High Voltage Padmount
PTI's high voltage padmount transformer, (66kV HV Padmount shown), is suitable for serving distribution loads directly from 46kV and higher sub-transmission systems. This patented design enables Utilities to service customers at voltages at or above 46kV at substantially less cost than building new distribution stations. The concept eliminates the need for station structures and fenced switchyards and so provides considerable savings in construction and maintenance costs. This style of station, That is being refered to as a Distribution Supply Centre or DSC, has now been incorporated in a number of applications.
Since the HV Padmount offers an underground option for connecting a high voltage transformer into the system, customers can be served at a significant cost saving when compared to building aconventional distribution sub-station. Often the only overhead electrical structures are the HV cable and switch poles. There is otherwise no other structure required. This allows for total flexibility when it comes to land and placement.
Ideally, the transformer is specified such that it can be shipped completely assembled on a standard step-deck trailer. This eliminates the need for onsite transformer assembling and oil processing. Installation or removal is easy as the design allows both HV and LV cable terminations to be pre-installed or left in place. Sizes are available in the standard configuration to 10 MVA at 138 kV, 650BIL. Designs have successfully passed short circuit testing. See the list of these designs at the bottom of this page.
High Voltage; Low Maintenance
Range: 1500 kVA to 15 MVA
Primary Voltage: Up to 138 kV Class*
Secondary Voltage: 5 to 34.5 kV*
* dual voltage configurations are also available
Contact PTI for other options
The HV Padmount uses sealed tank construction with a blanket of dry nitrogen above the oil. Standard designs are rated ONAN only. The HV Padmount is designed to require minimal maintenance. Basic condition monitoring and periodic visual inspection of the unit and gauges are recommended.
Safe to the Public; Safe from the Public
In a tamperproof enclosure, the HV Padmount incorporates dead-front HV and LV technologies. There is little danger for damage due to the elements, humans and wildlife. The public is also protected without the need for fencing, provided appropriate grounding designs meeting the requirements of IEEE 80 with respect to step and touch potential are installed. The placement of all grounding conductors, either inside compartments or underground, greatly reduces the probabilities of copper theft.
Also, very recent developments with respect to HV current limiting fuses reduce probability of eventful failure (contact PTI for more informaton).
Maximized Efficiency; Minimized Footprint
A Distribution Supply Centre includes:
- a high voltage pole mounted switch
- a high voltage fuse & arresters on a pole structure
- cable & terminations (often combined with fuses and arresters on the same pole)
- HV Padmount Transformer
- a padmounted distribution multiple circuit switching cubicle
- padmounted circuit reclosers/breakers
- padmounted single or three phase station transformer
- padmounted regulators, and other auxiliary equipment as required
Combined with other pad-mounted distribution devices, the DSC eliminates the need for a large station structure, station yard and fence. The compact modular design allows the DSC to be accomodated in spaces as small as a one, or two residential lots.
Back to the Future
With rising property costs, utilities have turned to fewer, larger stations with longer feeders. They often require capacitors and regulators for voltage support. The processes of design, approval and installation are lengthy with costs escalating over time. This however has come at the cost of greater voltage drop, more losses, increased installed capacity and considerable plant and planning for the future.
The DSC reverses these trends utilizing instead small and inexpensive installations that fit in minimal spaces close to load centres. Shorter feeders minimize voltage drop, losses, and increases reliability.
Many Applications
The flexibility offered by the HV Padmount Transformer and the associated Distribution Supply Centre has resulted in a growing repertoire of applications. The initial concept of a low cost rural station has been successfully extended to include applications such as rotten wood pole station replacement, direct customer supply, system VAR support, existing station load support, urban residential distribution supply, low noise settings, mining, wind farm stations, etc.
Short-Circuit Tested
Short-Circuit Withstand Testing has successfully been carried out on the following rated HV Padmount Transformers manufactured by PTI. The tests were performed in accordance with IEEE C57.12.00-2000 and C57.12.90-1999. The transformers complied with the series of relevant short-circuit applications. The tests verified the transformer design and construction withstand mechanical and thermal stresses produced under external short-circuit conditions.
Summary Information:
KEMA Laboratories - April 2003
Rating: Three-Phase, 5000 kVA - 60 Hz, 66,000v Delta - 12,470v Y
PowerTech Labs - September 2006
Rating: Three-Phase, 10 MVA - 60 Hz, 66,000v Delta - 24,000v Zig-Zag
KEMA Laboratories - January 2009
Rating: Three-Phase, 10 MVA - 60 Hz, 115,000v Delta - 12,470v Zig-Zag