JP2019067934A - Ac power transformer - Google Patents

Abstract

To provide an AC power transformer that can make a neutral point leakage current of a primary winding almost zero.SOLUTION: An AC power transformer includes a primary winding in which U, V, and W-phase windings 101u, 101v, and 101w are Y-connected, and the neutral point is grounded, a secondary winding having an A-seat on which the U-phase winding 102ua and the W-phase winding 102wa are roof-connected and a B-seat including a V-phase winding 102vb insulated from the A-seat, and a third winding in which U, V, Wand -phase windings 103u, 103v, 103w are delta-connected.SELECTED DRAWING: Figure 1

Description

  TECHNICAL FIELD The present invention relates to an AC electric power transformer provided in an AC electric power transformer substation which is used for an electric iron / AC electric power feeding system and which receives power from a system of an ultra high voltage direct grounding system.

  In an AC electric power transformer substation that receives power from a direct grounding system, it is necessary to make the primary winding of the feeding transformer Y-connected and to ground the neutral point, and the current mainstream is described in, for example, Patent Document 1 It has become a roof delta connection transformer. However, as a weak point of this transformer, a leakage current (apparent zero phase current) may flow to the neutral point of the primary Y winding due to the impedance irregularity of the secondary delta winding.

  FIG. 4 shows a configuration of a roof-delta connection transformer used in a substation for AC power transmission which receives power from a direct grounding system, and comprises a primary U-phase winding 201u and a primary V-phase winding which constitute a primary winding. 201 v, the primary W-phase winding 201 w is Y-connected, and its neutral point is grounded. Each end of each of the windings 201u, 201v, 201w on the opposite side to the neutral point is connected to a three-phase power source (system) of ultra high voltage (for example, 170 kV or more, 180 kV or more) not shown.

  The secondary winding A-seat is constructed by connecting the secondary A-seat U-phase winding 202ua and the secondary A-seat W-phase winding 202wa on a roof, and is connected to a feeding facility such as a feeder cable (not shown). .

  The secondary winding B-seat is insulated from the secondary winding A-seat, and the secondary B-seat U-phase winding 202ub, the secondary B-seat V-phase winding 202vb, and the secondary B-seat W-phase winding 202wb It is configured as delta connection (Δ connection).

  A feeding equipment 300 such as a feeder is connected between both ends of the secondary B-seat V-phase winding 202vb.

Current I _V1 flowing through the primary V-phase winding 201v of the primary winding to flow diverted to the primary U-phase winding 201u and primary W-phase winding _{201w (I U1, I W1)} , the neutral point current I _n Becomes I _n = I _V1 − (I _U1 + I _W1 ).

The secondary winding B locus of each winding 202ub, 202vb, the current I _U2, I _V2, I _W2 each flowing in 202Wb, current I _B flowing through the feeding circuit arrangement 300 each serve as a direction indicated by an arrow, I _B = I There is a relationship of _V 2 + I _U2 and I _U2 = I _W2 .

Patent No. 3825661 gazette

In the configuration of FIG. 4, the secondary winding B locus Δ connection (202ub, 202vb, 202wb) phase impedance (Zu, Zv, Zw) and the relationship of the neutral current I _n of the primary winding Y connection is, I _{n = (((Zu + Zw} ) -2Zv) / ((Zu + Zw) + Zv)) × I B , and the impedance of the secondary winding B locus Zu = Zv = if Zw neutral current I _n does not flow.

  However, since the secondary B-seat V-phase winding 202vb carries twice as much current as the other windings 202ub and 202wb, the wire diameters are different, and the respective phase impedances are not completely the same. Therefore, the ground leakage current flows to the neutral point of the primary winding.

  Although the device has been technically devised to reduce this value to a certain value or less, the apparent zero-phase current is flowing to the system side, which tends to be less preferable as the stability of the system.

  The present invention solves the above problem, and an object thereof is to provide an AC electric charging transformer capable of making the neutral point leakage current of the primary winding substantially zero.

In order to solve the above-mentioned subject, the transformer for alternating current power supply according to claim 1 is:
Primary winding with each phase of U, V and W connected by Y connection and the neutral point grounded
A secondary winding having a seat A having the U and W phases roof-connected and a seat B comprising a V phase insulated from the seat A;
A tertiary winding in which U, V and W phases are delta-connected,
It is characterized by having.

(1) According to the invention of claim 1, the V-phase current flowing to the secondary winding B seat is compensated by the V-phase current flowing to the primary winding and the V-phase current flowing to the tertiary winding, The U-phase and W-phase currents of the tertiary winding are subjected to flux compensation by the U-phase and W-phase currents of the primary winding.

  As a result, there is no surplus in the current divided from the V-phase to the U-phase and the W-phase of the primary winding, so that the neutral point leakage current of the primary winding can be made substantially zero.

  As a result, no apparent zero-phase current is generated on the system side, malfunctioning of the ground fault overcurrent relay on the system side can be prevented, and accurate operation value setting can be performed, and the stability on the ultra-high voltage system side is improved.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the transformer by embodiment of this invention. Explanatory drawing showing the electric current which flows into each part of the transformer by embodiment of this invention. Explanatory drawing which represented the electric current value which flows into each part of the transformer by embodiment of this invention with a unit method. The block diagram of the conventional roof delta connection transformer.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments.

  FIG. 1 shows the configuration of an AC electric charging transformer according to this embodiment, which includes a primary winding, a secondary winding (1), a secondary winding (2), and a tertiary winding. .

  In FIG. 1, a primary U-phase winding 101u, a primary V-phase winding 101v, and a primary W-phase winding 101w, which constitute a primary winding, are Y-connected, and their neutral point is grounded. Each end of each of the windings 101u, 101v, 101w opposite to the neutral point is connected to a three-phase power supply (system) of ultra high voltage (for example, 170 kV or more, 180 kV or more) not shown.

  The secondary winding A-seat (secondary winding (1)) is constructed by connecting the secondary A-seat U-phase winding 102ua and the secondary A-seat W-phase winding 102wa on the roof, and is not shown It is connected to a feeding facility (the output of the A seat is 60 kV, for example).

  The secondary winding B-seat (secondary winding (2)) is composed of a secondary B-seat V-phase winding 102vb (output is, for example, 60 kV) insulated from the secondary winding A-seat (the output is 60 kV). Feeding equipment such as a wire (not shown) is connected between both ends of the wire 102vb.

  The tertiary winding is configured by delta connection (Δ connection) of the tertiary U-phase winding 103u, the tertiary V-phase winding 103v, and the tertiary W-phase winding 103w.

  The current flowing in each winding of FIG. 1 is shown in FIG. Reference numeral 300 in FIG. 2 denotes a feeding facility connected between both ends of the secondary B-seat V-phase winding 102vb.

2, since current I _V1 flowing through the primary V-phase winding 101v of the primary winding flows diverted to the primary U-phase winding 101u and primary W-phase winding _{101w (I U1, I W1)} , neutral point current I _n is I _n = I _V1 - a (I _U1 + I _W1), the I _U1 and I total I _V1 if they match the neutral point current I _n = 0 in _W1.

Further, the current I _B flowing through the feeding equipment 300 is equal to the current I _{V2 of the} secondary B-seat V-phase winding 102 vb (I _B = I _V2 ).

Since the tertiary winding is a delta connection, the current I _U3 flowing through the tertiary U-phase winding 103 u, the current I _V3 flowing through the tertiary V-phase winding 103 v, and the current I _W3 flowing through the tertiary W-phase winding 103 w are all equal. _U3 = I _V3 = I _W3 .

In the connection scheme of FIG. 2, the current corresponding to I _V2 (= I _B ) is divided into the primary current I _V1 and the tertiary current I _V3 . Since I _U3 = I _V3 = I _W3 , the primary current corresponding to I _U3 and I _W3 is also I _U1 = I _W1 .

Current ratio of I _V1 and I _V3 (p.u. (perunit: unit normal)) of 2: As the 1 relationship, for branching the primary current also _{I U1 = I W1 = 0.5I V1} , of each winding The current is stable in this state, so the primary winding current has no surplus at the neutral point, and almost no neutral point current flows.

  These operations will be described with reference to FIG. 3 in which the direction of the current flowing in each part of FIG. 2 is indicated by an arrow and the current value is indicated by a unit method. In FIG. 3, the arrangement of the primary winding and the tertiary winding in FIG. 2 is interchanged and illustrated.

  Secondary winding A-seat (secondary A-seat U-phase winding 102ua and secondary A-seat W-phase winding 102wa) carries a line voltage between two phases (U-phase and W-phase) and a wire (feeding equipment 300) And the B-seat of the secondary winding (secondary B-seat V-phase winding 102vb) sends a phase voltage of only one phase (V-phase) to the feeder (the feeding equipment 300).

  The phase difference between the A and B seats of the secondary winding is 90 ° as in the conventional roof delta connection transformer.

  When the loads on the A and B seats of the secondary winding are equal, the primary current balances in each phase. The tertiary winding has the effect of cleanly halving the shunt of the primary winding.

  That is, the current of 1.5 pu flowing in the secondary B-seat V-phase winding 102vb is compensated for the magnetic flux by 1.0 pu flowing in the primary V-phase winding 101v and 0.5 pu flowing in the tertiary V-phase winding 103v.

  Since the tertiary windings are delta connections, the currents flowing through the phase windings 103u, 103v and 103w are all equal to 0.5 pu. Therefore, the current of 0.5 pu flowing in each of the tertiary U-phase winding 103 u and the tertiary W-phase winding 103 w is compensated by 0.5 pu flowing in each of the primary U-phase winding 101 u and the primary W-phase winding 101 w. .

  In the primary winding, the current of 1.0 pu of primary V-phase winding 101 v is split into 0.5 pu each of primary U-phase winding 101 u and primary W-phase winding 101 w, so there is no surplus, and the neutral point leakage current (There is no such a neutral point leakage current because the above-mentioned current distribution is always obtained from the concept of the above-mentioned magnetic flux compensation).

  The AC transformer transformer according to this embodiment has a simple phase voltage at the B-seat output of the secondary winding, and the winding structure is simple as compared with the conventional transformer.

  As described above, according to the present embodiment, since the primary Y winding neutral point leakage current caused by the B-seat load current hardly flows even if the impedances of the respective windings are somewhat uneven, the apparent zero in the system side Since no phase current is generated, malfunction of the ground fault overcurrent relay on the system side can be prevented and accurate operation value setting can be performed, and the stability of the extra-high voltage system can be improved.

101u ... primary U-phase winding 101v ... primary V-phase winding 101w ... primary W-phase winding 102ua ... secondary A-seat U-phase winding 102 wa ... secondary A-seat W-phase winding 102vb ... secondary B-seat V-phase winding Wire 103 u ... tertiary U-phase winding 103 v ... tertiary V-phase winding 103 w ... tertiary W-phase winding

Claims (1)

Primary winding with each phase of U, V and W connected by Y connection and the neutral point grounded
A secondary winding having a seat A having the U and W phases roof-connected and a seat B comprising a V phase insulated from the seat A;
A tertiary winding in which U, V and W phases are delta-connected,
AC transformer for transformers characterized by having.

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