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ALPHA FIX Terminal Blocks
Screw Terminals
8WA measuring transformer terminals
11/37
Siemens ET A1 · 10/2008
11
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Overview
Measuring transformer terminals can be used for testing and
isolating circuits in switchgear installations, control rooms, etc.
without interrupting operation.
The isolating and instrument isolating terminals contain an isolat-
ing device in the through-type connection. The isolating device
permits electrical separation between the input and output of a
terminal.
Test sockets for plugs with a diameter of 4 mm can be screwed
into the front side of the through-type and isolating terminals.
The rated insulation voltage between colored test sockets is
125 V. The rated insulation voltage between test sockets and link
rails which are not connected to the terminal is 16 V (circuit 3,
terminals 3 and 5).
Two adjacent terminals can be connected in parallel with the dis-
connecting link. The disconnecting link can be operated in any
position of the isolating device.
Instrument set for one transformer
The instrument set for one transformer makes the basic circuit of
the transformer terminal blocks clear. This basic circuit is also in-
cluded in much larger instrument sets, which are extended by
adding on equivalent circuits. Links between the basic circuits
allow many kinds of tests to be carried out, parallel outgoing
feeders to other measuring instruments, the connection of test
equipment etc.
Instrument set for three transformers
The simplest version of an instrument set for a three-phase cir-
cuit consists of three basic circuits strung together without any
continuing links or extensions. Instead of isolating terminals 1, 3
and 5, less expensive through-type terminals can also be used.
On the other hand, it is also possible to use instrument isolating
terminals for this purpose so that the terminal versions are all the
same.
Instrument set for three transformers with neutral point
The instrument set with a neutral point is an extension of the pre-
vious circuit. Four instead of six lines are sufficient for connect-
ing it to the measuring instruments. The neutral point is pro-
duced on the measuring instruments on the one hand, and using
a shortened 8WA1 822-7VH10 link rail on the other. The instru-
ment isolating terminal 1 is connected to the neutral point using
a connection comb.
Note
The introduction of the 8WA1 011-1MH10 through-type terminals
and their associated disconnecting links has made it consider-
ably easier to configure terminal sets for current transformers.
Now, instead of the 12 isolating or instrument isolating terminals
used previously, only four instrument isolating terminals and
three through-type terminals are required.
Instrument set with test facility
This instrument set represents a significant enhancement over
previous types. In normal operation, terminals 2, 5 and 8 are
closed. For testing a measuring instrument (e.g. a plotter), these
terminals are opened and terminals 3, 6 and 9 are closed in or-
der to feed in a test signal. The transformers first have to be
short-circuited with the disconnecting links between terminals
1-2, 4-5 and 7-8. Wire bridges connect terminals 1, 4 and 7 with
the neutral point. It is formed in terminals 10, 11, 12 and 13 with
an 8WA1 887 link rail.
Connection possibility for measuring transformer terminals (instrument sets)
1
2
3
4
L
k l
1
2
L3
k l
1
2
k l
3
4
k l
5
6
L2
L1
L3
k l
1
2
k l
3
4
k l
5
6
L2
L1
7
N
L3
l
1
2
l
3
4
l
5
6
L2
L1
7
8
9
10
11
N
12
13
I2_14021
1
2
3
4
1 2 3
4
8WA1 011-1MH10
3
7
8WA1 011-1MH11
3
3 1
8WA1 011-1MH15
4
3
3 1
8WA1 825
a)
2 2
8WA1 885
3
8WA1 887
1
8WA1 822-7VH10
1
b)
8WA1 822-7VH01
3
3
3 1
8WA1 822-7PH00
4
8WA1 822-7VH22
1
Test socket
Link rail
Small partition
Disconnecting link (closed)
Connecting comb, 2-pole
b) Shortened
a) In some cases additionally required
between instrument sets
Type
Number required for
Instrument set for 1 transformer
Instrument set for 3 transformers
Instrument set for 3 transformers
with neutral point
Instrument set with testing facility
Test
© Siemens AG 2008
