Differentiating Process Objects (PO) from SCADA PowerTags in SIMATIC PCS 7 and WinCC Licensing

In Siemens industrial automation, Process Objects (PO) and SCADA PowerTags represent fundamentally different licensing and engineering abstractions. A Process Object (PO) in PCS 7 represents an entire functional control entity (such as a motor, valve, PID loop, or analog transmitter) containing dozens of I/O pins, alarms, and faceplate tags, yet counting as exactly 1 AS and 1 OS Process Object. In contrast, a SCADA PowerTag in standalone WinCC licenses individual process variables communicating across the network; a single motor requiring 10 controller tags consumes 10 SCADA PowerTags.

DCS Object-Oriented Engineering vs Traditional SCADA Tagging

Understanding the difference between a Process Object in a Distributed Control System (DCS) and a Tag in a Supervisory Control and Data Acquisition (SCADA) system is essential for accurate system sizing and licensing:
* The Traditional SCADA Philosophy (WinCC Standalone):
SCADA originated as an independent monitoring layer above heterogeneous programmable logic controllers (PLCs). Licensing is structured around raw communication bandwidth: every variable address read from or written to an external controller is counted as an individual PowerTag (1 Tag = 1 License Point).
* The Integrated DCS Philosophy (SIMATIC PCS 7):
PCS 7 is an integrated system where controller algorithms, distributed I/O drivers, alarm management, operator faceplates, and historical archiving are designed simultaneously. Licensing is structured around functional plant equipment: each automated device or control loop is treated as a unified Process Object (1 Equipment Entity = 1 PO).

Process Object (PO) Counting Rules in SIMATIC PCS 7

In SIMATIC PCS 7:
* What Constitutes 1 Process Object?:
Any CFC block or SFC sequencer that communicates with the operator station and fulfills all of the following conditions:
1. Possesses Operator Control and Monitoring capability (S7_m_c := 'true').
2. Generates WinCC alarms via Alarm_8P / Notify_8P.
3. Provides an integrated faceplate or block icon.
* The High-Density Advantage:
Consider an APL motor block (MotL FB1850):
* Internal controller variables: ~80 parameters.
* WinCC communication tags: ~30 structure elements.
* Alarm messages: 16 individual alarm states.
* License Consumption: Exactly 1 AS RT PO and 1 OS RT PO.

WinCC SCADA PowerTag Licensing Mechanics

In standalone WinCC SCADA (6AV6381-2BM07-4AX0):
* Counting Criteria:
Only external process tags with a direct communication connection to a PLC are counted. Internal tags, system variables (@...), and script variables do not consume PowerTag licenses.
* The Multiplicative Effect:
Controlling that exact same motor (MotL) in standalone WinCC requires mapping the start command, stop command, run feedback, trip alarm, speed setpoint, and fault codes as separate variables. The single motor consumes 8 to 15 PowerTags.

Comparison Table: Process Objects (PO) vs SCADA PowerTags

The table below summarizes the core differences between PO and PowerTag models:

Architectural MetricSIMATIC PCS 7 Process Object (PO)Standalone WinCC PowerTagSystem PhilosophyIntegrated DCS (Equipment Centric)Open SCADA (Variable Centric)Licensing UnitFunctional Control Module / BlockSingle Communication VariableTypical I/O / Tag Ratio1 PO represents 10 to 40 individual tags1 Tag represents exactly 1 scalar variableLicense LocationSEC Card (AS) & Automation License Manager (OS)Automation License Manager on PC StationRedundancy ImpactAS: 1 PO license per redundant pair; OS: licensed per serverLicensed per individual server stationAlarms Included?Yes, unlimited embedded Alarm_8P messagesAlarms count toward overall WinCC tag limits

Calculating License Consumption in Installed PCS 7 Engineering Stations

Engineers can verify actual license consumption directly within SIMATIC Manager:
1. AS Process Object Utilization:
* Open the Multiproject in SIMATIC Manager.
* Select the AS project or chart folder.
* Navigate to Options -> Charts -> Process Objects -> Displayed Process Objects.
* The dialog displays total configured POs versus available AS RT PO licenses and SEC capacity.
2. OS Process Object Utilization:
* Select the OS Server object.
* Open Options -> OS -> Process Objects.
* Compare utilized OS POs against the installed WinCC RT PO license package (e.g., 2,000 PO 6ES7658-2CX58-0YB5).

Verification

To verify system licensing compliance:
1. Open Automation License Manager (ALM) on the Engineering Station and OS Servers.
2. Verify that PCS 7 AS RT PO and PCS 7 OS RT PO license keys display a status of Valid with sufficient available balance.
3. On the AS controller, open Module Information (Ctrl+D) -> System Expansion Card tab. Confirm that configured POs do not exceed authorized SEC capacity.
4. Verify that WinCC Runtime activates without triggering license shortage warning banners.

Limitations and Operational Precautions

Never Infer Licenses from I/O Counts: Estimating licensing solely from physical hardware I/O count leads to severe under-licensing. Complex software blocks (e.g., totalizers, calculations, splitters) with OCM capabilities consume Process Objects even if they do not wire directly to physical I/O.
SFC Chart Licensing: In PCS 7, each instantiated SFC Chart consumes 1 Process Object. SFC Types consume 1 PO per instance.
Commercial Accuracy Disclaimer: Final license quantities, AS/OS RT PO packages (6ES7658-2CX58-0YB5), and WinCC PowerTag MLFBs must be validated against the applicable Siemens catalog and authorized distributor quotation.