JPH0231879Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention is a transformer protection relay that can electrically detect internal faults in a transformer, even if they are minute faults (such as one-turn short circuit), using a ratio differential relay. Regarding equipment.

[Conventional technology]

In recent years, transformer protection devices have been required to have higher reliability and higher performance as transformers have become larger in capacity and higher in voltage. Adoption of high-speed static relay,
Automatic monitoring devices are being adopted.

In order to increase the capacity of a transformer, the winding structure of a transformer is often increased by adding a main leg of the iron core and winding the windings around it and connecting it in parallel.

For example, in the case of a 500kV single-phase transformer, the capacity is 500/
In the case of 3MVA, as shown in Figure 1, a winding is wound around the main leg A1 of the three-leg iron core consisting of one main leg A1 and two return legs B1 and B2, and the magnetic flux φ is is formed, but the capacity is doubled,
In the case of 1000/3MVA, 2 as shown in Figure 2.
A four-leg iron core consisting of two main legs A1, A2 and two return legs B1, B2 is used, and there are two main legs/phase. The windings are also wound for each main leg, and the windings are parallel. connected to. Similarly, the capacity is tripled to 1500/
In the case of 3MVA, as shown in Fig. 3, a five-leg iron core consisting of three main legs A1, A2, A3 and two return legs B1, B2 is used, and the number of main legs is three per phase. The windings are wound and the windings are connected in three parallels. The center of the three main legs is used as the return leg. Capacity quadruples to 2000/3MVA
In this case, as shown in FIG. 4, two four-legged iron cores shown in FIG. 2 are used. Note that the design of the core main leg main winding is the same for all of the capacities mentioned above, and the physique of the winding is the same, so the impedance voltage based on the capacity is the same.

[Problem that the invention attempts to solve]

However, the problem with this type of stacked block structure is that in conventional protection devices, the more parallel windings there are, the larger the capacity, the more the monopod windings are compared under the same accident conditions. As the input of the ratio differential relay becomes smaller (if the capacity increases by n times, the input becomes 1/n), there is a possibility that an accident cannot be detected. Such a conventional protection device will be explained based on FIGS. 5 and 6. Figure 5 is
It shows the structure diagram of a 1000/3MVA transformer.
FIG. 6 shows the protection circuit diagram. In the conventional protection device, one current transformer CT1, CT2 is installed for each phase as shown in Fig. 5, and the current transformers CT1, CT2 are used to change the ratio as shown in Fig. 6. Differential relay D1 is connected. However, according to such a protection device,
In the structure of the transformer as shown in Fig. 3,
If a fault occurs in one of the windings wound around each main leg and a fault current If flows, the current transformation ratio is α, 2α, and 3α, respectively, in proportion to the capacity, so the ratio differential relay The inputs to the difference circuit are respectively If×
1/α, If×1/2α, If×1/3α, and the larger the capacity, the smaller the input. The minimum operating value of a ratio differential relay is generally about 30% of the rated current.
If the input of the ratio differential relay described above is less than the minimum operating value, it will not be able to operate. In terms of disaster prevention measures for transformers, it is necessary to detect even the slightest accident and promptly trip the disconnector before the accident escalates. Although it depends on the transformer specifications, structure, system conditions, etc., in the case of a small accident, the fault current when one turn is shorted is generally about 30 to 100% of the rated current.
The fault current in the event of a 1-tap short circuit is approximately 50 to 50% of the rated current.
200%, and when the capacity is increased, the input of a ratio differential relay becomes 1/n when the capacity increases by n times, so a ratio differential relay can detect not only a one-turn short circuit accident but also a one-tap short circuit accident. It becomes difficult.

[Means for solving problems]

In view of the above, the present invention has multiple main landing gear cores as a transformer protection relay device that can detect even a one-turn short circuit accident with a ratio differential relay, and the windings wound around each main landing gear are connected in parallel. In connected transformers, a current transformer is installed in each winding, and current transformers placed in windings of different orders of the transformer are combined to form a ratio differential protection relay circuit. be.

[Effect]

In the present invention, a current transformer is arranged for each winding connected in parallel to each main leg of the above configuration, so that the primary current and secondary current at the terminal side of the windings of different orders of the transformers connected in parallel are Since the current transformation ratio is the same as that of the winding configuration shown in Fig. 1 with a single winding around one leg core, the fault current due to a winding fault in one leg of the core of the windings connected in parallel is: This means that detection can be performed with twice the sensitivity compared to the conventional configuration.

〔Example〕

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

Figure 7 shows a configuration diagram of a 1000/3MVA transformer. Similar to the transformer shown in Figure 5, a four-leg iron core is used, but compared to Figure 5, each winding is The difference is that flow vessels CT1 to CT4 are attached. In this way, current transformer CT1 or
FIG. 8 shows an embodiment of the protection circuit diagram according to the present invention when CT4 is attached to each winding.

Figure 8 shows an example in which a ratio differential protective relay circuit is constructed by combining current transformers installed in each winding for each main leg (A1 leg, A2 leg each). Since a current transformer is installed for each winding, the current transformation ratio (primary current/secondary current) can be kept constant even if the capacity increases, and the input to the ratio differential relay does not change. Therefore, when the capacity increases by n times, it is equivalent to increasing the sensitivity of the ratio differential relay by n times compared to the conventional protection device in which the current transformation ratio is 1/n, which means that the current ratio is 1/n. It is possible to detect minute accidents such as turns and one-tap short circuits.

Figure 9 shows an example in which a ratio differential protection relay circuit is constructed by combining current transformers installed for each winding for different main legs, and shows the faulty leg (winding) and the healthy leg (winding). By comparing the legs (windings) and applying the fact that in the event of an accident, the fault current flows only to the accident leg,
The unbalance between the two legs creates an input to the ratio differential relay and causes it to trip.
In this case, even if the capacity is large, the current transformation ratio can be kept constant, and like the ratio differential protection relay circuit shown in Figure 8, the sensitivity has been improved by n times compared to the conventional one. become equivalent. Furthermore, in the configuration shown in FIG. 9, if an internal accident occurs, both ratio differential relays D1 and D2 operate.
By using the output contacts of the ratio differential relays D1 and D2 to make the contacts redundant and to create two lines, it is possible to prevent malfunctions and malfunctions and improve reliability.

In the above embodiments, only a transformer provided with a primary winding and a secondary winding is shown, but the same applies to a transformer provided with a primary winding, a secondary winding, and a tertiary winding. FIG. 10 shows a configuration diagram of a transformer provided with primary, secondary, and tertiary windings. Similar to FIG. 7, a four-leg iron core is used, and each winding has current transformers CT1 to CT6.
is installed. Note that the winding indicated by a broken line in the figure is the tertiary winding. In this way, a tertiary winding is provided and each winding is connected to a current transformer CT1 or CT1.
An embodiment of the protection circuit diagram according to the present invention when the CT6 is installed is shown in FIGS. 11 and 12.

FIG. 11 shows an embodiment in which a ratio differential protection relay circuit is constructed by combining current transformers attached to each winding for each main leg (A1 leg, A2 leg). Figure 12 also shows the current transformer attached to the primary winding of the current transformers attached to each winding, and the current transformer attached to the primary winding, and the two Next, an embodiment will be shown in which a ratio differential protection relay circuit is constructed by combining the tertiary winding with a current transformer attached. Furthermore, as shown in Figure 12, instead of the current transformer attached to the tertiary winding wound on the same main landing gear as the secondary winding, there is a current transformer attached to the tertiary winding wound on the same main landing gear as the primary winding. It is also possible to use a current transformer attached to the next winding. It goes without saying that when applied to a transformer having a tertiary winding in this manner, the same effect as that of the n-fold improvement in sensitivity of a ratio differential relay can be obtained.

Further, when the capacity is increased and a plurality of cores are used as shown in FIG. 4, a current transformer can be installed for each core to form a ratio differential relay circuit. However, in this case, the sensitivity is lower than when a current transformer is installed for each winding.

In the above description of the embodiment, only the case of a four-legged core has been described, but it can also be applied to a five-legged core or a core with more legs by selecting a predetermined current transformer. .

[Effect of idea]

In this way, according to the present invention, a current transformer is installed for each winding, and among the current transformers, current transformers arranged in windings of different orders of the transformer are combined. Even minute accidents such as taps or single-turn short circuits can be detected. Also, Figures 8 to 9, Figures 11 and 12
The protection device according to the present invention as shown in the figure is used in combination with the protection device shown in Fig. 6, the former being used for detecting minute accidents in the transformer (split protection), and the latter being used for all-in-one protection of the entire transformer. As a result, system reliability can be further improved. Furthermore, by adding a current transformer installed for each winding, it is possible to create a protection device that combines the protection devices shown in Figures 8 to 9, 11, and 12, improving the reliability of protection. can be done.

[Brief explanation of the drawing]

Figures 1, 2, 3, and 4 are configuration diagrams of the core of a transformer, Figure 5 is a configuration diagram of a transformer with a conventional protection device, Figure 6 is its protection circuit diagram, and Figure 7 , FIG. 10 is a block diagram of a transformer using the protection device of the present invention, and FIGS. 8 to 9, 11, and 12 are diagrams of its protection circuit. A1, A2, A3...Main landing gear core, B1, B2...
...Return leg iron core, CT1 to CT6...Current transformer, D
1, D2, D3...Ratio differential relay.

Claims (1)

[Claims for Utility Model Registration] 1. In a transformer having a plurality of main landing gear cores and having windings wound around each main landing gear core connected in parallel,
A transformer protection relay characterized in that a current transformer is installed for each winding, and a ratio differential protection relay circuit is constructed by combining current transformers placed in windings of different orders of the transformer. Electrical equipment. 2. A transformer protection relay device according to claim 1 of the utility model registration, characterized in that current transformers installed on windings wound around the same main landing gear core are combined. Relay device. 3. A transformer protective relay device according to claim 1 of the utility model registration claim, characterized in that current transformers installed in windings wound around different main landing gear cores are combined. Electrical equipment. 4. In the transformer protective relay device set forth in claim 3 of the utility model registration, the current transformer installed in the primary winding and secondary winding wound on different main landing gear cores is combined. Characteristic transformer protection relay device. 5. In the transformer protection relay device set forth in claim 3 of the utility model registration claim, a current transformer installed in a primary winding wound around one main landing gear core and a current transformer installed in a primary winding wound around one main landing gear core, and a current transformer installed in a primary winding wound around one main landing gear core, A transformer protection relay device characterized by a combination of a current transformer installed in a secondary winding and a tertiary winding. 6. In the transformer protective relay device set forth in claim 3 of the utility model registration, a current transformer installed in a primary winding and a tertiary winding wound around one main landing gear core and a current transformer and other main A transformer protection relay device characterized by combining a current transformer installed in a secondary winding wound around a leg iron core.