John Stark – Russelectric Inc.John Stark – Russelectric Inc.

OverviewOverview

Recent changes to the National Electrical Code (NEC) require the selective Recent changes to the National Electrical Code (NEC) require the selective coordination of overcurrent protective devices at hospitals and other mission-coordination of overcurrent protective devices at hospitals and other mission-critical facilities. critical facilities.

Transfer switches with 30-cycle closing and withstand ratings dramatically Transfer switches with 30-cycle closing and withstand ratings dramatically simplify designing to that requirement.simplify designing to that requirement.

CommercialUtility Power

UPS

UPS Batteries

Air conditioning, Lighting,Mechanical, Building Loads,etc.

Network Computer Loads

Transfer Switchgear

Generator ParallelingControl Switchgear

EmergencyGenerators

Transfer Equipment in a Common Scenario Transfer Equipment in a Common Scenario

With regard to the emergency back-With regard to the emergency back-up and transfer scheme, it is up and transfer scheme, it is incumbent upon engineers to select incumbent upon engineers to select the proper equipment for the the proper equipment for the application. There are many application. There are many considerations and they are considerations and they are becoming more with each decade.becoming more with each decade.

What is Selective Coordination?What is Selective Coordination?

• Definition Definition (Article 100 – NEC)(Article 100 – NEC)

Localization of an overcurrent condition to restrict outages to the circuit or Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective equipment affected, accomplished by the choice of overcurrent protective devices and their ratings.devices and their ratings.

““For the full range of possible overcurrents, the act of isolating an overloaded or faulted circuit For the full range of possible overcurrents, the act of isolating an overloaded or faulted circuit from the remainder of the electrical system, thereby eliminating unnecessary power outages.”from the remainder of the electrical system, thereby eliminating unnecessary power outages.”

The circuit causing the overcurrent is isolated by the selective operation of only that overcurrent The circuit causing the overcurrent is isolated by the selective operation of only that overcurrent protective device which is closest upstream to the overcurrent condition.protective device which is closest upstream to the overcurrent condition.

Article 100 provides the Code definition. Here is another way to describe it:Article 100 provides the Code definition. Here is another way to describe it:

Selective coordination was first required by the NEC in 1993 for elevator circuits. Amendments to the Code in 2005 and 2008 strengthened the requirements and expanded them to include emergency and legally required standby systems, as well as critical operations power systems. Selective coordination, as defined in the 2008 NEC,

is the (as in previous slide) “localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent protective devices and their ratings or settings.” It is a complicated process of coordinating the ratings and settings of overcurrent protective devices, such as circuit breakers, fuses, and ground fault protection relays, to limit overcurrent interruption (and the resultant power outages) to the affected circuit or equipment (the smallest possible section of a circuit). In other words, the only overcurrent protective device that should open is the device immediately “upstream” from the circuit/equipment experiencing an overcurrent condition.

Selective Coordination, History & Requirements

Proper Selective Coordination is becoming more and more of an engineering Proper Selective Coordination is becoming more and more of an engineering consideration and is being enforced by inspectors more & more often…consideration and is being enforced by inspectors more & more often…

Refer to IAEI handout “Selective coordination restricts outages to the circuit or equipment affected, Refer to IAEI handout “Selective coordination restricts outages to the circuit or equipment affected, ensuring reliability of electrical power.”ensuring reliability of electrical power.”

NEC 2008 –Verbiage on Selective CoordinationNEC 2008 –Verbiage on Selective Coordination

• NEC(2008) 700.27 Coordination: requires “Emergency system(s) overcurrent devices shall NEC(2008) 700.27 Coordination: requires “Emergency system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.”be selectively coordinated with all supply side overcurrent protective devices.”

• NEC(2008) 701.18 Coordination: requires “Legally required standby system(s) overcurrent devices shall be selectively coordinated with all supply side overcurrent protective devices.”

• NEC(2008) 517.26 Application of other articles: requires “The essential electrical system NEC(2008) 517.26 Application of other articles: requires “The essential electrical system shall meet the requirements of Article 700.”shall meet the requirements of Article 700.”

The overcurrent protective devices may include the following:The overcurrent protective devices may include the following:

Molded Case Circuit BreakersMolded Case Circuit BreakersFused devicesFused devicesInsulated Case Circuit BreakersInsulated Case Circuit BreakersAir Power Circuit breakersAir Power Circuit breakers

More on Selective CoordinationMore on Selective Coordination

RequirementsRequirements

Selective coordination requirements for life safety are not Selective coordination requirements for life safety are not a new concept for the a new concept for the CodeCode. There has been a . There has been a CodeCode requirement to coordinate selectively the over-current requirement to coordinate selectively the over-current protective devices for elevator circuits since 1993. protective devices for elevator circuits since 1993.

Most engineers agree this is the simplest way to assure Most engineers agree this is the simplest way to assure coordination, however…..coordination, however…..

BreakersBreakersInstantaneous circuit breakers will not coordinate properly Instantaneous circuit breakers will not coordinate properly because typically, they aren’t adjustable.because typically, they aren’t adjustable.

Fuses

One-lineOne-line

G Utility

4000AAPCB

1600AAPCB

1600AAPCB

800AICCB

400AMCCBAn overcurrent event (overload, short

circuit, or ground fault) here should trip the 400A MCCB

ATS

MCCB's (Molded Case Circuit Breaker) typically instantaneous or Current Limiting Devices.

ICCB's (Insulated Case Circuit Breaker) are 30 cycle withstand or up to 4 Cycle Instantaneous.

APCB's (Air Power Circuit Breaker) are typically 30 cycle withstand devices.

Selective CoordinationSelective Coordination

G Utility

4000AAPCB

1600AAPCB

1600AAPCB

800AICCB

400AMCCB

Fault on load side of ATS could see up to 30 cycles of fault current -depending on the Air Power Circuit Breaker settings that is feeding it- and could travel through the ATS and the ATS contacts.

ATS

If the 400A MCCB does not trip/clear…

ATS

In the absence of other means to satisfy selective coordination, the ATS must withstand a fault or even close on potential fault to be properly coordinated.

Review of Code RequirementsReview of Code Requirements

• Article 517 Health Care FacilitiesArticle 517 Health Care Facilities 517.26 Application of Other Articles517.26 Application of Other Articles

• Article 620 Elevators, etcArticle 620 Elevators, etc 620.62 Selective Coordination (2008)620.62 Selective Coordination (2008)

• Article 700 Emergency SystemsArticle 700 Emergency Systems 700.9 (B)(5)(b), Exception700.9 (B)(5)(b), Exception

• Article 701 Legally Required Standby SystemsArticle 701 Legally Required Standby Systems 701.18 Coordination701.18 Coordination

• Article 708 Critical Operations Power SystemsArticle 708 Critical Operations Power Systems 708.54 Selective Coordination708.54 Selective Coordination

2005 Code Adoption2005 Code Adoption

  2005 NEC   1999 NEC   2002 NEC   Local Adoption

2008 Code Adoption2008 Code Adoption

2005 NEC – 8 States

WV

WI

MT ND

SD

WA

OR

NV

ID

UT

AZ NM

TX

CO

WY

NB

M I

KY

TN

MN

IA

MO

AR

LA

MS

ILIN

OH

AL GA

KS

OK

NH

ME

NY

PA

VA

DE

NJ

MA

RI

FL

NC

SC

VT

CA

Local Adoption – (10)

MD

2008 NEC – 32 States

M I

Note: Some local adoption states have earlier than 2005 adoptions in some jurisdictions

CT

AK

State Adopted Unincorporated Areas

State Adopted

S. Carolina Code Council adopted

2009 IRC with 2008 NEC 3/22/10 with

implementation effective 1-1-11

Expected July 10’

Expected January 2011

Expected July 2010

AK

HI, basically 2002 NEC but some islands back to 1993 NEC

Revised April 19, 2010

HI

Code RulingsCode Rulings

•Panel 20 Statement:Panel 20 Statement:““The overriding theme of Articles 585 (renumbered to 708) The overriding theme of Articles 585 (renumbered to 708) is to keep the power on for vital loadsis to keep the power on for vital loads. Selective . Selective coordination is obviously essential for the continuity of service required in critical operations power systems. coordination is obviously essential for the continuity of service required in critical operations power systems. Selective coordination increases the reliability of the system.” Selective coordination increases the reliability of the system.”

In the 2008 Code Cycle there were challenges to the selective coordination requirement. Proposal 13-135 In the 2008 Code Cycle there were challenges to the selective coordination requirement. Proposal 13-135 proposed the elimination of the selective coordination requirement for 700.27.proposed the elimination of the selective coordination requirement for 700.27.

The proposal was to remove the selective coordination requirement from the mandatory text The proposal was to remove the selective coordination requirement from the mandatory text and places it in a and places it in a non-mandatory in a FPN (fine print note).non-mandatory in a FPN (fine print note).

But Code Panel 13 rejected this proposal by a vote of 9-4. To follow is their statement:But Code Panel 13 rejected this proposal by a vote of 9-4. To follow is their statement:

•Panel 13 Statement:Panel 13 Statement:“This proposal removes the selective coordination requirement from the mandatory text and This proposal removes the selective coordination requirement from the mandatory text and places it in a non-mandatory FPN (fine print note). places it in a non-mandatory FPN (fine print note). The requirement for selective The requirement for selective coordination for emergency system over-current devices should remain in the mandatory text. coordination for emergency system over-current devices should remain in the mandatory text. Selective coordination increases the reliability of the emergency system. The current working Selective coordination increases the reliability of the emergency system. The current working of the NEC is adequate.of the NEC is adequate. The instantaneous portion of the time-current curve is no less The instantaneous portion of the time-current curve is no less important than the long time portion. Selective coordination is achievable with the equipment important than the long time portion. Selective coordination is achievable with the equipment available now”.available now”.

Then, Code Panel 20, which was responsible for the new Article 708, summed up the need for selective coordination Then, Code Panel 20, which was responsible for the new Article 708, summed up the need for selective coordination in their statement to Comment 20-13, (which was another proposal for the deletion of the selective coordination in their statement to Comment 20-13, (which was another proposal for the deletion of the selective coordination requirement). requirement).

This comment was rejected 16-0. The actual panel statement to Comment 20-13:This comment was rejected 16-0. The actual panel statement to Comment 20-13:

Exceptions to Code RulingsExceptions to Code RulingsRefer to IEEE handout “Selective Coordination versus Arc Flash…” page 12Refer to IEEE handout “Selective Coordination versus Arc Flash…” page 12

There are numerous proposals being adopted by States and/or City or local governmental bodies which There are numerous proposals being adopted by States and/or City or local governmental bodies which modify the selective coordination requirements. modify the selective coordination requirements.

The most commonly heard proposals fall into two categories:The most commonly heard proposals fall into two categories:

1. Allow the degree of selective coordination needed to be the responsibility of the qualified person 1. Allow the degree of selective coordination needed to be the responsibility of the qualified person responsible for the project. responsible for the project.

Exception No. 2: Where the system design is under the control of a licensed professional engineer engaged in the Exception No. 2: Where the system design is under the control of a licensed professional engineer engaged in the design or maintenance of electrical installations, the selection of overcurrent protective devices shall be permitted to design or maintenance of electrical installations, the selection of overcurrent protective devices shall be permitted to coordinate to the extent practicable. The design shall be documented, stamped by the professional engineer, and coordinate to the extent practicable. The design shall be documented, stamped by the professional engineer, and made available for review by the authority having jurisdiction.made available for review by the authority having jurisdiction.

(The Commonwealth of Massachusetts was the first State to adopt such a proposal as an exception to (The Commonwealth of Massachusetts was the first State to adopt such a proposal as an exception to the Articles in 700.27, 701.18 and 708.54, which require selective coordination as follows:the Articles in 700.27, 701.18 and 708.54, which require selective coordination as follows:

Arc Flash ConsiderationsArc Flash ConsiderationsRefer to IEEE handout “Selective Coordination versus Arc Flash…” page 10Refer to IEEE handout “Selective Coordination versus Arc Flash…” page 10

This is the other side of the argument regarding the subject of Selective Coordination VS Arc Flash This is the other side of the argument regarding the subject of Selective Coordination VS Arc Flash Considerations.Considerations.

The presenter will not delve into this side of the argument, as he is in the business of providing emergency powerThe presenter will not delve into this side of the argument, as he is in the business of providing emergency powerto critical facilities and therefore is in the camp of having a non-sensitive, robust type system, selectively coordinated, to critical facilities and therefore is in the camp of having a non-sensitive, robust type system, selectively coordinated, that facility managers want to perform well when called upon. In cases of catastrophic outages, Arc flashthat facility managers want to perform well when called upon. In cases of catastrophic outages, Arc flashconsiderations might take a back seat to keeping as much of the facility up and running as possible and only considerations might take a back seat to keeping as much of the facility up and running as possible and only Tripping CB’s closest to the fault.Tripping CB’s closest to the fault.

For more details on the ARC Flash concerns, and that whole side of the argument, please refer to your handout.For more details on the ARC Flash concerns, and that whole side of the argument, please refer to your handout.

UL 1008 Withstand TestUL 1008 Withstand Test

34.1 When tested under the conditions described in 34.2 – 34.15, 34.1 When tested under the conditions described in 34.2 – 34.15, a transfer switch shall a transfer switch shall withstand the designated levels of current until the over-current protective devices withstand the designated levels of current until the over-current protective devices open or for a timeopen or for a time as designated in 34.3. At the conclusion of the test: as designated in 34.3. At the conclusion of the test:a)a) The switch shall be capable of being operated by its intended means;The switch shall be capable of being operated by its intended means;b)b) The fuseThe fuse mentioned in 34.14 mentioned in 34.14 shall not openshall not open,,c)c) There shall be no breakage of the switch base to the extent that the integrity of the mounting There shall be no breakage of the switch base to the extent that the integrity of the mounting

of live parts is impairedof live parts is impaired,,d)d) The door shall be prevented by its latch, without bolt or lock installed therein, from being The door shall be prevented by its latch, without bolt or lock installed therein, from being

blown open, and deformation of the door alone is not determined to be unacceptable;blown open, and deformation of the door alone is not determined to be unacceptable;e)e) No conductor shall have pulled out of a terminalNo conductor shall have pulled out of a terminal connector and there is connector and there is no damage to the no damage to the

conductor insulation or the conductorconductor insulation or the conductor (see 41.56); and (see 41.56); andf)f) For a plug in or draw out unit, For a plug in or draw out unit, the point of contact is to be the same both mechanically and the point of contact is to be the same both mechanically and

electrically as before the test.electrically as before the test.

UL 1008 Closing TestUL 1008 Closing Test

36.1 When tested in accordance with 36.2, a transfer switch shall comply with the 36.1 When tested in accordance with 36.2, a transfer switch shall comply with the requirements in 34.1(a) –(f).requirements in 34.1(a) –(f).

36.1 Revised September 18, 199636.1 Revised September 18, 1996

36.2 The sample for this test is to be that used for the withstand test. Test 36.2 The sample for this test is to be that used for the withstand test. Test procedures and conditions for the closing test are to be as described in 34.3 – procedures and conditions for the closing test are to be as described in 34.3 – 34.19. 34.19. The switch is to be closed on the circuit.The switch is to be closed on the circuit.

36.3. The 36.3. The test test (for close on)(for close on) current shall be the same as current shall be the same as that used in the that used in the withstandwithstand

test.test.

UL 1008 Short Circuit Test HistoryUL 1008 Short Circuit Test History

• Around 1989 UL introduced an optional 3 cycle test for any over- current protection device.

Prior to this, manufactures could test with any over-current device.

If a manufacturer didn’t test to 3 cycles, they would be required provide a label that lists all breakers that the switch was “coordinated with”.

This requirement did not take into consideration air power circuit breakers APCB’s. Some of these breakers were 4-5 cycle devices (GE AKR and Westinghouse DS)

• January 9th, 2002 UL introduced an optional short time current rating test.

A withstand and a close and withstand test is required to get a UL short time rating.

This requirement did not take into consideration air power circuit This requirement did not take into consideration air power circuit breakers APCB’s. Some of these breakers were 4-5 cycle devices breakers APCB’s. Some of these breakers were 4-5 cycle devices (GE AKR and Westinghouse DS)(GE AKR and Westinghouse DS)

Overcurrent Protective DevicesOvercurrent Protective Devices

• Molded Case Circuit Breakers –MCCB (UL489)Molded Case Circuit Breakers –MCCB (UL489) May be Current Limiting to 200KAMay be Current Limiting to 200KA Long Time OvercurrentLong Time Overcurrent Instantaneous Interruption is less than 3 cyclesInstantaneous Interruption is less than 3 cycles

• Fuses and Fused DevicesFuses and Fused Devices Current LimitingCurrent Limiting Mostly used on 200KA circuitsMostly used on 200KA circuits

• Insulated Case Circuit Breakers -ICCB (UL489)Insulated Case Circuit Breakers -ICCB (UL489) May be Current Limiting to 200KAMay be Current Limiting to 200KA Instantaneous Interruption is typically less than 4 cycles Instantaneous Interruption is typically less than 4 cycles Short Time delay available (30 cycles) with Instantaneous over-rideShort Time delay available (30 cycles) with Instantaneous over-ride

• Low Voltage Air Power Circuit Breakers -APCB (UL1066)Low Voltage Air Power Circuit Breakers -APCB (UL1066) May be Current Limiting to 200KAMay be Current Limiting to 200KA Instantaneous Interruption is typically less than 4 cyclesInstantaneous Interruption is typically less than 4 cycles Short Time delay available (30 cycles) without Instantaneous Short Time delay available (30 cycles) without Instantaneous

Selective Coordination - GoodSelective Coordination - Good

No overlapping fault current of individual devices.

This is coordinated properly.

In a perfect world this is great.

Selective Coordination - BADSelective Coordination - BAD

In this case, since it takes 8 cycles for the upstream breaker to clear the fault, a 3 cycle rated transfer switch is inadequate.

ATS Feeder Breaker

8 cycles to clear

What is our Competition Doing?What is our Competition Doing?

ASCO

100-400a 100-400a 30k@30cycles30k@30cycles600-800a 600-800a 42k@30cycles42k@30cycles1000-1200a 1000-1200a 65k@30cycles65k@30cycles1600-3000a 1600-3000a 85k@30cycles85k@30cycles4000a* 4000a* 100k@30cycles100k@30cycles

* ATS only* ATS only

Short Time Close & Short Time Close & WithstandWithstand

8. With fuses only

Non UL

6

News regarding Cummins Power Generation

2009 News Releases June 12, 2009

Cummins Power Generation Transfer Switches First With UL-Listed 30 Cycle Ratings MINNEAPOLIS, MINNESOTA – Series OHPC and CHPC PowerCommand® automatic transfer switches from Cummins Power Generation Inc. are the industry's first transfer switches to achieve UL-listed 10-cycle and 30-cycle withstand and closing (short-time) ratings.

The OHPC open transition and CHPC closed transition switches demonstrated unprecedented short-time ratings of 25 kA at 10 cycles for 125 to 260-amp switches, 30 kA at 30 cycles for 300 to 600 amps, and 50 kA at 30 cycles for 800-amp switches in UL tests. The switches continued to operate safely at full load, even after testing.

The UL listing provides consulting and specifying engineers independent assurance that the OHPC and CHPC transfer switches offer the industry's highest performance level, particularly for standby power systems requiring selective coordination. As defined by the 2008 edition of the National Electrical Code (NEC), selective coordination is mandatory for emergency and legally required electrical systems in buildings where life safety is paramount, including hospitals, health care facilities, emergency shelters and high-rise buildings with multiple elevators. NEC 2008 also requires selective coordination for critical operation power systems (COPS) in secure buildings such as banks, data centers, embassies and government offices.

Selective coordination localizes an overcurrent condition to restrict outages to the circuit or equipment being affected. It is achieved by selecting circuit breakers and transfer switches with timing and withstand characteristics that delay or prevent faults from tripping upstream overcurrent protection devices. Selective coordination requirements are more easily satisfied by specifying OHPC or CHPC switches rather than products without UL-listed short-time ratings.

The ability of CHPC and OHPC transfer switches to withstand fault current for up to 30 electric cycles (one-half second) gives the consultant the flexibility to adjust the instantaneous time delay on the ATS overcurrent protection device to prevent upstream 2breakers from tripping unnecessarily. Both transfer switches feature Cummins Power Generation's innovative High Endurancehttp://www.cumminspower.com/en/about/news/2009/news-2009-9/ 8/12/2009

Page 2

Mechanism (HEM), designed to ride through a fault condition undamaged and retain its capability to carry 100 percent of the rated load. Magnetic forces developed during a fault cause a typical transfer switch's contacts to blow open, producing an electrical explosion that often results in extensive internal damage to the switch, requiring replacement of contacts, arc chutes and, in some cases, the controller.

In contrast, the HEM uses that same magnetic energy to hold the contacts closed during a fault, virtually eliminating arcing, contact damage and performance degradation. It can survive multiple faults of the specified magnitude - listed on the nameplate as the withstand and closing current ratings (WCR) - and continue to carry the rated current without overheating. This proprietary Cummins Power Generation technology means that there will be no costly repairs or inconvenient downtime after a fault.

"Cummins Power Generation is proud to be the first manufacturer of transfer switches proven to survive a fault condition and to continue to operate at full load without repair," said Rich Scroggins, ATS product manager of Cummins Power Generation. "This ability gives consulting engineers more design flexibility in addressing requirements, and potentially to lower costs by using fewer transfer switches.“ Underwriters Laboratories (UL) is a leading safety testing and certification organization that has conducted product safety testing for nearly 115 years. On electrical products, the UL mark designates products that have been certified for safety regarding foreseeable hazards that include electric shock, fire and mechanical hazards.

Although Cummins Power was first to the market with some sizes, this is all they’ve published so far.

PowerGeneration

Switch Current RatingsSwitch Current Ratings Short Time RatingsShort Time Ratings

Transfer Transfer SwitchesSwitches

Bypass Bypass SwitchesSwitches DurationDuration CyclesCycles

125-260a125-260a 125-260a125-260a 25 ka25 ka 1010

300-600a300-600a 300-600a300-600a 30 ka30 ka 3030

800a800a 800a800a 50 ka50 ka 3030

1000-4000a1000-4000a 1000-4000a1000-4000a

The OHPC open transition and CHPC closed transition switches demonstrated unprecedented short-time ratings of 25 kA at 10 cycles for 125 to 260-amp switches, 30 kA at 30 cycles for 300 to 600 amps, and 50 kA at 30 cycles for 800-amp switches in UL tests. The switches continued to operate safely at full load, even after testing.

100-400a 100-400a 30k@30cycles30k@30cycles600-800a 600-800a 42k@30cycles42k@30cycles1000-1200a 1000-1200a 65k@30cycles65k@30cycles1600-3000a 1600-3000a 85k@30cycles85k@30cycles4000a* 4000a* 100k@30cycles100k@30cycles

* ATS only* ATS only

Short TimeShort Time

No Mention in the press release of bypass switches

Only the 800awe don’t match

So we’ve distilled the info and put the values into a table.

EATON CUTLER HAMMEREATON CUTLER HAMMER

Magnum Circuit Magnum Circuit Breaker based transfer Breaker based transfer switches.switches.

First mention of 30 First mention of 30 cycle rating but only cycle rating but only when used with when used with upstream fuses ??upstream fuses ??

While inconclusive as While inconclusive as to whether these type to whether these type switches carry a UL switches carry a UL 30 cycle 30 cycle close and close and withstand ratingwithstand rating, it , it doesn’t seem as if doesn’t seem as if they do without the they do without the inclusion of upstream inclusion of upstream fuses. fuses.

G.E. ZenithG.E. Zenith

To Our Knowledge, they presently publish nothing otherTo Our Knowledge, they presently publish nothing other

than 3 cycle ratings.than 3 cycle ratings.

New Russelectric New Russelectric 30 Cycle Automatic Transfer Switches30 Cycle Automatic Transfer Switches

and Bypass Isolation Switchesand Bypass Isolation Switches

SIDE BARRIER:

-5/8” thk glass polyester

-Greater arc & track resistance

-Excellent flame resistance

-Movable contact support

BACKPLATE:

-increased thickness to 1.25”

-added strength and stability

Back Plate AssemblyBack Plate Assembly

Current Path

Movable Main Contact

Stationary Contact

Movable Arcing Contact

Blow Open Force

Movable and Arcing Contact Springs

Blow-Off Contact Design:- Used for Interrupting High Fault Currents- Magnetic forces push contacts open- Used for 3 cycle devices- Contact springs - only force to withstand fault

Contact Design: Blow-off vs. Blow-onContact Design: Blow-off vs. Blow-on

- Used for withstanding High Fault Currents- Magnetic forces from fault increase pressure on contacts - Offset hinge point allows for rotation toward contacts for blow on effect

Current Path

Contact SpringsHinge Point

Stationary Contact

Main Contact

Force

Contact Design: Blow-onContact Design: Blow-on

Contact Comparison: 3 Cycle vs. 30 Cycle

Russelectric 3 Cycle DesignRusselectric 3 Cycle Design

Blow-Off Design Single Arcing Contact Multiple Contact Fingers depending on

amperage Main Contact Pad material:

AgWC50 – Silver Tungsten Carbide

Tungsten to reduce erosion Arcing Pad Material:

AgW73 – Silver Tungsten Stationary Contact Pad material:

AgWC50 – Silver Tungsten Carbide Contacts Rotate on Copper Hinge

Block and Pin Assembly Metal Contact Holder

30 Cycle Design

Blow-On DesignBlow-On Design Arcing Contact Designed into each Arcing Contact Designed into each main contact – Coppermain contact – Copper Multiple Contact Fingers depending onMultiple Contact Fingers depending on amperageamperage Main Contact Pad material:Main Contact Pad material: AgWC40 – Higher Silver Contact to AgWC40 – Higher Silver Contact to prevent overheatingprevent overheating Stationary Contact Pad material:Stationary Contact Pad material: AgC4 – 96% Silver, graphite to AgC4 – 96% Silver, graphite to prevent welding during withstandprevent welding during withstand Flexible Braided connectors – Flexible Braided connectors – prevents overheating and hot spotsprevents overheating and hot spots Brush Movement in Main Contacts – Brush Movement in Main Contacts – Cleans contact pad every operationCleans contact pad every operation Molded Contact Holder Molded Contact Holder - Contains arc- Contains arc - BMC thermoset material- BMC thermoset material - Withstands heat- Withstands heat - Great arc and track resistance- Great arc and track resistance

CROSSARM MECHANISM

Made from 1.125 Square Steel StockMade from 1.125 Square Steel Stock Overcenter Spring Mechanism to Latch Contacts Closed and OpenOvercenter Spring Mechanism to Latch Contacts Closed and Open

Utilizes same mechanics as the 3 cycle switch – Heavier springUtilizes same mechanics as the 3 cycle switch – Heavier spring

OPERATORS

•Open Transition Switches with EMO

•Reliability of Motor Operators

Removal of Isolation Handle

Single Handle is for Bypass Operation

800A Rollout Switch

Cradle rolls out on Ground – not on rails

Gearbox Rack-in Mechanism

Access Rack-in Shaft through door - only in Bypass Mode

Position Indicator Window

- Connected

- Connected – Bypassed

- Test

- Isolated

Gearbox needed for Increased Spring Pressure

- Must Pass the “Liz Test”

Secondary Disconnect

•Located on left Side of Cubicle for accessibility

•Allows for Test Position

•Incorporated into Side Guide-Rail

Guide Plates

Used for Left to Right Alignment

Prevents Rollout Switch from jumping or shifting during fault

Shutter Design (Optional)

Shutter Open (switch racked-in) Shutter Closed (switch in test position or isolated)

Finger Clusters

2500A Cluster 800A Cluster

Added Spring Pressure for Clamping

Increased Contact Surface Area

Withstood 100KA for 3 Cycles and 85KA for 30 Cycles - without a scratch