U.S. patent application number 14/666283 was filed with the patent office on 2015-09-17 for branch circuit monitor.
This patent application is currently assigned to PRECISION AIR & ENERGY SERVICES, LLC. The applicant listed for this patent is PRECISION AIR & ENERGY SERVICES, LLC. Invention is credited to Daniel L. Janovy, David L. Janovy, Montgomery J. Sykora.
Application Number | 20150260767 14/666283 |
Document ID | / |
Family ID | 49725748 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150260767 |
Kind Code |
A1 |
Sykora; Montgomery J. ; et
al. |
September 17, 2015 |
Branch Circuit Monitor
Abstract
A branch circuit monitoring system (BCMS) for monitoring branch
circuit currents in one or more electrical circuit panels is
described. The system is comprised of a data center server, one or
more panel processors, each with one or more collection devices,
and one or more current sensors per collection device. The BCMS is
designed to be installed entirely inside the panel without the need
for a dedicated enclosure or power supply to facilitate ease of
installation and low-cost. The BCMS also allows for future
upgradability through standard software updates so that the system
can be updated or patched easily. The BCMS data center server
collects, aggregates, stores, and serves historical branch circuit
current data from the panel processors to networked users via a web
server to provide visualization of data such as tables, charts, and
gauges. Finally, the BCMS interfaces to third-party software suites
using industry-standard protocols such as Modbus.RTM. TCP and
BACnet.TM. for integration with data center infrastructure
management or building management system software.
Inventors: |
Sykora; Montgomery J.;
(Denver, CO) ; Janovy; Daniel L.; (Spearfish,
SD) ; Janovy; David L.; (Sturgis, SD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PRECISION AIR & ENERGY SERVICES, LLC |
Denver |
CO |
US |
|
|
Assignee: |
PRECISION AIR & ENERGY
SERVICES, LLC
Denver
CO
|
Family ID: |
49725748 |
Appl. No.: |
14/666283 |
Filed: |
March 23, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14108134 |
Dec 16, 2013 |
8988062 |
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14666283 |
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13963844 |
Aug 9, 2013 |
8610438 |
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14108134 |
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61681406 |
Aug 9, 2012 |
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61681527 |
Aug 9, 2012 |
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Current U.S.
Class: |
324/119 |
Current CPC
Class: |
G01R 15/202 20130101;
G01R 19/22 20130101; G01R 15/183 20130101; G01R 19/2513
20130101 |
International
Class: |
G01R 19/22 20060101
G01R019/22; G01R 19/25 20060101 G01R019/25; G01R 15/18 20060101
G01R015/18 |
Claims
1. A branch circuit monitoring system comprising: a first
collection device configured to receive signals indicative of a
measured current value in at least one branch circuit of a first
plurality of branch circuits and convert the signals indicative of
the measured current value in the at least one branch circuit of
the first plurality of branch circuits from an alternating current
(AC) signal to a direct current (DC) signal; a second collection
device configured to receive signals indicative of a measured
current value in at least one branch circuit of a second plurality
of branch circuits and convert the signals indicative of the
measured current value in the at least one branch circuit of the
second plurality of branch circuits from an alternating current
(AC) signal to a direct current (DC) signal; and a panel processor
in communication with the first and second collection devices
configured to receive the plurality of DC signals, the panel
processor configured to store in a local memory a plurality of data
structures comprising the measured branch circuit current data
values for said branch circuit along with a timestamp associated
with a time at which the currents were measured.
2. The branch circuit monitoring system of claim 1 further
comprising a branch circuit monitor server and an associated
database, the branch circuit monitor server in communication with
the panel processor by means of a network or communication channel
and configured to receive the plurality of data structures from the
panel processor.
3. The branch circuit monitoring system of claim 1 further
comprising: a first plurality of current sensors configured to be
coupled to the at least one branch circuit of the first plurality
of branch circuits and to measure a current within one of the
respective first plurality of branch circuits and to provide the
signal indicative of the measured current value in the at least one
branch circuit of the first plurality of branch circuits; and a
second plurality of current sensors configured to be coupled to the
at least one branch circuit of the second plurality of branch
circuits and to measure a current within one of the respective
second plurality of branch circuits and to provide the signal
indicative of the measured current value in the at least one branch
circuit of the second plurality of branch circuits.
4. The branch circuit monitoring system of claim 3 wherein the
first and second plurality of current sensors each comprise a
current transformer.
5. The branch circuit monitoring system of claim 3 wherein at least
two of the first plurality of current sensors are each coupled with
a sub-branch of a first branch circuit of the first plurality of
branch circuits and configured to measure a current value within
the sub-branches of the first branch circuit of the first plurality
of branch circuits.
6. The branch circuit monitoring system of claim 5 wherein a
measured current value of the first branch circuit is determined by
summing the measured current values of each of the
sub-branches.
7. The branch circuit monitoring system of claim 1 wherein the
panel processor polls the first and second collection devices for
the first and second DC signals.
8. The branch circuit monitoring system of claim 1 wherein the data
structure comprises a branch identifier, a measured current and a
time stamp.
9. The branch circuit monitoring system of claim 1 wherein the
panel processor is configured to provide the data structure over a
data connection to a building management system.
10. The branch monitoring system of claim 1 further comprising a
building management system running on a server machine, the
building management system including a branch circuit monitoring
module configured to receive the branch circuit monitoring data
over a data connection, the branch circuit monitoring module
further configured to display the branch circuit monitoring data
within the building management system.
11. The branch monitoring system of claim 1 wherein the signal
indicative of the measured current comprises a voltage level.
12. The branch monitoring system of claim 1 wherein the signal
indicative of the measured current comprises a digital value.
13. The branch monitoring system of claim 1 wherein each of the
first and second collection devices comprises a rectifier/signal
conditioning element, an analog to digital converter and an output
connection to convert the signals indicative of the measured
current value from each of the first and second plurality of
current sensors to the first and second DC signals,
respectively.
14. The branch circuit monitoring system of claim 13 wherein the
rectifier/signal conditioning element comprises a resistor coupled
to a voltage rectifier and is configured to convert an AC resistor
voltage to an equivalent DC voltage.
15. The branch circuit monitoring system of claim 14 wherein the
rectifier/signal conditioning element further comprises a signal
conditioner configured to prepare a signal for use by an analog to
digital converter.
16. The branch circuit monitoring system of claim 1 wherein the
panel processor is configured for self-discovery of a new
collection device.
17. A method of monitoring branch circuits comprising: receiving,
at a first collection device, a first plurality of signals
indicative of a first plurality of measured current values of a
first plurality of branch circuits; converting, at the first
collection device, the signals indicative of the measured current
value of the first plurality of branch circuits from a first
alternating current (AC) signal to a first direct current (DC)
signal; receiving, at a second collection device, a second
plurality of signals indicative of a second plurality of measured
current values of a second plurality of branch circuits;
converting, at the second collection device, the signals indicative
of the measured current value of the second plurality of branch
circuits from a second alternating current (AC) signal to a second
direct current (DC) signal; receiving, at a panel processor in
communication 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 measured branch circuit current data values for said
branch circuit along with a timestamp associated with a time at
which the currents were measured.
18. The method of claim 17 further comprising measuring a first
plurality of currents within the first plurality of branch circuits
using a first plurality of current sensors each coupled with a
respective branch of the first plurality of branch circuits.
19. The method of claim 18 wherein at least two of the first
plurality of current sensors are each coupled with a sub-branch of
a first branch circuit of the first plurality of branch circuits
and configured to measure a current value within the sub-branches
of the first branch circuit of the first plurality of branch
circuits.
20. The method of claim 19 wherein a measured current value of the
first branch circuit is determined by summing the measured current
values of each of the sub-branches.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/108,134 entitled "Branch Circuit Monitor"
filed by Montgomery J. Sykora et al. on Dec. 16, 2013, which is a
continuation of U.S. patent application Ser. No. 13/963,844
entitled "Branch Circuit Monitor" filed by Montgomery J. Sykora et
al. on Aug. 9, 2013, each of which is hereby incorporated by
reference as though fully set forth herein.
[0002] This application also claims the benefit, through the Ser.
No. 13/963,844 application, of U.S. provisional application No.
61/681,406 entitled "Apparatus, System and Method for Branch
Circuit Monitoring" filed by Montgomery J. Sykora et al. on Aug. 9,
2012 and U.S. provisional application No. 61/681,527 entitled
"Apparatus, 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 Aug. 9, 2012, both
provisional applications are also hereby incorporated by reference
as though fully set forth herein.
BACKGROUND
[0003] 1. Field
[0004] Aspects of the present disclosure involve a branch circuit
monitoring system providing information concerning the utilization
of individual branch circuits, particularly within a data center,
and providing the ability to manage those circuits so that
individual circuits are not overloaded while at the same time fully
utilizing various circuits.
[0005] 2. Background
[0006] Branch circuit monitoring (BCM) devices typically utilize a
multitude of current transformers (CTs) connected to a sampling and
processing board, either directly or via an intermediary circuit
board. The CTs generate a voltage or current electric signal that
is 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 current.
Additional calculations such as real power, apparent power, power
factor, and kWh are possible with the estimation or measurement of
the voltage of the branch circuit. However, because the circuits
are limited by the circuit breaker current rating, the most
important and 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 current total. Some BCM devices use digital signal processors
and a multitude of analog-to-digital (A/D) converters to accomplish
this. As the number of circuits monitored grows, the size and
complexity of the collection and processing circuitry increases,
leading to large systems and relatively high prices per panel. A
typical data center may have hundreds of panels and thousands of
circuits to monitor, making conventional BCM devices prohibitively
expensive to install.
[0007] Typical BCM devices require that the circuit panel be
de-energized to pass the circuit wires through the CTs, making
retrofits difficult in data centers that need continuous operation
(or up-time). Use of split-core CTs alleviates some of the
difficulty of installing a BCM in a "live" panel, but in general,
the main processing circuitry still has the disadvantage of being
large and requiring a separate cabinet and power supply for
installation. These two requirements increase the cost and
complexity of the BCM device installation.
[0008] In addition, most prior art BCM devices are designed with
application-specific processors and circuitry. This makes upgrading
or improving the system difficult and expensive, if even
possible.
BRIEF SUMMARY
[0009] In accordance with one embodiment a branch circuit
monitoring (BCM) device comprises a programmable panel processor, a
plurality of small, modular collection devices, and a plurality of
non-contact current sensors.
[0010] Accordingly several disadvantages described above can be
alleviated or mitigated by the apparatus, system and methods
described herein along with additional desirable features.
[0011] An improved branch circuit monitoring device, system and
methods are described herein. The device, system and methods
overcome the major issues with current BCM devices and systems:
high cost, installation complexity, and obsolescence. These factors
are interrelated and are addressed by multiple approaches and
methods. Together, the features and improvements presented make
branch circuit current monitoring affordable and feasible for
existing data centers.
[0012] The complexity of the BCM device is reduced while
simultaneously decreasing the 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 accurate RMS-to-DC voltage converter circuitry
on small, decentralized collection boards allows for relatively
inexpensive general purpose processor to be utilized for the data
aggregation and processing while maintaining highly accurate
current values. Finally, standard networking protocols such as TCP,
HTTP, UDP, as well as any specific protocols such as BACnet.TM.,
Modbus.RTM., or SNMP are supported. The system supports long-term
data storage, retrieval, and visualization using modern,
open-source programs and methods and the ability to integrate
numerous BCM devices into a system.
[0013] In one implementation, a branch circuit monitoring system is
provided comprising: a first collection device configured to
receive signals indicative of a measured current value in at least
one branch circuit of a first plurality of branch circuits and
convert the signals indicative of the measured current value in the
at least one branch circuit of the first plurality of branch
circuits from an alternating current (AC) signal to a direct
current (DC) signal; a second collection device configured to
receive signals indicative of a measured current value in at least
one branch circuit of a second plurality of branch circuits and
convert the signals indicative of the measured current value in the
at least one branch circuit of the second plurality of branch
circuits from an alternating current (AC) signal to a direct
current (DC) signal; and a panel processor in communication with
the first and second collection devices configured to receive the
plurality of DC signals, the panel processor configured to store in
a local memory a plurality of data structures comprising the
measured branch circuit current data values for said branch circuit
along with a timestamp associated with a time at which the currents
were measured.
[0014] In another implementation, a method of monitoring branch
circuits is provided comprising: receiving, at a first collection
device, a first plurality of signals indicative of a first
plurality of measured current values of a first plurality of branch
circuits; converting, at the first collection device, the signals
indicative of the measured current value of the first plurality of
branch circuits from a first alternating current (AC) signal to a
first direct current (DC) signal; receiving, at a second collection
device, a second plurality of signals indicative of a second
plurality of measured current values of a second plurality of
branch circuits; converting, at the second collection device, the
signals indicative of the measured current value of the second
plurality of branch circuits from a second alternating current (AC)
signal to a second direct current (DC) signal; receiving, at a
panel processor in communication 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 measured branch circuit current
data values for said branch circuit along with a timestamp
associated with a time at which the currents were measured.
[0015] The foregoing and other aspects, features, details,
utilities, and advantages of the present invention will be apparent
from reading the following description and claims, and from
reviewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows an example implementation of a branch circuit
monitoring system.
[0017] FIG. 2 shows an example implementation of a collection
device that may be used within a branch circuit monitoring system
such as shown in FIG. 1.
[0018] FIG. 3 shows example implementation of a panel processor
coupled to a plurality of collection devices.
[0019] FIG. 4 is a view of an example BCM device installed in a
circuit panel board.
[0020] FIG. 5A shows an example collection device circuit board,
also known as a CT interface (CTIF) board.
[0021] FIG. 5B shows a simplified schematic of an example analog
processing chain on the CTIF board.
[0022] FIG. 6 shows the BCM device from software and networking
perspectives.
[0023] FIG. 7 shows the BCM System (BCMS) block diagram.
[0024] FIG. 8 shows the alternate embodiment of the CTIF board with
Hall Effect sensors.
[0025] FIG. 9A depicts a calibration setup.
[0026] FIG. 9B gives an example algorithm flowchart to accomplish
the calibration for a sensor.
DETAILED DESCRIPTION
[0027] Modern data centers host a tremendous number of computing
devices, such as web servers and the data storage systems necessary
for enterprise software operations, cloud computing, Internet
access and applications, and numerous other computing functions.
The power for the physical equipment within the data center is
supplied by branch circuits. So, for 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 FIG.
1, originate from a power panel where the source of power is
received, which may be a 120 volt, 208 volt or other alternating
current (AC) supply, and which may be two or three phase. The power
supplied to the panel is then distributed across some number of
discrete branch circuits. Conventional panels may include 42 or 72
branch circuits with each circuit also including a breaker.
[0028] FIG. 1 shows one example implementation of a branch circuit
monitoring device 10. A branch circuit monitor 10 is a device that
enables the monitoring of individual branch circuits 12 of an
electrical panel 14. A typical panel contains 42 or 72 branch
circuits, although other panel configurations are possible. These
circuits are then routed to equipment or 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 used, for example, to trigger alarms,
both locally and remotely, as well as be archived in a database for
retrieval and analysis.
[0029] In one example, the branch current monitor 10 is configured
to measure and log the 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 cases, more than one current sensor 16 may be deployed
across various sub-branches of a branch circuit 12. The sub-branch
currents may later be summed, such as by a management board, to
determine a total branch current.
[0030] In one implementation, each of the current sensors 16 (e.g.,
current transformers (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 with a signal indicative of the branch circuit
current. The collection device 18 uses the signal from the current
sensor 16 to produce a voltage (or other signal) indicative of the
measured current that can be understood by a panel processor 20.
The panel processor 20 receives each 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 later relayed to a server, such as the Data
Center BCM Server 24 shown in FIG. 1, for longer term storage in a
database, such as BCM Database 26 shown in FIG. 1. The server 24
may periodically report measurements to a building management
system (BMS) 28 and/or to a user. 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 report data or other
information to a user.
[0031] FIG. 2 shows an example implementation of a collection
device 40 (in this implementation, a current measurement board
although other collection devices are contemplated) that may be
used within a branch circuit monitoring system, such as the branch
circuit monitor 10 shown in FIG. 1. In this particular
implementation, the collection device may utilize any method form
measuring current and provide the current measurement to a panel
processor 50 (shown in FIG. 3). As shown in FIG. 2, the collection
device 40 may include a rectifier/signal conditioning element 42,
an analog-to-digital (A/D) converter 44, and an output 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 example, the
rectifier/signal conditioning element 42 may comprise a resistor
coupled to a voltage rectifier to convert the AC resistor voltage
to an equivalent direct current (DC) voltage. The resistor may be
connected to the terminals of the current sensor 38 (e.g., CT).
When 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 voltage. In many cases, it may be beneficial to convert the AC
resistor voltage to an equivalent DC voltage using the rectifier of
the rectifier/signal conditioning element 42. This element may also
comprise a signal conditioner configured to prepare the signal for
use by the A/D converter 44. The signal may be amplified (or scaled
down) to be in an operable range of the A/D converter 44 and may
also be filtered to remove excess noise. For example, the A/D
converter 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 to produce an output signal. The rectified and
conditioned signal is then communicated to the A/D converter 44
which then converts the signals from each current sensor 48 into
digital values and produces an output for transmission to the panel
processor 50. The A/D converter 44 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 configured to receive DC power from the
panel processor 50.
[0032] In one specific implementation, each collection device is
connected with or otherwise configured to receive an input from N
current sensors 48 (e.g., 1 to 8 current 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 device or a plurality of collection
devices depending on the number of branch circuits and the
implementation of the collection devices.
[0033] FIG. 3 shows an example implementation of a panel processor
50 coupled to a plurality of individual collection devices 40, such
as the collection device 40 shown in FIG. 2. In one example, the
panel processor 50 may comprise an input circuit 52, a processor
54, a data storage element such as a memory 56, and a network
connection 58. The processor 54 is configured to perform current
calculations by executing instructions stored in the memory 56. The
memory 56 may also store any needed constant values for current
calculations. Once each 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 then be used to send the current measurement(s),
the address(es), and a timestamp(s) to a server 60 at regular
intervals, irregular intervals, or based on a command from the
server 60. Furthermore, the panel processor 50 may receive
configuration data from the user via the server 60.
[0034] A branch circuit monitoring server 60 is coupled with each
panel processor within a data center. Since there may be hundreds
of panels in a data center, there may in turn be hundreds of panel
processors obtaining and recording data from thousands of branch
circuits. The server 60 is connected with a database (see, e.g.,
FIG. 1) and is configured to request data from the processors 54 of
the panel processors 50 and store the collected data in the
database (or other form of data storage). Like the processor 54,
the database may include the 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 cleared thereby allowing the memory size at the panel
processors 50 to be relatively small. Similarly, the collection
device may have only sufficient memory to store only the most
recent measurements or some number of measurements that would occur
between polling cycles of the panel processor to the collection
device.
[0035] The server 60, panel processors 50 and collection devices 40
are arranged in a programmable modular system. Thus, the system may
be deployed in any data center with any number of branch circuits;
the system easily adapts to the addition or removal of circuits,
and does not require extensive customization for deployment.
Moreover, the server 60 and panel 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 building management system may be configured
to receive and display the measured parameters. In one example, the
building management system is connected to the server by way of a
Modbus.RTM. TCP connection, although other forms of standard or
proprietary communications protocols are possible.
[0036] Besides the ability to view the data, the system also
provides the data center or the purchasers of a circuit to manage
the circuit usage. In one example, the data center may utilize the
full capacity of a given circuit or set of circuits before
installing additional panels and circuits. If, for example, a 20
amp circuit is a supplying at most 10 amps, then there are
approximately 8 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 additional underutilized capacity. Thus, the
circuits may be rearranged or additional equipment coupled with the
circuit rather than adding additional panels. Similarly, if a
circuit is running over its maximum rated capacity, say
consistently at or near 20 amps, then some load can be 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 automatically notify the
user when such conditions occur.
[0037] In this implementation, the panel processor 50 is connected
with and configured to collect data, such as via polling or
interrupt, from the collection devices 40 (e.g., a plurality of
individual current measurement boards). In one specific
implementation, for example, each of 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 as I2C, SPI, or USB. As discussed
above, the panel processor 50 includes an input 52 for receiving
the data from the collection devices 40, a processor 54, and a
storage device, such as some form of memory 56, where the data is
stored at the panel processor 50. In one example, 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.
[0038] In one implementation, each collection device is connected
with or otherwise configured to receive input from eight current
sensors. Depending on the implementation, however, any number of
branch circuits may be connected with a collection device. In one
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 store
the measured current with association to the branch circuit where
the measurement was taken as well as the time.
[0039] The panel processor 50 receives the measurements from each
of the current 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 adapted to receive a very large number of signals as the
system is expanded to cover more and more branch circuits. For
example, the panel processor 50 may have one input for every
current sensor. To handle these inputs, the panel processor 50 may
employ an input circuit 52 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.
[0040] Once receiving the current measurements, the panel processor
50 may then convert the voltage measurements into current readings
constantly, according to a schedule, or according to a user
command. Using the example provided above, the panel processor 50
may 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 Ohm's
law and accounting for any gain produced by the output circuit) and
compensating for the turns ratio of the CT.
[0041] One particular implementation of a BCM device 100 is
illustrated in FIG. 4. In this particular implementation, the BCM
device 100 comprises a panel processor 101, one or more collection
devices 102 (e.g., current measurement or collection circuit
boards), and one or more 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 special purpose processor, an ASIC, a digital signal
processor (DSP) or the like. In the particular implementation of
FIG. 3, for example, the panel processor comprises an ARM Cortex-8
processor using a Linux operating system with an easily modifiable
programming 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 systems
such as an Intel Atom processor using Windows 8 RT can be used. In
one implementation, the BCM device uses split-core CT current
sensors on each circuit to allow for easy installation of "live"
panels without the need to de-energize.
[0042] 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 panel
processor, collection boards, and current sensors are small modular
devices that are adapted to be installed inside of the panel
enclosure. In this implementation, the collection devices connect
to the panel process by means of a multi-conductor cable, such as a
category 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 alternate embodiment. The current sensors connect to
the collection devices by means of a simple twisted pair cable 105.
The only external connection to the BCM device, in this
implementation, is a power-over-Ethernet cable (PoE) 106 that
interfaces to a commercial-off-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 5V DC power to the panel processor.
[0043] FIGS. 5A and 5B show physical and logical depictions of an
example implementation of a collection device and its corresponding
current sensors. In this particular implementation, for example,
the current sensors comprise current transformer (CT) current
sensors 203 and the collection device comprises a current
transformer interface (CTIF) board 202. The CT current sensors 203
are coupled to each branch circuit and provide a signal indicative
of the current flowing through the branch circuit to the CTIF board
collection devices 202. In the case of the use of a CT current
sensor 203, as shown in FIGS. 5A and 5B, the CT current sensor 203
may be both physically and inductively coupled to a component in
the branch circuit, such as a power cable, a circuit breaker, or
any other component that has the full 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 indicative of the current flowing
through the branch circuit. Thus, for example, if the servers being
supplied by the branch circuit consume between a low of about 6
amps and a high of about 10 amps (e.g., during peak usage of the
hosted website) at 120 VAC, then the CT current 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).
[0044] In this implementation, the CT current sensors 203 generate
an induced current proportional to the actual current passing
through a branch circuit conductor that is installed through the
air gap core of the CT current sensor 203. The CT current sensors
203, for 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-energizing the circuit. A solid core CT current sensor 203 may
be used on a new installation before the circuits are energized. As
shown in FIGS. 2A and 2B, a plurality of CT current sensors 203
(e.g., eight (8) in one implementation), connect to a collection
device circuit board, 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 methods) as previously described to give a total
circuit capacity (e.g., a total capacity of at least 42 circuits in
one implementation). One implementation supports six (6) CTIF board
collection devices 202, although other implementations are
possible. In one implementation, each CTIF 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 into a voltage by
Ohm's Law. In other implementations, for example, a digital signal
(e.g., digital word) representing the sampled current value may be
generated. In still another implementation, a branch circuit
current may be indirectly or directly coupled with a Hall Effect
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 conditioning circuit
(e.g. integrator). Other implementations of providing a signal
representative of a sampled current in a branch circuit may also be
used.
[0045] These voltages (or other signal indicative of the current
level sensed in a branch circuit) are then routed to a single
RMS-to-DC converter integrated circuit 204 by means of a
multiplexer integrated circuit 205 under the control of a panel
processor, such as by way of 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 example, could use a 16:1 or
32:1 multiplexer for supporting more CT connections per CTIF 202. A
benefit of using the RMS-to-DC converter circuitry 204 for the CT
current sensors 203 is that the installation of the CT sensors 203
becomes non-critical since there is no longer a 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 product a DC voltage as their
output, such as a Hall Effect current sensor. The DC voltage
produced by the RMS-to-DC converter circuitry 204 (or directly from
the multiplexer 205 in the case of a DC current sensor
implementation) is transmitted to an operational amplifier circuit
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
operational amplifier circuit 206 could include non-inverting gain
to increase the amplitude of the DC voltage. The DC voltage output
of the operational amplifier 206 is connected to the signal output
connector 208 of the CTIF board collection device 202. The output
signal radiometrically corresponds to a specific branch circuit
current, and the voltage is then sampled by the panel processor via
an A/D converter and a periodic interval, nominally once per second
(1 Hz), or at a rate supported by the hardware and the customer's
needs. In one implementation, the panel processor has a built-in
A/D converter that is multiplexed by the operating system to appear
as individual A/D converter inputs (e.g., seven individual A/D
converter inputs). Other implementations may employ external A/D
converter devices, either multiplexed, or dedicated, per CTIF board
collection device 202, or even per CT sensor 203. The A/D
converter, or A/D converters, may be part of the CTIF board
collection device 202, or be part of the panel processor. In an
alternate implementation, the CTIF board collection device 202 has
one or more A/D converters that transmit a CT digital word to the
panel processor by a digital signal. In 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 processor cycles through all the CTIF board
collection devices 202 and attached CT sensors 203 connected to the
CTIF board collection devices 202 to represent all the digital
branch circuit current values and stores the digital branch circuit
current values in the panel processor memory.
[0046] FIG. 6 shows an example implementation of a system
monitoring a branch 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 one implementation, for example, the
panel processor executes two interdependent programs that retrieve,
process, and communicate the branch circuit current values to the
end user, or to another computer by means of a communications
medium and protocol. In one embodiment, 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 implementations. As shown in FIG. 6, the
first program, called the CT collection server (ctcServer) 301,
interfaces with the panel processor digital input and output (I/O)
signals 303A and A/D converter inputs 303B to set the digital bits
of the address lines connected to the 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 sequence and sample
the DC voltage outputs presented by the collection devices, and
store the converted digital value in a distinct memory location 304
for each value. Upon completion of the collection, conversion, and
storage of all the DC voltage values representing all the branch
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 communication channel
between a physical and/or logical layer may be used. The second
program, called the branch circuit monitor server (bcmServer) 306,
receives the values from the ctcServer 301, stores them in distinct
memory locations 304, and computes short-term statistics 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 the panel
processor via privileged access. In one implementation, the first
and second programs execute on the same panel processor. In an
alternate implementation, the two programs execute on separate
processors connected by a networking media and protocol, or by
other physical and/or logical means.
[0047] The bcmServer 306 also instantiates and executes an embedded
hypertext transfer protocol (HTTP) server 308 to provide one or
more networked users 309 with one of several visualizations of the
branch circuit current data 310. The HTTP server of the bcmServer
306 can communicate with any number and type of HTTP clients such
as, but not limited to, Internet Explorer, Firefox, or Google
Chrome. The bcmServer 306 supports alarm threshold that activate if
a branch circuit current exceed a set value, or values, on an
instantaneous, or time-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 allows privileged users to configure elements of the BCM
such as client/customer name associated with a circuit, change
circuit breaker amperage ratings, set, modify, and clear alarms,
and perform built-in tests (BIT). The bcmServer 306 utilizes a
configuration file 311, 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 configuration file can be modified through the privileged
access or offline and uploaded to the panel processor. Alternate
formats for the configuration file such as, but not limited to,
extensible markup language (XML) or comma separated values (CSV)
are possible in alternative embodiments.
[0048] As shown in FIG. 7, in one implementation, the BCM devices'
one or more panel processor 400 communicate to a central computer
401 executing software called the data center server (dcServer)
402. The central computer 401, dcServer program 402, and two or
more BCM devices comprise a BCM System (BCMS). The BCMS allows
centralized access, 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 communicate with third-party data center information
management (DCIM) or building management system (BMS) software 403
via standard or proprietary protocols as desired by the customer.
Additionally, the central computer 401 and dcServer software 402
may send alarm, status, or diagnostic messages to networked users
by means SMS texts, email, or voice communications.
[0049] One useful feature of the BCMS is the storage, querying, and
retrieval of historical branch circuit's current data. The central
computer 401 hosts a database management system (DBMS) 404 that
stores and retrieves historical branch circuit current data. The
DBMS 404 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
minute ( 1/60 Hz) to the central computer that stores each branch
circuit value in the DBMS 404. In one implementation, the DBMS 404
will store these values in a circular buffer such that the last 24
hours of 1/60 Hz data for each branch circuit current is available
for viewing or analysis. Similarly, the DBMS 404 will calculate and
store running averages for the branch circuit currents at rates of
once per quarter hour, hour, six hours, and daily in a similar
circular buffer of length 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 and date ranges.
[0050] As shown in FIG. 8, in an alternate embodiment, a BCMS
supports branch circuit current monitoring of DC currents. In this
embodiment, the current sensors comprise 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. In one implementation
for measuring only DC currents, for example, the collection devices
will bypass or omit the RMS-to-DC converter circuitry 504 and
directly connect the Hall Effect sensor voltage through a
multiplexer 505 to an operational amplifier circuit 506. In one
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. Melexis produces Hall Effect current sensor integrated
circuits that support such an arrangement. In an alternate
embodiment of the Hall Effect sensor, the branch circuit current
induces a magnetic flux 508 in a permeable core 509 similar to that
of a conventional CT, with 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 changed to reflect a DC current versus an AC current.
[0051] As an alternate to the analog signal produced by the Hall
Effect sensor, a variation of the aforementioned Hall Effect
sensors outputs a digital signal, such as a pulse width modulation
(PWM) waveform. This method provides increased accuracy and
immunity to noise as compared to an analog output. In place of an
A/D converter, the panel processor starts a counter when the
waveform transitions from low to high logic levels, and stops the
counter when the waveform transitions from high to low logic
levels. The counter value is compared to a value of the counter for
a high to high logic level interval, indicating a radiometric
representation of the current value.
[0052] In lieu of one or more current sensors connected to a
collection device, one or more voltage sensors may be connected. A
voltage sensor connects between a phase voltage line and the
neutral line of a polyphase system, typically two or three phases.
The voltage sensor translates the line-to-neutral voltage down from
a high voltage, typically 120V RMS to a lower voltage, typically
less than 5V RMS. The voltage sensor output then connects to the
collection device in a similar fashion as a current sensor. The
voltage is applied across the sensing 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 is either transmitted to the
panel processor and converted to a digital value by means of the
panel processor A/D converter, or directly converted by means of an
A/D converter resident on the collection device, and transmitted to
the panel processor as a digital signal to a digital input port on
the panel processor.
[0053] The resulting digital values of the phase voltages are
interpreted by the software on the panel processor to represent
Volts RMS. The phase voltages are associated to one or more branch
circuits by a defined pattern. Thus, for each branch circuit, a
current sensor can determine the branch circuit current measured in
Amperes RMS, and the phase voltage is 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 power describes the accurate power drawn by the
branch circuit. In addition, energy usage by the branch circuit can
be calculated by integrating apparent power over a time interval.
The resulting energy value is measured in Volt-Amp-hours (VA-h).
This energy value can be used in subsequent calculations to
estimate cooling requirements of a data center based on energy
usage of equipment connected to branch circuits.
[0054] The aforementioned Hall Effect sensors 501 may be calibrated
to provide highly accurate readings. FIG. 9A depicts an example
calibration setup. The method to calibrate one or more sensors
involves using a goal-seek algorithm and a test setup to provide a
known 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 and a full-scale reading value, both defined in Amperes.
These two values are unique to each sensor and stored in the JSON
configuration file 311 as described above. FIG. 9B gives an
algorithm flowchart to accomplish the calibration for a sensor. The
algorithm may be extended 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 configuration file for use in an
operational system. If a sensor is replaced, or the conductor that
it is measuring is changed, the calibration needs to be repeated
with the new sensor and/or the new conductor.
[0055] Although embodiments of this invention have been described
above with a certain 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 references (e.g., upper, lower, upward, downward, left,
right, leftward, rightward, top, bottom, above, below, vertical,
horizontal, clockwise, and counterclockwise) are only used for
identification purposes to aid the reader's understanding of the
present invention, and do not 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 may include intermediate members
between a connection of elements and relative movement between
elements. As such, joinder references do not necessarily infer that
two elements are directly connected and in fixed relation to each
other. It is intended that all matter contained in 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 spirit
of the invention as defined in the appended claims.
* * * * *