Filtering Time-Stamped Process Values from SICAM eRTU to WinCC

Overview: Substation Time-Tagged Telemetry to SCADA

Time-stamped process data is the backbone of modern substation automation. A breaker trip recorded at 14:32:07.412 in the field must arrive at the control center with the same millisecond resolution, not with the SCADA server's scan time. This article explains how to filter a process value and its time stamp from an incoming IEC 61850 / IEC 60870-5-104 telegram inside a SICAM eRTU built on a SIMATIC S7-400 CPU 416-3, place both into a STEP 7 data block using the INF2DB function block from the SICAM library, and then surface them as time-correct WinCC messages in SIMATIC WinCC Alarm Logging.

The architecture in scope is the standard Siemens Energy substation layout:

• Bay Controllers / IEDs in the switchyard (SIPROTEC 4/5, 7SA86, 7UT85, etc.) transmit GOOSE and/or MMS reports carrying a UTC timestamp per the IEC 61850 data model.
• The SICAM eRTU (central unit = S7-400 CPU 416-3, e.g. 6ES7416-3ES06-0AB0) ingests those reports, decodes them, and stores them in a process image.
• WinCC V7.x or TIA WinCC Professional on the station computer polls the S7-400 over Industrial Ethernet / S7 Protocol and renders operator messages with the original time tag.

Prerequisites

Confirm that the SICAM eRTU and the WinCC station are on the same time source. With GPS-based time, the typical end-to-end accuracy achievable on a properly engineered SICAM eRTU subnet is better than ±5 ms, and the IEEE paper "A Polyline-based Visualization Technique for Tagged Time-varying Data" discusses visualization strategies for time-tagged SCADA data that are directly applicable to WinCC trend and message views.

How Time Tags Arrive at the S7-400

An IEC 61850 data object of type Quality-MmsType / Timestamp carries an 8-byte UTC time field plus a 1-byte quality indicator inside every MV (measured value), SPS (single-point status), DPS, or INC structure. The S7-400 receives the report through the SICAM eRTU IEC 61850 stack, which translates it into the SICAM process image (PI).

For an MMS report, the stack populates two parallel fields per signal:

• value – the Boolean, integer, or float process value.
• t – an 8-byte TIME_AND_DATE / DATE_AND_TIME equivalent holding the 64-bit UTC timestamp from the IED.

Internally, SICAM stores the time as a DATE_AND_TIME (DT) data type: 8 bytes, byte 0 = year (BCD), byte 1 = month, byte 2 = day, byte 3 = hour, byte 4 = minute, byte 5 = second, bytes 6–7 = milliseconds (the high nibble of byte 6 is reserved). This format is what STEP 7 expects in its DATE_AND_TIME declaration and what WinCC Alarm Logging consumes when you bind the message to a tag of type Date/Time.

The INF2DB Block – Purpose and Interface

INF2DB is a SICAM library function block whose task is to copy an information entry (the IED point's value, time, and quality) from the SICAM process image into a STEP 7 data block that the SCADA system can read. The block lives in the SICAM S7-400 library and is typically called in OB1 or OB35 (cyclic 100 ms or 1 s) depending on refresh requirements.

Standard instance interface (FB type, varies slightly by SICAM Toolbox version):

One call to INF2DB writes a single INF record into the destination DB. A standard INF record occupies 24 bytes:

• Bytes 0–1: value (BOOL/INT/FLOAT depending on the configured data type)
• Bytes 2–9: DATE_AND_TIME (8 bytes)
• Bytes 10–11: quality flags + validity
• Bytes 12–23: SICAM internal status / spare / next-link pointer

For a typical SPS (single-point status with quality), the value area is 2 bytes; for a MV measured value with engineering range, it expands to 4 or 8 bytes depending on whether you expose the float or the scaled integer. Plan the DB size accordingly: nSignals * 24 rounded up to the next even boundary.

Step-by-Step Configuration

Step 1 – Build the IED Topology in SICAM TOOLBOX II

1. Open the SICAM TOOLBOX II project that defines the substation.
2. Import the ICD/CID file of the bay IED (SIPROTEC 5 export, REF615, etc.) using File → Import → IEC 61850 IED Description.
3. In the Process Image view, mark every data object you need to forward to WinCC and note its internal information number. This is the value that goes into INF_NO on INF2DB.
4. Verify in the Communication Diagnostics window that reports are arriving and the Time Stamp column shows valid UTC time (not 1980-01-01 which indicates time sync loss).

Step 2 – Create a STEP 7 DB for INF Records

In the STEP 7 project for the S7-400, add a new shared data block (DB), e.g. DB200 – "WinCC_MSG_DB". Declare a custom structure that mirrors the INF record layout, or use a simple array of bytes:

DATA_BLOCK DB200
TITLE = 'WinCC Message Database'
AUTHOR : Siemens
VERSION : 0.1
  STRUCT
    INF : ARRAY [1..64] OF // up to 64 INF records
      STRUCT
        Value    : REAL;   // 4 bytes – MV float
        Time     : DATE_AND_TIME; // 8 bytes
        Quality  : BYTE;   // IEC 61850 quality summary
        Spare    : ARRAY[1..11] OF BYTE;
      END_STRUCT;
  END_STRUCT;
END_DATA_BLOCK

Note: 64 records × 24 bytes = 1536 bytes, which fits well inside the work memory of a 416-3. The DB_OFFSET for the i-th record is (i-1) * 24. If you are using the byte-array layout, pre-compute the offsets in a table for quick reference.

Step 3 – Call INF2DB for Each Signal

In OB1 (or OB35 for a 100 ms cyclic refresh), call INF2DB for every information number you want to forward. Example for breaker position point 1001:

      CALL FB 100, DB1000  // FB100 = INF2DB, instance DB1000
       INF_NO   := 1001
       DB_NO    := 200
       DB_OFFSET := 0      // first record in DB200
       EN_MSG   := TRUE
       MODE     := B#16#0  // write on change
       VALID    := M10.0
       ERR      := MW12

Repeat for the next signal with DB_OFFSET := 24, then 48, 72, and so on. Use a small ladder/ST sequence in OB1 to populate the offsets, or assign them manually in a watch table while commissioning.

Step 4 – Configure WinCC Tag Connection

1. In WinCC Explorer open Tag Management → SIMATIC S7 PROTOCOL SUITE → TCP/IP. Add a new connection with the S7-400 CP443-1 IP address (default station address = rack/slot 0/2 for CPU 416-3 PN).
2. Add tags pointing into DB200:
   • Breaker1_Pos_Value – DB200.DBX0.0 / WORD at offset 0, data type Unsigned 16 (for SPS) or Float (for MV).
   • Breaker1_Pos_Time – DB200.DBX2.0 with data type Date/Time, length 8 bytes.
   • Breaker1_Pos_Quality – DB200.DBX10.0, type Unsigned 8.
3. Enable the Date/Time tag format and verify in the tag simulation that the value updates.

Step 5 – Build the WinCC Message

1. Open Alarm Logging.
2. Create a new single message, e.g. "Breaker Position Change" with number 100001.
3. Set the trigger tag to the value field (Breaker1_Pos_Value). For a 0→1 and 1→0 transition, add two messages or configure the bit mask under Trigger.
4. In the message text, reference Time stamp from tag – select Breaker1_Pos_Time as the Tag for Time Stamp. This is the critical link: WinCC will use the field time, not the SCADA receive time.
5. Optionally add the Quality tag to the message text using a dynamic text list (Good=0, Substituted=1, Failure=2, etc. per IEC 61850 quality bits).
6. Compile Alarm Logging and download to the runtime.

Step 6 – Runtime Verification

Trigger a forced status change from the bay IED (SICAM IEDScout, DIGSI 5, or REF615 setting tool) and watch the WinCC message window. The displayed time must match the time stamp shown in the SICAM process image (drift < 1 s due to refresh jitter; ideally identical).

INF2DB Error Code Reference

Verification Checklist

Troubleshooting Matrix

Performance and Sizing Notes

The 416-3 has roughly 0.045 ms execution time for the INF2DB call in typical SICAM firmware. Calling it 200 times in OB35 means 9 ms CPU load per cycle, well under the 100 ms cycle budget. A more aggressive approach with 1000 signals in OB1 will consume ~45 ms and may interfere with bus communication – move to OB35 or a dedicated OB (e.g. OB32 at 500 ms) in that case.

DB200 at 1.5 KB for 64 records fits within the S7-400's 16 MB work memory with a negligible impact. If you need to expose more than 200 signals, split them into multiple DBs (DB200, DB201, …) and ensure each INF2DB call references the correct DB_NO.

Compatibility and Firmware Notes

• SICAM eRTU V5.x and CPU 416-3 (6ES7416-3ES06) is the current Siemens Energy validated combination. Earlier eRTU versions (V3.x) used the older 416-2 CPU and a slightly different block interface – if you migrate, check the SICAM Toolbox release notes.
• WinCC V7.5 SP2 and TIA WinCC Professional V18 are supported; V8.0 (TIA) requires the S7-400 to be imported as a "legacy device" since S7-400 is not a native TIA target.
• STEP 7 V5.7 is required to download to a 416-3 with firmware V6.0.4 or later; STEP 7 V5.5 cannot program those newer firmware versions.

Frequently Asked Questions