JP2002191121A - Ratio differential relay provided with higher harmonic locking function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a ratio differential relay with a higher harmonic locking function which is used for detecting an internal failure of a transformer and protecting the transformer, enables simple and inexpensive forming of a locking command output circuit, and has a noise resisting property, too. SOLUTION: This ratio differential relay has a vector adding circuit 8 for performing vector addition of a current I1 flowing in the primary side of a transformer 2 being an object of protection and a current I2 flowing in its secondary side, a CPU 10 which takes out the secondary higher harmonic of the current after the vector addition, and locks tripping of a circuit-breaker when the ratio of content of the secondary higher harmonic with respect to the fundamental component of the current after the vector addition exceeds a threshold value, a relay LX, and a relay RX. The CPU 10, the relay LX, and the relay RX lock tripping of the circuit-breaker, when the ratio of the content of the secondary higher harmonic of the current after adding the vector with respect to the fundamental wave component exceeds a threshold value, in at least one phase. The CPU 10 realizes the locking of tripping of the circuit- breaker by software.

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 with a harmonic lock function, which is used to protect a transformer by detecting an internal failure of the transformer.

[0002]

2. Description of the Related Art A ratio differential relay is a relay that operates when a fault occurs in a transformer because a primary-side and secondary-side differential current is generated. However,
If the power is turned on when no load is applied, an exciting rush current flows to the primary side of the transformer, and this causes a problem that the ratio differential relay responds and performs unnecessary operation.

In view of the above, attention has been paid to the fact that the inrush current has a large amount of second harmonic components. When the second harmonic component is large, a technique for locking the operation of the auxiliary relay even when the exciting inrush current flows has been proposed. (Japanese Patent Publication No. 6-67115).

[0004]

However, in the configuration of the prior art, the lock command output circuit is composed of a hardware electronic circuit including the relay SU, and the configuration is complicated and expensive. In addition, since a low-voltage power supply (5 V) is used in the electronic circuit, there is a problem that it is weak to noise. Accordingly, an object of the present invention is to realize a ratio differential relay with a harmonic lock function that can simply and inexpensively configure a lock command output circuit and has noise resistance.

[0005]

SUMMARY OF THE INVENTION A ratio differential relay with a harmonic lock function according to the present invention comprises a vector of a current I1 flowing through a primary side of a transformer to be protected and a current I2 flowing through a secondary side. Vector addition means for performing addition, means for obtaining a second harmonic of the current after the vector addition, and when the content of the second harmonic with respect to the fundamental component of the current after the vector addition exceeds a threshold value. And locking means for locking the trip of the circuit breaker, wherein the locking means is configured such that in at least one phase, the content of the second harmonic of the current after the vector addition with respect to the fundamental wave component exceeds a threshold value. The lock means comprises a combination of a logic circuit, a relay, and an arithmetic processing circuit. In this arithmetic processing circuit, the tripping of the circuit breaker is performed. It realizes the lock by software (claim 1).

According to the above configuration, the locking means includes:
It is composed of a combination of a logic circuit, a relay, and an arithmetic processing circuit, and locks the trip of the circuit breaker by software. Therefore, there is no need to insert a relay in series into the trip circuit of the circuit breaker as in the past,
The configuration of the trip circuit does not become complicated. Further, the relay constituting the locking means has a DC11.
A driving power supply of 0 V can be used (claim 2).

Therefore, it is possible to form a lock circuit which is more resistant to noise than conventional lock means which uses a 5V power supply in an electronic circuit.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall block configuration diagram of a ratio differential relay 1 with a harmonic lock function. Current transformers CT on the primary and secondary sides of the three-phase transformer 2
And the detection signal is input to the ratio differential relay 1 with the harmonic lock function. Note that FIG. 1 shows only one phase, but the other two phases have the same configuration.

In the configuration of the ratio differential relay 1 with the harmonic lock function, the power supply unit 3 is a DC power supply (DC 110 V) for operating the auxiliary relay RX and the like. The output of the current transformer CT is input to the auxiliary current transformer 4, where it is converted into a voltage value. The converted voltage signal is input to a ratio matching circuit 5 for adjusting the voltage according to the winding ratio between the primary and secondary windings of the transformer 2. The voltage signal that has been matched by the ratio matching circuit 5 is split into two, one of which enters the rectifier circuit 6 and takes an absolute value (such as an effective value). The absolute value is added by the absolute value adding circuit 7 and input to the A / D converter 9.

Another one enters a vector addition circuit 8,
The vector sum I1 + (-I2) is obtained and input to the A / D converter 9. In the arithmetic processing unit 10, the current value | I1 | + | I2 |
-I2 ratio / (| I1 | + | I2 |) (1) is compared with a threshold value. If the threshold value is exceeded, it is determined that a transformer internal failure has occurred and the auxiliary relay TX is determined. A drive signal is issued to When driven, the auxiliary relay TX turns on a contact to energize the trip coil and cut off the system.

FIG. 2 shows the differential relays 1a-1a.
CPUs 10a to 10c and auxiliary relays TXa to TX
c is a diagram for explaining the connection state of the trip coil TC, and the subscripts a to c indicate that they correspond to each phase. Since the contacts of the three auxiliary relays TXa to TXc are connected in parallel with each other, when any one of the contacts of the auxiliary relay TX is turned on, the trip coil TC is energized. Therefore, if the ratio exceeds the threshold value in one phase, the power of all phases is shut off.

Returning to FIG. 1, the arithmetic processing unit 10 has software for calculating a fundamental wave and a second harmonic.
The second harmonic (I1-I2) of the vector added currents I1-I2
Calculate the ratio (I1-I2) ₂ / (I1-I2) ₁ (2) between I2) ₂ and the fundamental wave (I1-I2) _1, and calculate the threshold (for example, set to 0.13). Compare. If the threshold value is exceeded, the auxiliary relay LX is operated, and the lock auxiliary relay RX is energized. As a result, the contact of the locking auxiliary relay RX is closed, and the signal s for locking the auxiliary relay TX is input to the arithmetic processing unit 10.

The lock auxiliary relay RX is provided with a power supply unit 3.
Is driven at a high voltage by DC110V generated at DC5.
Noise resistance is improved as compared with the conventional auxiliary relay driven by V. FIG. 3 shows the CPUs 10a to 10c of the ratio differential relays 1a to 1c with a harmonic lock function, the auxiliary relays LXa to LXc, and the auxiliary relays RXa to R for locking.
It is a figure for explaining the connection state of Xc etc. Subscript a
To c show each phase.

Locking auxiliary relays RXa to RX for three phases
When the auxiliary relay LX for one phase is operated and the contact is closed, the auxiliary relay for locking RX is energized for all three phases and the three CPs are connected.
For U10a to 10c, auxiliary relays TXa to TXc
Is input. Therefore, 3
The operation of the two auxiliary relays TXa to TXc is locked.
The time required to lock the operation of the auxiliary relays TXa to TXc is within 100 msec, while the time required to turn on the contacts of the auxiliary relays TXa to TXc and energize the trip coil is about 150 msec. because there is,
Before the trip coil is energized, the auxiliary relay TXa ~
TXc operation can be stopped.

Therefore, when an exciting rush current flows,
Unnecessary operation of the ratio differential relay 1 with the harmonic lock function can be reliably prevented. Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above embodiments, and various modifications can be made within the scope of the present invention.

[Brief description of the drawings]

FIG. 1 is an overall block configuration diagram of a ratio differential relay 1 with a harmonic lock function.

FIG. 2 shows a CP of a ratio differential relay 1 with a harmonic lock function.
FIG. 7 is a diagram for explaining a connection state of a U, an auxiliary relay TX, and a trip coil TC.

FIG. 3 shows a CP of a ratio differential relay 1 with a harmonic lock function.
FIG. 9 is a diagram for explaining a connection state of a U, an auxiliary relay LX, and a lock auxiliary relay RX.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ratio differential relay with harmonic lock function 2 three-phase transformer 3 power supply unit 4 auxiliary current transformer 5 ratio matching circuit 6 rectifier circuit 7 absolute value addition circuit 8 vector addition circuit 9 A / D converter 10 arithmetic processing unit TX Auxiliary relay LX Auxiliary relay RX Auxiliary relay for lock

Claims (2)

[Claims] 1. Vector addition means for performing vector addition of a current flowing on a primary side of a transformer to be protected and a current flowing on a secondary side, a means for obtaining a second harmonic of a current after vector addition, When the content of harmonics to the fundamental component of the current after the vector addition exceeds a threshold value, the device has lock means for locking the trip of the circuit breaker, wherein the lock means includes at least one phase. When the content of the second harmonic of the current after the vector addition with respect to the fundamental component exceeds a threshold, the tripping of the circuit breaker is locked, and the locking means includes a logic circuit, a relay, With a harmonic lock function, characterized in that the lock of the trip of the breaker is realized by software in this arithmetic processing circuit. Rate differential relay. 2. A relay constituting the locking means has a resistance of about D
The ratio differential relay with a harmonic lock function according to claim 2, wherein a driving power supply of C110V is used.