GE DGP Instruction Manual page 19

1 PRODUCT DESCRIPTION
1.4 OTHER FEATURES
The DGP system takes eight current and four voltage inputs (refer to Section 1.5: ELEMENTARY DIAGRAMS).
The input currents in terminals BH1, BH3, and BH5 (I
and 51V. As noted in the elementary diagrams, these currents can be derived from system side or neutral side
CTs as desired. Either the system or neutral side CTs can be used for these functions if the Stator Differential
(87G) function is enabled.
The current inputs I and I
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not require dedicated neutral CTs. Zero-sequence current at system and/or neutral side of the generator stator
windings is calculated and then compared with the measured I
background self-test.
The I current is used to process the 51GN function (not available on DGP***AAA models). If desired, a ded-
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icated neutral CT can be used for the input I
The DGP phase voltage inputs can be wye or delta and are derived from the generator terminal voltage. V
derived from the generator neutral grounding transformer.
A time synchronizing signal can be connected to the DGP for synchronization to within 1 ms of a reference
clock. Either IRIG-B or GE's G-NET system signal can be used. This signal is required only if it is necessary to
synchronize the DGP to an external reference clock.
Six digital inputs can be connected to the DGP. Two of these inputs (DI3 and DI4) are assigned for possible
routing of external trip/alarm signals to take advantage of the output configuration or sequence-of-events capa-
bility. Generator off-line (DI1), turbine inlet-valve-close indication (DI2), and external VTFF (DI6) inputs are
used for various relay logic functions. A contact input, (DI5), can also be used to trigger the optional oscillogra-
phy feature. In some models, the DI6 input can be configured as external VTFF or DISABLE ALL PROTEC-
TION (refer to Section 1.5: ELEMENTARY DIAGRAMS for details).
The digital input circuits are universally rated for nominal control voltages of 48 to 250 V DC.
The DGP system includes eight user-configurable output relays. Four of these relays (94G, 94G1, 94G2 and
94G3) are high speed (4 ms) trip-duty rated with two form A contacts each. The remaining four (74A, 74B, 74C
and 74D) are standard speed (8 ms) with one form C contact each, intended for alarms. Each of the protection
functions can be configured to operate any number of these output relays. The trip outputs are intended for, but
not limited to, the following purposes:
• 94G: trip a lockout relay to shut down the machine
• 94G1: trip field breaker
• 94G2: trip main generator breaker or breakers
• 94G3: operate a lockout relay to trip turbine.
In addition to the configurable output relays, five pre-defined alarm duty relays with one form C contact each
are included. These alarm relays include critical and non-critical self-test alarms (74CR and 74NC), the VTFF
alarm (74FF), and loss of power-supply alarms (PS1 and PS2). The form C contact of each of the alarm relays,
except PS1 and PS2, are wired out to the terminal block. A hard wire jumper is used to select either the form A
or the form B contact of each of the PS1 and PS2 relays, as shown in Figure 3–3: DGP POWER SUPPLY
MODULE on page 3–4.
All alarm relays, with the exception of 74CR, PS1 and PS2, are energized when the appropriate alarm condi-
tions exist. Relays 74CR, PS1 and PS2, however, are energized under normal conditions and will drop out
when the alarm conditions exist.
GE Power Management
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are derived from the residual connections of the respective phase CTs and do
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.
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DGP Digital Generator Protection System
, I , and I ) are used to process functions 46, 40, 32,
BS CS
and/or I values by the DGP as a part of the
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1.4 OTHER FEATURES
1.4.1 INPUTS
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1.4.2 OUTPUT RELAYS
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