Prior testing the auxiliary components of both monitoring systems were placed outside of the test switchgear. Author and the electrical engineer from As Harju Elekter Elektrotehnika supporting these tests were both analysing data throughout the testing. Figure 40 presents the test environment, where were two laptops, one for the wired system and one for the wireless Intellisaw system. Author was operating with the IntelliSAW system data.
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Figure 40. Test environment, data analysing
51 IntelliSAW system configuration was done successfully according to the manufacturer’s manual (Intellisaw 2016. IntelliSAW IntelliSAW Configuration Tool User Manual). Each sensor was found by the system and temperatures were corresponding to the ambient temperatures. Sensors were named by the locations, where those were installed (Figure 41).
Figure 41. Sensor data in temp sensor display before tests.
52 3.4 Test 1
In the test 1 the HECON test switchgear main busbars were short circuited (Figure 43) to load the switchgear with the rated current of 630 A. Figure 42 presents the principle diagram of the test 1. The same figure can be found from the appendices, Appendix 8.
Figure 42 Principle diagram of test 1
The HECON test switchgear had been designed in a way that it was easy and safe to short circuit the busbars. Figure 43 presents the short circuit bar that was used to connect the main busbars together.
Figure 43. Short circuit busbar
53 Figure 44 presents the installation of busbar sensors.
Figure 44. Test 1 register 424-426 sensors
In test 1 sensors were installed as shown in figures 37 and 44. In this test the outgoing MCCB feeder was not analysed and excessive sensors of registers 427 – 429 were used to measure the cable connections of the supply cabinet. One sensor was placed to measure the ambient temperature and the two sensors were installed to measure the phases of L1 and L2 of the cable connections of the supply cabinet (Figure 45).
Figure 45. Test 1 register 427-429 sensors
54 3.5 Test 2
In test 2 the outgoing MCCB feeder was loaded with rated current and the temperatures of the cable connections of the MCCB were measured. Figure 46 presents the principle diagram of test 2. The same figure can be found from the appendices, Appendix 9.
Figure 46. Principle diagram of test 2
In this test, the MCCB was loaded with load resistors and the short circuit busbar was not used.
The sensors presented in Figure 47 were installed to the outgoing cable connections of the outgoing MCCB.
Figure 47. Test 2 register 427-429 sensors
55 Sensors that were installed to the busbars in test 1 were re-installed to the cable connections of the cables between busbars and outgoing MCCB (Figure 48).
Figure 48. Test 2 register 424-426 sensors
In test 2 loading resistors were used (Figure 49). In the trolley there were four three-phase step-up transformers (that the currents in the loading resistors would be smaller compared with the currents in the switchgear) and three adjustable load resistors per each phase of the step-up transformer. In test 2, only one step-up transformer was needed to load the MCCB.
Figure 49. Loading resistors in test 2
56 Step-up transformer for the loading resistors had primary side voltage of 1.5 V and current 504 A and secondary side voltage of 400 V and current 1.9 A (Figure 50). The loading resistors for each phase were 165 ohms and 2 A (Figure 51).
Both the supply cabinet voltage and the resistance of load resistors were adjusted until the load in the MCCB circuit (Figure 52) was the same as the rated current of the MCCB 250 A.
Figure 52. Load current in the testing of the MCCB Figure 50. Step-up transformer Figure 51. Loading resistor
57 3.6 Test 1 results
Test 1 lasted three hours and 37 minutes. At first, 690 A load current was applied to speed up the temperature rise. When the temperatures had risen, the load current was set to the rated value of test HECON switchgear (630 A). In test 1, the main switch L1 wired sensor became loose after 50 minutes of testing. This can be seen in the test-1-wired-sensor report. Results are presented in Figure 53 (Appendix 8)
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Figure 53. Temperature rise graph of test 1 with wired sensors
IntelliSAW software was recording data to an Excel file during the tests. One row of temperature data was recorded in every second. Total of 13334 rows of temperature data was created to the Excel file when test 1 was completed. Figure 54 is presenting the graph from the received Excel data. The results are also presented in attachments, Appendix 10.
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Figure 54. Temperature rise graph of test 1 with IntelliSAW wireless sensors
In Table 3 are presented the steady state temperature values of the two temperature monitoring systems at the end of test 1. The first column indicates the measurement location. The second and the third columns present the steady state values of the wired sensor system and the wireless IntelliSAW sensor system. The differences between the results of the wired and IntelliSAW monitoring systems are brought out in the “Difference” columns (differences brought out in temperature K values and in percentage).
The temperature values of the main busbar are meeting the prior expectations described in chapter 3.2. In Table 2 the main busbar steady temperature is approximately 65 celsius degrees at the ambient temperature of 20 celsius degrees. Due to the blocked natural ventilation the main busbar temperature is higher than in the free air. This means that in the given circumstances the main busbars at 630 A rated current and in IP44 switchgear the steady state temperature would be 80 celsius degrees at the ambient temperature of 35 celsius degrees according to the standard IEC 61439-1. In comparison, in the free air the same busbars would reach steady state temperature of 65 celsius degrees at the ambient temperature of 35 celsius degrees and with current of 780 A.
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Table 3. Comparison of results of test 1
At the end of the measurements, thermal images at the sensor locations were taken. Figures 55 – 62 illustrate the locations and the thermal images of each sensor location at the end of test 1. In the busbar images (Figure 57 & Figure 59) the temperature data of thermal imaging is also added to the photos of the locations. The reason for this is following. If for example Figures 57 and 59 are looked, it can be seen that in that the thermal imaging at location of the wired sensors are indicating temperature of ~40 degrees of celsius and the thermal imaging at the location of wireless sensors are indicating temperature of ~ 50 degrees of celsius.
However, if data in Table 2 is looked, it can be seen that both temperature monitoring systems are giving temperature results between 90 and 100 degrees of celsius. This is a big difference in temperatures between the thermal camera images and the sensors. As two separate monitoring systems are both registering values close to each other it can be concluded that the thermal imaging results are in this case not reliable.
Answer can be found in the IR imaging. Temperatures between 90 -100 degrees of celsius really exist in these connections, but those were not noticed straight away from the sensor locations.
This why it is important to read the thermal images correctly. If only direct locations of sensors are analysed the temperatures could be wrongly interpreted.
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Figure 58. Busbar (BB) connection after main-switch (MS) L1, L2 and L3 IR image
Figure 55. Cable before MS L2 and L3 normal image
Figure 57. Busbar (BB) connection after main-switch (MS) L1, L2 and L3 normal image
Figure 56. Cable before MS L2 and L3 IR image
Figure 60. Horizontal and vertical BB connection L1, L2 and L3 IR image
Figure 59. Horizontal and vertical BB connection L1, L2 and L3 normal image
61 3.7 Test 2 results
The duration of Test 2 was three hours and 36 minutes. This test was done twice. At the first time it was not noticed that the thermal protection relay of the 250 A MCCB was set to a lower tripping setting. Approximately 30 minutes from the start of the test the outgoing breaker tripped. The trip setting of the thermal relay was set to 250 A level and the MCCB was closed again. The test was finished according to the test plan, but it was decided to repeat the test again.
At the second time, there was no tripping. In the thesis are presented the first time test of test 2 in wireless temperature graph (Figure 64 & Appendix 11) and the second time test of the test 2 in wired temperature graph (Figure 63 & Appendix 9). Final results of both of these tests are the same, the difference in the tests is only that the breaker tripped and was reset in the first time test.
Figure 61. Power cable L1, L2 and ambient normal image
Figure 62. Power cable L1, L2 and ambient IR image
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Figure 63. Temperature rise graph of test 2 with wired sensors (second time test)
IntelliSAW software was recording data to an Excel file during the tests. One row of temperature data was recorded in every second. Total of 11723 rows of temperature data were created to the Excel file when test 2 was completed. Figure 64 is presenting a graph from the received Excel data. The results are also presented in attachments, Appendix 11.
Figure 64. Temperature rise graph of test 2 with IntelliSAW wireless sensors (first time test)
63 In Table 4 are presented the steady state temperature values of the two temperature monitoring systems at the end of test 2. The first column indicates the measurement location. The second and the third columns present the steady state values of the wired sensor system and the wireless IntelliSAW sensor system. The differences between the results of the wired and IntelliSAW monitoring systems are brought out in the “Difference” columns (differences brought out in temperature K values and in percentage).
Measurement place Wired
Table 4. Comparison of results of test 2
At the end of the measurements, thermal images at the sensor locations were taken. In figures 65 – 72 are presented the locations and the thermal images of each sensor location at the end of the test 2. From each measurement location normal and thermal images are presented.
Figure 65. Cable before MS L1, L2 and L3 normal image
Figure 66. Cable before MS L1, L2 and L3 IR image
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Figure 68. Busbar (BB) connection after main-switch (MS) L1 IR image
Figure 72. Outgoing cable L1, L2 and L3 IR image
Figure 70. Vertical BB and cable connection L2 and L3 IR image
Figure 71. Outgoing cable L1, L2 and L3 normal image
Figure 69. Vertical BB and cable connection L2 and L3 normal image
Figure 67. Busbar (BB) connection after main-switch (MS) normal image
65 3.8 Conclusions
Two tests were performed in this thesis and temperatures were measured with three different temperature monitoring systems. The thermal imaging results are also added to the comparison tables with the difference analysis compared to the IntelliSAW system (Table 5 & Table 6).
Measurement place Wired
Busbar (BB) connection after main-switch (MS) L1 91.4/364.6 101.4/374.6 96.7/369.9 -10/-4.7 -3 %/1 %
BB connection after MS L2 - 103.1/376.3 95.1/368.3 -/8 -/2 %
BB connection after MS L3 95.1/368.3 98/371.2 90.2/363.4 -2.9/-7.8 -1 %/2 % Horizontal and vertical BB connection L1 63.3/336.5 62.2/335.4 64.1/337.3 1.1/1.9 0 %/1 % Horizontal and vertical BB connection L2 66.1/339.3 64.1/337.3 64.1/337.3 2.0/0.0 1 %/0 % Horizontal and vertical BB connection L3 60.8/334.0 63.9/337.1 63.9/337.1 -3.1/0.0 -1 %/0 %
Power cable L1 30.7/303.9 31.2/304.4 31.2/304.4 -0.5/0.0 0 %/0 %
Power cable L2 33.1/306.3 32/305.2 33.2/306.4 1.1/1.2 0 %/0 %
Ambient 20.3/293.5 22.6/295.8 22.8/296.0 -2.3/0.2 -1 %/0 %
Table 5. Comparison of results of test 1 including data from thermal camera
Measurement place Wired
Busbar (BB) connection after main-switch (MS) L1 38.3/311.5 42/315.2 42.1/315.3 -3.7/0.1 -1 %/0 % BB connection after MS L2 39.8/313.0 41.2/314.4 42.1/315.3 -1.4/0.9 0 %/0 % BB connection after MS L3 39.3/312.5 40/313.2 42.1/315.3 -0.7/2.1 0 %/1 % Vertical BB and cable connection L1 42.3/315.5 40.2/313.4 39.0/312.2 2.1/-1.2 1 %/0 % Vertical BB and cable connection L2 40.4/313.6 38.2/311.4 39.0/312.2 2.2/0.8 1 %/0 % Vertical BB and cable connection L3 35.3/308.5 38.4/311.6 38.2/311.4 -3.1/-0.2 -1 %/0 %
Outgoing cable L1 77.8/351.0 69.3/342.5 69.3/342.5 8.5/0.0 2 %/0 %
Outgoing cable L2 77.9/351.1 68.1/341.3 70.6/343.8 9.8/2.5 3 %/1 %
Outgoing cable L3 70.2/343.4 65.4/338.6 67.8/341.0 4.8/2.4 1 %/1 %
Ambient 21.7/294.9 22.6/295.8 22.8/296.0 -0.9/0.2 0 %/0 %
Table 6. Comparison of results of test 2 including data from thermal camera
66 The different temperature monitoring systems and devices have the following accuracies:
- IntelliSAW sensors = 2 degrees of celsius in the range of 0-80 degrees of celsius, 4 degrees of celsius in the full range (Intellisaw. 2016. IntelliSAW Sensor Installation Manual).
- Thermocouple Z2-K-5M = 1.5 degrees of celsius (Labfacility).
- Amplifiers AD8495 = 1 degrees of celsius (Analog devices. 2010).
- Fluke Ti400 = 2 degrees of celsius (Fluke. 2021).
In both tests, 12 connection points were monitored. Under temperatures of 80 celsius degrees, the error margin is 4 celsius degrees between the IntelliSAW system and the thermal camera.
Under temperatures of 80 celsius degrees, the error margin is 4.5 celsius degrees between the IntelliSAW system and the wired system (summarized accuracy 1 + 1.5). Over temperatures of 80 celsius degrees, error margin is 6 celsius degrees between the IntelliSAW system and the thermal camera. Over temperatures of 80 celsius degrees, the error margin is 6.5 celsius degrees between the IntelliSAW system and the wired system.
At test 1, over 80 celsius degrees the highest single temperature difference between the IntelliSAW system and the wired system is 10 celsius degrees. The highest single temperature difference between the IntelliSAW system and the thermal camera result is 8 celsius degrees.
At test 1, under 80 celsius degrees the highest single temperature difference between the IntelliSAW system and the wired system is 6.4 celsius degrees. The highest single temperature difference between the IntelliSAW system and the thermal camera result is 5 celsius degrees.
At test 2, under 80 celsius degrees the highest single temperature difference between the IntelliSAW system and the wired system is 9.8 celsius degrees. The highest single temperature difference between the IntelliSAW and the thermal camera result is 2.5 celsius degrees.
At test 1, there were in total 2 monitored connection points, where the result difference of the IntelliSAW system compared to results of both, the wired system and the thermal camera, were over error margin (of 4 – 4.5 celsius degrees). “Cable before MS L3” lesser difference was 5 celsius degrees and “BB connection after MS L2” difference was 8 celsius degrees.
67 At test 2, there were no monitored connection points, where the result difference of the IntelliSAW system compared to results of both, the wired system and the thermal camera, were over error margin (of 4 – 4.5 celsius degrees).
Manufacturers give the accuracies for the monitoring devices. There are still other factors, which will affect the accuracy, for example poor contact with the surface. Two different monitoring system results were compared with the IntelliSAW system result. The number of connection points of the IntelliSAW system, where both thermal camera and wired system results compared to the IntelliSAW results were over error margin, was two. “Cable before MS L3” value exceeded the error margin by 1 celsius degrees. “BB connection after MS L2”
exceeded the error margin by 4 celsius degrees. However, in that connection point the results of only one other monitoring system was compared. All other results in the tests, 22 in total, were inside the acceptable error margin. It can be stated, that the IntelliSAW system was successfully installed and the monitored temperature values are real and reliable.
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4 FINAL CONCLUSIONS
4.1 Cost of system
Cost of the system depends on the topology of the system. The most expensive part of the system are the devices. The number of readers and sensors are certainly increasing the costs of a compete system. Also, data monitoring solutions may significantly increase the system costs, if some custom solution is required. The cost of system can be compared with other solutions.
It can be compared with a price of a wired temperature monitoring system. It could be for example analysed, how much more the wireless system devices cost compared to the wired system devices, and also how much the assembly time of the wireless system is lower compared to the wired system. Another way to compare costs is to compare it with the costs of manual thermal imaging. When a wireless temperature monitoring system is installed, it has a high initial cost, but after that it basically does not have any cost and manual thermal imaging has labour costs when it is done continuously. However, wireless temperature system component lifetime is limited. This should be considered, when calculating specific payback time. It is possible to make some rough calculations for example by comparing the costs of a wireless system to the continuous costs of thermal imaging. It is important to remember that it is always recommended to carry out the manual thermal imaging even when the switchgear is equipped with a wireless temperature monitoring system. But in some switchgears, the wireless temperature monitoring system can cover all the connection points in the switchgear and in such cases the thermal imaging is not required as it does not add any additional value for safety.
The following comparisons are rough estimations. Specific prices of the IntelliSAW devices are not presented in this thesis. The analysis of wired monitoring systems is out of scope of this thesis. Pricing of thermal imaging can vary a lot (whether the customer owns a thermal camera or wants to purchase the device or requires service from another company). If thermal imaging service is required how long travel time is required from the headquarters to the site. Are there a lot of switchgears to be monitored at the same time or is there only one switchgear. It is not possible to make exact cost comparisons, because situations may be very different. However, some cost comparisons are presented in this thesis.
69 When comparing wired systems with wireless systems, a very rough first comparisons indicate that the wired system cost could be half of the cost of a wireless system. Estimation cost for an example wireless system, which includes 6 sensors and 2 air interfaces could be 2000 euros. In this case the cost of a wired system would be 1000 euros. Assembly cost price in a switchgear manufacturing is roughly 30 euros/hour. Estimated assembly time for one wired sensor could be 15 minutes. For the given example the assembly cost of a wired system is presented as.
6 × 15 min = 90 min = 1.5 h × 30 € = 45 €. (6) The assembly cost for a wired system assembly is 45 €. Comparing the assembly times with wireless IntelliSAW system, it must be considered, that the wireless system also includes air interface cabling assembly time. For six sensors two air interface cables are needed. The same assembly time for the air interface cable can be considered as assembling a wired sensor. This must be subtracted from equation (6).
45 € − 2 × 0.15 h × 30 € = 30 € (7)
In this case the differences in the costs of the assembly time are not exceeding the differences in the costs of devices to be in favor of the wireless system. If the differences in the device costs are smaller and the differences in the wiring assembly cost are higher, then the more wireless system can be preferred.
We can also compare the systems with the cost of thermal imaging. The following should be considered. It is very common that thermal imaging is done for multiple switchgears on site.
Then having just one switchgear on site with wireless monitoring would not give much savings compared to the total costs for thermal imaging of all the switchgears. The benefits would come out in switchgears where the wireless temperature monitoring system covers nearly all the switchgear connections and an additional thermal imaging is not needed. For example, if there is a switchgear, where there is one incoming MCCB and three outgoing MCCBs and a thermal imaging is required for this switchgear once per year.
70 Cost of thermal imaging could be considered 500 euros, which includes travel costs, monitoring costs and report costs. The cost of the wireless monitoring system for this switchgear would be 8000 euros (total of four MCCBs and six sensors per each MCCB). It could be assumed that the cost of thermal camera monitoring prices would increase every year (e.g., 25 € every year).
In this case, the break-even time for the wireless system would be 15 years (Figure 73).
Figure 73. Thermal camera monitoring costs compared to wireless system
The price comparisons in this thesis are giving some rough estimation of what kind of financial incentives are required for the wireless system. But cost is only one of many aspects to be considered in these systems, whereas safety and control aspects could be more dominant in the project. The target of the wireless temperature monitoring system is not to fully replace the thermal imaging but rather the two combined could cover the fire safety aspects of the
The price comparisons in this thesis are giving some rough estimation of what kind of financial incentives are required for the wireless system. But cost is only one of many aspects to be considered in these systems, whereas safety and control aspects could be more dominant in the project. The target of the wireless temperature monitoring system is not to fully replace the thermal imaging but rather the two combined could cover the fire safety aspects of the