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Power supply
Auxiliary power
supply
Extension board
Communication unit
1.5
Measuring System
1.5.1
Input Signals
ZMD400xT
© Landis+Gyr AG
The supply voltages for the meter electronics are obtained from the three-
phase network, whereby the phase voltage can vary over the entire voltage
range without the supply voltage having to be adjusted. A voltage monitor
ensures correct operation and reliable data recovery in the event of a
power failure and correct restarting when the voltage is restored.
For medium or high-voltage applications in particular, the measuring volt-
age can be switched off. Since the meter normally obtains its supply from
the measuring voltage, it is also switched off and cannot be read. The aux-
iliary power supply connected in parallel with the normal power supply en-
sures operation of the meter free from interruption, so that it can be read at
any time. The auxiliary power supply is situated on an extension board.
The extension board is fitted inside the meter and is secured by the certifi-
cation seals. It cannot be exchanged. It can have the following components:
up to 4 control inputs in combination with
up to 6 output contacts (solid-state relays)
an auxiliary power supply
The communication unit for fitting only in the ZxD400xT meters is a com-
plete unit in its own case. If present, it is situated behind the front door, and
is therefore secured by a utility seal and can be exchanged or inserted in
the field if necessary. It contains:
Communication interfaces as required for remote readout of the meter
(e.g. CS, RS232, RS485, modem)
2 signal inputs (S0 interfaces) for processing external pulse transmit-
ters
Fig. 1.2
Block schematic diagram of measuring system
The meter has the analogue current values I1, I2 and I3 and analogue volt-
age values U1, U2 and U3 available as input signals.
Fig. 1.3
Type of measurement ZMD400xT
Since the ZMD400xT measures the individual phases mutually independ-
ently with one measuring element each, it can record the sum of the three
phases, the individual phases themselves, the phase angle between volt-
age and current as well as the angle between voltages U1–U2 and U1–U3.
D000030110 d – E650 Series 3 (ZMD400AT/CT, ZFD400AT/CT) – User Manual
Description of Unit
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