阅读说明：本技术 一种采用电压差的变压器匝间短路检测器 (Transformer turn-to-turn short circuit detector adopting voltage difference ) 是由 范宝龙 于 2019-09-20 设计创作，主要内容包括：本发明公开了一种改进的变压器通过差动电压的中间短路检测装置包括单相变压器(TM)。单相变压器(TM)包括高压线圈(K)和低压线圈(N)。电压互感器(PT)被定位在单相的高电压侧变压器(TM)。高压线圈(K)的抽头(K1)的两个分支与第一转换器(Q’)的输入连接,并且获得第一电压(U1’)。变压器(PT)的次级侧连接第二个转换器(Q)的输入端和第二个电压(U1)获得第一电压(U1’)和第二电压(U1),并且当电压差高于预定的初级阈值时,确定初级侧的匝间短路故障。低压线圈(N)的抽头(N1)和低压线圈(N)的一个端子与第三转换器(M’)的输入和第三电压(U2’)连接。得到低压(N)的两个端子与第四转换器(M)的输入端连接,得到第四电压(U2),第三电压(U2’)和第四电压(U2)电压(U2比较,并且当电压差高于预定的次级阈值时,确定次级侧的匝间短路故障。(The invention discloses an improved transformer passing differential voltage intermediate short circuit detection device which comprises a single-phase Transformer (TM). The single-phase Transformer (TM) comprises a high-voltage coil (K) and a low-voltage coil (N). The Potential Transformer (PT) is positioned at the high voltage side Transformer (TM) of the single phase. Two branches of a tap (K1) of the high voltage coil (K) are connected with the input of the first converter (Q ') and obtain a first voltage (U1'). The secondary side of the transformer (PT) is connected to the input of the second converter (Q) and to a second voltage (U1) to obtain a first voltage (U1') and a second voltage (U1), and when the voltage difference is higher than a predetermined primary threshold, a turn-to-turn short fault on the primary side is determined. The tap (N1) of the low voltage coil (N) and one terminal of the low voltage coil (N) are connected to the input of the third converter (M ') and to a third voltage (U2'). The two terminals that get the low voltage (N) are connected to the input of the fourth converter (M), a fourth voltage (U2) is got, the third voltage (U2') and the fourth voltage (U2) voltage (U2) are compared, and when the voltage difference is higher than a predetermined secondary threshold, a turn-to-turn short fault on the secondary side is determined.)

1. An improved transformer turn-to-turn short circuit detector, employing voltage differentiation, comprising a single-phase transformer in a single-phase high voltage power supply circuit, the single-phase transformer comprising a high voltage winding and a low voltage winding, a voltage transformer providing a high voltage on the high voltage side of the single-phase transformer, drawing the high voltage from a tap of the high voltage winding connected to a first converter and converting to a first voltage by the first converter, drawing a second voltage from a second converter, the voltage transformer being connected to and converting to the second voltage by the second converter; wherein a first comparison is made between a first voltage and a second voltage and a first result is output, then a low voltage is taken from a tap connected to a low voltage winding of a third converter and converted into a third voltage by the third converter and a second comparison is made between a third voltage converted by a fourth converter and a fourth voltage, and a second result is output from a full voltage of the low voltage winding, and wherein the first result and the second result are compared with a predetermined value to determine whether a short circuit occurs.

Technical Field

The invention relates to a transformer turn-to-turn short circuit detector utilizing voltage difference, in particular to a detector for detecting and protecting transformer turn-to-turn short circuit.

Background

As cities expand, the number and capacity of power transformers are rapidly increasing. However, at present, except for (1) high-capacity transformers, (2) transformers with special requirements are equipped with current-pilot differential detection mechanisms to provide inter-turn and inter-phase severe short-circuit protection therein, or (3) medium-capacity oil-immersed transformers protected by Buchholz relays installed, all other oil-immersed or dry-type transformers below 6300KVA are not equipped with protection circuits for detecting early faults of inter-turn or inter-phase short-circuits. Generally, the following problems exist in the devices which are not provided with turn-to-turn or phase-to-phase short circuit protection according to relevant relay protection design specifications: one, when an inter-turn or inter-layer short circuit occurs for internal or external reasons, the transformer cannot find the initial low energy fault condition, which enables the faults to develop further until they develop into a serious accident of a high capacity short circuit energy condition, for example as a fire, triggering a protective action of the high voltage input terminals. Therefore, the short circuit problem cannot be solved early and in time, and the problem is enlarged. Repairing the transformer after a fault has propagated is very difficult, especially when the fault destroys the current overflow protection of the substation at a higher level. This can seriously compromise the safety of the power supply and personal safety. Second, once the turn-to-turn short circuit occurs and the transformer cannot analyze and identify the fault type, it is difficult to provide appropriate corresponding protection for the transformer. Therefore, the present inventors have designed a transformer turn-to-turn short circuit detector using a voltage difference, and applied to chinese patent No. 200820081814.2. However, the technical solution of the patent has the following disadvantages: (1) the third coil must be mounted inside the transformer body. However, it is difficult to install the third coil inside the transformer body after the transformer coil is installed, resulting in a limited range of applications because the signal cannot be extracted, and (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to satisfy the requirement of differential protection. The present inventor has designed a transformer turn-to-turn short circuit detector using a voltage difference, and applied for chinese patent (No. 200820081814.2). However, the technical solution of the patent has the following disadvantages: (1) the third coil must be mounted inside the transformer body. However, it is difficult to install the third coil inside the transformer body after the transformer coil is installed, resulting in a limited range of applications because the signal cannot be extracted, and (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to satisfy the requirement of differential protection. The present inventor has designed a transformer turn-to-turn short circuit detector using a voltage difference, and applied for chinese patent (No. 200820081814.2). However, the technical solution of the patent has the following disadvantages: (1) the third coil must be mounted inside the transformer body. However, it is difficult to install the third coil inside the transformer body after the transformer coil is installed, resulting in a limited range of applications because the signal cannot be extracted, and (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to satisfy the requirement of differential protection. 200820081814.2). However, the technical solution of the patent has the following disadvantages: (1) the third coil must be mounted inside the transformer body. However, it is difficult to install the third coil inside the transformer body after the transformer coil is installed, resulting in a limited range of applications because the signal cannot be extracted, and (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to satisfy the requirement of differential protection. 200820081814.2). However, the technical solution of the patent has the following disadvantages: (1) the third coil must be mounted inside the transformer body. However, it is difficult to install the third coil inside the transformer body after the transformer coil is installed, resulting in a limited range of applications because the signal cannot be extracted, and (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to satisfy the requirement of differential protection. And (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to meet the requirements of differential protection. And (2) the signal detected from the third coil may be affected by higher or lower load and load performance (resistance, capacity and inductance), and thus it is difficult to meet the requirements of differential protection.

(3) The conversion using the same core in the comparison of the sampled voltage signal in the original patent with the voltage signal of the main winding may result in a short circuit of the sampled signal and no signal comparison can be achieved. In addition, it is inefficient and has poor accuracy.

Disclosure of Invention

It is an object of the present invention to overcome the disadvantages of the prior art by providing an improved, efficient and highly accurate transformer turn-to-turn short detector using voltage differences. The improved detector is manufacturable, immune to higher or lower loads and load performance (resistance, capacity and inductance), and meets differential protection requirements. The sampled voltage signal from the detector is compared with the voltage signal of the primary winding converted by the separate converter to avoid affecting the test signal.

The technical scheme of the improved detector for detecting the turn-to-turn short circuit of the transformer by adopting the voltage difference is as follows. An improved transformer turn-to-turn short circuit detector, using voltage differentials, includes a single-phase Transformer (TM) in a single-phase high-voltage power circuit. The single-phase Transformer (TM) comprises a high-voltage winding (K) and a low-voltage winding (N). A voltage transformer (PT) is provided on the high-voltage side of the single-phase Transformer (TM). A high voltage is tapped/extracted from a tap (K1) of the high voltage winding (K). A tap (K1) high voltage winding (K) is connected to an input of a first converter (Q '), and a voltage at an output of the first converter (Q ') is a first voltage (U1 '), a second voltage is drawn from a secondary output side of a voltage transformer (PT), the second voltage being connected to an input of a second converter (Q). two outputs of the first converter (Q ') and the second converter (Q) are connected to a module to distinguish a turn-to-turn short circuit at the first output side.A first voltage (U1 ') and a second voltage (U1) are compared in the module.

A low voltage is tapped from a tap (N1) of the low voltage winding (N) connected to the input of a third converter (M '), and the voltage at the output of the third converter (M ') is a third voltage (U2 '). Both ends of the low voltage winding (N) are connected to the input of a fourth converter (M), and the voltage at the output of said fourth converter (M) is a fourth voltage (U2). Two outputs of the third converter (M') and the fourth converter (M) are connected to the module to distinguish turn-to-turn short circuits on the secondary output side. The third voltage (U2') and the fourth voltage (U2) are compared in the module. When the voltage difference is greater than a preset secondary threshold, a turn-to-turn short on the secondary output side may be determined.

Furthermore, the tap (K1) of the high voltage winding (K) comprises two additional connectors from the middle winding of the high voltage winding (K) and said two additional connectors are connected to the input of the first converter (Q').

Furthermore, the tap (N1) from the low voltage winding (N) is an auxiliary connector from the middle winding of the low voltage winding (N). One end of the auxiliary connector and the low voltage winding (N) is connected to the input of the third converter (M').

The electromechanical detection process of the transformer turn-to-turn short circuit detector improved by the voltage difference of the present invention is as follows. A separate dedicated potential transformer PT is installed on the high side of the protected transformer (the potential transformer can be adjusted on the gear required for the protected transformer). The sampled voltage is taken/extracted from the high and low voltage windings or any other winding, and a short circuit condition needs to be detected. The voltage may be obtained from taps of the protected winding of the transformer or preset in the manufacture of the transformer. 1' and the voltage transformer will convert the voltage U1. Theoretically, the values of U1' and U1 should be the same. Furthermore, a partial voltage is drawn from the transformer, which secondary output side is converted into a voltage U2 by converting the sampled voltage from the secondary output side at the secondary output, and compared with the converted voltage U by 2 for the correlation' comparison. There are two comparison processes as follows. First, the secondary output side voltage of the voltage transformer is compared with the selected voltage U1 ". When the voltage difference is less than the preset value, it recognizes that no short circuit or accident occurs in the primary winding. And when the comparison result exceeds a preset rated range, a protection signal is output to trigger a protection system, and the short circuit or the accident of the high-voltage winding of the transformer is recognized. Next, the converted voltage U2 is compared with the voltage U2'. When the voltage difference is less than the specific value, no action signal is output. When the voltage difference exceeds the allowable upper limit, a protection signal is output, and the transformer is recognized to have an accident.

An advantage of the present invention is that it is not affected by higher or lower loads and load performance (resistance, capacity and inductance). The invention meets the requirement of differential protection. The sampled voltage signal from the detector is effectively and accurately compared with the voltage signal of the primary winding converted by the independent converter to avoid affecting the test signal.

Drawings

Fig. 1 is a circuit diagram of a transformer turn-to-turn short detector improved using voltage differences.

Detailed Description

The present invention relates to an improved detector for transformer turn-to-turn short using voltage differences as shown in fig. 1. The improved detector includes a single phase Transformer (TM) in a single phase high voltage power supply circuit. The single-phase Transformer (TM) comprises a high-voltage winding (K) and a low-voltage winding (N). The voltage transformer (PT) is arranged on the high-voltage side of the single-phase Transformer (TM). A high voltage is drawn from a tap (K1) of the high voltage winding (K). A tap (K1) of the high voltage winding (K) is connected to an input of a first converter (Q '), and a voltage at an output of the first converter (Q ') is a first voltage (U1) '). A second voltage is drawn from the secondary output side of the Potential Transformer (PT) and is connected to the input of the second converter (Q). Two outputs of the first converter (Q') and the second converter (Q) are connected to the module to distinguish turn-to-turn short circuits on the first output side. The first voltage (U1') and the second voltage (U1) are compared in the module. When the voltage difference is greater than a preset first threshold, a turn-to-turn short on the first output side may be determined.

A low voltage is tapped from a tap (N1) of the low voltage winding (N) connected to the input of a third converter (M '), and the voltage at the output of the third converter (M ') is a third voltage (U2 '). Both ends of the low voltage winding (N) are connected to the input of a fourth converter (M), and the voltage at the output of said fourth converter (M) is a fourth voltage (U2). Two outputs of the third converter (M') and the fourth converter (M) are connected to the module to distinguish turn-to-turn short circuits on the secondary output side. The third voltage (U2') and the fourth voltage (U2) are compared in the module. When the voltage difference is greater than a preset secondary threshold, a turn-to-turn short on the secondary output side may be determined.

The tap (K1) of the high voltage winding (K) comprises two additional connectors from the middle winding of the high voltage winding (K) and said two additional connectors are connected to the input of the first converter (Q').

The tap (N1) from the low voltage winding (N) is an auxiliary connector from the middle winding of the low voltage winding (N). One end of the auxiliary connector and the low voltage winding (N) is connected to the input of the third converter (M').

The electromechanical detection process of the transformer turn-to-turn short circuit detector improved by the voltage difference of the present invention is as follows. A separate dedicated potential transformer PT is installed on the high side of the protected transformer (the potential transformer can be adjusted on the gear required for the protected transformer). The sampled voltage is obtained from the high and low voltage windings or any other winding and a short circuit condition needs to be detected. The voltage may be obtained from the taps of the protected windings or preset in the manufacture of the transformer. The above voltages are fed to a voltage converter (the power consumption of the voltage converter should not affect the detection and comparison accuracy requirements), the sample voltage is converted into U1' and a voltage transformer is used for converting the voltage into U1. Theoretically, the values of U1' and U1 should be the same. Furthermore, a partial voltage is drawn from the transformer, which secondary output side is converted into a voltage U2 by converting the sampled voltage from the secondary output side at the secondary output and comparing with the correlation of the converted voltage U2'.

There are two comparison processes as follows: 1. a comparison is made between the secondary output side voltage of the voltage transformer and the selected voltage U1'. When the voltage difference is less than the preset value, it can be recognized that no short circuit or accident has occurred in the primary winding. And when the comparison result exceeds a preset rated range, a protection signal is output to trigger a protection system, and the short circuit or the accident of the high-voltage winding of the transformer is recognized. 2. The converted voltage U2 is compared to the voltage U2 ". When the voltage difference is less than the specific value, no action signal is output. When the voltage difference exceeds the allowable upper limit, a protection signal will be output. It is recognized that an accident has occurred to the transformer. The circuit is able to identify all short circuit conditions and output certain fault signals, in particular recognizing that several faults are characterized as follows: (1) the turn-to-turn short circuit is intermittent during the early stages of the transformer turn-to-turn short circuit. A de-energized conductor with a small amount of short circuit energy and immediate actuation duration. The change in the number of turns affects the transformation ratio due to intermittent inter-turn accidents. Thus, the processing of the signal will recognize the occurrence of the early fault and avoid fault propagation. (2) Recognizing the instantaneous high resistance condition of the accident and outputting an accident signal. When a short circuit occurs in the transformer winding, the wires and conductors will burn out within a certain time. However, the burnout is not in a steady state, and due to the high voltage and electromagnetic force, the burnout portion will be melted again by arc welding at the place where the insulation is broken. The fused wire will then be broken again by a current surge when blown. This alternation occurs very quickly. At this stage, the accident will only generate a small amount of energy, since no short circuit will occur in the plurality of windings. However, variations in the transformer ratio can cause substantial variations in winding opening and voltage differential circuit fault signal extraction. (3) When certain windings of the transformer are disabled, open or short circuited, the change in the number of windings affects the transformation ratio, resulting in a voltage difference output short circuit signal. After comparing the signals converted from the partial voltages and the comparable signals converted from the full voltages, the signal characteristics can be used to identify the sequence of accident status and accident severity. Since the accident status comes from the high or low pressure side of each stage, we can not only identify whether the accident occurred at high or low pressure, but also determine the stage of the accident.