Siemens UL 489, UL1066 CubicleBUS, Communications Capability of the Electronic Trip Units ETUs

Communication-capable Circuit Breakers

WL Circuit Breaker

The ability to change between two different parameter sets is also possible. This function is particularly useful in the event of a power failure when an automatic transfer is made from utility to generator power, a process which can involve changing many of the trip unit parameters.

A wide range of lock-out systems are available to improve reliability during critical processes. All accessories, such as shunt trips, motor operators and communication components, can be installed quickly and easily; this is made easier because the accessories are identical across the entire product line. The commitment to reducing the overall number of parts results in fewer spares to be ordered and lower inventory costs.

The heart of each circuit breaker is the electronic trip unit (ETU). Several versions are available to adapt the protective, metering, and alarm functions to the system requirements: from simple overload and short-circuit protection to trip units that can be configured remotely and which feature a wide range of metering and alarm functions.

All circuit breakers with ETU745, ETU748, ETU755 and ETU776 trip units are communications capable, and allow additional components to be internally networked via the CubicleBUS.

The circuit breaker is connected to MODBUS via the RS485 interface on the COM16 module.

The breaker data adapter (BDA) (see Chapter 4) also supports higher-level networking/ communication (Intranet/Internet).

The CubicleBUS

The CubicleBUS, which connects all the intelligent components within the WL Circuit Breaker and enables additional external components to be connected quickly and reliably, forms the backbone of the modular architecture of the WL. The CubicleBUS is already integrated in and connected to all assembled circuit breakers with the ETU745, ETU748, ETU755, and ETU776 trip units.

The high level of system modularity enables communication functions (e.g. metering function) to be retrofitted at any time. A WL Circuit Breaker that is not communications capable can be upgraded (e.g. by exchanging ETU725 for ETU745 with CubicleBUS) quickly and easily on site. All CubicleBUS modules can access the existing data of the circuit breaker directly, thereby ensuring rapid access to information and speedy responses to events.

By connecting additional, external modules to the CubicleBUS, cost- effective solutions for communicating data from other devices in the cubicle can be implemented.

Communications Capability of the Electronic Trip Units (ETUs)

The electronic trip units ETU745, ETU748, ETU755, and ETU776 are all communications capable. The CubicleBUS is connected to the circuit breaker terminals X8.1(-) to X8.4(+)

Different versions of communications-capable trip units are available.

The front of the ETU745 has rotary switches for setting protective parameters. These can be read via the communication device. The ETU745 can also be installed with a four-line display for the measured values.

The ETU755 does not have rotary switches or a display. The protective parameters can only be changed via communications. This trip unit with remote-only parameter setting is for special application demands.

The ETU776 features a graphical display with a clearly structured, key-driven menu. This not only enables operators to display measured values, status information, and maintenance information, but also to read all the existing parameters and make password-protected changes.

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WL MODBUS Communication and Electronic Accessories • January 2005