Which transformers are gas relays installed on?

Power oil-filled transformers, which have an expansion tank in their design, with a power of 630 kVA or more, are necessarily equipped with gas protection. The gas relay serves to protect against all types of internal damage, during which flammable gas is released, oil rapidly flows into the expansion tank and oil leaks from the transformer to the outside.

Gas protection of transformers, operating principle of a gas relay

Gas protection for transformers is the most sensitive and versatile protection against internal damage. It is installed on oil-cooled transformers that have an oil conservator.

The principle of operation of gas protection is based on the fact that any damage in the transformer, including increased heating of the oil, leads to chemical decomposition of the transformer oil, as well as organic winding insulation materials, resulting in the release of gas inside the transformer.

This gas affects special gas protection devices, which give a warning signal or shut down the transformer.

Gas protection responds to damage such as an interturn short circuit in the transformer windings, to which differential and overcurrent protection does not respond; since in such cases the magnitude of the circuit current is insufficient to trigger the protection.

The nature of the damage in the transformer and the size of the damage affect the intensity of gas formation. If the damage develops slowly, which corresponds to slow gas formation, then the protection gives a warning signal, but does not turn off the transformer.

Intense and even violent gas formation, indicating a short circuit, creates a signal in the gas protection system of such a magnitude that, in addition to warning, causes the shutdown of the faulty transformer.

Gas protection for transformers also triggers a warning signal when the oil level in the tank drops.

Invention of a gas relay for transformer protection. The Max Buchholz Story

The future inventor of the gas relay was born into a Prussian bookbinder family in February 1875. Since childhood, Max showed interest in mechanical objects. He celebrated his twenty-fifth birthday at the Berlin Engineering University as a first-year student. Upon completion of the educational process, he acquired a specialty in the field of electrical engineering (electrical engineer).

Max Buchholz

In 1901, he received a job at the Siemens & Halske company, which at that time was engaged in the construction of the first European subways. By the way, at the same time, the company’s management enters into an agreement to implement the Pyatigorsk tram line project for almost half a million rubles.

In 1903, Buchholz got a job at the Berlin-Stettin shipping company in the design department of electrical equipment and profile machines. At this place, Max conducts research robots for the first time and discovers his first inventions. In 1910, he received several gold and silver medals at the World Exhibition in Brussels, but the gas relay design was still waiting for its turn...

During the First World War, Buchholz went to the front. In 1917, after a fierce battle, Max was hospitalized. After some time, the inventor was appointed to the post of president of the Kassel Construction Administration, which was soon renamed the “Electric Power Administration”. But the sharp mind of the “Prussian Kulibin” apparently could not adapt to the architectural format, and in 1918 Max moved to the Kassel engineering department as a process engineer. After some time, Buchholz will head this institution, which is considered in some way the cradle of the gas transformer relay.

Prussian Engineering Directorate Kassel

The Prussian Engineering Department was founded to construct mechanical and electrical equipment in the Eder and Diemel dams. During design work, Buchholz increasingly began to notice that transformers were failing after a thunderstorm. The researcher carefully studied the phenomenon and came to the conclusion that critical voltage surges destroy insulating materials on the windings and, as a result, a large amount of gases are released.

The first gas relay, 1925

The problem of protecting a transformer from the “whims of nature” worried many business owners at that time, but by and large did not have effective preventive measures. In 1923, after another breakdown in management, Max comes up with a brilliant idea while taking a bath (according to sources). After making calculations, he consults with his employees and finds the right solution, which apparently pushes Buchholz to create a prototype of the first gas relay.

Soon the inventor registered a patent and in 1928 founded the company “Max Buchholz AG” in Kassel, and the company “Elektrokustos AG” in Zurich. The gas relay was immediately included in transformers produced by the German company AEG and the Swiss company BBC. Contracts with these large companies made the Buchholz name and the gas protection system known throughout the energy industry.

Gas relay - types, internal structure and design

There are three main types of gas relay:

The most common are gas float relays.

The relay body is a cast vessel made of aluminum alloy or cast iron, coated with a protective paint and varnish material with two floats. There are also single-float relays with flange or threaded connection. The relay vessel is embedded in a cut in an inclined pipeline designed to connect the transformer and expansion tanks.

Fig No. 1. Gas relay in transformer design

Gas relay elements

Let us repeat that the gas protection of the transformer is carried out through a relay. In other words, the principle of protection is based on the operation of this device. One of the fundamental elements of protection are flat-bottomed aluminum cups, which carry out a rotational movement in time with movable-type contacts around the axis of the cup.

These wires can become connected to the non-moving ones if the cups begin to fall. And during proper operation (when the oil volume in the relay housing is at an acceptable level), these basic protection elements are held in a certain position in which they do not close any of the contacts.

When the oil level in the casing drops, the cups also begin to fall along with the contacts, which close with other, stationary ones. Moreover, in case of minor damage, only the upper cup will lower, and the closure of its contacts will lead to the fact that the gas protection device of the transformer will only give a signal of a breakdown.

If the intensity of gas formation is high, then the flow of oil and gas will also affect the blade, which, when the contacts are closed together with the lowered cup, will cause a shutdown of the operating transformer.

During normal operation of the unit, the oil speed inside has values ​​of 0.6/0.9/1.2 m/s. This indicator depends on the quality of cooling of the object. When a problem occurs, the response speed of the transformer gas protection takes from 0.05 s to 0.5 s. It can be added that on the territory of the Russian Federation, the gas relay with two spherical plastic floats BF80/Q is most widespread.

Technical characteristics and main indicators of gas relays

Gas protection of transformers, principle of operation

The operation of the float mechanism is based on the principle of hydromechanics. Two mercury relay contacts are attached to the floats; they control the auxiliary current circuits. The float located on top has contacts connected to the signal circuit. The lower contacts located on the lower, second float are included in the transformer shutdown circuit.

Fig No. 2. Float type gas relay

If the transformer has damage inside the housing, as a result of which gases are formed, like decomposition products of transformer oil, they will rise to the oil conservator and enter the gas relay.

Gas or air collects in the upper part of the relay, the transformer oil filling the gas relay vessel will be displaced, the upper float will lower, and the contacts will close, triggering a “signal.” The sound alarm sounds and the control blinker falls out at the substation.

The subsequent further decrease in the level of transformer oil in the tank causes the lower float to lower, and the lower contacts close, triggering the transformer shutdown.

Fig No. 3. Schematic diagram of switching on a gas relay

Rapid gas formation causes oil to flow from the transformer tank into the expander, as a result of which the lower float turns the plate, it overturns, causing the transformer to turn off.

The relay is activated when the oil flow rate through the pipe is 50 cm/sec. The sensitivity of the relay to the oil flow rate is adjustable; for this, the adjusting weight on the graduated plate is set to the appropriate value. The relay is adjustable to operate at any oil movement speed from 50 to 150 cm/sec.

The operation of the relay can be monitored through the viewing window on which the level scale is applied. In the upper window, you can see how much oil is displaced in cm3, the lower inspection window shows the oil level above the upper edge of the throttle washer outlet in centimeters.

On the relay body, on its cover and on the bottom, there are two special taps; with the help of the upper one, gas is taken out and released; through the lower one, oil is taken out and the relay vessel is emptied.

Paddle type gas relay

The principle of operation of gas protection, a paddle-type relay is identical to the operation of a float relay, the difference is that its main element consists of a float and a blade, they are connected to a mercury contact that triggers a shutdown.

Cup type gas relay

Cup-type relays are more advanced modern models used in gas protection of transformers; instead of a float, there is a cup in the housing that can rotate around its axis. When the oil level in the relay drops, the contact closes; when gas is formed rapidly, the blade rotates and the contacts are switched off.

RKTU-01

Relay RKTU-01 continuously monitors leakage current in DC, AC or rectified voltage circuits (including monitoring the insulation of gas protection circuits). If the current exceeds the set limit (which is set by the user using a DIP switch on the front panel of the case), a trip signal is issued. The RKTU-01 relay has a wide range of response settings, thanks to which it can be used at various nominal operating voltages from 24 to 220 V.

If the gas relay contact closes, a current flows in the RKTU-01 input circuit, determined by the load of the gas protection circuit and obviously exceeding the fixed blocking setting.

Power transformers

In power transformers, in addition to the presence of a gas relay, which responds to gas formation and movement of oil towards the expander, there are also jet-type relays. The purpose of these relays is to protect the contactors of oil-filled transformer tap changers from damage that may occur due to too rapid flow of oil from the contactor tank into the conservator.

It is also worth mentioning that gas protection of power transformers is triggered even with the most minor damage, that is, even with low intensity of gas formation and at low oil speed. By the way, the electrical protection of the jet relay is not capable of detecting such minor violations.

Advantages

Gas protection of power transformers has a number of advantages:

1. Simplicity of design.
2. High sensitivity to damage, especially inside windings or to interturn short circuits.
3. A high degree of damage is characterized by a short duration of action,
4. The relay operates “on signal” when there is a weak signal, or “on signal” when there is intense gas formation.
5. Gas protection is the only protection of a transformer that protects it from a “steel fire” of the magnetic circuit due to damage to the insulation between the steel sheets.

Furnace transformer protection

Features of operation and application of the Tesla resonant transformer

The operation of furnaces is associated with a sharp increase and decrease in current, therefore it is not recommended to use differential protection here, but only gas and thermal ones. The heating elements of such furnaces can operate on reduced voltage from 220–660 Volts. Most often, special electric furnace transformers are used here. Of course, we are talking about furnaces for melting metal, and not for cooking. In them, the melting modes are changed by both the supply voltage and the magnitude of the arc current. Furnace transformers must be equipped with protection against overloads, as well as in the event of a short circuit. Overload protection is installed on the low side, and current transformers for instantaneous operation on the high side. In this case, the relay setting is adjusted in such a way that it does not turn off during normal operational short circuits, because they operate in this mode and during some short circuits, the shutdown should not occur, but only the raising of the electrodes.

In any case, in the end, I would like to note that the consequences of abnormal operating conditions of the transformer, and therefore the cost of subsequent repairs, depend on the settings and correct operation.

Division of transformer protection into main and backup

Any type of damage in a transformer poses a potential danger to both the integrity of the equipment and the reliability of the entire power system. Therefore, it is extremely important to competently set up the operation of protections at power plants, traction and transformer substations, local transformer substations and transformer substations. For this purpose, transformer protection is conventionally divided into two categories - main and backup.

Basic protection is a type of automation that is aimed at analyzing the internal state of the transformer (windings, hardware, additional equipment). This type covers both the device itself and adjacent buses, wires, etc.

Backup protection covers those disturbances that occur outside the transformer but can directly affect its conductors and internal components. These are all kinds of overloads, short circuits and overvoltages in lines, on adjacent devices, etc.

Rice. 2. Primary and backup protections

Benefits of protection

Among the main advantages of gas protection of a transformer are the following points:

In addition to the above, we can add that all transformers with a power of 1,000 kW or more are supplied with this type of protection. However, there is a small drawback, which is that gas protection does not react in any way to damage to the unit’s terminals, and therefore must be equipped with a second protection against internal problems. For example, in low-power transformers, overcurrent protection and current cut-offs became such a protection system.

Features of gas protection [edit | edit code ]

Gas protection of oil-filled devices has absolute selectivity and is triggered only if there is damage inside the tank of the protected object. The protection reacts to damage accompanied by the release of gas, the release of oil from the tank into the conservator, or an emergency drop in the oil level. Gas protection is one of the few after which automatic reclosure (automatic reclosure) is not allowed, since in most cases the damages it turns off are permanent.

There is a rule that says that all transformers with a power of 1 MW or more must be equipped with protection. To accomplish this task, gas protection of the transformer was chosen.

Protection Features

It is important to note that gas protection is multifaceted in its operating principle. It reacts not only to the formation of gases, but also to the presence of atmospheric air in the transformer, to movement or shocks of oil inside the casing, as well as to mechanical damage that may occur due to vibration of the unit housing.

In order to avoid false triggering of gas protection and unnecessary shutdown of the transformer, the lower float of the gas relay is most often set so that it responds to oil speed in the range from 50 to 160 cm/s.

Source

Gas relays RGT-50 and RGT-80

Transformer protection is one of the most important tasks of automation systems in substations. Its failure can lead to emergencies and significant material losses, because a variety of consumers are connected to it. Moreover, according to regulatory documents, gas protection is required for most transformers at substations with a power of 400 kVA and above, as it is the most effective and universal at the moment. To fulfill this requirement, gas relays are used, the features of which we will consider below.

The principle of operation of a gas relay for protecting a transformer is based on monitoring gas pressure. The relay is placed in a special metal casing and cut into the transformer oil line between the tank and the conservator. In the event of a sharp increase in temperature, which can occur for various reasons (for example, due to a short circuit in the transformer windings or a “steel fire”), the transformer oil begins to decompose or the organic elements of the winding heat up, causing gas to form inside the transformer.

Heated gases tend to enter the device expander, passing through the relay body. If the heating is weak, the gas pressure will increase gradually and the relay will give a warning signal without turning off the transformer. But at high gas pressure, which indicates strong heating, which, as a rule, is associated with a short circuit, the relay turns off the transformer.

It should be noted that a gas relay for protecting a transformer is capable of responding not only to the gas pressure formed as a result of heating, but also to the presence of atmospheric air in the transformer, to movement or shocks of oil inside the casing, as well as to various mechanical damage that can arise from - for vibrations in the unit body during operation. However, modern gas relays provide protection mechanisms against false operation and transformer shutdown. It is not for nothing that gas relays are widely used to protect transformers of various powers. There are three main advantages.

The first is the simplicity of organizing this type of protection. The second is the high sensitivity of gas relays. They even react to an interturn short circuit in the transformer windings, which is not available for differential and overcurrent protection. And the third advantage is relatively high performance. If a short circuit occurs, the gas relay turns off the transformer in a matter of seconds. That is why the use of gas relays to protect transformers is enshrined in regulations.

Today, there are several manufacturers in the country that produce gas relays for protecting transformers. One of them is, which produces gas relays RGT-50 and RGT-80 (Fig. 1).

In the mid-1990s, these relays replaced the Buchholz gas relays, widely used in the Soviet Union, produced by the Magdeburg Electrical Engineering and Instrumentation Plant (GDR), and today they are no less common in Russia than their predecessors. Gas relays RGT-50 and RGT-80 are successfully used to protect oil-filled transformers, autotransformers and reactors with an expander from damage inside the tank. Their flow sections have a diameter of 50 and 80 mm, respectively, and are designed for oil flow rates of 0.65, 1.0 and 1.5 m/s.

Rice. 1. Relay RGT-80

One of the main elements of such relays are the control contact blocks - BKR1 and BKR2. The BKR2 block has two floats - upper and lower, on which permanent magnets are installed that control the reed switches. The upper (signal) contact system of the relay is activated when the oil level in the transformer tank drops by 100–250 cm³.

The lower (disconnecting) contact system operates before the oil level reaches the lower level of the flange inlet on the relay body. As already noted, gas relays RGT-50 and RGT-80 have proven themselves in operation and are well known to our consumers.

At the same time, other products for electrical networks and protection of electrical equipment from ECCO-Technology have no less potential, which we will briefly describe below. Review of ESSO-Technology products The company presents a wide range of modern low-voltage and high-voltage equipment: KRU 2-10, KM-1F and KRUN, K-59, TEMP, relay RKTU-01 and other equipment. Let's look at these solutions in more detail.

The microprocessor terminal for control and protection of connections TEMP is used to protect overhead and cable lines, sectional and input switches. This device has rich capabilities and performs many protection, automation, control, measurement, recording and alarm functions.

Types of Buchholz gas relay models

This article mainly contains information about two-float gas relays, which are manufactured by global manufacturers and have the same flange design with sizes of 50 and 80 mm. Presumably all of the above models are analogues and can replace each other in standard power transformer designs.

Gas relay PG-22 and PGZ-22

The first domestically produced relay, produced from 1922 to 1968, is considered to be the PG-22 relay. Over the course of a long time, the relay design has changed slightly. These devices were assembled at the Zaporozhye Transformer Plant. Relays of the types PGZ-22, PG-54, RGZ-61, etc. were used. However, in all these relays, hollow cylindrical metal floats with mercury contacts attached to them served as signal and switching elements.

A design feature of the gas relay PG-22, and subsequently PGZ-22, is the absence of a disconnecting plate that responds to the speed of oil flow from the transformer to the conservator. The appearance of the PGZ-22 relay is shown in the image below.

Gas relay PGZ-22

In the relay body there are two floats located one above the other, each of which carries a closing mercury contact. The upper float (signal) contact closes when the float is lowered if the oil level drops to a certain limit. The lower float (switching) contact closes when the oil level in the relay further decreases, as well as during rapid gas release, when the oil in the oil line acquires significant speeds.

The floats have adjusting devices in the form of weights. The upper and lower floats are equipped with a weight. By moving the weight of the upper float, you can change its buoyancy (within small limits) and thereby change the sensitivity of the contact depending on the amount of gas released under the relay cover or a decrease in the oil level. By moving the weight on the lower float along the ring from the extreme left to the extreme right, you can adjust the sensitivity of the contact - depending on the speed of oil flow from the transformer to the expander through the oil line.

A valve is installed on the cover of the relay housing to take a gas sample and bleed air from the relay after its installation. In addition, the cover has leads from the contacts for connection to the protection circuit.

Price: from 4000 rub.

Gas relay RGChZ-66

The gas relay RGC-61, developed at Chelyabenergo, has become the most widely used, the industrial production of which was mastered by the Zaporozhye Transformer Plant. Thus, RGChZ-66 appears.

The main design feature of the RGChZ-66 gas relay is that the floats in it are made in the form of metal cups. Like all gas relays, it has a hermetically sealed housing installed in the oil line between the transformer tank and the conservator. It contains three elements: the upper one – signal and two lower switching elements. When the relay is filled with oil, the contacts located inside the cups remain open, since each cup on the side of the spiral spring is pulled up by it until it stops.

Gas relay RGChZ-66

When air is released or the transformer is damaged, accompanied by weak gas formation, gas or air rising to the conservator accumulates in the upper part of the relay, displacing the oil. In this case, the oil remains in the cup of the relay signal element, and under the influence of the mass of this oil, the cup rotates down around its axis until the contacts close.

The disconnecting elements (cup and plate) are located in the lower part of the relay housing, the plate is installed opposite the oil wire inlet on the transformer side. It is an element that reacts to the speed of oil movement in the oil line, and the cup is an element that reacts to the complete emptying of the relay housing from oil. Both elements act on one contact, and when the plate is working, the cup may not work.

If the transformer is damaged, accompanied by rapid gas formation, the pressure in the tank increases and the oil is forced out of the tank into the conservator. When the oil flow rate is equal to or greater than the relay setting, the force generated on the plate rotates around the axis with the stand and moving contacts until they close with the fixed contacts. In this case, the cup of the disconnecting element can remain at rest. In this case, the signaling element may operate slightly later than the tripping element, while the released gas rises from the transformer tank and fills the upper part of the gas relay housing.

Price: from 26,000 rub.

Gas relay EMB BF 80/Q and BF 50/10

German version of the relay. EMB is a “direct descendant” of the original company managed by Max Buchholz. The main office is located in Barleben.

Gas relays BF 80/Q (BF 50/10) consist of a body and a cover made of a weather-resistant light metal alloy, to which all the main elements of the relay are attached (B - relay with two elements, F - flange, 50, 80 - internal diameter of the flange in mm, Q – square flange shape). A plate indicating the type of relay and its data is attached to the cover, and there is also an arrow that should be directed towards the expander. The steel assembly bracket 8 is attached with two screws to the relay cover; this bracket is the main one for fastening the signal and switching elements, a permanent magnet and a number of other relay parts.

Gas relay EMB BF 80/Q

The signal element consists of a plastic hollow spherical float with a holder, which is attached to the assembly bracket. A round magnet is rigidly connected to the float and serves to control the signal contact. Both the signal and trip contacts of the relay are made using magnetically controlled reed switches, the closure of which occurs when the magnet approaches the end of the glass bulb in which the contact is enclosed. When the oil level in the relay drops, the float of the signal element drops and when the gas volume in the relay is 250-300 cm³, the control magnet causes the signal contact of the relay to close.

The disconnecting element is placed in the lower part of the relay housing under a plate that serves to secure the magnet in one of three positions and at the same time serves as a screen that protects the element from sludge deposited from the oil. The disconnecting element (as a signal element) is attached to the assembly bracket and also consists of a plastic float, a round magnet and a reed switch.

The trip element plate is held in its normal position by a permanent magnet. It is designed to be triggered by oil flow; at a certain flow speed, the attractive force of the magnet is overcome and the plate is deflected by a certain angle, turning around its axis.

Price: from 52,000 rub.

Gas relay RZT-50 and RZT-80

Ukrainian version of the RZT relay. The housing is made of cast aluminum alloy and has inlet and outlet flanges with holes for connecting the relay to pipelines. For visual control of the operation of the mechanical unit, the housing has sight glasses on both sides. To protect the glass from dirt and the harmful effects of sunlight, there are protective covers that fold up.

Gas relay RZT-80

The red arrow on the body indicates the direction of fluid movement towards the expander. The mechanical unit consists of a cover and an actuating mechanism. The mechanical unit is bolted to the housing. A gas release valve, a control button, and a block of sealed magnetically controlled contacts and a terminal block are mounted on the cover, cast from aluminum alloy. The terminal box has two threaded holes into which a plug and an adapter are attached for sealed entry and fastening of the control cable in the metal hose, and is closed on top with a hinged lid with a rubber gasket.

The sealed contact block (SBC) consists of a stainless steel casing with a connecting flange and a printed circuit board. With one or two (depending on version) magnetically controlled contacts. After assembly, the casing is filled with nitrogen or dried air and sealed with epoxy compound. The design eliminates contact of current-carrying elements with the working fluid.

The switching mechanism consists of a prefabricated frame in which the upper and lower switching systems are mounted. The upper switching system is made structurally on the principle of a breaking lever, on one arm of which a metal hollow float is fixed, and on the other - a permanent magnet; when the float is lowered, the lever closes and the magnet is forced to move relative to the BGK casing, and causes the closure of a magnetically controlled contact, and when raised float, the arm of the lever with the magnet lowers freely under the influence of gravity and opens the contact.

Price: from 32,000 rub.

Gas relay COMEM UNEL 50 H and COMEM UNEL 80 H

Italian version of the relay. The Comem gas relay is an assembly of two machined aluminum alloy castings that provide a perfect gland seal. The main relay body is equipped with tempered glass viewing windows with graduated cubic centimeter scale markings to indicate internal volume. The oil drain plug is located at the bottom of the main body. On the top cover there is a frame containing the moving parts of the relay. They consist of two floats and associated mercury switches, enclosed in glass bulbs, and one calibrated flow valve. Magnetic switches are also available for R1 and RF 1. The cover also carries:

• gas discharge valve with G1/8″ with external thread and protective cap;
• valve for pneumatic testing (OK) of alarm and shutdown circuits, with protective cap;
• pusher for mechanical shutdown of alarm and trip circuits, with a protective cap;
• terminal box containing 4 numbered M6 terminals and one ground terminal.

Gas relay COMEM UNEL 50 H

Login to myABB There is a problem with your request. As a routine test, all castings are tested by injecting ambient air at 2. Lightning impulse withstand peak voltage kV between circuits and ground 2 5 Open contacts 1 3 Working pressure - 1 bar, tested to 2.5 bar for 2 minutes at degrees Celsius.

The transformer 10 is equipped with a Buchholz relay according to the invention, which is designated by the control digit 16 and is integrated between the transformer and the expansion vessel. It is obvious that the adjustment of the movable damper 33 is of a discrete type and must be precisely studied as a delay in the size and number of removable parts 45 to make the relay 16 conveniently sensitive to oil currents.

Helium leak test as a guarantee of oil and gas tightness Before delivery, each Buchholz relay is tested for leaks in addition to a functional test. More details I agree. Gases moving towards the oil conservator, or shock waves created by the rapid development of gas, trigger the Buchholz relay alarm.

Based on the color change of the indicators built into the glass tubes, high-energy hydrogen incident and R-ray monoxide aging of the insulating material can be quickly and reliably detected. BR Internal gas accumulation and oil flow are monitored and kept under control by the Buchholz relay. Installed in the pipeline between the tank and the oil conservator, it reacts to faults occurring inside the transformer.

Price: from 70,000 rub.

Gas relay ORGRESENERGO RGT 50 201 and RGT 80 201

Russian version of the gas relay. Gas relays of the RGT series are designed to protect oil-filled transformers, autotransformers and reactors with an expander from damage inside the tank. When damaged, the oil heats up, gas is released, the oil level drops, or it spills from the tank into the conservator.

Gas relay ORGRESENERGO RGT-80-201

Relay types are set depending on the bore diameter and the oil flow rate setting. Thus, the flow sections of the RGT-50 and RGT-80 relays have a diameter of 50 and 80 mm, respectively, and are designed for an oil flow rate of 0.65; 1.0; 1.5 m/s.

One of the main elements of a gas relay is the control contact blocks. The BKR2 block has two floats - upper and lower, on which permanent magnets are installed that control the reed switches. In the RGT‑50 and RGT‑80 relays, the upper (signal) contact system is activated when the oil level drops by 100–250 cm³. The lower (disconnecting) contact system operates before the oil level reaches the lower level of the flange inlet on the relay body. When the oil flow rate in the pipeline from the tank to the conservator exceeds the relay operating value, the pressure plate shut-off system is activated.

The response speed of the RGT relay is 0.1 s.

The installation and connection dimensions of all of the listed relays allow them to be used to replace existing RZT-25, RZT-50, RZT-80, RGC3-66, BF 80/Q, BF 50/10 and URF 25/10 without any modifications .

Features and advantages of jet and gas relays RGT-50 and RGT-80: – they have more advanced float and contact systems than their “predecessors”; – provide the ability to implement two independent shutdown and two independent signal circuits; – allow you to change the settings for the oil flow rate; – allow you to replace contact systems in case of their malfunction without removing the relay from the transformer.

Price: from 48,000 rub.

Technical details and price from the manufacturer of the gas relay ORGRESENERGO can be found here

Gas relay MESSKO MBR-50 and MBR-80

German version of the gas relay. The MSafe® relay is installed in the pipe connecting the transformer tank and the expansion tank and reacts to accidents that occur inside the protected transformer. Accidents occurring inside the protected transformer are not subject to visual monitoring and can only be detected in a timely manner using a Buchholz relay. In this case, the Buchholz relay can signal or turn off the protected device as a result of the following events:

Gas relay MESSKO MBR-50

The movement of gases in the direction of the expander triggers the Buchholz relay alarm system.

The shock wave generated by the rapid release of gas triggers the Buchholz relay alarm system.

If the oil level in the expansion tank is too low and there is an oil leak, the Buchholz relay acts as an oil level sensor. The MSafe® relay is available as a two-float Buchholz relay in various versions for nominal pipe diameters DN25, DN50 and DN80. • MBR25-6, MBR25-16 and MBR25-G (1 1/2“ thread) • MBR50-6 and MBR50-16 • MBR80-6/4, MBR80-16/8 and MBR80-16/4 • MBR80-CH und MBR80-QU (square flange) • Upon request, it can be equipped with 4 NO, NC and/or changeover contacts. The following versions are optionally available: • inspection window cover • reset button after testing • fitting for connecting a compressed air cylinder • “marine” version

Price: from 87,000 rub.

Gas relay VILLE QJ-50 and QJ-80

Chinese version of gas relay. QJ type Buchholz relay is a kind of protection device used in oil immersed transformer with conservator and on-load tap-changer. If there is a malfunction inside the transformer (or on-load tap-changer), gases are released from the decomposition of the oil. When gas accumulates to a predetermined level, the signal contact of the Buchholz relay is switched on and an alarm signal is sent. If a serious fault occurs within the transformer or on-load tap-changer, the oil in the transformer surges, the oil flows heavily through the pipeline and causes the Buchholz relay breaker plate to operate, causing the switching contact to close and thus tripping the transformer. If the oil level is low due to loss of oil, the alarm will also sound.

Gas relay VILLE QJ-50

During installation, the axis of the relay pipeline must be parallel to the cover of the transformer housing, while the end leading to the expander is allowed to be higher, but the inclination between the axis and a flat surface should not exceed 4%.

The top consists of a gas lock, gas lock nut, probe, lock, retaining ring (float), weight release, skid plate, magnet, connection terminal, spring, control rod and dry reed contact. A flow device is formed that acts to release, a gas lock in the lid is used for depletion in the event of assembly and extraction of gas from the system. The probe is used to test the flexibility and reliability of the release mechanism.

Price: from 35,000 rub.

Gas relay CEDSAPE EB050A20N and BQ80420N

Italian version of the gas relay. The gas operated protective relay is designed to detect faults as well as minimize the spread of any damage that may occur in oil filled transformers. Thus, the relay is especially effective in case of faults: – lamination of short-circuited conductors – broken insulation of the conductor bolts – overheating of some parts of the windings – poor contacts – short circuit between phases, turns – ground faults – puncture of bushing insulators inside the tank In addition, the relay can prevent the occurrence of conditions leading to short circuits in the transformer, for example, a drop in oil level due to leaks or air penetration as a result of defects in the oil circulation system.

Gas relay CEDSAPE BQ80420N

Therefore, the use of other forms of protection does not exclude the use of a gas-driven Buchholz relay, since this device is the only means of detecting incipient faults, which, if not noticed, can lead to severe failures. The operating principle of the Buchholz relay is based on the fact that each type of fault in an oil-filled transformer causes decomposition of the insulating material, whether liquid or solid, due to overheating in the fault area or the action of an intense electric field, as well as the formation of a gas bubble. They enter the relay (usually filled with oil) through a pipeline connecting the transformer to the conservator, where the Buchholz relay is installed.

Design features of the active part of the relay are designed in such a way as to ensure free passage of oil flow through the housing, while there are no obstacles between the inlet and outlet of the oil inside the relay (except for the flap, which determines the speed of oil flow), such as floats or any other devices. The lower and upper floats are isolated from the oil flow, avoiding unattended operation due to oil turbulence. On request, a special device allows, in the event of an oil splash, to keep the NC contact in the operating position, which makes it possible to return the relay to its original position only manually. Contact Design The relays are equipped with magnetic switches to prevent unattended contact closure and subsequent malfunction of the relay if it is subjected to strong vibrations. In addition, each contact is driven by 2 magnets biased in such a way as to create a constant magnetic field around the contact itself, thus the contact is not affected by external magnetic fields present on the transformer.

Minor Faults When a minor or incipient fault occurs in transformers, small gas bubbles that travel up to the conservator become trapped in the relay housing, thereby causing the oil level inside the relay to drop. As a result, the upper float closes its magnetic switch, thereby completing the alarm circuit and controlling the external alarm. Serious Faults Gas Radiation When a serious fault occurs in a transformer, gas radiation is strong and causes oil to escape through the connecting pipe to the conservator. In the relay, this oil surge hits a flap located at the bottom (in front of the oil passage hole) and causes the magnetic switch to close, completing the trip circuit to the power switch and tripping the transformer. The oil flow rate required to operate the release can be changed by changing the counterweight mounted on the device itself or by changing its size. Oil leakage Oil leakage in the transformer causes the oil level inside the relay to drop, causing first the alarm float (upper) and then the trip float (lower), which close their own circuits. Air intake into the transformer caused by defects in the oil circulation system or other reasons , activates the alarm float first and after the break contact.

Design features, finishing and accessories, Buchholz relay body and cover are made of aluminum alloy, oil-proof and weatherproof; The compact design, meaning low weight, small dimensions, efficiency, is the result of a very long experience in relay manufacturing. Two flanges on the body make it easy to connect the relay to the tubes; On both sides of the relay housing there are two large viewing windows made of trogamide (tempered glass at the customer's request), with a graduated scale (at the customer's request, the windows can be equipped with a sun visor). The flat surface on the relay cover allows, using a spirit level, to install the relay with the appropriate inclination. Accessories The relay cover has a gas release valve, a button for testing electrical circuits, a small valve for pneumatic tests (standard for Buchholz size 2″ and 3″ on request for Buchholz size 1″) and a cable box (which is molded integrally into the lid) with 2 cable entries measuring M25x1.5.

There is an oil drain plug at the bottom of the relay. Ready As standard, all cast parts are protected with one layer of epoxy primer and one layer of polyurethane paint (total thickness 80 microns), final color RAL 7030, screws and washers made of stainless steel; The degree of protection of the device is IP 55. Therefore, the device is suitable for outdoor installation in tropical climates and industrial pollution.

Price: from 35,000 rub.

Gas relay ATVUS GOR 2M and GOR 3M

Indian version of gas relay. Power transformers are considered a highly reliable type of equipment, but to ensure the continuity of their operation in modern conditions, protective devices are required. The purpose of such devices is to shut down faulty equipment before large-scale damage occurs to the equipment or other equipment connected to it. Such devices typically respond to changes in current or pressure resulting from a fault and are used either for signaling or to shut down circuits.

Gas relay ATVUS GOR 3M

Protective devices in an ideal housing should be sensitive to all faults, easy to operate, reliable to maintain and economical. Considering liquid submersible transformers, a nearly ideal “protective device” is available in the form of gas and oil relays described here. The relay operates on the well-known fact that almost every type of electrical fault in “liquid submersible transformers” results in gas generation. This gas is collected in the relay housing and used in one way or another to trigger an alarm or trip circuit.

The gas-oil relay principle was first successfully demonstrated and used by Buchholz many years ago. In a series of experiments carried out extensively in Germany, it was found that the relay is capable of detecting incipient faults, thereby preventing further spread of the fault and extensive damage and saving costly and time-consuming repairs. The operating principle of this relay is so successful that, despite the ongoing search for better protective devices in other areas of the electrical power industry, the gas-oil relay itself still provides protection against various faults.

Price: 0 rub

RKTU-01

Relay RKTU-01 continuously monitors leakage current in DC, AC or rectified voltage circuits (including monitoring the insulation of gas protection circuits). If the current exceeds the set limit (which is set by the user using a DIP switch on the front panel of the case), a trip signal is issued. The RKTU-01 relay has a wide range of response settings, thanks to which it can be used at various nominal operating voltages from 24 to 220 V.

If the gas relay contact closes, a current flows in the RKTU-01 input circuit, determined by the load of the gas protection circuit and obviously exceeding the fixed blocking setting.

KSO, KRU, UBPVD, KRUN

High-tech equipment for electrical networks includes the following devices:

KRUN type K-59 are designed for receiving and distributing electrical energy of alternating three-phase current of industrial frequency 50 and 60 Hz with voltage of 6 and 10 kV. KRUN type K-59 are used as distribution devices, including at transformer substations (including complete, or block, transformer substations).

In addition to these products, the product line of ESSO-Technology LLC includes:

In conclusion, we note that it has another interesting area of ​​work: it is engaged in the production and supply of products for the repair of high-voltage circuit breakers, oil transformers, disconnectors and other equipment located at substations. This is a critical task, given that it is impossible to quickly modernize networks, and old equipment must be in working order while it is gradually replaced by new ones. ECSO-Technology has a quality certificate ISO 9001-2008 (ISO 9001:2008), which is proof of building an effective and modern management system.

Source: ESSO-Technology LLC, Cheboksary

Source

Domestic gas and jet relays

Gas relays of the RGT series and jet relays of the RST series are a domestic analogue of the Buchholz relays, which were widely used during the Soviet Union.
New relays have improved characteristics, are developed and produced in the Russian Federation and make it possible to update outdated instrumentation without any alterations. LLC "ESSO-Technology", Cheboksary

In the Soviet Union, starting from the 1930s, three main types of gas relays were consistently used, which generally had a similar principle of operation, but differed in some design features. At first, oil transformers with expanders were protected from explosion and fire using Soviet-made relays PG-22, PGZ-22, PG-54 and RGZ-61, then - RGChZ-66. The last to be installed on Soviet transformers were Buchholz relays, produced in the GDR by the Magdeburg Electrical Engineering and Instrumentation Plant (EGEM) and supplied to the USSR since 1970. They included two elements: the upper (signal) and the lower (disconnecting), which began to move when the oil was displaced by gas from the relay. The signal and shutdown elements were floats to which magnets were attached. When the oil was displaced from the relay, the magnets began to interact with the magnetic control contacts, closing the alarm circuit or overturning the pressure valve (flap).

Buchholz relays were installed in most energy enterprises, but by the mid-1990s the instrument fleet was already in need of updating, and then a concept was developed: to create products that would be almost identical to their Western counterparts, but at the same time would have better technical characteristics and would be produced in Russia.

This task was completed in 1995. With the support of RAO UES of Russia, two enterprises - OJSC Firm ORGRES, a large company operating in the electric power industry since 1933, and OJSC VNIIR - in accordance with TU3425-002-00113483-96, jointly created gas relays RGT-50 , RGT‑80 and inkjet relays RST‑25. Currently, the main partner of OJSC Firm ORGRES for the promotion and sale of these products is ESSO-Technology from Cheboksary.

Relay RGT and PCT

Gas relays of the RGT series (Fig. 1) are designed to protect oil-filled transformers, autotransformers and reactors with an expander from damage inside the tank. When damaged, the oil heats up, gas is released, the oil level drops, or it spills from the tank into the conservator. RGT‑50 is designed as an analogue of the BF‑50/10 and RZT‑50 relays. The initial samples of the RGT-80 relay are BF-80/Q, RZT-80 and RGChZ-66.

Rice. 1.

Gas relay RGT‑80

Relay types are set depending on the bore diameter and the oil flow rate setting. Thus, the flow sections of the RGT-50 and RGT-80 relays have a diameter of 50 and 80 mm, respectively, and are designed for an oil flow rate of 0.65; 1.0; 1.5 m/s.

One of the main elements of the gas relay is the control contact blocks (BKR1 and BKR2). The BKR2 block has two floats - upper and lower, on which permanent magnets are installed that control the reed switches. In the RGT‑50 and RGT‑80 relays, the upper (signal) contact system is activated when the oil level drops by 100–250 cm³. The lower (disconnecting) contact system operates before the oil level reaches the lower level of the flange inlet on the relay body. When the oil flow rate in the pipeline from the tank to the conservator exceeds the relay operating value, the pressure plate shut-off system is activated.

The jet relay RST‑25 (Fig. 2) protects oil-filled transformers and autotransformers from damage when oil spills from the switch tank into the conservator. The relay is an analogue of URF-25 and RZT-25.

Rice. 2.

Jet relay RST‑25

The flow section of the PCT‑25 has a diameter of 25 mm and is designed for an oil flow rate of 0.9; 1.2; 1.5; 2.0; 2.5 m/s.

The contact system of the PCT‑25 relay is activated only by oil flow.

The response speed of the RGT and PCT relays is 0.1 s.

The installation and connection dimensions of all of the listed relays allow them to be used to replace existing RZT-25, RZT-50, RZT-80, RGC3-66, BF 80/Q, BF 50/10 and URF 25/10 without any modifications .

Features and advantages of jet and gas relays RST‑25, RGT‑50 and RGT‑80: - they have more advanced float and contact systems than their “predecessors”; — provide the ability to implement two independent shutdown and two independent signal circuits; — allow you to change the settings for the oil flow rate; — allow you to replace contact systems in case of their malfunction without removing the relay from the transformer.

In 2004 (Cheboksary), in partnership with OJSC Firm ORGRES, began work on the promotion and sale of relays RST-25, RGT-50 and RGT-80. LLC "ESSO-Technology" is one of the enterprises of the Russian electrical industry, specializing in the production of modern low-voltage and high-voltage equipment. This company has always worked in the field of import substitution, and therefore the “Switch to Domestic” concept proclaimed by the government was met with approval and enthusiasm. ESSO-Technology LLC has a quality certificate ISO 9001-2008 (ISO 9001:2008), which is proof of building an effective and modern management system.

Instead of an afterword. Blitz interview with the executive director of ESSO-Technology LLC Nikolai Valerievich Myasnikov

ISUP: Are the RGT and PCT relays literally analogues of old products, or has their design undergone some changes or been improved?
N.V. Myasnikov:
Of course, the design has been changed for the better. Buchholz relays can rather be called the “progenitors” of new relays. The development of the RGT and RST series was carried out by both research staff of the Institute of Relay Manufacturing and specialists from ORGRES who worked in the energy networks of RAO UES of Russia, and they knew well what difficulties arise when operating Buchholz relays. The information they had was taken into account in order to make the RGT and PCT relays more modern devices. This is the first, and the second, you understand, materials and technologies change over time. Thanks to their improvement, it is often possible to achieve higher quality at the same or lower cost of the product.

ISUP: The article is devoted to the production of inkjet and gas relays.
What could you tell us about other areas of your company’s activities? N.V. Myasnikov:
Of course, our work is not limited to the production of relays. We have a fairly wide range of products, which can be found on the company website. The main activity of ECSO-Technology is the production and supply of products for the repair of high-voltage circuit breakers, oil transformers, disconnectors and other equipment located at substations. It must be said that the production of spare parts for the repair of old substations is a large and important job. There is currently a lot of equipment in use whose service life is running out. It must be maintained in working order while it is being replaced with new, more modern products. It is impossible to simply take and replace everything at the same time due to the fact that this involves very large financial costs. Not all operating organizations have such funds. But substations must be kept in working order. Therefore, spare parts are replaced, while simultaneously and gradually introducing more modern equipment.

ISUP: What allows you to stay ahead of the competition?
N.V. Myasnikov:
Of course, we have competitors. But we also have a wealth of experience, which gives great advantages when working with customers. We have been repeatedly contacted on the recommendations of our old clients, they contacted us because they were faced with a problem: either they could not find the necessary equipment, or they were not able to identify some old part to replace. They just don't know its name! And then they recommend us, and we solve all problems.

Gas protection of transformers

Gas protection for transformers is the most sensitive and versatile protection against internal damage. It is installed on oil-cooled transformers that have an oil conservator.

The principle of operation of gas protection is based on the fact that any damage in the transformer, including increased heating of the oil, leads to chemical decomposition of the transformer oil, as well as organic winding insulation materials, resulting in the release of gas inside the transformer.

This gas affects special gas protection devices, which give a warning signal or shut down the transformer.

Gas protection responds to damage such as an interturn short circuit in the transformer windings, to which differential and overcurrent protection does not respond; since in such cases the magnitude of the circuit current is insufficient to trigger the protection.

The nature of the damage in the transformer and the size of the damage affect the intensity of gas formation. If the damage develops slowly, which corresponds to slow gas formation, then the protection gives a warning signal, but does not turn off the transformer.

Intense and even violent gas formation, indicating a short circuit, creates a signal in the gas protection system of such a magnitude that, in addition to warning, causes the shutdown of the faulty transformer.

Gas protection for transformers also triggers a warning signal when the oil level in the tank drops.

Application [ edit | edit code ]

Some powerful electrical devices generate a significant amount of heat during operation, as a result of which air cooling of such devices is not effective enough. In these cases, for cooling, these devices (which may include transformers, autotransformers, reactors) are placed in a tank filled with transformer oil, which naturally or forcedly cools these devices. In addition, the oil additionally serves to increase the insulation level of transformer windings.

The use of oil solves the cooling problem, but creates a new problem associated with the increased danger of operating an electrical apparatus. If live parts are damaged (for example, due to a short circuit between the windings of a transformer), the oil begins to heat up, increased gas formation occurs, and the oil pressure in the tank rises sharply, which can lead to an explosion accompanied by a fire. To prevent such damage, gas protection is used.

Gas relay operating principle

Gas protection (GZ) is carried out using special gas relays. The gas relay is a metal casing embedded in the oil line between the transformer tank and the conservator. The relay is filled with oil.

gas relay transformer

The casing has a sight glass with a scale, which is used to determine the volume of gas accumulated in the relay. On the cover of the gas relay there is a tap for releasing air and taking a gas sample for analysis, and there are also contacts for connecting the cable.

The designs of gas relays differ in the principle of execution of the reacting elements in the form of:

Float relays gas relay

Float relays have two floats mounted on hinges inside the casing, which are hollow metal cylinders. The floats are equipped with mercury contacts connected by flexible wires to terminal clamps on the relay cover. The mercury contact is a glass bulb with two contacts soldered into its vertical part. The cones contain a small amount of mercury, which at a certain position of the cones closes contacts with each other, thereby creating a circuit through a relay. When the speed of gas and oil flows is about 0.5 m/s, the lower float located in the flow path overturns and its mercury contacts close in the shutdown circuit. Due to the fact that in the event of a short circuit (short circuit) violent gas formation immediately occurs in the transformer, the GZ produces a shutdown within a short time of 0.1-0.3 seconds. The disconnecting element also operates when the oil level in the relay housing is greatly reduced.

Rice. 9.4 Float gas relay, principle of operation

Paddle relay gas relay

The principle of operation of gas protection, a paddle-type relay is similar to the operation of a float-type relay, differs in that its main element consists of a float and a blade, they are connected to a mercury contact, which gives a shutdown command.

Rice. 9.5 Vane gas relay operating principle

Cup relays

Cup relays use open metal cups instead of floats and usually open contacts operating directly in oil instead of mercury contacts. It is normal for the relay body to be completely filled with oil, while the upper and lower cups are also filled with oil and are held in their original state by springs.

Cup gas relay

The most famous and widespread gas relay is the RGChZ-66 type, produced by the Zaporozhye Transformer Plant.

Currently, gas and jet transformer protection relays of the RGT50, RGT80, RST25 types, developed by ORGRES and VNIIR, are produced. These relays have advantages over older designs.

Structure of a gas relay. Basic protection mechanism and damage properties of power transformer

Description of the function of a two-element (double-float) gas relay. During normal operation of the transformer, the internal chamber of the Buchholz relay is completely filled with oil. The floats are fixed in the upper positions and act as triggers. In case of any malfunction, a gas accumulation will form inside the tank. It moves to the expander, which is connected to the tank via a pipeline. A gas relay is located in the connecting pipe section. The released gas is primarily accumulated in this place.

Gas relay from Siemens-Schuckertwerke 1927

Depending on the severity of the damage inside the transformer and the amount of gas in the relay, the protective properties are activated. Due to the fact that the gas displaces the oil supporting the floats, they move down and activate the supply of the necessary signals to adjust the operation of the power transformer. Two-element gas relays are used to detect minor or major faults, for example:

• damage to the tie pin insulation;
• short circuits at interturn points;
• damaged contacts;
• overheating of the winding sector;
• bushing puncture;
• phase short circuits;

The protective function of the gas relay will also be activated in the event of an oil leak or air entering the oil system.

The gas-oil relay not only provides protection against a number of internal faults, but can also in some cases help identify the type of transformer fault. The gas collected in the relay differs in composition, color and odor depending on the damage factor.

• If the gas is colorless and odorless or has only a faint oil odor, then the gas is trapped in the air in the oil or insulating sheath;
• If the gas is greyish-white in color with a pungent and penetrating odor but does not ignite, it is due to overheating or damaged insulation.
• If the gas is dark gray and flammable, it may be due to flash in the oil or excessive oil overheating caused by a faulty winding or center element.

When the gas relay protection signal is activated, if analysis of the collected gas does not indicate a serious fault, the transformer can be left in operation until it can be thoroughly inspected. Usually, during the initial startup of a transformer, signals appear about its malfunction due to the accumulation of air in the oil or insulating parts.

Gas protection of transformer on-load tap-changer on jet relay

The gas protection of the on-load tap-changer of the transformer is made on a jet relay and acts to turn off the transformer when there is an intensive movement of oil flow from the on-load tap-changer tank towards the conservator.

The on-load tap-changer contactors are located in a compartment separate from the transformer tank. Since the arc burns in the oil when switching contactors, the oil gradually decomposes, releasing gas and other components. This oil does not mix with the rest of the oil in the tank and does not degrade its quality. The on-load tap-changer tank is also connected to the expander (separate compartment) and a special relay, for example, type URF-25, is installed in the connecting pipe.

Jet relay URF 25, URF 25/10

This relay is called a jet relay and only operates when oil is released. Once activated, the jet relay remains in the actuated position and must be returned to its original position by pressing the button on the relay. The relay is also equipped with a test button, by pressing which you can turn off the transformer.

The jet relay URF 25/10 is installed in the pipeline between the step switch head and the expander. Installing a relay allows you to control the oil flow. If the oil flow speed exceeds the response threshold of the valve gate (0.9-4.0 m/s ±15%, depending on the valve gate), the switching contact is switched on and the transformer is switched off.

Operating principle of transformer jet relay

Jet relay ÜRF-25/10

Explanation of the relay abbreviation:

25 – internal diameter of the flange in mm;

10 – pressure at the location of the flange in kgf/cm².

During normal operation of the contactor of the on-load tap-changer (voltage regulation under load), under the influence of an electric arc at the moment of switching, a small amount of oil decomposes and gas is released from it, which passes through the pipeline into its conservator or into the compartment of the general conservator and then exits through its respiratory tract into atmosphere. A small amount of gas released from the oil during contactor operation is normal.

Malfunction of the contactor can be caused by damage to the insulation, weakening of the springs of the mechanism, aging of ceramic power contacts, which leads to slower and unclear switching. A prolonged arc is accompanied (taking into account the small amount of oil in the contactor tank) by rapid decomposition of the oil. A stream of oil mixed with gas is directed from the contactor tank into the expander.

In case of such damage, it is necessary to turn off the transformer and the on-load tap-changer in order to take measures to eliminate the damage, therefore the jet relay, which is triggered at a given speed of the oil jet, is activated immediately to turn off the transformer.

Unlike a gas relay, a jet relay will not respond to gas formation and oil leaving the transformer.

The jet relay is a single element. The reacting element of the relay is a steel plate 1, similar to the plate of a gas relay. The plate is located on the side of the contactor tank and under normal conditions is held in a certain position by weight 2. The oil jet creates pressure on the plate, which leads to its rotation at a certain angle. At the same time, the load 2 rises and the permanent magnet 3 approaches the magnetically controlled reed switch 4, which closes.

At the end of the movement, the plate is fixed in the actuation position using latch 5, so the relay contact remains closed until manually reset. This does not make it possible to put into operation a transformer that has been disconnected from the gas protection of the on-load tap-changer. Thus, we can conclude that such injuries are considered the most dangerous and require careful attention.

To return a triggered relay to its normal position, it has a return device, which also serves to monitor the functionality of the relay.

The control-return device of the jet relay is structurally similar to the control device for the Buchholz gas relay and consists of a movable rack 6 with a return spring 7 and a protrusion 8. The control-return device is controlled, like the gas relay, by button 9 on the relay cover.

When the button is slowly pressed, the rack, moving in the guide frame, lowers by approximately half its stroke and removes the spring latch from the slot of the installation bracket 10, which, under the influence of gravity of the load 2, causes the plate 1 to return to its normal position and the reed switch 4 to open (through the inspection window the glass shows that the load is lowered to a horizontal position).

When you further press the button down all the way, the protrusion 8 of the rack 6 is pressed onto the rounded edge of the weight holder 11 and the load rises again, as if under the pressure of a stream of oil (we can see this through the sight glass).

Thus, operating personnel should pay attention that the relay returns by pressing the button until halfway through the stroke, and is activated until the end of the stroke.

The relay is available in two versions:

— 1 setting range – 0.9; 1.2; 1.5 m/s;

— 2 setting range – 1.5; 2.0; 2.5 m/s.

The settings are changed by moving the load up or down along the fastening axis.

The jet relay does not have a gas tap and there are no scale divisions on the sight glasses.

The relay must be installed in the pipeline between the contactor tank and its expander (pipeline with a diameter of 25 mm) in the direction of the oil flow. The rise of the pipeline from the contactor to the expander should be 2-4%, as well as the gas relay.