New digital modems in RTUs improve reliability of gas pressure monitoring.

The telecommunications industry eliminated analog cellular service in urban areas at year-end 2005 so that remote monitoring of natural gas pressure using analog communications technology would no longer work. Switching to digital cellular service was a problem because remote monitoring requires

To solve this problem, a communications equipment package was developed to allow quick, easy replacement of modems and related components in existing remote terminal units (RTUs). Also, new digital cellular service was introduced that allows two-way communications between modems and the SCADA system, with either end able to initiate data exchange. The new digital modems kept RTUs working and improved their performance with better cellular coverage and higher reliability. The replacement equipment also saved about $769,000 vs. buying and installing new remote units.

Using SCADA Systems To Monitor And Control Gas Pressure

One function of SCADA systems in natural gas distribution applications is monitoring and controlling gas pressure at various points in the distribution network. RTUs in gas distribution SCADA systems have replaced old-fashioned paper chart recorders. Today's RTUs enable wireless remote monitoring as well as generating alarms at selected pressure thresholds (whenever the gas pressure in the line drops or gets too high).

KeySpan Corporation is the fifth-largest distributor of natural gas in the United States and the largest in the Northeast, operating regulated gas utilities in New York, Massachusetts, and New Hampshire that serve 2.6 million customers. In KeySpan's system, most RTUs are sited permanently at pressure regulator stations and at low-pressure distribution points. About one-fourth of the RTUs are deployed only in the winter (these are called winter-gage RTUs), when lowered gas distribution pressure is a primary concern. Pressure monitoring by RTUs in SCADA systems has several benefits to gas/energy companies and their customers:

* Ensure adequate gas supply pressures and deliver gas properly to customers.