WO2003075294A1

WO2003075294A1 - On-line detection and measurement system for gases in oil-filled electrical equipment

Info

Publication number: WO2003075294A1
Application number: PCT/IN2002/000127
Authority: WO
Inventors: Anil Kohli
Original assignee: Anil Kohli
Priority date: 2002-03-01
Filing date: 2002-06-04
Publication date: 2003-09-12
Also published as: AU2002311624A1

Abstract

A system for on-line detection and measurement of evolved gases and/ or composite hydrocarbons in the oil filled equipments wherein the gases coming out of the top cover plate are detected by a sensing device provided with a gas trapping device and permeable membrane for stopping the flow of oil particles present in the evolved gases. The sensing device is provided with an amplifier and a programmable device for analysing, reporting and corrective actions.

Description

ON-LINE DETECTION AND MEASUREMENT

SYSTEM FOR GASES IN OIL-FILLED

ELECTRICAL EQUIPMENT

FIELD OF THE H ENT1ON

The present invention relates to a system for on-line detection and measurement of evolved gases in fluid filled equipment and giving a signal or indication visually, numerically to rectify the defect before the equipment is damaged. More particularly the present invention relates to a system for on-line detection and measurement of evolved gases in oil filled equipments like electrical and loco transformers .

The main embodiment of the invention resides in the process and apparatus of on-line detection and measurement of key evolved gases produced under the fault condition namely; Acetylene (C₂H₂), Hydrogen (H₂), Methane (CH₄), Ethylene (C₂H₄), Ethane (C₂H₆), Carbon-Monoxide (CO), Carbon dioxide (CO₂) and/or composite hydrocarbons in an oil filled equipment.

Another embodiment of the invention resides in the total transformer monitoring system.

Another embodiment resides in detection and measurement of the gasses continuously through the gas permeable but fluid impermeable membranes allowing the gasses evolved under the fault condition to reach selective gas sensors located in the sensing apparatus.

Yet another embodiment resides in programming a programmable device to acquire the data on real time basis to measure each gas concentration, its rising trend, detect rapid change, compare the various combinations of varying concentration of fault gases and also to other factors related to temperature, load, pressure and provide output signals indicating fault initialization, fault confirmation, type of fault, aging process and system error fault thus representing the condition of an equipment. Whereby the computer processes the signals representing the equipment condition and providing audio & visual alarm levels, remote alarm over telephone, trending, historical logging, statistically data analysis, dial-in option and communication over internet.

The object of the invention is to provide an advance, automated, on-line, reliable and quick process and apparatus of fault monitoring for the fluid filled systems by creating an evolved gas trapping point between the top cover plate of the equipment and the conservator tank where a sensing apparatus for gas sensors and the transmitter are provided.

It is also the object of the present invention to provide detailed fault diagnosis including fault initialization, fault confirmation, type of fault, aging process and system error fault. The internal faults namely arcing, sparking, corona, partial discharge, hot spot, hot metal, overheating and insulation failure are also detected.

BACKGROUND OF THE INVENTION

Power transformers are a key factor in the overall availability of power transmission system. The reliability of the transformer, including the insulation and cooling system, and the maintenance required during its useful life have a significant impact on availability.

It has long been recognized by the electrical industry that abnormal electrical and thermal stresses in electrical apparatus are invariably accompanied by degradation of the surrounding insulating material. In oil/ paper insulating system, this degradation is accompanied by the production of a number of gases. These are principally Acetylene, Hydrogen, Methane, Ethylene, Ethane, Carbon- Monoxide, Carbon dioxide. The rate of generation of these gases and their composition is a function of fault severity, i.e. rate of energy dissipation and temperature and of fault type (arcing, sparking, corona, partial discharge, hot spot, etc.)

Conventionally, the gas operated Buchholz's relay has been used which operates the alarm at approximately 165 cc volume irrespective of gas/ air. The main disadvantage of detection of the fault at this stage is that the equipment may already been damaged and the user is left with a little or no option either to replace or repair, followed by high down time and production loss.

However, it has also been recognized that reliable detection of fault gases, before the generation rate becomes large enough to activate the Buchholz's relay, can provide early warning system of incipient fault at initial stage of development.

Dissolved gas analysis in the oil is to detect an incipient fault inside oil filled equipments mainly transformers has been a normal industry practice. Various types of dielectric or excessive heating problems break down the insulating oil and solid materials into characteristic gases that dissolve in the oil. It has been a practice in the industry for users to take periodic oil samples from transformers for testing in a laboratory to identify developing operating problems. Considerable efforts over the years have gone into trying to categorize certain gases and ratios of these gases to interpret the oil samples and diagnose problems. Because of high variability between different samples, different laboratories and different lab tester, it is generally considered an "art" subject to different diagnosis from different laboratories.

So far, incipient fault in oil filled equipment/transformer is mainly based upon the dissolved gas analysis carried out either in field or in laboratory. Whereas, evolved gas based on-line equipment is the step forward to fault monitoring and that too on real time basis. Even though the evolved gasses under the fault condition gets dissolved during the course of time based upon various factors such as temperature, pressure and above all the solubility level of each gas under the subject matter. The solubility of gases in oil is proportional to the external gas pressure and it is greater in oils of higher viscosity. For example, Hydrogen is most important gas evolved under the stress condition but has the lowest solubility level of less than 8%. Similarly from evolved gas point of view, other hydrocarbon gasses will be in most cases higher, equal to or with some kind of equilibrium with dissolved gas level under the fault condition. Undoubtedly, by monitoring the evolved gasses in PPM level would leads to much better control of equipment under stress condition, if monitored on real time basis.

Oil being hydrocarbon, Hydrogen is bound to produce under an electrical or thermal stress conditions. Even though from the dissolved gas point of view Hydrogen presence is important for diagnosis any type of fault but from evolved gas point of view it is critical. If insulating oil is subjected to electrical fault such as arcing the following gases are evolved:

Hydrogen: 60 to 80 percent hydrogen gas is produced but less than 8 percent get dissolved in oil due to its poor solubility. Since it is lightest among all, it invariably reaches to the gas trapping point indicating fault condition.

Acetylene: 10 to 25 percent acetylene gases are produced. An arc under insulating oil generates acetylene gas along with much larger quantity of hydrogen.

Methane: 1.5 to 3.5 percent methane gas is produced. Ethylene: 1.0 to 2.9 percent ethylene gas is produced. In this case, Carbon Dioxide & Carbon Monoxide are absent.

Key fault gasses:

The following concentration of key fault gasses in gas and oil phase equivalent

S.N. Gas GAS Phase(PPM) OIL Phase Equivalent

(PPM) 1 Hydrogen 200 - 50,000 10 - 2,100

2 Acetylene 10 - 50,000 10 - 47,000

3 Methane 200 - 50,000 70 - 17,000

4 Ethylene 5 - 50,000 7 - 68,000

5 Ethane 5 - 50,000 10 - 100,000 6 Carbon Monoxide 15 - 50,000 5 - 5,100

Note: Conversions were made using Ostwald Coefficients at 25 degree C.

Gasses diffuse much faster throughout gas than through fluid. Acetylene and other gases produced under the fault condition rides up with the hydrogen bubbles and therefore will be present within composite gases evolved and trapped position, where an apparatus is installed for quickly sensing the selective gas concentration, its rising trend, detect rapid change, compare the various combinations of varying concentration of fault gases for indicating the type of fault with programmable computer. The computer software can also be worked as analyst of various kinds of faults namely general violation level, thermal fault violation level, electrical fault violation level, aging / insulation violation level based upon the kind of gases and other key parameters such as oil temperature, winding temperature, load and pressure etc.

General violation level is defined in case of increasing trend of hydrogen gas together with and without any or multiple parameters from oil temperature , winding temperature, load & pressure levels. The hydrogen gas is bound to produce under the general stress condition in excess of load levels. Excess load conditions over a period will lead to increase other parameters such as oil and winding temperature, pressure & load . In case of aged / old equipment general violation needs to be kept under control and if taken care it may leads to longer life also.

If insulating oil is overheated, hydrocarbon vapors notably Ethylene, Ethane, Methane and Hydrogen are evolved at temperature up to 500°C. This type of mixture results come from the thermal decomposition of oil. Partial discharge is generated in transformers due to poor impregnation or cavities in the insulation or electrical over stressing of the insulation. The main gases evolved are Hydrogen and Methane. Local overheating between 150°C and 300°C occurs due to magnetic losses and insufficient cooling. Local over heating between 300°C and 1000°C results because of high circulating currents in the core. The shorting links between the core laminates leads to the local overheating to temperatures beyond 1000°C. Up to 300°C, the unsaturated hydrocarbons like ethylene are generated. The formation of ethylene reaches a maximum at 700°C. Above 1000°C little acetylene is also produced. Therefore, thermal violation level is indicated if any two or more combination of gases in increasing trend out of Hydrogen, Methane, Ethylene, Ethane are observed or even any one gas out of Methane, Ethane and Ethylene is found with increasing trend.

Acetylene is nearly always possible symptom of electrical faults such as arcing, sparking, partial discharge, corona, inside the equipment and can be ascertained if increasing trend is observed. Acetylene gas together with or without any hydrocarbon gas evolved is indicative of electrical fault violation level.

In any Electrical equipment, most important part of it is a insulation which is of prime concern and represents the life of an equipment. If insulation fails, the equipment also fails. More particularly in case of oil filled transformer which mainly comprises of core & winding and insulation material such as paper, varnish / press board and insulating oil, etc. Under normal aging process due to deterioration of insulation material Carbon Monoxide and Carbon dioxide are formed. If cellulose is overheated, in a closed system and gases are collected and analyzed it is found that Carbon dioxide & Carbon Monoxide are present at temperature as low as 140°C. In case of Pyrolysis with cellulosic material, it would be observed that on heating it releases water, Carbon dioxide and carbonaceous decomposition products in the form of tar or coke. Which means primarily Carbon Monoxide and Carbon dioxide are formed. Severe overheating leads to formation of water and carbonaceous matter. Aging/insulation faults is defined as increasing trend of Carbon Monoxide and Carbon dioxide together with and without other parameters which are formed by thermal aging of paper. Suggestive Type of Violation/ Faults based upon various Evolved gases, etc.

US Patent No. 3,559,457, Collins, 1971 , describes a hydrogen detector for use in a transformer tank, which includes a tube, formed of palladium alloy, which will expand in the presence of hydrogen. It appears that this detector must be used in gaseous environment, such as in the nitrogen cushioned over the oil insulator in a transformer. It is not believed that the device shown in this patent could be utilized in oil sealed transformer to detect dissolved hydrogen.

US Patent No. 3680359, Lynch, 1972 the monitor described seems limited to gas cushioned transformers and is based on detection of hydrogen by measurement of the thermal conductivity of gas which comprises the gas cushion. The Lynch type of monitor does not appear to be suitable completely for oil filled apparatus such as conservator and diaphragm sealed power transformers. US patent No. 4,654, 806 describes a microprocessor based transformer monitoring system wherein various parameters related to transformers load and condition are periodically measured. However there are no provisions in the system to use the measured parameters for fault diagnosis.

US Patent No. 5,659,126, Milton Farber, 1997 describes a method for monitoring dissolved gases in the insulating oil supply of an electrical transformer in which a blanket of gas containing a fault gas is present in the headspace above the insulating oil supply contained in the transformer .The method includes transferring a sample of the gas from the headspace to a gas chromatograph instrument, and measuring by gas chromatograph techniques the gas concentration level of the fault gases contained in the gas sample. The output from the gas chromatograph is processed by a computing device, which calculates the related gas concentration level of the fault gases present in the oil supply. The problem with the measurement of dissolved gases is that there are many factors, including temperature, pressure, existing degree of saturation, and the solubility of each gas at different conditions .It is difficult to sense an unchanging gas condition because of the dynamic change in gas distribution through out the transformer.

US Patent No. 6,289,716, 2001 describes a method for monitoring fault gases in head space of a transformer and indication of transformer conditions The method includes periodically transferring a sample of gas to a gas analyser. However no system was provided for detection and an on-line analysis of the fault gas detection and for taking corrective measures instantly to save damaging of the equipment. Thus, there always existed a need for a fault gas detection which can analyse fault gases truly on-line so as to indicate at the time of fault initialization and also the type of fault at a reasonably low cost and without time delay caused by oil sample extraction, analysis and complex equipment used.

The present invention provides these desired benefits in the form of fault gas detection system with programmable computer, using an evolved gas-trapping point between the top cover plate of equipment up to the conservator tank where an apparatus comprising the gas sensors along with transmitter is to be installed. The programmable computer acquires the data from the gas sensors on real time basis and measures concentration of each gas evolved, its rising trend, detects rapid change, compares the various combinations of varying concentration of fault gases and also the other factors related to temperature, load, pressure and provide output signals indicating fault initialization, fault confirmation, type of fault, aging process and system error fault are also monitored, thereby offering pro-active decision-making tool for the industry.

The gas bubbles rise to the top and enter the gas trapping point.

By monitoring these key evolved gases in the gas trapping point a warning signal can be generated thereby avoiding catastrophic damage to the equipment and associated system. The gases most likely transfer from rising oil to the gas trapping position first and then back into the oil at the interface. Interfacial transfer takes place in accordance with the relative saturation Ostwald coefficients for individual gases. The close monitoring of evolved gasses at the trapping position for rapidly increasing levels of acetylene and hydrogen would provide an indication of arcing and could be used to generate a dangerous condition and/or a trip signal The gas trapping mechanism is provided in a pipeline which is connected to the top cover plate of the oil filled equipment in upward direction below the oil filled level in the conservation tank. The bubbles of the fault gases above the headspace travel through the pipeline having an air gap of the diameter of about 20-35% of the diameter of the pipeline by a metal barrier provided at the angle between 40-60°. Thereafter another barrier is placed oppositely parallel to the first barrier for further restricting the flow of evolved gases and directing them to a vertically inclined pipe which is in line with the top barrier. There is provided a release valve to release the trapped air if required without removing the sensing apparatus.

Accordingly the subject invention relates to a system for on-line detection and measurement of evolved gases such as Acetylene (C₂H₂), Hydrogen (H₂), Methane (CH₄), Ethylene (C₂H₄), Ethane (C₂H₆), Carbon- Monoxide (CO), Carbon dioxide (CO₂) and/or composite hydrocarbons in the oil filled equipments comprising:

-an oil filled equipment provided with the top cover plate having means for outflow of evolved gases to a gas trapping device for trapping evolved gases provided between the conservator tank and top cover plate,

-a conservator tank connected with the gas trapping device to maintain the level of oil in oil filled equipment,

-an air release valve provided at the top end of the gas trapping device for release of evolved gases,

-means for controlling the flow of oil present in the evolved gases from entering the sensing apparatus,

-means for sensing and characterization of the evolved gases coming out through the air release valve, -means for amplifying the output signals coming out of the sensing means and transmitting it to the monitoring means,

-means for measuring and displaying the concentration of evolved gases with programmable audio and visual alarm settings, -means for sending the signals to a programmable device for analysing, reporting and corrective actions.

The embodiment of the invention resides in a system for on-line detection and measurement of evolved gases such as Acetylene (C₂H₂), Hydrogen (H₂), Methane (CH₄), Ethylene (C₂H₄), Ethane (C₂H₆), Carbon- Monoxide (CO), Carbon dioxide (CO₂) and/or composite hydrocarbons on the oil filled equipment comprising:

-an oil filled equipment provided with the top cover plate having means for outflow of evolved gases above/through the headspace to a gas trapping device for trapping evolved gases,

-a conservator tank provided with a hollow pipe at its lower end portion wherein the other end of the pipe is placed above the top cover plate of the oil filled equipment,

- means for controlling and directing the flow of evolved gases coming out of the equipments top plate in a unilateral direction,

- means for directing the flow of evolved gases from gas trapping device to a sensing apparatus,

-means for controlling the flow of the unwanted gas to the sensing apparatus, -means for controlling the flow of oil present in the gaseous mixture from entering the sensing apparatus,

-means for sensing and characterization of the evolved gases received from the gas trapping point,

-means for amplifying the output signals coming out of the sensing means and transmitting it to the monitoring means, -means for measuring and displaying the concentration of evolved gases with programmable audio and visual alarm settings,

-means for sending the signals to programmable computer for analysis, reports and corrective actions,

A more complete appreciation of the invention and the attendant advantages thereof will be more clearly understood by reference to the accompanying drawings, which are for illustrative purposes, hence the same should not be construed to restrict the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig.1 depicts a schematic diagram of Loco Transformer with created gas trapping point with installed apparatus.

Fig.2 depicts a schematic diagram of Transformer with located gas trapping point with an apparatus

Fig.3 depicts a schematic illustration of a Total Transformer Monitoring system.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 is a simplified block diagram of a locomotive transformer (1), in which insulating oil is present. In order to create a gas trapping point (7) above the headspace but between the top cover plate of the fluid filled equipment and below oil filled level of the conservator tank (6) a hollow pipe made of metal in two or more parts connected to each other by means of a sealing joint or joints. The hollow pipe is connected to the top plate of the transformer(l) at one end and to the conservator (6) on the other. An inclined metal barrier (4) made of soft steel or steel is fixed inside the said hollow pipe at the angle of 40-60° having an air gap between its free end and wall of the hollow pipe Another inclined metal barrier (5) is configured oppositely parallel to the said metal barrier (4) in the said hollow pipe for directing the gas bubbles (3) flow in unilateral direction . A vertically inclined pipe having the gas trapping point (7) is placed adjacent in-line to the top barrier near the further end of the said hollow pipe to which the sensing apparatus(δ) is removably attached. A polymeric membrane is provided at the bottom end of the sensing apparatus to stop the flow of the fluid and only the gases are allowed to pass. The sensing apparatus comprises of a number of electrochemical sensors. These sensors are connected to the transmitter. An amplifier is provided at the top end of the sensor to amplify the signals. From main oil filled equipment (2) above the headspace through a hollow pipe in upward direction, gas bubbles(3) are directed to travel through the air gap of preferably about 25-30% of the width of the said hollow pipe to reach near the sensing apparatus (8) through a laterally connected pipe at the gas trapping point (7). An air release valve is inserted before the sensing apparatus (8) to make a provision for releasing the trapped air if required without removing the sensing apparatus (8). The output signals from the sensing apparatus (8) are carried by twisted and sheathed cable (9).

In fig. 2 a conventional transformer (11) is shown. Main tank (10) filled with insulating oil. Where a gas trapping point located at air vent valve position of gas operated Buchholz's relay (12) is used to mount the sensing apparatus (14). This gas trapping point is located well above the transformer main tank cover plate above the headspace but below the oil filled conservator tank (13). Fig.3 is a schematic illustration of a Total Transformer Monitoring system. Both type of above transformers used in fig.1 and fig. 2 are connected to this system. Where the sensing apparatus (8 & 14) is normally in close contact with the fluid. In between a polymeric membrane is used which is impermeable to fluid but permeable to gasses so as to allow the evolved gasses to reach gas sensors inside the apparatus. The gas sensors namely Acetylene, Hydrogen, Methane, Ethylene, Ethane, Carbon Monoxide, Carbon Dioxide and/or Combustible Hydrocarbons are very low PPM level sensors for detecting and measuring any changes under fault condition. The sensors used for accurate measurement of these gases, is basically electro-chemical sensors generating output signals in micro amperes equivalent to specific gas concentration in PPM. These sensors output is given to transmitter for carrying these signals noiselessly to distant monitoring by amplified the output signal in the range of 0 to 5 volts or industrial standard 4 to 20 m A. The transmitter and sensors are mounted inside the sensing apparatus(δ). The output signal from the sensing apparatus(δ) is carried by twisted and sheathed cable (9 & 15).

The sensing apparatus (8 & 14) enclosure is made of metal generally stainless steel housing where the bottom is hollow pipe with male threaded suitable to be mountable on air trapping position (7) either at Air vent valve of Buchholz's relay or so. Through the hollow pipe fluid is allowed to reach inside the apparatus up to the polymeric membrane which is gas permeable but fluid impermeable . This polymeric membrane serves the purpose of keeping the fluid up to that level and allowing evolved gasses to pass through it The gasses thus evolved are exposed to selective gas sensors responding to Acetylene, Hydrogen, Methane, Ethylene, Ethane, Carbon-Monoxide, Carbon Dioxide and/or composite Hydrocarbons. The sensor used are preferably electro- chemical sensors which are more accurate and reliable for detecting low PPM level of gas volume. The output signal from such sensor is amplified with the help of built-in Transmitter fitted near the sensor 's output position as close as possible so as to avoid any external interference . Thereafter the amplified output signals from the sensor is connected through multi pin socket provision provided at the top position of the apparatus. The transmitter is required because of low output signal comes from electro- chemical sensor usually in the range of micro amperes to be converted into Industrial standard, i.e. 0 to 5 Volts, 4 to 20 m.A /mV. Whereas, in case of 0 to 5 Volts, 0 volts signifies starting range of sensor and 5 volts represents the end range of sensor. This is required to get the much stable & noise free signals to transmit remotely through twisted and sheathed cable to the customer desired distance unit, through which customer want to communicate through programmable device such as computer/ P.L.C, etc.

The transmitters mounted inside the apparatus (8 &14) are designed for standard two-wire operation suitable for 4-20 mA circuit output and also 0-5 V. The wire (9 & 15) used is twisted and sheathed suitable for carrying output signals to Monitoring unit (16).

The monitoring unit(16) installed near the equipment is used for working independently as standalone to measure and display the gasses concentration with programmable audio & visual alarm settings; low (yellow) alarm for fault initialization, high (red) alarm and error alarm for system mal-functioning The monitoring unit also acts as a source of power supply to transmitter generally upto 24 VDC and also serve the purpose for calibrating the sensor cum transmitter for zero and span adjustment. It also can be independently programmed through P.L.C/Programmable I. Cs for working as standalone, to set to various alarms low/ high /error alarms in shape of visual / audio type with an option to give display reading of each sensor/ channel. These alarms and reading can be carried forward to remote alarm unit at customer specified place through suitable mechanism e.g. relays, communication ports. The same functions can be Remotely (20) monitored at distant place by carrying these signals.

Alternatively through communication port such as RS 232/ RS 485 signals from the Monitoring unit through cables(17) is processed in data acquisition unit (18) where signals are converted from analog to digital or digital to digital for distant transmission and lastly send to computer (19).

By programming a programmable computer (19) to acquire the data on real time basis to measure each gas concentration, its rising trend, detect rapid change, compare the various combinations of varying concentration of fault gases and also to other factors related to temperature, load, pressure through suitable transducers and provide output signals indicating fault initialization, fault confirmation, type of fault, aging process and system error fault thus representing the condition of an equipment. Whereby the computer can process the signals representing the equipment condition and providing audio, visual alarm and/or trip signal levels, remote alarm over telephone, Trending, Historical logging, statistically data analysis, dial-in option and communication over internet. To perform this analysis, a hierarchy of response produced by the transformer monitoring system. The type of response depends on the level of the exceeded threshold in the hierarchy. The range of response produced by the transformer monitoring system includes : data collection and analysis and recommendations for further necessary actions. The computer is programmed to take and record the signal from sensor at certain time frequency i.e. one second onwards . These samples are plotted on the graph/front Screen on real time basis for the last one hour for each sensor/channel. It is also programmed to each sensor specific range and accuracy and tuned as full range between absolute minimum and absolute maximum. Normally two levels low/high alarm levels are users selectable for indication and confirmation of fault for example 20% as low alarm and 40% as high alarm of the full range of a sensor. Further this can be raised, if required.

Periodical data can be reviewed between any date and time i.e. day/week / month can be selectable by user to get plot of the data for detailed analysis. Besides statistically information such as average, maximum, minimum, mean, standard deviation can be programmed and reviewed any time by user. The provision for remote alert through telephonic call to the user with pre-recorded telephone numbers and message can be activated in case of non acceptance of audio / visual alarms. Computer will start dialing on pre-recorded telephone number through built in fax modem to any distant location on the globe. Similarly, it can also programmed to send the e-mails as remote alert The system is connected with local area network with any number of monitoring clients for viewing the data remotely and also capable of communicating through internet/ intranet for two way communication for monitoring the health of equipment.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

1. A system for on-line detection and measurement of evolved gases such as Acetylene (C₂H₂), Hydrogen (H₂), Methane (CH₄), Ethylene (C₂H₄), Ethane (C₂H₆), Carbon-Monoxide (CO), Carbon dioxide (CO₂) and/or composite hydrocarbons in the oil filled equipments comprising:

-means for measuring and displaying the concentration of evolved gases with programmable audio and visual alarm settings,

-means for sending the signals to a programmable device for analysing, reporting and corrective actions.

2. A system for on-line detection and measurement of evolved gases such as Acetylene (C₂H₂), Hydrogen (H₂), Methane (CH ), Ethylene (C₂H₄), Ethane (C₂H₆), Carbon-Monoxide (CO), Carbon dioxide (CO₂) and/or composite hydrocarbons on the oil filled equipment comprising: -an oil filled equipment provided with the top cover plate having means for outflow of evolved gases above/through the headspace to a gas trapping device for trapping evolved gases, -a conservator tank provided with a hollow pipe at its lower end portion wherein the other end of the pipe is placed above the top cover plate of the oil filled equipment,

- means for controlling and directing the flow of evolved gases coming out of the equipments top plate in a unilateral direction, - means for directing the flow of evolved gases from gas trapping device to a sensing apparatus,

-means for controlling the flow of the unwanted gas to the sensing apparatus,

-means for controlling the flow of oil present in the gaseous mixture from entering the sensing apparatus,

-means for sending the signals to programmable computer for analysis, reports and corrective actions.

3. A system for on-line detection and measurement of evolved gases according to claim 2 wherein the means for controlling and directing the flow of evolved gases are at least a pair of inclined barriers placed parallelly opposite to each other inside the hollow pipe having an air gap between its free end and the wall of the hollow pipe.

4. A system for on-line detection and measurement of evolved gases according to claim 2 wherein means for directing the flow of evolved gases from gas trapping device to a sensing apparatus is an inclined vertically oriented hollow pipe placed adjacent in-line to the top barrier near the further end of the hollow pipe.

5. A system for on-line detection and measurement of evolved gases according to claim 2 wherein the means for controlling the flow of the unwanted gas to the sensing means comprises of an air release valve provided at the further end of the hollow pipe.

6. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein the means of flow of oil present in the evolved gases from entering the sensing apparatus comprise a polymeric membrane permeable to gases and impermeable to fluid provided at the bottom end of the sensing means.

7. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein the sensing and characterization means are electro-chemical sensors generating output signals in micro amperes equivalent to specific gas concentration in PPM at the input end of the sensing apparatus.

8. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein an amplifier is provided at the top end of the sensing apparatus to amplify the output signal.

9. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein the sensing and characterization means are enclosed in a stainless steel housing where the bottom is hollow pipe with male threaded suitable to be mountable on air trapping point.

10. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein the monitoring means is monitoring unit provided at the output end of the sensing means for displaying the type of fault.

11. A system for on-line detection and measurement of evolved gases according to claim 1 or 2 wherein the means for corrective actions are computer aided devices which operate and control the parameters such as general, thermal, electric and aging.