Note: Descriptions are shown in the official language in which they were submitted.
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1 BRANCH CIRCUIT MONITOR
2
3 CROSS-REFERENCE TO RELATED APPLICATIONS
4 [0001] This application claims the benefit of United States non-
provisional patent
application number 13/962,937 entitled "Branch Circuit Monitor" filed by
Montgomery J. Sykora
6 et at. on August 8, 2013, United States provisional application no.
61/681,406 entitled
7 "Apparatus, System and Method for Branch Circuit Monitoring" filed by
Montgomery J. Sykora
8 on August 9, 2012 and United States provisional application no.
61/681,527 entitled "Apparatus,
9 System and Method for Branch Circuit and HVAC Monitoring and Control for
Optimal Cooling
and Energy Efficiency" also filed by Montgomery J. Sykora et al. on August 9,
2012, each of the
11 three applications are hereby incorporated by reference as though fully
set forth herein.
12
13 BACKGROUND
14 Field
[0002] Aspects of the present disclosure involve a branch circuit
monitoring system
16 providing information concerning the utilization of individual branch
circuits, particularly within a
17 data center, and providing the ability to manage those circuits so that
individual circuits are not
18 overloaded while at the same time fully utilizing various circuits.
19
Background
21 [0003] Branch circuit monitoring (BCM) devices typically utilize a
multitude of current
22 transformers (CTs) connected to a sampling and processing board, either
directly or via an
23 intermediary circuit board. The CTs generate a voltage or current
electric signal that is
24 proportional to the current flowing in the branch circuit. The standard
procedure dictates a
sampling of the electric signal and performing mathematical calculations to
determine the RMS
26 current. Additional calculations such as real power, apparent power,
power factor, and kWh are
27 possible with the estimation or measurement of the voltage of the branch
circuit. However,
28 because the circuits are limited by the circuit breaker current rating,
the most important and
29 useful measurement is the RMS current value. This value is used to
determine if a circuit is in
danger of being overloaded, or can be summed with other current values to give
a phase
31 current total. Some BCM devices use digital signal processors and a
multitude of analog-to-
32 digital (ND) converters to accomplish this. As the number of circuits
monitored grows, the size
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I and complexity of the collection and processing circuitry increases,
leading to large systems and
2 relatively high prices per panel. A typical data center may have hundreds
of panels and
3 thousands of circuits to monitor, making conventional BCM devices
prohibitively expensive to
4 install.
[0004] Typical BCM devices require that the circuit panel be de-energized
to pass the
6 circuit wires through the CTs, making retrofits difficult in data centers
that need continuous
7 operation (or up-time). Use of split-core CTs alleviates some of the
difficulty of installing a BCM
8 in a "live" panel, but in general, the main processing circuitry still
has the disadvantage of being
9 large and requiring a separate cabinet and power supply for installation.
These two
requirements increase the cost and complexity of the BCM device installation.
11 [0005] In addition, most prior art BCM devices are designed with
application-specific
12 processors and circuitry. This makes upgrading or improving the system
difficult and expensive,
13 if even possible.
14
BRIEF SUMMARY
16 [0006] In accordance with one embodiment a branch circuit monitoring
(BCM) device
17 comprises a programmable panel processor, a plurality of small, modular
collection devices,
18 and a plurality of non-contact current sensors.
19 [0007] Accordingly several disadvantages described above can be
alleviated or mitigated
by the apparatus, system and methods described herein along with additional
desirable
21 features.
22 [0008] An improved branch circuit monitoring device, system and
methods are described
23 herein. The device, system and methods overcome the major issues with
current BCM devices
24 and systems: high cost, installation complexity, and obsolescence. These
factors are
interrelated and are addressed by multiple approaches and methods. Together,
the features
26 and improvements presented make branch circuit current monitoring
affordable and feasible for
27 existing data centers.
28 [0009] The complexity of the BCM device is reduced while
simultaneously decreasing the
29 size and footprint of the apparatus to allow a low-cost system to be
installed easily inside a
standard panel board without external enclosures or a dedicated power supply.
The use of
31 accurate RMS-to-DC voltage converter circuitry on small, decentralized
collection boards allows
32 for relatively inexpensive general purpose processor to be utilized for
the data aggregation and
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1 processing while maintaining highly accurate current values. Finally,
standard networking
2 protocols such as TCP, HTTP, UDP, as well as any specific protocols such
as BACnetTM,
3 Modbue, or SNMP are supported. The system supports long-term data
storage, retrieval, and
4 visualization using modern, open-source programs and methods and the
ability to integrate
numerous BCM devices into a system.
6 [0010] In one implementation, a branch circuit monitoring system
is provided comprising: a
7 first plurality of current sensors each coupled with at least one branch
circuit of a first plurality of
8 branch circuits, each respective current sensors of the first plurality
of current sensors
9 configured to measure a current within one of the respective first
plurality of branch circuits and
to provide a signal indicative of the measured current value; a first
collection device configured
11 to receive the signals indicative of the measured current value from
each of the first plurality of
12 current sensors, multiplex the signals indicative of the measured
current value from each of the
13 first plurality of current sensors, and convert the signals indicative
of the measured current value
14 from each of the first plurality of current sensors from a first
alternating current (AC) signal to a
first direct current (DC) signal; a second plurality of current sensors each
coupled with at least
16 one branch circuit of a second plurality of branch circuits, each
respective current sensor of the
17 second plurality of current sensors configured to measure a current
within one of the respective
18 second plurality of branch circuits and to provide a signal indicative
of the measured current
19 value; a second collection device configured to receive the signals
indicative of the measured
current value from each of the second plurality of current sensors, multiplex
the signals
21 indicative of the measured current value from each of the second
plurality of current sensors,
22 and convert the signals indicative of the measured current value from
each of the second
23 plurality of current sensors from a second alternating current (AC)
signal to a second direct
24 current (DC) signal; and a panel processor in communication with the
first and second collection
devices configured to receive the first and second plurality of DC signals,
the panel processor
26 configured to store in a local memory a plurality of data structures
comprising the measured
27 branch circuit current data values for said branch circuit along with a
timestamp associated with
28 a time at which the currents were measured.
29 [0011] In another implementation, a method of monitoring branch
circuits is provided
comprising: measuring a first plurality of currents within a first plurality
of branch circuits using a
31 first plurality of current sensors each coupled with a respective branch
of the first plurality of
32 branch circuits; receiving, at a first collection device, a first
plurality of signals indicative of the
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1 first plurality of measured current values of the first plurality of
branch circuits; multiplexing, at
2 the first collection device, the first plurality of signals indicative of
the first plurality of measured
3 current values; converting, at the first collection device, the signals
indicative of the measured
4 current value from each of the first plurality of current sensors from a
first alternating current
(AC) signal to a first direct current (DC) signal; measuring a second
plurality of currents within a
6 second plurality of branch circuits using a second plurality of current
sensors each coupled with
7 a respective branch of the second plurality of branch circuits;
receiving, at a second collection
8 device, a second plurality of signals indicative of the second plurality
of measured current
9 values of the second plurality of branch circuits; multiplexing, at the
second collection device,
the second plurality of signals indicative of the second plurality of measured
current values;
11 converting, at the second collection device, the signals indicative of
the measured current value
12 from each of the second plurality of current sensors from a second
alternating current (AC)
13 signal to a second direct current (DC) signal; receiving, at a panel
processor in communication
14 with the first and second collection devices, the first and second
plurality of DC signals; and
storing, in a local memory of the panel processor, a plurality of data
structures comprising the
16 measured branch circuit current data values for said branch circuit
along with a timestamp
17 associated with a time at which the currents were measured.
18 [0012] The foregoing and other aspects, features, details, utilities,
and advantages of the
19 present invention will be apparent from reading the following
description and claims, and from
reviewing the accompanying drawings.
21
22 BRIEF DESCRIPTION OF THE DRAWINGS
23 [0013] Figure 1 shows an example implementation of a branch circuit
monitoring system.
24 [0014] Figure 2 shows an example implementation of a collection
device that may be used
within a branch circuit monitoring system such as shown in Figure 1.
26 [0015] Figure 3 shows example implementation of a panel processor
coupled to a plurality
27 of collection devices.
28 [0016] Figure 4 is a view of an example BCM device installed in a
circuit panel board.
29 [0017] Figure 5A shows an example collection device circuit board,
also known as a CT
interface (CTIF) board.
31 [0018] Figure 5B shows a simplified schematic of an example analog
processing chain on
32 the CTIF board.
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1 [0019] Figure 6 shows the BCM device from software and networking
perspectives.
2 [0020] Figure 7 shows the BCM System (BCMS) block diagram.
3 [0021] Figure 8 shows the alternate embodiment of the CTIF board
with Hall Effect
4 sensors.
[0022] Figure 9A depicts a calibration setup.
6 [0023] Figure 9B gives an example algorithm flowchart to
accomplish the calibration for a
7 sensor.
8
9 DETAILED DESCRIPTION
[0024] Modern data centers host a tremendous number of computing devices,
such as web
11 servers and the data storage systems necessary for enterprise software
operations, cloud
12 computing, Internet access and applications, and numerous other
computing functions. The
13 power for the physical equipment within the data center is supplied by
branch circuits. So, for
14 example, a rack of servers that are used to host a website may be
supplied by a single 20 Amp
rated branch circuit. These branch circuits, as illustrated in Figure 1,
originate from a power
16 panel where the source of power is received, which may be a 120 volt,
208 volt or other
17 alternating current (AC) supply, and which may be two or three phase.
The power supplied to
18 the panel is then distributed across some number of discrete branch
circuits. Conventional
19 panels may include 42 or 72 branch circuits with each circuit also
including a breaker.
[0025] Figure 1 shows one example implementation of a branch circuit
monitoring device
21 10. A branch circuit monitor 10 is a device that enables the monitoring
of individual branch
22 circuits 12 of an electrical panel 14. Atypical panel contains 42 or 72
branch circuits, although
23 other panel configurations are possible. These circuits are then routed
to equipment or
24 equipment racks where individual computers, networking devices, or
similar components draw
power from one or more circuits. The monitoring of the branch circuit current
values can be
26 used, for example, to trigger alarms, both locally and remotely, as well
as be archived in a
27 database for retrieval and analysis.
28 [0026] In one example, the branch current monitor 10 is configured
to measure and log the
29 branch current of a plurality of branches spanning the power panels of
the data center. One or
more current sensors 16 are used to monitor the current of each branch circuit
12. In some
31 cases, more than one current sensor 16 may be deployed across various
sub-branches of a
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1 branch circuit 12. The sub-branch currents may later be summed, such as
by a management
2 board, to determine a total branch current.
3 [0027] In one implementation, each of the current sensors 16 (e.g.,
current transformers
4 (CTs)) connects to a collection device 18 (e.g., a current measurement
board or other collection
device) located in the power panel 14. The current sensors 16 provide the
collection device 18
6 with a signal indicative of the branch circuit current. The collection
device 18 uses the signal
7 from the current sensor 16 to produce a voltage (or other signal)
indicative of the measured
8 current that can be understood by a panel processor 20. The panel
processor 20 receives each
9 voltage signal (or other type of signal), calculates a current, and
stores the current
measurement along with a timestamp and address in a memory 22. This
information may be
11 later relayed to a server, such as the Data Center BCM Server 24 shown
in Figure 1, for longer
12 term storage in a database, such as BCM Database 26 shown in Figure 1.
The server 24 may
13 periodically report measurements to a building management system (BMS)
28 and/or to a user.
14 Users may also alter the configuration of the branch current monitor 10
by accessing the server
24. A user interface 30, such as a display with a graphical user interface
(GUI), may be used to
16 report data or other information to a user.
17 [0028] Figure 2 shows an example implementation of a collection
device 40 (in this
18 implementation, a current measurement board although other collection
devices are
19 contemplated) that may be used within a branch circuit monitoring
system, such as the branch
circuit monitor 10 shown in Figure 1. In this particular implementation, the
collection device may
21 utilize any method form measuring current and provide the current
measurement to a panel
22 processor 50 (shown in Figure 3). As shown in Figure 2, the collection
device 40 may include a
23 rectifier/signal conditioning element 42, an analog-to-digital (AID)
converter 44, and an output
24 connection 46. Together these elements may be configured to convert the
signal captured by
the current sensor 48, such as a CT, into a signal that is usable by the panel
processor 50. For
26 example, the rectifier/signal conditioning element 42 may comprise a
resistor coupled to a
27 voltage rectifier to convert the AC resistor voltage to an equivalent
direct current (DC) voltage.
28 The resistor may be connected to the terminals of the current sensor 38
(e.g., CT). When
29 branch circuit current is nonzero, a current will flow through the
resistor creating a measurable
voltage drop. If the branch circuit has an AC voltage, the resistor voltage
will likewise be an AC
31 voltage. In many cases, it may be beneficial to convert the AC resistor
voltage to an equivalent
32 DC voltage using the rectifier of the rectifier/signal conditioning
element 42. This element may
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1 also comprise a signal conditioner configured to prepare the signal for
use by the ND converter
2 44. The signal may be amplified (or scaled down) to be in an operable
range of the ND
3 converter 44 and may also be filtered to remove excess noise. For
example, the AID converter
4 44 may be configured to accept a DC input and the rectifier may only
provide a 0 to 1V output.
In this case, it may be beneficial to amplify the output of the rectifier in
the signal conditioner 42
6 to produce an output signal. The rectified and conditioned signal is then
communicated to the
7 ND converter 44 which then converts the signals from each current sensor
48 into digital values
8 and produces an output for transmission to the panel processor 50. The ND
converter 44
9 interfaces with a connection element 46, such as a standard RJ45
connection or any other
suitable electrical connection. In one example, the connection element 46 may
also be
11 configured to receive DC power from the panel processor 50.
12 [0029] In one specific implementation, each collection device is
connected with or
13 otherwise configured to receive an input from N current sensors 48
(e.g., 1 to 8 current
14 sensors). Depending on the implementation, however, any number of
current sensors may be
connected with to a collection device. Likewise, each power panel may have a
single collection
16 device or a plurality of collection devices depending on the number of
branch circuits and the
17 implementation of the collection devices.
18 [0030] Figure 3 shows an example implementation of a panel
processor 50 coupled to a
19 plurality of individual collection devices 40, such as the collection
device 40 shown in Figure 2.
In one example, the panel processor 50 may comprise an input circuit 52, a
processor 54, a
21 data storage element such as a memory 56, and a network connection 58.
The processor 54 is
22 configured to perform current calculations by executing instructions
stored in the memory 56.
23 The memory 56 may also store any needed constant values for current
calculations. Once each
24 current calculation is completed, the processor 54 may store the results
in the memory 56 along
with an address associated with the result, and a timestamp. The network
connection 58 may
26 then be used to send the current measurement(s), the address(es), and a
timestamp(s) to a
27 server 60 at regular intervals, irregular intervals, or based on a
command from the server 60.
28 Furthermore, the panel processor 50 may receive configuration data from
the user via the
29 server 60.
[0031] A branch circuit monitoring server 60 is coupled with each panel
processor within a
31 data center. Since there may be hundreds of panels in a data center,
there may in turn be
32 hundreds of panel processors obtaining and recording data from thousands
of branch circuits.
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1 The server 60 is connected with a database (see, e.g., Figure 1) and is
configured to request
2 data from the processors 54 of the panel processors 50 and store the
collected data in the
3 database (or other form of data storage). Like the processor 54, the
database may include the
4 branch ID, the current value and the time stamp. Once the data is
collected from the
processors 54 of the panel processors 50, the memory 56 at the panel
processors 50 may be
6 cleared thereby allowing the memory size at the panel processors 50 to be
relatively small.
7 Similarly, the collection device may have only sufficient memory to store
only the most recent
8 measurements or some number of measurements that would occur between
polling cycles of
9 the panel processor to the collection device.
[0032] The server 60, panel processors 50 and collection devices 40 are
arranged in a
11 programmable modular system. Thus, the system may be deployed in any
data center with any
12 number of branch circuits; the system easily adapts to the addition or
removal of circuits, and
13 does not require extensive customization for deployment. Moreover, the
server 60 and panel
14 processors 50 may be configured for self-discovery of new collection
devices, circuits, etc., so
that user programming or configuration of the system is minimized or even
eliminated. A
16 building management system may be configured to receive and display the
measured
17 parameters. In one example, the building management system is connected
to the server by
18 way of a Modbus TCP connection, although other forms of standard or
proprietary
19 communications protocols are possible.
[0033] Besides the ability to view the data, the system also provides the
data center or the
21 purchasers of a circuit to manage the circuit usage. In one example, the
data center may utilize
22 the full capacity of a given circuit or set of circuits before
installing additional panels and circuits.
23 If, for example, a 20 amp circuit is a supplying at most 10 amps, then
there are approximately 8
24 amps of underutilized capacity on that circuit (considering that it is
typical practice to not fully
load the circuit in order to avoid tripping the breaker). Across several
panels there may
26 additional underutilized capacity. Thus, the circuits may be rearranged
or additional equipment
27 coupled with the circuit rather than adding additional panels.
Similarly, if a circuit is running over
28 its maximum rated capacity, say consistently at or near 20 amps, then
some load can be
29 removed from the circuit and thereby avoid down time for the equipment
coupled with the circuit
when the breaker trips. The BMS module within the BMS system may be further
configured to
31 automatically notify the user when such conditions occur.
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1 [0034] In this implementation, the panel processor 50 is connected
with and configured to
2 collect data, such as via polling or interrupt, from the collection
devices 40 (e.g., a plurality of
3 individual current measurement boards). In one specific implementation,
for example, each of
4 the collection devices 40 is connected with the panel processor 50 by way
of a twisted pair
parallel connection, although other forms of communication and connection are
possible, such
6 as I2C, SP1, or USB. As discussed above, the panel processor 50 includes
an input 52 for
7 receiving the data from the collection devices 40, a processor 54, and a
storage device, such as
8 some form of memory 56, where the data is stored at the panel processor
50. In one example,
9 the processor 54 stores an indication of the branch where a particular
measurement was taken
(e.g., a branch ID), the measured current, and a time stamp.
11 [0035] In one implementation, each collection device is connected
with or otherwise
12 configured to receive input from eight current sensors. Depending on the
implementation,
13 however, any number of branch circuits may be connected with a
collection device. In one
14 implementation, the collection device is configured to poll each branch
circuit monitor once per
second or at some other interval or in response to a command, and may further
be configured to
16 store the measured current with association to the branch circuit where
the measurement was
17 taken as well as the time.
18 [0036] The panel processor 50 receives the measurements from each
of the current
19 sensors via the collection devices 40. Thus the panel processor 50
receives one or more DC
voltage inputs from each collection device 40. In this implementation, the
panel processor 50 is
21 adapted to receive a very large number of signals as the system is
expanded to cover more and
22 more branch circuits. For example, the panel processor 50 may have one
input for every current
23 sensor. To handle these inputs, the panel processor 50 may employ an
input circuit 52
24 comprising multiplexers and logic circuitry as needed. Furthermore,
additional panel
processors 50 may be added once a panel processor 50 has run out of inputs.
26 [0037] Once receiving the current measurements, the panel
processor 50 may then convert
27 the voltage measurements into current readings constantly, according to
a schedule, or
28 according to a user command. Using the example provided above, the panel
processor 50 may
29 constantly receive a 0 to 5 VDC signal representing a voltage drop
across a resistor. The panel
processor 50 may then solve for the branch current by determining the resistor
current (using
31 Ohm's law and accounting for any gain produced by the output circuit)
and compensating for the
32 turns ratio of the CT.
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1 [0038] One particular implementation of a BCM device 100 is
illustrated in Figure 4. In this
2 particular implementation, the BCM device 100 comprises a panel processor
101, one or more
3 collection devices 102 (e.g., current measurement or collection circuit
boards), and one or more
4 current sensors 103 (e.g., current transformers (CTs)) per collection
device. The panel
processor 101 may comprise any known processor, such as a general purpose
processor, a
6 special purpose processor, an ASIC, a digital signal processor (DSP) or
the like. In the
7 particular implementation of Figure 3, for example, the panel processor
comprises an ARM
8 Cortex-8 processor using a Linux operating system with an easily
modifiable programming
9 language to ensure upgrades, patches, and additional features are as
simple as upgrading a
standard PC computer. In an alternate implementation, other processors and
operating
11 systems such as an Intel Atom processor using Windows 8 RT can be used.
In one
12 implementation, the BCM device uses split-core CT current sensors on
each circuit to allow for
13 easy installation of "live" panels without the need to de-energize.
14 [0039] Implementations of the BCM device may also use solid core
CTs, or other current
sensors such as Hall Effect sensors, or Rogowski coils. In one particular
implementation, the
16 panel processor, collection boards, and current sensors are small
modular devices that are
17 adapted to be installed inside of the panel enclosure. In this
implementation, the collection
18 devices connect to the panel process by means of a multi-conductor
cable, such as a category
19 5 (Cat 5) Ethernet cable 104 for a simple parallel transmission of
control and sensor signals or
ribbon cable for a serial connection of the collection devices in a daisy-
chain fashion in an
21 alternate embodiment. The current sensors connect to the collection
devices by means of a
22 simple twisted pair cable 105. The only external connection to the BCM
device, in this
23 implementation, is a power-over-Ethernet cable (PoE) 106 that interfaces
to a commercial-off-
24 the-shelf (COTS) PoE splitter 107. The PoE splitter 107 passes network
communications to
and from the panel processor Ethernet interface and the rest of the network,
and also provides
26 5V DC power to the panel processor.
27 [0040] Figures 5A and 5B show physical and logical depictions of
an example
28 implementation of a collection device and its corresponding current
sensors. In this particular
29 implementation, for example, the current sensors comprise current
transformer (CT) current
sensors 203 and the collection device comprises a current transformer
interface (CTIF) board
31 202. The CT current sensors 203 are coupled to each branch circuit and
provide a signal
32 indicative of the current flowing through the branch circuit to the CTIF
board collection devices
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1 202. In the case of the use of a CT current sensor 203, as shown in
Figures 5A and 5B, the CT
2 current sensor 203 may be both physically and inductively coupled to a
component in the
3 branch circuit, such as a power cable, a circuit breaker, or any other
component that has the full
4 or partial branch current. The CT current sensor 203 is also connected
directly to the CTIF
board collection device 202, providing the CTIF board collection device 202
with a signal that is
6 indicative of the current flowing through the branch circuit. Thus, for
example, if the servers
7 being supplied by the branch circuit consume between a low of about 6
amps and a high of
8 about 10 amps (e.g., during peak usage of the hosted website) at 120 VAC,
then the CT current
9 sensor 203 will produce a scaled AC voltage indicative of 6 to 10 amps
(e.g., according to the
turns ratio of the CT current sensor to the part the CT current sensor is
coupled to).
11 [0041] In this implementation, the CT current sensors 203 generate an
induced current
12 proportional to the actual current passing through a branch circuit
conductor that is installed
13 through the air gap core of the CT current sensor 203. The CT current
sensors 203, for
14 example, may comprise a split-core or solid core device. A split-core CT
current sensor 203, for
example, allows the CT core to open and enclose the conductor without
disconnecting or de-
16 energizing the circuit. A solid core CT current sensor 203 may be used
on a new installation
17 before the circuits are energized. As shown in Figures 2A and 2B, a
plurality of CT current
18 sensors 203 (e.g., eight (8) in one implementation), connect to a
collection device circuit board,
19 also known as the CT interface (CTIF) board collection device 202. A
plurality of CTIF boards
collection devices 202 connect to the panel processor 101 (e.g., via Cat 5
cables or other
21 methods) as previously described to give a total circuit capacity (e.g.,
a total capacity of at least
22 42 circuits in one implementation). One implementation supports six (6)
CTIF board collection
23 devices 202, although other implementations are possible. In one
implementation, each CTIF
24 board collection device 202 provides a signal termination resistor for
each of the connected CT
current sensors, converting the induced current that is proportional to the
branch circuit current
26 into a voltage by Ohm's Law. In other implementations, for example, a
digital signal (e.g., digital
27 word) representing the sampled current value may be generated. In still
another
28 implementation, a branch circuit current may be indirectly or directly
coupled with a Hall Effect
29 sensor to generate an AC or DC voltage proportional to the current in
the conductor (as a
function of time), or further converted to a DC signal through a rectifier or
other signal
31 conditioning circuit (e.g. integrator). Other implementations of
providing a signal representative
32 of a sampled current in a branch circuit may also be used.
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1 [0042] These voltages (or other signal indicative of the current
level sensed in a branch
2 circuit) are then routed to a single RMS-to-DC converter integrated
circuit 204 by means of a
3 multiplexer integrated circuit 205 under the control of a panel
processor, such as by way of
4 address select lines 207. In one implementation, an 8:1 multiplexer and
thus three (3) address
select lines 207 are used, although other configurations are possible. Other
implementations, for
6 example, could use a 16:1 or 32:1 multiplexer for supporting more CT
connections per CTIF
7 202. A benefit of using the RMS-to-DC converter circuitry 204 for the CT
current sensors 203 is
8 that the installation of the CT sensors 203 becomes non-critical since
there is no longer a
9 polarity associated with the current value, easing installation. In
another embodiment, the RMS-
to-DC converter 204 may be omitted for use with sensors other than CT sensors
203 that
11 product a DC voltage as their output, such as a Hall Effect current
sensor. The DC voltage
12 produced by the RMS-to-DC converter circuitry 204 (or directly from the
multiplexer 205 in the
13 case of a DC current sensor implementation) is transmitted to an
operational amplifier circuit
14 206 provides buffering and a low-impedance output for the CTIF board
collection device 202 for
transferring the DC voltage signal to the panel processor. In an alternate
implementation, the
16 operational amplifier circuit 206 could include non-inverting gain to
increase the amplitude of the
17 DC voltage. The DC voltage output of the operational amplifier 206 is
connected to the signal
18 output connector 208 of the CTIF board collection device 202. The output
signal radiometrically
19 corresponds to a specific branch circuit current, and the voltage is
then sampled by the panel
processor via an AID converter and a periodic interval, nominally once per
second (1 Hz), or at
21 a rate supported by the hardware and the customer's needs. In one
implementation, the panel
22 processor has a built-in AID converter that is multiplexed by the
operating system to appear as
23 individual ND converter inputs (e.g., seven individual ND converter
inputs). Other
24 implementations may employ external ND converter devices, either
multiplexed, or dedicated,
per CTIF board collection device 202, or even per CT sensor 203. The ND
converter, or ND
26 converters, may be part of the CTIF board collection device 202, or be
part of the panel
27 processor. In an alternate implementation, the CTIF board collection
device 202 has one or
28 more ND converters that transmit a CT digital word to the panel
processor by a digital signal. In
29 these implementations, the resulting digital signal value is then stored
in a panel processor
memory for later processing by software executing on the panel processor. The
panel
31 processor cycles through all the CTIF board collection devices 202 and
attached CT sensors
32 203 connected to the CTIF board collection devices 202 to represent all
the digital branch circuit
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1 current values and stores the digital branch circuit current values in
the panel processor
2 memory.
3 [0043] Figure 6 shows an example implementation of a system monitoring
a branch
4 circuit 300. A collection of digital values representing the branch
circuit currents are interpreted
by software executing on a panel processor as a current value, measured in
Amperes RMS. In
6 one implementation, for example, the panel processor executes two
interdependent programs
7 that retrieve, process, and communicate the branch circuit current values
to the end user, or to
8 another computer by means of a communications medium and protocol. In one
embodiment,
9 the programs are written in server-side JavaScript, known as node.js.
Other programming
languages such as, but not limited to, C, C++, or Python are possible in
alternate
11 implementations. As shown in Figure 6, the first program, called the CT
collection server
12 (ctcServer) 301, interfaces with the panel processor digital input and
output (I/O) signals 303A
13 and ND converter inputs 303B to set the digital bits of the address
lines connected to the
14 collection device's (e.g., a CTIF board collection device's)
multiplexers, and sample the voltage
output of the collection devices, respectively. The ctcServer program uses
control structures to
16 sequence and sample the DC voltage outputs presented by the collection
devices, and store the
17 converted digital value in a distinct memory location 304 for each
value. Upon completion of the
18 collection, conversion, and storage of all the DC voltage values
representing all the branch
19 circuit currents, then collates and transmits the digital values to the
second program via a
network socket protocol 305, although any type of communication such as a
generic
21 communication channel between a physical and/or logical layer may be
used. The second
22 program, called the branch circuit monitor server (bcmServer) 306,
receives the values from the
23 ctcServer 301, stores them in distinct memory locations 304, and
computes short-term statistics
24 307 on the values for each circuit such as maximum, minimum, and average
values, in addition
to the current real-time value of the branch circuit current. It also provides
for configuration of
26 the panel processor via privileged access. In one implementation, the
first and second
27 programs execute on the same panel processor. In an alternate
implementation, the two
28 programs execute on separate processors connected by a networking media
and protocol, or by
29 other physical and/or logical means.
[0044] The bcmServer 306 also instantiates and executes an embedded
hypertext transfer
31 protocol (HTTP) server 308 to provide one or more networked users 309
with one of several
32 visualizations of the branch circuit current data 310. The HTTP server
of the bcmServer 306
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1 can communicate with any number and type of HTTP clients such as, but not
limited to, Internet
2 Explorer, Firefox, or Google Chrome. The bcmServer 306 supports alarm
threshold that
3 activate if a branch circuit current exceed a set value, or values, on an
instantaneous, or time-
4 averaged basis. The bcmServer 306 will forward such alarm conditions to a
central computer,
or may display them on the embedded web server, or both. The bcmServer 306 web
server
6 allows privileged users to configure elements of the BCM such as
client/customer name
7 associated with a circuit, change circuit breaker amperage ratings, set,
modify, and clear
8 alarms, and perform built-in tests (BIT). The bcmServer 306 utilizes a
configuration file 311,
9 such as in a JavaScript Object Notation (JSON) format, to store the
parameters of each branch
circuit such as customer name, circuit number, breaker capacity, CT number,
etc. The
11 configuration file can be modified through the privileged access or
offline and uploaded to the
12 panel processor. Alternate formats for the configuration file such as,
but not limited to,
13 extensible markup language (XML) or comma separated values (CSV) are
possible in
14 alternative embodiments.
[0045] As shown in Figure 7, in one implementation, the BCM devices' one or
more panel
16 processor 400 communicate to a central computer 401 executing software
called the data
17 center server (dcServer) 402. The central computer 401, dcServer program
402, and two or
18 more BCM devices comprise a BCM System (BCMS). The BCMS allows
centralized access,
19 data storage, querying, retrieval, and visualization of all the circuits
in the data center.
Additionally, through the central computer 401 and the dcServer program 402,
the BCMS can
21 communicate with third-party data center information management (DCIM)
or building
22 management system (BMS) software 403 via standard or proprietary
protocols as desired by
23 the customer. Additionally, the central computer 401 and dcServer
software 402 may send
24 alarm, status, or diagnostic messages to networked users by means SMS
texts, email, or voice
communications.
26 [0046] One useful feature of the BCMS is the storage, querying,
and retrieval of historical
27 branch circuit's current data. The central computer 401 hosts a database
management system
28 (DBMS) 404 that stores and retrieves historical branch circuit current
data. The DBMS 404
29 allows short-, medium-, and long-range data storage for each branch
circuit. The panel
processors 101 will send a running-average value of each branch circuit at a
rate of once per
31 minute (1/60 Hz) to the central computer that stores each branch circuit
value in the DBMS 404.
32 In one implementation, the DBMS 404 will store these values in a
circular buffer such that the
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1 last 24 hours of 1/60 Hz data for each branch circuit current is
available for viewing or analysis.
2 Similarly, the DBMS 404 will calculate and store running averages for the
branch circuit currents
3 at rates of once per quarter hour, hour, six hours, and daily in a
similar circular buffer of length
4 commensurate with the sampling rate. Users can query, view, and analyze
branch circuit
current data in graphical format to look for trends or trouble conditions over
a plurality of time
6 and date ranges.
7 [0047] As shown in Figure 8, in an alternate embodiment, a BCMS
supports branch circuit
8 current monitoring of DC currents. In this embodiment, the current
sensors comprise
9 non-contact current sensors 501, such as using Hall Effect sensor devices
502 to produce a DC
voltage that is proportional to the DC or AC current flowing through a branch
circuit conductor.
11 In one implementation for measuring only DC currents, for example, the
collection devices will
12 bypass or omit the RMS-to-DC converter circuitry 504 and directly
connect the Hall Effect
13 sensor voltage through a multiplexer 505 to an operational amplifier
circuit 506. In one
14 embodiment of the Hall Effect sensor 501, the branch circuit conductor
is arranged parallel to
the major plane of the Hall Effect sensor and the current is inferred by means
of the Hall Effect.
16 Melexis produces Hall Effect current sensor integrated circuits that
support such an
17 arrangement. In an alternate embodiment of the Hall Effect sensor, the
branch circuit current
18 induces a magnetic flux 508 in a permeable core 509 similar to that of a
conventional CT, with
19 the Hall Effect sensor's main plane perpendicular to the flux flow.
Several manufacturers
produce Hall Effect sensors that support this arrangement. The software would
be minimally
21 changed to reflect a DC current versus an AC current.
22 [0048] As an alternate to the analog signal produced by the Hall
Effect sensor, a variation
23 of the aforementioned Hall Effect sensors outputs a digital signal, such
as a pulse width
24 modulation (PWM) waveform. This method provides increased accuracy and
immunity to noise
as compared to an analog output. In place of an ND converter, the panel
processor starts a
26 counter when the waveform transitions from low to high logic levels, and
stops the counter when
27 the waveform transitions from high to low logic levels. The counter
value is compared to a value
28 of the counter for a high to high logic level interval, indicating a
radiometric representation of the
29 current value.
[0049] In lieu of one or more current sensors connected to a collection
device, one or more
31 voltage sensors may be connected. A voltage sensor connects between a
phase voltage line
32 and the neutral line of a polyphase system, typically two or three
phases. The voltage sensor
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1 translates the line-to-neutral voltage down from a high voltage,
typically 120V RMS to a lower
2 voltage, typically less than 5V RMS. The voltage sensor output then
connects to the collection
3 device in a similar fashion as a current sensor. The voltage is applied
across the sensing
4 resistor in the same manner as the current sensor, and multiplexed and
converted to a DC
voltage via the RMS-to-DC converter integrated circuit, or a rectification
circuit. The DC voltage
6 is either transmitted to the panel processor and converted to a digital
value by means of the
7 panel processor ND converter, or directly converted by means of an ND
converter resident on
8 the collection device, and transmitted to the panel processor as a
digital signal to a digital input
9 port on the panel processor.
[0050] The resulting digital values of the phase voltages are interpreted
by the software on
11 the panel processor to represent Volts RMS. The phase voltages are
associated to one or more
12 branch circuits by a defined pattern. Thus, for each branch circuit, a
current sensor can
13 determine the branch circuit current measured in Amperes RMS, and the
phase voltage is
14 determined by a voltage sensor voltage measured in Volts RMS. From these
two values, the
apparent power can be accurately calculated measured in Volt-Amps (VA). The
apparent
16 power describes the accurate power drawn by the branch circuit. In
addition, energy usage by
17 the branch circuit can be calculated by integrating apparent power over
a time interval. The
18 resulting energy value is measured in Volt-Amp-hours (VA-h). This energy
value can be used in
19 subsequent calculations to estimate cooling requirements of a data
center based on energy
usage of equipment connected to branch circuits.
21 [0051] The aforementioned Hall Effect sensors 501 may be
calibrated to provide highly
22 accurate readings. Figure 9A depicts an example calibration setup. The
method to calibrate
23 one or more sensors involves using a goal-seek algorithm and a test
setup to provide a known
24 value of current through the representative conductor that the sensor
will be associated with by
means of a calibration station. The response parameters of the DC sensor are
an offset value
26 and a full-scale reading value, both defined in Amperes. These two
values are unique to each
27 sensor and stored in the JSON configuration file 311 as described above.
Figure 9B gives an
28 algorithm flowchart to accomplish the calibration for a sensor. The
algorithm may be extended
29 to allow calibration of any number of sensors that are connected to the
calibration station. Once
the calibration is complete, the new offset and full-scale values for each
sensor are stored it the
31 configuration file for use in an operational system. If a sensor is
replaced, or the conductor that
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1 it is measuring is changed, the calibration needs to be repeated with the
new sensor and/or the
2 new conductor.
3 [0052] Although embodiments of this invention have been described
above with a certain
4 degree of particularity, those skilled in the art could make numerous
alterations to the disclosed
embodiments without departing from the spirit or scope of this invention. All
directional
6 references (e.g., upper, lower, upward, downward, left, right, leftward,
rightward, top, bottom,
7 above, below, vertical, horizontal, clockwise, and counterclockwise) are
only used for
8 identification purposes to aid the reader's understanding of the present
invention, and do not
9 create limitations, particularly as to the position, orientation, or use
of the invention. Joinder
references (e.g., attached, coupled, connected, and the like) are to be
construed broadly and
11 may include intermediate members between a connection of elements and
relative movement
12 between elements. As such, joinder references do not necessarily infer
that two elements are
13 directly connected and in fixed relation to each other. It is intended
that all matter contained in
14 the above description or shown in the accompanying drawings shall be
interpreted as illustrative
only and not limiting. Changes in detail or structure may be made without
departing from the
16 spirit of the invention as defined in the appended claims.
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