Uninterruptible Power Supply Improves Reliability at The Australian Synchrotron Sean Murphy – ARW 2013 Melbourne

Introduction Background of the project Look at the power interruptions to blame The causes of power interruptions UPS technical requirements Design, efficiency, and autonomy of the UPS Practical implementation and installation The improvements to power reliability

Background The Australian Synchrotron is expected to operate continuously 24 hours per day, 7 days per week (approximately 5,000 User Beam Hours per year) The mean time between failures (MTBF) for power interruptions was approximately 150 hours prior to the installation of the UPS systems. Power reliability was to blame for approximately 35% of all down time. 3 systems that are particularly sensitive to power disturbances include the storage ring magnets, the storage ring RF, and the mechanical plant. A voltage fluctuation of greater than ±5% from the 240V nominal for 10 cycles (200ms at 50Hz mains) can cause either of these systems to enter a fault condition, losing the stored beam. An uninterruptible power supply (UPS) was a strong solution to provide adequate power conditioning

Power Interruptions Example of a site feed voltage sag: No interruption longer than 2 seconds has occurred

Power Interruptions The Synchrotron site is supplied by two dedicated underground 22kV feeders from Zone substations SV (Springvale) and SVW (Springvale West). The Synchrotron site feeders are SV19 and SVW44 and both are 2.8km in length.

Power Interruptions All disturbances are within the limits allowed by the distribution code

Power Interruptions Information Technology Industry Council (ITIC) Curve and Victorian Distribution Code

Power Interruptions Interruptions when compared with the ITIC curve:

Causes Known faults at 66kV and 22kV as well as unknown causes. Common voltage sags are caused by network operations (switching, capacitor banks) and other customers (motors starting and equipment failures).

Causes Other causes include trees, possums, fires, etc.

UPS Requirements The UPS system ratings needed to cover the storage ring critical loads in order to ride through power interruptions. The design loads were specified: TransformerLoadApparent Power Active PowerPower Factor Tx2Mechanical Plant 1,700kVA1615kW0.95 Tx4Storage Ring RF 1,200kVA1140kW0.95 Tx6Storage Ring Magnets 1,400kVA1330kW0.95 Total4,300kVA4085kW0.95

UPS Requirements Flywheel rotary UPS systems provide very high output current compared to purely electronic UPS systems, and are able to provide inrush current for inductive loads, and large loads such as magnet power supplies. In addition they can provide 14 times rated current under short circuit in order to clear faults on downstream circuit protection. Rotary systems that don’t use batteries have a year lifecycle, which suits the operating life of the Australian Synchrotron Only short-term ride through of at least 2 seconds is required due to the network supply reliability. Rotary systems are on-line, and this is important as one cannot predict when a power interruption will occur when using a standby off-line system

UPS Requirements The UPS systems are installed between the existing transformer secondary windings and the main circuit breakers of the low voltage switch boards.

The UPS Design Flywheel Energy Storage Converter Bridge Motor/Generator Coupling Choke Load

The UPS Design 6000kg steel disc rotates at 55Hz mechanical frequency (3300rpm) on a 4- pole motor/generator Flywheel lifted by a magnetic bearing to reduce wear on the mechanical bearings Flywheel is encased inside a positive pressure helium vessel which reduces friction and is less prone to problems that vacuum systems have Energy storage is approximately 15.7MJ Generates electricity at 110Hz down to 50Hz electrical frequency. This is equivalent to 55Hz – 25Hz mechanical frequency (3300rpm – 1500rpm) Generated electricity is converted via SCR bridges to drive the output motor/generator at 50Hz ± 1Hz continuously until the flywheel is discharged. Motor/Generator runs at 25Hz (1500rpm, 4-pole) for 50Hz mains output

UPS Efficiency UPS efficiency is approximately = 93.6% Cooling is required to keep the system below 30°C Total UPS losses UPS SystemAverage LoadAverage Losses Site Feed UPS Tx kW kW Site Feed UPS Tx kW49.077kW Site Feed UPS Tx kW kW Total: kW

UPS Autonomy Typical active power demands: Tx6: kW Tx4: kW Tx2: kW This typically allows over 14 seconds autonomy on all systems UPS SystemPeak LoadMinimum Autonomy Time UPS TR21615kW8 seconds UPS TR41140kW14.8 seconds UPS TR61330kW12.75 seconds

Implementation Main Building & LV Room – HV Room – UPS Building

Implementation The UPS systems installed inside the UPS building

Implementation Cables to the 2000kVA unit required 5 X 500mm2 cross sectional copper conductor area per phase plus neutral (20 cables)

Implementation UPS systems must be kept below 30°C and dust free with a 200kW capacity air handling unit. Springs suspension for isolating 25Hz and 55Hz mechanical vibrations from the technical floor / beamlines was necessary.

Improvements to reliability No more outages to the storage ring due to brief electrical interruptions. The percentage of faults due to power decreased for 35% to 5% after the UPS was commissioned. 5% during 2012 was due to on site electrical faults YearFacility MTBF (hours) Power MTBF (hours) % of faults due to power % % % UPS COMMISSIONED DECEMBER %

Conclusion and Further Improvements The UPS was effective at improving power reliability and beam availability at the Australian Synchrotron. Installation of the Tx3 LINAC load of 124kW on to the Tx4 UPS system will be possible in May.

The end Any Questions?