Diagnosing Strikethrough Time Displays and System Icons in WinCC OS Runtime Headers

In SIMATIC PCS 7 WinCC OS Runtime, a strikethrough line displayed across the system time in the overview screen header indicates a Time Synchronization Failure: the OS station has lost connection to its designated time master, incoming time frames have ceased, or the local clock deviates beyond permissible synchronization tolerance. In the alarm one-line header (@AlarmOneLine.pdl), the '??' symbol indicates an unassigned or empty Batch ID / Order string, while an 'X' icon with a blue background is the standard 'Loop in Alarm' indicator, signifying that the active alarm is linked to a process picture and clicking the icon will navigate directly to that picture and open the originating block's faceplate.

Executive Summary

The runtime overview area and alarm header in SIMATIC PCS 7 provide critical visual telemetry regarding overall plant health, operator permissions, active alarms, and system integrity. During plant commissioning or following network maintenance, automation engineers frequently observe visual anomalies in the WinCC runtime header: the digital clock appears static or struck through with a horizontal line, and cryptic symbols appear within the single-line alarm banner (@AlarmOneLine.pdl), including question marks (??) and an X badge overlaid on a blue background.

These visual markers are not random software glitches; they are standardized PCS 7 system status indicators. A strikethrough time display warns operators that chronological event logging and alarm sequence order can no longer be guaranteed due to a plant bus time synchronization fault. Understanding these indicators allows engineers to rapidly isolate network communication issues, verify time master status, and correctly utilize operator navigation shortcuts. This guide decodes the standard runtime header symbols, explains the mechanics of the time synchronization watchdog, and provides the step-by-step procedure to restore valid clock synchronization.

Architecture and Fundamental Mechanics

The WinCC runtime header is generated by standard system screens (@Overview1.pdl and @AlarmOneLine.pdl) driven by the PCS 7 Basic Process Control (BPC) architecture:
1. Time Display Strikethrough Mechanics:
* WinCC incorporates an internal time synchronization monitoring watchdog (TimeSync).
* When Time Synchronization is configured on an OS station (via Terminal Bus or Plant Bus), the local runtime expects cyclic time frames (SIMATIC Mode broadcast or NTP packets) at least once every configured synchronization cycle (typically 10 seconds).
* If the time client receives no valid time frames for more than three consecutive intervals, or if the time difference between the incoming master time and the local system clock exceeds the maximum allowed drift limit, WinCC flags the time as invalid.
* The graphical script attached to the time display text object in @Overview1.pdl detects this invalid status and draws a horizontal strikethrough line across the digits, warning operators that timestamp accuracy is compromised.
2. Decoding Alarm Banner Symbols (@AlarmOneLine.pdl):
* ?? (Double Question Mark): In the alarm line, one of the displayed message columns is configured for 'Batch Name' or 'Batch ID'. When an alarm originates from a continuous process block or a unit where no active SIMATIC BATCH recipe or batch order is assigned, the batch string tag is null. WinCC renders an uninitialized or empty batch parameter as ??.
* X with Blue Background ('Loop in Alarm'): This icon is the standard PCS 7 'Loop in Alarm' button. When an alarm is configured with an origin link (linking the message to a specific WinCC picture name and block icon tag), the Loop in Alarm button illuminates. Clicking this icon immediately opens the associated process picture and highlights the faulted block icon, allowing the operator to address the fault instantly.

Step-by-Step Implementation Procedure

Step 1: Troubleshoot Strikethrough Time and Restore Clock Synchronization

In WinCC Explorer on the affected OS station, open the Time Synchronization editor.
Check the configuration:
* Verify whether the station is configured to synchronize via Terminal Bus or Plant Bus.
* Verify that the IP address of the central NTP master clock or time master server is reachable via ping.
Verify network ports: ensure UDP port 123 (NTP) is not blocked by local Windows Defender Firewall or plant network switches.
Check the S7-400 CPU clock in SIMATIC Manager (PLC > Set Time of Day): confirm the CPU clock is set to UTC without daylight saving offsets.
In Windows Services (services.msc), ensure the Windows Time service (w32time) is running and synchronized.
In WinCC Explorer, restart WinCC Runtime or toggle Time Synchronization off and back on to force an immediate clock resynchronization.

Step 2: Resolve Empty Batch String ('??') in Alarm Header

Open WinCC Explorer and double-click Alarm Logging.
In the Alarm Logging editor, select the message line layout for the single-line banner.
Inspect the column configurations for @AlarmOneLine.pdl:
* If your plant does not utilize SIMATIC BATCH, the 'Batch ID' or 'Batch Name' column is irrelevant.
* In the Message List configuration, remove the 'Batch ID' column from the visible columns list, or replace it with 'Area' or 'Event Text'.
If SIMATIC BATCH is used, verify that SIMATIC BATCH Control Center is active and that the batch recipe has allocated the unit correctly.

Step 3: Validate Loop in Alarm ('X' Icon) Functionality

In the @AlarmOneLine banner, observe the blue icon with the white 'X'.
Click the icon while an active process alarm is highlighted.
Verify that WinCC immediately loads the process picture where the alarming block is located and centers the view on the faulted block icon.
If clicking the icon does not change pictures, ensure that the OS Compile was completed with 'Create/update block icons' enabled so that picture cross-references are populated.

Verification

In WinCC Runtime, observe the digital clock in the upper-right corner of the overview screen: confirm that the strikethrough line is gone and the time updates smoothly each second.
Open WinCC Channel Diagnosis (Tools > Channel Diagnosis): confirm all AS connections report 'Ready' with zero communication errors.
In @AlarmOneLine.pdl, verify that alarm messages display clear text descriptions without ?? badges (unless batch tracking is deliberately unassigned).
Trigger a test alarm on any motor or valve block, highlight the message in the alarm banner, and click the blue 'X' Loop in Alarm icon: confirm instantaneous navigation to the correct process picture.

Limitations and Operational Precautions

Modifying standard @... system pictures (such as @Overview1.pdl or @AlarmOneLine.pdl) directly in Graphics Designer is strongly discouraged; any changes will be overwritten when running the OS Project Editor.
All PCS 7 controllers and servers must operate in UTC; local time conversion is strictly performed at the WinCC display layer.
If an NTP server drifts significantly from true time, resynchronization will jump the system clock, which may cause temporary gaps or duplicates in historical trend archives.
Loop in Alarm navigation requires that the target picture exists in the local GraCS folder of the OS station or is properly assigned in server packages.

Engineer FAQ

Why does the runtime clock have a strikethrough line?

It indicates that WinCC has lost synchronization with its designated time master (Time Synchronization error), warning that event timestamps may not be accurate.

What does the blue icon with the X do in the alarm line?

It is the 'Loop in Alarm' button. Clicking it navigates the operator directly to the process screen containing the block icon that generated the alarm.

Why does '??' appear in the alarm line?

The message column is configured to display the Batch ID, but the alarm originated from a process unit that is not currently running an active SIMATIC BATCH order.

Can I remove the Batch column from the single-line alarm banner?

Yes. In WinCC Alarm Logging, you can customize the message line columns displayed in @AlarmOneLine.pdl to show only relevant process data.

Does the strikethrough clock affect plant operations?

While process control and interlocking in the AS continue uninterrupted, historical trend logging and alarm timestamps may become misaligned until time synchronization is restored.