Sentron Power Manager OPC DA Integration with WinCC 7 SCADA

Overview

Siemens Sentron Power Manager 3.0 is delivered with a built-in OPC DA (Data Access) 2.0/3.0 server that exposes measured values gathered from SENTRON PAC multifunction meters (PAC3100, PAC3200, PAC4200, PAC4220) over Modbus TCP. The OPC DA server runs as an out-of-process COM service (OpcEnum + the Sentron-specific OPC server CLSID) on the configuration PC.

When the WinCC 7 SCADA runtime must consume those values from a different Windows host, the OPC DA contract requires either:

1. Both applications on the same workstation (in-proc / local COM),
2. A correctly configured DCOM link between the two workstations, or
3. A bypass using the native Modbus TCP driver of WinCC 7 against the PAC meters directly.

This reference covers all three paths, with emphasis on the DCOM-free Modbus TCP route that eliminates the entire OpcEnum / LaunchPermission / AccessPermission matrix that is otherwise mandatory for cross-machine OPC DA.

Prerequisites

Verify PAC reachability first with a Modbus poll tool before touching OPC:

If that returns a non-zero register, the meter is reachable and the OPC server is not required at all.

Architecture Comparison

For new installations, prefer Option C. Use Option A when consolidating hardware. Use Option B only when the meter is already aggregated inside Power Manager and that consolidation has business value.

Option A — Local OPC Server (Avoid DCOM Entirely)

Install the WinCC 7 SCADA runtime on the same physical or virtual machine that hosts Sentron Power Manager 3.x. With both processes in the same logon session, the OPC client (WinCC) and the OPC server (Power Manager) negotiate COM locally, so no DCOM is involved.

1. Install Sentron Power Manager 3.x and confirm the OPC DA service registers. Open Component Services → Computers → My Computer → DCOM Config and verify a Sentron-related application is listed.
2. Install WinCC 7 on the same host. Select the WinCC OPC channel component during setup.
3. In the WinCC Explorer, add a new OPC Channel → OPC DA connection. Browse the local computer; the Sentron Power Manager OPC server appears automatically.
4. Insert tags by browsing the server namespace or entering ItemIDs manually (ItemIDs in Sentron follow the form Channel.Device.Tag such as Line1.PAC4200.U_L1_N).

Option B — Remote OPC via DCOM (Two-PC Architecture)

When the topology mandates two PCs, configure DCOM end-to-end. The official Siemens procedure for the equivalent SIMATIC NET OPC server is documented in Siemens Support Entry 22033262 — "How do you get remote access to the SIMATIC NET OPC server?" The same procedure applies to the Sentron Power Manager OPC server, because it also exposes its COM object through OpcEnum on the same DCOM port range.

B.1 — Required Windows firewall and RPC ports

B.2 — DCOM configuration procedure

1. On the Power Manager PC, open dcomcnfg.exe.
2. Navigate to Component Services → Computers → My Computer → DCOM Config.
3. Locate the Sentron OPC server entry (right-click → Properties if the name is truncated; the CLSID is vendor-specific and can be confirmed with the Sentron 3.x installation log).
4. General tab: Authentication Level = Connect. Identity = Interactive User (single-user setup) or This User with a domain service account (recommended for unattended WinCC service).
5. Location tab: enable Run application on this computer.
6. Security tab:
   • Launch and Activation Permissions: add the WinCC service account, grant Local Launch, Remote Launch, Local Activation, Remote Activation.
   • Access Permissions: add the same account with Local Access and Remote Access.
   • Configuration Permissions: leave at defaults (Administrators).
7. On the WinCC PC, open dcomcnfg.exe and add the same account to Default Security tab (Access, Launch, Configuration) — required for the client side to launch the proxy.
8. Windows Firewall → Inbound Rules: enable Distributed Transaction Coordinator (RPC) and OPC Enumerator (OpcEnum) on both machines. The OpcEnum rules are not pre-installed; add custom rules for TCP 135 and the dynamic OPC range 5000-5020.
9. Restart the OPCEnum service on both machines: net stop OpcEnum && net start OpcEnum.

B.3 — Verify the COM link with OPC Scout

OPC Scout is shipped with SIMATIC NET and acts as a generic OPC DA client. It is useful to isolate whether a failure is on the DCOM layer or on the WinCC configuration layer.

1. On the WinCC PC, launch OPC Scout V10 (Start → SIMATIC → SIMATIC NET → OPC Scout).
2. Click Add Server → select the network computer name of the Power Manager PC.
3. If the Sentron server appears in the list, DCOM is working.
4. Add a group, drag tags from the namespace, observe the values refresh at the configured update rate (default 1000 ms for PAC).

If OPC Scout cannot enumerate the remote server, the issue is at the DCOM / RPC / firewall layer — not at WinCC. Do not touch WinCC until OPC Scout succeeds.

Option C — Direct Modbus TCP from WinCC 7 (Recommended)

WinCC 7 includes a native Modbus TCP channel driver that polls Modbus registers directly. The PAC meters expose all relevant values (voltage, current, power, energy, THD, status) as standard Modbus holding registers, documented in the PAC4200 Modbus address list.

C.1 — Verify the PAC Modbus map

Common PAC4200 registers (function code 0x03, holding registers, base address 1 in the manual):

C.2 — Configure the Modbus TCP channel in WinCC Explorer

1. Right-click Tag Management → Add New Driver → select MODBUS TCPIP.MODBUSTCP from the list (the channel is part of the standard WinCC 7 install).
2. Create a Connection per PAC meter. Properties:
   • IP address: 192.168.10.50 (example)
   • Port: 502
   • Station address (Modbus unit ID): 1
   • Timeout: 1500 ms
   • Update time: 1000 ms (do not go below 500 ms on PAC meters — the internal measurement cycle is 200 ms but averaging of the last 10 cycles limits useful throughput)
3. Add tags. Tag properties:
   • Data type: Float 32 IEEE 754 (for the scaled voltage / current / power values)
   • Address: register number in zero-based form expected by the WinCC driver (the WinCC MODBUSTCP driver addresses registers from 0; subtract 1 from the 1-based register number above; e.g. register 1 → address 0)
   • Length: 2 words (4 bytes) for Float32
   • Swap bytes / words: Yes (PAC sends big-endian / Modbus word order; WinCC expects little-endian word swap on Intel hosts)

WinCC 7 OPC Channel Configuration (when Option B is used)

1. In WinCC Explorer, Tag Management → Add New Driver → OPC.OPCDA.
2. Right-click OPC Groups → System Parameters: set the OPC server name to the Sentron Power Manager server exactly as it is registered (use the name from dcomcnfg, not the human-readable label).
3. Run the OPC Item Browser; if the channel cannot reach the server, the browser returns "Server not found" — that is a DCOM failure, not a configuration failure.
4. Add tags by dragging from the browser, or by manually entering the ItemID. The Sentron server uses a hierarchical ItemID structure: ChannelName.DeviceName.Measurement, e.g. SENTRON.PAC4200_1.VoltageL1N.
5. Set a sensible update rate (1000-2000 ms). The Sentron OPC server caches reads internally, so hammering at 100 ms only increases network traffic without improving accuracy.

Verification

Troubleshooting Matrix

Field-Proven Caveats

• Windows XP on the Power Manager PC forces NTLMv1 in some configurations; force NTLMv2 in Local Security Policy → Network security: LAN Manager authentication level on the XP host when interoperating with Windows 7.
• The Sentron Power Manager OPC server CLSID changes between major versions (3.0 vs 3.1). Hard-coding the CLSID in WinCC scripts breaks across upgrades; always reference the server by ProgID when scripting.
• When the PAC meter is on a managed switch port with energy-efficient Ethernet (EEE / 802.3az), Modbus TCP may drop connections on link-down events. Disable EEE on the switch port.
• WinCC 7.5 and later ship with the OPC UA channel as well, but the Sentron 3.x OPC server is OPC DA only. A bridge (such as a third-party DA-to-UA wrapper) is required if the SCADA side is OPC UA only.
• When four PAC meters are read by Sentron PM, do not exceed an aggregate poll interval of 250 ms inside Power Manager — the OPC server's internal cache cannot serve WinCC faster than that without dropping tags.

FAQ