Emergency Power Systems Scott Thomas Director - Application - PowerPoint PPT Presentation

Emergency Power Systems Scott Thomas Director - Application Engineering Cummins Southern Plains

Agenda  Generator Application Considerations – Ratings – Diesel vs Natural Gas – Common Design Challenges • Packaging – Enclosures and Fuel Tanks – Emissions – Common Generator Failures – Maintenance Recommendations  Automatic Transfer Switches – Basic Functionality – Open and Closed Transition – ATS Types  Question and Answer

Generator Ratings

Definitions  ISO 8528-1 Sect. 13 defines these ratings:  Emergency Standby power (ESP)  Limited Time Prime Power (LTP)  Unlimited Time Prime Power (PRP)  Continuous Operating Power (COP)  Any manufacturer can go above and beyond the ISO ratings definitions

Rating Example 2750kW DQLF  Standby rating 2750 kW  Max avg. load in 24h period (70%) : 1925 kW  200h/year  Limited Time Prime Power 2500 kW  Max load is (100%) : 2500 kW  500h/year with constant load  Unlimited Time Prime Power Rating 2500 kW  Max avg. load in 24h period (70%) : 1750 kW  Unlimited Hours with Variable Load  Continuous Operating Power 2100 kW  Max load is (100%) : 2100 kW  Unlimited Hours with Constant Load

Fuel Selection Diesel Generators  Local Fuel Source  Better Transient Response  Lower Cost >150 kW Natural Gas Generators  Unlimited Fuel Source – Outage Risk?  Slight Cost advantage <150 kW  Larger Footprint >150 kW  Emissions

Common Design Challenges  Sound – Contact city to verify sound requirement at property line  Fuel Tanks – Contact Fire Marshall for fuel storage requirements  Clearances – Recirculation of radiator discharge air – Proximity to ATS - Transformer  Natural gas supply piping  Generator Sizing – Fire Pumps – WWTP/LS/PS – VFD’s - Harmonics Cummins Confidential

Sound Attenuation

Sources of Sound – Engine noise • 100 -110dB(A)@1m – Cooling fan noise • 100-105dB(A)@1m – Alternator noise • 80 – 90dB(A)@1m – Structural/mechanical noise • Vibration, Gears etc. – Un-silenced engine exhaust • 120-130dB(A)@1m

Sound Attenuation Strategies  Contact City to understand local requirement based on zoning of property – field testing requirements.  Increase distance from receiver (Property Line) – Sound pressure drops ~6 dBA at 2x distance  Insert high mass, absorptive barriers – Enclosure Baffles  Watch for reflective surfaces – Perceived sound pressure increases 3dBA due to a reflective surface; 5dBA for two reflective surfaces  Direct noise away from sensitive locations – Radiator discharge turning vanes (Scoop) – Engine Exhaust elbows

Sound Attenuation Strategies

Sound Attenuation Strategies

Installation Review: Airflow Restriction

Installation Review: Airflow Restriction

Installation Review: Airflow Restriction

Installation Review: Accessibility

Location Considerations: Outdoor  Ease of Access – Fuel Fill – Load Bank Connections  Weather Events – Snow Loading / Plowing – Flood Plain  Proximity to Occupied Facilities – Windows/Doors – Ventilation Intakes

Location Considerations: Indoor  Safety – Dedicated space – Working space (36” or 1 m minimum) – Working height  Future Planning – Additional equipment space – Future genset capacity – Replacement parts access

Diesel Fuel Systems

Diesel Fuel Tanks  Tank size – Contact Fire Marshall for volume, tank construction expectations, and field testing requirements – Access and filling for rooftop installations – Actual run time required/desired  Fuel temperature concerns – Cold - Waxing point of particular diesel blend on-site – Warm – Fuel return temperature in small tanks  Tank ventilation (Discharge to exterior)  Special requirements for onsite testing, alarms, remote fill stations

Diesel Fuel Tank Notes  UL 142 and UL 2085 listing requires pressure/leak testing prior to shipment  Common Options: – Overfill protection valves (OFPV) – Spillboxes – Fuel level alarms – Polishing systems – Remote Fill Stations – Elevated Vents  Be weary of additional control/breaker handle height with subbase tanks

Day Tank Notes  2 to 4 hour run time  One day tank for each generator set  As close to the generator set as possible  Automatic filling control  Ability to return fuel back to bulk tank – Auxiliary pump or gravity return  Manual filling provision Options: – Utilize genset subbase tank with additional ports – Standalone day tank from 3 rd party supplier

Diesel Fuel System Piping  Size Lines for Flow, NOT Consumption  Route for Lowest Restriction – Limit fittings, bends, and length of runs

EPA Emissions Tables

 CI NSPS Stationary Emissions - Diesel engines

EPA SI NSPS Final Rule

Stationary Emergency Engine Designated Use for NSPS and RICE NESHAP  Unlimited use during emergencies – Utility failure, transformer, UPS, circuit breaker, ATS – Document issue as a part of record keeping requirement  100 hours per year allowed for: – Maintenance and testing – Emergency Demand Response (EDR) programs (May 1 st 2016 EDR Revision) – 50 hrs/year (of the 100hrs/yr) for non-emergency operation allowed (if there is no financial arrangement*) • e.g.: storm avoidance

Generator Maintenance

Common Generator Failures – Dead Batteries (Redundant Battery String & BBS) – Battery Charger Failure (Redundant Battery String & BBS) – Fuel Quality (Fuel Filtration Systems, Fuel Maintenance Program) – Low Coolant Levels (Periodic Inspection – Alarm) – Control not in Auto (Remote Annunciator – SCADA Alarm) – Circuit Breaker Open (Remote Annunciator – SCADA Alarm)

Maintenance Recommendations  Cummins recommendations for Annual Maintenance – Quarterly Inspections – Annual Oil/Filter Change – Annual Supplemental Load Bank Testing • In addition to any building load tests throughout the year. – Battery Replacement • Per NFPA 110, batteries to be replaced in standby generator sets every two years. – Annual Fluid Sampling • Fuel/Oil/Coolant Analysis – ATS Inspections • Operate with load at least once per year

What is a Transfer Switch?  A device that transfers electrical loads between two sources of power by using either automatic or manual  Transfer switch controls  ATS monitors utility voltage and frequency  On utility failure generator starts and accelerates to rated speed and voltage  ATS senses source available  Utility  Generator  Time delay on transfer

Transition Types and Applications  Open Transition (In Phase or Time delayed / Programmed Transfer)  Closed Transition

Open Transition – Utility to Genset  From Utility Power  Utility Fails Generator Starts  ! Gen Source  To Loads Available Load Transfers to Generator

Open Transition – Genset to Utility  From Utility Power  Utility Returns ATS retransfers load to Utility ATS removes gen  To Loads run command  !

Time Delayed Transition From Utility To Loads Utility/Genset Voltage Load (Residual) Voltage

Time Delayed Transition UTILITY UTILITY UTILITY INDUCTIVE INDUCTIVE INDUCTIVE LOAD LOAD LOAD LOAD VOLTAGE TIME Pre-determined delay allows the residual voltage to decay

Closed Transition From Utility To Loads

Full power outage cycle (utility drops out) UTILITY UTILITY UTILITY LOAD LOAD LOAD LOAD VOLTAGE TIME Up to 10s of power interruption

Return to Normal Power (After Outage) UTILITY UTILITY UTILITY LOAD LOAD LOAD LOAD VOLTAGE TIME Up to 100ms of paralleled operation

Closed Transition Risks  Why do breakers trip during closed transition transfer? – Current flow between sources caused by a difference in instantaneous voltage between sources at the instant of closure  What causes the difference in voltage? – Phase angle difference between sources – Difference in RMS voltage between sources – Transient condition on one of the sources • Motor stops/starts • VFD ramps/down

Closed Transition Considerations  Closed Transition is not a substitute for a UPS  Closed Transition might result in disturbances on transfer – Frequency and Voltage shift due to less than perfect synchronization – Current spike may result due to voltage difference – Disturbances minimized by Load sequencing  Closed transition adds cost due to requirements for protective relays  Closed transition systems can result in project delays due to additional utility regulations

Bypass Isolation Switches  Allows service of ATS without disrupting power to critical loads.  By having two transfer switches connected in parallel, the bypass transfer switch adds redundancy to the system  Applications: – Critical power and maintenance requirements, including data centers,health care, and waste water treatment facilities

Bypass Transition Switch ATS Bypass N L E