JP2683183B2 - How to prevent unnecessary operation of protective relay for AC feeding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection relay system for a feeder circuit in which an electric vehicle runs at high speed by providing a switching section for different power sources in front of a substation in an AC electric railway.

[0002]

2. Description of the Related Art FIG. 1 is a circuit diagram showing a part of the connection between a conventional AC feeding circuit and a protective relay, which is converted by a feeding transformer 1 into two sets of single-phase AC of M seat and T seat. It is received by each direction. This electric power is stepped down by the autotransformer AT2, and the electric vehicle 1 is driven by the trolley wire 3 and the rail 4.
Supply power to 6 and 17.

The amount of electricity in an AC electric railway substation is
Distance relays (44F) 1 as protective relays by converting the current transformers CT11, 12 for meters into small currents suitable for the measurement system
4. Inputting to the AC ΔI type fault selecting device (50F) 15, the feeding voltage is converted into a small voltage suitable for the measuring system by the instrument transformer PT13 and is input to the distance relay (44F) 14. The T-phase currents I _T and F of the feeder transformer are
The phase currents I _F are input to the protective relays 14 and 15 as the outputs of the current transformers for instruments, respectively, and then combined in the protective relays.

In the feeder circuit, the resistance R and the reactance X are distributed in the length direction, and the impedance Z thereof is expressed by the following equation.

[0005]

## EQU1 ## Z = R + jX

The protection characteristics of the distance relay (44F) 14 can be represented on the complex plane of FIG. 2 with the resistance R on the horizontal axis and the reactance jX on the vertical axis. On this complex plane, the line impedance 18 is on a line of about 75 °, and the distance relay (44F) 14 calculates the impedance from the voltage and the current, and the parallelogram 19 including the line impedance 18 of the feeder circuit is used as the protection area. If the calculated impedance is within the protection area, it is regarded as a failure and the circuit breaker 9 removes the failure. In FIG. 2, the electric car 1 is running
The load characteristic of 7 can be drawn like the load region 20,
The power factor angle is in the direction of about 40 °, and as the load current increases, the impedance decreases and approaches the origin. On the other hand, in FIG. 1, when the electric vehicle 16 enters the different power source switching section 8, the switching switch 6 is turned off, and the switching switch 7 is turned on after 300 ms, depending on the turning-on phase,
As shown in FIG. 4, a large no-load excitation inrush current 25 flows through the vehicle transformer. The no-load excitation inrush current has an asymmetric vertical waveform and contains a large amount of second harmonic current, so the second harmonic content ratio to the fundamental current is, for example, 12%.
If so, the output of the distance relay is locked so that unnecessary operation does not occur even if the region 21 of the exciting inrush current enters the protection region of the distance relay from the direction of the power factor angle 80 ° to 90 ° in FIG. There is.

On the other hand, the current change in the AC feeding circuit is as shown in FIG. 3, and the current change 24 due to the notch of the electric vehicle is small, and the current change 23 due to the fault current is large. Utilizing this feature, the AC ΔI type fault selection device (50F) 15 determines that a fault exists if ΔI equal to or more than the set value, and the breaker 9 removes the fault current.
However, when the electric vehicle 16 enters the switching section 8, a large no-load excitation inrush current 25 flows in the vehicle transformer as shown in FIG. 4, and the value of the current change ΔI is large. The failure selection device (50F) 15 may operate. Therefore, as in the case of the distance relay (44F) 14, the second harmonic content rate with respect to the fundamental current is
For example, if it is 12% or more, the AC ΔI type failure selection device (5
The output of 0F) 15 is locked to prevent unnecessary operation.

[0008]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention Conventional distance relays and AC ΔI type fault selectors are used in vehicle transformers with large values, which occur when an electric vehicle passes through a different power source switching section in front of a substation. The second harmonic content rate is detected for the load excitation inrush current, and when the value is above a certain value, the output of the relay is locked to prevent unnecessary operation. However, recently, the load on the electric vehicle has increased remarkably, and as shown in FIG. 5, the load current 26 of the preceding electric vehicle is often combined with the no-load excitation inrush current 25 of the different power source switching section to become a current 27. ing. The power factor angle of the load current I _L of the preceding electric vehicle is about 40 °, and the power factor angle of the no-load excitation inrush current I _e is about 8 °.
Since it is 0 °, the combined feeding current I _S 27 of the substation is given by the following equation, and is widely distributed between the power factor angle of the electric vehicle load and the no-load excitation inrush current.

[0009]

[Equation 2] I _S = I _L ∠−40 ° + I _e ∠−80 °

Since the synthesized current 27 has a small second harmonic content rate, the second harmonic content rate is smaller than the set value of the protective relay, for example, 12%, and enters the protection area 19 of the distance relay. In that case, the lock may not work and unnecessary operation may occur. In addition, as shown in FIG. 5, even for the AC ΔI type fault selecting device, the second harmonic content rate is, for example, 12% or less, which is the set value of the protective relay, and the current change ΔI is larger than the set value. If so, unnecessary operation may occur.

The invention of claim 1 has been made to solve the above problems, and can reliably protect the feeder circuit when the feeder circuit fails, and at the same time, it can transform the AC electric vehicle in the different power source switching section. It is an object of the present invention to provide a protective relay method capable of reliably preventing an unnecessary operation due to a combination of a no-load excitation inrush current of a device and a load current of a preceding electric vehicle.

[0012]

According to a first aspect of the present invention, a no-load excitation inrush current of a transformer for an electric vehicle passing through a different power source switching section is measured by providing a current transformer for an instrument in the switching section. It is characterized in that the apparent no-load excitation inrush current is reduced by subtracting it from the no-load excitation inrush current input to the feeder circuit protection relay to prevent unnecessary operation of the protection relay.

[0013]

[Operation] At an AC feeding substation, it is possible to prevent unnecessary operation of the feeding circuit protection relay by combining the no-load excitation inrush current of the main transformer for the electric vehicle and the load current of the preceding electric vehicle, and ensure stable transportation of the electric vehicle. Can contribute to.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for preventing unnecessary operation of a protective relay for AC feeding of the present invention will be described with reference to the drawings. FIG. 6 shows an example of the basic configuration of the method for preventing unnecessary operation of the protective relay for AC feeding according to the present invention.
_Is inserted, and the switching section current I _sn is measured. The switching section current I _sn is an appropriate magnification 1 / by the auxiliary CT30.
If it is reduced by m times and connected in parallel to the trolley wire side CT11 in reverse polarity, the input current I _RY seen from the protective relay becomes the following equation, and the no-load excitation inrush current input to the protective relay is apparently small. Become.

[0015]

## _EQU00003 ## I _RY = (I _T + I _F ) -I _sn / m

In the AT feeding system of FIG. 6, since the transformer voltage is stepped down by a factor of two by AT, the sum of the T-phase current I _T and the F-phase current I _F of the transformer current is the electric vehicle. It corresponds to the current flowing in, and when the load exists only in the switching section, the following equation is obtained.

[0017]

## _EQU00004 ## I _sn = I _T + I _F

[0018] The switching section current I _sn and the load current (I _T
+ I _F ), and the current I _Ry input to the protective relay are shown in FIG. 7, the electric vehicle 16 enters the switching section 8, opens the switching switch A6, and 300 ms later, the switching switch is opened. When B7 is turned on, a no-load exciting inrush current flows through the vehicle transformer. The no-load excitation inrush current is rapidly attenuated, and then the power running current of the electric vehicle starts to flow. The end of the switching section is composed of an air section 29 that allows the pantograph to pass smoothly.
Further, an electric car collects power by a plurality of pantographs, and these pantographs are generally connected in parallel by a special high voltage electric wire. Therefore, further advanced electric vehicle, the electric vehicle pantograph shorting the air section 29, an electric vehicle current to the current i ₁ supplied from the switching section 6 is supplied from the trolley line of the main line Current i ₂ is divided. Therefore, the air section current I _sn is halved at this point. Further, when the electric car progresses and passes through the switching section, I _sn becomes zero. On the other hand, the load current ( _IT + _IF ) is independent of the pantograph passing through the air section 29.

The input current of the protective relay according to the unnecessary operation preventing method of the protective relay for AC feeding of the present invention is as shown in the protective relay input current I _Ry of FIG. 7, and the constant m of the auxiliary CT30.
Depending on the value of, the magnitude of the no-load excitation inrush current of the vehicle transformer is significantly reduced, and as a result, unnecessary operation of the protective relay can be prevented. On the other hand, when the pantograph passes through the air section 29, a change in current ΔI occurs. That is, if the value of m is set to 1, for example, the electric current when the electric vehicle is only in the switching section is canceled and becomes zero, but the current change ΔI when the pantograph passes through the air section 29 becomes large. , Is not preferable for the AC ΔI type failure selection device 15. For this reason, it is possible to reduce the current change ΔI by selecting about 1.5 to 3 as the value of the constant m.

Since the switching section current I _sn is subtracted from the protective relay input, when a short circuit fault occurs in the switching section 8, the fault current input to the protective relay becomes smaller than it actually is, and the existing protective relay 14 , 15, the protective ability decreases. For this reason, an overcurrent relay 31 with a lock function by the second harmonic current is provided on the secondary side of the current transformer 28 for the instrument inserted in the switching section so as not to operate with the vehicle transformer no-load excitation inrush current. It is desirable to install and detect switching section failures.

[0021]

As described above, according to the present invention, the no-load excitation inrush current of the vehicle transformer having a large value generated when the electric vehicle passes through the different power source switching section in front of the substation for the AC electric railway. Is detected by an instrument current transformer inserted in the switching section and is subtracted from the input of the protective relay to make it apparently small, so that unnecessary operation of the protective relay can be prevented.

[Brief description of the drawings]

FIG. 1 is an example of a circuit diagram showing a part of the connection between a conventional AC feeding circuit and a protective relay.

FIG. 2 is a complex plan view showing a protection range of a protective relay and an electric vehicle load area.

FIG. 3 is a current change example of a load current and a fault current in an AC feeding circuit.

FIG. 4 is an example of a no-load excitation inrush current waveform of a vehicle transformer.

FIG. 5 is an example of a current waveform in which an electric vehicle power running load current and a no-load excitation inrush current of a vehicle transformer are combined.

FIG. 6 is a basic configuration of an unnecessary operation preventing method for a protective relay for AC feeding of the present invention.

FIG. 7 is a variation example of the load current synthesized by the method for preventing unnecessary operation of the protective relay for AC feeding of the present invention.

[Explanation of symbols]

1 Feeding transformer 2 Autotransformer AT 3 Trolley wire 4 Rail 5 Feeding wire 6 Open side switching switch 7 Closing side switching switch 8 Switching section 9 Feeding circuit breaker 10 Feeding circuit breaker 11 T phase Side current transformer CT 12 F phase current transformer CT 13 Meter transformer PT 14 Distance transformer PT 14 Distance relay (44F) 15 AC ΔI type fault selection device (50F) 16 Electric vehicle in switching section 17 General Electric vehicle existing in the electricity section 18 Line impedance 19 Protective area of distance relay 20 Load area of electric vehicle running 21 Area of no-load excitation inrush current of vehicle transformer 22 Power vehicle current and no vehicle transformer Region where load excitation inrush current is combined 23 Current change due to fault current of train line 24 Current change due to notch step of electric vehicle 25 Waveform example of no-load excitation inrush current of vehicle transformer 26 Example of load current waveform of preceding electric vehicle 27 Leading electric car Current waveform example in which load current and no-load excitation inrush current of vehicle transformer are combined 28 Current transformer CT for an instrument for measuring electric vehicle current existing in different power source switching section according to the present invention CT 29 Air section 30 Auxiliary CT 31 Overcurrent relay

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minor Kayama Minoru 1-4-1 Nakamura-ku, Nagoya-shi, Aichi Prefecture Tokai Passenger Railway Co., Ltd. (72) Kenji Nakamura Ken-ichi, Nakamura-ku, Nagoya-shi, Aichi No. 1-4 No. 1 Tokai Passenger Railway Co., Ltd. Examiner Isao Tachikawa (56) References Japanese Patent Laid-Open No. 2-60402 (JP, A) SAI 58-92138 (JP, U)

Claims (1)

(57) [Claims] 1. A distance relay for detecting a failure by an impedance value of the feeder circuit when a failure occurs in the AC feeding circuit, and an AC ΔI type failure selecting device for detecting a failure by selecting a change in current. In a protective relay system that uses an electric vehicle, a current transformer for instruments is inserted in the different power source switching section in front of the substation for electric railways, and the transformer for the vehicle with the large value generated when the electric vehicle passes through the switching section is inserted. To prevent unnecessary operation of the protective relay by combining the no-load excitation inrush current of the vehicle transformer and the load current of the preceding electric vehicle by detecting the no-load excitation inrush current of the transformer and subtracting it from the input of the protective relay. A method for preventing unnecessary operation of a protective relay for AC feeding characterized by.