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EnerVista PMCS 6.15 Quick Start Guide
UR 1.1.1.2 2000ms 2000ms
Multinet 1.1.1.3 1500ms 1500ms
*ML750 1.1.1.4 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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