SYSTEM FOR TRANSFORMERS ONLINE DIAGNOSTIC AND OIL PROCESSING TOR-5
Diagnostic mode
GlobeCore technology for diagnostic evaluation of transformers status is based on measuring some parameters by means of sensors, calculating other important parameters in reliance on these data, and transmitting all the results to the end user.
Interpretation of the results of online measurements of transformer parameters is available in the web application. We can always see what range measured and calculated values are within. But critical damage can develop in a matter of days and hours, and if the deterioration of parameters is observed on a day off work, or the transformer is very far away, you may never get a change to purify and dry the oil. Specifically for such cases, TOR-5 unit is equipped with a system for drying and filtering the insulating oil. When the transformer parameters reach the values set by the operator, TOR-5 automatically switches from the diagnostic evaluation mode to the insulating oil filtration and drying mode.
Diagnostic mode
GlobeCore technology for diagnostic evaluation of transformers status is based on measuring some parameters by means of sensors, calculating other important parameters in reliance on these data, and transmitting all the results to the end user.
Interpretation of the results of online measurements of transformer parameters is available in the web application. We can always see what range measured and calculated values are within. But critical damage can develop in a matter of days and hours, and if the deterioration of parameters is observed on a day off work, or the transformer is very far away, you may never get a change to purify and dry the oil. Specifically for such cases, TOR-5 unit is equipped with a system for drying and filtering the insulating oil. When the transformer parameters reach the values set by the operator, TOR-5 automatically switches from the diagnostic evaluation mode to the insulating oil filtration and drying mode.
GlobeCore monitoring technique is based on using the relative humidity of insulating oil. Water can enter the transformer from the environment, for example, due to seal leaks; therefore, TOR-5 system measures the following parameters by means of sensors once a minute, 24 hours a day, 7 days a week:
- temperature of transformer top and bottom oil;
- active water in transformer top and bottom oil;
- relative humidity of transformer top and bottom oil;
- ambient air temperature;
- relative humidity of ambient air.
A high-precision hydrogen sensor is additionally used as an indicator of transformer malfunctions. Hydrogen is formed in oil as one of the first gases already at the temperature of 150 degrees Celsius and accounts for up to 59% of all the gases released during the decomposition of oil molecules. Therefore, the content of this gas in insulating oil is a rather informative parameter for diagnostic evaluation of possible transformer malfunctions, in particular, occurring partial discharges. With partial discharges in oil, the weakest hydrocarbon bonds are broken through ionization with accumulation of hydrogen.
All measured data are transmitted via the Internet to a cloud server using a high-speed router. The router contains specialized software run in Linux environment. This software receives several analyzed parameters from sensors via Modbus/RS485 protocol and transfers them via HTTPS protocol. The router is connected to the Internet via any 2G/3G/LTE mobile network available at the location of the equipment.
On the cloud server, other parameters are calculated using special formulas and give more complete information about the transformer status:
- water content in transformer top and bottom oil;
- water content in solid insulation at transformer top and bottom;
- breakdown voltage of oil;
- oil quality index.
Thus, the quantity of information parameters available in TOR-5 system is greater than the quantity of installed sensors due to the application of calculation algorithms. More parameters allow going beyond the scope of simple assessment of water content in the transformer and proceeding to assess various risks associated with the presence of water in oil and paper insulation.
Oil Drying and Filtration mode
In this mode, the oil is taken from the transformer bottom; next, it is sequentially pumped through a filter with the filtration fineness of ten microns and three adsorbers (sorbent cartridges) each of which contains 15 kilograms of aluminosilicate sorbent consisting of granules with a microporous structure. Using a filter, mechanical impurities are removed from the oil, and the aluminosilicate sorbent absorbs and retains water molecules in its crystals. After that, pure and dry oil is fed to the top of the transformer tank. The process of absorbing and entrapping the water does not require heating the oil and runs with the same efficacy regardless of the temperature. The pumping speed is 30 liters per hour, and the oil is processed without disconnecting the transformer, regardless of the time of day, weather conditions, or the presence of maintenance staff.
After the oil parameters return to normal, TOR-5 unit automatically switches back from the oil filtration and drying mode to the parameters monitoring mode.
Due to the fact that the water in the transformer is in a state of constant migration from oil to paper insulation and vice versa, the circulation of oil through the adsorbers allows removing the water not only from the oil, but also from the paper insulation. Thus, owing to TOR-5 system, the transformer remains dry throughout its service life.
Standard Complete
A standard complete set of TOR-5 system includes:
- transformer parameters monitoring section (two sensors for moisture content and active water measurement, a hydrogen sensor, a top oil temperature sensor, a relative humidity and ambient temperature sensor, a heater for creating the temperature difference between input and output oil, a high-speed router);
- transformer oil processing section (three sorbent cartridges, a transfer pump, a pressure sensor for monitoring the filter clogging rate, an electronic oil meter, a float sensor for oil spill in the tray, an oil level sensor in the transformer tank);
- web application that is hosted in a cloud service or on a virtual server in Linux environment. The web application receives data from TOR-5 units, accumulates them in the database, performs the necessary calculations, and provides the user on a real-time basis with the initial parameters received from the sensors and the parameters calculated using the formulas.
TOR-5 system is connected to the transformer using hoses or pipelines. The connection is made by one person via camlock quick couplings in a few minutes. Connection to radiator fins is also possible. TOR-5 can be connected to any oil-filled transformer regardless of brand and operational life.
- Low relative cost of the system. The price of new transformers and the losses caused by emergency failure of operating transformers reach hundreds of thousands and millions of dollars. And the cost of TOR-5 system accounts for only a small part of those expenses which makes the purchase and usage thereof a profitable investment.
- The system solves three challenges: determining the important parameters of transformers online, filtering and drying the insulating oil, as well as informing the user about its operation and the operation of the transformer in a prompt manner.
- TOR-5 system is suitable for servicing new and aged oil-filled transformers, as well as multipurpose transformers.
- Compact size. The system consists of the minimum number of components required for efficient operation which are placed in a single 115 centimeters wide, 208 centimeters high, and 35 centimeters long housing.
- The service life of the system is commensurate with the service life of the transformer due to the reliable protection of all components from damage and atmospheric precipitation.
- Convenient use of the web application. The web page displays a list of substations and transformers for each substation. The program also includes display of transformers on the map with representation of measurements and calculations in the form of graphs and charts. By choosing an object, one can get complete information about the oil condition for the entire period after installing TOR-5 system near the transformer, or for a selected period of time.
- Easy connection. After the preparatory stage, it takes a few minutes to connect the system to the transformer.
- The oil is processed automatically without disconnecting the transformer.
- Remote monitoring. Even while on vacation, the head of the electric power company or an employee of the service subdivision can log into the system from any workplace and get to know the transformer fleet status without awaiting the laboratory result and leaving for the equipment operation site.
- More complete information and assessment of transformer status change dynamics. Due to ongoing data acquisition, the transformer status change dynamics can be assessed which makes TOR-5 system more informative compared to periodic laboratory analyses.
- Extended service life of new transformers for decades. With regard to older transformers, TOR-5 system makes it possible to determine based on oil aging dynamics when it is necessary to carry out repairs or to take the equipment out of operation in proper time avoiding an emergency.
- Increased timing between maintenance services for transformers due to preventive processing of insulating oil.
- Saved money due to ceasing to use laboratory analyses when obtaining more complete and immediate information of transformer status.
- Reduced expenses for insurance of transformers. The failure probability of a transformer equipped with TOR-5 system is considerably lower than that of a transformer not equipped with this kind of system. In such cases, an insurance policy usually costs less.
- Decreased number of skilled staff involved (sampling specialists, laboratory employees, operators of insulating oil filtration and drying units, etc.).
- Environmental conservation. A failed transformer causes an environmental disaster through a spill, fire, and even an explosion. TOR-5 system by GlobeCore allows avoiding these situations and preventing the environmental pollution associated with transformer emergencies.
TOR-4 TRANSFORMER STATUS MONITORING SYSTEM
GlobeCore has developed TOR-4 system for online monitoring of power transformer status. It is used to carry out transformer monitoring for special-purpose (traction, mine, marine, electric furnace, wind turbine, and other) transformers, as well as for transformers with a long service life.
GlobeCore TOR-4 system performs the following functions:
- Online transformer oil analysis.
- Convenient informing of users about the current transformer status via a web-interface.
- Transformer oil drying when the moisture content exceeds the specified limits.
TOR-4 system remains near the transformer and is connected thereto using pipelines. All important components of the system, including sensors, are located inside the housing; the IP rating of the housing allows operating the transformer online monitoring equipment outdoors.
Approaches to classification of transformer status monitoring methods
There exist various approaches to classification of transformer status monitoring methods which are determined by the attribute underlying the classification. We highlight direct and indirect, as well as offline and online diagnostic evaluation methods.
Direct methods are applied to the transformer component the status of which must be diagnosed. For example, in order to become aware of the windings insulation status, the insulation resistance is measured using a megohmmeter. Indirect diagnostic evaluation methods use intermediate components of a transformer, or an intermediate information medium. Insulating oil is typically used as an information medium. In this case, first, transformer oil diagnostic evaluation is performed, and next, a conclusion is made about the presence of certain defects in the transformer based on the results thereof.
Online diagnostic evaluation methods are implemented using the instruments and devices connected directly to the transformer, “reading” the information, and transmitting it to the end user. Offline methods are implemented using the laboratory instruments that handle previously taken samples of insulating oil or other samples (paper insulation pieces, etc.).
Chromatographic analysis of transformer oil
Chromatographic analysis is one of the most commonly used methods for diagnostic evaluation of transformer status. In this case, oil is a carrier of useful information represented by concentrations of dissolved gases which begin to evolve with development of defects. The concentrations of hydrogen, acetylene, ethylene, methane, ethane, carbon monoxide and dioxide are used for diagnostic evaluation.
There exist many techniques for interpretation of measurement and defect detection results which are implemented either by computation and analysis or by graphics. In the first case, the numerical ratios of different gas pairs are found, and a conclusion is made about the presence and type of defect depending on obtained values. The classic graphic technique is the Duval Triangle according to which a triangle is first constructed; next, it is divided into several sectors, and the type of defect is determined by the sector where the point plotted on the basis of measured gas concentrations gets in.
Chromatographic dissolved gas analysis is a powerful diagnostic evaluation technique, but implementing it requires special laboratory equipment that allows extracting gases from oil (analyzers).
Transformer oil monitoring based on results of laboratory analyses
In addition to the information function, oil performs two other system-forming functions in a transformer; these include removal of heat from heating parts and insulation of current-carrying elements. Therefore, it is also important to monitor the condition of oil. Laboratory methods are mostly used for that purpose.
First, oil samples are taken from the transformer; next, the samples are delivered to the laboratory where they are tested using special instruments. In order to understand the condition of oil, its breakdown voltage, dielectric loss tangent, acid number, interfacial tension, moisture and mechanical impurities content, color, and other parameters are determined.
The main disadvantage of laboratory methods is that results take long to come. In modern transformers, serious damage can develop in a matter of days or hours; therefore, after obtaining a laboratory analysis report, one can manage to perform the required transformer maintenance not in every instance. The principle of periodic sampling where analyses are carried out regardless of the condition of oil does not prove its worth either. Every owner is interested in cheap transformer maintenance and cost reduction for transformer oil analysis; thus, it is advisable to pay attention to online diagnostic evaluation systems.
TOR-4 transformer monitoring systems
Transformer online monitoring is an excellent alternative to long-term transformer oil analysis. The advantages of this type of monitoring are obvious:
- more complete insights into the transformer status which are difficult to get by means of laboratory tests only;
- taking samples is not required which reduces the manual labor input;
- saving money on orders for analyses placed with private laboratories.
GlobeCore has developed TOR-4 system for online monitoring of power transformer status. It is used to carry out transformer monitoring for special-purpose (traction, mine, marine, electric furnace, wind turbine, and other) transformers, as well as for transformers with a long service life.
GlobeCore TOR-4 system performs the following functions:
- Online transformer oil analysis.
- Convenient informing of users about the current transformer status via a web-interface.
- Transformer oil drying when the moisture content exceeds the specified limits.
TOR-4 system remains near the transformer and is connected thereto using pipelines. All important components of the system, including sensors, are located inside the housing; the IP rating of the housing allows operating the transformer online monitoring equipment outdoors.
Transformer parameters monitored by TOR-4 system
Using sensors, TOR-4 system measures the following parameters once a minute:
- temperature of transformer top and bottom oil;
- active water in transformer top and bottom oil;
- relative humidity of transformer top and bottom oil;
- ambient air temperature;
- relative humidity of ambient air.
Apparently, measurement of humidity is accepted as a baseline parameter. It is associated with the fact that wet transformer prevention is one of the main tasks in servicing.
Parameters evaluated by TOR-4 system
All measured data are transmitted via the Internet to a cloud server where additional parameters are calculated:
- water content in transformer top and bottom oil;
- water content in solid insulation at transformer top and bottom;
- breakdown voltage of oil;
- oil quality index.
Thus, the quantity of information parameters available in TOR-4 system is greater than the quantity of installed sensors due to the application of calculation algorithms.
The oil quality index is a comprehensive indicator that characterizes the overall condition of transformer oil. This indicator correlates well with the degree of oil aging; therefore, it can be deemed as an alternative to online measurement of acidity. The oil quality index ranges from zero to one. A range value of 0.8–1 corresponds to a good condition of transformer oil, and a range value of 0–0.2 corresponds to bad, aged oil.
Features of TOR-4 system web interface
All the measurement and calculation results are displayed on a web page which can be accessed with a password, and the number of users with access is unlimited. The system is additionally protected against hacking by encryption, so the receipt of information by third parties is prevented.
Data visualization has been made user-friendly: the web page displays a list of substations and transformers of each substation. The program also includes display of transformers on the map with representation of measurements and calculations in the form of graphs and charts. Having chosen an object, one can get complete information about the condition of oil for the entire period after installing TOR-4 system near the transformer, or for a selected period of time.
Even while on vacation, the director of the electric power company or an employee of the service subdivision can log in the system from any workplace and get to know the transformer fleet status without awaiting the laboratory result and leaving for the equipment operation site. Due to ongoing data acquisition, the transformer status change dynamics can be assessed which makes TOR-4 system more informative compared to periodic laboratory analyses. And even if there is no Internet connection for some reason, not a single measurement will be lost: all the data are saved, and when the connection is restored, they are transmitted to the server in batch mode.
Transformer online drying by means of TOR-4 system
When the moisture content of oil reaches the specified value, TOR-4 system automatically switches from diagnostic evaluation to oil processing mode.
Oil processing includes:
- filtration — a filter with the filtration fineness of 10 microns is installed;
- oil drying — the water is absorbed by a sorbent while the oil is sequentially pumped through adsorbers.
After the parameters are restored, TOR-4 unit automatically switches between oil processing and diagnostic evaluation modes.
Oil processing by pumping the oil through sorbent-filled adsorbers may be deemed as alternative transformer drying. In this case, oil is taken by TOR-4 system from the bottom point and returns dried to the transformer top point. Due to the fact that the transformer water constantly migrates from oil to paper insulation and the other way around, oil circulation through adsorbers allows removing the water not only from oil, but also from paper insulation. Thus, continuous transformer drying is achieved. TOR-4 system keeps a transformer dry throughout its service life.
Additional features — hydrogen stream gas analyzer
Unlike thermal vacuum drying, sorbent-based drying does not influence the dissolved gas composition and amount in oil. Therefore, sensors which are used to determine, for example, hydrogen content in oil can be optionally added to TOR-4 system.
Continuous online gas analysis will allow expanding the capabilities of TOR-4 system and make the diagnostic evaluation of transformer status more complete and informative.
Benefits of using TOR-4 system
- extended service life of transformers due to continuous monitoring of important parameters and timely processing of oil online;
- increased timing between maintenance services for transformers due to periodic processing of oil in automatic mode;
- saved money due to ceasing to use laboratory analyses;
- reduced expenses for insurance of transformers;
- decreased number of qualified staff involved;
- environmental conservation due to preventing the transformer emergencies associated with splashing of insulating oil.