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Installation, Operation and Maintenance
Introduction
The REL 356 relay assembly is a numerical (fully digital) current differential transmission line protection system, with
optional distance back-up protection and digital fault recording capability. The following communication options are
provided:
• 9600 bps Audio tone
• 56/64 kbps Digital communication
REL 356 Construction
The standard nomenclature for ABB relay protection equipment is as follows:
• Cabinet – contains fixed-racks, swing-racks, or open racks
• Rack – contains one or more chassis (e.g., the REL 356)
• Chassis – contains several modules (e.g., Microprocessor or Power Supply)
• Module – contains a number of functional circuits (on printed circuit board)
• Circuit – a complete function on a printed circuit board (e.g., analog-to-digital conversion)
• The REL 356 relay assembly consists of an outer-chassis and an inner-chassis which slides into the outer-
chassis. The REL 356 conforms to the following dimensions and weight:
• Height 7" (requires 4 rack units @ 1.75" each); 177 mm
• Width 19"; 483 mm
• Depth 13.6"; 345 mm
• Weight 38 Lbs; 17.5 kg
All of the relay circuitry, with the exception of the input isolation transformers and first-line surge protection, are mounted
on the inner chassis, to which the front panel is attached. The outer chassis has a Backplate, which is a receptacle for
all external connections, including Digital Communication Interface. Two optional FT-14 switches are mounted in the two
peripheral areas of the outer chassis. The FT-14 switches permit convenient and safe disconnection of trip, ac and dc
input circuits, and provide for injection of test signals.
REL 356 Modules
The inner and outer chassis, together, contain standard modules, plus the optional relay output. The Backplane module
and Digital Communication Interface (DCI) are connected to the Backplate (outer chassis). The remaining modules are
attached to the inner chassis:
• Interconnect module
• Relay Output module
• Contact Input module
• Microprocessor module
Installation, Operation and Maintenance
ABB REL 356 Current Differential Protection
2-1
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