Why do we conduct oil testing of our power equipment?
Many medium- and high-voltage transformers and circuit breakers utilize different types of oils for insulation. Chemical testing of the oil has proven to be a very dependable method of locating existing or potential problems.
Only a brief overview of some of the common tests can be provided here.
One of the most obvious problems that would significantly reduce the insulation value of the oil is contamination such as moisture or, for circuit breakers and load top changers, carbon.
This can be tested on-site by measuring the voltage at which dielectric breakdown occurs with a special test set that is designed for this purpose.
Oil samples may be sent to a testing laboratory for a series of tests. Measurements of the acidity give an indication of how much oxidation or contamination the oil has experienced.
Interfacial tension, the force that is required to rupture the surface tension at an oil-water interface, is also an indication of possible oxidation or contamination.
One of the most successful tests in determining if a transformer winding has experienced hot spots, corona discharge, or arcing is the dissolved gas analysis test. An oil sample is taken with a special cylinder that is air tight, and the gases that are dissolved in the oil are analyzed.
By determining the type and amount of gas that has been dissolved in the oil, predictions can be made about the internal integrity of the transformer winding.
Showing posts with label Test. Show all posts
Showing posts with label Test. Show all posts
INFRARED SCANNING FOR HOTSPOT OF ELECTRICAL COMPONENTS BASIC INFORMATION
What is Infrared Scanning? How is it done?
Infrared scanning is a method that is utilized to locate high-resistance connections ("hot spots") by using a camera that turns infrared radiation into a visible image.
This test is performed with the equipment in service carrying normal load current, which is a major advantage because it does not interrupt normal production. Exposure to energized equipment, of course, carries the possibility of exposure to electrical hazards.
The operator shall recognize and deal with such potential hazards accordingly.
The most common use of infrared scanning is to locate loose or corroded connections in switchboards, panel boards, bus ways, and motor starters.
It is a comparative type test in which the person who performs the scan is looking for an area that appears brighter (hotter) than a similar area, such as a lug connection on phase "A" as it compares to similar connections on phases "B" and "C"
The person should be aware of how unbalanced loading may affect heating, thereby giving an indication similar to looseness.
One limitation of infrared scanning is that the equipment has to be carrying enough load for the hot spots to be visible.
At lower loads, there may not be enough heat generated to locate a problem, even when the connections are significantly looser than they should be.
Infrared scanning is a method that is utilized to locate high-resistance connections ("hot spots") by using a camera that turns infrared radiation into a visible image.
This test is performed with the equipment in service carrying normal load current, which is a major advantage because it does not interrupt normal production. Exposure to energized equipment, of course, carries the possibility of exposure to electrical hazards.
The operator shall recognize and deal with such potential hazards accordingly.
The most common use of infrared scanning is to locate loose or corroded connections in switchboards, panel boards, bus ways, and motor starters.
It is a comparative type test in which the person who performs the scan is looking for an area that appears brighter (hotter) than a similar area, such as a lug connection on phase "A" as it compares to similar connections on phases "B" and "C"
The person should be aware of how unbalanced loading may affect heating, thereby giving an indication similar to looseness.
One limitation of infrared scanning is that the equipment has to be carrying enough load for the hot spots to be visible.
At lower loads, there may not be enough heat generated to locate a problem, even when the connections are significantly looser than they should be.
MOTOR SURGE COMPARISON TESTING BASIC INFORMATION AND TUTORIALS
What is Motor surge comparison testing? How is it done?
Motor surge comparison testing addresses the problem of insufficient test voltage to find the weak insulation between turns by utilizing a high-voltage pulse. Two identical high-voltage pulses are introduced into two windings of a motor.
The propagation of the pulse through one winding is compared to the propagation of the identical pulse through the winding next to it.
An oscilloscope (usually built into the surge tester) is used to look at the traces and to compare them. The patterns should be identical (or very nearly so) and can appear as one trace (two superimposed traces) if both windings are good.
A turn-to-turn failure (or a failure to ground) is indicated by two distinctly different traces appearing on the oscilloscope.
Motor surge comparison testing has been used by motor winding shops for many years. There are now portable models that are available for field testing.
Motor surge comparison testing has proven to be a valuable tool in detecting the early stages of a winding failure, both from the standpoint of preventing an unexpected failure during operation and preventing a catastrophic failure of the motor so it can be repaired instead of needing to be replaced.
Motor surge comparison testing addresses the problem of insufficient test voltage to find the weak insulation between turns by utilizing a high-voltage pulse. Two identical high-voltage pulses are introduced into two windings of a motor.
The propagation of the pulse through one winding is compared to the propagation of the identical pulse through the winding next to it.
An oscilloscope (usually built into the surge tester) is used to look at the traces and to compare them. The patterns should be identical (or very nearly so) and can appear as one trace (two superimposed traces) if both windings are good.
A turn-to-turn failure (or a failure to ground) is indicated by two distinctly different traces appearing on the oscilloscope.
Motor surge comparison testing has been used by motor winding shops for many years. There are now portable models that are available for field testing.
Motor surge comparison testing has proven to be a valuable tool in detecting the early stages of a winding failure, both from the standpoint of preventing an unexpected failure during operation and preventing a catastrophic failure of the motor so it can be repaired instead of needing to be replaced.
TRANSFORMER TURNS RATIO TESTING BASIC INFORMATION AND TUTORIALS
What is Transformer turns ratio (TTR) testing? How is it done?
The voltage across the primary of a transformer is directly proportional to the voltage across the secondary, multiplied by the ratio of primary winding turns to secondary winding turns.
In order to ensure that the transformer was wound properly when it was new, and to help locate subsequent turn-to-turn faults in the winding, it is common practice to perform a TTR test.
The simplest method would be to energize one primary winding with a known voltage (that is less than or equal to the windingÕs rating) and measure the voltage on the other winding.
Since source test voltages can fluctuate, it is often more accurate to use a test set, designed for this purpose, that creates the test voltage internally, thus giving a direct read-out of the ratio measured.
The voltage across the primary of a transformer is directly proportional to the voltage across the secondary, multiplied by the ratio of primary winding turns to secondary winding turns.
In order to ensure that the transformer was wound properly when it was new, and to help locate subsequent turn-to-turn faults in the winding, it is common practice to perform a TTR test.
The simplest method would be to energize one primary winding with a known voltage (that is less than or equal to the windingÕs rating) and measure the voltage on the other winding.
Since source test voltages can fluctuate, it is often more accurate to use a test set, designed for this purpose, that creates the test voltage internally, thus giving a direct read-out of the ratio measured.
WINDING AND CONTACT RESISTANCE TEST BASIC INFORMATION AND TUTORIALS
What are winding and contact resistance testing?
Winding and contact resistance are similar in that both are looking for a very low ohmic value, since they are measuring the "resistance" of a component that is supposed to conduct electricity.
A Kelvin Bridge has long been a standard method of measuring low values of resistance, and is still in use today.
With the advent of electronics, there are digital meters available that also are capable of measuring very low values (milliohms or microohms) of resistance.
The typical low-resistance ohmmeter uses four terminals (to eliminate lead resistance) in which a dc current is injected into the conductor to be measured and the voltage drop across the conductor is measured.
Contact resistance test sets can be used to measure the resistance of bus joints and cable joints, as well as the closed contacts of a circuit breaker or motor starter.
In many cases, it is a comparative type test in which the resistance of one set of contacts is compared to the readings obtained from the other two phases of the same, or a similar, piece of equipment.
Winding resistance differs from contact resistance in that the inductance of large windings can interfere with the operation of the test set.
There are test sets, available commercially, that are designed specifically for large transformer and motor windings, for cases in which a standard low-resistance ohmmeter is not adequate.
Winding and contact resistance are similar in that both are looking for a very low ohmic value, since they are measuring the "resistance" of a component that is supposed to conduct electricity.
A Kelvin Bridge has long been a standard method of measuring low values of resistance, and is still in use today.
With the advent of electronics, there are digital meters available that also are capable of measuring very low values (milliohms or microohms) of resistance.
The typical low-resistance ohmmeter uses four terminals (to eliminate lead resistance) in which a dc current is injected into the conductor to be measured and the voltage drop across the conductor is measured.
Contact resistance test sets can be used to measure the resistance of bus joints and cable joints, as well as the closed contacts of a circuit breaker or motor starter.
In many cases, it is a comparative type test in which the resistance of one set of contacts is compared to the readings obtained from the other two phases of the same, or a similar, piece of equipment.
Winding resistance differs from contact resistance in that the inductance of large windings can interfere with the operation of the test set.
There are test sets, available commercially, that are designed specifically for large transformer and motor windings, for cases in which a standard low-resistance ohmmeter is not adequate.
INSTRUMENT TRANSFORMERS TESTING BASIC INFORMATION AND TUTORIALS
What is instrument transformer testing?
There are two common designations of instrument transformers: CTs and voltage transformers (VTs) or potential transformers (PTs). The function of an instrument transformer is to reduce the level of voltage or current so that the protective relay (or metering) does not have to be rated for full line voltage or current.
The insulation resistance, transformer ratio, and polarity may be tested in both CTs and VTs. The ratio is the number of turns of wire in the primary winding divided by the number of turns of wire in the secondary winding.
The polarity is determined by which way the wire was wrapped around the iron core. This determines the relationship between the primary winding terminal (H1) and the secondary winding terminal (X1) so that X1 is positive with respect to X2 at the same time that H1 is positive with respect to H2.
The correctness of polarity is important to the correct operation of many relays and metering instruments. CTs often have two additional tests performed: "burden" and "saturation" tests. The burden on a CT is the amount of impedance connected to the secondary winding as a load, usually in the form of protective relays or metering.
The burden test consists of injecting a known current level (usually 1-5 A ac) into the load (usually from the shorting terminal block of the CT) and measuring the voltage at the point of injection. The impedance (or burden) of the circuit is the ratio of the voltage measured to the current injected.
A saturation test is performed to find out the voltage at which the iron in the CT saturates. A known voltage source is connected to the secondary of the transformer and is raised in steps, while the current value is recorded at each step.
When saturation is reached, the given voltage changes cause much smaller changes in current. The saturation test is used in conjunction with the burden test to make sure that the CT is capable of operating the load (usually protective relays) to which it may be subjected.
If the burden on the CT is too high, it may go into saturation and be unable to maintain its proper ratio. When this happens, protective relays may trip too slowly or not at all due to an insufficient level of current from the CT secondary.
There are two common designations of instrument transformers: CTs and voltage transformers (VTs) or potential transformers (PTs). The function of an instrument transformer is to reduce the level of voltage or current so that the protective relay (or metering) does not have to be rated for full line voltage or current.
The insulation resistance, transformer ratio, and polarity may be tested in both CTs and VTs. The ratio is the number of turns of wire in the primary winding divided by the number of turns of wire in the secondary winding.
The polarity is determined by which way the wire was wrapped around the iron core. This determines the relationship between the primary winding terminal (H1) and the secondary winding terminal (X1) so that X1 is positive with respect to X2 at the same time that H1 is positive with respect to H2.
The correctness of polarity is important to the correct operation of many relays and metering instruments. CTs often have two additional tests performed: "burden" and "saturation" tests. The burden on a CT is the amount of impedance connected to the secondary winding as a load, usually in the form of protective relays or metering.
The burden test consists of injecting a known current level (usually 1-5 A ac) into the load (usually from the shorting terminal block of the CT) and measuring the voltage at the point of injection. The impedance (or burden) of the circuit is the ratio of the voltage measured to the current injected.
A saturation test is performed to find out the voltage at which the iron in the CT saturates. A known voltage source is connected to the secondary of the transformer and is raised in steps, while the current value is recorded at each step.
When saturation is reached, the given voltage changes cause much smaller changes in current. The saturation test is used in conjunction with the burden test to make sure that the CT is capable of operating the load (usually protective relays) to which it may be subjected.
If the burden on the CT is too high, it may go into saturation and be unable to maintain its proper ratio. When this happens, protective relays may trip too slowly or not at all due to an insufficient level of current from the CT secondary.
PROTECTIVE RELAY TESTING BASIC INFORMATION AND TUTORIALS
What is protective relay testing? How to do protective relay testing?
Protective relaying is a very broad subject. Only a brief overview can be given here. There are two major objectives in protective relaying.
First, a protective relay serves to provide equipment protection (i.e., locate and isolate overloads, short circuits, undervoltages, and other types of electrical problems quickly in order to minimize damage).
Second, the protective device that is closest to the problem should operate first to clear the problem, and no other device should operate unless the closest one fails. This concept, known as "selective tripping" or "selectivity", maintains service to as much of the electrical system as possible by isolating only the problem area.
In order to achieve these objectives, each relay must function as it was designed, and the relays must function in conjunction with the other protective devices in the system. Having all the protective devices function as one overall protective system is called "coordination".
Each protective device has specific parameters within which it has been designed to operate. For example, a single element fuse has a value of current above which it opens.
It takes a specific amount of time for a given current to melt the link away and open the fuse. Manufacturers of fuses publish "time-current" curves that show how long it takes a fuse to operate for varying current values.
Generally, the higher the current, the shorter the time.
This same inverse current-vs.-time concept is used for overcurrent relays and for low-voltage circuit breakers. Relays and low-voltage circuit breakers (with internal trip units) have a range of "pickup" operating current that causes them to operate.
In many cases, this value of current is adjustable. By properly selecting the type, characteristic, and/or setting of fuses, relays, or circuit breakers, the system can be coordinated so that the device that is closest to the problem opens before any device upstream of it. It is necessary to select compatible time current characteristics of the devices for the entire system, in addition to selecting the proper settings for the devices.
Prior to performing protective relay testing, a coordination study should be completed to determine the proper settings for the relays to be calibrated. This is usually done by the design engineer when the system is first installed. If there have been revisions or additions to the system, a new study may be necessary.
Once the coordination study has been completed, the relays need to be calibrated to the proper settings. There are special test sets available for this purpose that inject currents and voltages, as necessary, and time the various operations of the relays.
This type of testing is usually performed by a technician who specializes in this area. Depending upon the relay to be calibrated, quite complex test equipment may be required and in-depth training in protective relaying may be needed to properly set the relay.
Protective relaying is a very broad subject. Only a brief overview can be given here. There are two major objectives in protective relaying.
First, a protective relay serves to provide equipment protection (i.e., locate and isolate overloads, short circuits, undervoltages, and other types of electrical problems quickly in order to minimize damage).
Second, the protective device that is closest to the problem should operate first to clear the problem, and no other device should operate unless the closest one fails. This concept, known as "selective tripping" or "selectivity", maintains service to as much of the electrical system as possible by isolating only the problem area.
In order to achieve these objectives, each relay must function as it was designed, and the relays must function in conjunction with the other protective devices in the system. Having all the protective devices function as one overall protective system is called "coordination".
Each protective device has specific parameters within which it has been designed to operate. For example, a single element fuse has a value of current above which it opens.
It takes a specific amount of time for a given current to melt the link away and open the fuse. Manufacturers of fuses publish "time-current" curves that show how long it takes a fuse to operate for varying current values.
Generally, the higher the current, the shorter the time.
This same inverse current-vs.-time concept is used for overcurrent relays and for low-voltage circuit breakers. Relays and low-voltage circuit breakers (with internal trip units) have a range of "pickup" operating current that causes them to operate.
In many cases, this value of current is adjustable. By properly selecting the type, characteristic, and/or setting of fuses, relays, or circuit breakers, the system can be coordinated so that the device that is closest to the problem opens before any device upstream of it. It is necessary to select compatible time current characteristics of the devices for the entire system, in addition to selecting the proper settings for the devices.
Prior to performing protective relay testing, a coordination study should be completed to determine the proper settings for the relays to be calibrated. This is usually done by the design engineer when the system is first installed. If there have been revisions or additions to the system, a new study may be necessary.
Once the coordination study has been completed, the relays need to be calibrated to the proper settings. There are special test sets available for this purpose that inject currents and voltages, as necessary, and time the various operations of the relays.
This type of testing is usually performed by a technician who specializes in this area. Depending upon the relay to be calibrated, quite complex test equipment may be required and in-depth training in protective relaying may be needed to properly set the relay.
MEDIUM AND HIGH VOLTAGE CABLE TESTING BASIC INFORMATION AND TUTORIALS
Most cables that are rated for use at voltage levels above 600 V are shielded cables. A shielded cable has a conductor in the center, a semiconducting layer over the strands that is surrounded by insulation, a semiconducting layer, and then a metal foil or wire mesh that surrounds the whole assembly.
There is usually another layer over the shield that makes up the outer jacket of the cable. It is a common practice to hi-pot test the cables on initial installation in order to verify that the cables were not damaged when they were pulled into place and that all the splices and/or terminations were installed properly.
The voltage level that is selected usually is lower than factory test levels, frequently 80% of the dc equivalent of the factory test level.
There are normally two considerations that are given to hi-pot testing of cables as a routine maintenance practice. One is a function of the chosen maintenance philosophy [i.e., breakdown maintenance, preventive maintenance, predictive maintenance, or reliability-centered maintenance (RCM)].
The other depends upon the type of operation and how critical it is to have continuous power without interruption.
The debate on whether or not to perform maintenance hi-pot testing centers around the fact that a cable in marginal condition can be caused to fail by the hi-pot test itself. A cable that is in good condition should not be harmed.
People who subscribe to maintenance testing feel that it is much better to have the cable fail under test. Cable maintenance testing frequently is performed at 50-65% of the factory test voltage.
Problems can then be corrected while the circuit is intentionally shut down, thus avoiding an in-service failure that could interrupt production.
It is important to remember that the necessary material, such as splice kits or cable terminations, should be available to facilitate repairs should the cable fail during testing.
There is usually another layer over the shield that makes up the outer jacket of the cable. It is a common practice to hi-pot test the cables on initial installation in order to verify that the cables were not damaged when they were pulled into place and that all the splices and/or terminations were installed properly.
The voltage level that is selected usually is lower than factory test levels, frequently 80% of the dc equivalent of the factory test level.
There are normally two considerations that are given to hi-pot testing of cables as a routine maintenance practice. One is a function of the chosen maintenance philosophy [i.e., breakdown maintenance, preventive maintenance, predictive maintenance, or reliability-centered maintenance (RCM)].
The other depends upon the type of operation and how critical it is to have continuous power without interruption.
The debate on whether or not to perform maintenance hi-pot testing centers around the fact that a cable in marginal condition can be caused to fail by the hi-pot test itself. A cable that is in good condition should not be harmed.
People who subscribe to maintenance testing feel that it is much better to have the cable fail under test. Cable maintenance testing frequently is performed at 50-65% of the factory test voltage.
Problems can then be corrected while the circuit is intentionally shut down, thus avoiding an in-service failure that could interrupt production.
It is important to remember that the necessary material, such as splice kits or cable terminations, should be available to facilitate repairs should the cable fail during testing.
HIGH POTENTIAL (HI POT) TESTING BASIC INFORMATION AND TUTORIALS
What is HiPot testing?
High-potential testing, as its name implies, utilizes higher levels of voltage in performing the tests. It is generally utilized on medium-voltage (1000Ð69 000 V) and on high-voltage (above 69 000 V) equipment.
As stated earlier, the leakage current is usually measured. In some cases, such as in cable hi-potting, the value of leakage current is significant and can be used analytically. In other applications, such as switchgear hi-potting, it is a pass/fail type of test, in which sustaining the voltage level for the appropriate time (usually 1 min) is considered "passing."
High-potential testing, as its name implies, utilizes higher levels of voltage in performing the tests. It is generally utilized on medium-voltage (1000Ð69 000 V) and on high-voltage (above 69 000 V) equipment.
As stated earlier, the leakage current is usually measured. In some cases, such as in cable hi-potting, the value of leakage current is significant and can be used analytically. In other applications, such as switchgear hi-potting, it is a pass/fail type of test, in which sustaining the voltage level for the appropriate time (usually 1 min) is considered "passing."
INSULATION RESISTANCE TEST BASIC INFORMATION AND TUTORIALS
What is insulation resistance test? How to conduct insulation resistance test?
Insulation resistance tests are typically performed on motors, circuit breakers, transformers, low-voltage (unshielded) cables, switchboards, and panel boards to determine if degradation due to aging, environmental, or other factors has affected the integrity of the insulation.
This test is normally conducted for 1 min, and the insulation resistance value is then recorded. As mentioned earlier, the electrical properties of the insulation and the amount of surface area directly affect the capacitance between the conductor and ground, and therefore affect the charging time.
With larger motors, generators, and transformers, a common test is to measure the "dielectric absorption ratio" or the "polarization index" of the piece of equipment being tested. The dielectric absorption ratio is the 1 min insulation resistance reading divided by the 30 s insulation resistance reading.
The polarization index is the 10 min (continuous) insulation resistance reading divided by the 1 min reading. Both of these provide additional information as to the quality of the insulation.
Many types of insulation become dry and brittle as they age, thereby becoming less effective capacitors. Thus, a low polarization index (less than 2.0) may indicate poor insulation.
Even though insulation may have a high insulation resistance reading, there could still be a problem, since the motor and transformer windings are subjected to strong mechanical stresses on starting. With the exception of electronic equipment (which can be damaged by testing), insulation resistance testing is normally done on most types of new equipment and is also part of a maintenance program.
It is a good practice to perform insulation resistance testing on switchgear and panelboards after maintenance has been performed on them, just prior to re-energizing them. This prevents re-energizing the equipment with safety grounds still applied or with tools accidentally left inside.
Insulation resistance tests are typically performed on motors, circuit breakers, transformers, low-voltage (unshielded) cables, switchboards, and panel boards to determine if degradation due to aging, environmental, or other factors has affected the integrity of the insulation.
This test is normally conducted for 1 min, and the insulation resistance value is then recorded. As mentioned earlier, the electrical properties of the insulation and the amount of surface area directly affect the capacitance between the conductor and ground, and therefore affect the charging time.
With larger motors, generators, and transformers, a common test is to measure the "dielectric absorption ratio" or the "polarization index" of the piece of equipment being tested. The dielectric absorption ratio is the 1 min insulation resistance reading divided by the 30 s insulation resistance reading.
The polarization index is the 10 min (continuous) insulation resistance reading divided by the 1 min reading. Both of these provide additional information as to the quality of the insulation.
Many types of insulation become dry and brittle as they age, thereby becoming less effective capacitors. Thus, a low polarization index (less than 2.0) may indicate poor insulation.
Even though insulation may have a high insulation resistance reading, there could still be a problem, since the motor and transformer windings are subjected to strong mechanical stresses on starting. With the exception of electronic equipment (which can be damaged by testing), insulation resistance testing is normally done on most types of new equipment and is also part of a maintenance program.
It is a good practice to perform insulation resistance testing on switchgear and panelboards after maintenance has been performed on them, just prior to re-energizing them. This prevents re-energizing the equipment with safety grounds still applied or with tools accidentally left inside.
AIR QUALITY TESTING AND MONITORING METHODS OF SAMPLING
Indoor air quality testing may be necessary to ensure employee safety. Testing and monitoring may be applied to those conditions where employees may be exposed to:
nitrogen dioxide and sulfur dioxide
landfill gases
noxious odors
radon gas
factory emissions
odor complaints
rainwater
metals
smoke levels
dust
volatile organic compounds
indoor air quality (including Carbon Monoxide)
The results of air quality testing may be used to:
• Assign levels of worker respiratory protection
• For emergency planning
Methods of Sampling and Testing
Electric Power producers shall provide adequate means of carrying air monitoring in generator houses, transmitting stations, injection and switching substations, etc.
Three main methods are available to measure air pollution:
Passive Sampling: This refers to absorption or diffusion tubes or badges that provide a simple and inexpensive indication of average pollution levels over a period of weeks or months. Plastic tubes or discs open at one end to the atmosphere and with a chemical absorbent at the other, collect a sample for subsequent analysis in the laboratory.
The low cost per tube allows sampling at a number of points and is useful in highlighting "hotspots" where more detailed study may be needed. The quality and accuracy of the data from passive sampling tubes does not make them suitable for precise measurements but they can give useful long term trend data.
Active Sampling: This involves the collection of samples, by physical or chemical means, for subsequent laboratory analysis. Typically, a known volume of air is pumped through a filter or chemical collector for a known period of time - the collection medium is then subjected to laboratory analysis. This method is not suitable for continuous or near-real time air quality monitoring.
Automatic Sampling: This is the most sophisticated method of air quality analysis, producing high-resolution measurement data of a range of pollutants. The pollutants that can be measured include, but are not limited to, NOx, S02 CO, 03, VOCs, PM10, PM2.5, Carbon Black, Hg, Benzene etc. The air quality is continuously sampled and measured on-line and in real-time.
The real time data is stored, typically as one hourly averages, with data being collected remotely from individual monitoring stations by telemetry. Remote control of the monitoring and data system is also possible as is remote diagnostics for most of the analyzers.
nitrogen dioxide and sulfur dioxide
landfill gases
noxious odors
radon gas
factory emissions
odor complaints
rainwater
metals
smoke levels
dust
volatile organic compounds
indoor air quality (including Carbon Monoxide)
The results of air quality testing may be used to:
• Assign levels of worker respiratory protection
• For emergency planning
Methods of Sampling and Testing
Electric Power producers shall provide adequate means of carrying air monitoring in generator houses, transmitting stations, injection and switching substations, etc.
Three main methods are available to measure air pollution:
Passive Sampling: This refers to absorption or diffusion tubes or badges that provide a simple and inexpensive indication of average pollution levels over a period of weeks or months. Plastic tubes or discs open at one end to the atmosphere and with a chemical absorbent at the other, collect a sample for subsequent analysis in the laboratory.
The low cost per tube allows sampling at a number of points and is useful in highlighting "hotspots" where more detailed study may be needed. The quality and accuracy of the data from passive sampling tubes does not make them suitable for precise measurements but they can give useful long term trend data.
Active Sampling: This involves the collection of samples, by physical or chemical means, for subsequent laboratory analysis. Typically, a known volume of air is pumped through a filter or chemical collector for a known period of time - the collection medium is then subjected to laboratory analysis. This method is not suitable for continuous or near-real time air quality monitoring.
Automatic Sampling: This is the most sophisticated method of air quality analysis, producing high-resolution measurement data of a range of pollutants. The pollutants that can be measured include, but are not limited to, NOx, S02 CO, 03, VOCs, PM10, PM2.5, Carbon Black, Hg, Benzene etc. The air quality is continuously sampled and measured on-line and in real-time.
The real time data is stored, typically as one hourly averages, with data being collected remotely from individual monitoring stations by telemetry. Remote control of the monitoring and data system is also possible as is remote diagnostics for most of the analyzers.
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