L6555
Emax
44/74
Doc. no.
Model
Apparatus
Scale
Page No
1SDH000460R0002
12.4.8.4. Trip curves for function G
t =
k
I
2
t = k
12.5. Main functions
12.5.1. Measurement
The current measuring (ammeter) function is available in all versions of the PR121/P unit.
This function is accessible by means of test unit BT030-USB, Ekip T&P (connected to a PC) and PR010/T, or by means of HMI030.
The measurement tolerance margins are:
Type of measurement Range of values measured by the relay
Standard operation range
Range Tolerance %
Phase and neutral current 0,05 ... 16 In 0,3 ... 6 In ± 1,5
Earth fault current 0,05 ... 4 In 0,3 ... 4 In ± 1,5
The relay allows the maximum current reading to be periodically recorded: this function must be enabled with test unit BT030-
USB or Ekip T&P, and requires auxiliary voltage.
12.5.2. Self-monitoring
The PR121/P unit provides certain self-monitoring functions that allow faults or setting errors to be identifi ed more easily. Faults
are signalled by a combination of led lights.
The functions are as follows:
Rating Plug validity.
Checks to fi nd out whether the current sensors (CS) are connected correctly.
Watchdog for proper connection of the Trip Coil (TC ).
Hw Trip protection. If activated, a CB opening command is transmitted through activation of the TC if sensors are disconnected
or if the Rating Plug is not connected/faulty. This function can be activated by means of test unit PR010/T, BT030-USB or Ekip
T&P.
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