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1.1
INTRODUCTION
The MDAR relay assembly (Figure 1-1) is a digital
transmission line protection system, with three
zones of distance protection. All measurements and
logic are performed by digital means, using a micro-
processor. Self-checking and line monitoring tech-
niques are included. MDAR is primarily recommend-
ed for application on non-series compensated lines.
The non-pilot MDAR relay assembly is standard (see
Section 3); an optional pilot MDAR relay assembly is
also available (in Section 3).
1.2
MDAR 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
MDAR)
• Chassis - contains several modules (e.g., Micro-
processor 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 MDAR relay assembly consists of an outer-
chassis and an inner-chassis which slides into the
outer-chassis. The MDAR conforms to the follow-
ing dimensions and weight (see also Section 2):
• Height 7" (requires 4 rack units; 1.75" each)
• Width 19"
• Depth 13.6"
• Weight 35 Lbs
All of the relay circuitry, with the exception of the in-
put isolation transformers and first-line surge protec-
tion, 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 con-
nections, including a communication adaptor (see
Figure 4-1). Two FT-14 switches may be included,
as options, 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.
(5/92)
Section 1. PRODUCT DESCRIPTION
1.3
The inner and outer chassis, together, contain 6
standard modules, plus the option module for single
pole trip applications (see Figure 1-2). The Back-
plate is connected to the Backplane module (outer
chassis). The remaining modules are attached to the
inner chassis:
•
•
•
•
•
•
Circuit descriptions for each module, may be found
in Appendices A thru G, in accordance with the list in
the Preface to this document (see "Contents of Re-
lay System").
1.3.1 Backplane Module
The Backplane Assembly includes three voltage
transformers, four current transformers, two filter
chokes and several surge protection capacitors.
The Backplane Module (see Appendix A) receives
all external connections (with or without the FT-14
switch option), and connects directly to the Intercon-
nect module, thru plug-in connectors (J11, J12, J13)
which provide the connection between outer and in-
ner chassis.
The female parts of the connectors are mounted on
the Backplane module, which is part of the outer
chassis. The male parts of the connectors are
mounted on the Interconnect module, which is part
of the inner chassis.
The INCOM
mounted on the Backplate of the outer chassis and
is connected to the Backplane module.
MDAR MODULES
Interconnect module
Option module
Filter module
Microprocessor module
Display module
Power Supply module
®
or RS232 PONI
®
1. "INCOM
"stands
COMmunications.
The
stands for Product Operated Network Inter-
face.
I.L. 40-385.1B
1
(see Figure 1-3) is
for
INtegrated
"PONI"
acronym
1-1
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