Default monitoring signals of earth fault monitoring relay ([S90.1 and S90.2],
oQ987 and +2Q987)
The diagram below shows the monitoring signals for a one relay system (Q988).
The table below contains the descriptions. It also lists the terminal markings for the second
relay in a two-relay system (2Q988).
5
6
DOOR
-A90.1
Alarm 1
11
12
14
Alarm 2
21
22
24
A1
A2
-K91.1
X1
X2
-S90.1
9
-X90
10
7
8
12
11
14
-F92.1
12
11
14
-K91.1
24 V
3
1
2
4
Earth fault monitoring relay [S90.1]
A90.1
Measuring circuit status alarm (energized when the monitoring relay is energized). For a two-relay system
(2Q987), the alarm of the second relay is connected to X90:15/16.
1
Insulation level alarm 1. For a two-relay system (2Q987), the alarm 1 of the second relay is
connected to X90:17/18.
2
Insulation level alarm 2. For a two-relay system (2Q987), the alarm 2 of the second relay is
connected to X90:19/20.
3
User connections and user-defined monitoring circuit (dashed lines). The design varies. See the delivery-
specific circuit diagrams for the actual connections.
4
Monitoring signals of current transducer relays ([B353.11] ... [B353.14], oG353
and +2G353)
See the delivery-specific circuit diagrams. ([B353.11], etc. G353, +2G353)
Electrical installation 35
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