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May 31, 2004 Provided by System Dynamics Inc.

BPL Part 3: Main.net BPL in Manassas

We visited Manassas a week after the PLCA conference to meet with Joe Marsilli of Main.net and John Hewa of the City of Manassas.


Main.net Communications

Joe Marsilli, the CEO of Main.net Communications, is an engineer with many years of experience in the power industry. He characterized himself--rather proudly--as a DOUG: "dumb old utility guy".

Joe said that most electrical utilities had long ago deployed communications technology to monitor and control their electrical grids. These early systems operated at low speed, and typically used some form of wireless or PLC technology. With the recent outages indicating the need for tighter grid control, state regulators are putting pressure on the utilities to upgrade these old systems to improve the reliability of the grid. With a projected BPL capital and installation expense of $65 to $75 per home passed, most utilities could justify the installation of BPL for internal use.

Main.net calls its BPL product the PLUS system. Joe described it as organized into a cellular structure with a backhaul network and three main BPL components:

  • The backhaul network--fiber in Manassas; T1 or wireless in other installations--connects each cell to the network center. Many vendors provide various forms of backhaul networks, and many utilities already have at least part of these networks in place to support internal applications.
  • The center of each cell is a Main.net CuPLUS concentrator, typically mounted at a transformer. The CuPLUS is connected to the backhaul network and to the medium voltage grid.
  • RpPLUS repeater units are deployed along the grid to carry the BPL signals between the concentrator and individual homes. At each transformer, the Rp unit is connected on the medium voltage side, and plays a dual role: amplifying and repeating the signal along the medium voltage line toward the next transformer, and transmitting through the transformer to the low voltage side connected to subscriber homes. Rp units are also used on the "low voltage" side if necessary to provide sufficient signal strength for the homes.
  • NtPLUS "network termination" units plug into electrical outlets in each subscriber home. Each NtPLUS communicates through one or more RpPLUS repeaters to the concentrator, which in turn communicates over the backhaul to the network center.

The CuPLUS and RpPLUS units connect to the electrical grid with inductive couplers that sit on the medium voltage and low voltage wires. Main.net has couplers for both overhead and underground wiring.

Main.net has what it says is a unique MAC structure designed specifically for BPL. This is based on the concept of "smart repetition" in which signals are repeated only if necessary. Repetitions are dynamically adjusted on a "least cost routing" basis to suit the current conditions on the electrical grid.

Because of the unique nature of Main.net's technology, all components of its system, including the NtPLUS consumer home device, are proprietary.

At the network center, Main.net provides the NmPLUS network management system. This includes tools to monitor and manage all components in the PLUS system.

Main.net has deployed two generations of technology, with a third in the works. The original "G1" technology operates with Direct Sequence Spread Spectrum using a high degree of redundancy for reliability; it operates at up to 1.8 Mbps and can deliver typical end-user services at 400 kbps. The new "G2" technology uses OFDM with only a single copy of data transmitted at a time - this provides a five-time improvement in typical end-user speed.


Manassas Deployment

John Hewa, Assistant Director, Electric Utility for the City of Manassas, is an engineer with 10 years prior experience at another municipally-owned utility before coming to Manassas.

He said that Manassas had previously deployed more than 60 miles of fiber for monitoring and to provide telecommunications services for the city. For the BPL rollout, an additional 20 miles of fiber were being deployed.

In Manassas, each Main.net Cu concentrator is co-located with a distribution switch; the technology permits an 8000 foot wire reach from each Cu with repetition as necessary. The additional fiber was planned to optimize the location of the concentrators to create cells reaching every home in the city. Medium voltage Rp repeaters are installed in every transformer. Instead of deploying low-voltage repeaters in advance, they are installed in hand boxes and meter bases upon receipt of a customer order. The pilot deployment was completed without expanding the utility workforce, and they plan to maintain the current headcount throughout the deployment.

To follow up on the "developer model" Alan Todd had described in the PLCA meeting (see above), John explained the division of responsibility between the city and the franchisee. The franchisee will provide all of the equipment. The city will install the Cu and Rp equipment on the medium and low voltage grid, and will install repeaters as needed on the bases of electric meters outside homes. The franchisee will install (or support self-install) of the Nt units in subscriber homes.

The franchisee will be responsible for marketing, sales and customer support. The pricing is expected to be $28.95/month for a 300-400 Kbps service (based on Main.net G1 equipment), with no contract and no installation fee. While the franchisee is not necessarily bound to use Main.net equipment, the expectation is that bidders will continue in the direction Manassas has used for the pilot. The service speed will be increased as they deploy Main.net G2 equipment, which has just gotten underway.

Because Manassas already had a lot of fiber in place, and expects the franchisee to bear the capital expense for the BPL equipment, the initial capital expense for the city is expected to be less than $400,000.

Their evaluation is that BPL is best suited for medium to high density areas. It works, can be deployed quickly, and doesn't cause outages of the electrical plant. Their existing staff can install and maintain the equipment in the grid. Once it is installed, the city gets the benefit of outage reporting from the network management system. In addition, the city can use the BPL infrastructure for municipal applications such as control of traffic lights.

( www.powerline-plc.com ) ( www.manassascity.org )