TREND TREATMENT PROPERTY
I have 1 doubt regarding the trend treatement of how it shows data. Please see the attached scrrenshot of incomer feeder at one of our site. The marked trend is for KW which varies from 5 to 50 MW around 3-4 time in 1 hour interval.but if you can see the trends remain linear for most of the time durig that interval. can someone please explain this.
Logname I have taken as SEAMLESS & Treatement I selected as TIMEAVERAGE.
Can this problem be solved if I select treatment as "ExtMomentary", i.e. it will show the exact curve when the value changes from 5 to 50MW. it should represent distorted trend ifit their as linear curve indicate not considerable change.
TimeAverage will attempt to read data from the most suitable log, or set of logs and the result is then merged and *resampled* to match the current trend window's resolution. This reduces number of bytes to read from disk and send over wire to client.
ExtMomentary will read ALL points of the scope from the PRIMARY LOG ONLY and remove any overlapping points before sending the data over the wire to the client.
Momentary is similar to ExtMomentary, but here ALL points are also sent to the trend, even if they overlap.
Obviously, the TimeAverage treatment is the fastest one because it will enable reading data from secondary logs (a trend with 1 day scope size often have a max resolution of several minutes).
But a 5 minute averaging log (if available in the Log Template) will for obvious reasons not show all movements of the signal. The content is a mean value of the period.
ExtMomentary is a good choice when scope size is small to medium, but will work less good with large scopes since the amount of data to be retrieved could be immense (tens of megabytes, per trend curve).
Momentary is the slowest of them all. It is also unable to read secondary data.
By selecting a log name (instead of SEAMLESS) you even further reduces the choice of log to read. Hence, use SEAMLESS to enable reading from all logs.
Small scope: use TimeAverage or ExtMomentary
Large scope: use TimeAverage
Never use Momentary. ExtMomentary gives same output to a lesser cost.
Remember to turn on the "Refresh when zooming" setting on the trend template, or else you must press "L" on the keyboard to force the trend to retrieve new data after zooming.