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3.3 XTM TEST PLUGS
3.3 XTM TEST PLUGS
The XTM test plugs are designed specifically for post-installation testing of the DGP system. As many as four
plugs can be used at one time: two XTM28L1 (left-hand plugs) and two XTM28R1 (right-hand plugs), each pro-
viding access to fourteen relay-side and fourteen system-side points. The system-side points are designated
"S" and the relay-side points are designated "R". The plugs are keyed by the contact finger arrangement so
that there can be no accidental interchange between the left-hand and right-hand plugs.
The plugs are fitted with a sliding handle that swings out to facilitate wiring to the terminals. The terminals con-
sist of #8 screws threaded into flat contact plates. The handles each have a tab on the outside edge to guide
the wire dress of the test leads.
Not all external connections to the DGP system are wired through the test receptacle.
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The test receptacle and connection plugs are located to the extreme left and right on the lower unit. The left-
hand plugs are labeled as TP1 with terminals 1 through 28. The right hand plugs are labeled TP2 with termi-
nals 1 through 28. These points are designated on the elementary diagrams as TP1-1 (see Section 1.5: ELE-
MENTARY DIAGRAMS on page 1–23). The left-hand test plug (XTM28L1) terminals are labeled 1R through
14R and 1S through 14S for the relay side and system side, respectively, with the system side labeled in red.
Similarly, the right-hand test plug (XTM28R1) terminals are labeled 15R through 28R and 15S through 28S.
Test-circuit connections, designated as TP points in the elementary diagrams, should be made to the relay side
of the test plug. Where it is desired to use available system quantities for testing (e.g. DC control power), jump-
ers may be inserted between the corresponding system-side and relay-side test plug terminals. Appropriate
precautions should be taken when working with station battery DC power. Connections should be made to the
test plugs prior to insertion into the DGP system.
It is critical that jumpers be inserted on the system-side test plug terminals that are connected
to the CT secondaries, as shown in Figure 1–9: ELEMENTARY DIAGRAM WITH TEST
BLOCKS, WYE VTs. If these jumpers are left out, the resulting high voltages will present a
CAUTION
serious hazard to personnel and may severely damage equipment.
To remove power from the relay, remove at least one of the connection plugs.
To insert the test plugs, the two connection plugs must first be removed. In so doing, electrical continuity is bro-
ken between the power system and the DGP for those signals that are wired through the test receptacle (refer
to TP points on the elementary diagrams in Section 1.5: ELEMENTARY DIAGRAMS on page 1–23). For the
terminals connected to the CT secondaries, shorting bars are included on the system side of the test recepta-
cle. These are clearly visible through the transparent plastic face plate on the receptacle. The shorting bars
make contact before the connection-plug contacts break during removal so that the CT secondaries are never
open-circuited.
Four test plugs may be inserted at the same time giving access to all 56 terminals simultaneously. Otherwise, if
using fewer than four test plugs, the remaining connection plugs may remain in the other receptacles.
When the test plugs are inserted into the receptacle, parts of the power system become isolated from the DGP.
Refer to the elementary diagrams in Section 1.5: ELEMENTARY DIAGRAMS on page 1–23 for the TP points
associated with each of the test plugs.
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DGP Digital Generator Protection System
3 HARDWARE DESCRIPTION
3.3.1 DESCRIPTION
3.3.2 TERMINAL DESIGNATION
3.3.3 XTM TEST-CIRCUIT CONNECTIONS
3.3.4 TEST PLUG INSERTION
GE Power Management
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