ABB REF 542plus relay protection device
ABB REF 542plus is an advanced relay protection device that plays a critical role in ensuring the safe and stable operation of power equipment in
the power system. It can quickly and accurately detect various faults in the power system, such as short circuits, overloads, grounding faults, etc.,
and promptly issue alarm signals or perform tripping operations, isolate the fault area, prevent the expansion of the fault range,
minimize power outage time and economic losses, and is a solid guarantee for the reliable operation of the power system.
Safety information
Dangerous voltages can occur on the connectors, even though the auxiliary voltage has been disconnected.
Non-observance can result in death, personal injury or substantial property damage.
Only a competent electrician is allowed to carry out the electrical installation.
National and local electrical safety regulations must always be followed.
The frame of the device has to be carefully earthed.
The device contains components which are sensitive to electrostatic discharge.
Unnecessary touching of electronic components must therefore be avoided

General
REF 542plus is a Switchgear Multifunction Protection and Switchgear Control Unit and it is the further development of the former REF 542 multifunctional unit.
Like its predecessor, it features the following functions:
Protection
Measurement
Control
Monitoring and self diagnosis
Communication
All above-mentioned and also power quality functions are integrated into a programmable environment.
The exceptional flexibility and scalability of this new generation device lead to a smart solution where the traditional approach would be ineffective and expensive.
The following figures Fig. 3.-1 and Fig. 3.-2 show examples of the REF 542plus installation in several switchgears.
REF 542plus is composed of two parts: a base unit and a separate human machine interface (HMI). The base unit contains the power supply, the processor board, the analog input board and binary input and output (I/O) modules, as well as optional modules for supplementary functions.
The base unit and a HMI are connected with a serial cable.
The HMI is a stand-alone unit with its own power supply. It can be installed on the low voltage (LV) compartment door or in a dedicated compartment close to the central unit.
The HMI can be used to set the protection parameters to locally operate the switching devices in the switchgear and to visualize events and measurements.
A shielded, isolated twisted pair according to the RS-485 standard interface connects the HMI to the base unit. Fig. 3.-4 shows an installation of the central unit and the HMI Control Unit in the LV compartment of a switchboard for the switchgear.

REF 542plus is a real-time system. A digital signal processor (DSP) carries out the measurement and protection functions, and a micro controller (MC) the control functions.
Due to the task separation, there is no impact between the implemented protection scheme and the control scheme to be modified.
An optional communication processor (CP) is needed when connecting to a station automation
system.
A block diagram of the REF 542plus is shown in Fig. 3.-4.
The main module is equipped with the DSP and the MC. The CAN Open interface,the Ethernet interface for the embedded Web server, the optical input port for time synchronization are located on the main module as well.
The optional communication module takes care of the communication with the substation
automation system.
The binary input and output modules interface the primary process to send commands and to acquire status information.
The analog input module acquires the current and voltage signals, both from instrument transformers
or non-inductive sensors.
The optional analog 0/4 ... 20 mA output module and analog 4 ... 20 m A input module allow exchanging information with the 4 ... 20 mA or 0 ... 20 mA current loop.
This green LED is turned on when the unit is operational. This LED is switched off when there is no power supply or when the unit is not operational.
Network Communication LED
This LED is meaningful only when the REF 542plus is equipped with a communication module and configured to use it.
When a communication module is detected inside the unit, the LED turns on to green.
If a communication module is not detected or fails, the LED turns from green to red.
When the unit is not configured for the communication, the LED is switched off.
Alarm LED
The alarm LED turns to red when user-defined alarms become true. Several arbitrary alarm conditions can be defined and configured with the operating tool.
Alarm conditions can be a trip of a protection function, loss of SF6 in the circuit breaker and so on. When this LED is on, it is not possible to close the circuit breaker or to download a new configuration.
The alarm condition has to be removed and the alarm must be acknowledged first.
Interlocking Error
The interlocking error LED is usually green. The LED turns temporarily to red when the user attempts an operation that would violate the programmed interlocking conditions, for example switching a disconnector with the circuit breaker in closed position.