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What is Power Quality?
- 10. Service Entrance Gear Utility Source A B C fault
- 14. Source: EPRI, An Assessment of Distribution System Power Quality, Vol. 2: Statistical Summary Report. Palo Alto, CA. EPRI TR-106294-V2 (May 1996)
- 16. Device % Nominal Voltage Ride-Through Time Contactors 43-49% 2 cycles Relays 78% < 1 cycle DC Power Supplies 70% 9.2 cycles PLC’s 47% 37 cycles Regulating Ballasts 65% Varies ASD’s 70% 2 cycles
- 20. Device Possible Solution Result Contactors & Relays Hold-in Circuit Improved performance up to 75% Sags PLC’s PQ Resistant Programming Improved performance up to protection limits ASD Local Ride-Thru Device Improved performance up to 60 % Sags UPS Local Ride-Thru Device Full sag protection
- 21. One PD for each XFMR One PD for 3 XFRM’s A B C fault
- 24. Critical Load Utility Input Output Input Bypass PES Isolation transformer Up to (4) power modules System control AC caps Battery Battery charger AC inverter
- 25. Voltage Sag red = supply voltage; blue = load voltage
- 26. Critical load Output Input Bypass Main container Isolation transformer Up to (8) power modules Battery New or existing back-up generator system Utility input AC gen Diesel, Natural Gas or Turbine Engine Diesel engine Power- Electronic Switch Battery charger AC inverter System control AC caps Transfer switch
Notas do Editor
- The average power quality in the U.S. was documented in a two-year (1995-1996) study by the Electric Power Research Institute (EPRI). This histogram shows the statistical average performance a user can expect. It shows the average monthly number of events, in terms of voltage sags and outages. As you can see, most sites can expect at least one disruption of some type every few months. The solutions that we will discuss can protect critical loads from all the events noted.
- Metal-enclosed switchgear allows protection of each individual circuit instead of group protection.
- Metal-enclosed switchgear allows protection of each individual circuit instead of group protection.
- These small units come in four sizes as shown on the previous slide. This shows the single-line diagram for a 1250 kVA system at 480 volts. In this example, the PES and circuit breakers are rated at 1,600 amps.
- This graph shows an actual 25% sag in utility voltage being corrected by the PureWave UPS.
- The system can be combined with a new or existing generator to make a “seamless” power system. When combined with a backup generator, the PureWave UPS will ride-through sags and very short outages ( up to 2 seconds) without sending a signal to start the generator. Once the outage exceeds 2 seconds, the start command is sent to the generator, the generator reaches rated speed in about 6-10 seconds, and the transfer switch “transfers” to the generator position. The PureWave “sync” to the generator and ramps the critical load over to the generator in a “soft load” method. A typical diesel generator can accept load at about one megawatt every 3 seconds. Therefore, total transfer of a two megawatt system load from outage to running on a generator takes about 15 seconds .
- Switchgear Options by S&C Electric Company 05/10/11 Presented to Tri-City Electric on February 17, 2005