring maximum power transferover adjacent transmission Reactors Filter Reactors are used in conjuctionwith capacitor banks to form series tuned harmonic filter circuits,or in conjunction with capacitorbanks and resistors to form broad-band harmonic filter specifying filter Reactors ,the magnitudes of fundamentaland harmonic frequency currentshould be indicated.

5 If inductanceadjustment for fine tuning is required, the required tapping rangeand tolerances must be filter applications require aQ-factor which is very much lowerthan the natural Q of the is often achieved by connectinga resistor in the economical alternative is theaddition of a de Q'ing ring structureon a reactor. This can reduce theQ-factor of the reactor at tuningfrequency up to as much as onetenth without the necessity of in-stalling additional damping resi-stors. (see Fig. 9 below)These rings, mounted on the reactorare simply coupled to the magneticFig. 8 Filter reactorsFig. 9 Filter Reactors with de Q ing ringsFig. 7 Schematic diagramFig. 10 Capacitor/filter protection relayfield of the reactor. This eliminatesthe concern of space, connectionand reliability of additional compo-nents such as Capacitor/Filter ProtectionRelay CPR 04is a microprocessorbased protection relay speciallydesigned for optimized protectionof shunt banks and harmonic VAR Compensators are used on transmission systems to improvethe overall reliability, correct forvoltage fluctuations and power factor as well as increasing the transmission capability and reducing ReactorsShunt Reactorsare used to compensate for capacitive VARsgenerated by lightly loaded trans-missionlines or underground cables.

6 They are normally connectedto the transformer tertiary windingbut can also be directly connectedon systems up to 115 11 Schematic diagramFig. 14 Thyristor controlled reactorFig. 12 Tertiary connectedshunt reactorsFig. 13 Thyristor controlled shunt Reactors and filterreactors in a Static VAR Compensator Thyristor Controlled Shunt Reactorsare extensivelyused in static VAR systems, wherereactive VARs are adjusted by thyristor circuits. Static VAR compensator reactor applicationsnormally include: Thyristor controlled shunt Reactors (TCR). The compensating poweris changed by controlling thecurrent through the reactor bymeans of the thyristor valves. Thyristor switched Reactors (TSR) Thyristor switched capacitor Reactors (TSC) Filter Reactors (FR)6 HVDC-ReactorsHVDC lines are used for long distance bulk power transmissionFig. 15 Schematic diagramFig. 17 HVDC-Smoothing reactorFig. 16AC-Filtersa) AC - PLCb) AC - FRc) HVDC - SMRd) DC - FRe) DC - PLCas well as back-to-back inter-connections between differenttransmission Reactors normally includeSmooting Reactors , AC and DCHarmonic Filter Reactors as well as AC and DC PLC Noise Filter ReactorsSmoothing Reactors are used to reduce the magnitude of the ripplecurrent in a DC system.

7 They areused in power electronics applications such as variable speeddrives and UPS systems. They arealso required on HVDC transmissionlines for system voltages up to500 kV. Several design and constructiontechniques are offered by 18 Schematic diagramFig. 19 Iron core, forced air cooled reactorFig. 20 Air core, encapsulated winding designFig. 21 Iron core, water cooled reactor8 Test Lab ReactorsTest Lab Reactors are installed inhigh voltage and high power testlaboratories. Some typical applications include current limiting,synthetic testing of circuit breakers,inductive energy storage, artificiallines, 22 Schematic diagramFig. 23 Reactor bank for the voltage circuit for synthetic testingof circuit breakers; 32 kA peak to peak, 0,318 mH to 353,6 mH, up to 1600 kV BILFig. 25 Short circuit test reactorFig. 24 Adjustable current limiting reactor9 Neutral Grounding ReactorsNeutral Grounding Reactors limitthe line to ground fault current tospecified levels. Specificationshould also include unbalancedcondition continuous current 26 Schematic diagramFig.

8 27 Arc suppression coil 110 kVFig. 28 Standard arc suppression coilArc Suppression CoilsSingle-phase neutral grounding(earthing) Reactors (arc suppressioncoils) are intended to compensatefor the capacitive line-to-groundcurrent during to a single arc suppression coil (ASC) represents the central element ofthe TRENCH earth fault protection the electric system is subjectto changes, the inductance of theASC used for neutral earthingmust be earth fault detection systemdeveloped by TRENCH utilizes theplunger core coil (moveable coredesign). Based on extensive experi-ence in design, construction andapplication of ASCs, Trenchproducts can meet the moststrin-gent requirements for earth faultcompensating TRENCH air core dry type reactorconsists of a number of parallelconnected, individually insulated, aluminum (copper onrequest) conductors. These conductorscan be small wire orproprietarycables custom designedand size and type of conductorused in each reactor is dependanton the reactor specification.

9 Thevarious styles and sizes of conductors available ensure optimum performance at the mosteconomical cost. The windings aremechanically reinforced withepoxy resin impregnated fibreglass,which after a carefully definedoven cure cycle produces an encapsulated coil. A network ofhorizontal and vertical fibreglassties coupled with the encapsulationminimizes vibration in the reactorand achieves the highest availablemechanical windings are terminated ateach end to a set of aluminum barscalled a spider. This constructionresults in a very rigid unit capableof withstanding the stresses developed under the most severeshort circuit high levels of terminalpull, tensile strength, wind loadingand seismic withstand can be accommodated with the Fig. 29 for details on unique design can be installedin all types of climates and environments and still offer optimum air core dry type Reactors are installed in pollutedand corrosive areas supplyingtrouble free operation. In additionto the standard fixed reactancetype of coil, units can be suppliedwith taps for variable number of methods are availableto vary inductance for fine tuningor to provide a range of larger inductance utilizes various otherdesigns for Reactors (eg.)

10 Iron core,water cooled, etc.) which aredescribed in other sections of 29 Typical TRENCH air core dry typereactor construction11It is the customer's responsibilityto consider these minimum clearances, especially if steel reinforcing in concrete foundationsor floors, or structural steel is involved in the building or stationdesign. It is important, even outsidethese minimum magnetic clearan-ces, to avoid closed electrical loopswith metallic ClearanceDIf required, non-magnetic extensionbrackets can be supplied by TRENCH to maintain the necessary magnetic clearancebelow the reactor. TRENCH canprovide additional details on spacerequirements and recommended reinforcing steel(rebar) design, if ClearenceMinimum clearances to metallicparts, and between coils, must bemaintained as indicated by Figs. 32and 33. The values shown are onlyguidelines. Each specific reactordesign will specify magnetic clearance requirements. Fig. 30 Terminal orientationFig. 31 Terminal detailsFig. 32 Minimum magnetic clearance to other Reactors and metallic parts not forming closed loops (approximate values only)Terminals12 Generally, air core, dry type Reactors can be installed in eitherside by side or vertically stackedconfigurations and are oftenadded to existing substations orlocations where space limitationsexist.