New SCADA System Adds More Control, More Information

Danetta Bramhall

In 1998, Seattle Public Utilities (SPU), Seattle, Washington had a problem. Y2K was coming and new regulatory requirements were issued by the state's Department of Ecology. During a Y2K analysis on their pumpstation equipment, Dan Pflager, Senior Software Engineer in charge of embedded systems Y2K for SPU, found problems in the software and hardware as well. He also reported that much of the field equipment was obsolete or unsupported.

Regulatory Requirements

But Y2K was only one of the problems SPU needed to address. The new regulations required by the Department of Ecology stated that the current pumpstation network be able to quantify an overflow at any given permitted site. This was not possible with the older monitoring and data collection equipment in place at the time. When it was installed in the 1980s, data collection was expensive, forcing officials to limit data collection parameters to only minimal data necessary to perform SPU's current business and permit requirements.

Designing the New System

SPU decided that in order to meet both the regulatory requirements, avoid any potential for a Y2K incident, and update the legacy equipment, a new system was definitely in order; one that could provide more data from their field equipment and add intelligence to the remote sites to compute and log lift station flow rates and increase the accuracy of data during overflow events.

Robert Schommer from Systems Interface Inc. and Pat Murphy of Rockwell Automation put their heads together and designed just such a system.

Systems Interface, a Seattle-based system integrator company, was granted the bid to design this state-of-the-art SCADA system. Although the specifications detailed by SPU would fit several manufacturers, Robert Schommer, Municipal Business Manager with Systems Interface, recommended Allen-Bradley hardware.

According to Schommer, Systems Interface looked towards Allen-Bradley hardware for various reasons: the excellent local distributor support, the internationally recognized name brand, the large market share and the availability of future product support.

ProSoft Steps In

Integrating multiple applications was needed for the Seattle Telemetry Project since the specifications called for the Modbus protocol.

"The customer preferred an internationally recognized, name brand solution with local distribution and required Modbus protocol," said Schommer. "The solution had to be PLC compatible and the customer preferred the Allen-Bradley hardware, yet A-B couldn't accommodate the need for Modbus."

"That's where ProSoft Technology stepped in," said Doug Sharratt, President and Lead Developer for ProSoft. "A large number of SCADA projects in the Oil & Gas and Water/Waste Water industries have been specified with the Modbus protocol. The ProSoft RTU-5/03 Processor, developed jointly by ProSoft Technology and Allen-Bradley, is aimed specifically at these opportunities. It is an Allen-Bradley SLC 5/03 processor that has been modified to include the Modbus Slave protocol.

"One of the things we pride ourselves in is our ability to fit our products to a particular application and, when needed, to quickly develop solutions based on the market needs and specific customer requests," said Sharratt. "We are a major supplier of protocol emulation modules for the Allen-Bradley family of products. Our strong partner relationship with Rockwell has given us access to proprietary technology licenses, allowing us to offer products tightly integrated into A-B hardware platforms."

"We're just the little guy riding on the coattails of the giant, namely Rockwell Automation," said Lenus Hong, ProSoft's Regional Sales Manager for the Asian-Pacific region. "What we do is just a small part of the big picture, but it is an integral part of that picture."

More Control, More Information, More Support

Once the Modbus protocol is activiated, a Modbus host can read and write data from all the common Modbus data types. In addition, support has been provided for the transfer of Floating Point data, which optionally uses the "Enron" addressing range. A host can also access the processor Status File S2 to remotely monitor the health of the unit or do such things as setting the real time clock.

"SPU couldn't compute station flow rates, including overflow events, with the past system," said Schommer. "Now they can track the well level and integrate it over time to accurately compute and log well inflow, outflow and, how much overflow has occurred."

The new telemetry system consists of a hot backup, redundant, dual processor headquarter master station talking to 72 Remote Telemetry Units (RTU) at each of SPU's sewer pump stations.

"ProSoft's Modbus Communication Modules function independent of the PLC, sharing the task of communications and allowing the processor module to concentrate on control and data functions," said John Stephenson, Project Manager for Systems Interface.

The RTUs monitor the pump station activities and control the operation of the sewage removal equipment, which consist of either pumps or air compressors. The headquarter master polls each RTU via a modem connection and staff at the headquarters monitor the status and alarms in order to track pertinent data and be able to respond to emergency situations. This is far different from the previous system, which couldn't track or control any station flow rates.

"Technically speaking," said Pflager in an interview with the Seattle Times, "they [were] just modems...that have no smarts at all."

The new SCADA system, completed in late October 1999, changed all of that. System testing was completed in June 1999 and a successful simulation of the system was run to catch and correct any defects. The new system passed all compliance tests with flying colors.

Seattle Public Utilities will be adding two more, remote telemetry sites for the combined sewer overflow stations soon. These sites will also use the same Allen-Bradley/ProSoft solution as the main project.