Basler Electric BE1-CDS240 General Information
SECTION 1 • GENERAL INFORMATION
TABLE OF CONTENTS
SECTION 1 • GENERAL INFORMATION ................................................................................................ 1-1
Introduction ............................................................................................................................................ 1-1
Features ................................................................................................................................................. 1-1
I/O Functions ...................................................................................................................................... 1-2
Protection and Control Functions ....................................................................................................... 1-3
Metering Functions ............................................................................................................................. 1-4
Reporting and Alarm Functions .......................................................................................................... 1-4
BESTlogic Programmable Logic ........................................................................................................ 1-6
Security............................................................................................................................................... 1-6
Human-Machine Interface .................................................................................................................. 1-6
ASCII Command Interface ................................................................................................................. 1-6
Installation .......................................................................................................................................... 1-7
Testing and Maintenance ................................................................................................................... 1-7
BESTCOMS™ Software ..................................................................................................................... 1-7
Primary Applications .............................................................................................................................. 1-7
Differential Protection Application Considerations ................................................................................. 1-8
Problem 1: False Differential Current Due to Poor CT Performance ................................................. 1-8
Problem 2: Measured Current Magnitude Mismatch ......................................................................... 1-9
Problem 3: Mismatch Caused by Load Tap Changers ...................................................................... 1-9
Problem 4: Phase Angle Shift .......................................................................................................... 1-10
Problem 5: Zero-Sequence Current Sources Within the Zone of Protection ................................... 1-13
Problem 6: Transformer Energization Inrush and Overexcitation .................................................... 1-15
Problem 7: Digital Measurement Errors ........................................................................................... 1-15
Model and Style Number Description .................................................................................................. 1-16
Sample Style Number ...................................................................................................................... 1-16
Operational Specifications ................................................................................................................... 1-17
Metered Current Values and Accuracy ............................................................................................ 1-17
Metered Voltage Values and Accuracy ............................................................................................ 1-17
Metered Frequency Values and Accuracy ....................................................................................... 1-17
Calculated Values and Accuracy ..................................................................................................... 1-17
Energy Data Reporting ..................................................................................................................... 1-18
24 Overexcitation Protection ............................................................................................................ 1-18
27P Phase Undervoltage Protection ................................................................................................ 1-18
47 Negative-Sequence Voltage Protection ...................................................................................... 1-18
50T Instantaneous Overcurrent Protection ...................................................................................... 1-19
50BF Breaker Failure Protection ...................................................................................................... 1-19
51 Time Overcurrent Protection ....................................................................................................... 1-20
59P Phase Overvoltage Protection .................................................................................................. 1-20
59X Auxiliary Overvoltage Protection ............................................................................................... 1-20
60FL Fuse Loss ................................................................................................................................ 1-20
62 Logic Timers ................................................................................................................................ 1-20
81 Frequency Protection .................................................................................................................. 1-21
87 Current Differential Protection ..................................................................................................... 1-21
87ND Neutral Differential Protection ................................................................................................ 1-22
Automatic Setting Group Characteristics ......................................................................................... 1-22
BESTlogic ......................................................................................................................................... 1-22
General Specifications ......................................................................................................................... 1-22
AC Current Inputs ............................................................................................................................. 1-22
Analog to Digital Converter .............................................................................................................. 1-23
Power Supply ................................................................................................................................... 1-23
Output Contacts ............................................................................................................................... 1-23
Contact-Sensing Inputs .................................................................................................................... 1-23
IRIG .................................................................................................................................................. 1-24
Real-Time Clock ............................................................................................................................... 1-24
9365200990 Rev M BE1-CDS240 General Information i
Communication Ports ....................................................................................................................... 1-24
Display .............................................................................................................................................. 1-25
Isolation ............................................................................................................................................ 1-25
Surge Withstand Capability .............................................................................................................. 1-25
Radio Frequency Interference (RFI) ................................................................................................ 1-25
Electrostatic Discharge (ESD) .......................................................................................................... 1-25
Shock ................................................................................................................................................ 1-25
Vibration ........................................................................................................................................... 1-25
Environment ..................................................................................................................................... 1-25
UL Recognition ................................................................................................................................. 1-25
C.S.A. Certification ........................................................................................................................... 1-25
GOST-R Certification ....................................................................................................................... 1-25
Patent ............................................................................................................................................... 1-25
Physical ............................................................................................................................................ 1-26
Figures
Figure 1-1. Restrained Differential Characteristic ..................................................................................... 1-8
Figure 1-2. Tap Adjust for Mismatch ......................................................................................................... 1-9
Figure 1-3. Currents on Different Voltage Bases ...................................................................................... 1-9
Figure 1-4. Delta/Wye Transformer Circuits ............................................................................................ 1-11
Figure 1-5. Three-Phase Connections, Delta-Wye Configuration, CT Compensation ............................ 1-12
Figure 1-6. Three-Phase Connections, Delta-Wye Configuration, Internal Phase Compensation ......... 1-13
Figure 1-7. Traditional Zero-Sequence Trap for Application with Ground Banks ................................... 1-14
Figure 1-8. Style Number Identification Chart ......................................................................................... 1-16
Figure 1-9. Typical 87 Response Characteristic Curves ......................................................................... 1-22
Tables
Table 1-1. Contact-Sensing Turn-On Voltages ....................................................................................... 1-23
Table 1-2. Contact-Sensing Input Burden ............................................................................................... 1-24
ii BE1-CDS240 General Information 9365200990 Rev M
SECTION 1 • GENERAL INFORMATION
Introduction
The BE1-CDS240 Current Differential System is an economical, microprocessor based, multifunction
system that provides a four input, three-phase percentage differential with harmonic restraint protection.
Also included is three-phase with voltage control, ground, and negative-sequence overcurrent protection,
voltage and frequency protection, breaker failure for up to four breakers, breaker monitoring for four
breakers, transformer monitoring, and metering functions, all in an integrated system with several
communications options. The BE1-CDS240 Current Differential System is intended for use in any low
impedance current differential protection application including transformer, generator, motor, and bus
protection. Four setting groups are provided for adaptive relaying with automatic selection logic for cold
load pickup and/or dynamic setting group changes.
The BE1-CDS240 can be ordered with 12 programmable contact sensing inputs, 10 programmable
outputs, and one alarm output or eight programmable contact-sensing inputs, 14 programmable outputs
and one alarm output. Outputs can be assigned various functions by logical programming to perform
protection, control, or indicate operations. For example, protection functions can cause a protective trip
operation. Control functions can cause a manual trip, manual close, or automatic reclose operation.
Indicators could be relay alarm, setting group one enable, setting group two enable and others.
Protection scheme designers may select from an embedded pre-programmed logic scheme or from a
number of logic library schemes found in BESTCOMS™ to perform the most common protection and
control requirements or create a custom scheme using BESTlogic.
The BE1-CDS240 is available in a fully draw-out MX case with configurations for horizontal 19" rack
mounting, horizontal panel mounting and vertical panel mounting. BE1-CDS240 features include:
• Up to four restraint inputs (four three-phase current circuits) and two virtual current circuits
that can be used with any combination of two current inputs
• Independent ground input
• Three voltage inputs (Va, Vb, Vc, to Vn)
• Three-phase percentage differential protection with harmonic restraint
• Three-phase voltage, frequency and overcurrent protection
• Four setting groups
• One embedded preprogrammed logic scheme
• Fourteen or 10 programmable outputs
• Eight or 12 contact sensing inputs
• Breaker failure protection for four breakers
• Front panel HMI (human-machine interface)
• Communications ports: one front RS-232, one rear RS-232, one rear RS-485 and one rear
IRIG port
• Communications protocols available: DNP3, Modbus™ RTU, and ASCII
• Sequence of events recording
• Fault recording
• Oscillography
• Demand reporting
• Differential current monitoring
• Optional load profile reporting
Section 2, Quick Start, provides BE1-CDS240 Current Differential System users with a simplified, "How
To Get Started" procedure.
Features
The BE1-CDS240 includes many features for the protection, monitoring, and control of power system
equipment such as transformers, breakers, buses, generators, and motors. These features include
9365200990 Rev M BE1-CDS240 General Information 1-1
protection and control functions, metering functions, reporting and alarm functions, and various
communication options. A highly flexible programmable logic system called BESTlogic allows the user to
apply the available functions with complete flexibility and customize the system to meet the requirements
of the protected power system. Programmable I/O, extensive communications features, and an advanced
HMI (human machine interface) provide easy access to the features provided. Through BESTCOMS
software, BE1-CDS240 users with personal computers (PCs) have another easy-access means to
communicate, program, control, and monitor relay/system performance. BESTCOMS is a Windows®
(based software application that enhances communication between the PC user and the BE1-CDS240
relay. This software is provided free with every BE1-CDS240 relay. Another software application tool is
BESTWAVE. BESTWAVE is a utility program to view standard COMTRADE (Common Format for
Transient Data Exchange) files like those recorded by Basler Electric multifunction relays.
The following information summarizes the features included in this multifunction device. The organization
of this information outlines the organization for the rest of the manual. Each feature, along with how to set
it up and how to use the outputs is described in complete detail in the later sections of this manual.
I/O Functions
Power System Measurement Functions
• The BE1-CDS240 has four sets of three-phase currents that are digitally sampled and digitally
filtered. The fundamental, second, and fifth harmonics are extracted using a Discrete Fourier
Transform (DFT) algorithm for use by all of the current based functions.
• Neutral (residual) and negative-sequence current magnitudes are calculated from each set of
three-phase currents.
• Each set of three-phase currents can be phase-shifted and tap compensated for use in
transformer differential applications.
• Each three-phase current source can have its polarity reversed in the relay, which simplifies the
commissioning process in the event polarity of a CT circuit is rolled.
• The digital sampling rate tracks the measured frequency to provide high accuracy at frequencies
other than nominal frequency to make this relay ideally suited for applications such as generator,
motor and generator step-up transformer differential protection.
• An independent ground current input (IG) measures the current in a transformer neutral, tertiary
winding or a flux balancing CT and is used for providing ground differential protection.
• Each current circuit is low burden and isolated to allow for more effective zoning with fewer costly
CTs.
• Three-phase voltage inputs are digitally sampled and the fundamental frequency is extracted
using a Discrete Fourier Transform (DFT) algorithm. Voltage sensing circuits can be configured
for single-phase, three wire or four wire voltage transformer circuits.
Voltage sensing circuitry provides voltage protection, frequency protection, and watt/var
metering. Neutral (residual), positive, negative, and zero sequence voltage magnitudes are
calculated from the three-phase voltages.
Contact Sensing Inputs
• Eight (I/O option E) or 12 (I/O option A) programmable contact sensing inputs with programmable
signal conditioning provide binary logic interface to the protection and control system.
• The function of each input is programmable using BESTlogic and can be given a user meaningful
name for the variable and for each state (open and closed) for use in reporting functions.
• The threshold voltage is adjustable. See Section 12, Installation, Contact Sensing Input Jumpers.
Contact Outputs
• Fourteen (I/O option E) or 10 (I/O option A) programmable contact outputs provide a binary logic
interface to the protection and control system (OUT1 through 14). OUTA is dedicated to critical
alarms.
• OUT1 and 2 are dedicated form “c” contacts. The remainders are “a” contacts. Outputs 7, 8, 9, 10
are dedicated to trip coil monitoring for up to 4 breakers. However, board level jumpers are
supplied so that the user can disable the TCM circuit and allocate the output contact to any virtual
output. Refer to Section 12, Installation, Trip Coil Monitor (TCM) Jumpers.
1-2 BE1-CDS240 General Information 9365200990 Rev M
• Each output is programmable using BESTlogic (assign any virtual output to any physical output
relay) and can be given a user meaningful name for the variable and for each state (open and
closed) for use in reporting functions.
• Output logic can be overridden to open, close or pulse each output contact for testing, or control
purposes.
Protection and Control Functions
Setting Groups
• Four (4) settings groups allow adaptive relaying to be implemented to optimize the relay settings
for various operating conditions.
• Automatic and external logic can be employed to select the active setting group.
Differential Protection
• Three-phase percentage restrained differential protection with harmonic restraint: 87. Protection
can be set to monitor two, three, or four windings. Unused inputs can be used for overcurrent
protection.
• Two restricted earth fault ground differential protection elements with independent ground (IG)
input (and C-phase, IG2, of Current Circuit 4): 87ND and 187ND.
• Tap compensation for the differential protection can be automatically calculated by the relay
based upon user settings of CT ratio, MVA and kV base values.
• Ground differential between calculated residual of any winding and the phase C current input of a
fourth and unused winding (IG2).
• Each winding can be independently set for a phase relationship (relative to winding 1) of 0 to 360
degrees in steps of 30 degrees.
• Each winding can be set for IEC standard transformer connections.
Overcurrent Protection
• Instantaneous overcurrent with settable time delay for each operating quantity (A, B, C, N (using
IN or IG) and Q. Eight (8) sets Phase, Five (5) sets Neutral, Four (4) sets Negative-Sequence.
Each function is individually assignable to any of the current input circuits. Functions are: 50TP,
150TP, 250TP, 350TP, 450TP, 550TP, 650TP, 750TP, 50TN, 150TN, 250TN, 350TN, 450TN,
50TQ, 150TQ, 250TQ, and 350TQ.
• Inverse time overcurrent functions with integrating or instantaneous reset. Four (4) for Phase, five
(5) for Neutral, and four (4) for Negative-Sequence. Each function is individually assignable to
any of the current input circuits. Functions are 51TP, 151TP, 251TP, 351TP, 51TN, 151TN,
251TN, 351TN, 451TN, 51TQ, 151TQ, 251TQ, and 351TQ.
• Time overcurrent functions employ a dynamic integrating timing algorithm covering a range from
pickup to 40 times pickup with selectable instantaneous or integrated reset characteristics.
• Time overcurrent curves conform to IEEE PC37.112 and include seven curves similar to
Westinghouse/ABB CO curves, five curves similar to GE IAC curves, four IEC curves, a fixed
time curve, and a user programmable curve.
• Digital signal processing filters out unwanted harmonic components while providing fast
overcurrent response with limited transient overreach and overtravel.
Voltage Protection
• Voltage control or restraint for 51P (51V protection)
• One (1) volts per hertz protective element (24) provides overexcitation protection for a generator
and/or transformer.
• Two phase (2) undervoltage elements, 27P and 127P, provide phase undervoltage protection.
• Two phase (2) overvoltage elements, 59 and 159, provide phase overvoltage protection.
• One (1) negative-sequence overvoltage element (47) provides protection for phase unbalance or
a reverse system phase-sequence.
• One (1) zero sequence overvoltage element (59X) provides protection for ground faults on
ungrounded systems using calculated 3VO.
Frequency Protection
• Six (6) over/underfrequency protection elements are provided: 81, 181, 281, 381, 481, and 581.
9365200990 Rev M BE1-CDS240 General Information 1-3
Fuse Loss Protection
• A fuse loss function, 60FL, protects against false tripping due to a loss of voltage sensing.
Breaker Failure Protection
• Four (4) breaker failure protection function blocks are assignable to any of the current input
circuits: 50BF, 150BF, 250BF, and 350BF.
• The current circuit assigned to the breaker failure function block also determines which current
circuit is used by the breaker monitoring functions described later.
General Purpose Logic Timers
• Four (4) general-purpose logic timers with six modes of operation: 62, 162, 262, and 362.
Virtual Control Switches
• Four (4) virtual breaker control switch, accessible locally from the HMI or remotely from the
communications ports can be used to provide trip and close control of a selected breaker: 101,
101A, 101B, and 101C.
• The breaker label provided for the breaker monitoring function is used to label the virtual breaker
control switch. This makes it easily discernible which breaker is being controlled as up to four (4)
breakers can be controlled.
• Eight virtual switches with three modes of operation, accessible locally from the HMI or remotely
from the communications ports. Switches can be used to provide additional control: for example,
to trip and close additional switches or breakers, or to enable and disable certain functions: 43,
143, 243, 343, 443, 543, 643, and 743.
Metering Functions
• Metering, including magnitude and angle, is provided for all measured phase and neutral voltage
and currents and all derived positive, neutral, and negative-sequence voltage and currents.
Power factor, frequency, watts, vars, and demands are also provided.
• Metering, including magnitude and angle, is also provided for the phase and tap compensated
restraint, second and fifth harmonic, and differential currents.
Reporting and Alarm Functions
Relay Identification
• The relay includes four 30-character, free-form fields for the user to enter information to identify
the relay. Examples would be station name, circuit number, relay system, purchase order, etc.
These fields are used by many of the reporting functions to identify which relay created the report.
Clock
• A real-time clock is included with a capacitor backup that will keep time upon loss of power for 8
to 24 hours depending upon conditions. Optional battery backup maintains time keeping for an
extended period.
• A standard IRIG input (format B002 from IRIG Standard 200-98) is provided for receiving time
synchronism signals from a master clock.
• The time and date reporting format is settable for 12 or 24-hour format and for mm/dd/yy or
dd/mm/yy format.
• Automatic daylight savings time adjustment can be enabled.
• Recording of time or date changes made via Modbus or DNP to the sequence of events can be
enabled.
General Status Reporting
• The relay has extensive capability to report its general status for monitoring, commissioning, and
troubleshooting.
• Status reports are available from the HMI or the communications ports.
Demand Reporting
• Ampere demand registers are provided for monitoring A, B, C, N, and Q. These registers are
assignable to any of the current input circuits.
1-4 BE1-CDS240 General Information 9365200990 Rev M
• The demand interval and demand calculation method is separately settable for phase, neutral
and negative-sequence measurements.
• The demand reporting function records today's peak, yesterday's peak, and peak since reset,
with time stamps for each register.
• An optional 4,000-point data array can record over 40 days of 15-minute demand data.
Differential Current Monitoring
• A detailed current check record can be requested from the relay to aid in initial in-service
readings to verify correct phase and tap compensation of the differential currents. This report can
be stored with commissioning records to save time during initial check out.
• Once in service, the mismatch in the differential function is continuously monitored and can
provide an alarm if the mismatch is approaching a trip condition due to loading current. A current
check record is generated when this occurs and the diagnostic function will indicated the possible
source of the mismatch: for example, incorrect or missing phase compensation.
Transformer Monitoring
• Transformer through-fault duty statistics are recorded including number of through faults,
accumulated through-fault (It or I2t), and maximum through-fault (It or I2t). The through-fault
current measurement is assignable to any of the current input circuits.
• Each of these conditions can be set to alarm.
Breaker Monitoring
• Breaker statistics are recorded for up to four breakers. They include the number of operations,
fault current accumulation duty and breaker time to trip. This function is associated with the
current input circuit assigned to the breaker failure function block.
• Each of these conditions can be set to alarm.
Trip Circuit Monitoring
• Four trip circuit monitor functions are provided to monitor the trip circuit of a breaker or lockout
relay for loss of voltage (fuse blown) or loss of continuity (trip coil open).
• Each of the four TCMs can be disabled with a circuit board jumper allowing the associated output
to operate the same as the other outputs.
Fault Reporting
• Fault reports consist of simple target information, fault summary reports, and detailed
oscillography records to enable the user to retrieve information about disturbances in as much
detail as is desired.
• Oscillography memory can be partitioned into 6 to 16 records and all data is stored in non-volatile
memory.
• The relay records and reports oscillography data in industry standard IEEE, COMTRADE format
to allow using any fault analysis software.
Sequence Of Events Recorder
• A 255-event sequence of events recorder (SER) is provided that records and time stamps all
inputs and outputs to the relay as well as all alarm conditions monitored by the relay. Time
stamps are to the nearest quarter cycle resolution. All records are stored in non-volatile memory.
• I/O and Alarm reports can be extracted from the records as well as reports of events recorded
during the time span associated with a specific fault report.
Alarm Function
• The relay includes extensive self-diagnostics. Fatal relay trouble alarms are not programmable
and are dedicated to the alarm output (OUTA) and the relay trouble LED on the front of the relay.
• Additional relay trouble alarms and all other alarm functions are programmable for major or minor
priority. Programmed alarms are indicated by major and minor alarm LEDs on the front of the
relay. The major and minor alarm points can also be programmed to any output contact including
OUTA.
• The HMI provides local annunciation of programmed alarm conditions.
• Active alarms can be read and reset from the optional HMI or from the communications ports.
9365200990 Rev M BE1-CDS240 General Information 1-5
• Seventy (70) alarm conditions are available to be monitored including user definable logic
conditions using BESTlogic.
Version Report
• The version of the embedded software (firmware) is available from the front panel interface HMI
or the communications ports.
• The unit serial number and style number is also available from the communications ports.
BESTlogic Programmable Logic
• Each of the protection and control functions in the BE1-CDS240 is implemented in an
independent function that is equivalent to its single function, discrete device counterpart so that it
is immediately familiar to the protection engineer. Each independent function block has all of the
inputs and outputs that the discrete component counterpart might have.
Programming BESTlogic is equivalent to choosing the devices required by your protection and
control scheme and drawing schematic diagrams to connect the inputs and outputs to obtain the
desired operational logic.
• One preprogrammed embedded logic scheme (in the relay firmware) and a library of
preprogrammed logic schemes in BESTCOMS are provided and thoroughly documented in
Section 8, Applications. To set the relay to one of the BESTCOMS library applications, simply
select the logic scheme and upload it to the relay.
• A set of custom logic settings is also available for you to optimize the functionality to the specific
needs of your operation's practices and power system requirements.
Security
• Security can be defined for three distinct functional access areas: Settings, Reports, and Control.
Each functional access area can be assigned a password. A global password provides access to
all three functional areas. Each of these four passwords can be unique or multiple functional
access areas can have the same password.
• Allowing the user to restrict access to any of the three functional access areas from only specific
communication ports provides a second dimension of security. For example, you could set
security to deny access to control commands from the rear RS-232 port that is connected through
a modem to a telephone line.
• Security settings only affect write access. You have read access from any port to any area.
Human-Machine Interface
• Each BE1-CDS240 comes with a front panel display with LED (light emitting diode) indicators for
power, relay trouble alarm, minor alarm, major alarm, and trip. Each BE1-CDS240 also comes
with the software application program BESTCOMS for the CDS240. This program is a user
friendly, Windows based program that makes relay setup and support very easy.
• The programmable graphical LCD (liquid crystal display) allows the relay to replace local
indication and control functions such as panel metering, alarm annunciation, and control
switches.
• The human-machine interface (HMI) is set up in a menu tree with four scrolling buttons for
navigation. Edit and Reset pushbuttons provide access to change parameters and reset targets,
alarms and other registers. Scrolling buttons are used for data entry when in edit mode. Edit
mode is indicated by an LED on the Edit button.
• The LCD has automatic priority logic to govern what is being displayed on the screen so that
when an operator approaches, the information of most interest is automatically displayed without
having to navigate the menu structure. The priorities are targets, then alarms and then the
programmable automatic scrolling list.
• Up to 16 screens can be defined in the programmable, automatic scroll list.
ASCII Command Interface
• Three (3) independent, isolated communications ports provide access to all functions in the relay.
Com 0 is a 9-pin RS-232 port located on the front of the case. Com 1 is a 9-pin RS-232 port
located on the back of the case. Com 2 is a three-terminal, RS-485 port located on the back of
the case.
1-6 BE1-CDS240 General Information 9365200990 Rev M
• Standard communications is an ASCII command interface to allow easy interaction with the relay
using standard, off the shelf, communications software.
• The ASCII command interface is optimized to allow automating the procedure for setting the relay
by allowing settings files to be captured from the relay and edited using any software that
supports *.txt file format. These ASCII *.txt files can then be used to set the relay using the send
text file function of the communications software.
• Modbus and other common protocols are optionally available for the RS-485 communications
port. A separate instruction manual appropriate for the protocol comes with each unit. Consult the
product bulletin or the factory for availability of these options and instruction manuals.
Installation
• The BE1-CDS240 is available in two, fully draw-out, case styles; MX vertical can be mounted as
an M1, M2, FT31, or an FT32. MX horizontal units can be panel mounted or 19" rack mounted.
• Relay terminals are clearly marked on the rear panel.
Testing and Maintenance
• Four (4) testing methods are covered in this manual: acceptance testing, commissioning testing,
periodic testing, and functional testing.
• The relay also provides a virtual testing function that allows the user to isolate a portion of the
logic program and test it by using a set of switches.
BESTCOMS™ Software
• BE1-CDS240 BESTCOMS is a 32-bit Windows based graphical user interface (GUI). It provides
the user with point-and-click capability for applying settings to the relay. This facilitates setting the
relay by eliminating the need for the user to be thoroughly knowledgeable of the ASCII
commands associated with the relay settings.
Primary Applications
The BE1-CDS240 Current Differential System provides percentage restrained differential protection along
with multiple overcurrent elements and is intended for use in any low impedance current differential
protection application including transformer, generator, motor, reactor, and bus protection. Its unique
capabilities make it ideally suited for applications with the following requirements.
• Applications that require low burden to extend the linear range of CTs.
• Applications where dedicated CTs for the differential are not available. Unlike traditional
differential relays, dedicated CT circuits are not required because each CT input is isolated from
the others and phase shift compensation can be accomplished internally.
• Applications that require high accuracy across a wide frequency range such as motor, generator,
and generator step-up transformer protection or in co-generation facilities.
• Applications that require the flexibility provided by wide settings ranges, multiple setting groups
and multiple coordination curves in one unit.
• Applications that require the economy and space savings provided by a multifunction, multi-phase
unit. This one unit can provide all of the protection, as well as, the local and remote indication,
metering and control required on a typical circuit.
• Applications that require harmonic restraint to aid security for the differential.
• Applications that require communication capability and protocol support.
• Applications where the optional case configurations facilitate modernizing protection and control
systems in existing substations.
• Applications where the capabilities of a digital multifunction relay are required, yet draw-out
construction is also desirable.
• Applications where bus protection is provided by a high-speed overcurrent-blocking scheme on
the transformer bus mains instead of dedicated bus differential circuit.
• Applications where the capabilities of intelligent electronic devices (IEDs) are used to decrease
relay and equipment maintenance costs.
9365200990 Rev M BE1-CDS240 General Information 1-7
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