Woodward EGCP-2 - Figure 3-6. Four Wire WYE PT Connection

EGCP-2 Engine Generator Control Package Manual 26076
18 Woodward
42
43
44
45
46
47
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+
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EGCP-2
VIS-055a
00-10-17
A
B
C
N
N
A
N
B
N
C
N
N
N
Figure 3-6. Four Wire WYE PT Connection
Utility (Mains) and Plant Bus PT Input Wiring
The EGCP-2 utilizes one PT input to sense both utility tie-line voltage and plant-
bus voltage. This PT input should be the same configuration as the generator PT
input. The potential transformer should be the same ratio as the generator PT
input. Two Relay outputs are used by the EGCP-2 to select which voltage source
to monitor, depending upon the state of the control. The EGCP-2’s control logic
is set up to monitor the utility tie voltage during normal operation and local bus
voltage when sensing for a dead bus condition or synchronizing the generator to
the local bus. Refer to figures 3-7, 3-8a and b, for required input wiring
configurations. This type of configuration allows the EGCP-2 to perform a break-
before-make relay action when switching between voltage sources to assure that
the utility PT and Bus PT never are connected.
Sequence of Mains PT Disconnect (DO8) and Local Bus PT Connect (DO7)
The EGCP-2 will command a Mains PT disconnect (DO8) when:
1. The EGCP-2 has an “AUTO” discrete input and either
a. A loss of Mains (LOM) is detected or
b. A “Run with load” discrete input.
2. The Generator Stable Delay time has been met.
3. The EGCP-2 is in the “Close Gen Breaker” mode.
When the Mains PT Disconnect changes state, the EGCP-2 has to measure less
than 40 Vac on the Mains/Bus PT input (terminals 40 and 41). If the EGCP-2
measures greater than 40 Vac after the Mains PT Disconnect command was
given, the EGCP-2 senses this as a fault and will not synchronize.
For this reason, when only one PT signal is being connected, the external relay
logic to remove the incoming Mains/Bus PT signal must still be applied (Figure
3-8a).