JPH0130368B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a protective relay inspection method.

Generally, a protective relay takes in the voltage and current of the system to be protected as input via an instrument transformer, transforms this input appropriately with a built-in auxiliary transformer, performs protection calculations, and then provides static protection. In the relay, the output of the auxiliary transformer is passed through an input conversion circuit consisting of a rectifier to convert it into DC of an appropriate value for protection calculations.

Inspection of static protective relays involves applying a simulated input to the DC side of the input conversion circuit to check whether a protective output is possible. In this inspection method, only the circuits after the input conversion circuit are inspected for quality.
If the problem occurs in the input conversion circuit or auxiliary transformer, the problem cannot be detected.

Therefore, ideally when inspecting a protective relay, it is possible to inspect all the circuits from the input terminal to the final output terminal by applying an inspection AC input to the input terminal of the protective relay. To realize this inspection method, the method shown in FIG. 1 can be considered.

Figure 1 shows the case where it is applied to a ground fault directional relay. A sheath breaker 2 and a zero-phase current transformer 3 are interposed on the distribution line 1 to be protected among the multiple lines, and the zero-phase current transformer 3
Connect the transformer output terminals k and l of the transformer to the current input terminals C ₁ and C ₂ of the earth-fault directional relay 4, and connect the attached resistor 5 to the voltage input terminals P ₁ and P ₂ of the earth-fault directional relay 4 on one side. The transformed output of the grounded instrument transformer 6 is introduced, and the ground fault directional relay 4 calculates the magnitude of the zero-sequence voltage obtained from the transformer 6 and the ground fault current obtained from the current transformer 3, and determines the phase of both. and obtain the trip signal for disconnector 2. 7 is a current limiting resistor.

In such a ground fault direction relay, an inspection changeover switch 8 is provided to supply the voltage from an inspection power source instead of the voltage from the instrument transformer 6 to the voltage input terminals P ₁ and P ₂ . The voltage input terminals P ₁ and P ₂ of the earth-fault directional relay 4 are normally connected to the tertiary winding of the potential transformer 6, and during inspection, the changeover switch 8 is switched to the normally open side and the transformer is connected to the tertiary winding of the voltage transformer 6. Disconnect the tertiary winding No. 6. In addition, during inspection, connect current transformer 3 from the inspection power supply.
Current is also supplied to the test winding terminals k _t and _lt to give a simulated zero-sequence current to the current input terminals C ₁ and C ₂ of the relay 4.

In such an inspection method, the provision of the changeover switch 8 in the circuit of the relay 4 itself reduces the reliability of the protective relay. In particular, since the normally closed contact of the changeover switch 8 is a B contact, the reliability of the contact ability is very low, and there is a risk that an inspection circuit intended to improve the reliability of the relay may actually reduce the reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inspection method that allows an inspection input to be applied to an input terminal of a relay while maintaining connection with the relay without adversely affecting the instrument transformer.

FIG. 2 shows an embodiment of the present invention, which is applied to a ground fault direction relay. Inspection power transformer 9
are terminals GP ₁ , GP ₂ connected to the tertiary winding of the ground voltage instrument transformer 6 and terminals RP ₁ , RP ₂ connected to the voltage input terminals P ₁ , P ₂ of the ground fault directional relay 4. and terminals TP ₁ and TP ₂ connected to the voltage terminals of the power supply for inspection.
Equipped with. The power supply for inspection is inspection power switch 1.
A voltage regulator 11 adjusts the voltage of the AC power taken in through the transformer 9, and the voltage output of the voltage regulator 11 is used as a voltage input to terminals TP ₁ and TP ² of the transformer 9 via a voltmeter 12. The alternating current power that has passed through the power switch 10 is input as a current to the test winding terminals k _t and l _t of the current transformer 3 through a variable resistor 13 and an ammeter 14 connected in series.

The inspection power transformer 9 has the configuration shown in FIG. 3a. Iron core A is a three-legged iron core with an intermediate core A', and a closed magnetic circuit is constructed, and the inspection input winding C connected to inspection voltage input terminals TP ₁ and TP ₂ is connected to the intermediate core of iron core A.
A′, and the voltage input terminals P ₁ , P ₂ of relay 4
The voltage output winding D connected to the voltage output terminals RP ₁ and RP ₂ for applying voltage to is wound around one of the outer leg cores of the iron core A, and is connected to the output of the tertiary winding of the grounded instrument transformer 6. The zero-phase voltage input winding E, which has the input as
The winding E is wound around one core of core A'' with approximately the same number of turns on both sides of core A'' with intermediate core A'' as a boundary, and connected in series.

In this configuration, when the check voltage V ₁ is applied between the terminals TP ₁ and TP ₂ , the magnetic flux φ of the intermediate core A′ generated by the winding C is φ /2, and the voltage V ₃ induced in the winding E becomes zero as the magnetic velocities φ/2 become opposite directions and cancel each other out. On the other hand, the winding D has a magnetic flux φ/2
Accordingly, a voltage V ₂ can be generated between the terminals RP ₁ and RP ₂ . Next, terminals GP ₁ and GP ₂ are connected from the transformer 6.
When a voltage V ₃ is applied between the terminals TP ₁ and TP ₂ , as shown in FIG. ₁ does not occur and becomes 0. And terminal RP ₁
A voltage V ₂ can be generated between and RP ₂ due to the magnetic flux φ.

Therefore, in the configuration shown in FIG. 2, if the inspection power transformer 9 is of the configuration shown in FIG. 3,
To inspect the relay 4, close the switch 10, set the voltage regulator 11 to a predetermined inspection voltage, and apply the inspection voltage to the relay 4 by applying it between terminals TP ₁ and TP ₂ of the power transformer 9. Can be done. At this time, no voltage is generated between the terminals GP ₁ and GP ₂ of the transformer 9 as described above, and the tertiary winding of the ground voltage instrument transformer 6 is not affected in any way. Note that a variable resistor 13 can be adjusted between the test winding terminals k _t and _lt of the zero-phase current transformer 3 to supply a predetermined inspection current to the relay 4 .

Next, when a system ground fault occurs, the zero-sequence voltage from the transformer 6 is applied between the terminals GP ₁ and GP ₂ of the transformer 9, so that the zero-sequence voltage can be applied to the relay 4. Then, the terminals of transformer 9 for zero-sequence voltage
There is no voltage generated between TP ₁ and TP ₂ , and there is no effect on the inspection circuit or inspection power supply.

The above explanation shows the case where it is applied to the voltage input circuit of a ground fault directional relay, but it can be applied to the voltage input circuit from a voltage transformer not limited to other protective relays and ground faults to obtain the same effect. Of course, by applying a current transformer similar to transformer 9 to the instrument current transformer circuit as the current input circuit of the protective relay, it is possible to prevent the relay inspection current and the system transformation current from influencing each other. It can be supplied without any adverse effects. In particular, opening the secondary circuit of a current transformer during operation would result in an accident, so a method that causes the secondary circuit of a current transformer to open, such as the conventional changeover switch 8, cannot be applied. , the method of the present invention is extremely effective.

Further, although the embodiment shows a case where the inspection power transformer 9 is provided outside the relay 4, the same effect can be obtained by incorporating a small inspection power transformer in the relay.

In addition, although the example shows the case of manual inspection,
A test input voltage or current of the transformer 9 or an equivalent test current transformer is periodically applied by a programmed voltage (current) generator to enable automatic check and remote monitoring of the relay.

Furthermore, the inputs of the windings C and E can be switched between the inspection power supply side and the transformer side to obtain the same effect.

As described above, according to the method of the present invention, an AC input for inspection is given to the relay without disconnecting the input from the instrument transformer using a power transformer for inspection or a current transformer for inspection, which is a stationary device. Moreover, since the AC input for inspection and the transformation input of the system do not affect each other, inspection without blind spots from the input end to the output end of the relay is possible, and the problems caused by conventional transfer switches can be avoided. The reliability of the relay as a whole is improved by ensuring stable switching, coupling the inspection input with the system input by welding the switch contacts, and eliminating the dangers associated with inspections such as the opening of the secondary circuit of the current transformer when the switch is opened and closed. be able to.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining the conventional inspection method.
FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a diagram showing an embodiment of the power transformer for inspection in FIG. 4...Ground fault direction relay, 6...Grounding instrument transformer, 9...Inspection power transformer, 10...Inspection power switch, A...Iron core, A'...Intermediate iron core,
C...Inspection input winding, D...Voltage output winding,
E...Winding for zero-phase voltage input.

Claims (1)

[Claims] 1 A three-legged iron core having an intermediate core to form a closed magnetic circuit, a first input winding wound around the intermediate core of this iron core, and an iron core that connects the upper and lower parts of the three-legged iron core of the above-mentioned iron core, respectively. A second coil is wound and connected in series by being wound with approximately the same number of turns with the intermediate core as a boundary.
and an output winding that is wound around one of the outer leg cores of the three-legged core and outputs the input voltage or current of the protective relay. The transformed output from the device is connected to be input to one of the first and second input windings, and the inspection output from the inspection power source is input to the other of the first and second input windings. The transformation input from the instrument transformer and the inspection input from the inspection power supply are connected to each other so that the voltage or current induced in the other input windings is zero, and the transformation output or inspection output is output to the above output winding. An inspection method for protective relays that is characterized by taking them out as follows.