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Claims  |
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We claim:
1. A tripping system for interrupting electric current flowing through at
least one conductor from a source of electrical energy to a load,
comprising:
a tripping unit having
a current sensor for measuring the current, and
processing means, responsive to the current sensor, for disconnecting the
load from the source if the measured current exceeds a predetermined
threshold and for transmitting data representing the status of the
tripping unit,
said processing means including means for dividing data to be transmitted
into a more critical data set and a less critical data set and for
transmitting said more critical data set more frequently than said less
critical data set;
a data path, coupled to the tripping unit, for carrying the transmitted
data from the tripping unit; and
a peripheral device, coupled to the data path, for receiving the data
transmitted by the tripping unit.
2. A tripping system, according to claim 1, further including a second
peripheral device coupled to the data path for monitoring and displaying
the status of the data transmitted on the data path.
3. A tripping system, according to claim 1, wherein the peripheral device
includes a local monitoring unit for monitoring the data transmitted by
the tripping unit and means for commanding the tripping unit to interrupt
the flowing current.
4. A tripping system for interrupting electric current flowing through at
least one conductor from a source of electrical energy to a load,
comprising:
a plurality of tripping units, each unit having
a current sensor for measuring the current flowing through one or more
associated conductors,
processing means, responsive to the current sensor, for disconnecting the
load from the source if the measured current exceeds a predetermined
threshold and for transmitting a first data set and second data set, at
least the first data set representing the status of the tripping unit;
wherein said processing means transmits the first data set more frequently
than said second data set;
a plurality of data paths, each coupled to an associated one of the
tripping units, for carrying the transmitted data from the associated
tripping units; and
a plurality of monitoring units, each monitoring unit being coupled to a
respective one of the data paths, for analyzing the transmitted data from
the tripping units.
5. A tripping system, according to claim 4, wherein each of the monitoring
units receives the data from the associated tripping unit at a rate that
is independent of the rate at which the data is transmitted from the
tripping unit.
6. A tripping system, according to claim 4, wherein each of the monitoring
units includes means, responsive to the transmitted data, for monitoring
the measured current and for commanding the associated tripping unit to
interrupt the flowing current by sending a tripping signal to the
associated tripping unit.
7. A tripping system, according to claim 6, further including a central
computer, coupled to each of the monitoring units, for monitoring the
status of the plurality of tripping units and for setting trip parameters
in the associated local monitoring unit.
8. A tripping system, according to claim 6, wherein each tripping unit
further includes means for delaying the transmission of the data for a
predetermined time period to allow the associated monitoring unit to
receive the data at a slower rate than the rate at which the data is
transmitted.
9. A tripping system for interrupting electric current flowing through at
least one conductor from a source of electrical energy to a load,
comprising:
a tripping unit, powered by the flowing current, having
a current sensor for measuring the current,
processing means, responsive to the current sensor, for disconnecting the
load from the source if the measured current exceeds a predetermined
threshold and for transmitting data in prioritized sets wherein more
critical data sets, including information representative of said
predetermined threshold, are transmitted more frequently than less
critical data sets;
a data path, coupled to the tripping unit, for carrying the transmitted
data from the tripping unit; and
a peripheral device, coupled to the data path, for receiving the data
transmitted by the tripping unit so that at least the more critical data
sets are received before the tripping unit loses power.
10. A tripping system, according to claim 9, wherein the data path carries
the data in a serial stream.
11. A tripping system for interrupting electric current flowing through at
least one conductor from a source of electrical energy to a load,
comprising:
a tripping unit having
a current sensor for measuring the current,
processing means, responsive to the current sensor, for transmitting data
in prioritized sets wherein more critical data sets are transmitted more
frequently than less critical data sets and for disconnecting the load
from the source in response to a trip event in which the measured current
exceeds a predetermined threshold;
a data path, coupled to the tripping unit, for carrying the transmitted
data from the tripping unit; and
a peripheral device, coupled to the data path, including a processor for
receiving the data transmitted by the tripping unit at a rate that is
independent of the rate at which the data is transmitted from the tripping
unit.
12. A tripping system, according to claim 11, wherein the processing means
includes:
means for determining the cause of the trip event; and
means for dividing the data into a first set and a second set, wherein the
first set represents the cause of the trip event and is processed as the
more critical data.
13. A tripping system for interrupting electric current flowing through at
least one conductor from a source of electrical energy to a load,
comprising:
a tripping unit having
a current sensor for measuring the current,
processing means, responsive to the current sensor, for disconnecting the
load from the source if the measured current exceeds a predetermined
threshold and for transmitting data representing the status of the
tripping unit;
said processing means including means for dividing data to be transmitted
into a more critical data set and a less critical data set and for
transmitting said more critical data set more frequently than said second
data set;
a data path, coupled to the tripping unit, for carrying the transmitted
data from the tripping unit;
a monitoring unit, coupled to the data path, for receiving the data
transmitted by the tripping unit and for commanding the the tripping unit
to interrupt the current between the load and the source; and
a central computer, capable of sending data to and receiving data from the
monitoring unit, for monitoring the status of the tripping unit and for
setting trip parameters in the monitoring unit.
14. A tripping system, according to claim 13, wherein the data is received
by the monitoring unit at a rate that is independent of the rate at which
the data is transmitted from the tripping unit.
15. A tripping system, according to claim 13, wherein the monitoring unit
further includes nonvolatile memory.
16. A tripping system, according to claim 13, wherein the nonvolatile
memory is in the form of electrically erasable programmable only memory
(EEPROM).
17. A tripping system for interrupting electric current flowing from a
three-phase source of electrical energy to a three-phase motor,
comprising:
a tripping unit, which is powered by said flowing current, having
first, second and third current sensors for measuring the current in each
corresponding phase of the current,
processing means, responsive to the current sensors, for disconnecting the
three-phase motor from the three-phase source in response to an event in
which the measured current exceeds a preprogrammed parameter and for
transmitting data representing the status of the tripping unit;
said processing means including means for dividing said data to be
transmitted into a more critical data set and a less critical data set and
for transmitting said more critical data set more frequently than said
second data set and wherein the more critical data set represents the
cause of said event;
a data path, coupled to the tripping unit, for carrying the transmitted
data from the tripping unit; and
a peripheral device, coupled to the data path, for receiving the data
transmitted by the tripping unit so that at least the more critical data
sets are received before the tripping unit loses power;
wherein the peripheral device receives the data from the tripping unit at a
rate that is independent of the rate at which the data is transmitted from
the tripping unit. |
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Claims |
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Description |
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FIELD OF THE INVENTION
The invention relates to circuit breakers operated by a microprocessor, and
more particularly to a network having a plurality of circuit breakers
communicating with a computer.
BACKGROUND OF THE INVENTION
A circuit breaker is used to disconnect an electrical circuit from a supply
of electric energy in the event that too much electric current flows in
the electrical circuit. In applications such as the electrical
distribution system of a factory it is necessary to utilize a complex
system of main electrical feeder lines providing electrical energy for a
large number of branch circuits. Each of the main electrical feeder lines
must be protected by a circuit breaker. Also each of the branch circuits
must be protected by a circuit breaker. Additionally, it is convenient to
provide tie lines between feeder circuits so that a feeder line which
loses power may be alternatively supplied by a different feeder line which
remains capable of supplying electrical power. And it is convenient to
provide the tie connection with a protective circuit breaker in order to
protect the associated circuits from over current and short circuit
conditions.
A microcomputer may be incorporated in a circuit breaker design in order to
give the circuit breaker intelligence so that switching operations may be
simplified. However, a problem not solved by present designs of
microcomputer containing circuit breakers is that no provision has been
made for a communications network having circuit breakers communicating
with a central control point.
SUMMARY OF THE INVENTION
The invention is a network of microprocessor operated circuit breakers
capable of communications with a central computer and with digital meters.
Each circuit breaker uses a microprocessor to control its operation. The
network provides a means for convenient control of switching actions of
the circuit breakers. Additionally, the network supplies information
concerning each main feeder circuit, and each branch circuit for which
information is desired, to the central computer. The information supplied
about each circuit may include, current and voltage in each phase of a
multiple phase distribution system, electric power, vars, phase angle,
trip settings of the circuit breaker, current reached during trip events,
the number of trip events, and historical records of trip events, etc. Any
information which can be sensed through current sensors or voltage sensors
and then calculated from the quantities sensed may be supplied to the
central computer. The invention uses both circuit breakers and metering
units to sense the required information and to transmit the information to
the central computer.
Additional objects of the invention are as set out hereinbelow.
Object No. 1
To provide a switchgear system with computer intelligence capable of
monitoring power circuits and taking actions based upon decisions made by
the computer.
Object No. 2
To provide a circuit breaker and metering unit having serial data
communications in addition to microprocessor operated restraint-in and
restraint-out signals.
Object No. 3
To provide a circuit breaker system having a plurality of circuit breakers,
a plurality of metering units, and a ring communications system for
communications with a central computer.
Object No. 4
To provide a circuit breaker transmitting a serial data stream to a
receiving unit and having pauses between BYTES.
Object No. 5
To provide a circuit breaker system having a metering unit capable of
receiving serial data from a circuit breaker and capable of transmitting
information on a transmission system.
Object No. 6
To provide a circuit breaker having a serial communications data stream to
a receiving unit and including wait states to enhance data reception, and
having more critical data transmitted most often and less critical data
transmitted less often, and having trip data transmitted upon occurrence
of a trip.
Object No. 7
To provide a circuit breaker transmitting a serial data stream to a Remote
Indicator Unit, and the Remote Indicator Unit having solid state latch
memory to preserve information during a power outage.
Object No. 8
To provide a circuit breaker drawing power from current transformers and
having a microprocessor placed in a low power state during loss of power.
Object No. 9
To provide a power down and reset control circuit for a circuit breaker.
Object No. 10
To provide a trip unit with power failure resistant memory for retention of
former trip data.
Object No. 11
To provide a power supply using current transformers for powering a circuit
breaker, and having means for shorting the power supply to ground in order
to prevent overvoltage during high current transients.
Object No. 12
To provide a circuit breaker capable of external testing and having optical
isolation.
Object No. 13
To provide a circuit breaker trip unit selective between motor protection
curves and circuit breaker curves, and a circuit breaker offering phase
unbalance protection.
Object No. 14
To provide a circuit breaker having a trip unit, and an external unit for
applying power to the trip unit to get data out of the trip unit.
Object No. 15
To provide a Circuit breaker having external test using multi-turn resistor
fine adjustment of test parameters.
Object No. 16
To provide a circuit breaker indicator package having a switchable battery
power supply and an oscillator that runs only when needed, for a trip unit
or the like.
Object No. 17
To provide a circuit breaker using microprocessor and having operator
accessible switch controls for trip characteristics and multiplier plug.
Object No. 18
To provide a circuit breaker having a metering unit with a display panel
operating from a menu.
Object No. 19
To provide a digital metering unit having two microprocessors, where a
first processor may sample current and voltage parameters, and a second
processor may handle other functions including communications.
Object No. 20
To provide a circuit breaker having a microprocessor operated Metering Unit
which has a software reset in the event that the microprocessor quits
running.
Object No. 21
To provide a circuit breaker having a remote indicator unit using latching
relays to retain status after trip.
Object No. 22
To provide a circuit breaker having direct trip by a heavy current event,
and microprocessor inhibition of the trip to permit storage of data into
memory.
Object No. 23
To provide a microprocessor controlled circuit breaker capable of
digitizing a plurality of input quantities, and capable of digitizing only
selected ones of the quantities on a cyclical basis.
Object No. 24
To provide a Power Metering Unit using a microprocessor and sampling both
voltage and current during the same time interval using an analog latch.
Other and further aspects of the present invention will become apparent
during the course of the following description and by reference to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings, in which like numerals represent like parts
in the several views:
FIG. 1 is a drawing of a circuit breaker system mounted in an equipment
rack, and including computer intelligence.
FIG. 2 is a close up of a computer operated circuit breaker.
FIG. 3 is a close up drawing of the control panel of a computer operated
circuit breaker Trip Unit.
FIG. 4 is a close up drawing of a Local Management Unit, LMU.
FIG. 5a is a drawing of a programmable controller.
FIG. 5b is a drawing of a system interface unit for a programmable
controller.
FIG. 5c is a schematic for a system interface unit.
FIG. 6 is a drawing of a Display Unit.
FIGS. 7A and 7B comprise a drawing of a Remote Indicator Unit.
FIG. 8 is a schematic of a simple power distribution system.
FIG. 9 is a schematic of a more extensive power distribution system.
FIG. 10 is a partial schematic of a power distribution system.
FIG. 11 is a diagram of a power management system having Local Management
Units connected in an optical fiber communications system.
FIG. 12 is a connection diagram for a Trip Unit and a Local Management Unit
and having communications between the Trip Unit and a the Local Management
Unit, and between a plurality of Local Management Units.
FIG. 13 is a connection diagram for a Trip Unit having communications to a
Display Unit.
FIG. 14 is a partial schematic of a connection of a Trip Unit to a power
distribution system.
FIG. 15-1 A and B is a schematic of a Trip Unit.
FIG. 15-2 A and B is a schematic of a Trip Unit.
FIG. 15-3 A and B is a schematic of a Trip Unit.
FIG. 15-4 A and B is a schematic of a Trip Unit.
FIG. 16 is a timing diagram of a Trip Unit.
FIG. 17 is a flow diagram for software of a trip unit.
FIG. 18A is part of a flow chart for Trip Unit software.
FIG. 18B is part of a flow chart for a Trip Unit software.
FIG. 18C is part of a flow chart for Trip Unit software.
FIG. 19 is part of a flow chart for Trip Unit software.
FIG. 20 A and B is a schematic of a Display Unit.
FIG. 21 is a block diagram of a menu program for a Display Unit.
FIG. 22 is a schematic of a Remote Indicator Unit.
FIG. 23 is a block diagram of a Local Management Unit.
FIG. 24 is a block diagram of a Local Management Unit.
FIG. 25-1 is a schematic of a Local Management Unit.
FIG. 25-2 is a schematic of a Local Management Unit.
FIG. 25-3 A and B is a schematic of a Local Management Unit.
FIG. 25-4 is a schematic of a Local Management Unit.
FIG. 25-5 is a schematic of a Local Management Unit.
FIG. 25-6 is a schematic of a Local Management Unit.
FIG. 25-7 is a schematic of a Local Management Unit.
FIG. 25-8 is a schematic of a Local Management Unit.
FIG. 25-9 is a schematic of a Local Management Unit.
FIG. 25-10 is a schematic of a Local Management Unit.
FIG. 25-11 A and B is a schematic of a Local Management Unit.
FIG. 25-12 is a schematic of a Local Management Unit.
FIG. 25-13 is a schematic of a Local Management Unit.
FIG. 26 A through G are bus timing diagrams for a Local Management Unit.
FIG. 27A, 27B, 27C, 27D, is a memory map for a Local Management Unit and a
System Interface Unit.
FIG. 28 is a drawing of a Local Management Unit control panel and display
panel.
FIG. 29 is a diagram of a menu for an LMU.
FIG. 30 is a diagram of a menu for an LMU.
FIG. 31 is a diagram of a menu for an LMU.
FIG. 32 is a diagram of a menu for an LMU.
FIG. 33 is a diagram of an option tree for an LMU display.
FIG. 34 is a block diagram of software for an LMU.
FIG. 35 is a schematic for a System Interface Unit, SIU.
DETAILED DESCRIPTION
Overview
FIG. 1 shows a circuit breaker equipment rack 100 having a system of
microprocessor controlled circuit breakers mounted therein. A variety of
circuit breaker types may be controlled by programmable controller 101,
including an iron frame circuit breaker 102, a molded case circuit breaker
104, and a toggle operated molded case circuit breaker 105. A Local
Management Unit 106 is mounted on the door of the compartments having a
circuit breaker. Each Local Management Unit has a control panel 107. Each
circuit breaker transmits data on a serial communications link to its
Local Management Unit. The Local Management Units have two way serial
communications with the programmable controller 101. Meter panel 108 may
display measured quantities such as voltage, current, power, phase angle,
or kilowatt hours.
FIG. 2 is a detailed view of the front of a microprocessor controlled
circuit breaker. The circuit board for the Trip Unit (TU) is visible
through the panel opening. Various switches visible through the panel
opening are used to control settings of the Trip Unit, such as the long
time ampere rating and delay time, the short time ampere pickup rating and
delay time, the instantaneous ampere pickup rating, and the ground fault
ampere pickup rating and delay time The actual amperes at which functions
occur is determined, additionally, by the choice of current transformers
and by the choice of a rating plug for the unit. A control panel is shown
for the Trip Unit in a projection from its place of mounting. Connection
jacks for connecting external equipment to the Trip Unit circuit board are
shown. The external equipment may be a Local Management Unit (LMU), a
Display Unit (DU), or a Remote Indicator Unit (RIU).
FIG. 3 is a detailed view of the Trip Unit control panel. The status of the
Trip Unit may be read from the Trip Unit control panel display device.
A table gives the values of current in amperes selected by the various
positions of the front panel switches for different sensor current
transformers.
FIG. 4 shows a control panel 107 for a Local Management Unit (LMU) 106,
mounted on the door of the enclosure for the circuit breaker. The LMU
receives data via a serial communication link from the Trip Unit. The
Local Management Unit is a microprocessor controlled apparatus for
performing several functions, including measurement of electrical current
and electrical power at sufficient accuracy for metering purposes,
displaying Trip Unit data, displaying LMU data, and for communicating
through a ring optical fiber link to a programmable controller, through a
System Interface Unit
(SIU) along with up to, for example, 64 other Local Management Units, in
order to provide an intelligent electrical energy management system.
FIG. 5 shows a programmable controller 101. One of the modules in the
programmable controller may be a Systems Interface Unit (SIU). The SIU is
the transmitter and receiver for the ring type optical fiber communication
system, and the SIU may communicate with up to 64 Local Management Units.
FIG. 6 shows a Display Unit (DU). The Display Unit provides a remote
display of functions of the Trip Unit. The Display Unit is an optional
feature used when the sophistication of a Local Management Unit is not
needed. A Display Unit may mount, for example, on the door of the circuit
breaker enclosure, as is shown for the Local Management Unit in FIG. 1.
The Display Unit receives data via the serial communications link from the
TU.
FIGS. 7A and 7B illustrate front and bottom views of a Remote Indicator
Unit. A Remote Indicator Unit provides contact closures to indicate
selected states of the Trip Unit. The Remote Indicator Unit is an optional
feature which can be used independently with a Trip Unit or in conjunction
with either a Local Management Unit or a Display Unit. The contact
closures of the relay may be used for remote signaling of the status of
the Trip Unit. The Remote Indicator Unit receives data via the serial
communications link from the TU.
FIG. 8 is a schematic diagram of a typical three-phase AC power
distribution system. A main circuit breaker utilizes a Trip Unit and a
Local Management Unit. A feeder bus supplied by the main circuit breaker
feeds branch circuits, each of which is protected by a Trip Unit. As
shown, some of the Trip Units have a Display Unit connected and the
remaining TU do not. The arrangement shown in FIG. 8 does not permit
communications on a serial communications link between the various Trip
Units. However, the Trip Units communicate directly by a "restraint-in and
restraint-out" system.
Restraint-In, Restraint-Out
The restraint-in and restraint-out system is indicated by the dashed line.
Each Trip Unit contains its own microprocessor, and the restraint-in and
restraint-out system operates by logic level signals provided by the
microprocessor. The purpose of the restraint-in restraint-out connection
is for a branch circuit breaker to communicate to a main circuit breaker
that a fault is occurring in its branch, and commands the main circuit
breaker to utilize a higher current and longer time delay "look up table"
in its trip routine. The higher current and longer time delay "look up
table" of the main breaker permits the branch breaker to trip first,
thereby isolating a power loss to that branch, and avoiding the loss of
power to the other branches by a premature trip of the main circuit
breaker.
The restraint-in and restraint-out system is a level communications system
in addition to communications between circuit breakers through the Trip
Unit Serial Communications Link to the LMU, and communication of various
LMU Units to a System Interface Unit, SIU. A Trip Unit may be arranged to
communicate with another Trip Unit so that the process of occurrence of a
trip at the first Trip Unit changes the settings for the occurrence of a
trip at a second Trip Unit. For example, if a first Trip Unit monitors a
bus supply system and other Trip Units monitor loads deriving their source
of electrical energy from the aforementioned bus, then it is desirable to
have the downstream Trip Unit trip out first in the event of a fault on
its load. The Restraint In, Restraint Out signals connected between a
downstream circuit breaker and an upstream circuit breaker cause the
downstream circuit breaker to signal the upstream circuit breaker that a
fault is occurring in the load of the downstream circuit breaker. Receipt
of this signal by the upstream circuit breaker causes the upstream circuit
breaker to utilize different settings for developing a trip. The different
settings cause the upstream circuit breaker to delay its trip until the
downstream circuit breaker has had a chance to isolate the fault. The
Restraint In, Restraint Out signaling arrangement prevents the occurrence
of a fault on one branch circuit from causing an upstream circuit breaker
to trip thereby removing power from other branch circuits in which no
fault is occurring.
Some of the branch circuits shown in FIG. 8 are protected by a Trip Unit
only. A Trip Unit without a Display Unit, a Local Management Unit, or a
Remote Indicator Unit does not have communications capability. However,
the status of the Trip Unit may be read from the Trip Unit control panel
as shown in FIG. 3.
FIG. 9 shows a more complex electrical energy distribution system. Two main
three-phase AC power lines are capable of feeding a number of branch
circuits. Each AC power line is protected by a main circuit breaker. Each
main circuit breaker is controlled by a Trip Unit and a Local Management
Unit. Restraint-in and restraint-out communications between the branch
circuit breakers and the main circuit breaker are available, but is not
shown in FIG. 9 for the sake of clarity.
A power "link" is protected by a Trip Unit and a Display Unit.
Alternatively, a Local Management Unit could be used with the link Trip
Unit.
Branch circuits which are judged to be "critical" are protected by both a
Trip Unit and a Local Management Unit. All Local Management Units are
connected in an optical fiber ring communication system to a system
interface unit (SIU). The SIU is a board plugged into a programmable
controller. The SIU is mounted within the programmable controller as a
receiver and transmitter for the optical fiber ring communications link.
Various branch circuits may be protected by additional Trip Units in
combination with a Local Management Unit, or by Trip Units in combination
with a Display Unit, or by Trip Units with a Remote Indicator Unit, or by
Trip Units standing alone.
Also shown in FIG. 9 is a connection between the programmable controller
and an optional host computer. The communications connection between the
programmable controller and the host computer may be by a standardized
Manufacturing Automation Protocol, MAP link, or alternatively by any
convenient data connection.
SYSTEM CONNECTIONS
Single Trio Unit and Local Management Unit
FIG. 10 shows the connection of a Trip Unit (TU) and a Local Management
Unit (LMU). An AC power source supplies three phase electrical energy to
conductors A, B, C. Conductors A, B, C supply energy to the load. Current
transformers CTA, CTB, and CTC provide signals to the Trip Unit
proportional to current flow in their respective conductors. Contacts CA,
CB, and CC interrupt current flow in their respective conductors when the
trip coil is energized by the Trip Unit. The trip coil is energized by the
Trip Unit whenever current flow in conductors A, B, C exceeds
predetermined values. For example, if a short circuit develops in the
load, the Trip Unit will energize the trip coil and open contacts CA, CB,
CC. Also, if a ground fault occurs in the load the Trip Unit will open
contacts CA, CB, CC in order to isolate the fault.
The Local Management Unit, LMU, has input signals from precision current
transformers PCTA, PCTB, PCTC, from their respective phases A, B, C. Also,
potential connections PA, PB, PC connect to the LMU. The LMU measures
current flow, power, reactive power, and phase factor in conductors A, B,
C. The LMU measures these quantities to an accuracy necessary for metering
purposes as, for example, 1% A read out of the various quantities measured
and computed by the LMU may be observed by an operator at the read out
block.
The Trip Unit communicates with the Local Management Unit through the Trip
Unit Serial Communications Link, an electrical communications link. The
Trip Unit transmits, on a predetermined protocol, information including
the following: fault conditions including phase and balance pickup or
trip, ground fault pickup or trip, short time pickup or trip, long time
pickup or trip, 90% of long time pickup, instantaneous pickup or trip, if
a trip is occurring, a ground fault pickup condition, a short time pickup
condition, a long time pickup condition, an instantaneous pickup
condition, whether a self-test trip occurred, current levels in phase A,
phase B, and phase C, ground fault current, the option of trip unit or
motor protection unit for which the trip unit is set, sensor and plug
identifiers, positions of selector switches for long-time delay, long-time
pickup, short time delay, short time pickup, ground fault delay, ground
fault pickup, instantaneous pickup, phase and balance percent switch,
long-time trip memory, the cause of the last trip, the current at the last
trip, and other pertinent circuit breaker data. A 31 BYTE stream is
cyclically transmitted. The individual bits of each BYTE are discussed
hereinbelow.
Operating power for the Trip Unit is supplied by current derived from the
current transformer CTA, CTB, CTC. Power for operation of the Local
Management Unit, LMU, is supplied by an external power source.
The information communicated from the Trip Unit to the Local Management
Unit may be observed by an operator at the readout of the Local Management
Unit.
Alternatively, the serial communications port may communicate on a linear
bus, and alternatively, may use RS232, RS422 or other standard
communications method.
The Local Management Unit has a serial communications port for
communicating on a ring optical link, along with up to 64 other Local
Management Units, to a programmable controller or other computer.
LMU Optical Ring Communications System
FIG. 11 shows a drawing of individual Trip Units, TU, and Local Management
Units, LMU, connected in an optical communications ring. Each individual
Trip Unit measures current flow to its individual load. Each Trip Unit has
its own Local Management Unit for measuring power flow. The Trip Unit
communicates to its Local Management Unit on the Trip Unit electrical
serial communications link.
The various Local Management Units communicate with a System Interface Unit
utilizing an optical ring serial communications system, or alternatively
on a linear bus, or may use RS232, RS422 or other standard communications
method. Up to 64 Local Management Units can communicate with a single SIU.
Each LMU communicates with the System Interface Unit according to a polling
protocol. The SIU/LMU communications protocol is described hereinbelow.
The information communicated by an LMU to the System Interface Unit may
include all of the information transmitted from the Trip Unit to the LMU,
and also may include all of the information developed by the LMU in its
measurement function.
SIU-System Interface Unit
The System Interface Unit may be a module mounted within a programmable
controller. For example, the Sy/Max brand of programmable controller sold
by the Square D Company may satisfactorily serve as the programmable
controller. The SIU module may fit into a slot in a register rack of the
programmable controller. The programmable controller normally receives
information along a data highway connecting the SIU and the programmable
controller. Also, the programmable controller may control the SIU and
direct it to poll a particular Local Management Unit, LMU.
Central Computer
Output from the programmable controller may be transmitted along a data
highway to a central computer. The central computer may utilize inputs
from the SIU along with inputs from various other sensors in order to
control processes in a manufacturing plant.
System Connection Diagram
FIG. 12 is a System Connection Diagram. An alternating current bus is shown
in the upper left corner of FIG. 12, and includes conductors for phase A,
phase B, phase C and the neutral line. Main current transformers for
circuit breaker #1 are shown schematically, and are connected to Trip Unit
#1 at connection TB3. Conductors passing through circuit breaker #1 main
current transformer, conductors A, B, C, N, connect to contacts operated
by the trip solenoid. Energization of the trip solenoid by Trip Unit #1
opens the contacts.
Conductors A, B, C, N connect from the downstream side of the contact to
breaker #1 precision current transformer, and continue on to the breaker
#1 load. The breaker #1 precision current transformers connect at
connection TB5 to Local Management Unit LMU #1. A serial communication
link from Trip Unit #1 is connected to Local Management Unit LMU #1 at
jack J5 of Trip Unit #1 and plug P5 of Local Management Unit LMU #1. Trip
Unit #1 has a rating plug connected at jack J6. A Testing and Calibration
Unit may be connected to Trip 10 Unit #1 at jack J4. Step up current
transformers connect into Trip Unit #1 at connection TB4, and accept
current at connection TB3 from breaker #1 main current transformers.
Local Management Unit LMU #1 is connected to control
r at connection TB #6. Local Management Unit LMU unit #1 is in a fiber
optical ring type "daisy chain" serial data communication ring. Other LMU
units in the communications ring are indicated, and unit #N is shown.
There may be up to 64 LMU units connected in the optical ring "daisy
chain". A System Interface Unit, SIU, is shown connected in the optical
ring. The SIU connects to a programmable controller. Data transmitted to
the System Interface Unit from each of the Trip Units and the Local
Management Units may be transferred to the programmable controller. Also,
the programmable controller may command the SIU to poll a particular LMU.
Alternative Embodiment for Trip Unit
FIG. 13 shows an alternative embodiment of a Trip Unit. The alternative
embodiment does not utilize a Local Management Unit, LMU. The alternative
embodiment is a stand-alone circuit breaker utilizing a Trip Unit and a
display unit. Rather than connecting an LMU to the TU at jack J5, a
Display Unit is connected to the TU at jack J5. Also, a Remote Indicator
Unit (RIU) is shown connected to the TU at connection TB4. The RIU is
capable of operating a contact in order to signal a long time pick-up or
dry trip condition of the Trip Unit.
The Display Unit accepts the serial communications data stream output by
the TU, just as the LMU accepts the serial data stream, and may display
the data at a location remote from the Trip Unit. Internal operation of
the Display Unit and the RIU will be described hereinbelow.
Trip Unit I/O Connections
FIG. 14 shows connections between a Trip Unit and a 3 phase AC line.
Conductors A, B, C, and Neutral, are shown at the left of FIG. 14 in the
connection between a switch gear bus and a load. Current flow in
conductors A, B, C may be interrupted by opening of the contacts. The trip
solenoid, when energized, opens the contacts.
Main current transformer CTA, CTB, CTC, and CTN are shown. Current
transformer CTN develops a voltage proportional to the current flow in the
neutral line. The main current transformers are connected to current
transformers SUA, SUB, SUC, and SUM. Transformers SUA, SUB, and SUC have
turns ratio of, for example, 1 to 10. The SUM current transformer has a
turns ratio of, for example | | |
