JPH0559650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a network protector used in high-voltage spot network power reception systems and the like.

(Prior Art) FIG. 5 shows the basic configuration of a high-voltage spot network power reception system. In the figure, consumer A and consumer B each receive power from the high-voltage distribution line 51 through three lines. The voltage of the high-voltage distribution line 51 is connected to the primary side of a step-down network transformer 53 connected △-△ via a primary disconnector 52 for each line, and the secondary side is connected to the protector fuse 5.
4 and a network bus 56 via a protector circuit breaker 55.

Further, a current transformer 57 is connected between the protector fuse 54 and the protector breaker 55, and the protector breaker 55 is connected from between its poles to the secondary side of the network transformer 53 and the network bus 56 side. The primary side of a differential voltage measuring transformer 58 that directly introduces the differential voltage between the
This differential voltage meter transformer 58 and the current transformer 5
A main relay 59 is connected between the secondary sides of 7. Further, on the secondary side of the network transformer 53, there is provided a standard for detecting the secondary side voltage of the network transformer 53 as an input circuit for obtaining a three-phase balanced voltage for the reference voltage in the differential voltage input characteristic of the network protector. The primary side of voltage meter transformer 60 is connected, and the secondary side thereof and the secondary side of differential voltage meter transformer 58 are connected to phase check relay 61 .
Note that loads are connected to the network busbars 56 via takeoff circuit breakers 62, respectively. Here, the network protector 63 includes a protector fuse 54, a protector circuit breaker 55, a main relay 59 as a network protector relay, a phase check relay 61, a current transformer 57, a differential voltage meter transformer 58, and a reference voltage meter transformer. It is composed of a container 60.

Next, as a specific example of this type of network protector, the voltage on the network bus 56 side is detected instead of the differential voltage instrument transformer 58, and the network protector detected by the reference voltage instrument transformer 60 is FIG. 6 shows a network protector 63' equipped with a potential transformer 58' for obtaining a voltage difference between the voltage on the secondary side of the transformer 53 and introducing the voltage to the network protector relay.

That is, in FIG. 6, the reference voltage voltage transformer 60 and the voltage transformer 58' connected to the network bus 56 are both connected to each other.
These secondary side phase voltages are introduced into the phase check relay 61 and the main relay 59 so that each relay operates. That is, the secondary side one phase and the neutral point of the reference voltage instrument transformer 60 are connected to the reference voltage coil 72 in the phase check relay 61,
One phase on the secondary side of each potential transformer 60, 58' is connected to the differential voltage coil 73 in the phase check relay 61, and each phase on the secondary side and the neutral point of the reference voltage potential transformer 60 are connected to the main It is connected to the reference voltage coil 75 in the relay 59, and the differential voltage coil 7 in the main relay 59 is connected between each phase on the secondary side of each potential transformer 60, 58'.
6 of the current transformer 57, respectively.
The next side is connected to the current coil 74 in the main relay 59, respectively. With this circuit configuration, the main relay 59 and the phase check relay 61 detect the differential voltage and phase angle between the secondary side of the network transformer 53 and the network bus 56 side, and detect the cutoff contact 64 and the make contact of the main relay 59. 65 and the contact 66 of the phase check relay 61 are operated, and the protector circuit breaker 5
5 is automatically opened and closed.

In this FIG. 6, the reference voltage meter transformer 60
Figure 7 shows an excerpt of only the secondary side burden. As is clear from this figure, the burden on the phase check relay 61 (reference voltage coil 72)
is connected only between phases u and n (n is the neutral point), and the burden on the main relay 59 (reference voltage coil 7
5) is connected between the un, vn, and wn phases, so that the loads on each phase are unbalanced.

On the other hand, since the network transformer 53 is Δ-connected and has no neutral point, the reference voltage instrument transformer 60
The neutral point becomes a virtual neutral point that depends on the magnitude of the load on the secondary side, and the voltages of each phase become unbalanced. As is well known, when applying a differential voltage to the protector circuit breaker 55 using a three-phase balanced voltage as a reference voltage, the secondary voltage Vt of the network transformer 53 and the network bus line are determined from the differential voltage application characteristics of the network protector. Since the protector circuit breaker 55 is automatically closed when the voltage Vn of 56 is in the relationship of Vt-Vn≧ΔV (differential voltage) and the phase angle of each voltage Vt, Vn is an appropriate value, as described above. If the magnitude and phase of each phase voltage on the secondary side of the reference voltage meter transformer 60 is uneven due to unbalanced load on the secondary side, the above condition will not be satisfied.

Therefore, conventionally, as shown in FIGS. 6 and 7, the v-
Correction impedance 67, 68 between n and wn phases
These correction impedances 67 and 68 were adjusted so that the voltages of each phase were balanced for all three phases.

In addition, considering the characteristic difference in the voltage fluctuation rate of each potential transformer 60, 58', the magnitude and phase of the secondary voltage of each potential transformer 60, 58' are adjusted when the protector circuit breaker 55 is closed. Correcting impedances 69 to 71 are connected between each phase of the secondary side of the potential transformer 58' and the neutral point so that the impedances are equal, and when the protector breaker 55 is disconnected, the above-mentioned closing conditions are adjusted. It was necessary to confirm that Vt−Vn≧ΔV was satisfied.

(Problems to be Solved by the Invention) However, according to this method, the work of adjusting the correction impedances 67 to 71 and checking the three-phase balanced voltage is extremely complicated, and a lot of time is required for adjustment, etc. Since a large number of circuits 71 to 71 are required, there are problems such as an increase in cost and a complicated circuit.

The present invention was proposed in order to solve the above problems, and its purpose is to provide a network without using correction impedance even if the secondary side load of the reference voltage voltage transformer is unbalanced. Balance the input reference voltage of the protector relay in three phases,
This eliminates the work of adjusting the correction impedance, reduces costs, and simplifies the circuit configuration, and is not affected by differences in characteristics between the reference voltage voltage transformer and the network bus side voltage transformer. It is an object of the present invention to provide a network protector capable of obtaining differential voltage application characteristics and reverse excitation (reverse power) interruption characteristics.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a protector connected between a network busbar and the secondary side of a network transformer whose primary side is connected to a distribution line. In a network protector equipped with a circuit breaker, a current transformer connected to the secondary side of the network transformer, and its own secondary side connected to the secondary side of the network transformer and △ connected. A reference voltage potential transformer outputs as a reference voltage a three-phase balanced voltage whose phase is 90 degrees ahead of the line voltage from the midpoint of each phase, and a network transformer outputs the voltage between the poles of the protector circuit breaker. A differential voltage instrument transformer detects the differential voltage between the secondary side of the network and the network bus side, the current output of the current transformer, the reference voltage and the differential voltage are respectively introduced and the protector circuit breaker is automatically activated. The network protector relay is characterized in that it is equipped with a network protector relay that turns on or off.

(Function) In the present invention, the secondary side of the reference voltage instrument transformer is
By connecting the lines and extracting the voltage with a phase lead of 90 degrees from the line voltage from the midpoint of each phase and introducing these as reference voltages to the network protector relay, the secondary side burden of the reference voltage instrument transformer can be reduced. A three-phase balanced voltage that is not affected by the voltage is obtained without using a correction impedance. In addition, since the interpole voltage (differential voltage) of the network busbar is directly detected by a voltage transformer separate from the reference voltage voltage transformer and introduced into the network protector relay, There is no need for a correction impedance to compensate for the characteristic difference, and good differential voltage application characteristics and reverse excitation cut-off characteristics can be obtained.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.
First, FIG. 1 shows a first embodiment of the present invention. In the figure, 53 is a network transformer connected △-△ in the same manner as described above, and its primary side is connected to a high-voltage distribution line (not shown). It is connected to the. The network protector 1 according to the present invention is connected to the secondary side of the network transformer 53. For convenience, the network transformer 53-2
The protector fuse connected to the next side is not shown.

In the network protector 1, 2 is a current transformer, and current coils 3, 4, 5 of a main relay 6, which together with a phase check relay 11 (described later) constitute a network protector relay, are connected to the secondary side of the current transformer. . In addition, 2 of the network transformer 53
Each phase on the next side is connected to each terminal U, V, and W on the primary side of the reference voltage measuring transformer 7 connected by Δ-Δ. Furthermore, the reference voltage instrument transformer 7-2
On the next side, as shown in Figure 2 in detail, the terminal v
-w, w-u, and uv are the midpoints n ₁ ,
n ₂ and n ₃ are provided respectively, and the u terminal and the midpoint n ₁
is connected to the reference voltage coil 8 of the main relay 6 and the reference voltage coil 12 of the phase check relay 11, the v terminal and the midpoint _n2 are connected to the reference voltage coil 9 of the main relay 6, and w
The terminal and midpoint n ₃ are connected to the reference voltage coil 10 of the main relay 6.

On the other hand, in FIG.
A protector circuit breaker 13 is connected between the secondary side of the circuit and a network bus (not shown), and a voltage difference between the secondary side and the network bus is directly detected between its poles. A wired differential voltage potential transformer 14 is connected. A differential voltage coil 15 of the phase check relay 11 is connected between one phase and the neutral point on the secondary side of the instrument transformer 14, and a main relay is connected between each phase on the secondary side and the neutral point. Six differential voltage coils 16 to 18 are connected, respectively. Although not shown, the network protector 1 is provided with a closing contact and a closing contact of the main relay 6 that closes or disconnects the protector circuit breaker 13, and a contact of the phase check relay 11.

Therefore, in such a configuration, the secondary side line voltages V・uv, V・vw,
V・wu, the voltage V・un ₁ between the u terminal and the midpoint n ₁ , the voltage V・vn ₂ between the v terminal and the midpoint n ₂ , and the voltage V・wn ₃ between the w terminal and the midpoint n ₃ are It is expressed by the voltage vector in Figure 3. Here, the voltages V・un ₁ , V・vn ₂ , and V・wn ₃ lead the line voltages V・vw, V・wu, and V・uv by 90° in electrical angle, and if the line voltage V・vw,V・wu,V・
If the magnitude of uv is 110V, the voltages V・un ₁ , V・vn ₂ ,
V・_wn3 is 110×(√3/2)≒95.3V.
Here, since the magnitude of each line voltage V・uv, V・vw, V・wu is always constant regardless of the unbalanced load on the secondary side, the potentials at midpoints n ₁ , n ₂ , n ₃ are also constant. and therefore,
The voltages V·un ₁ , V·vn ₂ , and V·wn ₃ are three-phase balanced voltages that are not affected by the unbalanced load on the secondary side. Therefore, these voltages are transmitted to the main relay 6 and the phase check relay 1.
1, a three-phase balanced voltage can be obtained as a reference voltage.

On the other hand, the voltage transformer 14 on the network bus side
Since the differential voltage is introduced directly into the main relay 6 and the phase check relay 11 from the voltage transformer 14
Even if there is a characteristic difference between the voltage difference and the reference voltage instrument transformer 7, the differential voltage itself is not affected, and the differential voltage input characteristics and reverse excitation (reverse power) cut-off characteristics of the network protector 1 are not affected in any way. There is no.

Next, FIG. 4 shows a second embodiment of the present invention. In this embodiment, the network transformer 53' is Δ-connected, and the reference voltage meter transformer 7'
are connected to -△, and these transformers 5
The connection side neutral points of 3' and 7' are both grounded. The rest of the configuration is exactly the same as the first embodiment, and in this network protector 1', a three-phase balanced voltage is applied as the reference voltage from the secondary side of the reference voltage potential transformer 7' regardless of the unbalanced load. A voltage can be introduced into each relay 6,11.

(Effects of the Invention) As described above, according to the present invention, a three-phase balanced voltage is generated from each phase of the △-connected secondary side of the reference voltage instrument transformer and is used as the reference voltage of the network protector relay. This eliminates the need for a large number of correction impedances as in the prior art, which simplifies the circuit configuration and reduces costs, and at the same time eliminates the need for complicated adjustment work to balance the three-phase voltages.

Furthermore, since the differential voltage is directly introduced from the voltage transformer on the network bus side, it is possible to obtain differential voltage turning-on characteristics and reverse excitation cut-off characteristics that are unaffected by characteristic differences with the reference voltage voltage transformer.

Furthermore, since the secondary side of the reference voltage instrument transformer is Δ-connected, there is an advantage that there is no variation in line voltage due to harmonic voltage from the grid.

[Brief explanation of drawings]

1 to 3 show a first embodiment of the present invention, in which FIG. 1 is a circuit configuration diagram, FIG. 2 is an explanatory diagram of the main parts in FIG. 1, and FIG. A voltage vector diagram, FIG. 4 is a circuit configuration diagram showing a second embodiment of the present invention, FIG. 5 is a basic configuration diagram of a spot network power receiving system, and FIG. 6 is a circuit configuration diagram showing a conventional network protector. Figure 7 is the 6th
It is an explanatory view of the secondary side load of the reference voltage meter transformer in the figure. 1, 1'...Network protector, 2...Current transformer, 6...Main relay, 7,7'...Reference voltage instrument transformer, 11...Phase check relay, 13...Protector breaker, 14...Differential voltage instrument transformer, 53,5
3'...Network transformer, 56...Network busbar.

Claims (1)

[Scope of Claims] 1. A network protector comprising a protector circuit breaker connected between a network busbar and the secondary side of a network transformer whose primary side is connected to a distribution line, comprising: The voltage between the current transformer connected to the secondary side of the transformer and the midpoint of each phase of the secondary side connected to the secondary side of the network transformer and connected △ is higher than the line voltage, respectively. A reference voltage instrument transformer outputs a three-phase balanced voltage with a phase lead of 90 degrees in electrical angle as a reference voltage, and a voltage between the poles of the protector circuit breaker is connected to the secondary side of the network transformer and the network bus side. a voltage difference measuring transformer for detecting a voltage difference between the current transformer and the current transformer;
A network protector comprising a network protector relay that automatically closes or disconnects the protector circuit breaker when the reference voltage and the differential voltage are respectively introduced.