L2234
L2778
Emax
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Model
Scale
Page No.
Doc. No.
Apparatus
1SDH000460R0002
12.1 Standard
The PR121/P has been designed to work in accordance with the following international standard:
IEC 60947-2 Low voltage apparatus. Circuit-breakers.
12.2 Specifications
12.2.1 General
The PR121/P unit is a high-performance self-supplied protection unit with
Protection
functions for the ABB SACE 'Emax' range of 3-pole and 4-
pole low voltage air circuit-breakers. The unit's user interface also enables parameter setup and complete pre-alarm and alarm management with
LED warning/alarm indicators for the protection and watchdog functions.
Depending on the version, the protections available are as follows:
Symbol
Protection against
L
overload with inverse long time delay
S
short-circuit with adjustable delay
I
instantaneous short-circuit
G
earth fault with adjustable delay
The PR121/P can be installed on 3-pole CBs with and without an external neutral, or on 4-pole CBs.
It should be noted that the reference current for the PR121/P is the In (the rated current defined by the Rating Plug) and not the Iu (the uninterrupted
rated current of the CB itself).
Example: the CB E1B800 with a 400A Rating Plug has an Iu of 800A and an In of 400A.
The unit opens the circuit-breaker in which it is installed by means of the TC, which takes effect directly on the device's mechanical leverism.
The unit is made using digital microprocessor technology and interfaces with the user by means of DIP switches. The unit's protection parameters
and general operating mode can be set entirely by the user.
12.2.2 Electrical characteristics
Rated operating frequency
50/60 Hz ±10%
Pass band
3000 Hz max
Peak factor
6.3 max @ 2 In
MTBF (MIL-HDBK-217E)
15 years @ 45°C
12.2.2.1
Self-supply
The unit requires no outside power source for the protection and alarm signal functions. It is self-supplied by the current sensors installed on the
circuit-breaker. For it to function, it simply needs the current defined below to be flowing in at least one phase. An outside power source can, however,
be connected to enable other functions and particularly for its connection to the separate devices: HMI030 and PR021/K.
The characteristics of the busbar current are given in the table below:
Characteristics
Relay Enabling
E1...E3
E4...E6
Three-phase minimum busbar current for enabling relay (LED alive and full relay operation)
>70 A
>140 A
12. SACE PR121/P Release - Identification
The PR121/P units available, in accordance with the IEC Standards, with the various default and optional protections and modules, are illustrated
in the figure below:
PR121/P
PR121/P
PR121/P
Protections
Optional modules available
BT030
PR030/B
12.2.2.2
Auxiliary power supply
The outside 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 3.5 mA.
