JPH0515295U - Ratio differential relay - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a ratio differential relay with a small inoperative region over the entire tap of the transformer. [Structure] The primary input current circuit and the secondary input current circuit are provided with a voltage correction circuit in one or both of them, and the apparent power passing through the transformer is used as a reference by correcting the current change due to the tap position change. To obtain the ratio differential relay.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to a ratio differential relay that protects a transformer.

[0002]

[Prior Art]

 Figure 5 is a single wire connection diagram showing how to use a conventional relay. In the figure, 1 is a transformer to be protected, 2 is a primary side current transformer, 3 is a secondary side current transformer, and 4 is a ratio. It is a differential relay. Fig. 6 is an internal connection diagram showing the operating principle of, for example, the Mitsubishi TUB-2 type ratio differential relay. In the figure, 10 is an input current transformer with a tap on the primary side, and 11 is an input with a tap on the secondary side. Current transformer, 12 suppression circuit, 13 differential circuit, 14 comparison circuit, 15 differential output relay, 16 second harmonic detection circuit, 17 output relay, 15a relay 15 contact, 17a Is a contact of the relay 17, 18 is a self-holding relay, and 18a is a contact of the relay 18.

Next, the operation will be described. It is added as a current input to the input current transformers 10 and 11 from the current transformers 2 and 3 provided on the primary and secondary sides of the transformer 1. The input current transformers 10 and 11 are sent to the differential circuit 13 and the suppression circuit 12 after correcting the transformation ratio of the transformer 1 to be protected and the current transformation ratios of the primary and secondary side current transformers 2 and 3. The differential circuit 13 detects the range of the differential current to be protected, and the suppression circuit 12 prevents malfunction due to the magnitude of the current. These two outputs are compared by the comparison detection circuit 14, and when the value to be protected is reached, the output relay 5 is operated. The second harmonic detection circuit 16 detects the second harmonic in the exciting inrush current when the transformer is turned on, activates the output relay 17, and cooperates with the output relay 15 to prevent malfunction of the differential protection relay. Play a role in prevention.

[0004]

[Problems to be solved by the device]

 Since the conventional ratio differential relay is configured as described above, when the tap of the transformer is changed, it is necessary to change the setting or increase the dead zone so that it does not operate within the changed range. However, there were problems such as forgetting to change the setting of the relay or lowering the sensitivity due to the expansion of the dead zone.

The present invention has been made in order to solve the above problems, and can reliably detect an internal failure irrespective of the relay tap position, and does not reduce the sensitivity due to the expansion of the dead zone. The purpose is to provide a relay.

[0006]

[Means for Solving the Problems]

 The ratio differential relay according to the present invention is such that the input current to the relay is corrected by the voltage detected from the primary side and the secondary side of the transformer.

[0007]

[Action]

 Since the input current correction circuit according to the present invention corrects by the voltage detected from the primary and secondary sides of the transformer, the transformer can be protected without expanding the dead zone regardless of the tap position of the transformer.

[0008]

【Example】

 Example 1. An embodiment of the present invention will be described below. In FIG. 1, 101 is a primary side transformer, 102 is a secondary side transformer, and is a voltage input source to the ratio differential relay 5. FIG. 2 shows the internal connection of the relay 5 showing one embodiment of the present invention, 121 is a primary side input current correction circuit, and 122 is a secondary side input current correction circuit.

Next, the operation will be described. The tapped input current transformers 10 and 11 are the transformers to be protected 1. The transformer ratio, the current transformer ratios of the current transformers 2 and 3 installed on the primary and secondary sides, and the secondary current transformer connection method. Correct the input current due to and select the tap position so that the difference in the input current to the relay circuit between the primary side and the secondary side is small. The primary input current correction circuit 121 and the secondary input current correction circuit 122 compare the reference voltage with the primary and secondary voltage inputs to correct the voltage fluctuations, and then output the suppression circuit 12 and the differential circuit 13. If the correction of 121 and 122 is (input voltage) (current correction circuit output) = ────── × (input current) (reference voltage), the input current to the relay will change even if the tap of the transformer changes. Is corrected so that the apparent power passing through the voltage transformer 1 becomes constant, so protection is possible without being affected by the tap position.

Example 2. In the above embodiment, the correction of the relay input current is provided for both the primary side input current and the secondary side input current. However, the same effect can be obtained by providing the primary side input current circuit only as shown in FIG. The circuit may be set according to the following equation. (Primary input voltage) (Secondary input voltage) (Correction circuit output) = ──────── × ──────── × (Input current) (Primary reference voltage) (Secondary reference Voltage)

Example 3. In the second embodiment, the primary side input current is corrected, but this also has the same effect in the secondary side input current correction method as shown in FIG.

Example 4. In addition, the above-mentioned Examples 1 to 3 have been described using the input current transformer with taps in the current input circuit of the relay, but without using this current transformer, the transformation ratio of the transformer is corrected by the input current by voltage. Obviously, it may be included in the correction circuit.

Further, although the case of the two-winding transformer has been described in the first to fourth embodiments, the same method can be applied to a transformer having three windings or more, and the same effect as that of the embodiment is obtained.

[0014]

[Effect of the device]

 As described above, according to the present invention, a voltage element is added to the ratio differential protection relay of the transformer and the apparent power passing through the transformer is compared, so that it is protected even in the tapped transformer under load. Protection is possible at all tap positions without expanding the range, which has the effect of ensuring protection.

[Brief description of drawings]

FIG. 1 is a single wire connection diagram according to a first embodiment of the present invention.

FIG. 2 is an internal connection diagram of the relay according to the first embodiment of the present invention.

FIG. 3 is an internal connection diagram of a relay according to a second embodiment of the present invention.

FIG. 4 is an internal connection diagram of a relay according to a third embodiment of the present invention.

FIG. 5 is a single wire connection diagram showing a method of using a conventional relay.

FIG. 6 is an internal wiring diagram of a conventional relay.

[Explanation of symbols]

 1 Transformer 2 Primary side current transformer 3 Secondary side current transformer 4 Ratio differential relay 5 Ratio differential relay with voltage correction circuit 121 Primary side input current correction circuit 122 Secondary side input current correction circuit

Claims (1)

[Scope of utility model registration request] 1. A ratio differential relay which detects and protects an internal failure of the transformer by operating when the ratio of the primary side current and the secondary side current of the transformer is out of a predetermined range. ,
A correction circuit that detects the primary side voltage and the secondary side voltage of the transformer and corrects at least one of the current values detected from the primary side and the secondary side of the transformer according to the ratio of these voltages. The ratio differential relay is characterized by the provision of.