Interfacing S7-300 Gas Turbine Control Systems with SIMATIC PCS 7: CP 343-1, Industry Library, and Architecture Guidelines

To integrate an S7-300 gas turbine control system into an overall SIMATIC PCS 7 DCS, install an Ethernet Communications Processor (such as CP 343-1 Lean or CP 343-1 Advanced) in the S7-300 rack and configure an S7 Connection in NetPro to the PCS 7 S7-400 or CPU 410-5H. Use the SIMATIC PCS 7 Industry Library (IL) for S7-300 to provide native APL-lookalike faceplates, alarm handling, and operator control on the PCS 7 OS clients, or implement standard S7 communication blocks (BSEND/BRCV or PUT/GET) between the controllers.

Architectural Strategies for S7-300 Package Unit Integration

Gas turbine generator sets frequently arrive on site as vendor-packaged OEM units controlled by Siemens S7-300 or S7-300F fail-safe processors (such as CPU 317F-2 PN/DP). Plant owners running SIMATIC PCS 7 across their main process often mandate supervisory control, unified alarming, and unified HMI faceplates on the PCS 7 OS without introducing disjointed third-party HMIs.

Integrating an S7-300 package unit into PCS 7 can be accomplished through three primary architectures:

AS-to-AS Industrial Ethernet Coupling: An S7 connection is established between the S7-300 (via integrated PN port or CP 343-1) and the central PCS 7 S7-400 / CPU 410-5H. Process values and commands pass through the PCS 7 AS, which executes standard APL blocks and serves faceplates to the OS.
Direct OS Integration via SIMATIC PCS 7 Industry Library (IL): The S7-300 runs dedicated IL function blocks that support PCS 7 message generation (ALARM_8P emulation) and direct WinCC OS faceplate assignment.
OpenPCS 7 / OPC UA Gateway: The package unit is decoupled via an OPC server, suitable for loose monitoring but undesirable for high-speed gas turbine interlocks and time-stamped alarming.

Hardware Selection: CP 343-1 Lean vs CP 343-1 Advanced

When adding an Ethernet communications processor to an existing S7-300 rack:

CP 343-1 Lean (6GK7343-1CX10-0XE0): Provides basic S7 communication as a server only. It can respond to S7 queries initiated by the S7-400 (using PUT/GET or USEND/URCV configured in the S7-400), but cannot initiate S7 connections or execute client PUT/GET calls. It supports up to 8 S7 connections and 10/100 Mbit/s transmission.
CP 343-1 Advanced (6GK7343-1GX31-0XE0): Provides full S7 communication as both client and server, supports up to 16 S7 connections, PROFINET IO controller/device functionality, IP routing, and advanced security firewalls. For critical turbomachinery applications where the turbine controller must actively report trip statuses or initiate fail-safe handshakes, the CP 343-1 Advanced is required.

Software Architecture: Industry Library (IL) vs Custom S7 Blocks

The SIMATIC PCS 7 Industry Library offers engineering blocks specifically designed for S7-300 and TIA Portal controllers that mimic PCS 7 Advanced Process Library (APL) look, feel, and operating philosophy:

Industry Library for S7-300: Contains blocks such as L_MotL, L_VlvL, L_MonAn, and L_OpAn written in SCL optimized for S7-300 memory structures. These blocks create instance data blocks with s7_m_c attributes that compile directly into WinCC OS tags and generate standard APL-style faceplates.
Standard S7 Communication Blocks: If IL is not licensed, the S7-400 must call BSEND (FB12) / BRCV (FB13) or PUT (FB14) / GET (FB15) to transfer data records between DBs. The S7-400 then routes these variables into native APL driver and control blocks in CFC.

Configuring S7 Connection in NetPro and Station Cross-Coupling

To establish deterministic communication between the two controllers:

Add S7-300 Station to Multiproject: In SIMATIC Manager, incorporate the S7-300 station into the PCS 7 Multiproject or configure it as an 'Other Station' if maintained under a separate engineering umbrella.
Open NetPro and Configure Network: Connect both the S7-400 CP 443-1 (or internal CPU PN port) and the S7-300 CP 343-1 to the shared plant Ethernet subnet (Terminal Bus or Industrial Ethernet Plant Bus).
Insert S7 Connection: Select the S7-400 CPU, right-click, select Insert New Connection, choose the S7-300 station, and select S7 connection.
Configure Connection Properties: Assign Local and Partner Connection IDs (ID hex). Enable 'Establish an active connection' on the S7-400 side (especially if using CP 343-1 Lean).
Compile and Download: Save and compile network routing in NetPro. Download the configuration to both stations. Ensure no IP conflicts exist between the turbine control rack and DCS subnets.

Package Unit Integration Method Comparison

The following table compares architectural methods for integrating package units into PCS 7:

Integration MethodS7-300 Communication BlockPCS 7 Engineering EffortHMI Faceplate ConsistencyAlarm Time-Stamping PrecisionPCS 7 Industry LibraryIL Blocks (L_MotL, etc.)Low (OS compiler generates tags)High (Identical to PCS 7 APL)High (Integrated OS Alarming)S7-400 PUT / GETNone on S7-300 (Passive DB)Moderate (Manual CFC mapping)High (Via S7-400 APL proxies)Medium (Polling cycle dependent)BSEND / BRCVFB12 / FB13 in S7-300High (Handshake DB programming)High (Mapped into CFC blocks)High (Event-driven buffer exchange)Modbus TCP GatewayModbus Blocks / GatewayHigh (Register address mapping)Medium (Custom faceplates)Low (Polled registers without alarms)OPC UA / OpenPCS 7OPC Client / ServerModerate (Software gateway setup)Low (Generic WinCC controls)Low (Client-server scan jitter)

Verification

Verify the gas turbine integration using the following steps:

In NetPro, verify that the S7 connection status indicates 'Configured' offline and 'Established' online without link aborts.
Open the S7-400 diagnostic buffer and confirm no communication error OB calls (OB87 / OB122) occur during data exchange.
Verify that analog values (e.g., turbine RPM, exhaust gas temperature) update in CFC and on the OS client within 100 ms.
Test an emergency shutdown (ESD) or trip signal from the turbine controller and confirm that alarms register on the PCS 7 OS Alarm Logging screen with correct timestamp and priority.

Commercial Accuracy Disclaimer: Software order numbers (MLFBs), package structures, and hardware capacity prerequisites vary across PCS 7 versions and hardware platforms. System integrators must confirm exact software entitlements and licensing requirements against the official Siemens Catalog CA 01 and obtain an authorized Siemens distributor quotation prior to purchasing.

Limitations and Operational Precautions

Consider the following operational constraints:

Never Route Safety-Critical Trips Over Uncertified Networks: Critical turbine overspeed trips and emergency shutdown (ESD) functions must be executed directly in hardwired fail-safe I/O or via certified PROFIsafe connections, never across standard S7 Ethernet communication.
Communication Load Restrictions: S7-300 CPUs feature limited communication work memory compared to S7-400s; keep cyclic PUT/GET polling frequencies above 200 ms to avoid starving the turbine's internal execution cycle.
CP 343-1 Lean Server Limitation: Remember that CP 343-1 Lean cannot initiate S7 connections; the PCS 7 S7-400 or OS server must always act as the active connection partner.

Engineer FAQ

Can the S7-300 connect redundantly to both sub-racks of an S7-400H system?

A standard CP 343-1 does not support native redundant S7-400H 2-out-of-2 connections (fault-tolerant S7 connections). To achieve high availability, establish two independent S7 connections (one to CPU 0 and one to CPU 1) and manage switchover logic in the PLC program.

How does time synchronization operate between PCS 7 and the S7-300?

Configure SIMATIC Mode or NTP time synchronization on the CP 343-1 in HW Config so the S7-300 synchronizes its internal real-time clock directly from the PCS 7 plant bus master clock.

What happens if the communication cable between S7-300 and PCS 7 is severed?

The communication blocks assert connection fault flags (Error / STATUS). Logic in both controllers must detect this watchdog timeout and transition to a safe operational state or local autonomous control.