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of 5 COPYRIGHT, 2009, GE PACKAGED POWER, L.P.,ALL RIGHTS RESERVED. THIS DRAWING IS THE PROPRIETARY AND/OR CONFIDENTIAL PROPERTY OF GE

PACKAGED POWER, L.P., AND IS LOANED IN STRICT CONFIDENCE WITH THE UNDERSTANDING THAT IT WILL NOT BE REPRODUCED NOR USED FOR ANY PURPOSE

EXCEPT THAT FOR WHICH IT IS LOANED. IT SHALL BE IMMEDIATELY RETURNED ON DEMAND, AND IS SUBJECT TO ALL OTHER TERMS AND CONDITIONS OF ANY

WRITTEN AGREEMENT OR PURCHASE ORDER WHICH INCORPORATES OR RELATES TO THIS DRAWING.

LM Control Systems & Wireless Communications

Introduction

GE Energy LM power generation systems are utilized in a wide variety of power generation applications, site conditions, and physical layouts. In the following paper we examine the applicability of currently available industrial wireless control system components to LM power generation controls.

LM Control System Communications Current Approach

Signal path Connections

Today, LM controls make extensive use of distributed I/O systems to substantially reduce the number of signal level interconnections between the main equipment assemblies and the control room.

The typical LM power generation system instrumentation and controls require connections between:

• Sensors and control system Input modules.

• Distributed control system input/output modules (located on several machinery assemblies).

• Control system I/O modules and the control system CPU(s).

• Control system CPU(s) and control subsystems/monitors.

• Control system CPU(s) and local and remote human machine interfaces (HMI PCs).

• Control system CPU(s) and plant control systems.

LM system equipment assemblies are generally packaged in enclosed or unenclosed modules (skids). Connections between sensors and input control system input modules are typically assembled and inspected within each equipment module at the factory, and generally do not need further assembly during field installation. This approach minimizes cable lengths within the equipment modules, reduces signal interference, increases system availability, and lowers the potential for connection failures between the equipment modules.

GE Energy Aero Energy Division

Position Paper #51

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Date: January 12, 2009

16415 Jacintoport Blvd

Houston, TX 77015

USA

T 001-281-864-2803

F 001-281-864-2977

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The connection requirements between each of the systems vary: - Type of signal (serial, digital, 4-20mA etc) - Performance requirements (update rates 10mS to 100mS) - Need for determinism (closed loop control) - Level of required availability (monitoring, control, safety functions) Connections from the distributed I/O system to the controller/control room are typically high speed serial links implemented with fiber optic cables with ST connectors. Short length connections between the controllers and human machine interface are typically high speed copper serial links. Power to controls and instrumentation, supplied by battery backed redundant DC charger systems, is connected via multiple copper wire medium, and is locally filtered and regulated on the equipment modules.

Wireless Control System Communications

The current marketplace includes many providers that make wireless connectivity possible between sensors and the control system(s) via wireless instrument transmitters/receivers and wireless I/O systems. While primarily intended for monitoring applications, some wireless systems are now being applied to control applications as well. Can Wireless systems be applied to GE LM Systems? - Key Considerations

Given the currently applied GE solutions described above, how do today’s off the shelf wireless product capabilities compare?

Wireless Instrument Transmitter

Wireless I/O Module

Mesh Network

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Power Source(s) Instrument transmitter –To be truly wireless, the typical wireless instrument transmitter includes an energy source, typically a non-rechargeable lithium/thionyl chloride battery. The lithium/thionyl chloride battery provides a very long shelf life, and “full” voltage output over long periods of time. Ultimately, battery life is mostly dependent upon the update rate required to adequately monitor/control the parameter of interest. With respect to the extremes of data update rates, rated battery life typically ranges from one month to 10 years. Wireless I/O system - Multichannel wireless I/O systems typically consume much more power than sensor transmitters and are typically designed to be powered by conventional external power sources. While most of the wireless I/O designs require power wiring, the benefit of the elimination of wired interconnections of individual signals to the controller is retained. Energy harvesting - Some wireless applications also utilize energy harvesting (light, motion, heat) as supplemental power source(s) combined with a rechargeable battery system, or, to provide primary power for devices that need very small amounts of energy. The tradeoffs are: - The energy harvesting device is (often by necessity) connected to the “wireless” device via conventional wiring. - Energy harvesting typically does not provide energy on a continual basis. Typical power generation systems require that continuous electrical power be supplied to the control systems during both running and non-running conditions, so in these applications, the wireless devices would often be dependent on the batteries. Update Rates Wireless Instrument transmitter - In order to conserve battery life, transmitters typically provide new data based upon a predetermined condition/event, or at selectable update rates. Typical update rates range from once a second to once every sixty minutes. Wireless I/O systems - Some currently marketed wireless I/O systems provide much more frequent update rates than wireless sensor transmitters. The update rates available from either type of wireless device is adequate for turbine/generator sub-system parameters that change “slowly” during both normal and abnormal process conditions. However, most “off the shelf” wireless systems do not provide an adequate update rate for monitoring and control of the “high speed” engine parameters, generator parameters, and control functions within the LM system.

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Availability The most advanced wireless instrument systems typically use “mesh” networks to provide maximum signal availability. Mesh network technology provides several signal paths for each sensor transmitter, avoiding extended loss of information if one or more signal paths become intermittent or disabled due to signal interference or loss of signal. In this respect, each individual instrument’s signal availability is very competitive with that of wired systems. It is however, necessary to note that when plant equipment maintenance is planned (movement of large sub assemblies for repair), plant layout is changed, or additional wireless devices are added to the plant, an RF site survey may need to be repeated to confirm multiple signal paths are still viable or if they need to be re-established. Currently LM power generation systems typically utilize fiber optic cable between major equipment modules, so, site layout changes and sources of electromagnetic interference on the longest cable paths are not a concern. Security Security is growing as a major concern to power generation facility operators. Wireless instrument systems can be very robust and nearly impossible to breach due to the inherent resistance of spread spectrum technology to unauthorized access, jamming, or interference. Wireless instrument systems currently appear to be very secure. GE Aero’s use of wired, and fiber optic control system I/O connections ensure that the control system signals cannot be accessed without a breach of the plant’s physical perimeter. All system communications, providing remote access via the Internet, whether connected with wireless or wired devices, must be protected from unauthorized access by encryption/secure VPN technology. Costs Wireless systems can provide substantial cost savings in large system installations, primarily, by elimination of control system input modules and wiring installation costs. With respect to LM power generation systems, the distances within the equipment modules, between the sensor/transmitter to the distributed I/O system input module rarely exceeds 50 ft. The potential installation cost savings are somewhat reduced due to these relatively short distances, battery maintenance, and substantially higher initial costs for wireless devices. Licensing Although most countries tend to allocate frequencies in accordance with the ITU (International Telecommunication Union) frequency allocation table, licensing requirements for wireless devices vary from country to country. Vendors of wireless devices under consideration should have experience with the licensing and application of their equipment in worldwide locations.

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Conclusion

Parameters utilized in control functions requiring frequent update rates, would continue to need wired instrument connections to the distributed I/O system, and concerns about signal system security and availability need further study. Given the limited applicability due to limited update rates, and battery life concerns, currently available wireless instrument devices do not provide significant advantages for LM modular packaged equipment systems at this time. Wireless I/O systems, capable of much faster update rates, could be applicable for a larger number of the process parameters, allowing further elimination of signal interconnect wiring. Looking ahead, if the technology is properly focused, it is likely that the ability to provide wireless transmission of monitoring and controls for power generation systems can be realized in the near future. GE Aero Energy will continue to monitor the progression of wireless systems, and periodically re-evaluate the available devices for potential applications.

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