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3.7.
TEST BOX
As an option, the bus differential protection may be provided with a testing element, whose aim is to
check the differential circuit operation (including the stabilization resistors) and the alarm and differential
units. These includes the following modules:
•
DAL: Alarm board (one per bar).
•
DDF: Differential boards (one per pole).
•
DRD: Differential output module (one per bar).
•
DDI: Differential unit input module (one per bar).
This element is provided with elements (latching relays: 3B/87) for the connection and disconnection of the
trip of the differential units (see drawing 22B6429F26).
The test box unit is housed in a 19" rack and consists of the following elements:
•
HLB100 (3B/87 in the schemes) latching relay (one for every differential). This relay inhibits the trips of
the corresponding differential units (see drawing 22B6429F26).
•
HLA100 (3P/87 in the schemes) auxiliary relays (one for every differential). This relay is in charge of
introducing the test current in the corresponding differential unit (see drawing 22B6429F16).
• DPR test module. This module is provided with the following elements:
•
Connection button (green color): This button operates on the HLB100 (3B/87) latching relay
allowing the trip output of the differential units.
•
Disconnection button (red color): This button operates on the HLB100 (3B/87) latching relay
•
Test button (white color): This button operates on the HLA100 (3P/87) auxiliary relay following
the below sequence:
a)
Disconnection of the trips of the differential unit through the HLB100 (3B/87) latching relay (if
connected), while memorising whether it was connected or disconnected. Trips from the
breaker failure logic are not disconnected.
b)
It blocks the reset of the HLB100 (3B/87) relay during the whole time the test is being carried
out and until all the elements which make up the trip circuits have been reset.
c)
It operates on the HLA100 (3P/87) relay introducing the test current in the differential circuit.
d)
When releasing the button, it carries out the opposite operation firstly disconnecting the test
current and connecting secondly (if it were memorised) the trips of the differential units, once
the trip circuits have been completely reset.
•
AL, DIF selector switch: It allows for selection between the differential unit test and the alarm
unit test.
•
Phase selector switch: It allows for selection of the phase to be tested.
•
Current level selector switch: It allows for selection of three different test current levels.
GEK-98514B
BUS1000 Busbar Protection
3. OPERATION PRINCIPLES
3.7.1. DESCRIPTION
3-7
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