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Outline Guide to ITER PON ArchivingDesign, development, procurement, operation and maintenance of ITERPON ArchivingAbstractThis guide provides simple and practical guidance to plant system Instrumentation and Control (I&C) responsible officers and designers on how to design, develop, procure, operate and maintain an effective plant system archiving system on PON.

Approval Process Name Action AffiliationAuthor Utzel N. 21 Aug 2017:signed IO/DG/COO/SCOD/CSD/CDCCo-AuthorsReviewers Park M.

Petitpas P. 04 Sep 2017:recommended04 Sep 2017:recommended

IO/DG/COO/SCOD/CSD/CDCIO/DG/COO/SCOD/CSD/PCI

Approver Wallander A. 05 Sep 2017:approved IO/DG/COO/SCOD/CSD#SecureIDM#

RO: Park MikyungRead Access LG: CODAC team, AD: ITER, AD: External Collaborators, AD: IO_Director-General, AD: EMAB, AD:

OBS - CODAC Section (CDC), AD: Auditors, AD: ITER Management Assessor, project administrator, RO, AD: OBS - Control System Division (CSD) - EXT, AD: OBS - CODAC Section (CDC) - EXT

IDM UID

B7N2B7VERSION CREATED ON / VERSION / STATUS

21 Aug 2017 / 1.2 / Approved

EXTERNAL REFERENCE / VERSION

PDF generated on 05 Sep 2017DISCLAIMER : UNCONTROLLED WHEN PRINTED – PLEASE CHECK THE STATUS OF THE DOCUMENT IN IDM

Change Log

Outline Guide to ITER PON Archiving (B7N2B7)

Version Latest Status Issue Date Description of Change

v0.0 In Work 23 Oct 2012

v1.0 Approved 18 Jan 2013 Version for final approvalv1.1 Approved 06 Mar 2013 Title changev1.2 Approved 21 Aug 2017 Document simplification with EPICS configuration emphasised. More

explanation about the “monitor” archiving mode and how the memory buffer size for each PV is estimated.

Outline Guide to ITER PON Archiving (B7N2B7) Page 1 of 9

Table of Contents

1 Introduction .........................................................................................................................21.1 PCDH Context .............................................................................................................21.2 Document Scope...........................................................................................................21.3 Definitions ....................................................................................................................3

1.3.1 Difference between Backup and Archive...............................................................31.3.2 Difference between Log and Archive ....................................................................31.3.3 Difference between Logbook and Archive.............................................................4

1.4 Related documents.......................................................................................................42 PON Archiving Principles ..................................................................................................5

2.1 What is a sample?........................................................................................................52.2 What are EPICS Monitors? .......................................................................................62.3 Signal noise reduction .................................................................................................6

3 PON Archiving in Details ...................................................................................................73.1 Is Archived? .................................................................................................................73.2 Event Driven Archiving ..............................................................................................73.3 Archiving Monitor Mode ............................................................................................73.4 Archiving Monitor with Threshold Mode.................................................................73.5 Archiving Scan Mode ..................................................................................................8

4 PON Archiving Data Retrieval...........................................................................................84.1 Trending Tool ..............................................................................................................84.2 PON Archiving Post-Analyser....................................................................................94.3 PON Archiving Export................................................................................................94.4 PON Archiving Retrieval Service ..............................................................................9


1 Introduction

1.1 PCDH Context

The Plant Control Design Handbook (PCDH) [RD1] defines methodology, standards, specifications and interfaces applicable to the whole life cycle of ITER plant Instrumentation & Control (I&C) systems. I&C standards are essential for ITER to:

Integrate all plant systems into one integrated control system. Maintain all plant systems after delivery acceptance. Contain cost by economy of scale.

The PCDH comprises a core document which presents the plant system I&C life cycle and recaps the main rules to be applied to the plant system I&Cs for conventional controls, interlocks and safety controls. Some I&C topics will be explained in greater detail in dedicated documents associated with PCDH as presented in Figure 1.1. This document is one of them.

Core PCDH (27LH2V)Plant system control philosophyPlant system control Life CyclePlant system control specificationsCODAC interface specificationsInterlock I&C specificationSafety I&C specification

PCDH core and satellite documents: v7PS CONTROL DESIGN

Plant system I&C architecture (32GEBH)

Methodology for PS I&C specifications (353AZY)

CODAC Core System Overview (34SDZ5) INTERLOCK CONTROLS

Guidelines for PIS design (3PZ2D2)

Guidelines for PIS integration & config. (7LELG4)

Management of local interlock functions (75ZVTY)

PIS Operation and Maintenance (7L9QXR)

I&C CONVENTIONSI&C Signal and variable naming (2UT8SH)

ITER CODAC Glossary (34QECT)

ITER CODAC Acronym list (2LT73V)

PS SELF DESCRIPTION DATASelf description schema documentation (34QXCP)

CATALOGUES for PS CONTROLSlow controllers products (333J63)

Fast controller products (345X28)

Cubicle products (35LXVZ)

Integration kit for PS I&C (C8X9AE)

PS CONTROL INTEGRATIONThe CODAC -PS Interface (34V362)

PS I&C integration plan (3VVU9W)

ITER alarm system management (3WCD7T)

ITER operator user interface (3XLESZ)

Guidelines for PON archiving (B7N2B7)

PS Operating State management (AC2P4J)

Guidelines for Diagnostic data structure (354SJ3)PS CONTROL DEVELOPMENT

I&C signal interface (3299VT)

PLC software engineering handbook (3QPL4H)

Guidelines for fast controllers (333K4C)

Software engineering and QA for CODAC (2NRS2K)

Guidelines for I&C cubicle configurations (4H5DW6)

CWS case study specifications (35W299)

NUCLEAR PCDH (2YNEFU)

OCCUPATIONAL SAFETY CONTROLSGuidelines for PSS design (C99J7G)

Available and approved

Legend

This document

(XXXXXX) IDM ref.

Guidelines for PON archiving (B7N2B7)

Figure 1-1 Schema of PCDH documents

1.2 Document Scope

This guide provides simple and practical guidance to responsible officers and designers of plant system Instrumentation and Control (I&C) on how to design, develop, procure, operate and maintain an effective plant system archiving system on PON (Plant Operation Network).


1.3 Definitions

ITER PON Archiving is designed to provide ongoing rapid access to historical data in order to analyse trends or a sequence of events.

Figure 1-2 shows fours trended EPICS process variables plotted over 1 month using CODAC Core System cs-studio data browser tool.

Figure 1-2 Plot of one month of archived data

1.3.1 Difference between Backup and ArchiveA classic backup application takes periodic images of active data in order to provide a method of recovering information that have been deleted or destroyed.

Essentially, a backup is designed as a short-term insurance policy to facilitate disaster recovery, while archive is designed for data analysis.

1.3.2 Difference between Log and ArchiveMessages are logged on the Log System to keep track of some events like an operator action - alarm acknowledgment, a configuration change, an alarm state change or some severe system exceptions.

The operator can access to the message history using a cs-studio tool as shown on Figure 1-3.

Figure 1-3 – Message History View


1.3.3 Difference between Logbook and ArchiveITER electronic logbook (ELog) intends at supporting operational and experimental activities by tracking relevant machine and plasma operation status and changes.

A Plant system operator can use Elog to report on an event with automatic content from cs-studio tools such as alarm information or a plot as illustrated on Figure 1-4.

Figure 1-4 – ELog web interface

1.4 Related documents

[RD1] Plant Control Design Handbook (PCDH). (ITER_D_27LH2V)


2 PON Archiving PrinciplesPON Archiving System can monitor any value that is available via Channel Access (CA) - the EPICS communication protocol (~10Hz) - such as tank levels, pump status or system pressures, store them in a central repository and make them available to the operator for trend analysis.

The configuration and operation of PON Archiving system require some planning, as only data that was sampled and stored will be available for future retrieval and analysis.

Some sensible compromise will have to be made between the urge to store all miniscule changes of all the available process variables (PVs) on one hand, and data storage constraints on the other hand.

2.1 What is a sample?

ITER PON Archiving System monitors process variables that are served by an EPICS IOC Channel Access server. It stores all the information available via CA according to the archive monitoring parameters:

• Original Time Stamp (nanosecond precision)• Value (integer, float, array or string)• Alarm Status/Severity (major, minor, no_alarm)• Meta information: like engineering units and display ranges.

It is possible to inspect the samples using a dedicated view in cs-studio as illustrated on Figure 2-1.

Figure 2-1 – Inspect samples view

The PON Archiving System stores the original time stamps as it receives them from Channel Access. It cannot check if these time stamps are valid, except that it refuses to go “back in time” because it can only append new values/time stamps in the data storage. It is therefore imperative to properly configure the data sources, i.e. the clocks on the CA servers and the slow/fast controllers.

NOTE: If the CA server provides bad time stamps, i.e. stamps that are older than values which are already in the storage, the archiving system will log a warning message and refuse to store the samples affected. This is a common reason for “Why is there no data in my archive?”.

It is also important to configure and synchronise the time between the data sources and the client – operator terminal or mini-CODAC. Plotting -1 hour of data will generate a request to the data store based on the “now()” time on the client. This is another common reason for “Why is there no historical data on my plot?”.


2.2 What are EPICS Monitors?

EPICS monitors are a mechanism that provides a channel access client with process variable data without having to constantly poll the IOC.

Through channel access, monitors inform the operator interface, the alarm and archive systems and any other clients about a PV change.

Monitors can be placed on any field that can be accessed: floats, integers, strings, enumerated, waveforms.

Monitors on the PV value are sent when either the value changes or the alarm condition changes.

Values of the floating-point type are special in that there are two deadbands around the monitor notification:

- ADEL for archive monitors,- MDEL for all other monitors.

These deadbands are provided to aid the user in reducing the amount of processing by filtering out negligible value changes. These numbers should be set after considering the precision required by the application. Setting these deadbands carefully could considerably extend the capability of an IOC.

Each time the record is processed, the last sent value is compared to the current value, and if the change is greater than the deadband, new monitors are sent

if ((current value - last value) > deadband)send monitors

Of course, the formula is a little bit more complicated in order to deal with negative numbers and other subtleties, but the basic idea is the same.

Practically: the archive dead band (ADEL) limits the values that will be received by ITER PON Archiving system in order to reduce the network traffic and storage space by filtering out minor value changes.

NOTE: The archiving system has no knowledge of the scan and processing rate or the dead band of an EPICS process variable! It is just a CA client that subscribes to PV and monitors them.

2.3 Signal noise reduction

SMOO is a smoothing filter to reduce noise on the input signal.

The smoothing argument is a constant between 0 and 1 and is specified in the SMOO field. It is applied to the converted hardware signal as follows:eng. units = (new eng units * (1 - smoothing) +

(prev. eng units * smoothing))


3 PON Archiving in DetailsDuring the design phase, CODAC provides tools to edit each CBS archive configuration:

- EPICS records and monitoring fields- Archiving mode.

3.1 Is Archived?

Only when the variable is configured as “Is Archived? = Yes” will it be considered as part of ITER PON archiving system. By default, a variable is not archived.

3.2 Event Driven Archiving

Archiving can be enabled / disabled according to a specific variable defined as the “enabling” variable:

• Whenever the value of this variable is above zero, sampling and archiving of a whole group (CBS level) will be enabled until the variable returns to zero or below.

A typical use case is the configuration of a power supply function with a set of process variables and the power supply state ON/OFF PV configured as the enabling variable of the group. The benefit of this configuration is to suppress archiving of noise while the power supply is OFF.

This is a property of the process variable that marks it as the enabling archive PV.

3.3 Archiving Monitor Mode

Using the Archiving Monitor mode, each value received is stored:

• In this mode, the archiving system requests a Channel Access Monitor, i.e. it subscribes to changes and stores all the values sent out,

• The Channel Access server determines when values are sent to the archiving system.

With a perfectly configured data source with adequate EPICS thresholds that only notify significant changes, this mode is ideal and is the default and recommended one.

Important changes in value are written to the archive, whilst noise in the signal is suppressed to minimise waste of resources.

When configuring a PV to be archived, the estimated time period between changes needs to be configured to allow the archiving system to reserve for the PV a suitable memory buffer where it stores received samples until they are written periodically to the storage.

memory buffer for each PV size = buffer_reserve × write_period / estimated_time_period

with buffer_reserve=2 and write_period=30 seconds

For a PV updated at 0.1 second max, buffer size = 2 x 30 / 0.1 = 600 samples

If the estimated time period between changes is under-estimated, the archiving system overwrites older samples in the ring buffer with newly arriving samples the archiving system overruns.

3.4 Archiving Monitor with Threshold Mode

Using the Archive Monitor with Threshold mode, each value received is compared by the archiving system to the previous one and stored only if the change is greater than the configured dead band:

• The Archive Engine performs the dead band checks in place of the Channel Access server.

But to minimise network traffic and archiving system CPU load, this should happen on the EPICS PV level with the configuration of the PV ADEL threshold.

As previously, in addition to the threshold, the estimated time period between changes needs to be configured to allow the archiving system to reserve for the PV a suitable memory buffer.


3.5 Archiving Scan Mode

Using the Archiving Scan mode, the archiving system receives each update from the data source but only writes the most recent ones at specific intervals, for example once every 5 minutes:

• This mode was created for PVs which do not have a good dead band configuration and where using monitored mode would add too many data to the archive,

• But should the archive engine fill disk space every 5 minutes if the PV has no significant change for hours? Actually, the archiving system will repeat the same value in the storage maximum 60 times consecutively,

• If an important event happened producing a brief blip, it will probably be missed when storing a value every 5 minutes.

Periodic sampling is clearly imperfect, and shall be used with care.

4 PON Archiving Data Retrieval

4.1 Trending Tool

The operator can:

• Have both historical and live data trending,• Define online or use predefined plot configuration,• Integrate plot within the operator interface,• Plot many trended EPICS PVs at once,• Use formulas (min, max, Java Math routines…),• Zoom, individually scale the time axis and the value range and start/stop scrolling,• Make annotations,• Save a snapshot to PNG file.

Figure 4-1 illustrates the trend of 3 archived PVs over 1 month of operation.

Figure 4-1 – CS-Studio trending tool

For improved display and analysis capabilities, the line thickness, color and style of trends can be configured.


4.2 PON Archiving Post-Analyser

The PON Archiving Analyser tool gives the capability to display integrated statistical functions – FFT, correlation, Gaussian fit, exponential fit or line fit.

4.3 PON Archiving Export

It is possible to export historical data from a plot into files:

- Spreadsheet format - TAB-delimited columns format suitable for import into programs like Microsoft Excel or OpenOffice Calc

- Matlab format - binary .mat or text .m file

An export of archived data into a file can also be done from command line using a dedicated archive view.

4.4 PON Archiving Retrieval Service

A PON archiving data retrieval service will support multiple formats/MIME types like:

- JSON format that can be easily loaded into most browsers using Javascript,- CSV that can be used for importing into Excel and other spreadsheets,- MAT which is the file format used for interoperating with Matlab.

Some processing like the mean over a period of time will be supported during data retrieval.

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