Basler BE1-46N User manual

INSTRUCTION MANUAL
FOR
NEGATIVE SEQUENCE OVERCURRENT
RELAY
BE1-46N
Publication Number: 9 1700 00 990
Revision: F 02/01
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BE1-46N Introduction i
W A R N I N G !
TO AVOID PERSONAL INJURY OR EQUIPMENT DAMAGE, ONLY
QUALIFIED PERSONNEL SHOULD PERFORM THE PROCEDURES
PRESENTED IN THIS MANUAL.
INTRODUCTION
This manual provides information concerning the operation and installation of the BE1-46N Negative
Sequence Overcurrent Relay. To accomplish this, the following is provided.
b
Specifications
b
Functional Description
b
Mounting Information
b
Operational Test Procedure
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ii BE1-46N Introduction
CONFIDENTIAL INFORMATION
OF BASLER ELECTRICCOMPANY, HIGHLAND, IL. IT IS LOANEDFORCONFIDENTIALUSE, SUBJECT
TO RETURN ON REQUEST, AND WITH THE MUTUAL UNDERSTANDING THAT IT WILL NOT BE USED
IN ANY MANNER DETRIMENTAL TO THE INTEREST OF BASLER ELECTRIC COMPANY.
It is not the intention of this manual to cover all details and variations in
e
q
ui
p
ment, nor does this manual
p
rovide data for ever
y
p
ossible contin
g
enc
y
re
g
ardin
g
installation or o
p
eration. The availabilit
y
and desi
g
n of all features
and o
p
tions are sub
j
ect to modification without notice. Should further
information be re
q
uired, contact Basler Electric Com
p
an
y
, Hi
g
hland, Illinois.
First Printing: May 1985
Printed in USA
© 1995, 1998, 2001 Basler Electric Co., Highland, IL 62249
February 2001
BASLER ELECTRIC
ROUTE 143, BOX 269
HIGHLAND, IL 62249 USA
http://www.basler.com, [email protected]
PHONE [phone] FAX [phone]
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BE1-46N Introduction iii
CONTENTS
SECTION 1 GENERAL INFORMATION 1-1
Description ................................................1-1
Principles of Symmetrical Operation ............................1-1
Model and Style Number .....................................1-1
Style Number Example ...................................1-2
Style Number Identification Chart ...........................1-2
Specifications ..............................................1-3
SECTION 2 HUMAN-MACHINE INTERFACE 2-1
Controls and Indicators ......................................2-1
SECTION 3 FUNCTIONAL DESCRIPTION 3-1
General ...................................................3-1
Input Sensing ..............................................3-1
Measuring I2...............................................3-1
Microprocessor .............................................3-2
Program Monitor ............................................3-2
Outputs ...................................................3-2
Power Supply ..............................................3-2
Power Supply Status Output ..................................3-3
Setting Consideration ........................................3-3
I nReference Level (Tap Value) ............................3-4
Alarm and Pickup ........................................3-4
K Setting ..............................................3-4
MAX TIME .............................................3-4
Calculation Example ........................................3-5
Setting Tap Adjust ..........................................3-5
Method 1, Single-Phase ..................................3-5
Method 2, Three-Phase ...................................3-6
Further Considerations .......................................3-7
Characteristic Curves ........................................3-8
SECTION 4 INSTALLATION 4-1
General ...................................................4-1
Relay Operating Precautions ..................................4-1
Dielectric Test ..............................................4-1
Mounting ..................................................4-1
S1 Case, Outline Dimensions, Front View ....................4-2
S1 Case, Panel Drilling Diagram, Semi-Flush Mounting .........4-3
S1 Case, Outline Dimensions, Rear View .....................4-4
S1 Case, Semi-Flush Mounting, Side View ...................4-5
S1 Case, Panel Drilling Diagram, Projection Mounting ..........4-6
S1 Case, Projection Mounting, Side View .....................4-7
Remote Meter Dimensions and Drilling Diagram ...............4-8
Connections ...............................................4-8
Typical DC Control Connections ............................4-9
Typical AC Sensing Connections ..........................4-10
Typical Internal Connections ..............................4-11
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iv BE1-46N Introduction
CONTENTS- Continued
SECTION 5 TESTING 5-1
General ............................................................5-1
Testing .............................................................5-1
Operational Test Procedure ............................................5-1
Pickup and Alarm .................................................5-1
Timing ..........................................................5-2
MAX TIME .......................................................5-3
SECTION 6 MAINTENANCE 6-1
General ............................................................6-1
In-House Repair .....................................................6-1
Storage ............................................................6-1
SECTION 7 MANUAL CHANGE INFORMATION 7-1
Summary and Cross Reference Guide ....................................7-1
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BE1-46N General Information 1-1
SECTION 1 • GENERAL INFORMATION
DESCRIPTION
BE1-46N Negative Sequence Overcurrent Relays are three-phase solid state relays designed to provide
protectionforgeneratorsandmotorsfromunbalancedloadingorpowersystemfaults. Theserelaysprotect
themachineryfromdamagewhentheprotectiveschemeorotherequipment,externaltothegenerator,fails
to eliminate the unbalanced condition.
BE1-46NNegativeSequenceOvercurrentRelaysaccuratelymonitorthemagnitudeandcontroltheduration
of the negative sequence current component. These relays incorporate a time delay that replicates the
machinery heating and coolingcharacteristics. Analarm element in the relays may be used to provide time
to locate and isolate the fault. Doing this avoids damage tothe machinery, preventsan undesired trip,and
precludes a potentially prolonged outage of the machinery.
BE1-46N relays are designed for use with any poly-phase generating system having known (I2)2t limits
between 1 and 99. Relays that operate using phase currents to determine the negative sequence
component are phase rotation sensitive. BE1-46N relays are phase rotation sensitive.
PRINCIPLES OF SYMMETRICAL COMPONENTS
Principles of symmetrical components allow an unbalanced system to be considered as three separate,
balanced subsystems. These balanced subsystems may then be analyzed as single phase quantities.
These quantities are the positive, negative, and zero sequence components of current and voltage.
Thepositivesequencecomponentofcurrent(I1)representstheportionofthetotalcurrentwhichhasnormal
phase rotation and produces no adverse effect on the system. An ideally balanced system contains only
positive sequence phase currents and voltages.
The zero sequence component of current (I0) also has no adverse effect on a three-phase, three-wire (no
neutral connection) power system because it produces no appreciable magnetic flux and causes no
excessive heating in the generator rotor or windings.
The negative sequence component of current (I2) produces a magnetic flux in the stator thathas the same
rotationalspeed as therotorflux,butinthe oppositedirection. Thiscausesthestatormagneticfluxtorotate
at twice the system frequency and induce eddy currents into the rotor. These eddy currents create
excessiveheatin therotorironand windings, and,ifallowedtopersist,could result inseveredamage to the
system.
MODEL AND STYLE NUMBER
Electrical characteristics and operational features included in a specific relay are defined by a combination
of letters and numbers that constitute the device style number. The model number, BE1-46N, designates
the relay as a Basler Electric Class 100 Negative Sequence Overcurrent Relay. The style number together
with the model number describe the features and options in a particular device and appear on the front
panel, drawout cradle, and inside the case assembly.
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1-2 BE1-46N General Information
St
y
le Number Exam
p
le
The following style number identification chart illustrates the features and options for BE1-46N relays. For
example, if the style number were BE1-46N G1H B8S B1B1F, the relay would have the following features:
BE1-46N Model number.
GThree-phase negative sequence current sensing.
1Sensing input range of 3.0 to 5.0 A nominal at 60 hertz.
HAlarm output relay contacts NC and trip output relay contacts NO.
B8 (I 2)2t timing characteristics.
SField selectable 48 or 125 Vdc power supply.
BOne current operated target for the trip circuit.
1A remote meter for monitoring I 2levels is supplied.
BAn oscillograph start function with NC contacts.
1An auxiliary output relay with NO contacts.
FSemi-flush mounting.
St
y
le Number Identification Chart
Figure 1-1. Style Number Identification Chart
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BE1-46N General Information 1-3
SPECIFICATIONS
Current Sensin
g
(
5 Am
p
ere CT
)
5 amperes nominal (50/60 hertz) current transformers; 10 amperes
continuous current, 250 amperes one second current, 2 VA burden
maximum per phase, frequency range 45 to 55 hertz for 50 hertz
systems and 55 to 65 hertz for 60 hertz systems.
(1 Ampere CT) 1amperenominal(60 hertz)currenttransformers;2 ampere continuous
current, 50 ampere one second current, 2 VA burden maximum per
phase, frequency range 60 ±5 hertz.
Power Supply Power for the internal circuitry may be derived from ac or dc external
power sources.
Type Nominal Input Voltage Input Voltage Range Burden at Nominal (Maximum)
O (Mid Range) 48 Vdc 24 to 150 Vdc 5.5 W
P (Mid Range) 125 Vdc
120 Vac 24 to 150 Vdc 90 to 132 Vac 6.0 W 16.0 VA
R (Low Range) 24 Vdc 12† to 32 Vdc 5.5 W
S (Mid Range) 48 Vdc
125 Vdc 24 to 150 Vdc 24 to 150 Vdc 5.5 W 6.0 W
T (High Range) 250 Vdc
240 Vac 62 to 280 Vdc 90 to 270 Vac 7.0 W 16.0 VA
†TypeRpowersupplyinitiallyrequires14Vdctobeginoperating. Onceoperating,thevoltagemay
be reduced to 12 Vdc and operation will continue.
Output Circuits Output contacts are rated as follows:
Resistive:
120/240 Vac Make 30 amperes for 0.2 seconds, carry 7 amperes continuously, and
break 7 amperes.
250 Vdc Make 30 amperes for 0.2 seconds, carry 7 amperes continuously, and
break 0.3 ampere.
Inductive:
120/240 Vac, Make 30 amperes for 0.2 seconds, carry 7 amperes continuously,
125/250 Vdc and break 0.3 ampere. (L/R = 0.04).
Oscillograph Start 0.5 ampere at 48 Vdc.
Target Indicators Targetsmaybe specified as eitherinternallyoperated,orcurrent operated
by a minimum of 0.2 ampere through the output trip circuit. When current
operated,theoutputcircuitmustbelimited to30amperes for0.2seconds,
7 amperes for 2 minutes, and 3 amperes continuously.
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1-4 BE1-46N General Information
TAP ADJUST Selection Ran
g
e
(5 Ampere CT) Continuously adjustable over the range of 3.0 amperes to 5.0 amperes.
This adjustment establishes the full load reference level (IN) for the
application.
(1 Ampere CT) Continuously adjustable over the range of 0.6 A to 1.0 A. This adjustment
establishes the full load reference level (IN) for the application.
PICKUP Selection Range Adjustable over the range of 1 to 50% in increments of 1%.
PICKUP Measuring Accuracy ±0.5% of I2.
PICKUP Dropout Ratio Better than 98% of pickup.
ALARM Selection Range Adjustable over the range of 1 to 50% in increments of 1%.
ALARM Pickup Measuring ±0.5% of I2.
Accuracy
ALARM Time Delay Factory set at 3.0 seconds.
ALARM Dropout Ratio Better than 98% of ALARM pickup level.
K SET Timing Accuracy ±5% of the selected curve.
Minimum Trip Timer Accuracy 200 ±25 milliseconds.
MAX TIME (X 10 SEC) Adjustable over the range of 10 to 990 seconds in increments of 10
Selection Range seconds.
MAX TIME Accuracy ±5% of the setting.
Radio Frequency Field tested using a five watt, hand-held transceiver operating at random
Interference
(
RFI
)
frequenciescenteredaround144 megahertzand440 megahertz,with the
antenna located six inches from the relay in both horizontal and vertical
planes.
Fast Transient Qualified to ANSI/IEEE C37.90.1-1989.
Isolation In accordance with ANSI/IEEE C37.90-1989 one minute dielectric (high
potential) test as follows:,
All circuits to ground: 2121 Vdc.
Input to output circuits: 1500 Vac or 2121 Vdc.
Surge Withstand Capability 3WCNKHKGF VQ #05++''' % 5VCPFCTF 5WTIG 9KVJUVCPF %C
RCDKNKV[ 59% 6GUVU HQT 2TQVGEVKXG 4GNC[U CPF 4GNC[ 5[UVGOU
Shock In standard tests, the relay has withstood 15 g in each of three mutually
perpendicular planes without structural damage or degradation of perfor-
mance.
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BE1-46N General Information 1-5
Vibration: In standard tests, the relayhaswithstood2 g in each ofthreemutuallyper-
pendicular planes,swept over therange of 10 to 500 hertzfor a total ofsix
sweeps,15minuteseachsweep,withoutstructuraldamageordegradation
of performance.
UL Reco
g
nized UL Recognized per Standard 508, UL File No. E97033. Note: Output
contacts are not UL Recognized for voltages greater than 250 volts.
O
p
eratin
g
Tem
p
erature -40
( C (-40 ( F) to 70 ( C (158 ( F).
Stora
g
e Tem
p
erature -65
( C (-85 ( F) to +100 ( C (+212 ( F).
Wei
g
ht 13.5 pounds maximum.
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BE1-46N Human-Machine Interface 2-1
SECTION 2 • HUMAN-MACHINE INTERFACE
CONTROLS AND INDICATORS
Table 2-1. BE1-46N Controls and Indicators (Refer to Figure 2-1)
Locator Control or Indicator Function
A PICKUP (Trip Level) Front-panel thumbwheel switch provides selection of the
negative sequence overcurrent pickup point that, when
exceeded, initiates timing. Setting is continuously
adjustable over the range of 1 to 50% in increments of
1%. A setting of 00 will be recognized as 1%. Any
setting beyond 50 will be recognized as 50%.
BALARM
(Trip Level) Front-panel thumbwheel switch provides selection of the
pickup point for the ALARM trip level and is continuously
adjustable over the range of 1 to 50% in increments of
1%. A setting of 00 will be recognized as 1%. Any
setting beyond 50 will be recognized as 50%.
C K SET Front-panel thumbwheel switch provides adjustment of
the relay timing characteristic over the range of 1 to 99 in
increments of 1. Allows the relay to match the character-
istics of the protected machine. See Figure 3-2 for
characteristic curves. A setting of 00 will be recognized
as a K-setting of 100.
DMAXTIME
(
X 10 SEC
)
Front-panel thumbwheel switch provides selection of the
maximum trip time over the range of 10 to 990 seconds
in increments of 10 seconds. Refer to Figure 3-2 for
characteristic curves. A setting of 00 will be recognized
as 1000 seconds.
EPOWER
LED LED illuminates when proper operating power is applied
to the relay internal circuitry.
F TAP ADJUST Front panel mounted, 10-position rotary switch
establishes the full-load current reference level (IN) for
the application. The 5 ampere model is adjustable from
3.0 A to 5.0 A in increments of 0.2 A. The one ampere
model is adjustable from 0.6 A to 1.0 A in increments of
0.04 A.
GCAL
Adjust Provides a vernier adjustment between the selected TAP
ADJUST setting and the next lower TAP ADJUST
setting. A fully CW adjustment of the CAL control
provides the indicated TAP ADJUST setting. CCW
adjustment of the CAL control provides adjustments to
the next lower setting.
HReset Lever Provides manual reset of Target indicator.
I PUSH TO ENERGIZE
OUTPUT Pushbutton Provides manual actuation of the output contacts by
inserting a 1/8 inch diameter, non-conducting rod through
the access hole in the front panel.
JTrip Target Indicator Provides visual indication that the trip output relay has
energized. Must be manually reset.
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Locator Control or Indicator Function
2-2 BE1-46N Human-Machine Interface
KALARMLED LED illuminates when level of I2exceeds the ALARM (trip
level) setting.
L PICKUP LED LED illuminates when level of I2exceeds PICKUP (trip
level) setting.
Figure 2-1. Location of Controls and Indicators
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BE1-46N Functional Description 3-1
SECTION 3 • FUNCTIONAL DESCRIPTION
GENERAL
The following discussion is referenced to the Functional Block Diagram, Figure 3-1.
Figure 3-1. Functional Block Diagram
INPUT SENSING
Three-phase currents are applied to the negative sequence filter network which removes the zero and
positive sequence components of sensed line currents.
Resolvednegativesequencecurrents(I2)arescaledbythe TAPADJUSTswitch. TheTAPADJUSTswitch
selects resistive loading to establish per unit (pu) current values. Switch positions, A through J, select tap
values from 3.2 amperes to 5.0 amperes in increments of 0.2 ampere. The CAL potentiometer is a vernier
control for selecting tap values between the settings of the TAP ADJUST switch.
The output from the filter is applied to the analog to digital (A/D) conversion network and to the buffer
amplifier to drive the external meter (optional) for I2level monitoring.
MEASURING I2
The input from the filter network is converted to an absolute value and applied to a comparator and a times
four amplifier. The amplified output is also sent to a comparator. Both the direct and amplified values are
measured by the microprocessor. When I2values are small, the amplified output is used. This improves
resolution and accuracy.
Successive approximation measuring techniques allow the microprocessor to measure the level of I2. A
digital number with only the most significant digit set high is sent from the microprocessor to the digital to
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3-2 BE1-46N Functional Description
NOTE
Connection between relay and meter must be made using no less than a 20 AWG,
shielded, twisted pair with the shield grounded only at the relay case. (Belden
Manufacturing Company part number 9962 or equivalent is recommended.)
analog (D/A) converter. The analog output from the D/A is compared with I2by both comparators and the
results sent to the microprocessor. Based on the results of that comparison, another digital number is sent
from the microprocessor to the D/A converter. The analog output is again compared with I2and the results
sent to the microprocessor. This continues until the microprocessor number equals the I2value. The
microprocessor then compares that number with the selected inputs from the thumbwheels. When the
magnitude of I2exceeds the setting of the trip level, the microprocessor begins timing and calculates the
(i2)2dt. The microprocessor compares the continuously calculated value with the maximum permissible
heating constant K. Tripping occurs when the calculated value exceeds the K setting. If I2falls below the
pickup setting, the relay will reset at a linear rate of 2.5 seconds per percent of full scale trip time.
MICROPROCESSOR
BE1-46N relays use an 8-bit, low power, CMS microprocessor which controls all timing, measurements,
computations, and outputs.
PROGRAM MONITOR
Duringpower-up,theprogrammonitorinitializesprogramsequencing. Duringoperation,themicroprocessor
outputs a series of pulses at regular intervals. The program monitor senses these pulses and, if the pulses
are disrupted in any way, resets the microprocessor. Reset initializes the program sequence and provides
for fail safe operation.
OUTPUTS
Output relays are provided for trip and alarm functions. An auxiliary output relay is available that operates
at the same time as the trip relay. Trip and auxiliary output relays are available with either normally open
(NO) or normally closed (NC) contacts. The alarm output and oscilloscope start relays are also available
with NO or NC contacts. Power supply output contacts are monitored at the mother board. Normal supply
voltage causes the status relay to be continually energized. However, if at any time thevoltage falls below
requirements, the relay drops out, and closes the normally closed contacts.
An optional remote meter calibrated to display the magnitude of I2is a percentage of the full load current is
also available. Full scale deflection of the meter corresponds to 50%.
If this option is specified, a standard 4.5 inch switchboard type meter is available and must be ordered
separately. Specify Basler Electric part number 9 1700 00 001.
POWER SUPPLY
BaslerElectricenhancedthepowersupplydesignforunitcaserelays. Thisnewdesign created three,wide
rangepowersuppliesthatreplacethefivepreviouspowersupplies. Stylenumberidentifiersforthesepower
supplies have not been changed so that customers may order the same style numbers that they ordered
previously. The first newly designed power supplies were installed in unit case relays with EIA date codes
9638 (third week of September 1996). Relays with a serial number that consists of one alpha character
followed by eightnumerical characters also have the new wide rangepower supplies. A benefit ofthis new
design increases the power supply operating ranges such that the 48/125 volt selector is no longer
necessary. Specific voltage ranges for the three new power supplies and a cross reference to the style
number identifiers are shown in the following table.
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BE1-46N Functional Description 3-3
Heat Energy0,T(i2)2dt
Heat Energy0,T(i2)2dt <K
Heat Energy <( i2)2T
I2per unit (i2)
Full Load Stator Current
Table 3-1. Wide Range Power Supply Voltage Ranges
Power Su
pp
l
y
St
y
le Chart Identifier Nominal Volta
g
eVolta
g
e Ran
g
e
Low Range R 24 Vdc 12† to 32 Vdc
Mid Range O, P, S 48, 125 Vdc,
120 Vac 24 to 150 Vdc, 90 to 132 Vac
High Range T 125, 250 Vdc,
120, 240 Vac 62 to 280 Vdc, 90 to 270 Vac
† 14 Vdc required to start the power supply.
Relay operating power is developed by the wide range, isolated, low burden, flyback switching,solid-state
power supply. Nominal ±12 Vdc is delivered to the relay internal circuitry. Input (source voltage) for the
power supply is not polarity sensitive. A red LED turns ON to indicate that the power supply is functioning
properly.
POWER SUPPLY STATUS OUTPUT
The power supply status output relay has normally closed (NC) output contacts. This relay is energized
uponpower-upthusopeningitscontacts. Normalrelayoperatingvoltagemaintainsthepowersupplystatus
outputrelaycontinuallyenergizedanditsoutputcontactsopen. However,ifthepowersupplyoutputvoltage
falls below the requirements for proper operation, the power supply status output relay de-energizes, thus
closing the NC output contacts.
SETTING CONSIDERATIONS
As the generator is subjected to unbalanced currents, the heating of the generator can be expressed in
terms of negative sequence current and time. The following mathematical relationship defines the
permissible heat energy tolerable to the generator without causing damage:
To avoid damage to the generator, the heat energy must be less than some value K as provided by the
generator manufacturer. The K value is a machine constant representing maximum permissible heating.
This value varies depending upon the generator design. K values normally range from 4 to 40. The
allowable heat energy is then expressed as:
Or, as: the instantaneous negative sequence current is equal to some constant I2which is expressed in per
unit of full load stator current. The formula is now expressed as:
For clarification, the following definitions are included.
K = machine constant supplied by generator manufacturer representing the maximum
permissible thermal capacity of the generator rotor
T = time in seconds
i2= instantaneous negative sequence current
I2pu = negative phase sequence overcurrent expressed in per unit of full load stator current
Where:
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3-4 BE1-46N Functional Description
BE1-46N relays are featured with the following settings:
& TAP ADJUST and TAP ADJUST CAL to establish a reference level (full load stator current)
& ALARM and PICKUP
& K SET
& MAX TIME (X 10 SEC)
InReference Level
(
Ta
p
Value
)
An adjustment is provided to establish the stator full load current reference level In. This adjustment has a
range of 3.0 to 5.0 amperes. This is provided by a 10 position switch and vernier control. The switch
positions are marked from position A through J and provide a TAP VALUE as follows:
A- 3.2
B- 3.4
C- 3.6
D- 3.8
E- 4.0
F- 4.2
G- 4.4
H- 4.6
I-4.8
J - 5.00
The vernier calibration control (CAL) is provided to adjust the full load current reference level Inin between
the TAP ADJUST range settings.
Alarm and Pickup
The I2output of the filter network is applied to the alarm and trip level detector circuits. The alarm circuit
pickup adjustment is settable from 0.01 to 0.50 which represents the ratio of magnitude of the negative
sequence current to the full load current rating of the machine. The alarm circuit compares the level of I2
from thefilter network to the selected ALARM pickup setting. When I2is greater than or equal to the setting
and exists for three seconds (a fixed three second time delay), the alarm output contact closes. The alarm
setting is usually set lower than the trip level to warn the station operator that corrective action is required.
After pickup (I2pu

I2÷In), the trip level detector circuitapplies the sensed negative sequencecurrent I2pu
to the minimum and maximum trip timers and the network which integrates the value (I2)2dt equal to the
machine constant K. The minimum trip time circuitry, after a 0.2 second time delay, applies a signal to
initiate the operation of the oscillograph (optional). The maximum trip time circuitry maintains the same I
2
pu and triggers the output trip contact when the time delay expires. The setting of the maximum trip time
setting is based upon the maximum time allowed for a particular K constant. For a conventionally cooled
synchronous generator, the permissible (I2)2rating is 30 (reference C37.102-1987). Therefore, a setting of
0.35 pu would allow the generator to carry a negative sequence current condition for 245 seconds without
damage. For I2currents of less than 0.35 pu, the generator will be adequately protected.
When the value of I2 pu applied to the microprocessor integrator network falls below the pickup setting, the
integration will cease and reset at a linear rate of2.5 seconds per percent of full scale trip time. This linear
reset approximates generator cooling.
K Settin
g
The K setpoint should be set so that the (I2t characteristic of the relay matches the permissible heating
characteristic of the generator.
MAX TIME
The maximum timer function prevents negative sequence current from being above pickup for long periods
of time. The maximum timer is ORed with the inverse timer such thatif either time out occurs,the unit trips.
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BE1-46N Functional Description 3-5
Ifull load 15 MVA x 1000
3 (13.8 (KV ))
627.55 AI
full load 15 MVA x 1000
3 (13.8 (KV ))
627.55 A
Isecondary 627.56 x5
800 3.92 AI
secondary 627.56 x1
800 0.784 A
I21
3(IA.2IB.IC)
if, IBIC0
then, I2IA
3Isingle

phase
3
jI2pu I2
Inominal
1
3
Isingle

phase
Inominal
Inominal 1
3
Isingle

phase
I2pu
Isingle

phase 3(Inominal)(I2pu)
CALCULATION EXAMPLE
Assume the generator to be protected is rated:
5 Am
p
CT 1 Am
p
CT
15 MVA
13.8 kV
CT Ratio 800/5 A
15 MVA
13.8 kV
CT Ratio 800/1 A
The calculated full load current would be:
5 Am
p
CT 1 Am
p
CT
The current being applied to the relay would be:
5 Am
p
CT 1 Am
p
CT
The relay TAP ADJUST should be set for this value of full load current.
SETTING TAP ADJUST
TwomethodsforsettingtheTAPADJUSTarethesingle-phase and three-phasemethods. Ineachofthese
methods, the amount of negative sequence current atwhich the relay is to trip must be calculated and then
applied to the relay. The TAP ADJUST CAL control is then adjusted so that the PICKUP LED lights at that
amount of negative sequence current.
Method 1, Sin
g
le-Phase
If a single-phase quantity is to be applied to the relay, the following equations need to be developed and
used in the calculations.
Solvin
g
for I nominal
E
q
uation A is:
Solvin
g
for I sin
g
le-phase
E
q
uation B is:
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3-6 BE1-46N Functional Description
NOTE
For the following step, any % value can be used. In this example, 50% has been chosen
only for convenience.
Isingle

phase 3(Inominal)(I2pu)
Isingle

phase 3(3.92)(0.5)
Isingle

phase 5.88 A
Isingle

phase 3(Inominal)(I2pu)
Isingle

phase 3(0.784)(0.5)
Isingle

phase 1.176 A
NOTE
For the following step,any % value can be used. In this example, 50% has been chosen
only for convenience.
I2IAIBIC
then, 0.5 × I20.5 × IINPUT
j0.5 × 3.92 1.96 A
I2IAIBIC
then, 0.5 × I20.5 × IINPUT
j0.5 × 0.784 0.392 A
To set the nominal current value (current being applied to the relay as derived in the calculation example),
perform the following steps.
Step 1. Set theTAP ADJUST switch to the nexthigher current value (4.0 A, position E for 5 ACT or 0.80
A, position E for 1 A CT) of the desired current value (3.92 A for 5 A CT or 0.784 A for 1 A CT).
Step 2. Set the % I2PICKUP thumbwheel switch to a value of 50 (0.5 pu).
Step 3. Using equation B, solve for I single-phase.
5 Am
p
CT 1 Am
p
CT
E
q
uation B is:
Step 4. Apply the calculated I single-phase to one of the phase inputs of the relay (example, phase A input,
relaycaseterminals8,9)andadjusttheTAPCALcontrolfromafullyclockwiseposition,counter-
clockwise until the front-panel PICKUP LED is ON.
The nominal current value is now set at 3.92 amperes (for 5 A CT) or 0.784 amperes (for 1 A CT) for this
application.
Method 2, Three-Phase
If any two phases ofa balanced three phase source are rotated, Iinput = I2because a reverse phase quantity
is being applied. The relay sees this as a 100% negative sequence condition.
To set the nominal current value (current being applied to the relay as derived in the calculation example):
Step 1. Set the TAP ADJUST switch to the next higher current value (4.0 amperes, position E for 5 A CT
or 0.80 amperes, position E for1 A CT) of the desired current value (3.92 amperes for 5 A CT or
0.784 amperes for 1 A CT).
Step 2. Set the % I2PICKUP thumbwheel switch to a value of 50 (0.5 pu)
Step 3. If applying A-C-B sequence,
5 Am
p
CT 1 Am
p
CT
Step 4. Apply 1.96 amperes (for 5 A CT) or 0.392 amperes (for 1 A CT), and adjust the TAP CAL control
from a fully clockwise position, counter-clockwise until the front-panel PICKUP LED is ON.
The nominal current value is now set at 3.92 amperes (for 5 A CT) or 0.784 amperes (for 1 A CT) for this
application.
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BE1-46N Functional Description 3-7
I2I1
X0
X2X0
I21.0 ×1.6
1.0 1.6 0.62 p.u.
30
(0.62)278 sec.
FURTHER CONSIDERATIONS
(
FOR 5 AMP CT
)
RelayPickupshouldbebasedonseries unbalances,particularlyanopenphase,ratherthanonunbalanced
faults. The limiting case for pick-up settings may be an open beyond the generator leads where the
negative-sequence current is distributed among several generators. This is in contrast to an open pole on
the generator breaker, where the total negative sequence current resulting from the open flows in the
generator being protected.
Ref. 1 specifies the continuous negative sequence current limit in per unit after 120 seconds as:
Salient Pole With connected dampers 0.10
With unconnected dampers 0.05
C
y
lindrical Rotor Indirectl
y
cooled 0.10
Directl
y
cooled to 960 MV A 0.08
961 to 1200 MV A 0.06
1201 to 1500 MV A 0.05
Assume an indirectly cooled cylindrical rotor generator and setPICKUP (trip unit) at 0.06 or 6%. Set alarm
pickup below the PICKUP value (trip unit), but above maximum expected unbalance due to untransposed
lines, etc. : at 4%. Assume that the manufacturer or the ANSI standard has specified a K factor of 30. Set
K = 30.
The maximum negative-sequence current I2for an open phase occurs when the open is in the generator
leads whether at the generator voltage or on the high side of the unit transformer. Current I2for this case
can be approximated:
E
q
uation C is:
where:
X2=ne
g
ative-se
q
uence reactance of an entire s
y
stem, includin
g
the
g
enerator
X0= zero-se
q
uence reactance of s
y
stem connected to an open phase
I1= positive se
q
uence current
Assume that X0= 1.6 times X2and I1= 1.0 p.u. Then, from Equation C:
Then, 0.62 p.u. is approximately the maximum expected current for an open phase for this case. At this
level, the inverse delay based on I22t = K = 30 will be:
The operator will probably not react fast enough in reducing loading to prevent tripping with a 78 second
relay delay. However, at lower levels the alarm unit may provide sufficient advanced warning to allow
effectiveoperatorcorrective action. Accordingly,theMAXTIMEsettingshouldpermit suchpossibleaction.
Set MAX TIME at 500 seconds (8.3 minutes).
Reference1. IEEECommitteeReport,
AStandardforGeneratorContinuousUnbalancedCurrentCapability
,IEEE Transactions,
PAS 92, No. 5, Sept./Oct. 1973, pp 1547-49.
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3-8 BE1-46N Functional Description
FURTHER CONSIDERATIONS
(
FOR 1 AMP CT
)
To determinethenegative sequencecurrentpickup setting, calculate thesensitivity required to insurerelay
operation at the expected minimum load condition with one pole of the generator breaker open. Assume
the value of negative sequence current under this condition is 0.14 A(secondary) or 0.18per unit. then for
our example, the relay must be atleast this sensitive. This value must be considered as the upper limit for
the pickup setting. A lower setting is recommended. For this example, a value of 12 percent (0.12 per unit)
will be used. Set the PICKUP thumbwheel to this value.
To set the value for the ALARM level of negative sequence current, it is only necessary to determine the
level that will give an operator sufficient time to attempt to correct the condition. A value of 08 may be set
on the thumbwheel.
The K value for this example has been provided by the generator manufacturer. Set this value (25) on the
K SET thumbwheel.
The MAX TIME thumbwheel establishes the maximum time allowed for the negative sequence current
tripping condition (defined by the PICKUP setting) to persist. If it is determined that this value is 500
seconds, set the thumbwheel at 50.
Since (I2)2t = K establishes the limit of operation, t = 25 divided by 0.122= 1736 seconds.
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