11
IDM T5 DAU Rear
All analog channels are calibrated in the factory and there is no
need for site adjustments. The DAU configuration sheet
provided at the back of this manual will list the calibration
details of each analog channel.
Each analog channel is fully isolated from each other and to
earth. The following also applies:
# Accuracy of reading better than 0.5% of full scale
# Phase angle error better than 0.5 degrees
# Common mode rejection ratio better than 85dB
Where a DAU is supplied with a combination of current and
voltage channels always ensure that the selected input channel is
a current channel before connecting a CT circuit.
Event / Digital Inputs (Standard)
Each DAU is fitted with 32 digital inputs. The digital input
sensitivity can be 24V, 48/125V or 220Vdc with a tolerance of
±20%. The DAU configuration sheet gives the digital input
details.
The purpose of the digital inputs is to monitor the state of
external contacts normally associated with protection relays and
plant.
The digital input connections are via a screw terminal adapter
block that plugs into
#1TB5. Event inputs are on terminals 1 - 8
with the common or neutral on terminal 9. Terminal 10 is earth
and should be connected to the system star earth.
This arrangement makes it easy to
change a complete DAU without
having to disconnect a large number of
wires.
An external DC wetting voltage is
required to operate the digital inputs.
This voltage is normally from the
station battery.
A DC voltage (in the correct range)
applied across an input is interpreted
as a closed contact while the absence
of voltage is interpreted as an open
contact. The current drawn by each
input, when rated voltage is applied is
approximately 1mA.
The digital inputs are arranged in
groups of eight with one common
connection. The digital inputs are
bipolar meaning that the switch wires
and common can be either plus and
minus or minus and plus respectively.
Each group of eight digital inputs is isolated from each other
and from earth.
Alarm Outputs
Each DAU is fitted with Alarm 1 and 2 on #1TB7. Each alarm is
in the form of a voltage free contact rated as follows:
# 125VA, 150W
The alarm output connections are via a screw terminal adapter
block that plugs into
#1TB7.
Alarm 1 (terminals 1 and 2) is an energised closed watchdog
alarm that opens when the DAU is switched off or when a
critical alarm occurs in the system.
Alarm 2 (terminals 3 and 4) is a fleeting alarm which is closed
for 250ms every time the DAU is triggered.
Terminal 6 is earth and should be connected to the system star
earth.
Ethernet Connections
There are two types of ethernet connection, a 10Base-T and a
10Base-FL. Both operate at a speed of 10Mbits/sec.
The 10Base-T connection is via the RJ45 socket and is used for
short range communication over standard twisted pair cables.
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