Patent Application
20120209549
Determining business planning implications from technical operating data, such the quality of electrical power supplied to equipment, can be challenging. This is because technical operating data is presented in terms not readily understood by those not versed in the particular technical area. Thus, while many metering products monitor and summarize technical operating data, they may fail to present the information in a manner that can readily provide guidance for business planning.
Methods and apparatus are provided for assessing equipment related risk based on electrical event data. An electrical event is an electrical voltage or current that falls outside a nominal range during an event duration. The electrical event data for electricity supplied to electrically-powered equipment is analyzed and one or more types of equipment related risk associated with an electrical event are quantified based on the electrical event data. A visual representation of the quantified one or more equipment related risks is provided.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various example systems, methods, and other example embodiments of various aspects of the invention. It will be appreciated that the illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. One of ordinary skill in the art will appreciate that in some examples one element may be designed as multiple elements or that multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa. Furthermore, elements may not be drawn to scale.
The quality of electrical power supplied to the equipment in an enterprise has short and long term business risk implications. For example, when the voltage supplied to equipment falls below a nominal value the equipment may shut down due to insufficient power. This low voltage condition, called a sag, creates process risk because the processes performed by the equipment may be interrupted. Process risk is a relatively short term risk that can happen unexpectedly and have serious financial impact if important functions are interrupted.
When voltage supplied to equipment rises above a nominal value, which is typically called a swell, the equipment may be damaged due to overheating or arcing. While the equipment may continue to function during and after a swell, it may have sustained incremental damage that will shorten the time until it must be repaired or replaced. Thus, swells tend to create capital risk associated with shortened equipment lifespan.
Process risk and capital risk present different business planning implications that should be factored into decision making. Some metering systems are capable of rating the severity of sags and swells and presenting the rating information in graphical form. However, these metering systems do not quantify business planning risk associated with the sags and swells experienced by an enterprise's equipment.
In one embodiment, the quantified process risk and capital risk can be communicated by way of a visual representation such as the scatter plot 100 shown in
Events that fall at the high end of both process and capital risk may be the result of an arc fault event. These types of events may be a safety concern and a business planner may want to further investigate when such an event occurs. Events that fall at the low end of both process and capital risk are often sub-cycle (short in duration) events such as a switching or addition of a power-factor correction capacitor, which is a routine occurrence that incurs negligible risk. The scatter plot may include additional labels in various regions to provide context for the points on the plot. The labels may be tailored to a specific site or equipment.
In some embodiments, the system 200 includes a meter 210 that monitors electricity supplied to equipment and produces the electrical event data. The risk assessment tool 220 may reside in a specially equipped meter. In other embodiments, the risk assessment tool 220 may reside in a remote device connected to the meter 210 by way of a web server (not shown). In this embodiment, several meters may provide electrical data to the same risk assessment tool 220 via the Internet. The system 200 will typically include electronic storage media (not shown) in either the meter 210 or risk assessment tool 220, or both, for storing the electrical event data for analysis purposes. The system 200 includes a user interface 230 configured to communicate the quantified risk (e.g., scatter plot) produced by the risk assessment tool 220. As with the meter 210, the user interface 230 may be provided as part of a specially equipped meter or by way of a remote device coupled to a web server.
V=0.87−0.159e−0158T−0.841e−4.63/(1−e−4.63T) (EQ 1)
The voltage V is the lowest voltage that occurs during the sag event and the time T is the duration of time during which the voltage was below nominal. Voltage is represented as a percent of nominal and time is presented in seconds on a logarithmic scale. Equation 1 describes a Level 2 (L2) sag which is considered to present a lowest “acceptable” sag. A Level 8 (L8) sag, which is consider to present a maximum possible process risk is described by Equation 2:
V=0.55−0.159e−0158T−0.841e−4.63/(1−e−4.63T) (EQ 2)
Intermediate levels may be interpolated between the L2 and L8 levels. For example, an L5 curve would be the average of the L2 and L8 curves. In some existing metering systems, a sag event is fitted to a nearest curve so that it can be classified as one of seven levels (L2-L8). Sag events that fall above the L2 curve are categorized as L2 sag events and sag events that fall below the L8 curve are characterized as L8 sag events.
Using the same formula with different coefficients, an L2 (lowest acceptable) swell can be characterized by Equation 3 and an L8 (maximum) swell can be characterized by Equation 4:
V=1.1+5e−2000T+0.1e−3T (EQ 3)
V=1.4+3e−200T+0.3e−12T (EQ 4)
Intermediate levels may be interpolated between the L2 and L8 levels. For example, an L5 curve would be the average of the L2 and L8 curves. In some existing metering systems, a swell event is fitted to a nearest curve so that it can be classified as one of seven levels (L2-L8). Swell events that fall below the L2 curve are categorized as L2 swell events and swell events that fall above the L8 curve are characterized as L8 swell events.
Some existing metering systems provide an integer level rating between 2 and 8 for sag and swell events. However to produce a process risk and capital risk scatter plot like the one shown in
Sag level=m*depth+b
where
m=(8−2)/(VL8sag(T)VL2sag(T)) and
b=2−mVL2sag(T)
For example, to calculate the continuous sag level for a 200 ms sag with a voltage depth at 50% of nominal, Equations 1 and 2 are solved for T=200 ms. The resulting VL2sag and VL8sag are then used to derive a slope of −2.67 and an intercept of 3.69. (see point marked “x” on the plot in
Sag level=−2.67(0.5)+3.69=2.36
To interpolate a continuous level rating for a swell event, the swell event is defined by its depth and duration. In calculating the swell level, if the per-unit voltage for a given duration is above the L8, it is assigned a swell level of 8. If the per-unit voltage for a given duration is below the L2 swell curve, it is assigned a swell level of 1. Otherwise, the continuous swell level is calculated such that:
Swell level=m*height+b
where
m=(8−2)/(VL8swell(T)−VL2swell(T)) and
b=2−mVL2swell(T)
For example, to calculate the continuous swell level for a 0.1 s sag with a voltage of 120% of nominal, Equations 3 and 4 are solved for T=0.1 s. The resulting VL2swell and VL8swell are then used to derive a slope of 22 and an intercept of −22.9. The swell level is then calculated as:
Swell level=22(1.2)−22.9=3.54
The risk assessment tool 220 uses the continuous sag or swell level for a given electrical event to quantify a process risk Rp and capital risk Rc associated with the electrical event. As already discussed above, a process risk is typically short-term and involves the consequences of interruption of processes due to insufficient voltage. In contrast a capital risk is typically a long-term risk that involves accumulated damage that may result in an unsafe working environment as well as repair or replacement of equipment. The quantified process risk and capital risk are communicated by way of the user interface 230. In one embodiment, the quantified process risk and capital risk are communicated by way of the scatter plot 100 shown in
In one embodiment the risk assessment tool 220 (
R
p(y coordinate on the scatter plot 2B)=Continuous Sag Level
R
c(x coordinate)=ln(Rp*Number of Sags at this Level).
Given a swell:
R
c=(Continuous Swell Level*0.27)*ln(Continuous Swell Level*Number of Swells at this Level).
R
p=square root of Rc
It can be seen that the capital risk associated with either a sag or a swell is increased based on a number of sags or swells that have already happened. This captures the incremental accumulation of damage that increases capital risk so that the first electrical event of a given type will result in a lower capital risk than the tenth electrical event of the same type. Process risk may also be augmented based on electrical data that indicates that equipment has shut down due to an electrical event.
In addition to sags and swells, process and capital risk associated with voltage spikes may also be characterized. In one embodiment, a voltage spike is treated as a swell having a 1 ms duration. Thus the continuous swell level would be calculated by: 22*Vpeak/1.414Nrms−23. For an 800 V spike on a 480 V system, the continuous swell level would be calculated as 2.9. Given the continuous swell level, Rp and Rc can be calculated as already described.
In another embodiment, the described methods and/or their equivalents may be implemented with computer executable instructions. Thus, in one embodiment, a non-transitory computer-readable medium is configured with stored computer executable instructions that when executed by a machine (e.g., processor, computer, and so on) cause the machine (and/or associated components) to perform the methods outlined in
In one embodiment, risk assessment tool 530 is a means (e.g., hardware, non-transitory computer-readable medium, firmware) for assessing equipment related risk from electrical event data.
The means may be implemented, for example, as an ASIC programmed to assess equipment related risk from electrical event data. The means may also be implemented as stored computer executable instructions that are presented to computer 500 as data 516 that are temporarily stored in memory 504 and then executed by processor 502.
Generally describing an example configuration of the computer 500, the processor 502 may be a variety of various processors including dual microprocessor and other multi-processor architectures. A memory 504 may include volatile memory and/or non-volatile memory. Non-volatile memory may include, for example, ROM, PROM, and so on. Volatile memory may include, for example, RAM, SRAM, DRAM, and so on.
A disk 506 may be operably connected to the computer 500 via, for example, an input/output interface (e.g., card, device) 518 and an input/output port 510. The disk 506 may be, for example, a magnetic disk drive, a solid state disk drive, a floppy disk drive, a tape drive, a Zip drive, a flash memory card, a memory stick, and so on. Furthermore, the disk 506 may be a CD-ROM drive, a CD-R drive, a CD-RW drive, a DVD ROM, and so on. The memory 504 can store a process 514 and/or a data 516, for example. The disk 506 and/or the memory 504 can store an operating system that controls and allocates resources of the computer 500.
The bus 508 may be a single internal bus interconnect architecture and/or other bus or mesh architectures. While a single bus is illustrated, it is to be appreciated that the computer 500 may communicate with various devices, logics, and peripherals using other busses (e.g., PCIE, 1394, USB, Ethernet). The bus 508 can be types including, for example, a memory bus, a memory controller, a peripheral bus, an external bus, a crossbar switch, and/or a local bus.
The computer 500 may interact with input/output devices via the I/O interfaces 518 and the input/output ports 510. Input/output devices may be, for example, a keyboard, a microphone, a pointing and selection device, cameras, video cards, displays, the disk 506, the network devices 520, and so on. The input/output ports 510 may include, for example, serial ports, parallel ports, and USB ports.
The computer 500 can operate in a network environment and thus may be connected to the network devices 520, including meters gathering electrical event data, via the I/O interfaces 518, and/or the I/O ports 510. Through the network devices 520, the computer 500 may interact with a network. Through the network, the computer 500 may be logically connected to remote computers. Networks with which the computer 500 may interact include, but are not limited to, a LAN, a WAN, and other networks.
While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Therefore, the invention is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims.
To the extent that the term “includes” or “including” is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term “comprising” as that term is interpreted when employed as a transitional word in a claim.
