JPS64894B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protection device for a phase shifting transformer connected between a power system and a thyristor load.

Conventionally, there has been a device of this type as shown in FIG. The phase shift transformer 1 has windings wa, wb,
It has a winding 2 in which wc is star-connected, and the windings wa ₁ , wb ₁ , wc ₁ are star-connected on the secondary side, and these windings wa ₁ , wb ₁ , wc ₁ are connected to a phase shifter. Winding wb ₂ ,
It has a phase shifting winding 3 in which wc ₂ and wa ₂ are connected in series.
One end of the windings wa, wb, wc forming the center O ₁ of the winding 2 is grounded, and their other ends are connected to the first connection wires 2a, 2b, 2c of the power system to receive voltages V _A , V _B ，
V _C is applied. One ends of the windings wa ₁ , wb ₁ , wc ₁ forming the center O ₂ of the phase shift winding 3 are grounded via a resistor 4 . The other ends of the windings wb ₂ , wc ₂ , wa ₂ are connected to a thyristor load (not shown) via second connection lines 3a, 3b, 3c. Winding wa ₁ , wb ₁ , wc ₁
generates voltages V _A ′, V _B ′, V _C ′, and windings wa ₂ ,
Since wb ₂ and wc ₂ generate −V _A ″, −V _B ″, and −V _C ″, by combining these, voltages V _A , V _B , and Voltages Va, Vb, and Vc with a phase difference θ are applied from V _C.

The currents in the second connection lines 3a, 3b, 3c are introduced into the phase shifter 6 via current transformers 5a, 5b, 5c, and after receiving compensation corresponding to the phase difference θ, current signals 6a, 6b , 6c and are input to the protective relay 7. The protective relay 7 connects the first connection wires 2a, 2
This is a normal differential protection relay that monitors abnormalities in the phase shift transformer 1 by introducing currents b and 2c through current transformers 8a, 8b, and 8c and comparing them with current signals 6a and 6b.

By the way, there are also phase shift transformers as shown in FIGS. 2 and 3. The phase-shifting transformer 9 has on the primary side a winding 2 identical to that of FIG. However, the phase shifting winding 10 on the secondary side has windings wa ₁ , wb ₁ , wc ₁ in addition to the phase shifting winding shown in FIG.
It has a configuration in which wc ₃ , wa ₃ , and wb ₃ are connected in series, and generates voltages −V _C ″, −V _A ″, −V _B ″ with a phase difference of −θ, and windings wa ₁ , wb ₁ , wc ₁ voltage V _A ′, V _B ′, V _C ′
As a result of the combination of
Apply Va′, Vb′, and Vc′.

As shown in Figure 2, a polyphase phase shift transformer that generates voltages with phase differences θ and -θ can be protected by a three-phase input protective relay device as shown in Figure 1. I can't.

In other words, in the protective relay device shown in Fig. 2, if a short circuit occurs internally, the voltages V _A ,
If a fault current flows due to a voltage vector unrelated to the phase difference θ between V _B , V _C and the voltages Va, Vb, and Vc, and this fault current is compensated by the phase shifter 6 in accordance with the phase difference θ, the phase shift There was a problem that phase matching with the current flowing to the primary side of the transformer 1 could not be achieved, and the protective relay 7 would malfunction.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and provides a protective joint that can provide highly reliable protective operation even if the phase shift transformer to be protected is a polyphase type. The purpose is to provide electrical equipment.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 4, the phase shift transformer 9 is the one shown in FIG.
c is the first current transformer 8a, 8b, 8 with Y-Δ connection.
c is provided, and the second connection wires 3a, 3 on the secondary side
b, 3c are Y-Δ connected second current transformers 11a,
11b, 11c are provided, and the third connection wires 10a, 10b, 10c on the secondary side are provided with a third Y-Δ connection.
Current transformers 12a, 12b, and 12c are provided.
The secondary sides of the first current transformers 8a, 8b, 8c are Δ-connected, and by transforming and combining the currents Ia, Ib, and Ic, the first connecting lines 2ab, 2bc, and 2ca are connected between each phase. Derive the primary currents Ia-Ib, Ib-Ic, and Ic-Ia. The second current transformers 11a, 11b, 11c are
The secondary side is Δ connected, and the currents Iu ₁ , Iv ₁ , Iw ₁
The second connection line 3 is created by changing the current and combining the
The current between each phase in ab, 3cb, and 3ca is Iu ₁ − Iv ₁ = Iuv ₁ ,
Derive Iv ₁ − Iw ₁ = Ivw ₁ and Iw ₁ − Iu ₁ = Iwu ₁ .
The secondary sides of the third current transformers 12a, 12b, 12c are also Δ-connected, and by transforming and combining the currents Iu ₂ , Iv ₂ , Iw ₂ , the third connecting lines 10ab, 1
Current between each phase at 0bc, 10ca Iu ₂ - Iv ₂ = Iuv ₂ , Iv ₂
−Iw ₂ =Ivw ₂ , Iw ₂ −Iu ₂ =Iwu ₂ are derived. 1st
The overcurrent detector 13 connects the second connection wires 3ab, 3bc,
Currents Iuv ₁ , Ivw ₁ , and Iwu ₁ of 3ca are introduced to respond to overcurrent exceeding a predetermined value. Further, the second overcurrent detector 14 connects the third connection wires 10ab, 10bc, 10ca.
The currents Iuv ₂ , Ivw ₂ , and Iwu ₂ are introduced to respond to overcurrents exceeding a predetermined value. The first phase shifter 15 has a current
The phases of Iuv ₁ , Ivw ₁ , and Iwu ₁ are shifted by −θ.
Further, the second phase shifter 16 has currents Iuv ₂ , Ivw ₂ ,
Shift the phase of Iwu ₂ by θ. Protective relay 7
inputs the combined output currents of the first and second phase shifters 15 and 16, and also connects the first connection line 2.
The currents Ia-Ib, Ib-Ic, and Ic-Ia of ab, 2bc, and 2ca are inputted and compared, and when an abnormality is detected, a signal 7a is output. Signal 7a is logic circuit 1
7 is input.

FIG. 5 is a block diagram of logic circuit 17. Signals 13a and 14a output from the first and second overcurrent detectors 13 and 14 and indicating their responses are input to the AND gate 18;
outputs a signal 18a. The AND gate 19 logically ANDs the inverted logic of the signal 18a and the signal 7a indicating the operation of the protective relay device 7, and outputs a signal 17a for protecting the phase shift transformer 9.

The operation will be explained. When each current flowing through the second and third connection lines 3a, 3b, 3c, 10a, 10b, and 10c is normal, the first and second overcurrent detectors 13 and 14 do not respond, and the signal 1
3a and 14a are not output. In addition, since the protective relay 7 maintains a balanced relationship between the current from the first connection lines 2ab, 2bc, and 2ca and the combined current of the outputs of the first and second phase shifters 15 and 16, the signal 7a is not output. Therefore, logic circuit 1
7 does not output the signal 17a, and the protective relay device does not start the protective operation.

Next, if accident F ₁ occurs as shown in the diagram,
The first overcurrent detector 13 responds and outputs a signal 13a. Similarly, if accident F ₂ occurs,
The second overcurrent detector 14 responds and outputs a signal 14a. However, in both cases, the protective relay 7
does not respond because both inputs are balanced, and the signal 7
Do not output a. Therefore, the logic circuit 17 receives the signal 1
7a is not output.

On the other hand, as shown in the figure, the second and third connection lines 3
If an accident _F12 occurs between a and 10a, the first
and second overcurrent detectors 13 and 14 both respond and output signals 13a and 14a, so that AND gate 18 outputs signal 18a. Therefore, AND gate 19 outputs signal 18
a, and the signal 17a is not output. In other words, even if the protective relay 7 reacts due to the unbalance between both inputs in such an external accident,
The protective relay device does not respond.

As is clear from FIG. 5, the conditions under which the protective relay device responds are as follows:
3 and 14 do not respond, or when either one of them responds, the protective relay 7 responds.

In addition, in the above embodiment, an overcurrent detector was used to determine faults on the secondary side line, but even if a detector that detects unbalance of voltage, current, or impedance between lines is used, the above-mentioned method also applies. The same effects as in the embodiment are achieved.

As described above, according to the present invention, an unbalanced state of the line on the secondary side of a phase shift transformer is detected, and only when these results satisfy a predetermined logical condition, protection is provided according to the operational output of the protective relay. As a result, the multiphase phase shift transformer can be protected with high reliability.

[Brief explanation of drawings]

FIG. 1 is a connection diagram of a conventional protective relay device, FIGS. 2 and 3 are diagrams showing the winding configuration of a phase shift transformer, and FIG. 4 is a diagram of a protective relay device according to an embodiment of the present invention. The connection diagram, FIG. 5, is a circuit diagram of the logic circuit shown in FIG. 1, 9...Phase shift transformer, 5a, 5b, 5c, 8
a, 8b, 8c, 11a, 11b, 11c, 12
a, 12b, 12c...current transformer, 7...protective relay,
13, 14... Overcurrent detector, 15, 16... Phase shifter, 17... Logic circuit. In addition, in the figures, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1. In a protective relay device for a phase-shifting transformer that has a plurality of phase-shifting windings on the secondary side and synthesizes multiphase currents using the phase-shifting windings, the primary side of the phase-shifting transformer is A plurality of Y-Δ-connected first current transformers that transform the current of each phase, and a plurality of Y-Δ-connected first current transformers that transform the current of one phase-shifting winding on the secondary side of the phase-shifting transformer at a predetermined ratio. Y of
−A second current transformer with Δ connection and two of the above phase shift transformers.
A plurality of Y-Δ connected third current transformers each transform the other phase shift winding current on the next side at a predetermined ratio, and the output current of the first current transformer is combined to connect each phase. a first connection line for deriving a current, and a second connection line for deriving a current between each phase on the secondary side by combining the output current of the second current transformer and the output current of the third current transformer. and a third connection line, first and second detectors that respond when each current flowing through the second and third connection lines exceeds a predetermined value, and the second and third connection lines. a first and a second phase shifter that phase shift each current flowing through the phase shifter by a predetermined value in the positive and negative directions, respectively; a current input that combines the outputs of the first and second phase shifters; A logical condition is established that prohibits the responsive output of the differential protective relay when both the first and second detectors output detection signals and the differential protective equipment that compares the current flowing through the connection wire, and the above-mentioned transfer A protection relay device equipped with a logic circuit that generates a signal to protect a phase transformer.