Buchholz relay

Transformer outages have a considerable economic impact on the operation of a power supply network.Internal gas accumulation and oil flow are monitored and kept under control by the Buchholz relay. Our Buchholz relays are designed topromptly provide information about internal malfunctioning, giving the possibility to shut down the transformer and prevent its possible destruction. Why Hitachi Energy? • More than 50 years of experience in manufacturing transformer components • New generation of Buchholz relays with analog and digital output (eDevices) • Global after-sales and customer support network

Buchholz relays have been applied on oil-filled power and distribution transformers at least since the 1940s. The relay is connected to the oil piping between the overhead conservator tank and the main oil tank of a transformer. The piping between the main tank and conservator is arranged so that any gas evolved in the main tank tends to flow upward toward the conservator and gas detector relay. Operation [ ] Depending on the model, the If an Through a connected gas sampling device the control can also be made from the ground. Depending on the requirements, the Buchholz relay has a flange or threaded connection. The classic Buchholz relay has to comply with the requirements of the DIN EN 50216-2 standard. Depending on the requirements, it is equipped with up to four (2 per float) switches or change-over switches, which can either send a light signal or switch off the transformer. The relay was first developed by Max Buchholz (1875–1956) in 1921. See also [ ]

Our Buchholz relays are characterized by a rugged design, formed from the experiences of more than 100 years of measuring, control and safety technology. The Buchholz relay takes on the function of a central protective device for fluid-filled transformers and reactors with an expansion tank. Installed in the pipeline between the tank and expansion tank, it responds to errors that occur inside the transformer being protected. Damage can be detected by the Buchholz relay early, thus preventing destruction. We are here for you. Wherever you are. Looking for the right contact partner? Do you have a concern, but don't know whom you should contact? You will find that information in our contact overview. In the event of any technical disturbances, our 24/7 support is always at your disposal (+49 941 4090 2000).

A transformer is a very important component in electrical applications. It is used to step up or step down a voltage. It can come in both lower and higher voltages. For higher voltages (more than 500 kVA), mostly oil-filled transformers are used. As they work in higher voltages, there are bound to occur many internal faults like insulation failure, oil failure, windings failure, partial discharge, short circuits, arcing, etc. If these failures are not detected, then they will result in damage to the transformer. For this, a special type of relay called the Buchholz relay is used. In this post, we will learn the concept of a Buchholz relay. What is a Buchholz Relay? The Buchholz relay is used to detect internal faults in an oil-filled transformer. Remember that oil is used as insulation for the transformer body. Buchholz Relay works on the theory of gas detection. The Buchholz relay is also termed as safety device used in the oil-filled transformers. Refer to the below image for understanding. When internal faults occur inside, the current shoots up to a very high abnormal range. This high current automatically increases the operating temperature inside. As oil is filled inside, due to the excess heat generated, it starts to evaporate. As it starts to turn into gaseous form, moves upwards towards the oil conservator. The relay is placed between the conservator and transformer tank (body). It detects this gas and immediately trips the circuit. This means the Working Principl...

The Buchholz relay is a protective device for oil-immersed transformers, detecting faults early to prevent damage and ensure power system reliability. Buchholz Relay: A Comprehensive Overview A Buchholz relay is a vital protective device used in transformers to detect and prevent faults. Transformers are essential components in power distribution systems, responsible for stepping up or stepping down voltage levels. However, they can develop internal faults, such as short circuits, insulation failure, or partial discharges. These faults can lead to excessive heating and gas formation within the transformer, which can damage the unit or cause it to fail altogether. The Buchholz relay serves as an early warning system to help prevent such incidents. History and Development The Buchholz relay, named after its inventor Max Buchholz, was first developed in 1921. Max Buchholz was a German engineer who sought to improve transformer safety by designing a device that could detect faults before they became severe. His invention has since been widely adopted and is now a standard component in oil-immersed transformers. How a Buchholz Relay Works A Buchholz relay is typically installed in the oil-filled pipe connecting the transformer tank to the conservator, a reservoir that holds the oil. The relay operates on the principle that gas is generated during a fault within the transformer. This gas accumulates in the relay chamber, causing a float to drop, which then activates a switch tha...

Contents • • • What is Buchholz Relay? A Buchholz relay is a safety device mounted on (some) oil-filled Buchholz relays have two main elements. The upper element consists of a float. The float is attached to a hinge in such a way that it can move up and down depending upon the oil level in the Buchholz relay container. A mercury switch is fixed on the float. The alignment of the mercury switch hence depends upon the position of the float. The lower element consists of a baffle plate and a mercury switch. This plate is fitted on a hinge just in front of the inlet (main tank side) of the Buchholz relay in a transformer in such a way that when oil enters in the relay from that inlet in high pressure the alignment of the baffle plate along with the mercury switch attached to it, will change. The Buchholz relay working principle is very simple. Buchholz relay function is based on a very simple mechanical phenomenon. It is mechanically actuated. Whenever there will be a minor internal fault in the transformer such as an insulation fault between turns, break down of core of the transformer, core heating, the insulating transformer oil will be decomposed in different hydrocarbon gases, CO2 and CO. The gases produced due to the decomposition of transformer insulating oil will accumulate in the upper part of the Buchholz container which causes a fall of the oil level in it. The video below shows a working animation of a Buchholz relay: Fall of oil level means lowering the position o...

Definition: The Buchholz relay protects the transformer from internal faults. It is the gas actuated relay. The Buchholz relay is placed between the main tank and the conservator. Such type of relay is used in the transformer having the rating higher than 500KVA. It is not used in small transformer because of economic consideration. Working Principle of Buchholz Relay When the fault occurs inside the transformer, the temperature of the oil increases. The oil evaporates in the form of the gas. The generation of the gas depends on the magnitude of the fault occurs inside the transformer. The internal failure occurs in the transformer either because of the insulation breakdown between the winding or the winding have the weak initial contact. The fault induces the arc which increases the temperature of the gas. The oil becomes evaporated and moves upwards. The Buchholz relay detects the failure and gives the alarm to the personnel. The transformer is disconnected from the main supply for maintenance. Construction of Buchholz Relay The Buchholz relay has two hinged which is placed in the metallic chamber. This metallic chamber is connected through the pipe between the conservator and main tank. The one of the hinged is placed in the upper portion of the metallic chamber along with the mercury switch. This mercury switch is used for activating the alarm. The other float is placed in the lower portion of the metallic chamber along with the mercury switch. The mercury switch is us...

• • • • • • • • • Working principle of Buchholz relay Faults that occur inside an oil-filled transformer generate heat, much enough to decompose the insulating oil into gases such as hydrogen, carbon monoxide, methane, etc. These gases gradually move toward the conservator through the connecting pipe, but a part of them get trapped inside the Buchholz relay. The trapped gases displace oil inside the relay. Hence the level of oil in it falls, activating the float switches inside. In the case of large faults, a huge amount of gases are produced by the decomposition of oil. This results in an oil surge that moves toward the oil conservator. This oil surge pushes down the flap attached to the transformer side of its outlet. This part can be understood only after reading the following sections. Image source: Construction and design features Cross Section of a double float Buchholz Relay Source: The external casing and terminal box of a Buchholz relay are made up of aluminum alloy. It is a weatherproof and oil-tight design that holds inside two float switches, one at the top and the other at the bottom, for sensing oil level and flap to sense oil surge. Two reed switches/mercury switches, one for alarm and the other for circuit breaker trip, are attached to the float switch. These switches are connected to the terminals within the terminal box at the top of the relay. An inspection window is provided to monitor the oil level inside it. The viewing window is fitted with scaled si...

Our Buchholz relays are characterized by a rugged design, formed from the experiences of more than 100 years of measuring, control and safety technology. The Buchholz relay takes on the function of a central protective device for fluid-filled transformers and reactors with an expansion tank. Installed in the pipeline between the tank and expansion tank, it responds to errors that occur inside the transformer being protected. Damage can be detected by the Buchholz relay early, thus preventing destruction. We are here for you. Wherever you are. Looking for the right contact partner? Do you have a concern, but don't know whom you should contact? You will find that information in our contact overview. In the event of any technical disturbances, our 24/7 support is always at your disposal (+49 941 4090 2000).

Buchholz relays have been applied on oil-filled power and distribution transformers at least since the 1940s. The relay is connected to the oil piping between the overhead conservator tank and the main oil tank of a transformer. The piping between the main tank and conservator is arranged so that any gas evolved in the main tank tends to flow upward toward the conservator and gas detector relay. Operation [ ] Depending on the model, the If an Through a connected gas sampling device the control can also be made from the ground. Depending on the requirements, the Buchholz relay has a flange or threaded connection. The classic Buchholz relay has to comply with the requirements of the DIN EN 50216-2 standard. Depending on the requirements, it is equipped with up to four (2 per float) switches or change-over switches, which can either send a light signal or switch off the transformer. The relay was first developed by Max Buchholz (1875–1956) in 1921. See also [ ]