Presentation of ULP System Architectures

Introduction

The ULP system architecture is defined by the way in which the Ethernet or Modbus-SL network interconnects the intelligent modular units (IMUs).

The various possible ULP system connections define five architectures.

Standalone architecture: the IMUs are not communicating to communication interfaces (IFE, EIFE, or IFM interfaces).
Centralized Modbus architecture: the IMUs are communicating to communication interfaces (IFE servers and IFM interfaces). The IFE servers and IFM interfaces are grouped in islands, mounted side-by-side on a DIN rail and interconnected by the stacking accessory.
Distributed Modbus architecture: the IMUs are communicating to IFM interfaces. The IFM interfaces are distributed as close as possible to the ULP modules in the IMU and linked by the Modbus cable.

There are two possible configurations for the distributed Modbus architecture:
- Daisy-chained distributed Modbus architecture
- Tap-linked distributed Modbus architecture
Both these distributed architectures can be combined to form a mixed architecture.
Daisy-chained Ethernet architecture: the IMUs are communicating to IFE or EIFE interfaces. The IFE and EIFE interfaces are distributed as close as possible to the ULP modules in the IMU and linked by the Ethernet cable.
Star Ethernet architecture: the IMUs are communicating to IFE or EIFE interfaces. The IFE or EIFE interfaces are distributed as close as possible to the ULP modules in the IMU and linked by the Ethernet cable to the switch.

The distributed and centralized architectures can be combined to adapt to the electrical installation and its restrictions.

The ULP system architectures follow rules for building low-voltage switchboards in compliance with IEC 61439-1 and IEC 61439-2 standards.

Choice of Architecture

The following table lists the advantages and disadvantages of ULP system architectures:

Architecture	Advantages	Disadvantages
Centralized Modbus	Ease of wiring due to the stacking accessory. Ease of maintenance due to the grouping of IFM interfaces in the islands. Option of connecting other Modbus devices through tap links, on the unused connectors of IFM interfaces in the islands. Minimized Modbus cable length. IFM interfaces could be stacked to an IFE server to get Modbus data through Ethernet.	Need for a dedicated place in the cubicle where the IFM interfaces can be grouped.
Daisy-chained distributed Modbus	No need for a dedicated place in the cubicle where the IFM interfaces can be grouped.	Additional wiring needed for daisy-chaining the Modbus cable between the IFM interfaces. Longer Modbus cable. Space taken up in the cubicle by the upstream Modbus cables and downstream ULP cords.
Tap-linked distributed Modbus	No need for a dedicated place in the cubicle where the IFM interfaces can be grouped. Ease of wiring by using a Modbus splitter block: up to eight IFM interfaces installed in several cubicles and connected to one Modbus splitter block.	Additional wiring needed for daisy-chaining the Modbus cable between the IFM interfaces. In the case of an architecture with shunt terminal block, need for a shunt terminal block at the top of each cubicle.
Daisy-chained Ethernet	Ease of wiring by using only an Ethernet cable. Plug-and-play. No need for a dedicated place in the cubicle.	Additional wiring needed for daisy-chaining the Ethernet cable between the IFE or EIFE interfaces. Long Ethernet cable. Space taken up in the cubicle by the upstream Ethernet cables and downstream ULP cords. Need two Ethernet ports (like on the IFE interface). Dependability in case of device detected failure.
Star Ethernet	Dependability in case of device detected failure. Ease of wiring by using only an Ethernet cable. Plug-and-play. No need for a dedicated place in the cubicle. Need only one Ethernet port.	Long cables and space taken by Ethernet cables in the cubicle. Space taken up in the cubicle upstream by the Ethernet cables and downstream by the RJ45 plug/plug ULP cords.