RU2713204C1 - Method of protecting a single-phase furnace transformer with a short network in form of a group of buses from electrical damages - Google Patents

Abstract

FIELD: electric power engineering.

SUBSTANCE: use in the field of electric power engineering for protection of furnace transformers with a short network in the form of a group of buses from turn-on short circuits in the primary winding of the transformer, as well as short circuits and breaks in the chain of short-circuit buses. According to the method, the magnetic field of the transformer windings scattering is measured in the plane perpendicular to the yokes of its core and passing through their center, and if it is more than zero, the transformer is disconnected from the mains and a "turn-on-fault" signal is generated. In addition, scattering magnetic fields are measured at windings upper and lower end faces on one of cores of transformer core, comparing them with each other, and if their difference is greater than zero, a signal is generated to disconnect the transformer from the network, as well as a signal "short-circuit fault", which in its turn is blocked when there is a "turn-on-fault" signal.

EFFECT: broader functional capabilities in the form of the ability to detect short circuits and breaks in a chain of short-circuit buses, as well as in the possibility of distinguishing between transformer damages and short-circuit faults.

1 cl, 2 dwg

Description

The invention relates to the electric power industry and is intended for the protection of furnace transformers with a short network in the form of a group of tires against windings in the primary winding of the transformer, as well as short circuits and open circuits in the bus network of a short network.

Closest to the proposed technical solution is a method of protecting a single-phase furnace transformer with a short network in the form of a group of buses from electrical damage, in which the magnetic field of the transformer windings is measured in a plane perpendicular to the yokes of its core and passing through their middle, and if it is turned off, it is turned off transformer from the network and form a signal "coil circuit" [KZ Patent No. 27097 publ. 06/14/2013, bull. No. 6].

However, this method does not allow to detect electrical damage in the form of short circuits, as well as breaks in the bus circuit of the short network.

The technical result is the expansion of functionality in the form of the ability to detect short circuits and breaks in the bus circuit of a short network, as well as the ability to distinguish transformer damage from damage to a short network.

The technical result is achieved by additionally measuring the magnetic fields of scattering at the upper and lower ends of the windings on one of the transformer core rods, comparing them with each other and if their difference is greater than zero, they form a signal to disconnect the transformer from the network, as well as a signal “damage” short circuit ”, which is blocked in the presence of a signal“ coil circuit ”.

The problem is solved due to the fact that the magnetic field of the scattering of the winding on any core core of a single-phase furnace transformer is symmetrical about its middle. Therefore, the scattering magnetic field of these windings at the upper and lower ends is the same, and their difference will be zero. In the event of a short circuit or a break in the flexible connection in any pair of buses of the short network, the magnetic fields of scattering at the upper and lower ends of these windings will be different, and their difference will be greater than zero. And since this can also occur when a winding is closed in the transformer winding, in this mode the signal about damage to the short circuit is blocked.

Comparative analysis with the prototype shows that the claimed technical solution differs from the known technical solution in the number and sequence of operations.

A comparison of the claimed technical solution with a known technical solution shows that these operations are known. However, their sequence allows us to show new properties in the claimed technical solution, which leads to the expansion of functionality due to the ability to detect electrical damage in a short network, as well as the ability to distinguish between a winding in the transformer windings and electrical damage in a short network.

Figure 1 shows the design of a single-phase furnace transformer with a short network section, as well as the placement of the measuring transducers in this transformer. Figure 2 shows a diagram of a protection device for implementing a method of protecting a single-phase furnace transformer with a short network in the form of a group of tires from electrical damage.

The furnace single-phase transformer is made in the form of a core 1 and two identical coils, which are placed on its rods 2 and 3. Each coil contains parts 4 and 5 of a multi-turn primary and elements of a two-turn secondary winding. Moreover, during installation, parts 4 and 5 of the multi-turn primary are connected in accordance - sequentially. Therefore, the closure of the turns 6 can occur only in the primary winding. The secondary winding of the transformer is split. It consists of several, in this case four, isolated from each other two-turn windings 7-10, which are located on parts 4 and 5 of the primary winding. In this case, each of them is connected to one of the pairs of short-circuit tires 11 isolated from each other, which, in turn, is connected to the electrodes of the furnace using flexible connections. These elements are not shown in the figures.

в реле 21 при отсутствии виткового замыкания в обмотках 4 и 5, а также электрического повреждения в короткой сети 11. Второй измерительный преобразователь 25 в виде цилиндрической катушки индуктивности размещается на плоскости Q, которая перпендикулярна ярмам 26 и 27 сердечника 1 однофазного печного трансформатора и проходит через их середину. При этом его продольная ось 28 располагается параллельно осям 13 и 14 стержней 2 и 3. Выводы 29 и 30 этого измерительного преобразователя присоединяется к обмотке реле 31. При этом нормально разомкнутый контакт 32 реле 31 подключен к отключающей цепи 33 выключателя и к блоку 24 индикации вида повреждения, а нормально замкнутый контакт 34, который является блокировочным, включают последовательно с контактом 22.The first measuring transducer 12 in the form of a cylindrical inductor with a lead from the middle is placed on the plane R, which passes through the axes 13 and 14 of the rods 2 and 3 of the core 1, so that its longitudinal axis 15 is parallel to the axis 13. Moreover, in accordance with the diagram on figure 2, the beginning 16 and the end 17 of the coil of the measuring transducer 12 are connected to the extreme terminals of the variable resistor 18, and the middle terminal 19 of this converter and the movable contact 20 of the resistor to the relay coil 21. In this case, the normally open contact 22 of this e 23 is connected to the switch breaking the circuit and to the unit 24 indicating the type of fault. Variable resistor 20 is designed to set the current $$\Delta I=0$$

in the relay 21 in the absence of a short circuit in the windings 4 and 5, as well as electrical damage in the short circuit 11. The second measuring transducer 25 in the form of a cylindrical inductor is placed on the Q plane, which is perpendicular to the yokes 26 and 27 of the core 1 of the single-phase furnace transformer and passes through their middle. At the same time, its longitudinal axis 28 is parallel to the axes 13 and 14 of the rods 2 and 3. The conclusions 29 and 30 of this measuring transducer are connected to the coil of the relay 31. In this case, the normally open contact 32 of the relay 31 is connected to the disconnecting circuit 33 of the switch and to the display unit 24 damage, and the normally closed contact 34, which is the interlock, include in series with the contact 22.

в обмотке реле 31 будет равен нулю, а его контакты 32 и 34 будут находиться в исходном положении. В свою очередь токи $$I_2$$

и $$I_3$$

будут равны между собой, их разность $$\Delta I$$

в обмотке реле 21 будет равна нулю, а контакты 22 реле 21 будут также находиться в исходном положении. Поэтому сигнал с контактов реле 21 и 31 на отключение печного трансформатора от сети и на входе блока 24 индикации вида повреждения отсутствует. Печной трансформатор не выводится из работы.The protection device operates as follows. In an arbitrary operational mode of operation of the furnace transformer with a short network 11 for the same number of turns in its windings 4, 5 and 7-10, which are located on different core rods, the same currents flow. With the exact manufacture and installation of these windings, the currents in them will induce an electromotive force equal to zero in the transducer 25, and the electromotive forces of the upper and lower windings in the transducer 12 will be equal in magnitude. Resulting in current $$I_{}$$$${}_1$$

in the winding of the relay 31 will be zero, and its contacts 32 and 34 will be in the initial position. In turn, currents $$I_{}$$$${}_2$$

and $${\mathrm{<figure-callout\; id="3"\; label="I"\; filenames="00000007.png"\; state="\{\{state\}\}">I</figure-callout>}}_3$$

will be equal to each other, their difference $$\Delta I$$

in the winding of the relay 21 will be zero, and the contacts 22 of the relay 21 will also be in the initial position. Therefore, there is no signal from the relay contacts 21 and 31 to disconnect the furnace transformer from the network and at the input of the unit 24 for indicating the type of damage. The furnace transformer is not taken out of operation.

и $$I_1$$

в обмотках реле 21 и 31 будут не равны нулю. В результате эти реле сработают. При этом контакты 22 и 32 замкнутся, а контакт 34 разомкнется. В результате в отключающей цепи 33 появится сигнал на отключение трансформатора от сети, а блок 24 индикации высветит сообщение «витковое замыкание».When the turns 6 are closed, the current in them will significantly exceed the amount of current in the rest of the primary winding. This will lead to a change in the distribution of the scattering magnetic field of the damaged winding on the rod 3 and to the appearance of an electromotive force in the measuring transducer 25. In this case, the electromotive forces of the upper and lower windings in the transducer 12 will not be equal to each other. In this regard, currents $$\Delta I$$

and $${\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="00000007.png"\; state="\{\{state\}\}">I</figure-callout>}}_1$$

in the windings of the relay 21 and 31 will not be zero. As a result, these relays will trip. In this case, contacts 22 and 32 will be closed, and contact 34 will open. As a result, a signal to disconnect the transformer from the network appears in the disconnecting circuit 33, and the display unit 24 displays the message “coil closure”.

в обмотке реле 31 будет равен нулю и оно не срабатывает, а разность тока $$\Delta I$$

в обмотке реле 21 будет не равна нулю и оно сработает. При этом контакты 22 замкнутся, а контакты 32 и 34 останутся в исходном положении. В результате в отключающей цепи 23 появится сигнал на отключение трансформатора. При этом блок 24 индикации высветит сообщение «повреждение короткой сети».If a short circuit occurs in one of the bus pairs, for example, attached to a two-turn winding 10, the current in it will increase and will be much larger than the current in the other two-turn windings 7-9. Which will lead to the same change in the distribution of the magnetic field of the scattering of the damaged winding on both rods of the transformer. In this case, the electromotive force in the transducer 25 will be zero, and the electromotive forces of the upper and lower windings in the transducer 12 will not be equal to each other. In connection with this current $$I_{}$$$${}_1$$

in the winding of the relay 31 will be zero and it does not work, and the current difference $$\Delta I$$

in the winding of the relay 21 will not be zero and it will work. In this case, the contacts 22 will be closed, and the contacts 32 and 34 will remain in their original position. As a result, a trip signal for the transformer will appear in the trip circuit 23. In this case, the display unit 24 will display the message “short circuit damage”.

в обмотке реле 31 будет равен нулю и оно срабатывает, а разность тока $$\Delta I$$

в обмотке реле 21 будет не равна нулю и оно сработает. При этом контакты 22 замкнется, а контакты 32 и 34 останутся в исходном положении. В результате в отключающей цепи 23 появится сигнал на отключение трансформатора. При этом блок 24 индикации высветит сообщение «повреждение короткой сети».If a break occurs in the circuit of one of the tires, for example, in flexible connections connecting a two-turn winding 10 to the furnace electrode, the current in this pair of tires and the two-turn winding 10 of the furnace transformer connected to it will be zero. Which will also lead to the same change in the distribution of the magnetic field of the scattering of the windings on both rods of the transformer. In this case, the electromotive force in the transducer 25 will be zero, and the electromotive forces of the upper and lower windings in the transducer 12 will not be equal to each other. In connection with this current $$I_{}$$$${}_1$$

in the winding of the relay 31 will be zero and it works, and the current difference $$\Delta I$$

in the winding of the relay 21 will not be zero and it will work. In this case, the contacts 22 will be closed, and the contacts 32 and 34 will remain in their original position. As a result, a trip signal for the transformer will appear in the trip circuit 23. In this case, the display unit 24 will display the message “short circuit damage”.

The technical and economic efficiency of the proposed method lies in the ability to detect not only winding short circuits in the windings of the furnace transformer, but also short circuits and open circuits in the bus network of the short network, as well as the ability to distinguish these types of damage and disconnect the transformer from the network in a timely manner. This will reduce the time and cost of emergency repairs.

Claims (1)

A method of protecting a single-phase furnace transformer with a short network in the form of a group of buses from electrical damage, in which the magnetic field of the transformer windings is measured in a plane perpendicular to the yokes of its core and passing through their middle, and if it is greater than zero, disconnect the transformer from the network and form signal "coil closure", characterized in that it additionally measure the magnetic field scattering at the upper and lower ends of the windings on one of the rods of the core of the transformer, compare them I’m waiting for myself, and if their difference is greater than zero, they form a signal to disconnect the transformer from the network, as well as a signal “damage to a short network”, which in turn is blocked when there is a signal “coil closure”.

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