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Thread: IEC61850 Timestamp

  1. #1
    Join Date
    01.11.2016
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    8

    Default IEC61850 Timestamp

    Hello Support,
    I am using IEC61850 protocol which supports time stapm to read data from SEL 451 relay using buffered reports, the problem is that i am receiving timestamp from the relay with wrong timestamp ( miliseconds in difference).
    Please advise.

  2. #2
    Join Date
    01.07.2008
    Location
    Salzburg, AT
    Posts
    799

    Default Re: IEC61850 Timestamp

    The relay is probably not time synchronized and sends data time stamps with information about bad TimeAccuracy (class > 1ms). This TimeAccuracy information (last byte in t-attributes) forces the iec850 driver to cut non-significant fraction of seconds of the time stamps.
    Please note that may products on the market (and Wireshark) are not evaluating TimeAccuracy to the ms value. But a SCADA system is obligated to evaluate the real time information from devices; whole info.

    If it is not possible to setup the relay to use proper TimeAccuracy you may configure in driver the setting 'ignore time accuracy'. This check-box is relatively new, so if you don't see it in the driver configuration you would have to update to 7.60 and one of the latest builds. This will force the driver - in connection with this particular relay - to evaluate from received t-attribute all bits in fraction of seconds, so also these bits which the relay declares as not relevant (not significant).

  3. #3
    Join Date
    01.11.2016
    Posts
    8

    Default Re: IEC61850 Timestamp

    Thsnks for the reply...what is the leatest build of 7.6 and how i can get it...if i uncheck this box i will get the exact timestamp from the relay?

  4. #4
    Join Date
    01.11.2016
    Posts
    8

    Default Re: IEC61850 Timestamp

    i updated 7.6 to the leatesr build sent by copadata but i cant see check box of ignore accurecy

  5. #5
    Join Date
    22.03.2010
    Posts
    18

    Default Re: IEC61850 Timestamp

    Quote Originally Posted by yazan View Post
    i updated 7.6 to the leatesr build sent by copadata but i cant see check box of ignore accurecy


    Hi!



    Best regards

    Fredrik

  6. #6
    Join Date
    01.11.2016
    Posts
    8

    Default Re: IEC61850 Timestamp

    Thanks...but still after updating and configuration of new option there is time deffirence in miliseconds between ied and zenon??

  7. #7
    Join Date
    22.03.2010
    Posts
    18

    Default Re: IEC61850 Timestamp

    Are you sure that the report block is used?
    If the variable is polled it could cause the mismatch in timestamp.

    Do you have the same time difference for all variables from this ied?
    Is it always the same time offset (in ms)?

  8. #8
    Join Date
    01.11.2016
    Posts
    8

    Default Re: IEC61850 Timestamp

    Yes i am sure that block report is configured and i can monitor report enable variable and its showing 1 means report enable...for some ieds there is delay from 200ms to 20ms, but from some ieds timestamp is fine.
    I can't understand if the problem from ied settigs or zenon report settings

  9. #9
    Join Date
    22.03.2010
    Posts
    18

    Default Re: IEC61850 Timestamp

    If the ied has a synchronized time and RCB is used, the timestamp should be the same in zenon.
    Check the status bits T_INTERN, T_EXTERN and T_INVAL/T_UNSYNC.

    There is plenty of information in the help file:
    Quality, time stamp and status bits of the variable
    Drivers -> IEC850 -> IEC850 client functions -> Quality, time stamp and status bits of the variable

    You could contact your local support for a deeper investigation.


    Best regards

    Fredrik

  10. #10
    Join Date
    01.07.2008
    Location
    Salzburg, AT
    Posts
    799

    Default Re: IEC61850 Timestamp

    yazan:
    Make sure that the IED is time synchronized and is sending correctly the TimeQuality information. 

    If you have configured the driver to 'Ignore time accuracy' but the events have different time stamp in IED as in zenon, then probably the IED is sending the current t-attribute value but with TimeQuality containing ClockFailure bit. When zenon iec850 driver receives t-attribute with ClockFailure flag, then it has to ignore the t-value given by IED (IED informs that its clock failed) and must use the own time stamp - from the clock of the PC with zenon. This can be these 20-200ms later. When this is the case the affected variables (e.g. */stVal[ST]) will have status bits T_INVAL and may have T_UNSYNC too (like Fredrik mentioned).

    In 7.60 you can configure in screen 'Variable diagnosis' additional columns to be visible: 'variable status', 'time internal (UTC)' and 'time external (UTC)'. The 'time internal' is the time from PC clock from the moment when driver has received the event. The 'time external' is the value of the related t-attribute delivered by IED (via Report or polling). But the delivered external t-value will be not used in CEL, AML etc., if the flag ClockFailure in TimeQuality was set by IED.

    TimeQuality is the last byte (8th) of t-values (t-value is 7 bytes UTC time as float and 1 byte TimeQuality not evaluated by Wireshark). In Wireshark you can see it hexadecimal. In this last byte the highest bit is LeapSecondKnown (can be any), then ClockFailure bit (if 1 then client has to ignore the time from IED --> T_INVAL in zenon) and bit ClockNotSychronized (in zenon info T_UNSYNC). The rest 5 bits are the TimeAccuracy. So by valid t-values in Wireshark you will see the last byte of t-value like e.g. 0f, 1f, 8f, 9f. If the first hex number in this byte is neither 0, 1, 8 nor 9 then the IED informs about its problem with the clock.  

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