JP4176529B2 - Differential protection relay system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a differential protection relay system for protecting a power system, particularly a transmission line.
[0002]
[Prior art]
In principle, transmission line protection methods include distance relay method, direction comparison relay method, phase comparison relay method, differential protection method, etc. A current differential protection method is evaluated for its superiority in determining the accident section, and is often used for main protection of important trunk lines.
[0003]
In this current differential protection method, the current signal detected for each terminal is transmitted and received between terminals by current signal transmission means using radio such as a display line (communication line), light, or microwave, and the terminal for each terminal. A vector sum and a scalar sum of currents are obtained, and it is determined whether the accident is an internal accident or an external accident in the protection section depending on whether these ratios are in a predetermined relationship (for example, see Non-Patent Document 1). ).
[0004]
By the way, there are cases where all of the transmission lines to be protected are overhead lines and some of the remaining overhead lines are cable lines. Yes. In other words, when all of the former transmission lines are overhead lines, a sequence circuit is built to reclose the circuit breaker for each terminal when an accident is interrupted by the differential protection relay. When a cable line is used, a sequence circuit that locks the reclosing circuit of the circuit breaker at the time of interruption due to a cable accident is built.
[0005]
FIG. 8 shows a configuration diagram in the case of protecting a transmission line that is a protection target configured by connecting an overhead line and a cable line in series with a conventional cable accident detection relay. In FIG. 8, A and B mean terminals of an electric station, respectively. TL is a power transmission line that links terminals A and B, and is composed of an overhead line 1 and a cable line 2 connected in series to one end of the overhead line 1. In addition, although the connection part of the overhead line 1 and the cable line 2 is normally called a cable lead-in port, it is called an intermediate connection part here, and it attaches | subjects and shows the code | symbol C. In general, the intermediate connection portion C is not housed in an electric station. Therefore, the vicinity of the intermediate connection portion C is normally unattended.
[0006]
3A and 3B are buses installed at terminals A and B, respectively. 4A and 4B are installed at terminals A and B, respectively, and connect buses 3A and 3B to the terminals of cable line 2 and overhead line 1 respectively. It is a circuit breaker. 5A, 5B and 5C are electromagnetic and iron core current transformers, among which 5A and 5B are installed at both terminals A and B of the transmission line TL, and 5C is an intermediate connection between the overhead line 1 and the cable line 2 Part C is installed.
[0007]
9A ′ and 9B ′ are power transmission line protection devices provided at the A terminal and the B terminal, respectively, and the fault detection of the entire power transmission line TL is performed by the differential protection relay for power transmission line, and the cable line fault detection is performed. It is configured to use a differential protection relay. For this reason, the secondary current Ia of the A terminal current transformer 5A is input in series to the transmission line differential protection relay (87) 11 and the cable line differential protection relay (87C) 12 installed at its own terminal, The secondary current Ic of the current transformer 5C installed in the intermediate connection portion C is the cable line differential protection relay (87C) provided at the A terminal through the insulation current transformer 31c, the display line 32 and the insulation current transformer 31a. 12 is input.
[0008]
In addition, although the inside of power transmission line protection apparatus 9B 'is not illustrated about B terminal, the secondary current Ib of the current transformer 5B is similarly input into the differential protection relay for power transmission lines (87) 11 of a self terminal. It is configured as follows.
[0009]
The cable line differential protection relay (87C) 12 performs a differential operation using the input secondary currents Ia and Ic to detect whether or not a cable accident has occurred. If an accident occurs at the point F of the cable line 2, the ratio of the vector sum current and the scalar sum current becomes larger than a predetermined value, and the cable line differential protection relay (87C) 12 operates.
[0010]
Although the above description relates to the protection mode when the cable line is differentially protected, FIG. 9 is a diagram showing a conventional example in which a cable accident is detected using a cable sheath. In this accident detection method, one terminal is grounded in order to prevent an induced current from flowing through the sheath itself, but the other terminal must be ungrounded. Is ungrounded, and the far end of the cable line is grounded.
[0011]
Reference numerals A, B, and 1 to 5B in FIG. 9 are the same elements as those in the example of FIG. Reference numeral 2-1 denotes a sheath of the cable 2 and shows an example in which the intermediate connection portion C side between the overhead line 1 and the cable line 2 is grounded by the ground line 2-2. Reference numeral 5D denotes a current transformer provided on the ground line 2-2, and reference numeral 41 denotes a current detector for taking the output of the current transformer 5D and transmitting it to a remote A end. The output of the current detector 41 is transmitted to the A end via the transmission line 42, and a cable accident detection relay 43 at the A end determines whether or not there is a cable accident.
[0012]
[Non-Patent Document 1]
The Institute of Electrical Engineers of Japan "Protective Relay Engineering", The Institute of Electrical Engineers of Japan, July 20, 1981, p. 150-154
[0013]
[Problems to be solved by the invention]
As described above, the conventional technique shown in FIG. 8, that is, a current transformer is provided in the intermediate connection part connecting the overhead line and the cable line, and the current extracted by this current transformer is transformed by the insulation transformer. In the technique of transmitting to the cable line differential protection relay via the display line, it is not necessary to provide a control power source in order to transmit the current Ic obtained at the connection C to the A terminal. It is necessary to configure so that the insulation current transformer 31 itself can withstand the high voltage generated in the current transformer when a large current flows. There is a drawback that requires a lot of effort.
[0014]
Further, since the cable accident detection relay 12 and the protective relay device that protects the transmission line TL are configured as separate devices, the output of the cable line differential protection relay 12 is input to the transmission line protection device. A logic circuit was also required.
[0015]
Further, in the case of the conventional technique shown in FIG. 9, that is, in the case of the method of detecting the cable accident using the cable sheath, the detection target is a ground fault of the cable line, A control power supply for transmitting the detected current to the determination unit is required. In general, it is desirable to avoid installing a power supply at the far end of an unattended for maintenance inspection.
[0016]
Therefore, the present invention can detect a cable accident without installing an insulation current transformer or a device that requires a control power source in an intermediate connection portion that connects an overhead line and a cable line, and is used for protecting a transmission line. It is an object of the present invention to provide a differential protection relay system that can easily cooperate with a differential relay.
[0017]
In order to achieve the above object, the invention of a differential protection relay system according to claim 1 is a differential protection relay system for protecting a power transmission line configured by connecting a cable line to one end of an overhead line. A first differential protection relay for introducing a current signal obtained at both terminals of the transmission line to obtain a differential amount and protecting the transmission line, and the cable line among the two terminals of the transmission line. a cable line terminal is to have side terminal, the overhead line and cable line and an optical sensor which converts the current signal obtained by the respectively provided on the intermediate connecting portion each such terminal into an optical signal output to be connected When the optical transmission path for transmitting the output of each optical sensor in a cascade, a photoelectric conversion means for outputting the differential amount of the electric signal from the optical signal transmitted through said optical transmission path, wherein the photoelectric conversion A differential amount output from the means and the introduced scalar sum current obtained from the current of the terminals of the transmission line is composed of a second differential protection relay for protecting remembering ratio characteristic cable line It is characterized by that.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected about the component and element which are common throughout each figure, and description is abbreviate | omitted.
[0022]
(First embodiment)
FIG. 1 is a configuration diagram of a first embodiment relating to a differential protection relay protection system of the present invention. In FIG. 1, A, B, 1, 2,..., 5C are the same as the parts and elements shown in FIG.
[0023]
8A, 8B and 8C are transformer secondary control cables for deriving secondary currents Ia, Ib and Ic of the current transformers 5A, 5B and 5C, respectively. An optical sensor 6 is provided on the secondary control cable 8C of the current transformer 5C, and is configured to output an optical signal corresponding to the input current by inputting the secondary current Ic. Reference numeral 7 denotes an optical cable as an optical transmission path for transmitting an optical signal output from the optical sensor 6, and 9A and 9B denote power transmission line protection devices installed at the A terminal and the B terminal, respectively. Among these transmission line protection devices, 9A includes a transmission line differential protection relay (87) 11A as a first differential protection relay and a cable line differential protection relay (87C) 12 as a second differential protection relay. The transmission line protection device 9B includes only a transmission line differential protection relay (87) 11B as a first differential protection relay. 10A and 10B are carrier wave transmission apparatuses for transmitting and receiving current information between the A terminal and the B terminal.
[0024]
FIG. 2 is a diagram showing details of the transmission line differential protection relay (87) 11A installed at the A terminal. The secondary current Ia of the current transformer 5A input from the transformer secondary control cable 8A is insulated by the input transformer 21 and converted into a predetermined magnitude, and then input to the analog / digital converter 22. Here, it is converted into digital data. This digital data is input to the determination unit 24 as determination data IA and is transmitted to the B terminal which is the opposite end via the transmission control unit 23.
[0025]
On the other hand, the current information Ib transmitted from the B terminal to the A terminal is received via the transmission control unit 23 and input to the determination unit 24 as determination data IB.
The determination unit 24 calculates an operation amount (vector sum current) Iop and a suppression amount (scalar sum current) Ires from the input determination data IA and IB for two terminals. For example, the following determination formula (1) is obtained. Whether or not the transmission line TL is in an accident is determined depending on whether or not it is established.
[0026]
Iop = │IA + IB│
Ires = │IA│ + │IB│
Judgment formula: Iop−kIres ≧ ko (1)
(However, k and ko are constants.)
[0027]
The determination formula (1) is merely an example, and the determination unit 24 may add the following conditional expression (2) to the expression (1) under an AND condition.
Iop ≧ k1 (2)
(Where k1 is a constant)
In this case, the determination part 24 determines with the accident of the power transmission line TL, when Formula (1) and Formula (2) are materialized simultaneously.
[0028]
Next, the details of the cable line differential protection relay (87C) 12 will be described with reference to FIG. Also in FIG. 3, 6 to 8 are the same as the parts and elements already described in FIG. Reference numeral 13 denotes an optical sensor similar to the optical sensor 6, reference numeral 14 denotes a light source, and reference numeral 15 denotes a photoelectric converter (O / E converter) as photoelectric conversion means for converting an optical signal into an electrical signal. The light source 14, the optical sensor 13, the optical sensor 6, and the photoelectric converter 15 are connected in cascade by the optical cable 7, and the photoelectric converter 15 corresponds to the difference current ID between the secondary currents Ia and Ic from the optical cable 7. An optical signal to be input is input, and the optical signal is converted into an electrical signal and output.
[0029]
As described above, a photocurrent measuring device for connecting the light source 14, the optical sensor 13, and the photoelectric converter 15 by the optical cable 7 is known from, for example, Japanese Patent Laid-Open No. 7-191061.
[0030]
Reference numeral 16 denotes a determination unit that inputs the difference current ID output from the photoelectric converter 15 and determines an accident of the cable line 2, and is constituted by a digital arithmetic element such as a microcomputer. For example, the determination unit 16 determines whether or not the cable line has an accident according to the following equation (3).
Judgment formula: ID ≧ ko (3)
(Where ko is a constant)
[0031]
Reference numeral 17 denotes an input / output unit for passing the determination output of the determination unit 16 to the transmission line differential protection relay (87) 11A to form various sequences.
As described above, according to the present embodiment, a control power supply is not required on the intermediate connection side between the overhead line and the cable line, and an insulation transformer is not required for detecting an accident in the cable line. A differential protection relay system can be provided.
[0032]
(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram of a second embodiment relating to the differential protection relay protection system of the present invention.
[0033]
The feature of this embodiment is that the determination unit 16 and the input / output unit 17 of the differential protection relay for cable line (87C) 12 described with reference to FIG. The electric wire protection device (87) 11 is configured to be shared with the determination unit 24 and the input / output unit 25.
[0034]
That is, the transmission line protection device 18A inputs the own end determination data IA, the opposite end determination data IB, and the cable line difference current ID to the determination unit 24, respectively, And the determination of the cable line accident. When the differential protection relay for cable line (87C) 12 is determined only by the difference current, that is, the operation amount ID, the detection sensitivity needs to take into account the error characteristics of the current transformer and the optical sensor. I can't hope. However, it is possible to increase the detection sensitivity by providing a ratio characteristic by using the electric quantities IA and IB of the own end and the opposite end as the suppression amount to the operation amount ID of the differential protection relay for cable line (87C) 12. it can. In addition, all the judgment formulas show examples, and there is no problem as long as the gist of the present invention is satisfied.
[0035]
(Transmission line accident)… 87 judgment Iop = │IA + IB│
Ires = │IA│ + │IB│
Judgment formula: Iop-kIres ≧ ko (4)
(However, k and ko are constants.)
(Cable track accident) ... 87C judgment Iop = ID
Ires = │IA│ + │IB│
Judgment formula: Iop−kIres ≧ ko (5)
(Where k and ko are constants)
[0036]
As a result of judging these formulas (4) and (5), in the case of an accident in the cable line section where judgment formula (5) is established, the shutoff command from the input / output unit 25 to the circuit breaker is not reclosed. Final shutoff output. However, if the determination formula (4) is satisfied but (5) is not satisfied, it can be regarded as an accident in the overhead line 1, and therefore a disconnection command is issued to the circuit breaker considering reclosing.
[0037]
Above As mentioned, in addition to the effects of the first embodiment according to the present embodiment, a built-in fault detection determination unit of the cable line in the transmission line protection devices, power line fault in one of the determination section Since the determination (87 determination) and the cable line accident determination (87C determination) are performed, the relay device can be downsized as compared with the case where a differential protection relay is provided separately.
[0038]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 omits the current transformer 5c installed on the side of the intermediate connection C in FIG. 1 by attaching the optical sensor 6 ′ so as to go around the body of the cable line 2 which is the main circuit of the transmission line. is there. In addition, the determination formula of the differential protection relay for cable line in this embodiment is the same as that in FIG. In addition, in FIG. 5, since it will become complicated if the power transmission line differential protection relay 11 is drawn, illustration is omitted dare.
[0039]
As described above, according to the present embodiment, in addition to the effects of the first embodiment, the optical sensor 6 ′ is directly attached to the body of the cable line 2 of the intermediate connection portion C so as to transform the current. The equipment can be omitted, and the equipment cost can be reduced accordingly.
[0040]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
In the description of the embodiments so far, the current of the three-phase power system was not particularly defined, but in general, the transmission line differential protection relay is a terminal current (Ir) of each phase (R phase, S phase, T phase). , Is, It) is used for the differential determination, but in this embodiment, the cable line differential protection using the sample amount is used to reduce the size of the equipment including the display line and the protective relay. It constitutes a relay.
[0041]
As is well known, the sample quantity is a one-phase or two-phase quantity of electricity created from the three-phase quantity of electricity as required. A typical one is a zero for ground faults as shown in the following formula (1). The amount of phase electricity.
▲ 1 ▼ (Ir + Is + It = 3Io) (Ground fault only)
If this sample amount dedicated to the ground fault is applied to FIG. 1, one optical sensor 6 is required for each phase (R phase, S phase, T phase), but a total of three optical sensors 6 are required. By collectively winding the phase conductors, there is an advantage that only one optical sensor is required.
[0042]
The following equation (2) is a method for sharing the short-circuit and ground fault detection by adding the T-phase current to twice the R-phase current.
(2) 2Ir + It (Short circuit, ground fault shared)
In this case, specifically, for example, the optical sensor is wound around the R-phase conductor for two turns, the optical sensor is wound around the T-phase conductor for one turn, and the outputs of these two optical sensors are combined. .
[0043]
Equation (3) is a method in which short-circuit detection is performed by subtracting the S-phase and T-phase currents from twice the R-phase current.
(3) 2Ir-Is-It (short circuit only)
In this case, specifically, for example, the optical sensor is wound around the R-phase conductor for two turns, and the optical sensor is wound around the S-phase and T-phase conductors for one turn in the opposite direction. What is necessary is just to synthesize the output of the sensor.
[0044]
As described above, according to the fifth embodiment, it is possible to provide a differential protection relay for a cable line in which equipment including a display line and a protective relay is reduced by introducing a sample quantity of electricity. Can do.
[0045]
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a diagram illustrating an example of processing the output of the power transmission line protection device 9A. The operating condition of the power transmission line differential protection relay (87) 11 is added to the output of the cable line differential protection relay (87C) 12. 6 (a) shows an example in which the condition of the differential protection relay for power transmission line (87) 11 is added to the reclosing lock and cable fault indication / alarm, and FIG. 6 (b) shows the cable fault. The example which comprised so that a display and an alarm may be performed by the output of the differential protection relay for cable lines (87C) 12 alone is shown.
[0046]
(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 7, the present embodiment is characterized by an optical sensor 13 for converting the secondary current Ia into an optical signal as shown in FIG. 5 on the side of the current transformer 5A installed at the A end. Without installing the optical sensor 6, the optical sensor 6 is installed only in the intermediate connection portion C between the overhead line and the cable line, the optical signal is input to the power transmission line protection device 18 A ′ via the optical cable 7, and the photoelectric converter 15 A signal is converted into an electric quantity, and an operation amount and a suppression amount are created from the current signal Ic obtained at the intermediate connection portion C and the current signals Ia and Ib of the power transmission line protection device, and a differential protection operation is performed. It is a thing.
[0047]
In FIG. 7, the determination unit 27 inputs the own-end current Ia, the opposite-end current Ib, and the current Ic of the intermediate connection portion C. Identify. The determination unit 27 and the determination unit 24 of the second embodiment (FIG. 4) are similar in configuration, but the difference between the two is obtained at both ends of the cable line in the case of the second embodiment. In contrast to the introduction of the current difference ID, in the present embodiment, the amount of electricity Ic obtained at the intermediate connection C is introduced. As a result, the determination formulas of the present embodiment are slightly different from the determination formulas (3) and (4) of the second embodiment, as shown by (6) and (7).
[0048]
(Transmission line accident)… 87 judgment Iop = │IA + IB│
Ires = │IA│ + │IB│
Judgment formula: Iop−kIres ≧ ko (6)
(However, k and ko are constants.)
(Cable line accident)… 87C judgment Iop = │IA + IC│
Ires = │IA│ + │IC│
Judgment formula: Iop−kIres ≧ ko (7)
(However, k and ko are constants.)
Each of the above-described determination formulas shows an example, and there is no problem as long as the gist of the invention is satisfied.
[0049]
Above As mentioned, according to this embodiment, compared with the second embodiment, since as to introduce terminal current in the cable line differential relay of its own terminal, for one piece self-terminal The light sensor can be omitted.
[0050]
【The invention's effect】
As described above, according to the present invention, a simple differential protection relay that does not require a control power supply on the connection point side of the overhead line and the cable line and does not need to provide an insulation transformer as a fault detection of the cable line. A system can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment relating to a differential protection relay protection system of the present invention.
FIG. 2 is a configuration diagram of a power transmission line differential protection relay.
FIG. 3 is a configuration example of a cable line differential protection relay.
FIG. 4 is a configuration diagram of a second embodiment according to the differential protection relay protection system of the present invention.
FIG. 5 is a configuration diagram of a third embodiment according to the differential protection relay protection system of the present invention.
FIG. 6 is a diagram showing an output relationship between a power transmission line differential protection relay and a cable line differential protection relay.
FIG. 7 is a configuration diagram of a third embodiment according to the differential protection relay protection system of the present invention.
FIG. 8 is a configuration example of a conventional differential protection relay for cable lines.
FIG. 9 is a configuration example of a conventional cable accident detection method.
[Explanation of symbols]
A, B ... Electric terminal, TL ... Transmission line, 1 ... Overhead line, 2 ... Cable line, 3A, 3B ... Busbar, 4A, 4B ... Breaker, 5A, 5B, 5C ... Current transformer, 6 ... Optical sensor, 7 ... Optical transmission line (optical cable), 8A, 8B, 8C ... Transformer secondary side control cable, 9A, 9B ... Transmission line protection device, 10A, 10B ... Carrier wave transmission device, 11A, 11B ... Differential protection relay, 12 ... Differential protection relay for cable line, 13 ... Optical sensor, 14 ... Light source, 15 ... Photoelectric converter, 16 ... Determination unit, 17 ... Input / output unit, 18, 18 '... Transmission line protection device 21 ... an input transformer, 22 ... an analog-digital converter, 23 ... a transmission control unit, 24 ... a determination unit, 25 ... an input / output unit, 27 ... a determination unit.

Claims (1)

In the differential protection relay system that protects the transmission line configured by connecting the cable line to one end of the overhead line,
A first differential protection relay for introducing a current signal obtained at each of both terminals of the transmission line to obtain a differential amount and protecting the transmission line;
Wherein the cable line terminal is the terminal on the side which is constituted by a cable line, obtained in the overhead line and respectively to the intermediate connection portion provided corresponding respective terminals for connecting the cable line, of the two terminals of the power transmission line An optical sensor that converts the output current signal into an optical signal and outputs it,
An optical transmission path for transmitting the output of each optical sensor in cascade;
Photoelectric conversion means for outputting a differential of an electric signal from the optical signal transmitted through said optical transmission path,
A second differential protection relay that protects the cable line with a ratio characteristic by introducing a differential amount output from the photoelectric conversion means and a scalar sum current obtained from currents of both terminals of the transmission line ; differential protection relay system characterized by being configured from.

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