GE DGP User manual

DGP
Digital Generator Protection Relay™
Instruction Manual
DGP Revisions:V210.12000P
V210.10000F
V211.32000J
V210.22000D
Manual P/N: GEK-100666D
Copyright © 2000 GE Power Management
GE Power Management
215 Anderson Avenue,Markham, Ontario
Canada L6E1B3
Tel:[phone]Fax:[phone]
Internet: http://www.GEindustrial.com/pm
All relays must be powered up at least once peryear
to avoid deterioration of electrolytic capacitors and
subsequent relay failure.
NOTE
Manufactured under an
ISO9002 Registered system.
g
GEPowerManagement

These instructions do not purport to cover all details or variations in equipment
nor provide for every possible contin
g
ency to be met in connection with
installation, operation, or maintenance. Should further information be desired
or should particular problems arise which are not covered sufficiently for the
purchaser’s purpose, the matter should be referred to the General Electric
Company.
To the extent required the products described herein meet applicable ANSI,
IEEE, and NEMA standards; but no such assurance is
g
iven with respect to
local codes and ordinances because they vary
g
reatly.

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.1 GETTING STARTED
1
1 PRODUCT DESCRIPTION 1.1 GETTING STARTED 1.1.1 UNPACKING THE RELAY
The following procedure describes how to unpack and setup the DGP.
1. Unpack and examine the DGP Digital Generator Protection relay. Ensure each module is properly seated
in the relay prior to applying power.
2. Apply rated DC power to the relay at the power supply input terminals. Refer to the appropriate elementary
diagram in Section 1.5: ELEMENTARY DIAGRAMS on page 1–23 for the location of these terminals. The
rated DC value (Vps) for the relay is found on the nameplate located inside the front cover on the right
side.
3. The DGP settings and control functions are protected by passwords on both MMI and remote access. The
relay is shipped with the factory default passwords that must be changed before any setting change or
control command can be executed (GE Modem Version only). The default passwords are listed below:
Note that the characters "." and "!" are part of the default passwords.
4. Instructions on how to use the keypad to change settings and put the relay into test mode can be found in
Section 4.3.2: SETTING CHANGES on page 4–3. Complete instructions on how to operate the keypad are
found in Section 8.3: KEYPAD on page 8–3.
5. To communicate with the relay from a PC, connect the relay to a serial port of an IBM compatible computer
with a DGP null-modem cable. Connection can be made either to the 25 pin D-connector on the back of
the relay (PL-1) or the 9 pin D-connector on the front (COM).
6. Refer to Figure 9–1: DGP COMMUNICATIONS WIRING on page 9–3 for the internal wiring of the cable.
7. GE-Link, the communications software required to access the relay from a PC, is included on the GE
Power Management Products CD or available from the GE Power Management web site at www.ge.com/
indsys/pm. Follow instructions in 10.1.3: INSTALLATION on page 10–1 to load GE-Link onto the PC.
8. To log into the relay, follow the instructions in Section 4.4: USING GE-LINK on page 4–5.
9. This instruction book describes functions available in DGP models with standard function groups A, B, and
C. Refer to the Nomenclature Selection Guide shown below to determine functions included in a specific
model.
MODE PASSWORD
MMI - SETTING 1234.
MMI - MASTER 5678.
REMOTE LINK - VIEW VIEW!
REMOTE LINK - SETTING SETT!
REMOTE LINK - CONTROL CTRL!

1-
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DGP Digital Generator Protection System GE Power Management
1.1 GETTING STARTED 1 PRODUCT DESCRIPTION
11.1.2 ORDER CODES & SELECTION GUIDE
Table 1–1: ORDER CODES
DGP


* * *

 
Base Unit DGP |||||| Base Unit
Current Rating 1||||| 1 Ampere Rated Current
5||||| 5 Ampere Rated Current
Power Supply 0|||| One Power Supply, 48 V DC
1|||| One Power Supply, 110 to 125 V DC
2|||| One Power Supply, 220 to 250 V DC
3|||| Two Power Supplies, 48 V DC
4|||| Two Power Supplies, 110 to 125 V DC
Test Blocks A| | | With Test Blocks
B| | | Without Test Blocks
Protocol A|| GE Modem Protocol
B|| Modbus RTU Protcol (DGP***BCA only)
Functions and
Features A|Functions and Features – see DGP selection guide below.
B|
C|
Revision ADGP Revision A Firmware
Table 1–2: DGP SELECTION GUIDE
FUNCTIONS & FEATURES ABC
Stator Differential 87G ✔✔✔
Current Unbalance 46 ✔✔✔
Loss of Excitation 40-1, 40-2 ✔✔✔
Anti-motorin
g
32 212
Overcurrent Volta
g
e Restraint 51V ✔✔✔
Stator Ground 64G1
c
✔✔✔
Stator Ground 64G2 d
✔-✔
Stator Ground 27TN e -✔✔
Neutral Overcurrent 51GN -✔✔
Overexcitation 24 (Volts/Hz) ✔✔✔
Overvoltage 59 ✔✔✔
Undervoltage 27 -✔✔
Underfrequency 81-U 424
Overfrequency 81-O 422
Accidental Engergization Logic ✔✔✔
Sequential Trip Logic ✔✔✔
Voltage Transformer Fuse Failure VTFF ✔✔✔
Oscillography Data Capture ✔✔✔
RS232 Communications Ports 222
Printer Output ✔-✔
IRIG-B Input ✔✔✔
DEC1000 compatible --
✔
c 64G1 is Fundamental Frequency Overvoltage, also known as 59GN
d 64G2 uses 3rd harmonic comparator algorithm for enhanced security
e 27TN is 3rd Harmonic Undervoltage supervised by an adjustable window of forward power.

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.1 GETTING STARTED
1
1.1.3 SPECIAL MODELS
In addition to the standard DGP model described by the order codes above, several special models are avail-
able. Some of these are shown below with a brief description.
DGP***AAA-0101 and DGP***AAA-0102
This model is similar to the standard DGP***AAA except for the following major changes:
• All digital inputs are rated for nominal voltage of 110 to 125 V DC instead of the standard 48 to 250 V DC
• The logic for function 51V is modified to remove fault detector supervision
• Seperate terminals are provided for the optional second power supply input
Refer to instruction book GEK-105552 for additional detail.
DGP***ABA-0005
This model is similar to the standard DGP***ABA except for the following major changes:
• Includes the Stator Ground 27TN function
• Includes oscillography data capture and IRIG-B input capabilities
• Suitable for application with 208 V AC nominal input
Refer to instruction book GEK-105587 for additional detail.
1.1.4 DEC 1000 CONTACT EXPANSION UNIT
The DEC 1000 is a relay expansion unit for the DGP consisting of five form C relays and six form A relays.
These contacts can be used for signalling or alarm purposes. Any protection function available in the compan-
ion DGP relay can be selected for DEC output relay assignment. The DEC 1000 is connected via the DGP
printer port PL2.
The DEC 1000 expansion unit is only compatible with the DGPkkkkkC units.
NOTE

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DGP Digital Generator Protection System GE Power Management
1.2 INTRODUCTION 1 PRODUCT DESCRIPTION
11.2 INTRODUCTION 1.2.1 GENERAL
The DGP Digital Generator Protection™ System is a microprocessor-based digital relay system that uses
waveform sampling of current and voltage inputs to provide protection, control and monitoring of generators.
These samples are used to compute current and voltage phasors that are used for the protection-function
algorithms. The DGP™ system uses a man-machine interface (MMI) and GE-Link software for local and
remote communication respectively.
This instruction book describes all the functions available in the various standard DGP models. Refer
to the SELECTION GUIDE in the previous section to determine functions included in a specific model.
1.2.2 APPLICATION
The DGP system is designed to be used on hydroelectric, gas, and steam generating units. Any size of gener-
ator can be protected with this digital system.
More detailed application considerations are contained below in the remaining headings of this section and in
Chapter 2: CALCULATION OF SETTINGS.
A typical wiring diagram for the DGP relay is shown on the following page.

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.2 INTRODUCTION
1
Figure 1–1: TYPICAL WIRING DIAGRAM
GROUND
BUS
A
B
C
AH
1
BG
8
BE
10
BE
9
BE
8
BE
7
AG
13
AG
12
AG
11
AG
10
AG
6
AG
5
AG
9
AG
8
AG
7
BF
5
BF
6
BF
6
BE
14
BE
13
BE
12
BE
11
AE
14
AE
13
AE
12
AE
11
AE
10
AE
6
AE
5
AE
9
AE
8
AE
7
TRIP A
(DRY)
TRIP B
(DRY)
TRIP C
(DRY)
TRIP D
(DRY)
ALARM A
ALARM B
ALARM C
ALARM D
VT FUSE FAIL
TEST PICKUP
TEST TRIP
SPARE
SELF TEST
NON
CRITICAL
SELF-TEST
CRITICAL
POWER
SUPPLY
ALARM 1
POWER
SUPPLY
ALARM 2
94G
94G1
94G2
94G3
74A
74B
74C
74D
74FF
DOR 12
DOR 13
DOR 9
74 NC
74 CR
TRIP A
TRIP B
TRIP C
TRIP D
BF
10
BF
9
BF
8
BF
7
AF
14
AF
13
AF
12
AF
11
AF
10
AF
6
AF
5
AF
9
AF
8
AF
7
BE
5
BE
6
BF
6
704753A7.CDR
BF
14
BF
13
BF
12
BF
11
GENERATOR
OFF LINE
TURBINE
INLET VALVE
LIMIT SWITCH
EXTERNAL
TRIP 1
INPUTS
OUTPUTS
EXTERNAL
TRIP 2
OSCILLOGRAPH
TRIGGER
EXT. VTFF/
Disable Prot.
BG
7
BG
6
BG
5
BG
4
BG
3
BG
2
BE
4
BE
2
BG
1
BE
3
BE
1
AH
12
AG1 CONTROL
POWER
AG2
BH
14
BH
1
BH
9
AH
2
AH
11
BH
2
BH
10
AH
3
BH
3
BH
11
AH
4
BH
4
BH
12
AH
5
BH
5
AH
9
AH
6
BH
6
AH
10
AH
7
BH
7
AH
8
BH
8
IAR
GND
VOLT
IAS VA IBR IBS VB ICR ICS VC
VOLTAGE
INPUTS
CURRENT
INRINS
A
C(B)
B(C)
DGP
Digital Generator Protection
g
DB25
DB9
DB25
RS-232
RS-232
IRIG-B
PRINTER
(REAR)
PL1
(FRONT)
(REAR)
PL2
(REAR)
PL3
AG
14
(+)
(+)
(+)
(+)
(-)
(-)
(-)
(-)
Contact Expansion
Unit
PRINTER
DEC1000
or
GE Power Management

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DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
11.3 PROTECTION FEATURES 1.3.1 DESCRIPTION
The following protection functions are included with the DGP system.
A single-line diagram for the DGP is shown below.
Figure 1–2: SINGLE LINE DIAGRAM
Table 1–3: DGP PROTECTION FUNCTIONS
PROTECTION FUNCTION ANSI CODE(S)
Stator Differential 87G
Current Unbalance 46
Loss of Excitation 40
Anti-Motoring 32
Time Overcurrent with Voltage Restraint 51V
Stator Ground 64G1, 64G2, 27TN
Ground Overcurrent 51GN
Over-excitation 24
Overvoltage 59
Undervoltage 27
Over and Underfrequency 81
Voltage Transformer Fuse Failure VTFF
Accidental Energization AE
To
MODEM
To
LAPTOP
PC
TRIP
ALARM
52G
GSU
Transf.
TO
POWER
SYSTEM
GEN.
51GN 64G1
64G2
27NT
RS232
46
87G 40
32
51V
VTFF
RS232
64G2
24 32
40
27
59
81
VTFF DGP
51V

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.3 PROTECTION FEATURES
1
1.3.2 STATOR DIFFERENTIAL (87G)
This function provides high-speed protection of the generator stator during internal phase-to-phase and three-
phase faults. It uses a product-restraint algorithm with dual-slope characteristic described in Section 2.3.2:
STATOR DIFFERENTIAL 87G on page 2–13. Refer to Figure 1–3: SIMPLE LOGIC DIAGRAM – 87G, 32, 27,
59, AND AE on page 1–12 for the logic diagram of this function.
Function 87G will not operate for turn-to-turn faults in the machine windings.
It will also not operate for single-phase-to-ground faults if the system is ungrounded or high-impedance
grounded. Phase-to-ground protection by this function requires that the neutral of the machine (or another
machine operating in parallel) be grounded. A small portion of the winding next to the neutral will not be pro-
tected, the amount being determined by the voltage necessary to cause minimum pickup current to flow
through the neutral-to-ground impedance. Current-limiting devices in the neutral-ground circuit increase this
impedance and will decrease the ground-fault-protection coverage of this function.
1.3.3 CURRENT UNBALANCE (46T)
There are several causes of generator unbalance. Some of these include unbalanced loads, unbalanced sys-
tem faults, and/or open circuits. The negative-sequence component (
I
2
) of stator current is directly related to
this unbalance and sets up a counter-rotating flux field in the machine. This in turn causes local heating in the
rotor iron. The capability of machines to withstand heating caused by unbalance currents is typically exper-
essed in terms of an constant, and is supplied by the manufacturer of the machine.
The current unbalance trip function (46T) of the DGP provides operating-time characteristics expressed as
I
22
T = K, as shown in Figure 2–6: TIME CURRENT CHARACTERISTIC OF 46T FUNCTION on page 2–19. A
linear reset characteristic is incorporated to approximate the machine cooling following an intermittent current-
unbalance condition. In addition to 46T, the DGP system also includes a current-unbalance alarm function,
46A, which is operated by the negative-sequence component (I2) with an adjustable pickup and time delay.
See Figure 1–4: SIMPLE LOGIC DIAGRAM – 46, 40, AND 51V on page 1–13 for the logic diagram.
1.3.4 LOSS OF EXCITATION (40)
This function is used to detect loss of excitation on synchronous machines. It includes two mho characteristics
looking into the machine, each with adjustable reach, offset, and time delay. Logic is provided to block this
function by presence of a negative-sequence voltage (indicating a voltage transformer fuse failure VTFF condi-
tion) and/or an external VTFF Digital Input DI6 (see Figure 1–4: SIMPLE LOGIC DIAGRAM – 46, 40, AND 51V
on page 1–13).
Excitation can be lost due to inadvertent tripping of the field breaker, open or short circuit on the field winding,
regulator failure, or loss of the source to the field winding. Loss of excitation can be damaging to the machine
and/or detrimental to the operation of the system. When a synchronous generator loses excitation, it will tend
to act as an induction generator: it will run above normal speed, operate at reduced power and receive its exci-
tation (VARS) from the system. The impedance seen by a relay looking into a generator will depend on the
machine characteristics, the load flow prior to the loss of excitation, and the type of excitation failure.
Studies indicates that first zone mho function (40-1) can be set to detect severe cases of excitation failure with
a shorter time delay, whereas the second zone (40-2) can be set to detect all the excitation failure cases. A
longer time delay setting is required for the 40-2 function for security during stable power system swing condi-
tions. Figure 2–7: MHO CHARACTERISTICS FOR 40-1 & 40-2 FUNCTIONS on page 2–21 shows the charac-
teristics of this function.
I
2
2
T

1-
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DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
11.3.5 ANTI-MOTORING (32)
On a total or partial loss of prime mover, if the power generated is less than no-load losses of the machine, real
power will start flowing into the generator. Typical motoring power of different kinds of prime movers are shown
in the table below. For a specific application, the minimum motoring power of the generator should be obtained
from the supplier of the unit.
The DGP system includes a reverse power function with adjustable time-delay. Either one or two (32-1 & 32-2)
independent setpoints are incorporated depending on the model number.
The 32-1 can be configured as a part of sequential tripping logic as shown in Figure 1–3: SIMPLE LOGIC DIA-
GRAM – 87G, 32, 27, 59, AND AE on page 1–12. If the sequential trip logic is used, 32-1 is enabled when clos-
ing of turbine inlet valves is indicated by digital input DI2 following a turbine trip. The trip sequence is then
continued when timer TL1 times out. The 32-2, if included, is not dependent on the DI2 and is primarily
intended to provide backup to the sequential trip. If the sequential trip is not enabled, the 32-1 can be used as
anti-motoring similar to 32-2.
1.3.6 TIME OVERCURRENT WITH VOLTAGE RESTRAINT 51V
A system must be protected against prolonged generator contribution to a fault. The DGP incorporates a time-
overcurrent function with voltage restraint (51V) to provide part of the system backup protection. As shown in
Figure 1–4: SIMPLE LOGIC DIAGRAM – 46, 40, AND 51V on page 1–13, this function is supervised by a fault
detector and VTFF. The VTFF supervision can be by an internal and/or external (DI6) VTFF function. See Sec-
tion 2.3.7: OVERCURRENT WITH VOLTAGE RESTRAINT (51V) on page 2–22 for the characteristic curves of
the 51V. Note that a separate algorithm is processed for each phase, with the restraint provided by correspond-
ing phase voltage. The restraint is proportional to the magnitude of the voltage and is independent of the phase
angle. A linear reset characteristic is incorporated for this function.
1.3.7 STATOR GROUND (64G/27TN)
This function consists of two overlapping zones (64G1 and 64G2/27TN) to detect stator ground faults in a high-
impedance-grounded generator system. The 64G1 is standard in all DGP models; however, the 64G2/27TN
function is provided in some models only. Together, the two zones cover 100% of the stator windings. See Fig-
ure 1–5: SIMPLE LOGIC DIAGRAM – 64G1, 64G2, 51GN, AND 24 on page 1–14.
Normally the generator-stator neutral has a potential close to ground. With the occurrence of a stator ground
fault, a potential increase will occur on the neutral for all faults except those near the neutral. 64G1 uses a fun-
damental-frequency neutral overvoltage to cover about 95% of the stator winding, depending on the pickup
voltage setting. Alternately, 64G1 can be used as a generator-bus ground detector in a high-impedance
grounded or an ungrounded system. For this application, the VN input must be a zero-sequence voltage
derived from the generator bus, and functions 64G2/27TN must be disabled.
Table 1–4: TYPICAL MOTORING POWER
TYPE OF PRIME
MOVERS MOTORING POWER IN % OF UNIT RATING
Gas Turbine 10 to 100
Diesel 15 to 25
Hydraulic Turbine 2 to 100
Steam Turbine 0.5 to 4

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.3 PROTECTION FEATURES
1
64G2 is based on the percentage of third-harmonic voltage at the generator neutral (VN3) compared to the
total third-harmonic voltage generated. This function is designed to cover 15% of the neutral end of the stator
windings, and is supervised by fundamental and third-harmonic voltage thresholds. These thresholds are fixed
at 30 and 0.5 volts respectively. The third-harmonic comparator method eliminates the need to know the gener-
ator harmonic characteristic to use or set this function. Note that wye-connected VTs are required for
proper operation of 64G2.
27TN is the third-harmonic neutral undervoltage function with a forward power supervision and can be used
with either wye or delta connected VTs. The percentage of stator windings covered by this function depends on
its threshold setting as well as the VN3 generated by the machine at the time of the fault. The magnitude of
VN3 under normal conditions is a function of several factors, such as type of generator, load current, load
power factor, system status, etc. It can be very small (nearly zero) under some conditions. To enhance security
during low VN3 voltage conditions, this function can be inhibited by a settable window of forward power. How-
ever, it should be noted that other conditions influencing the VN3 voltage may make 27TN insecure. In these
cases, function 64G2 (available in some models; see the DGP nomenclature guide) or some other means
should be considered.
Digital input DI1 can be configured to block 64G2/27TN when the generator is off-line. This provision is made
to enhance security of the functions under conditions such as static start of a gas turbine generator. Temporary
ungrounding of generator neutral during the static start can look like a ground fault near the neutral.
1.3.8 GROUND OVERCURRENT (51GN)
51GN is an inverse overcurrent function available in some models. It can be used to detect stator ground faults
in a high or low resistance grounded generator system. See Figure 1–5: SIMPLE LOGIC DIAGRAM – 64G1,
64G2, 51GN, AND 24 on page 1–14 for simplified logic diagram and Figure 2–16: 51GN TIME-CURRENT
CHARACTERISTICS on page 2–39 for the inverse time-current characteristics.
This function uses current INR which can be derived by residual connection or by using a generator neutral CT
as noted in Figures 1–9: ELEMENTARY DIAGRAM WITH TEST BLOCKS, WYE VTs and 1–12: ELEMEN-
TARY DIAGRAM WITHOUT TEST BLOCKS, DELTA VTs.
Since this function is independent of the phase current inputs, it can alternately be connected to a CT in the
neutral of the generator step-up transformer.
1.3.9 OVEREXCITATION (24)
Overexcitation can be caused by regulator failure, load rejection, or an excessive excitation when the genera-
tor is off-line. It can also result from decreasing speed while the regulator or an operator attempts to maintain
rated stator voltage. The Volts/Hertz quantity is proportional to magnetic flux in the generator and step-up
transformer cores, and is used to detect the overexcitation condition. See Figure 1–5: SIMPLE LOGIC DIA-
GRAM – 64G1, 64G2, 51GN, AND 24 for details.
The overexcitation protection includes trip (24T) and alarm (24A) functions. 24T consists of an inverse function
and an instantaneous function with time-delay characteristics. The combination of these two characteristics
allows the 24T setting to closely follow the generator and/or step-up transformer V/Hz limit curve. Both 24A
and 24T are computed for each of the three phase voltages (see Table 2–3: 24A VOLTAGES on page 2–30).
Function 24T can be configured to operate different output relays for generator on-line and off-line conditions.
This function incorporates a user-settable linear reset characteristic to mimic machine cooling. The figures in
Section 2.3.12: OVEREXCITATION TRIP (VOLTS/HERTZ: 24T) show the characteristics of this function.

1-
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DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
11.3.10 OVERVOLTAGE (59)
This function consists of a positive-sequence overvoltage with an user selectable inverse or definite time char-
acteristic. See Figure 1–3: SIMPLE LOGIC DIAGRAM – 87G, 32, 27, 59, AND AE on page 1–12 for the logic
diagram and Figure 2–15: 59 TIME-VOLTAGE CHARACTERISTICS on page 2–35 for the inverse time-voltage
characteristics. A linear reset characteristic is incorporated for this function. The overvoltage function can be
considered as a backup to the Volts/Hz function. Some possible causes of this condition are a system distur-
bance or regulator failure.
1.3.11 UNDERVOLTAGE (27)
This function consists of a positive-sequence undervoltage with an user selectable inverse or definite time
characteristic. See Figure 1–3: SIMPLE LOGIC DIAGRAM – 87G, 32, 27, 59, AND AE on page 1–12 for the
logic diagram and Figure 2–17: 27 TIME-VOLTAGE CHARACTERISTICS on page 2–40 for the inverse time-
voltage characteristics. A linear reset characteristic is incorporated for this function.
1.3.12 OVER AND UNDERFREQUENCY (81)
This function provides over and underfrequency protection, each with an adjustable time delay. Two or four
over and underfrequency steps are provided depending on the model. All frequency functions are supervised
by an adjustable positive-sequence voltage level. This undervoltage cut-off level and/or digital input DI1 can be
used to block the frequency functions during start-up. Frequency disturbance can occur due to a system fault
or islanding of the unit or an unconnected unit can operate at abnormal frequency due to malfunction of speed
control. Figure 1–6: SIMPLE LOGIC DIAGRAM – 81-O AND 81-U on page 1–15 shows the logic diagram for
this function.
1.3.13 VOLTAGE TRANSFORMER FUSE FAILURE (VTFF)
Functions 40 and 51V may operate for a full or partial loss of AC potential caused by one or more blown fuses.
The DGP makes provisions to block tripping by these functions when a fuse failure is detected; all other protec-
tion functions are allowed to trip. Figure 1–7: SIMPLE LOGIC DIAGRAM – VT FUSE FAILURE on page 1–16
shows the logic diagram for the VTFF function.
If AC potential is lost on one or more phases, the negative-sequence voltage (V2) rises and/or the positive-
sequence voltage (V1) drops. Either V2 > 15V or V1 < 50V provides a basic indication of the VTFF condition.
This signal is supervised by a Disturbance Detector (DD) and generator positive-sequence current (I1) detec-
tor (see three-input AND gate on the logic diagram). Supervision by the DD and I1 signals provide security
against false operation during fault and generator out of service conditions respectively. Security is enhanced
by use of the A/0 and B/0 timers shown in the logic diagram.
Signal DD is derived from a combination of sequence current levels, change in levels, and pickup flags of vari-
ous protection functions as shown in the logic diagram.
The VTFF logic allows integration of an external VTFF contact. Either of the two fuse-failure signals or both
signals can be configured to block tripping of functions 40 and 51V.
Detection of VTFF energizes the 74FF (Fuse Failure alarm) relay, de-energizes the 74CR (critical alarm) relay,
and turns the status LED red, even though all protection functions except 40 and 51V are unaffected.

GE Power Management DGP Digital Generator Protection System 1-
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1 PRODUCT DESCRIPTION 1.3 PROTECTION FEATURES
1
1.3.14 ACCIDENTAL ENERGIZATION (AE)
The DGP includes logic to detect accidental energization of the generator (see Figure 1–3: SIMPLE LOGIC
DIAGRAM – 87G, 32, 27, 59, AND AE on page 1–12). When a generator is energized while at standstill or
reduced speed, it behaves and accelerates as an induction motor. The machine terminal voltage and current
during such an event will be a function of generator, transformer, and system impedances.
An instantaneous overcurrent signal (50) is used to detect the accidental energization. This signal is armed by
a logic signal derived from positive-sequence voltage and GEN OFF LINE input DI1. These two "arming" sig-
nals can be configured in AND or OR mode by Setting 2703: AE ARM. The 50 function is armed 5 seconds
after the generator is taken out of service. The logic automatically disarms itself during a normal start-up
sequence when the voltage detector picks up and/or the generator is on-line.
For the AE logic to perform, special precautions must be taken to ensure that the DGP system and associated
trip circuits remain in service when the generator is out of service. Additionally, the generator off-line input, DI1,
must be reliable. It should also be noted that the pickup flag of function 51V is used as signal 50; therefore this
logic will automatically be disabled if function 51V is disabled.

1-
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DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
1
Figure 1–3: SIMPLE LOGIC DIAGRAM – 87G, 32, 27, 59, AND AE
87G
AE
CONFIGURABLE
LOGIC (2)
TRIP A
94G
TRIP B
94G1
OR
TRIP C
94G2
OR
TRIP D
94G3
OR
ALARM
74A
OR
ALARM
74B
OR
ALARM
74C
OR
ALARM
74D
OR
Undervoltage
(1)
27
(+) DI1
Gen.
Off-Line
AND
Overvoltage
59
Reverse Pwr.
No. 2 (1)
AND TL2
32-2
Reverse Pwr.
No. 1
(+)
DI2
Turbine Inlet Valve
Closed
Seq. Trip Enabled
(+)
DI1
SELBKDI1
Gen.
Off-Line
AND ANDOR TL1
32-1
AE
(+)
DI1
AND
Gen. Off-line
AE ARM
AND
50 (51V Pickup Flag)
AND AND
VTFF
PU
DO
V1 < 30V
OR
OR
AND
Stator
Differential
87G
NOTES:
(1) Indicates an optional function (includes associated logic). Refer to
DGP nomenclature selection guide for available functions in a
specific model.
(2) Each of the available protection functions can be configured to
operate any combination of the 8 output relays (4-Trip and 4-Alarm).
PU=5 sec
DO=0.25 sec
OR

GE Power Management DGP Digital Generator Protection System 1-
13
1 PRODUCT DESCRIPTION 1.3 PROTECTION FEATURES
1
Figure 1–4: SIMPLE LOGIC DIAGRAM – 46, 40, AND 51V
87G
AE
CONFIGURABLE
LOGIC (2)
TRIP A
94G
TRIP B
94G1
OR
TRIP C
94G2
OR
TRIP D
94G3
OR
ALARM
74A
OR
ALARM
74B
OR
ALARM
74C
OR
ALARM
74D
OR
NOTE:
(1) Timers TL21 and TL22 are available in models DGP***ACA only.
Loss of Excitation
Zone 1 40-1
VTFF + DI6
FD
Overcurrent
(voltage restraint) 51V
(+)
DI3
TL21
(1)
External Trip - 1
DI3
DI4
TL22
(1)
External Trip - 2
DI4
(+)
Current Unbalance
(Alarm)
TL14
46A
Current Unbalance
(Trip) 46T
TL12AND
Loss of Excitation
Zone 2 40-2
TL13AND
AND
(+)
DI6 Ext. VTFF OR
V
2
>
15V SELV2SUP
PUDO
ENA
DIS
PU=3 Samples
DO=5 Samples
OR
(2) Each of the available protection functions can be configured to
operate any combination of the 8 output relays (4-Trip and 4-Alarm).
DSPLGC2.VSD

1-
14
DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
1
Figure 1–5: SIMPLE LOGIC DIAGRAM – 64G1, 64G2, 51GN, AND 24
CONFIGURABLE
LOGIC (2)
TRIP A
94G
OR
TRIP B
94G1
OR
TRIP C
94G2
OR
TRIP D
94G3
OR
ALARM
74A
OR
ALARM
74B
OR
ALARM
74C
OR
ALARM
74D
OR
NOTES:
(1) Indicates an optinal function (includes associated logic). Refer to
DGP nomenclature selection guide for available functions in a
specific model.
Overexcitation
(Alarm)
TL6
24A
Stator Ground
Zone 1 64G1
TL4
AND
24T
(On-Line)
AND
Overexcitation
(Trip)
TL7
Time
Inst OR
DI1
(+)
Gen.
Off-Line
24T
(Off-Line)
Neutral Overcurrent
(1) 51GN
Stator Ground
Zone 2 (1)
AND TL5
VP3 > 0.5V
V1
>
30V
(+)
DI1
SELBKDI1
Gen.
Off-Line
64G2
TL20
AND
(+) DI1
GEN. OFF-LINE
SELBKDI1
POWER < FORPWR-L
POWER > FORPWR-H
OR
27TN
(1)
(2) Each of the available protection functions can be configured to
operate any combination of the 8 output relays (4-Trip and 4-Alarm).
V
1
≥
25V
V
N3
≤
27TN PICKUP

GE Power Management DGP Digital Generator Protection System 1-
15
1 PRODUCT DESCRIPTION 1.3 PROTECTION FEATURES
1
Figure 1–6: SIMPLE LOGIC DIAGRAM – 81-O AND 81-U
AE
CONFIGURABLE
LOGIC (2)
TRIP A
94G
OR
TRIP B
94G1
OR
TRIP C
94G2
OR
TRIP D
94G3
OR
ALARM
74A
OR
ALARM
74B
OR
ALARM
74C
OR
ALARM
74D
OR
NOTES:
(1) Indicates an optional function (includes associated logic). Refer to
DGP nomenclature selection guide for available functions in a
specific model.
Under Frequency
Set Point - 1 81-1U
TL8
AND
Under Frequency
Set Point - 3 (1) 81-3U
TL10
AND
Under Frequency
Set Point - 2 81-2U
TL9
AND
Under Frequency
Set Point - 4 (1) 81-4U
TL11
AND
(+)
DI1
SELBKDI1
Gen.
Off-Line
V1 > UVCUTOFF
Over Frequency
Set Point - 1 81-1O
TL15
Over Frequency
Set Point - 3 (1)
TL17
Over Frequency
Set Point - 2
81-3O
TL16
Over Frequency
Set Point - 4 (1) 81-4O
TL18
81-2O
AND
AND
(2) Each of the available protection functions can be configured to
operate any combination of the 8 output relays (4-Trip and 4-Alarm).
AND
AND

1-
16
DGP Digital Generator Protection System GE Power Management
1.3 PROTECTION FEATURES 1 PRODUCT DESCRIPTION
1
Figure 1–7: SIMPLE LOGIC DIAGRAM – VT FUSE FAILURE
NOTE:
* = 1 FOR 5 AMP RATED DGPs.
* = 5 FOR 1 AMP RATED DGPs.
AND
AND
(+) External VTFF
DI6
OR
PUDO
OR
PUDO
ENA
DIS VTFF VTFF Alarm
Critical Alarm
AND
OR OR OR
Supervise
51V,
21(Future)
FD DD
I1 > 0.1/*
51V Pickup Flag
40 Pickup Flag
87G Pickup Flag OR
51GN Pickup Flag
21 Pickup Flag (Fut.)
OR
64G1 Pickup Flag
64G2 Pickup Flag
(+)
DI1
SELBKDI1
Gen.
Off-Line
OR VTFF + DI6 Supervise
51V,
21(Future)
DGP_VTFF.VSD
|
∆
I2|
≥
0.2 / *
|
∆
I1|
≥
0.2 / *
|
∆
I0|
≥
0.2 / *
∆
I0
≥
0.6 / *
∆
I2
≥
0.6 / *
PU=9000 samples
DO=0
V1
<
50V
V2
>
15V
PU = 36 samples
DO = 0

GE Power Management DGP Digital Generator Protection System 1-
17
1 PRODUCT DESCRIPTION 1.4 OTHER FEATURES
1
1.4 OTHER FEATURES 1.4.1 INPUTS
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 (IAS, IBS, and ICS) are used to process functions 46, 40, 32,
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 INS and INR are derived from the residual connections of the respective phase CTs and do
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 INS and/or INR values by the DGP as a part of the
background self-test.
The INR current is used to process the 51GN function (not available on DGP***AAA models). If desired, a ded-
icated neutral CT can be used for the input INR.
The DGP phase voltage inputs can be wye or delta and are derived from the generator terminal voltage. VNis
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.
1.4.2 OUTPUT RELAYS
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.

1-
18
DGP Digital Generator Protection System GE Power Management
1.4 OTHER FEATURES 1 PRODUCT DESCRIPTION
1Also included are two additional relays (TEST PICKUP and TEST TRIP) that can be configured to operate by a
selected protection function pickup flag and trip output. These two outputs are intended to facilitate testing of
the selected protection function.
A Contact Expansion Unit is also available which can be used with DGP***ACA models. The General Electric
DEC1000 Contact Expansion Unit provides eleven additional output relays that can be factory configured to
user specifications. Refer to the GE Power Management Product Catalog, the GE Power Management Prod-
ucts CD, or instruction book GEK-105561 for additional details on the DEC1000.
1.4.3 START-UP SELF-TESTS
The most comprehensive testing of the DGP is performed during power-up. Since the DGP is not performing
any protection activities at that time, tests (such as RAM tests) that would normally be disruptive to run-time
processing are performed during the start-up. All processors participate in the start-up self-test process. The
processors communicate their results to each other so that any failures found can be reported to the user and
to ensure each processor successfully completes its assigned self-tests before the DGP system begins protec-
tion activity.
During power-up, the microprocessors perform start-up self-tests on their associated hardware (PROM, local
RAM, shared RAM, interrupt controller, timer chip, serial and parallel I/O ports, non-volatile memory, analog
and digital I/O circuitry, MMI hardware, etc.). In addition, the DGP system verifies that the PROM version num-
bers in all processor boards are compatible. The components tested at start-up are listed in Table 6–1: START-
UP SELF-TESTS on page 6–2.
In most cases, if any critical self-test failure is detected, the DGP will not continue its start-up but will not cause
a reset. An attempt will be made to store the system status, to initialize the MMI and remote communications
hardware/software for communication status, and to print a diagnostic message. The critical alarm relay will be
de-energized.
If no failures are detected, the DGP completes initialization of its hardware and software. Next, each processor
board (DAP and SSP) will enable the outputs. As a final step, the DGP checks the results of all the tests to
determine whether to turn the front panel status LED to green.
The start-up procedure takes approximately one minute. As soon as the SSP successfully completes its
PROM test and initializes the display hardware, the message INITIALIZING will be displayed. When the DGP
system initialization is completed, the display is blanked and the relay begins acquiring and processing data.
1.4.4 RUN-TIME SELF-TESTS
Each of the processors has "idle time" when the system is in a quiescent state; that is, when the DGP is not
performing fault or post-fault processing. During this idle time, each processor performs background self-tests
that are non-disruptive to the foreground processing. If any background self-test fails, the test is repeated. To
declare a component FAILED, the test must fail three consecutive times. In the case of critical failures, the
DGP forces a self reset to resume operation again after an intermittent failure. The reset activities are identical
to the start-up activities except that not all start-up self-tests are performed.
A reset is not reported to the user by the DGP system. If the reset is successful, no message is printed, no fail-
ure status is recorded, and the critical alarm is not generated. However, during the reset procedure, the red
LED on the MMI panel will light and a failure code may appear on the MMI display. If the reset is not success-
ful, the processor board will be shut down, leaving the MMI panel displaying the error information. Refer to
Section 6.4: ERROR CODES on page 6–7 for error codes. To prevent continual resets in the case of a solid
failure, both hardware and software will permit only four resets in a one hour period. On the fifth reset, the DGP
will not perform initialization, but will attempt to initialize MMI, communications, and the critical alarm output, as
in the case of a start-up with a critical self-test failure.