JPH10313531A - Ratio differential relay - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce wiring work time between a secondary side of a current transformer provided on a primary side and a secondary side of a transformer and a differential relay and to prevent erroneous wiring. is there. A current transformer is provided on each of a primary side and a secondary side of a transformer provided in an electric power system, and a phase difference between a primary side current and a secondary side current flowing from the current transformer is a predetermined angle. In a differential relay that detects internal faults in the transformer on condition that the above conditions are met, the analog amount of current flowing from the primary and secondary current transformers during the rated load operation of the transformer is digital data. Analog-to-digital conversion means 6-2a, 6-2b for converting the current into digital data and measuring the phase difference between two currents flowing from the primary and secondary sides of the transformer by calculating the digital data converted by the conversion means If there is a phase difference between the two currents, a calculating means 6-4 is provided for automatically advancing or delaying one of the currents by the phase difference and correcting the current so that the phase difference coincides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ratio differential relay for detecting an accident such as a short circuit inside a transformer on a power system.

[0002]

2. Description of the Related Art A ratio differential relay is used as a relay for detecting and protecting an internal accident of a transformer on a power system. FIG. 4 shows an example of a power system using a conventional ratio differential relay, and FIG. 5 shows a detailed connection circuit diagram around the transformer shown in FIG.

[0003] As shown in FIG. 4, the primary side of a transformer 3 is connected to a three-phase AC power supply via a circuit breaker 2, and the secondary side of the transformer 3 is connected to a transmission line or a distribution line via a circuit breaker 7. In order to detect and protect the internal accident of the transformer 3 in the power system connected to the
₁ and I ₂ are detected by the current transformers 4 and 5, respectively, and the detected currents i ₁ and i ₂ are input to the ratio differential relay 6.

The ratio differential relay 6 determines that the transformer is normal when the phase of the current flowing on the primary side of the transformer 3 matches the phase of the current flowing on the secondary side, and the phase difference is greater than a predetermined angle. The transformer is protected by opening the circuit breakers 2 and 7 on the primary and secondary sides of the transformer 3 on the condition that the transformer has an internal accident.

Accordingly, the secondary connections of the current transformers 4 and 5 provided on the primary side and the secondary side thereof are determined according to the connection method of the transformer 3 and are connected by wiring. As shown in FIG. Detected currents i _1R , i _1S , i _1T corresponding to the three phases of the primary side of transformer 3 input to dynamic relay 6 and detected currents i corresponding to the three phases of the secondary side of transformer 3 The phases of _2R , i _2S and i _2T are matched.

That is, in the example shown in FIG. 5, since the primary side of the transformer 3 is Y-connected and the secondary side is Δ-connected, the secondary side of the current transformer 4 provided on the primary side of the transformer 3 is Δ-connected. By connecting the secondary side of the current transformer 5 provided on the secondary side of the transformer 3 to the Y connection, the transformer 3 input to the ratio differential relay 6
Detection currents i _1R , i _1S , i corresponding to each of the three phases on the primary side
_1T and the detection current i corresponding to each of the three phases on the secondary side of the transformer 3
_2R , i _2S , and i _2T have the same phase.

[0007]

As described above, since the internal connection of the transformer to be protected differs from one transformer to another in the related art, the primary and secondary sides of the transformer and the ratio differential relay are connected via the current transformer. Connection, the current transformer connection must be determined in consideration of the lead or lag of the current phase between the primary and secondary sides of the transformer caused by the internal connection of the transformer. Time was needed. In addition, since the connection pattern between the secondary side of the current transformer and the ratio operation relay is not unified, there is a possibility that a wiring error may occur.

The present invention has been made in view of the above circumstances, and the internal connection is different for each transformer by automatically adjusting the phases of two input currents having different phases to the same phase inside the relay. Even though the connection between the primary and secondary transformers can be determined regardless of the internal connection of the transformer, the ratio differential can reduce wiring work time and prevent incorrect wiring. It is intended to provide a relay.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is to constitute a ratio differential relay by the following means. According to the invention corresponding to claim 1, current transformers are respectively provided on a primary side and a secondary side of a transformer provided in a power system, and a primary side current and a secondary side current flowing from these current transformers are provided. In a ratio differential relay that detects an internal failure of the transformer on condition that the phase difference is equal to or greater than a predetermined angle, the transformer flows from the primary and secondary current transformers at the time of rated load operation of the transformer. Analog-to-digital conversion means for converting an analog amount of current into digital data; and digital data converted by the analog-to-digital conversion means to calculate two currents flowing from the primary and secondary sides of the transformer. Calculating means for measuring a phase difference and automatically advancing or delaying one of the currents by the phase difference if the two currents have a phase difference so as to make the phase difference coincide with each other; Of is the connection between the primary side and the secondary side of the current transformer those to be determined without regard to the internal wiring of the transformer.

[0010] Therefore, in the ratio differential relay having the above configuration, once the rated load operation is performed to automatically measure the phase of the current from the primary side and the secondary side of the transformer, and
By intentionally advancing or delaying one current by the phase difference in order to eliminate the phase difference between the two currents, it becomes possible to make the phases of two input currents having the same period but different phases in-phase in the relay. , The transformer and its primary and secondary sides can be connected regardless of the internal connection of the transformer.

According to a second aspect of the present invention, in the ratio differential relay according to the first aspect of the present invention, when the arithmetic means determines that there is a phase difference between the two currents, the secondary side of the current transformer. Means for automatically performing a trip lock on the assumption that a connection error has occurred, and displaying a warning to that effect.

Therefore, in the ratio differential relay having the above configuration, in addition to the operation and effect of the invention according to the first aspect, when there is a phase difference between the two currents, the trip lock is automatically performed. Since it is performed, the transformer protection operation due to erroneous detection can be eliminated.

According to a third aspect of the present invention, in the ratio differential relay according to the first aspect of the present invention, when the phase difference between the two currents is not corrected by the arithmetic means, a short circuit in the transformer is provided. Short-circuit detecting means for constantly monitoring the accident and outputting a trip command for disconnecting the transformer from the power system when the accident occurs when the voltage is applied to the transformer.

Therefore, in the ratio differential relay having the above configuration, in addition to the operation and effect of the invention corresponding to the first aspect, the phase difference between the two currents can be corrected by initialization of the arithmetic means. Otherwise, the transformer can be automatically protected even if a short circuit occurs in the transformer when the voltage is applied to the transformer.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an actual connection circuit diagram showing the vicinity of the transformer in detail, and the same parts as those in FIG.

In FIG. 1, an internal connection is a Yd1 connection, that is, a primary side is a Y connection, a secondary side is a protection target transformer having a Δ connection, and currents I ₁ and I ₂ flowing through a primary side and a secondary side of the transformer 3 are shown. Compared with the above, the current I ₂ on the transformer secondary side is delayed by 30 ° from the current I ₁ on the transformer primary side, although the periods are equal. Current transformers 4 and 5 are provided on the primary side and the secondary side of such a transformer 3, respectively. The secondary sides of these current transformers 4 and 5 are Y-connected to each other, and
Detection currents i _1R , i _1S , i corresponding to each of the three phases on the primary side
_1T and the detection current i corresponding to each of the three phases on the secondary side of the transformer 3
_2R , i _2S , and i _2T are input to the ratio differential relay 6, respectively.

In this case, the current transformers 4, 5 provided on the primary side and the secondary side of the transformer 3 are different from those in FIG. , I ₁ and i
₁ , no phase shift occurs between I ₂ and i ₂ . Therefore, the secondary currents i _1R , i _1S , i _1T of the current transformer 4 and the secondary currents i _2R , i _2S , i _2T of the current transformer 5 are 30 ° similarly to the relationship between I ₁ and I ₂ .
Has occurred.

Next, the internal configuration of such a transformer 3 and the ratio differential relay 6 connected to the secondary side of the current transformers 4 and 5 provided on the primary side and the secondary side thereof will be described with reference to FIG. explain.
In FIG. 2, detection currents i _1R , corresponding to each of the three phases of the primary and secondary sides of the transformer 3 input from the current transformers 4 and 5,
i _1S , i _1T and i _2R , i _2S , i _2T are converted into analog / digital conversion means 6-2a, 6-2 via input conversion means 6-1.
b, and are subjected to digital conversion processing and guided to the data bus 6-10.

This data is stored in the storage means 6-8, and at the same time, a zero cross point is detected for each phase by the calculating means 6-4 using the digitized current displacement of each phase. The phases of in-phase currents from the primary side and the secondary side of the transformer are compared for each of the R phase, the S phase, and the T phase, and the phase shift angle is measured.

Further, the angles obtained by the calculating means 6-4 are compared, and if the phase shift angles are the same in all three phases, the angles are compared with the input currents from the primary side and the secondary side of the transformer. The phase difference is regarded as a phase difference, and one current is automatically advanced or delayed by the phase difference so as to eliminate two currents, so that two input currents having the same period but different phases have the same phase. Then, the value of the phase shift angle obtained by the calculation means 6-4 is stored in the storage means 6-8.

On the other hand, if the phase shift angles do not match in all three phases, it is regarded as a connection error between the secondary side of the current transformer and the ratio differential relay, and trip lock is automatically performed. At the same time, a warning is output to the outside from the interface 6-6.

The initialization means 6-3 can initialize all the calculated values, but immediately after the initialization, the phase shift angles of the input currents from the primary side and the secondary side of the transformer are immediately after the initialization. Since no setting has been made, it is not possible to detect a short-circuit accident in the transformer immediately after applying a voltage to the transformer.

Accordingly, in order to enable protection of the transformer immediately after the excitation, the short-circuit detection means 6-7 in the transformer always monitors the short-circuit fault in the transformer.
At -5, a trip command is automatically output to the circuit breaker.

Further, the interface 6-6 can output a phase shift angle set in response to a request, a change in phase of each current with time, and the like to the outside. Can display those data.

Next, the phase matching operation of the ratio differential relay 6 configured as described above will be described with reference to the flowchart shown in FIG. First, in step S1, it is determined whether the setting of the deviation phase angle and the phase matching of the ratio differential relay have already been executed or whether it is the initial setting, and if it has been executed, the phase matching operation flow is terminated as it is. .
If the setting is the initial setting, the setting is started by operating the transformer once with the rated load in step S2.

Next, it is determined in step S3 whether a short circuit has occurred inside the transformer. If a short circuit has occurred, a trip process is immediately executed in step S4, and a circuit breaker trip command is output in step S5. .

If it is determined in step S3 that the current is normal, the primary current i ₁ and the secondary current i ₁ are used in step S6 by using the current flowing from the primary and secondary sides of the transformer into the differential relay. The phase difference of the current i ₂ is set to 3 by step S7.
The respective phase components are calculated and compared in step S8.

Then, in step S8, it is determined whether or not all three phase differences match, and if they do not match, trip lock is performed in step S9 and an alarm is output in step S10.

[0029] If the phase difference between the 3-phase step S8 is all consistent, and i ₁ and the phase difference in step S11 i
₂ and stored by setting a phase shift angle, step S1
At 2, the phase of i ₁ and the phase of i ₂ are matched by advancing or delaying one of the current phases by the phase shift angle.

Thus, the phase matching of the input currents i ₁ and i ₂ is completed. As described above, according to the above-described embodiment, the phase delay or advance of the current phase between the primary side and the secondary side of the transformer caused by the internal connection of the transformer, which has been conventionally performed, is considered. It is no longer necessary to wire or connect the secondary side of the current transformer so as to cancel out, so it is possible to determine the connection between the primary and secondary current transformers regardless of the internal connection of the transformer Becomes

Therefore, the design time and the wiring work time can be reduced,
Incorrect wiring can be prevented. In addition, since all transformers can be used with the same connection, there is no need to change the primary and secondary sides of the transformer when updating the transformer.

Further, when there is a phase difference between the currents input from the current transformers provided on the primary side and the secondary side of the transformer, the trip lock is automatically performed. Can be eliminated.

Further, when the arithmetic means does not correct the phase difference of the currents corresponding to each of the three phases inputted from the current transformers on the primary and secondary sides of the transformer, the short circuit in the transformer is prevented. The accident is constantly monitored, and if an accident occurs when voltage is applied to the transformer, a trip command is output to the circuit breaker by the short-circuit detection means.Therefore, when a voltage is applied to the transformer, a short-circuit accident occurs in the transformer. Even can automatically protect the transformer. The present invention is not limited to the embodiment described above and shown in the drawings, but can be variously modified and implemented without changing the gist of the invention.

[0034]

As described above, according to the present invention, even if the internal connection differs for each transformer, the connection between the primary and secondary current transformers is determined regardless of the internal connection of the transformer. Therefore, it is possible to provide a ratio differential relay capable of reducing wiring work time and preventing erroneous wiring.

[Brief description of the drawings]

FIG. 1 is a connection circuit diagram showing details around a transformer of a power system to which a ratio differential relay according to the present invention is applied.

FIG. 2 is a block diagram showing an embodiment of a ratio differential relay according to the present invention.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is a circuit configuration diagram showing a power system using a conventional ratio differential relay.

FIG. 5 is a connection circuit diagram showing details around a transformer in a power system using a conventional ratio differential relay.

[Explanation of symbols]

 3 Transformer 4, 5 Current transformer 6 Ratio differential relay 6-1 Input conversion means 6-2a, 6-2b Analog-digital conversion means 6-3 Initialization means 6-4 Computing means 6-5 Trip output means 6-6 Interface 6-7 Short circuit detecting means in transformer 6-8 Storage means 6-9 Display LED 6-10 …… Data bus

Claims (3)

[Claims] A current transformer is provided on each of a primary side and a secondary side of a transformer provided in an electric power system, and a phase difference between a primary side current and a secondary side current flowing from these current transformers is predetermined. A ratio differential relay that detects an internal failure of the transformer on condition that the angle is equal to or greater than an angle, wherein the analog amount of current flowing from the primary side and secondary side current transformers during rated load operation of the transformer; Means for converting digital data into digital data, and measuring the phase difference between two currents flowing from the primary side and the secondary side of the transformer by calculating the digital data converted by the analog / digital converting means. And calculating means for automatically advancing or delaying one of the two currents by a phase difference if the two currents have a phase difference so as to correct the phase difference so that the two currents coincide with each other. Ratio differential relay, wherein the connection between the secondary side of the current transformer it has to be determined without regard to the internal wiring of the transformer. 2. The ratio differential relay according to claim 1, wherein if the arithmetic means determines that there is a phase difference between the two currents, the operation is regarded as a connection error with the secondary side of the current transformer and the automatic operation is performed. A ratio differential relay characterized in that means for automatically trip-locking and displaying an alarm to that effect is provided. 3. The ratio differential relay according to claim 1, wherein when a correction for a phase difference between the two currents is not performed by the calculating means, a short circuit fault in the transformer is constantly monitored, and A ratio differential relay comprising short-circuit detecting means for outputting a trip command for disconnecting the transformer from an electric power system when an accident occurs at the time of applying a voltage.