Integrating IEC 61850 Protection Relays in SIMATIC PCS 7 Power Control - DBA Direct WinCC vs AS Block Architectures

In SIMATIC PCS 7 Power Control (PCL), integrating electrical protection relays (such as SIPROTEC 4 7SJ663 or SIPROTEC 5 7SJ8xx) using IEC 61850 .ICD/.SCL files can follow two fundamentally distinct architectural models: Direct WinCC Integration via Database Automation (DBA) using PC_FEEDER, or AS-Level Controller Integration using SG_FEEDER. The DBA tool automatically parses relay telemetry directly into WinCC tags and faceplates (PC_FEEDER) without generating CFC charts in the S7 controller. However, if the process automation logic requires external interlocks, load shedding, or trip coordination inside the S7-400 CPU, engineers must deploy the AS-based Switchgear library blocks (SG_FEEDER) in CFC, interfacing with the relay via Industrial Ethernet or PROFINET.

Architectural Models for IEC 61850 Integration in SIMATIC PCS 7

In modern process plants, electrical power distribution systems (medium voltage and low voltage switchgear) are tightly integrated with the distributed control system using SIMATIC PCS 7 Power Control (PCL).

Protection relays (e.g., Siemens SIPROTEC, ABB Relion, Schneider Sepam) communicate using the international standard IEC 61850:
1. Direct WinCC Integration (DBA Pathway):
- The relay connects directly across the industrial Ethernet network to an IEC 61850 OPC Server or WinCC Communication Channel.
- The Database Automation (DBA) tool imports the relay's ICD (IED Capability Description) file and generates WinCC tag structures, alarm messages, and faceplates automatically.
- Object Type: PC_FEEDER (Power Control Feeder).
- Characteristic: Bypasses the S7-400 CPU entirely; zero CPU memory or Process Objects (PO) consumed.
2. AS-Level Controller Integration (CFC Pathway):
- The relay communicates with the S7-400 or CPU 410 controller via PROFINET (using CiR/GSDML) or via an optical IEC 61850 gateway.
- The controller executes specialized technological blocks from the Power Control Library.
- Object Type: SG_FEEDER (Switchgear Feeder).
- Characteristic: Full programmatic access inside CFC for interlocking, load shedding, and safety trip matrixing.

Comparing PC_FEEDER (WinCC Direct) and SG_FEEDER (AS Block)

Understanding the functional distinction is crucial during FEED engineering:
- PC_FEEDER: A visualization-only technological type defined inside DBA and WinCC. It provides comprehensive operator faceplates displaying feeder status, breaker positions, voltages, currents, power factors, and protective trip logs. Because it exists solely in WinCC, it cannot participate in high-speed controller logic.
- SG_FEEDER: An APL-compliant Function Block instantiated inside S7-400 Continuous Function Charts (CFC). It processes raw binary and analog words from the physical breaker and relay, evaluates protective interlocks, handles operator commands from WinCC, and generates system alarms.

Integrating Relays via Database Automation (DBA) Tool

The Database Automation (DBA) utility automates HMI engineering for power devices:
1. In DBA, the engineer imports the device specification file (.ICD, .CID, or .SCD).
2. DBA maps standard IEC 61850 Logical Nodes (e.g., XCBR for circuit breakers, CSWI for switch controllers, MMXU for measurements) into pre-assembled WinCC composite tag types (PC_FEEDER).
3. DBA compiles the tag structure directly into the target WinCC OS project database.
4. When OS Compilation runs, WinCC graphic pictures automatically populate with feeder block icons.

Implementing Automation Interlocks with Direct WinCC Relays

If a relay was integrated via DBA (PC_FEEDER) but now requires interlocks from the PCS 7 controller (e.g., do not allow breaker close if process vent fan is stopped):

Option 1: Bi-Directional OPC Data Bridging

Configure an internal WinCC tag linked to the S7 controller via AS-OS compilation.
In WinCC, write a C or VBS script (or use WinCC Event scripting) that conditions the PC_FEEDER command button authorization on the state of the AS interlock tag.

Option 2: Hardwired Discrete Interlocking

Route physical 24VDC dry contacts between the S7-400 digital output module and the binary input terminals of the SIPROTEC protection relay. Configure the relay's internal CFC logic (in DIGSI) to enforce the interlock at the physical hardware layer.

Option 3: Migration to SG_FEEDER Architecture

Replace the direct WinCC connection with standard AS communication, instantiating the SG_FEEDER block in CFC to achieve native DCS interlocking.

Architectural Comparison Matrix: PCL Integration Pathways

The table below compares the two Power Control integration methodologies:

Technical FeaturePC_FEEDER (DBA Direct WinCC)SG_FEEDER (AS CFC Block)Primary ToolDatabase Automation (DBA)SIMATIC Manager / CFC EditorController CPU Impact0% (No memory or execution cycle)Consumes S7 Work Memory & POsCFC InterlockingNot natively possible (HMI layer only)Native, deterministic CFC interlocksTrip Speed50 ms - 200 ms (HMI polling)1 ms - 10 ms (Bus / GOOSE speed)Recommended Use CasePure electrical monitoring and SCADAIndustrial switchgear with process trips

Step-by-Step Procedure: Deploying IEC 61850 via DBA and CFC

To configure power integration properly:

Step 1: Export ICD File from DIGSI

In Siemens DIGSI (SIPROTEC engineering software), configure relay parameters and protection curves.
Select Export > IEC 61850 Device Description (.ICD).

Step 2: Import into DBA for Direct Visualization

Launch PCS 7 DBA.
Select File > Import Device... and choose the .ICD file.
In the mapping tree, assign the device type to PC_FEEDER.
Select Compilation > Compile to WinCC to generate WinCC tags and faceplates.

Step 3: Implement AS Blocks (If Interlocks Required)

If controller interlocking is needed, open SIMATIC Manager.
In the Master Data Library, locate the Power Control Library blocks (SG_FEEDER).
Place SG_FEEDER on the target CFC chart and interconnect process trip interlocks to input pins Intlock, Permit, and Protect.

Verification

To confirm proper operation of the IEC 61850 feeder integration:
1. DBA Compilation Status: In the DBA utility, confirm that the compilation log reports 0 errors and all Logical Nodes are mapped.
2. WinCC Faceplate Inspection: Open the WinCC OS runtime picture; click the feeder block icon and verify that the PC_FEEDER faceplate opens, displaying live three-phase voltage and current values.
3. Interlock Test: Simulate an active interlock condition in CFC or DIGSI; verify that the breaker close command is blocked on the operator faceplate with an actionable interlock tooltip.

Limitations and Operational Precautions

Engineering teams must observe the following precautions:
- Pure WinCC HMI scripting should never be relied upon for personnel safety or high-speed electrical protection interlocks; safety interlocks must execute in the controller or inside the relay.
- Always validate final license quantities and MLFBs against the applicable Siemens catalog and authorized distributor quotation when procuring SIMATIC PCS 7 Power Control packages.
- Ensure the IEC 61850 station subnet is isolated from general enterprise IT networks to prevent denial-of-service packet flooding on protection relay Ethernet ports.

Engineer FAQ

Can SIPROTEC 5 relays communicate directly with S7-410 via PROFINET?

Yes. Modern SIPROTEC 5 relays equipped with PROFINET communication modules support direct cyclic PROFINET IO communication to S7-410 controllers without requiring an intermediate IEC 61850 gateway.

Does PC_FEEDER consume PCS 7 OS Runtime Process Objects (PO)?

Yes. WinCC tags generated by DBA for PC_FEEDER objects consume standard WinCC OS Runtime tags or Process Objects depending on license configuration.

Where can I obtain the PCS 7 Power Control Library?

The SIMATIC PCS 7 Power Control Library is an official Siemens add-on package available for purchase through the Siemens Industry Mall, complete with AS blocks and WinCC faceplates.

Technical References

Related Tags

Power Control
IEC 61850
SIPROTEC
DBA
PC_FEEDER

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Integrating IEC 61850 Protection Relays in SIMATIC PCS 7 Power Control - DBA Direct WinCC vs AS Block Architectures