L3447
Emax DC
31/108
Model
Scale
Page No.
Doc. No.
Apparatus
1SDH000635R0002
L3728
12.2.2
Auxiliary power supply
The external auxiliary power supply is provided using a galvanically-separated power pack.
Since the auxiliary voltage needs to be isolated from the ground, "galvanically separated converters" in accordance with
the IEC standard 60950 (UL 1950) or the equivalent IEC 60364-41 and CEI 64-8 have to be used to guarantee a current in
common mode or leakage current (as defined in IEC 478/1 and CEI 22/3) no greater than 3.5mA.
The presence of the auxiliary power supply enables the relay unit to be used even with the circuit-breaker open, as well as powering all the modules.
The characteristics of the power pack are given in the table below:
Characteristics
Version PR122/DC
Auxiliary voltage
(galvanically separated)
24V DC ±20%
Maximum ripple
5%
Inrush current @ 24V
~10 A for 5ms
Rated power @ 24V
~5W
12.2.2.1
Powered by the PR120/V-PR120/LV module
For a full explanation of the features of the PR120/V-PR120/LV, see par. 14.1.
12.2.3 Environmental characteristics
Operating temperature
-25°C ... +70°C
Storage temperature
-40°C ... +90°C
Relative humidity
0% ... 98% with condensation
Degree of protection (with PR122/DC installed in the CB)
IP 30
12.2.4 Description of inputs/outputs
12.2.4.1
Binary inputs
–
K51/SZin:
Zone selectivity: input for protection S
(only with Vaux)
12.2.4.2
Binary outputs
–
K51/SZout:
Zone selectivity: output for protection S
(only with Vaux)
Note: These inputs/outputs should be used between PR122/PR123 series units only.
12.2.5 Communication bus
Local bus on rear connector; RS485 physical interface, Modbus protocol.
External system bus, RS485 physical interface, Modbus RTU protocol, baud rate 9600-19200 bps.
Test bus on front test connector.
12.2.6 Protection functions
The PR122/DC protection unit carries out 7 independent protection functions. In particular:
1.
Protection against overload with inverse time “
L
”;
2.
Protection against short-circuit with adjustable delay “
S
”;
3.
Protection against instantaneous short-circuit“
I
”;
4.
Protection against closing on short-circuit “
MCR
”;
5.
Protection against instantaneous short-circuit at high currents "
Iinst
";
6.
Protezione override con relè non alimentato;
7.
Protection against overtemperature “
OT
”.
A timing indication (m "alarm" LED) is provided on the unit's display, which is activated during a protection alarm. It is disabled when
the alarm condition ceases or when the protection has been tripped. When the circuit-breaker opens, the page with the "Trip" data is displayed
(when "i Test" is pressed, or automatically in the presence of Vaux).
12.2.6.1
Circuit-breaker state
The PR122/DC unit records the state of the circuit-breaker by means of specific wiring on the circuit-breaker. In the case where the presence
of current is determined with the circuit-breaker in the "OPEN" state, a state error is signaled by a warning message being displayed (see par.
12.6) and the "warning" LED lighting up.
The signal can be combined with a relay of the PR120/K module or with those of the PR021/K unit.
12.2.7 Measurement functions
The current measuring (ammeter) function is available on all versions of the SACE PR122/DC unit.
The display shows histograms with the currents of the polarity on the main page and in numerical form.
- Current;
- Instantaneous current values over a given time interval (data logger).
- Maintenance: number of operations, percentage of contact wear, opening data storage (latest 20 trips and 80 events).
- The protection records the historical data of the maximum current read.
12.2.8 Watchdog
The PR122/DC unit provides some watchdog functions able to guarantee the proper management of relay malfunctions. These functions are as
follows:
Watchdog for presence of Auxiliary power supply with "plug" icon displayed.
Rating PLUG validity.
Watchdog for proper connection of the Trip Coil (TC). If it is enabled,
any faults are indicated by a special alarm message and the "alarm" LED
coming on; if the PR120/D-M module is installed, this activates the coil opening command (YO), thus opening the CB.
Watchdog for protection of Hw Trip. If it is enabled, in the event of CB undefined or Rating Plug error or Installation error, a CB opening command
is given by the TC being enabled.