Patent Application
20080068027
The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings, wherein:
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions, sizing, and/or relative placement of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will also be understood that the terms and expressions used herein have the ordinary meaning as is usually accorded to such terms and expressions by those skilled in the corresponding respective areas of inquiry and study except where other specific meanings have otherwise been set forth herein.
The following description is not to be taken in a limiting sense, but is made merely for the purpose of describing the general principles of the invention. The scope of the invention should be determined with reference to the claims. The present embodiments address the problems described in the background while also addressing other additional problems as will be seen from the following detailed description.
Referring to
One or more surge arrestors are located within the cabinet 100. A facility may include one or more cabinets and thus, one or more surge arrestors. The embodiments described below with reference to
Referring to
The remote computer 200 is coupled to the local computer through any type of network (e.g., the Internet, an Ethernet connection, a local area network, a wireless network, a virtual private network or other type of connection that allows communication between the remote computer 200 and the local computer 202). The local computer 202 is coupled to the electronic measuring device 204 such that data can be transferred from the electronic measuring device to the local computer 202. The electronic measuring device 204 is, for example, a spectrum analyzer, oscilloscope or other device that is capable of measuring voltage and/or current in either the frequency or time domain. The electronic measuring device 204 can also be a part of local computer 202 (e.g., a plug in card). The electronic measuring device 204 is coupled to the computer through, for example, a Universal Serial Bus (USB) connection, an Ethernet connection, an interface in accordance with IEEE 1394 standards, a general purpose interface bus (GPIB) or other known means of communicating data from a spectrum analyzer or oscilloscope to a computer.
The voltage probe 208 and the current probe 210 are coupled to the electronic measuring device 204 through the switching matrix 206. As defined herein, a switching matrix includes one or more physical or logical switches. The switching matrix is controlled by the control circuitry 216. The control circuitry 216 is any combination of hardware, software, and/or firmware and can be implemented as a dedicated fixed-purpose circuit and/or partially or wholly programmable platform. The control circuitry 216 can be implemented as a separate device or can be implemented as a module within either of the local computer 202 or the remote computer 204.
The voltage probe 208 is also coupled between the fuse 212 and the surge arrestor 214. The current probe 210 is coupled to a lead of the surge arrestor 214. Advantageously, in accordance with one embodiment, the current probe 210 is an inductive current probe that is placed around an input wire to the surge arrestor 214. In this manner, the current probe 210 is not physically connected to the surge arrestor 214.
The surge arrestor 214 is, for example, a metal oxide varistor (MOV), a spark gap type arrestor, a diode or Zener technology. Each of these devices has an inherent capacitance and thus, has at least a small total current present at the surge arrestor 214. The current probe 210 is coupled to the surge arrestor 214 and measures the total current in the surge arrestor 214. In general, the capacitance of the surge arrestor 214 is directly related to the health of the surge arrestor 214. Additionally, the capacitance 214 is also related to the total current in the surge arrestor 214. Thus, by measuring the total current with the current probe 210, a determination as to the status or health of the surge arrest 214 can be made. Furthermore, as MOVs age or experience normal system voltage surges, parts of their semi-conductor matrix heat and fuses together. This lowers the breakdown or function voltage of the MOV and increases the total current. Eventually, the breakdown voltage of the MOV lowers significantly to cause a catastrophic avalanche and failure of the MOV. The current probe 210 can be used to monitor the total current and the measured signal can be analyzed to determine a status, failure of the surge arrestor and/or changes in device characteristics with age.
In operation, the current probe 210 measures a total current from the surge arrestor 214. The total current is present due to the charging and discharging of the inherent capacitance of the surge arrestor 214. In accordance with one embodiment, the current probe 210 is an inductive current probe, for example, a 1 V/A current probe (with a sensitivity of 1 V/A at 60 Hz.) The output signal of the current probe 210 is input to the electronic measuring device 204 through the switching matrix 206. The electronic measuring device 204 measures the output signal from the current probe and stores data corresponding to the output signal. As described above, the electronic measuring device 204 is, for example, a spectrum analyzer or an oscilloscope. In one embodiment, a person can inspect the data directly at the electronic measuring device 204 by looking at a time-domain or frequency domain trace of the output signal or by analyzing appropriate waveform metrics (e.g., amplitude). Sample outputs in both the time-domain and frequency domain are shown below with reference to
In one embodiment, either the local computer 202 or the remote computer 200 run an algorithm that analyzes the data from the electronic measuring device 204 and determines if the measured total current is outside of a predetermined range. The predetermined range will change depending upon the power system and the type and size of surge arrestor. If the measured total current is outside of the predetermined range, in one embodiment, an alarm or message is created notifying the proper person that the surge arrestor should be replaced.
The monitoring system optionally also includes the voltage probe 208. The voltage probe 208 will register a voltage so long as the fuse 212 is not blown. The registered voltage will vary depending upon the voltage on the power line. However, if the fuse is blown the voltage probe 208 will register zero volts. When the voltage goes to zero, either a person monitoring the electronic measure device 204, a person monitoring the local computer 202 or the remote computer 200, or an algorithm running on the local computer 202 or the remote computer 200 determines that the fuse 212 has been blown. If the fuse 212 has been blown, there is a possibility that the surge arrestor is damaged and thus, the surge arrestor 214 should be identified as possibly damaged. A physical and electrical inspection of the surge arrestor 214 can then be made. In this manner, the current status of the surge arrestor 214 can be monitored without opening the cabinet in which the surge arrestor 214 is located.
Generally, when a surge arrestor fails, it will fail short and then typically blow open under a phase current. If the surge arrestor 214 remains shorted, fuse 212 will blow. If the surge arrestor 214 fails open, the circuit is unprotected and previously the only way to detect the failure was to inspect the surge arrestor. However, in the present embodiment, when the surge arrestor fails open the current probe 210 will no longer measure a total current and one of the computers, a person monitoring the data on one of the computers, or a person monitoring the electronic measuring device will detect the problem.
The control circuitry 216 controls the operation of the switching matrix 206 and thus controls the input to the electronic measuring device 204. In this manner, both the voltage probe 208 and the current probe 210 can be monitored using a single electronic measuring device 204.
The system shown in
Referring now to
The remote computer 300 is coupled to the local computer 302 which is coupled to the electronic measuring device 304. The local computer 302 is also coupled to the control electronics 318 that control the first switching matrix 306 and the second switching matrix 308. The first switching matrix 306 is coupled to the second switching matrix 308 through the first data line 320. The plurality of voltage probes 310 and the plurality of current probes 312 are coupled to the electronic measuring device 304 through the first switching matrix 306 and the second switching matrix 308.
In one embodiment, the second switching matrix 308, the plurality of voltage probes 310, the plurality of current probes 312, the plurality of fuses 314, and the plurality of surge arrestors 316 are located within a cabinet (such as the cabinet shown in
In one embodiment, the local computer 302 is connected to the electronic measuring device 304, for example, through a USB interface. As before, the electronic measurement device 304 can be integrated into the local computer 302. Data, corresponding to the signal being measured, is sent from the electronic measuring device 304 to the local computer 302. The local 302 computer is coupled to the control electronics 318 and thus is able to associate the data from the electronic measuring device 304 with a specific one of the plurality of surge arrestors 316. The local computer 302 can use the data to determine if the surge arrestor is operating within an acceptable predetermined range or a person looking at the data can determine if the surge arrestor is operating within an acceptable predetermined range. In one embodiment, a person can directly look at the electronic measuring device 304 and/or appropriate waveform metrics to determine if the surge arrestor is operating within the acceptable predetermined range.
In yet another embodiment, the data from the local computer 302 is sent to the remote computer 300 for analysis. In this embodiment, the remote computer 300 can also be connected to many different facilities and many different local computers 302. This allows multiple facilities each having one or more surge arrestors to all be monitor at one remote computer 300. Advantageously, this greatly reduces the need to have many employees visually inspecting surge arrestors at many different facilities. Additionally, as described above with reference to
In an alternative embodiment, the electronic measuring device 304 is capable of directly connecting to a network, for example, using an Ethernet connection. In this embodiment, the local computer 302 can be removed from the system and the electronic measuring device 304 can send data corresponding to the signal from the probes directly to the remote computer 300.
Referring to
If the total current decreases in amplitude, this indicates a reduction in the capacitance of the surge arrestor and indicates that the surge arrestor is starting to fail. If the current goes to zero Amps, the surge arrestor has failed and need to be changed. If the surge arrestor is being over voltaged or is starting to draw a base current, the current will start to increase. An increase in the current also indicates that the surge arrestor may fail. Thus, by monitoring the total current, a status of the surge arrestor can be determined.
Referring to
While the invention herein disclosed has been described by means of specific embodiments and applications thereof, other modifications, variations, and arrangements of the present invention may be made in accordance with the above teachings other than as specifically described to practice the invention within the spirit and scope defined by the following claims.
