Patent Publication Number: US-11391476-B2

Title: Method of identifying burning by monitoring water level and combustion analytes

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application No. 62/702,228, filed on Jul. 23, 2018, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention is directed generally to methods of determining that burning is occurring inside a manhole vault system and locating the source of the burning. 
     Description of the Related Art 
     In recent years, the importance of monitoring underground vaults (e.g., manhole vaults) for the purposes of avoiding manhole events has been recognized. Manhole events include both minor incidents (such as smoke or small fires) and/or major events (such as sustained fires and explosions). Devices have been described to monitor the conditions inside a manhole vault. For example, U.S. patent application Ser. No. 15/476,775, filed on Mar. 31, 2017, and titled SMART SYSTEM FOR MANHOLE EVENT SUPPRESSION SYSTEM describes a data logger. 
     Devices configured to monitor the conditions inside a manhole vault include at least one sensor together with the hardware and software configured to operate the sensor(s). Non-limiting examples of the sensor(s) include one or more of the following: a pressure sensor, a temperature sensor, a humidity sensor, a visible light camera, an infra-red camera, a motion sensor, a liquid water level sensor, a particulate sensor, a smoke sensor or detector, and a chemical concentration sensor. Chemical concentration sensors may be configured to detect one or more of the following: O 2 , CO 2 , CO, VOCs (volatile organic compounds), NO, NO 2 , O 3 , and H 2 S. For many conditions and events of interest to vault owners, more than a single sensor provides complimentary results. For example, a VOC concentration sensor, an O 2  concentration sensor, a CO 2  concentration sensor, a humidity sensor, and a temperature sensor may be considered complimentary sensors when used to detect oxidative decomposition of methane because oxidative decomposition of methane reduces the presence of VOCs (methane is a VOC) and O 2 , while increasing the concentration of both water (humidity) and CO 2 , and increasing temperature. Thus, these five sensors are complimentary sensors in the detection of oxidative decomposition of methane. 
     The chemistry of fires in manholes is described in some detail in G. Bertini, “Manhole Explosion and Its Root Causes,” IEEE Electrical Insulation Magazine, V. 35, No. 1, January/February 2019, which is incorporated herein by reference in its entirety. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is an illustration of a simplified network of underground vaults and underground connections. 
         FIG. 2  is a graph illustrating 48 hours of sensor readings collected on Jul. 3, 2018, and Jul. 4, 2018, at an underground vault that is in hydraulic communication with the Atlantic Ocean and is located in a city on the East Coast of the U.S. 
         FIG. 3  is a flow diagram of a method that may be performed by a system controller. 
         FIG. 4  is a diagram of hardware and an operating environment in conjunction with which implementations of the system controller may be practiced. 
     
    
    
     Like reference numerals have been used in the figures to identify like components. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a simplified network  200  of underground vaults  208  and underground connections  210 . The network  200  includes at least one monitor  212  and a system controller  230 . 
     In  FIG. 1 , the vaults  208  include nine vaults A- 1  to A- 2 , B- 1  to B- 3 , and C- 1  to C- 3 . One or more of the vaults  208  may house electrical equipment and/or electrical cables. Each of the vaults  208  may be characterized as being a node. Thus,  FIG. 1  shows a simple nine-node network with two external connections Ext  01  and Ext  02 . The external connection Ext  01  is connected to the vault B- 3  and the external connection Ext  02  is connected to the vault C- 2 . 
     Optionally, one or more of the vaults  208  may include a manhole event suppression system  240 , which may be implemented in accordance with any of the ventilation systems described in U.S. patent application Ser. No. 15/084,321 filed on Mar. 29, 2016, and titled “VENTILATION SYSTEM FOR MANHOLE VAULT,” U.S. patent application Ser. No. 15/173,633, filed on Jun. 4, 2016, titled “SYSTEMS FOR CIRCULATING AIR INSIDE A MANHOLE VAULT,” or U.S. patent application Ser. No. 15/476,775, filed on Mar. 31, 2017, and titled “SMART SYSTEM FOR MANHOLE EVENT SUPPRESSION SYSTEM.” All of three of the aforementioned applications are incorporated herein by reference in their entireties. The manhole event suppression system  240  may blow air from an external atmosphere outside the vault into an internal atmosphere inside the vault and/or from the internal atmosphere into the external atmosphere. Such air exchange may be referred to as ventilation. 
     The present application also incorporates herein by reference the following applications in their entireties: 
     U.S. patent application Ser. No. 16/162,260, filed on Oct. 16, 2018, titled “CALIBRATIONLESS OPERATION METHOD;” 
     U.S. patent application Ser. No. 16/189,639, filed on Nov. 13, 2018, titled “METHODS OF USING COMPONENT MASS BALANCE TO EVALUATE MANHOLE EVENTS;” 
     U.S. patent application Ser. No. 16/190,832, filed on Nov. 14, 2018, titled “METHODS OF USING COMPONENT MASS BALANCE TO EVALUATE MANHOLE EVENTS;” 
     U.S. patent application Ser. No. 16/207,633, filed on Dec. 3, 2018, titled “METHODS OF USING DILUTION OF A FIRST TYPE TO CALIBRATE ONE OR MORE SENSORS;” 
     U.S. patent application Ser. No. 16/208,098, filed on Dec. 3, 2018, titled “METHODS AND SYSTEMS FOR DETECTING MANHOLE EVENTS;” 
     U.S. patent application Ser. No. 16/208,120, filed on Dec. 3, 2018, titled “FLOW RESTRICTOR FOR INSTALLATION IN AN UNDERGROUND CONDUIT CONNECTED TO AN UNDERGROUND VAULT;” 
     U.S. patent application Ser. No. 16/219,137, filed on Dec. 13, 2018, titled “METHODS OF USING DILUTION OF A SECOND TYPE TO CALIBRATE ONE OR MORE SENSORS;” and 
     U.S. patent application Ser. No. 16/234,246, filed on Dec. 27, 2018, titled “METHODS OF USING TRIANGULATION TO LOCATE A MANHOLE EVENT IN A SYSTEM OF UNDERGROUND VAULTS.” 
     In the embodiment illustrated, the connections  210  include connections AA 12 , AA 23 , BB 12 , BB 23   a , BB 23   b , CC 12 , CC 23 , AB 11 , AB 22   a , AB 22   b , AB 33 , BC 11 , BC 22   a , BC 22   b , and BC 33 . Each of the connections  210  connects a pair of the vaults  208  together. For example, the connection AA 12  connects the pair of vaults A- 1  and A- 2  together. Each of the connections  210  may be implemented as conduit, duct, or pipe. Some of the connections  210  include at least one cable that extends therethrough. If a connection includes one or more cables, a gap may be defined between the cable(s) and the connection. Such a gap provides fluidic communication between the connected vaults. Thus, a fluidic flow may be present between the connected vaults. In some cases, a technique referred to as duct plugging, which involves installing a plug between the cable(s) and the connection, may be used to limit such fluidic flow. Unfortunately, all such duct plugs are likely to leak after aging and especially if a fire (oxidative decomposition, pyrolysis, and/or plasmatization) occurs and creates a positive pressure in the gap defined between the cable(s) and the connection. Thus, generally speaking, the connections  210  allow at least some communication between the vaults  208 . 
     For ease of illustration,  FIG. 1  omits connections (e.g., conduits) between building(s) owned by the vault owner&#39;s customers and one or more of the vaults  208  and/or the connections  210 . These connections provide electrical and fluidic communication with one or more adjacent buildings that may serve as pathways for dangerous gases to enter customer premises. Additionally, these connections may provide additional sources of undesirable gases inside the network  200 . 
     The at least one monitor  212  has been illustrated as monitors  212 A- 212 I positioned inside the vaults A- 1  to A- 2 , B- 1  to B- 3 , and C- 1  to C- 3 , respectively. However, this is not a requirement. The network  200  may include any number of monitors each like the monitors  212 A- 212 I installed in any of the vaults  208  and/or the connections  210 . Each of the monitors  212 A- 212 I includes a water level sensor  214  and at least one fire detection sensor  216  together with hardware and software configured to operate the sensors  214  and  216 . 
     The system controller  230  communicates over wireless or wired connections with the monitors  212 A- 212 I. The monitors  212 A- 212 I are each configured to send sensor data captured by the sensors  214  and  216  to the system controller  230 . By way of a non-limiting example, the system controller  230  may be implemented as a computing device  12  illustrated in  FIG. 4  and described below. 
     Monitoring conditions inside the network  200  (e.g., using the monitors  212 A- 212 I) provides data that may be used by the system controller  230  to answer the following three critical questions:
         1. Are flammable gases present inside a vault and/or connection that could contribute to a fire or explosion?   2. Are gases present inside a vault and/or connection that indicate a fire (oxidative decomposition, pyrolysis, and/or plasmatization) is occurring?   3. If the answer to at least one of the first and second critical questions is “YES,” from where precisely are the gases emanating?       

     When the answer to at least one of the first and second critical questions is “YES,” the system controller  230  may alert the operator of the network  200 . The utility of being alerted when the answer to at least one of the first and second critical questions is “YES,” is obvious. The utility of the answer to the third critical question is not as obvious, particularly to those individuals who do not operate networks like the network  200 . When the answer to at least one of the first and second critical questions is “YES,” it is necessary for the system owner to find and repair the issue. The very first step is to cut electrical power to the offending circuit as that electrical energy contributes to the fire, provides additional sources of ignition, and is potentially hazardous to maintenance personnel. Extinguishing a fire, if one exists, is the very next step. Clearing smoke and flammable vapors is next on the responder&#39;s agenda. Smoke, flammable gases, and toxic gases may leak from the circuit owner&#39;s vaults to connected customer facilities. Furthermore, the circuit owner&#39;s customers are inconvenienced by a power outage while troubleshooting proceeds. Hence, it is most preferable to pinpoint the specific conduit that is causing the problem or at least to eliminate some of the circuits and conduits which can be ignored. Reducing the required troubleshooting time minimizes and mitigates all of the costs, dangers, and inconveniences outlined above. 
       FIG. 1  illustrates a fire  220  (oxidative decomposition, pyrolysis, and/or plasmatization) in the connection BC 22   b  connecting the vaults B- 2  and C- 2 . Thus, the fire  220  is producing gases or particulates (e.g., CO, CO 2 , carbon agglomerates) that are detectable by the fire detection sensor(s)  216  of the monitor  212 E. When fire detection sensor(s)  216  indicates a fire (oxidative decomposition, pyrolysis, and/or plasmatization) has been detected, identifying the location of the fire is required before safe operations can resume. The fire detection sensor(s)  216  may include a temperature sensor, a humidity sensor, a visible light camera, an infra-red camera, a motion sensor, a particulate sensor, a smoke sensor or detector, and chemical concentration sensor(s). Examples of chemical concentration sensors that may be used to implement one or more of the fire detection sensor(s)  216  include sensors configured to detect O 2 , CO 2 , CO, VOCs, NO, NO 2 , and O 3 . By way of non-limiting examples, the fire detection sensor(s)  216  may detect one or more of the following conditions, which indicate a corresponding fire specified in parenthesis:
         i. CO 2  is elevated (oxidative decomposition);   ii. CO is elevated (pyrolysis);   iii. VOCs are elevated (pyrolysis);   iv. NO is elevated (evidence of plasma/electrical discharge);   v. NO 2  is elevated (evidence of plasma/electrical discharge);   vi. O 3  is elevated (evidence of plasma/electrical discharge);   vii. H 2 O (absolute humidity) is elevated (oxidative decomposition);   viii. O 2  is depressed (dilution by i-vii, and consumption by oxidative decomposition and partial pyrolysis);   ix. Temperature is elevated (oxidative decomposition);   x. Particulates are elevated (any or all oxidative decomposition, pyrolysis, plasma/electrical discharge); and   xi. Smoke is observed in visual or infra-red wavelengths by pattern recognition algorithms or by motion detection (any or all oxidative decomposition, pyrolysis, plasma/electrical discharge).       

     As mentioned above,  FIG. 1  illustrates the fire  220  in the connection BC 22   b  connecting the vaults B- 2  and C- 2 . Thus, monitors (like the monitors  212 E and  212 H) in the vaults B- 2  and/or C- 2  may be used to detect the fire  220 . For ease of illustration, the monitor  212 E inside the vault B- 2  will be described as having detected the fire  220 . In this example, the fire detection sensor(s)  216  will be described as being implemented as chemical or gas concentration sensors. Such gas concentration sensors can utilize a variety of physical or chemical technologies, such as infra-red absorbance, florescence quenching, electro-chemical, thermal-conductivity, and/or flame ionization. Gases to be tested for the presence of at least one analyte are conveyed to the sensor(s) passively (e.g., via diffusion and/or natural convection) or by active ventilation. Unfortunately, using prior art methods, this means that each of the connections  210  that is connected to the vault B- 2  must be tested to determine from where precisely the detected gases (generated by the fire  220 ) are emanating. In other words, to answer the third critical question using prior art methods, the gases emanating from each of the connections AB 22   a , AB 22   b , BB 12 , BC 22   a , BC 22   b , BB 23   a  and BB 23   b  must be tested separately by individual fire detection sensor(s) each like the fire detection sensor(s)  216 . 
       FIG. 3  is a flow diagram of a method  400  that may be performed by the system controller  230  (see  FIG. 1 ) and used to at least partially answer the third critical question (e.g., without using the individual fire detection sensor(s) mentioned above). The method  400  may be used to address the third Critical Question where the vaults  208  (see  FIG. 1 ) are in hydraulic communication with ocean tides. For ease of illustration,  FIG. 1  omits a third dimension, height above sea level that is critically important because many of the vaults  208  and/or the connections  210  lay at different elevations. Thus, different cables and/or electrical equipment positioned inside the connections  210  and/or vaults  208  are submerged (or not submerged) at different times during a tidal cycle. Fires do not occur under water. Thus, if a connection or vault is submerged under water, gases produced by a fire cannot emanate from that connection or vault. Additionally, when the water inside a connection or vault rises to a level sufficient to extinguish a fire, referred to as an Extinguish Level  300  (see  FIG. 2 ), gases produced by a fire cannot emanate from that connection or vault. 
       FIG. 2  is a graph illustrating 48 hours of sensor readings collected on Jul. 3, 2018, and Jul. 4, 2018, at an underground vault that is in hydraulic communication with the Atlantic Ocean and is located in a city on the East Coast of the U.S. In  FIG. 2 , a line  310  illustrates a water level inside the underground vault, a line  312  illustrates a CO 2  concentration level, and triangles  314  illustrate an O 2  concentration level.  FIG. 2  illustrates four related Events  16   a - 16   d  during which CO 2  and O 2  sensors detected gas concentration levels indicative of a fire (e.g., the triangles  314  show the O 2  concentration level is decreasing and the line  312  shows the CO 2  concentration level is increasing at the start event horizon depicted by a vertical line  304  and decreasing as the event extinguishes at the end event horizon depicted by a vertical line  305 ). In other words,  FIG. 2  illustrates separate Events  16   a - 16   d , during which the fire detection sensor(s)  216  detected a fire (e.g., the fire  220  illustrated in  FIG. 1 ). In  FIG. 2 , an X-axis is time (24 hours from Jul. 3, 2018 to midnight Jul. 4, 2018), a left hand Y-axis is both parts per million (“ppm”) of Analyte (e.g., CO 2 ) and water level measured in millimeters multiplied by 10, and a right hand Y-axis is oxygen concentration expressed as a volume percentage of air. 
     As mentioned above, each of the Events  16   a - 16   d  includes a start event horizon (depicted by the vertical line  304 ), an end event horizon (depicted by the vertical line  305 ), and a sensor baseline for each of the fire detection sensor(s)  216 . In the example illustrated, each of the Events  16   a - 16   d  includes a CO 2  sensor baseline (depicted by a horizontal line  306 ) and an O 2  sensor baseline (depicted by a horizontal line  307 ). Referring to  FIG. 2 , the Events  16   a - 16   d  are delineated with boxes formed by their respective start event horizon, end event horizon, CO 2  sensor baseline, and O 2  sensor baseline. The start event horizon (depicted by the vertical line  304 ) of each of the Events  16   a - 16   d  is defined as a moment or time that the system controller  230  (see  FIG. 1 ) determined that a fire had begun. The end event horizon (depicted by the vertical line  305 ) of each of the Events  16   a - 16   d  is defined as a moment or time that the System Controller  230  (see  FIG. 1 ) determined the fire had been extinguished. 
     In  FIG. 2 , the CO 2  sensor baseline (depicted by the horizontal line  306 ) is a baseline carbon dioxide concentration value detected for each of the Events  16   a - 16   d  prior to the event commencement. In the example illustrated, the CO 2  sensor baseline of the Event  16   a  is about 1000 ppm. The O 2  sensor baseline (depicted by the horizontal line  307 ) is a baseline oxygen concentration value detected for each of the Events  16   a - 16   d . In the example illustrated, the O 2  sensor baseline of the Event  16   a  is about 20.6% [right Y-axis]. While  FIG. 2  shows two sensor baselines, there can be any number of sensor baselines, each depicted by a horizontal line and for a different one of the fire detection sensor(s)  216  that is deployed and is perturbed by the event. 
       FIG. 2  demonstrates how the water level sensor  214  (see  FIG. 1 ) and the fire detection sensor(s)  216  (see  FIG. 1 ) may be utilized to find the Extinguish Level  300  at a particular location (e.g., the vault B- 2  illustrated in  FIG. 1 ) within the network  200  (see  FIG. 1 ). As mentioned above, in this example, the fire detection sensor(s)  216  have been implemented as gas concentration sensors. Specifically, in this example, the fire detection sensor(s)  216  are implemented as a CO 2  sensor and an O 2  sensor. 
     The Extinguish Level  300  is utilized to rule out locations within the network  200  that were submerged prior to the Extinguish Level  300  being reached by the rising tide. Referring to  FIG. 1 , the locations may include one or more of the vaults  208  and/or one or more of the connections  210  as well as electrical equipment housed therein. As is apparent from  FIG. 2 , locations that are submerged below the Extinguish Level  300  can be excluded from consideration as a gas source. Also, any potential fire sources (e.g., a cable, equipment, and the like) positioned above the Extinguish Level  300  can also be excluded from consideration as a gas source because if the fire was above the Extinguish Level  300 , the fire would likely continue to burn. However, this did not occur in  FIG. 2 . While it is possible that a fire may self-extinguish and hence a single crossing of the Extinguish Level  300  is not proof positive that the fire lies near the Extinguish Level  300 , the multiple crossings of the Extinguish Level  300  illustrated in  FIG. 2  confirm that the fire is near the Extinguish Level  300 . 
     For example, the Event  16   a  begins after the line  310  (water level) drops below about 1220 mm and is extinguished when the tide returns the line  310  (water level) to at least 1220 mm. Event  16   b  begins after the line  310  (water level) drops below about 1220 mm, and self-extinguishes about three hours later while the line  310  (water level) is still below 1220 mm. The fire rekindles about two hours later as the Event  16   c , and is again quenched when the tide rises (as shown by the line  310 , which is the water level) above about 1220 mm. Shortly after the tide recedes and the line  310  (water level) falls below 1220 mm, at about 06:30 on Jul. 4, 2018, the fire reignites and thus begins the Event  16   d . The Event  16   d  self-extinguishes at about 09:30 on Jul. 4, 2018. In other words, the Event  16   a  extinguishes at 1220 mm, the Event  16   b  reignites at 1220 mm, the Event  16   c  extinguishes at 1220 mm, and the Event  16   d  reignites at 1220 mm. These four milestones taken together provide ample assurance that the fire that caused Events  16   a - 16   d  is positioned at about 1220 mm and all ducts and equipment below that level are not harboring the fire and all ducts and equipment above that level are unlikely to be harboring the fire. In other words, this information may be used to pinpoint the elevation of the fire. 
     Thus, using the information of  FIG. 2 , the monitor  212 E and/or the system controller  230  may determine that the Extinguish Level  300  is about 1220 mm. Specifically, by noticing that the indicia of a fire repeatedly disappeared after the line  310  (water level) exceeded about 1220 mm and that the fire reignited when the line  310  (water level) was below 1220 mm, the monitor  212 E and/or the system controller  230  may conclude that the Extinguish Level  300  is about 1220 mm for that location. This process may be repeated for different locations within the network  200  (see  FIG. 1 ) and used to determine the Extinguish Level  300  for each location (e.g., each of the vaults  208 ). 
     As mentioned above,  FIG. 3  illustrates the method  400 , which may be performed by the system controller  230  (see  FIG. 1 ) and used to at least partially answer the third critical question when the vaults  208  (see  FIG. 1 ) are in hydraulic communication with ocean tides. Referring to  FIG. 3 , in first block  410 , the system controller  230  (see  FIG. 1 ) receives sensor data from the monitor  212 E (see  FIG. 1 ) installed in the vault B- 2  (see  FIG. 1 ). In next block  420 , the system controller  230  (see  FIG. 1 ) determines the sensor data indicates that the fire  220  (see  FIG. 1 ) is in progress somewhere within the network  200  (see  FIG. 1 ). In other words, the system controller  230  (see  FIG. 1 ) detects a new start event horizon of a new event. In block  430 , the system controller  230  identifies potential combustion locations connected to the vault B- 2  (see  FIG. 1 ). For example, in block  430 , the system controller  230  may identify the vaults A- 2 , B- 1 , B- 3 , and C- 2  as well as the connections AB 22   a , AB 22   b , BB 12 , BB 23   a , BB 23   b , BC 22   a , and BC 22   b.    
     In block  440 , the system controller  230  obtains a probability assigned to each of the potential combustion locations associated with the current water level in the vault B- 2  (see  FIG. 1 ). These probabilities may be used to exclude at least some of the locations from the potential combustion locations. 
     The probability assigned to each of the potential combustion locations is obtained by analyzing past events detected in the vault B- 2  (see  FIG. 1 ). By way of a non-limiting example, the system controller  230  (see  FIG. 1 ) may receive current water level data from the water level sensor  214  positioned within the vault B- 2  (see  FIG. 1 ) and compare the current water level data to the previously ascertained and recorded actual vertical positions of any potential fire sources (e.g., cables, components, equipment, and the like) within the potential combustion locations. Those potential fire sources located underwater before the new start event horizon may be assigned zero probability by the system controller  230 . By way of another non-limiting example, the system controller  230  may assign a zero probability to each potential fire source known to be underwater at the current time based on the tidal cycle. In other words, the system controller  230  may be configured to determine a tidal water level from the tidal cycle. Furthermore, when the current water level is at the Extinguish Level  300 , those potential fire sources positioned above the Extinguish Level  300  (e.g., dry equipment) are less likely to be the location of the fire than potential fire sources positioned near the Extinguish Level  300  (see  FIG. 2 ). The likelihood that dry equipment is involved in the new event decreases with each past event horizon that occurred at about the same extinguish level. 
     Both an actual vertical position of equipment and an actual water level are subject to measurement error. An estimate of anticipated deviations of these measurements using statistical methods well known in the art are made to compute probabilities that a measured vertical position likely correlates with an actual vertical position. For example, the system controller  230  may calculate a first anticipated deviation between a measurement of the current water level and a measurement of a vertical location of a potential fire source (e.g., equipment). Then, the system controller  230  may determine the measurements are the same when the measurement of the vertical location is within the first anticipated deviation of the measurement of the current water level. In other words, how close the measured vertical position of the potential fire source (e.g., equipment) must be to the measured current water level to be considered the same value may be determined as a non-determinate, probability-based value. As a non-limiting example, the measurement errors may be assumed to be represented by a normal distribution and the anticipated deviation may be represented by a standard deviation. Historical measurements can be utilized to refine anticipated deviations. When the errors are implemented as standard deviations, the standard deviations may be combined to form the first anticipated deviation. For example, the system controller  230  may calculate the first anticipated deviation by combining a standard deviation of measurement errors obtained from measuring the current water level with a standard deviation of measurement errors obtained from measuring the vertical location of the potential fire source. 
     Similarly, the system controller  230  may determine whether the current water level is at one or more of a plurality of extinguish levels. For example, the system controller  230  may calculate a second anticipated deviation between a measurement of the current water level and a measurement of an extinguishing water level. Then, the system controller  230  may determine the measurements are the same when the measurement of the current water level is within the second anticipated deviation of the measurement of the extinguishing water level. In other words, how close the measured current water level must be to the measured extinguishing water level to be considered the same value may be determined as a non-determinate, probability-based value. As a non-limiting example, the measurement errors may be assumed to be represented by a normal distribution and the anticipated deviation may be represented by a standard deviation. Historical measurements can be utilized to refine anticipated deviations. When the errors are implemented as standard deviations, the standard deviations may be combined to form the second anticipated deviation. For example, the system controller  230  may calculate the second anticipated deviation by combining a standard deviation of measurement errors obtained from measuring the current water level with a standard deviation of measurement errors obtained from measuring the extinguishing water level. 
     As explained above, the system controller  230  determines the Extinguish Level  300  for the vault B- 2  based on past events. The system controller  230  also uses statistical methods well known in the art to assign each of the potential combustion locations a probability that a potential fire source inside the potential combustion location is the actual source of the fire. Those potential combustion locations closest to the Extinguish Level  300  have the highest probabilities, potential combustion locations well below the Extinguish Level  300  are ruled out, and those potential combustion locations positioned above the Extinguish Level  300  have lower probabilities based on a number of times the potential combustion location was above the Extinguish Level  300  during start and end event horizons. To illustrate the calculation of these probabilities, consider three simple scenarios involving first, second, third, and fourth conduits positioned at 111 mm, 222 mm, 333 mm, and 444 mm, respectively. 
     Scenario 1: A single historical record of an event detected at a vault that was extinguished by a tidal rise to 150 mm, which is between the first and second conduits. Thus, the system controller  230  may conclude that any potential fire sources below 150 mm, such as the first conduit, could not have been the source of that fire. However, the system controller  230  is not able to draw any conclusions with respect to the second, third, or fourth conduits. Thus, the system controller  230  assigns probabilities to the first, second, third, and fourth conduits of 0%, 33.3%, 33.3%, and 33.3%, respectively. These probabilities may be used by the system controller  230  when the system controller  230  detects a next fire at the vault and the water level in the vault is about 150 mm. 
     Scenario 2: A single historical record of an event detected at the vault that was extinguished by a tidal rise to 220 mm, which is just below the second conduit. Thus, the system controller  230  may conclude that the first conduit could not have been the source of that fire. Further, because the fire extinguished very near the second conduit, the second conduit is most likely to be the fire source. Because the third and fourth conduits are above the water, they are less likely to have been the fire source but cannot be ruled out. Thus, the system controller  230  assigns probabilities to the first, second, third, and fourth conduits of 0%, about 80%, about 10%, and about 10% respectively. These probabilities may be used by the system controller  230  when the system controller  230  detects a next fire at the vault and the water level in the vault is about 220 mm. 
     Scenario 3: Four historical records of events detected at the vault that were extinguished by a tidal rise to 220 mm and two historical records of events detected at the vault that re-ignited after a tidal decrease to just below 220 mm. This scenario demonstrates that the fire source is very likely located around 220 mm and is therefore most likely within the second conduit. However, the third and fourth conduits cannot be ruled out. Thus, the system controller  230  assigns probabilities to the first, second, third, and fourth conduits of 0%, about 98%, about 1%, and about 1% respectively. These probabilities may be used by the system controller  230  when the system controller  230  detects a next fire at the vault and the water level in the vault is about 220 mm. 
     As demonstrated above, the system controller  230  assigns probabilities to each of the conduits that are informed by past experience and the probability model is adjusted to comport with post mortem examinations of actual fire events. Thus, as more events are observed, the probabilities are adjusted and become more robust with experience. 
     In block  450 , the system controller  230  displays the probability assigned to each of the potential combustion location(s). The network operator may take actions (e.g., conduct further investigation) with respect to each of the potential combustion location(s) based on the probability assigned to the location. For example, the network operator may cut electrical power to the potential combustion location(s). Then, the network operator may extinguish the fire  220  (see  FIG. 1 ), if one is found to exist. Next, the network operator may clear smoke and flammable vapors from those locations that are affected. For example, the system controller  230  and/or the network operator may instruct the manhole event suppression system  240  to ventilate the vault B- 2 . 
     Because the method  400  excludes those portions of the network  200  (see  FIG. 1 ) where the fire cannot be located, the method  400  reduces troubleshooting time, cost, danger, and inconvenience. 
     Computing Device 
       FIG. 4  is a diagram of hardware and an operating environment in conjunction with which implementations of the system controller  230  (see  FIG. 1 ) may be practiced. The description of  FIG. 4  is intended to provide a brief, general description of suitable computer hardware and a suitable computing environment in which implementations may be practiced. Although not required, implementations are described in the general context of computer-executable instructions, such as program modules, being executed by a computer, such as a personal computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform particular tasks or implement particular abstract data types. 
     Moreover, those of ordinary skill in the art will appreciate that implementations may be practiced with other computer system configurations, including hand-held devices, multiprocessor systems, microprocessor-based or programmable consumer electronics, network PCs, minicomputers, mainframe computers, and the like. Implementations may also be practiced in distributed computing environments (e.g., cloud computing platforms) where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. 
     The exemplary hardware and operating environment of  FIG. 4  includes a general-purpose computing device in the form of the computing device  12 . By way of non-limiting examples, the computing device  12  may be implemented as a laptop computer, a tablet computer, a web enabled television, a personal digital assistant, a game console, a smartphone, a mobile computing device, a cellular telephone, a desktop personal computer, and the like. 
     The computing device  12  includes a system memory  22 , the processing unit  21 , and a system bus  23  that operatively couples various system components, including the system memory  22 , to the processing unit  21 . There may be only one or there may be more than one processing unit  21 , such that the processor of computing device  12  includes a single central-processing unit (“CPU”), or a plurality of processing units, commonly referred to as a parallel processing environment. When multiple processing units are used, the processing units may be heterogeneous. By way of a non-limiting example, such a heterogeneous processing environment may include a conventional CPU, a conventional graphics processing unit (“GPU”), a floating-point unit (“FPU”), combinations thereof, and the like. 
     The computing device  12  may be a conventional computer, a distributed computer, or any other type of computer. 
     The system bus  23  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory  22  may also be referred to as simply the memory, and includes read only memory (ROM)  24  and random access memory (RAM)  25 . A basic input/output system (BIOS)  26 , containing the basic routines that help to transfer information between elements within the computing device  12 , such as during start-up, is stored in ROM  24 . The computing device  12  further includes a hard disk drive  27  for reading from and writing to a hard disk, not shown, a magnetic disk drive  28  for reading from or writing to a removable magnetic disk  29 , and an optical disk drive  30  for reading from or writing to a removable optical disk  31  such as a CD ROM, DVD, or other optical media. 
     The hard disk drive  27 , magnetic disk drive  28 , and optical disk drive  30  are connected to the system bus  23  by a hard disk drive interface  32 , a magnetic disk drive interface  33 , and an optical disk drive interface  34 , respectively. The drives and their associated computer-readable media provide nonvolatile storage of computer-readable instructions, data structures, program modules, and other data for the computing device  12 . It should be appreciated by those of ordinary skill in the art that any type of computer-readable media which can store data that is accessible by a computer, such as magnetic cassettes, flash memory cards, solid state memory devices (“SSD”), USB drives, digital video disks, Bernoulli cartridges, random access memories (RAMs), read only memories (ROMs), and the like, may be used in the exemplary operating environment. As is apparent to those of ordinary skill in the art, the hard disk drive  27  and other forms of computer-readable media (e.g., the removable magnetic disk  29 , the removable optical disk  31 , flash memory cards, SSD, USB drives, and the like) accessible by the processing unit  21  may be considered components of the system memory  22 . 
     A number of program modules may be stored on the hard disk drive  27 , magnetic disk  29 , optical disk  31 , ROM  24 , or RAM  25 , including the operating system  35 , one or more application programs  36 , other program modules  37 , and program data  38 . A user may enter commands and information into the computing device  12  through input devices such as a keyboard  40  and pointing device  42 . Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, touch sensitive devices (e.g., a stylus or touch pad), video camera, depth camera, or the like. These and other input devices are often connected to the processing unit  21  through a serial port interface  46  that is coupled to the system bus  23 , but may be connected by other interfaces, such as a parallel port, game port, a universal serial bus (USB), or a wireless interface (e.g., a Bluetooth interface). A monitor  47  or other type of display device is also connected to the system bus  23  via an interface, such as a video adapter  48 . In addition to the monitor, computers typically include other peripheral output devices (not shown), such as speakers, printers, and haptic devices that provide tactile and/or other types of physical feedback (e.g., a force feedback game controller). 
     The input devices described above are operable to receive user input and selections. Together the input and display devices may be described as providing a user interface. 
     The computing device  12  may operate in a networked environment using logical connections to one or more remote computers, such as remote computer  49 . These logical connections are achieved by a communication device coupled to or a part of the computing device  12  (as the local computer). Implementations are not limited to a particular type of communications device. The remote computer  49  may be another computer, a server, a router, a network PC, a client, a memory storage device, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computing device  12 . The remote computer  49  may be connected to a memory storage device  50 . The logical connections depicted in  FIG. 4  include a local-area network (LAN)  51  and a wide-area network (WAN)  52 . Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     Those of ordinary skill in the art will appreciate that a LAN may be connected to a WAN via a modem using a carrier signal over a telephone network, cable network, cellular network, or power lines. Such a modem may be connected to the computing device  12  by a network interface (e.g., a serial or other type of port). Further, many laptop computers may connect to a network via a cellular data modem. 
     When used in a LAN-networking environment, the computing device  12  is connected to the local area network  51  through a network interface or adapter  53 , which is one type of communications device. When used in a WAN-networking environment, the computing device  12  typically includes a modem  54 , a type of communications device, or any other type of communications device for establishing communications over the wide area network  52 , such as the Internet. The modem  54 , which may be internal or external, is connected to the system bus  23  via the serial port interface  46 . In a networked environment, program modules depicted relative to the personal computing device  12 , or portions thereof, may be stored in the remote computer  49  and/or the remote memory storage device  50 . It is appreciated that the network connections shown are exemplary and other means of and communications devices for establishing a communications link between the computers may be used. 
     The computing device  12  and related components have been presented herein by way of particular example and also by abstraction in order to facilitate a high-level view of the concepts disclosed. The actual technical design and implementation may vary based on particular implementation while maintaining the overall nature of the concepts disclosed. 
     In some embodiments, the system memory  22  stores computer executable instructions that when executed by one or more processors cause the one or more processors to perform all or portions of one or more of the methods (including the method  400  illustrated in  FIG. 3 ) described above. Such instructions may be stored on one or more non-transitory computer-readable media. 
     The foregoing described embodiments depict different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality. 
     While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this invention and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this invention. Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). 
     Conjunctive language, such as phrases of the form “at least one of A, B, and C,” or “at least one of A, B and C,” (i.e., the same phrase with or without the Oxford comma) unless specifically stated otherwise or otherwise clearly contradicted by context, is otherwise understood with the context as used in general to present that an item, term, etc., may be either A or B or C, any nonempty subset of the set of A and B and C, or any set not contradicted by context or otherwise excluded that contains at least one A, at least one B, or at least one C. For instance, in the illustrative example of a set having three members, the conjunctive phrases “at least one of A, B, and C” and “at least one of A, B and C” refer to any of the following sets: {A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}, and, if not contradicted explicitly or by context, any set having {A}, {B}, and/or {C} as a subset (e.g., sets with multiple “A”). Thus, such conjunctive language is not generally intended to imply that certain embodiments require at least one of A, at least one of B, and at least one of C each to be present. Similarly, phrases such as “at least one of A, B, or C” and “at least one of A, B or C” refer to the same as “at least one of A, B, and C” and “at least one of A, B and C” refer to any of the following sets: {A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}, unless differing meaning is explicitly stated or clear from context. 
     Accordingly, the invention is not limited except as by the appended claims.