System Assembly - ABB MDAR Instruction Manual

3.1 THE COMPLETE MDAR (REL-300) LINE
PROTECTION SYSTEM
The complete MDAR (REL-300) Line Protection Sys-
tem is housed in a 19-inch rack-mount package, 4
rack units (7 inches, 177.8 mm.) high, 19.0 inches
(482.6 mm.) width, 14.0 inches (356 mm.) depth,
weight 35 lbs. (16 kgs), as shown in Figure 1. It con-
sists of 6 basic and one optional modules. The 6
basic modules are backplane module, interconnect
module, power supply module, filter module, micro-
processor module and operator interface module. An
INCOM communication network interface or RS-
232C port provides remote data communication. The
two optional FT-14 switches are also available, as
shown in Figure 2.
For single-pole tripping applications, an optional sin-
gle-pole trip module is added with the extra relays for
tripping and BFI functions.
All user connections, including the serial data port for
communication, are on the rear panel. The front
panel presents controls and displays for the operator;
on either side are the (optional) type FT-14 test
switches. The test switches permit convenient and
safe disconnection of trip and ac input circuits, and
make it easy for the user to inject test signals.
An overall block diagram and the display panel of
MDAR (REL-300) relay are as shown in Figures 3
and 4, respectively.
3.2 BACKPLANE MODULE
The analog input circuitry consists of seven trans-
formers. Four currents (I
voltages (V , V and V
A B C
zero-sequence dual-polarizing ground current mea-
surement; the input is from the power transformer
neutral ct (Figure 5). The seven isolation transform-
ers are mounted on the transformer board which is
attached to the backplane module (Figure 2). They
drive resistive burdens to develop a secondary volt-
age which will be proportional to the primary input.
The current transformers are non-gapped. DC offset
attenuation is done with a digital filtering algorithm.
The first-line surge protection for each input and out-
put terminals are also located on the backplane mod-
Section 3. SYSTEM ASSEMBLY
, I , I , and I ) and three
A B C P
). The I input is used for
p
ule. The backplane module is mounted on the outer
chassis. All of the relay circuitry is located on the
other modules, mounted on the inner chassis, to
which the front panel is attached. The inner chassis
slides in or out of the outer chassis from the front.
The backplane module receives all external connec-
tions (with or without the FT-14 switch option), and
connects directly to the interconnect module, thru
plug-in connectors which provide the connection
between outer and inner chassis. Mating connectors
inside the case eliminate the need to disconnect
external wiring when the inner chassis is removed.
The INCOM or RS-232C PONI is mounted on the
Backplate of the outer chassis and is connected to
the Backplane module.
3.3 INTERCONNECT MODULE
The interconnect module becomes the floor of the
MDAR (REL-300) inner chassis: it provides electrical
connections from the backplane module to the other
modules. Two dc power fuses, two alarm relays (fail-
ure alarm AL1 and trip alarm AL2), and seven optical
isolation circuits are included on the interconnect
module in addition to the signal routing and connec-
tors to the other modules. The failure alarm relay AL1
is normally picked up, but the processor will deener-
gize it when a problem is found. The trip alarm relay
AL2 will be sealed-in if the AL2S is set to YES. Sta-
tus input information is interfaced to the microproces-
sor via seven optical isolators. They are:
• the status inputs from the breaker auxiliary con-
tact "52b",
• the pilot channel receiver output "RX1",
• the external "pilot enable" switch, (it is equiva-
lent to the 85CO device in a conventional pilot
system),
• the external target reset switch,
• the three status inputs, XTRIPA, XTRIPB and
XTRIPC, from the external trip circuits for SPT
application.
Terminals for these signal connections are located on
the rear panel of the outer chassis (Figure 6). The
input voltage level of these optical isolators can be
I.L. 40-385.5
3-1