Circuit Breakers and Switchgear. Thomas Greer Director of Engineering TLG Services

Transcription

1 Circuit Breakers and Switchgear Thomas Greer Director of Engineering TLG Services

2 Presentation Outline Switchgear Definition Overcurrent Protection Devices Circuit Breaker Trip Curves and Coordination Panelboard Switchboard Switchgear Maintenance Bypass Configurations and Applications

3 What is Switchgear? IEEE defines switchgear as: A general term covering switching and interrupting devices and their combination with associated control, instruments, metering, protective, and regulating devices; also assemblies of these devices with associated interconnections, accessories, and supporting structures used primarily in connection with the generation, transmission and conversion of electric power. The primary functions of UPS switchgear is: Circuit switching Short-circuit protection Over-current protection

4 Switching and Overcurrent Protection Devices Types Switches Disconnect Only - No Overcurrent Protection Fuses Cheap / Easy Replacement Successful Operation = Destruction Circuit Breakers More Expensive Than Fuses Designed for Repeated Operation

5 Circuit Breakers

6 Circuit Breakers Basic Types Molded-Case / Insulated Case Circuit Breakers UL489 (for Switchboards and Panelboards) 80% rated - Molded Case Typically Rated up to 1200A 100% rated Insulated Case - Rated A Low Voltage Power Circuit Breakers- LVPCB UL1066 (for Metal Clad Switchgear) 100% Rated

7 Molded Case Circuit Breakers Fixed Mounted Toggle Open-Close Operation

8 Molded Case Circuit Breakers Features Ampere Ratings Typically 3A A Typically 80% Rated Continuous Current Not To Exceed 80% Of Nameplate Usually Fixed Mounted Toggle Handle for Manual Operation Thermal Magnetic Fixed Trip Most Common Magnetic Instantaneous Trip Designed for Quick Interruption / Limited Withstand Duration Minimal Maintenance Capabilities

9 Insulated Case Circuit Breakers Drawout PowerBreak II Easy Inspection and Maintenance of Primary Contact Finger Assembly on Drawout Breakers

10 Insulated Case Circuit Breakers Features Tested and Listed to UL 489 Ampere Ratings up to 4000A Can be either Drawout or Stationary Two Step Stored Energy Mechanism Can be electrically operated Solid State Trip Units Most Common Low to No Maintenance Usually rated for 10,000 Operations

11 Low Voltage Power Circuit Breakers GE WavePro LVPCB SqD Masterpact NW and NT LVPCB

12 Low Voltage Power Circuit Breakers LVPCB (aka - Iron Frame Breaker or Air Breaker) Tested and listed to UL1066 Available in sizes up to 5000A Insulated Case Type or Traditional Iron Frame Construction Old Style Iron Frame Requires Maintenance and can be Rebuilt Inspection every 100 to 200 Operations Replacement of Contacts every 300 to 1000 Operations Newer Style Enclosed Have Maintainable Arc Chutes and Contacts Two Step Stored Energy Mechanism Trip units are typically electronic with selectable time current curve characteristics Higher Short Time Ratings

13 Available Trip Units for Circuit Breakers Thermal Magnetic Long-Time Overload Trip Bi-Metallic Strip Magnetic Instantaneous Solenoid Response to High Current Setting Self-Protection Feature Ground Fault Interrupt Current Summing CT Solid State Long Time Setting / Delay Short Time Setting / Delay Instantaneous Setting / Delay Ground Fault Setting / Delay

14 Why The Different Types?? Various Breaker And Trip Types Designed For Optimum User Flexibility In Designing The Power Distribution System. The Secret To Success In Designing Power Distribution Is,. Coordination... Coordination...»COORDINATION!!!!!

15 Selective Coordination Selective coordination is the process of localizing a fault to the overcurrent device closest to the fault. X Branch Device Opens Fault

16 Reading a Trip Curve Graphic representation Tripping time vs. Current level Shaded area -- possible trip Manufacturing tolerances Time in Seconds Header Multiples of Rated Current 100

17 Thermal Tripping Bi-metallic element responds to heat generated by the overcurrent Shown in the upper left portion of the trip curve Overload currents (1X to 6X) Inverse time - larger overcurrent opens the circuit breaker faster Time in Seconds Thermal Multiples of Rated Current

18 Instantaneous (Magnetic) Tripping Magnetic assembly responds to the current flow through the circuit breaker Shown in lower right portion of trip curve High level overcurrents (5x - 10x handle rating or higher) Trips instantaneously - no intentional time delay Time in Seconds Magnetic Multiples of Rated Current

19 Electronic Tripping Utilizes a trip solenoid Different tripping characteristics achieved by adjustment of trip unit functions Time in Seconds Long-time Pickup Long-time Delay Short-time Pickup Short-time Delay (I 2 T IN) I 2 T OUT Instantaneous Multiples of Rated Current

20 Trip Unit PE Circuit breaker LSIG 1200 and 1600 ampere Sensor

21 Square D MICROLOGIC Trip Units Standard Trip Unit LI, LSI Ampmeter Trip Unit (A) LI, LSI, and LSIG Power Trip Unit (P) LSI, LSIG/A Harmonic Trip Unit (H) LSI, LSIG/A

22 Where Are The Breakers Housed? Panelboards Switchboards Switchgear

23 Panelboards Front Cover Removed

24 Panelboards According to the NEC (NFPA 70), panel boards are: Used to control light, heat, or power circuits Placed in a cabinet or cutout box Mounted in or against a wall Accessible only from the front

25 Switchboards W/ FIXED MOLDED CASE BREAKERS W/ DRAW-OUT ICCB CIRCUIT BREAKERS REAR CONNECT D

26 Switchboard Construction UL Switchboard Referenced Standards: Enclosure: UL 891, NEMA PB-2 Stand-Alone Enclosure Design Available in front access only or front and rear access Construction with internal barriers between devices and bussing or control circuit is optional Can Utilize Molded Case, Insulated Case, and LVPCB s Fixed-Mounted / Plug-In / Draw-Out Device Options Front Accessible for Fixed Mounted / Plug-In Devices

27 Switchgear

28 Typical UPS Integral Switchgear Lineup

29 Switchgear Construction UL Switchgear Referenced Standards: Enclosure: ANSI C , UL 1558, NEMA SG5 Circuit Breakers: ANSI C37.13, UL1066 Stand-Alone Enclosure Design Generally Higher Amperage Low Voltage Power Circuit Breakers Only Rear access always required for installation and service Bus Bar Runbacks Breakers fully compartmentalized with barriers

30 Switchgear vs. Switchboard Selection of switchgear or switchboard is a function of the following: Application type: Switchgear used mostly for service entrance / substation Switchboard used mostly for load distribution, close to load Switchboard: More prevalent in lower amperage Lower short circuit current availability Load distribution / maintenance bypass applications Switchgear: Typically more costly Rear access requirement

31 Basic Switchgear Configurations & Uses Maintenance Bypass Load Distribution Power-Tie Integral System Control and STS

32 Maintenance Bypass Configurations

33 What is a Maintenance Bypass?? Intended to be a path for power to the critical load, wrapping around UPS components for maintenance purposes. Important considerations: Is There an Input / Output Voltage Phase Shift? Can The UPS Be Tested? Overcurrent Protection? What Is Your Competition Quoting?

34 Maintenance Bypass Configurations 2-Breaker maintenance bypass configuration. Normal operation MBB is OPEN and MIB is closed. Input feed must be the same as the UPS static bypass feed. Three (3) input feeds for dual input UPS. Be wary of single input UPSs - PHASE SHIFTS!!

35 2-Breaker Maintenance Bypass GOTCHA!!! 2-Breaker maintenance bypass with D or E version of the Npower UPS. UPS has a 30 degree phase shift from input to output. Feed through the maintenance bypass will be out of phase from the UPS output. Always verify that the UPS output will be in phase with the maintenance bypass utility feed!!!

36 Maintenance Bypass Configurations 3-Breaker maintenance bypass configuration. Most commonly used. Two (2) input feeders for a dual input UPS. Always know if bypass power is available For single input UPS BIB breaker must be sized for UPS input current.

37 Sample UPS System with 3-Breaker Maintenance Bypass

38 Maintenance Bypass Configurations 4-Breaker maintenance bypass configuration Option for dual input UPS only. One (1) feeder for a dual input UPS. No feeder redundancy RIB sized according to UPS AC input current demand

39 Sizing Maintenance Bypass For Single Module UPSs (SMSs) Normally Based On 80% Rated Devices (NFLA x 1.25) + (MA - NFLA) = Target Device Rating For Breaker Feeding UPS Rectifier (NFLA x 1.25) = Target Device Rating For Breaker Feeding UPS Bypass Or Output Breaker Information Required From Site Planning Document NFLA = UPS Normal Full Load Current NFLA = Rectifier Input Current for AC Input Device; Bypass or Output Current for Device Feeding UPS Bypass or Serving as Output Overcurrent Device. MA = Maximum Input Current MA = UPS Input Full Load Current PLUS Maximum Battery Recharge Current

40 Solenoid Key Interlock System Interlock System for maintenance bypass arrangements. Enforces proper transfer sequence between UPS output and maintenance bypass source. Prevents UPS inverter from being paralleled with the bypass utility source. Will not prevent load dump.

41 Solenoid Key Interlock System Includes the following components: Kirk Key locks on MIB and MBB breakers Solenoid Key Release Unit (SKRU) Communication interface kit required on most UPS modules to communicate to the SKRU if the UPS is in the proper mode to allow transfer to or from maintenance bypass. Key is held captive in the SKRU until a permissive signal received from UPS. Transfer procedures are provided on the bypass assembly to inform the user how to accomplish the transfers.

42 Load Bank Breaker Load Bank Breaker Option Bussed off UPS side of MIB breaker. Sometimes interlocked with MIB. Used for battery and UPS load testing. UPS static bypass can t be tested when used with a 3- breaker MBP.

43 Load Distribution Option Load Distribution Breaker Option Individual circuit breakers provided in lieu of a single main lug output. Limited space available in Liebert matching maintenance bypass cabinets.

44 EPO Option Emergency power off option for maintenance bypass. Guarantees power shut down under all conditions. Includes shunt trips on MIB and MBB breakers

45 Maintenance Bypass Summary Totally isolate the UPS cabinet for maintenance ~ Know the available feeders for the UPS system ~ Recommend interlock options ~ EPO requirement ~ Load bank breaker option ~ Load distribution option~