JPH0432620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a transformer, and more particularly to an improvement in a tap winding arrester for a tap winding provided in a high voltage winding.

[Technical background of the invention and its problems]

In order to adjust the operating voltage of the transformer to variations in the system voltage, transformers are typically provided with a voltage-free tap changer and/or an on-load tap changer. For large capacity transformers, one tap changer with multiple separate switching structures may be used, or multiple tap changers may be used in parallel if the passing current exceeds the current carrying or switching capacity of the tap changer. There is. In this case, the load current is 1
It is necessary to devise a current transformer winding so that the current is evenly divided to each separate switching mechanism of the two tap changers or to each tap changer used in parallel.

On the other hand, when lightning impulse voltage is applied to the transformer terminals, potential oscillations occur between the windings within the windings due to inductance and capacitance within and between the windings. It is necessary to suppress the voltage generated in the connected tap windings to within the dielectric strength value of the tap changer. For this reason,
If the voltage generated in the tap winding exceeds this dielectric strength value, a tap winding protection arrester (hereinafter abbreviated as tap protection arrester) is constructed by connecting the necessary number of nonlinear resistance elements in series for insulation protection. This generated voltage can be suppressed by connecting the tap winding in parallel with the tap winding. As this type of device, for example, Japanese Patent Laid-Open No. 80109/1983 is known.

Conventional wiring diagrams are shown in FIGS. 2 and 3 of the present invention. That is, a low voltage winding 1 and a high voltage winding 2 are concentrically wound around the iron core 5, and this high voltage winding 2 is
It is divided into two at a point to form high voltage windings 2 _-1 and 2 _-2 , and tap windings 3 and 4 are wound concentrically around each of the high voltage windings 2 -1 and 2 -2. And P near the center of the high voltage winding 2
The point is connected to the line terminal U and is divided into approximately two parts. Tap changers 6 and 7 are connected to the tap windings 3 and 4, respectively, and a changeover contact 6 is connected to the tap windings 3 and 4, respectively.
a and 7a are collectively connected to the neutral point N.

In FIG. 2, points P ₁ and Q of the tap winding ₃ are connected to terminals R and R ₁ of the tap protection arrester 8 via connections 11 and 11 _-1 , respectively. In addition, a tap protection arrester 9 is installed between the Q ₂ and _P points of the tap winding 4.
The terminals S _-1 and S of are connected via connecting wires 12 _-1 and 12, respectively.

Furthermore, in Fig. 3, points P ₁ and P ₂ are connected together to terminal R via connection line 13, and points Q ₁ and Q ₂ are connected together to terminal S via connection line 14. configured.

In FIG. 2, the current flowing from the line terminal U is shunted to the _P1 point and P2 point side of the high voltage winding ₂ , and the current flowing to the _P1 point side is transferred from the tap winding 3 to the tap changer 6. It flows to the neutral point N via . Also
The current shunted to the _P2 point side flows from the tap winding 4 to the neutral point N via the tap changer 7. The branching of current to the tap changer 6 and tap changer 7 is determined by the resistance value of the windings and the impedance between each winding.
The shunt is determined by the high voltage winding 2 since the number of turns of the high voltage winding 2 is much larger than the normal tap windings 3, 4. In this way, high voltage winding 2
The high voltage windings 2 _-1 and 2 _-2 are symmetrically divided into two, and the current branches of each are balanced. are almost equal.

In addition, in FIG. 3, points P ₁ and P ₂ are connected together by a connecting wire 13, and points Q ₁ and Q ₂ are connected together by a connecting wire 14 to terminals R and S of the tap protection arrester 10. By connecting them, one tap protection arrester 10 can be provided. However, in this case, because the points P ₁ and P ₂ are connected, the shunt between the tap windings 3 and 4 and between the tap changers 6 and 7 is not determined by the high voltage winding 2. It is determined by the impedance between the tap winding and other windings and between the tap windings. In general, the tap windings 3 and 4 have fewer turns and a smaller winding height than the high voltage winding 2, so the above impedance is easily affected by connection wires and manufacturing errors. 4 tends to cause imbalance. Furthermore, a closed loop is formed such as tap winding 3 → Q ₁ , Q ₂ → tap winding 4 → P ₁ , P ₂ → tap winding 3, and there is a risk that circulating current will flow in the tap winding due to unbalance of the shunt. occurs.

To avoid this, conventionally, when tap windings and tap changers are divided into multiple parts, the number of tap protection arresters required to protect the tap changers from abnormal voltage is equal to the number of tap winding divisions. However, in the above explanation, there is a problem that requires two sets, which should be improved.

[Purpose of the invention]

The present invention has been made in consideration of the above, and its purpose is to configure tap windings into multiple parallel circuits in order to shunt load current to multiple tap changers used in parallel. In this case, it is an object of the present invention to provide a transformer that can reduce the number of tap protection arresters provided to protect a tap changer from abnormal voltage.

[Summary of the invention]

According to the present invention, in order to achieve such an objective,
A tap winding with two circuits in parallel is connected to the high voltage winding, and the minimum required number of nonlinear resistance elements (Z) are connected in series to the first tap winding. A tap winding protective lightning arrester is formed by connecting at least one non-linear resistance element of X number, and connecting at least one non-linear resistance element of X number to the other end, and forming a tap winding protection arrester. Both ends of the line protection lightning arrester are designated as point A and point D, the one closer to point A among the Z ends is designated as point C, the one closer to point D is designated as point B, and one end of the first tap winding is designated as point A. Connect the other end to point B, connect the end of the second tap winding with the same polarity as the point A side of the first tap winding to point C, and connect the other end to point D. The present invention is characterized in that the tap winding protective lightning arrester is downsized by providing one set of tap winding protective lightning arresters.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The same parts as in FIGS. 2 and 3 are given the same reference numerals. That is, the low voltage winding 1 and the high voltage winding 2 are wound concentrically around the iron core 5. The high voltage winding 2 is divided approximately into two at point P to form high voltage windings 2 _-1 and 2 _-2 , and tap windings 3 and 4 are concentrically wound around each of the high voltage windings 2 -1 and 2 -2. Also, high voltage winding 2
Point P, which is located approximately in the center of the line, is connected to the line terminal U, and the line is divided into approximately two parts. Tap changers 6 and 7 are connected to the tap windings 3 and 4, respectively, and the changeover contacts 6a and 7a are connected to the neutral point N.
connected to.

The tap winding protection arrester 13 (hereinafter again abbreviated as tap protection arrester) is formed by connecting a plurality of non-linear resistance elements 15 (hereinafter abbreviated as elements) in series. This element 15 is made of, for example, TNR (trade name), which is a nonlinear resistor having excellent nonlinearity and containing zinc oxide as a main component. This element 1
Connect Z pieces of 5 in series, and let the two ends be point C and point B. Then, one or more elements 15 are connected to both ends of Z elements 15 to form a tap winding protection arrester 1.
3 (hereinafter abbreviated as tap protection arrester), one end of which is designated as point A, and the other end designated as D, and at least one X element 15 is connected between point A and point C. In addition, at least one element 15, the number of which is less than X, is connected between point C and point B.

In FIG. 1, an equal number of N elements 15 are connected to both ends of Z elements.

Point P _and point _Q , which are both terminals of the tap winding 3, are connected to points A and B of the tap protection arrester 13 via connecting wires 16 and 17, respectively. Further, points _Q2 and _P2 , which are both terminals of the tap winding 4, are connected to points D and C of the tap protection arrester 13 via connecting wires 18 and 19, respectively. At this time, the _P2 point of the tap winding 4, which has the same polarity as the P1 point connected to the A point side of the tap winding ₃ , is connected to the C point.

Next, the effects of the present invention will be explained. _P1
Since N elements 15 are connected between the point and the _P2 point and between the _Q1 point and the _Q2 point, Z elements 15 are connected to each of the tap windings 3 and 4 in common. The circulating current between the tap windings 3 and 4 is kept extremely low, and the shunt current between the tap windings 3 and 4 and between the tap changers 6 and 7 is transferred to the high voltage winding 2. Therefore, no unbalanced flow occurs.

Furthermore, the number of elements 15 inserted between points A and C and between points B and D of the tap protection arrester 13 was set to N, but normally the number of elements 15 inserted between points A and C and between points B and D is N. Since the potentials are approximately equal, one element 15 is sufficient.

Furthermore, since Z elements 15 are shared for protecting the tap changers 6 and 7, the number of elements 15 required is (Z+2) when N=1. Conventionally, approximately
Two sets of 2Z or Z pieces are required, and in the past, if one set was shared, a circulating current would flow, causing problems, but according to the present invention, the tap protection arrester 13 is smaller than the conventional one. can be used. In other words, the transformer can be made economical and downsized.

〔Effect of the invention〕

As explained above, according to the present invention, the tap winding and the tap changer are divided into two sets, and the number of sets of tap winding protection arresters and the number of required nonlinear resistance elements are approximately halved. It is economical and
It is also possible to provide a downsized transformer.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram of a transformer according to the present invention, and FIGS. 2 and 3 are wiring diagrams of a conventional transformer. 1...Low voltage winding, 2, 2 _-1 , 2 _-2 ...High voltage winding, 3, 4...Tap winding, 6,7...Tap switch, 13...Tap winding protection lightning arrester , 15...
...Non-linear resistance elements, 16, 17, 18, 19...
... Connection wires, A, B, C, D... Connection points between the tap winding and the tap winding protection arrester.

Claims (1)

[Claims] 1. In a transformer equipped with a tap winding in which two circuits are connected in parallel, (Z + One end of the first tap winding is connected to one end point A, the other end of the first tap winding is connected to the other end B opposite to the point A, and the first tap winding One end of the second tap winding, which has the same polarity as point A, is connected to point A.
Connect X non-linear resistance elements from the point and connect them to a distant point C, and connect the other end of the second tap winding to the opposite end to the point A, and at least one non-linear resistor from the point B. A transformer characterized in that it is equipped with a tap winding protection lightning arrester in which at least X non-linear resistance elements are connected to a distant point D.