GE PMCS 6.15 quick start Testing, Conclusion

EnerVista PMCS 6.15 Quick Start Guide

UR 1.1.1.2	2000ms
Multinet 1.1.1.3	1500ms
*ML750 1.1.1.4	1500ms

2000ms

1500ms

1500ms

Enervista PMCS

Enervista PMCS incorporate device ‘wizards’ or pre-made device graphics containing data point displays of typically required in a device. These displays can be very data intensive requiring many register calls to a device. This can cause a temporary or ‘exception’ condition where a device that is normally responding in under a second suddenly begins to update at a much slow rate. This is due to additional modbus blocks needed by the graphics. The graphics work in an ‘on-demand’ mode meaning the only time data is requested is when the actual display is open. Once the display screen is closed the device update rate returns to normal. For example when a UR tabular screen is opened in a PMCS system the device update time for that UR can suddenly jump from 1 second to 6 seconds as all the required registers begin to get polled. Once the screen is closed the update time then goes back to 1 second.

Please note that all the screens in a Enervista PMCS system typically require multiple modbus requests to populate the screens. Add in the fact that many other devices are typically multi-dropped on the line and PMCS of waveforms and alarm/events yields an update time of 2~5 seconds on a typically device screen. UPDATES BELOW 1 SECOND CAN ONLY RELIABLY BE ACHIEVED FOR SYSTEMS

RUNNING A DEDICATED MASTER REQUESTING A CONSTANT 1 OR 2 MODBUS BLOCKS FROM A SINGLE DEVICE ON A NETWORK. THIS IS A HIGHLY CUSTOMIZED FUNCTION REQUIRING CAREFUL PLANNING AND DESIGN.

Testing:

For systems testing and evaluation it is frequently impractical or impossible to have a test bed of all the required devices. To this end the Enervista Device Emulator has been designed. This is a Modbus TCP/IP/RTU software slave designed to emulate all the GE Multilin device types, their register maps and real device values both dynamic and static. It will accurately emulate all required network architectures in both size and timing characteristics. With it an integrator or end user can accurately bench test a project for both operation and update times. Virtual network configurations can be created and adjusted/changed before any physical hardware is installed. This software can be purchased thru your local GE Multilin rep.

Conclusion:

Before any network is designed or constructed a careful examination of needed data update performance must be done. Each site and customer is unique. Some customers may require data refresh times in the ten’s of seconds while other require less than a second. Any update requirement within the physical confines of Modbus can be done but require correct network layout and a thorough knowledge of what specific data is needed from each specific device type. This appnote has also examined the differences between Modbus TCP/IP and Modbus RTU. Integrators and users must be especially cogent of the fact that use of Modbus TCP/IP and Ethernet DOES NOT ITSELF INCREASE PERFORMANCE TO ANY NOTICABLE EXTENT. Much more critical is HOW MANY DEVICES ARE ON THE

SAME NETWORK AND HOW MUCH IS POLLED FROM EACH ONE.

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