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Low Voltage Switchgear Versus SwitchboardsLV switchgear and switchboards are similar in appearanceand perform similar functions, but there are someimportant differences. In general, low voltage switchgear istypically more rugged than comparable switchboards. Thisdifference translates into a higher manufacturing cost andselling price for low voltage switchgear.Another important difference relates to the different designstandards for switchboards and LV switchgear. The U. S.standards for LV switchgear were provide earlier in thiscourse. In comparison, consider that switchboards aredesigned to NEMA PB-2 and UL 891 standards. Inaddition, shown in the accompany chart, switchboards arecapable of incorporating a broader range of overcurrentprotection devices. This means that more devicestandards apply to switchboards.In summary, There are applications that can be handledeffectively with either switchboards or LV switchgear;however, there continues to be a need for both types ofproducts. Switchboards offer flexibility and a lower initialcost, and LV switchgear offers increased ruggedness andreliability that for many companies translates into a lowertotal cost of ownership. Siemens Industry, Inc. 2017Page 1-14

Online Self-paced LearningWith Siemens online self-paced learning, you select thetopics and set your own pace for completing chosencourses. All course material can be accessed online.Instruction starts upon completing the purchase of asubscription.You can choose from over 500 courses consisting of highquality graphics, on-screen text, supporting voiceovernarration, and interactive exercises. Features includeprintable course content for reference and underlined keyvocabulary terms with definitions displayed with a simplemouse-over action.Depending on the subscription purchased, you can chooseany 10 or 25 courses or select the entire online self-pacedcourse catalog.These courses are offered 24/7/365, so you can begin yoursubscription at any time. From the date of registration,you have one year to complete your course selections.For additional information: www.usa.siemens.com/sitrain Siemens Industry, Inc. 2017Page 1-15

Chapter 1 – IntroductionThis chapter covers the followingtopics: Overview WL LV Power Circuit Breakers Siemens Industry, Inc. 2017Page 1-16

WL LV Three-Pole Power Circuit Breaker RatingsWL low voltage power circuit breakers, also referred to as WL UL 1066 circuit breakers, are used in WL low voltageswitchgear as drawout-mounted breakers. They have a rated maximum operating voltage of 635 VAC and are available intwo frame sizes with frame ratings from 800 to 6000 A and continuous current ratings from 200 to 6000 A. Additionaldetails for three-pole WL power circuit breakers are provided in the chart shown below. Note that frame size I is not shownhere because it only applies to WL circuit breakers that conform to the UL 489 specification. Ratings for four-pole WLpower circuit breakers are provided in the chart on the following page. Siemens Industry, Inc. 2017Page 1-17

WL LV Four-Pole Power Circuit Breaker RatingsFour-pole breakers provide the neutral isolation capability that is advantageous for low voltage switchgear applicationswhere multiple, separately-derived power sources are individually grounded. Ratings for four-pole WL power circuitbreakers are provided in the chart shown below. Note that frame size I is not shown here because it only applies to WLcircuit breakers that conform to the UL 489 specification. Siemens Industry, Inc. 2017Page 1-18

WL Circuit Breaker Operational FeaturesWL circuit breakers can be fused or unfusedand optionally delivered with any of theseoperating mechanisms: Manual operating mechanism withmechanical closing (standard) Manual operating mechanism withmechanical and electrically-interlockedclosing Motorized operating mechanism withmechanical and electrically-interlockedclosing.As shown in the accompanying graphic, WLcircuit breakers have a number of standard andoptional features that enhance the safety andusability of the breaker, reduce errors, andminimize training time. Siemens Industry, Inc. 2017Page 1-19

Ready-to-close IndicatorOne of the standard safety features of WLlow voltage power circuit breakers is theready-to-close indicator that provides an at-aglance visual indication that the all eight ofthe necessary conditions have been met andthe breaker is in the ready-to-close state.The WL circuit breaker is ready to close if thefollowing conditions are met;1. The breaker is in the open position2. The stored-energy springs are charged3. The under-voltage release (UVR) isenergized4. The shunt trip is not energized5. The closing coil is not energized6. No interlocks are activated7. The mechanical closing lockout is reset8. The racking handle is stowed away Siemens Industry, Inc. 2017Page 1-20

Modularity of DesignWL circuit breakershave a flexiblemodular design thatincludes commonplug-in accessories,field upgradeable tripunits, and fieldchangeable contactsand arc chutes.This design minimizesinventory, allows forlast-minute changes,and is cost-effectiveto support. Siemens Industry, Inc. 2017Page 1-21

Field Installable AccessoriesWL circuit breakers offer a variety accessories and trip units that are easily mounted at the front of the breaker and eachof these devices fits all frames. Examples of some of the more common accessories are shown in the accompanyinggraphic. Siemens Industry, Inc. 2017Page 1-22

Electronic Trip Units – Part 1Three electronic trip units (ETUs) are available for use withWL circuit breakers. The protective functions andadditional capabilities available for these trip units areshown in the accompanying diagram. Some of the optionalfunctions are briefly described below and on the next pageThe switch-selectable I2t or I4t characteristic curvefunction allows the breaker’s long-time characteristics tobe set to either an I2t curve or an I4t curve to make iteasier to achieve optimal coordination.Switchable parameter sets simplify adapting the system torapid changes, such as when power is switched betweenutility power and a generator. Switching betweenparameter sets can be done quickly and, if desired,remotely. Siemens Industry, Inc. 2017Page 1-23

Electronic Trip Units – Part 2Dynamic Arc-Flash Sentry (DAS) employs the unique dualprotection settings of the ETU776 trip unit coupled with theability to toggle to a lower arc flash parameter set. Anormal parameter set can be optimized for selective tripcoordination with the alternate parameter set optimized forlower arc flash energy levels initiated when someoneapproaches the arc flash protection boundary.Extended Instantaneous Protection (EIP) is designed toprovide any WL low voltage power circuit breaker with thecapability to be applied at the short-time withstand ratingof the breaker with no instantaneous override. This featuregives downstream breakers the maximum possible time toclear a fault and reduces the likelihood of a system-wideoutage. Siemens Industry, Inc. 2017Page 1-24

Electronic Trip Unit Modularity – Part 1The modularity of WL circuit breakers extendsto the ETUs. For example, any ETU model canbe installed in any WL circuit breaker. Inaddition, as described below, selected ETUmodels can be easily adapted to changingconditions in the field by the addition orreplacement of the following ETU modules: DisplayGround fault protectionRating plugMetering function/Metering function plusCommunication.The alphanumeric LCD display is an option forETU745 (shown in the accompanying graphic)and ETU748. ETU776 comes equipped with agraphical LCD display. Siemens Industry, Inc. 2017Page 1-25

Electronic Trip Unit Modularity – Part 2Ground fault trip and alarm and ground-faultonly modules are available for ETU745,ETU748, and ETU776.The rating plug is a replaceable module used toset the continuous current rating for the circuitbreaker. Rating plugs are available for framesize II from 200 to 3200 amps and for framesize III from 800 to 6000 amps.The integrated metering function can beinstalled on ETU745, ETU748, and ETU776 tomeasure currents, voltages, power, energy,power factor, and frequency. All meteredquantities are real-time values with min/maxrecording. The metering module also providesadditional alarm setpoint and protective relayfunctions. The metering function plus modulehas additional recording capacity and supportsharmonic analysis. Siemens Industry, Inc. 2017Page 1-26

Communications Options – Part 1CubicleBUS forms the backbone of the WLcircuit breaker communication system.CubicleBUS is an internal system bus thatconnects all intelligent components in theWL circuit breaker and simplifies theconnection to external components.CubicleBUS is incorporated into all WLcircuit breakers with ETU745, ETU748, andETU776 trip units. The modular design ofthis system simplifies retrofitting ofcommunications functions. All modulesshown attached to CubicleBUS in theaccompanying graphic directly accessuseful circuit breaker data. Siemens Industry, Inc. 2017Page 1-27

Communications Options – Part 2With the addition of a COM15 PROFIBUSmodule for PROFIBUS DP communicationsor COM16 MODBUS module ( not shown)for MODBUS RTU communications, WLcircuit breakers with ETU745, ETU748, andETU776 trip units can have ETUparameters changed, and the breaker canbe opened and closed remotely. In addition,data can be shared with other systems. Fortrip units with the metering function ormetering function plus option, the breakercan take on an even wider role in a powermanagement system.The Breaker Data Adapter (BDA)incorporates configuration software andembedded web pages. This enables onlineconfiguration and diagnostics and allowsconfiguration data developed offline to bedownloaded to the trip unit.The BDA Plus has all the functionality ofthe BDA and can also connect to anEthernet network. Siemens Industry, Inc. 2017Page 1-28

CubicleBUS I/O ModulesA variety of CubicleBUS input/output (I/O) modules are available to expand thecapabilities of the WL circuit breaker. The following paragraphs summarize thecapabilities of this modules.The digital output module with rotary switch (not shown) allows up to six binarysignals to be connected to external signaling devices or used to control otherequipment. Digital and relay output versions of this module are available.The configurable digital output module allows up to six binary signals to betriggered by protective or setpoint events. Optionally, three of these outputs can beassigned in a logical-OR arrangement connected to up to six events. Both digitaland relay output versions of this module are available.The analog output module can be used to output a variety of measured values(amps, volts, power, power factor, etc.) to analog display devices on the cubicledoor. Up to two modules of this type can be connected to the WL breaker.The digital input module can connect to a maximum of six digital (24 VDC) inputs.This enables the status of a switch or the cubicle door to be communicated to thecircuit breaker. Siemens Industry, Inc. 2017Zone selective interlocking (ZSI) is a method that allows two or more circuitbreakers to communicate so that a short circuit or ground fault is cleared by thebreaker closest to the fault in the minimum time. The ZSI module is used tointerconnect WL circuit breakers in this arrangement.Page 1-29

Virtual Instructor-led LearningSiemens virtual instructor-led courses offer you a live,classroom experience with the convenience and costsavings of online learning. These courses provide hands-oninstruction and live interaction, delivered anywhere aninternet connection is available.Scheduled courses are typically 10-hour agendaspresented Monday through Friday in two-hour sessions.These sessions provide you with lecture, demonstration, labexercises, and Q&A sessions – all presented by Siemenssubject matter experts.For the full course duration, you can complete assignmentsand reinforce classroom instruction using a virtual cloudbased application providing 24/7 access to fully functionalSiemens software such as SIMATIC STEP 7 and PLCSIM.For additional information: www.usa.siemens.com/sitrain Siemens Industry, Inc. 2017Page 1-30

Chapter 2 – WL LV SwitchgearThis chapter covers the followingtopics: WL LV Switchgear Design Arc Resistant LV Switchgear Sm@rtGear LV Switchgear Siemens Industry, Inc. 2017Page 2-1

EnclosuresThe following types of enclosures are available for WL lowvoltage metal-enclosed switchgear: NEMA 1 (shown in the accompanying graphic) NEMA 3R outdoor (non-walk-in) NEMA 3R outdoor (walk-in)For NEMA 1 enclosures, rear covers with captive hardware arestandard. Rear doors with quarter-turn latches and captivescrews and rear doors with three-point latches are optional. Inaddition to the standard ventilation design, a tamper-resistantventilation design is available as an option.NEMA 3R enclosures are painted, weather-resistant steelhousings. Both enclosures sit on a six-inch high, formed steelbase which provides rigid support and a tight bottom seal. Aheavy-duty protective undercoating is applied to the under sideof the enclosure. Shielded ventilation housings permit properairflow. Walk-in enclosures have a 42-inch lighted andunobstructed service isle.The integrally mounted breaker hoist, standard on walk-inoutdoor and optional on indoor switchgear enclosures, travelsalong rails on top of the switchgear to assist in breakerhandling. Siemens Industry, Inc. 2017Page 2-2

Section TypesWL low voltage switchgear can be configured inmany ways by combining different section types.Up to five vertical sections plus a transitionsection can be shipped together as a unit. Ifrequested at order entry, the switchgear can beshipped so that it can be tilted onto its back totransport it during installation.The major assembly sections include: Transition Section - used as transition to aliquid filled transformer, to an outdoor dry-typetransformers, or other equipment such asMCCs or switchboards. Auxiliary Section - used as incoming bus ductor cable entrance when a main breaker is notused. Also utilized when utility metering or fullheight control section is required. Main Section - used to contain a main breakerand may house metering and feeder breakers. Feeder Section - used to contain feederbreakers and other equipment such asinstrumentation. Tie Section - used to contain a tie breaker andother equipment such as feeder breakers. Siemens Industry, Inc. 2017Page 2-3

Main SectionsThe accompanying graphic shows thepossible configurations for WL LVswitchgear main sections, which aresections that include a main breaker,but not a tie breaker. Siemens Industry, Inc. 2017Page 2-4

Main and Tie SectionsThe accompanying graphic shows the possible configurations for WL LV switchgear main and tie sections, which aresections that include a main breaker and a tie breaker. A tie breaker is a circuit breaker used in systems with two powersources. The tie breaker allows the user to select which source provides power to the load. Siemens Industry, Inc. 2017Page 2-5

Tie SectionsThe accompanying graphic shows the possible configurations for WL LV switchgear tie sections, which are sections thatinclude a tie breaker without a main breaker. A tie breaker is a circuit breaker used in systems with two power sources.The tie breaker allows the user to select which source provides power to the load. Siemens Industry, Inc. 2017Page 2-6

Feeder SectionsThe accompanying graphic shows the possible configurations for WL LV switchgear feeder sections, which are sectionsthat include feeder breakers and do not include main or tie breakers. Siemens Industry, Inc. 2017Page 2-7

Front Accessible FeaturesThe WL LV switchgear design incorporatesexceptional front access to key features. Forexample, all breaker settings and displays areclearly visible with the breaker door closed.The breaker can also be racked into itsconnect, test, or disconnect positions with thebreaker door closed.Control and communication wiring is routedthrough vertical and horizontal wireways inthe front of each breaker compartment andseparated from the power cables which areterminated in the rear. Opening the breakerdoor provides access to the vertical wireway.Standard control and communication wiring isnumber 14 AWG extra-flexible, strandedcopper type SIS. Siemens Industry, Inc. 2017Page 2-8

Bus Design – Part 1The standard main bus is silver-plated copper. Tinplated copper bus is optionally available. Verticaland horizontal bus bars utilize a channel shapedesign to maximize short circuit withstand capabilityand minimize heat rise. All bus joints include grade5 bolts and conical spring washers. Provisions forfuture extension of the main bus include platedjoints and high tensile strength steel hardware.The main three-phase horizontal buses arearranged vertically one phase above the other withedge-to-edge alignment to provide high, short circuitstrength. Insulated main bus with isolated verticalbus is optional.Vertical bus ratings available are 1600, 2000, 3200,4000, 5000, and 6000 amps continuous current.Horizontal bus ratings available are 1600, 2000,3200, 4000, 5000, and 6000 amps continuouscurrent. Siemens Industry, Inc. 2017Page 2-9

Bus Design – Part 2A neutral bus is furnished when specified, and canbe rated 1600, 2000, 3200, 4000, 5000, or6000 amps continuous current.A 1/4” x 3” standard copper ground bus extendsthrough all sections. Cable lugs are mounted to theground bus in each section. Standard short-circuitwithstand (4 cycle) and short-time withstand(60 cycle) bus bracing is 100,000 amperes. Highershort-circuit withstand bus bracings (150 kA and200 kA) are available.Load side runbacks for feeder circuits are copperconstruction, are insulated with sleeve tubing in themain bus area, and are supported by high-strengthbus bracing. Siemens Industry, Inc. 2017Page 2-10

CompartmentsEach complete vertical section contains thefollowing three compartments: Front compartment containing breakersand/or auxiliary equipment Bus compartment containing thehorizontal and vertical buses Rear cable compartment containing theload-side runbacks connecting the loadside of the breaker to the load cableterminals.Within the front compartment, each breakeris barriered and compartmented from allother breakers. This design also isolatesthe breakers in the front compartment fromthe bus compartment. Siemens Industry, Inc. 2017Page 2-11

Optional Barriers and LugsOptional barriers can be supplied to isolatethe bus compartment from the rear cablecompartment. Other optional barriers include: Full depth section barriers to isolate onesection from the adjacent section(s). Barriers to isolate the incoming line sideconnections to the main breaker(s) fromthe load-side bus and connections in theswitchgear section.(Note: line/load barriers are provided as astandard feature for service equi

operates in the medium voltage range. Other facilities have low voltage equipment at the service entrance. Medium voltage (MV) systems generally operate between 1000 and 38,000 volts (1 to 38 kV), although some MV systems can operate above 38 kV. The switchgear covered in this course is referred to as low voltage (LV) equipment. For