JP2004304915A - Differential protective relay system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a cable failure without installing a device that requires an insulating current transformer or a controlling power supply at an intermediate connecting portion that connects an aerial line and a cable line, and to make easy a harmonious operation with a differential relay for protecting a transmission line. <P>SOLUTION: This system is constituted of a first differential protective relay 11 that obtains a differential quantity by bringing in current signals each obtained at both terminals of a transmission line TL and protects the transmission line, an optical sensor 6 that converts the current signals each obtained from a terminal of the cable line 2 and the intermediate connecting portion into optical signals and outputs the signals, an optical transmission line 7 that transmits the outputs of the optical sensor in cascade, a photoelectric transducing means 15 that outputs the differential quantity of electrical signal out of the optical signals transmitted through the optical transmission line, and a second differential protective relay 12 that protects the cable line by bring in the differential quantity outputted from the photoelectric transducing means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD 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 a distance relay method, a direction comparison relay method, a phase comparison relay method, and a differential protection method. A current differential protection system is evaluated for being excellent in judging an accident section, and is often used for main protection of important trunk lines and the like.
[0003]
In this current differential protection system, a current signal detected for each terminal is transmitted and received between terminals by a current signal transmission means using a display line (communication line), wireless communication such as light or microwave, and a terminal is connected to each terminal. A vector sum and a scalar sum of currents are obtained, and it is determined whether an internal accident or an external accident in a protection section occurs based on whether or not these ratios have a predetermined relationship (for example, see Non-Patent Document 1). ).
[0004]
By the way, the transmission lines to be protected may be all overhead lines, some may be overhead lines, and the rest may be cable lines. I have. In other words, when the former transmission lines are all overhead lines, a sequence circuit is set up so that the circuit breaker is reclosed for each terminal when an accident is interrupted by the differential protection relay, but a part of the latter transmission line is used. In the case where is a cable line, a sequence circuit that locks the reclosing of the circuit breaker when a break due to a cable accident is established.
[0005]
FIG. 8 shows a configuration diagram in the case where a transmission line to be protected, which is configured by connecting an overhead line and a cable line in series, is protected by a conventional cable fault detection relay. In FIG. 8, A and B mean terminals of an electric station, respectively. TL is a transmission line linking the terminals A and B, and includes an overhead line 1 and a cable line 2 connected in series to one end of the overhead line 1. Although the connection between the overhead line 1 and the cable line 2 is usually called a cable entrance, it is called an intermediate connection here, and is denoted by reference numeral C. Generally, the intermediate connection portion C is not housed in an electric station. Therefore, the vicinity of the intermediate connection portion C is normally unmanned.
[0006]
3A and 3B are buses installed at terminals A and B, respectively, and 4A and 4B are installed at terminals A and B, respectively, connecting 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 type iron core current transformers. Among them, 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. It is installed in the section C.
[0007]
9A 'and 9B' are transmission line protection devices provided at the A terminal and the B terminal, respectively. Detection of an accident on the entire transmission line TL is performed by a differential protection relay for the transmission line, and detection of an accident on the cable line is performed on the cable line. It is configured to be performed by a differential protection relay. For this reason, the secondary current Ia of the current transformer 5A of the A terminal 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 at the intermediate connection portion C is supplied to the A terminal through the insulation current transformer 31c, the display line 32 and the insulation current transformer 31a, and the cable line differential protection relay (87C) is provided. 12 is input.
[0008]
Although the inside of the transmission line protection device 9B 'is not shown for the B terminal, the secondary current Ib of the current transformer 5B is similarly input to the transmission line differential protection relay (87) 11 of its own 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 fault has occurred. If an accident occurs at the point F of the cable line 2, the ratio between 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]
The above description is about the protection mode in the case where the cable line is differentially protected. FIG. 9 is a conventional example in which a cable accident is detected using a cable sheath. In this accident detection method, one terminal is grounded to prevent an induced current from flowing through the sheath itself, but the other terminal must be ungrounded. Are not grounded, 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 as those in the example of FIG. Reference numeral 2-1 denotes a sheath of the cable 2, and shows an example in which an intermediate connection portion C between the overhead line 1 and the cable line 2 is grounded by a ground line 2-2. 5D is a current transformer provided on the ground line 2-2, 41 is a current detector for taking in the output of the current transformer 5D and transmitting it to the far end A, which has a power supply inside. The output of the current detector 41 is transmitted to the terminal A via the transmission line 42, and a cable fault detection relay 43 at the terminal A determines whether or not a cable fault has occurred.
[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, the current transformer is provided at the intermediate connection part connecting the overhead line and the cable line, and the current extracted by this current transformer is transformed by the insulating transformer. In the technique of transmitting the current Ic obtained at the connection portion C to the terminal A through the display line and transmitting the current Ic obtained at the connection C to the terminal A, the transmission line TL is connected to the transmission line TL. It is necessary to configure the insulation current transformer 31 itself to withstand the high voltage generated in the current transformer when a large current flows, and to perform maintenance and inspection of the equipment after installation because of the high voltage resistance equipment. There is a drawback that requires great effort.
[0014]
Further, since the cable accident detection relay 12 and the protection relay device for protecting 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. Logic circuits were also needed.
[0015]
In the case of the conventional technique shown in FIG. 9, that is, the method of detecting a cable accident using a cable sheath, the detection target is a ground fault of the cable line. A control power supply for transmitting the detection current to the determination unit is required. In general, it is desirable to avoid installing a power supply at an unmanned remote end for maintenance and inspection.
[0016]
Therefore, the present invention can detect a cable accident without installing an insulated current transformer or a device that requires a control power supply at an intermediate connection section connecting the overhead line and the cable line, and can also be used to protect a transmission line. An object of the present invention is to provide a differential protection relay system that can easily cooperate with a differential relay.
[0017]
[Means for Solving the Problems]
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 transmission line configured by connecting a cable line to one end of an overhead line, A differential signal is obtained by introducing current signals obtained at both terminals of the transmission line, a first differential protection relay for protecting the transmission line, the cable line terminal, and an intermediate portion between the overhead line and the cable line. An optical sensor that converts a current signal obtained from each of the connection portions into an optical signal and outputs the optical signal; an optical transmission line that cascades and transmits the output of the optical sensor; and an optical signal that is transmitted through the optical transmission line And a second differential protection relay that introduces the differential amount output from the photoelectric conversion unit to protect the cable line. It was characterized by the door.
[0018]
Also, the invention of a differential protection relay system for a power system according to claim 2 is a differential protection relay system for protecting a transmission line configured by connecting a cable line to one end of an overhead line, wherein both ends of the transmission line are provided. A first differential protection relay for introducing a current signal obtained from a current transformer provided in the first line, obtaining a differential amount and protecting a transmission line, the cable line terminal, and an intermediate portion between the overhead line and the cable line. An optical sensor that converts a current signal obtained from a current transformer provided at each of the connection portions into an optical signal and outputs the optical signal; an optical transmission line that cascades the output of the optical sensor and transmits the optical signal; Photoelectric conversion means for outputting a differential amount of an electric signal from an optical signal transmitted through the optical path, and a second differential protection relay for protecting the cable line by introducing the differential amount output from the photoelectric conversion means It was characterized in that it is composed of.
[0019]
Furthermore, the invention of a power system differential protection relay system according to claim 6 is a differential protection relay system for protecting a transmission line configured by connecting a cable line to one end of an overhead line, wherein both ends of the transmission line are provided. The first differential protection relay for introducing the current signal obtained by each of the slaves to obtain the differential amount and protecting the transmission line, the cable line terminal, and the intermediate connection portion of the overhead line and the cable line. An optical sensor that converts the obtained current signal into an optical signal and outputs the signal, an optical transmission line that transmits the output of the optical sensor in a cascade, and an electric signal from the optical signal transmitted through the optical transmission line. A first differential protection relay for outputting a differential amount, and a second differential protection relay for introducing the differential amount output from the photoelectric conversion unit and protecting the cable line; When the dynamic protection relay operation gives the opening command to the circuit breaker, it said during the second differential protection relay operation, characterized by being configured to lock the reclosing of the first protective relay operation.
[0020]
Still further, the invention of a differential protection relay system according to claim 7 is a differential protection relay system that protects a transmission line configured by connecting a cable line to one end of an overhead line, wherein both terminals of the transmission line are used. Each of the obtained current signals is introduced to obtain a differential amount, and the differential amount is obtained from a first differential protection relay for protecting a transmission line, the cable line terminal, and an intermediate connection between the overhead line and the cable line. An optical sensor that converts the obtained current signal into an optical signal and outputs the optical signal; an optical transmission line that transmits the output of the optical sensor; and an optical signal that is transmitted through the optical transmission line is converted into an electric signal and output. A photoelectric conversion unit, and a second differential protection relay for introducing the electric signal output from the photoelectric conversion unit and the electric signal obtained from the cable line terminal to protect the cable line. Characterized in that the al configuration.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that parts and elements common to the drawings are denoted by the same reference numerals and description thereof is omitted.
[0022]
(First Embodiment)
FIG. 1 is a configuration diagram of a first embodiment according to a differential protection relay protection system of the present invention. In FIG. 1, A, B, 1, 2,..., 5C are the same as the components and elements shown in FIG.
[0023]
8A, 8B and 8C are control cables on the secondary side of the transformer for deriving the secondary currents Ia, Ib and Ic of the current transformers 5A, 5B and 5C, respectively. Reference numeral 6 denotes an optical sensor 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 line for transmitting an optical signal output from the optical sensor 6, and 9A and 9B denote transmission line protection devices installed at the A terminal and the B terminal, respectively. 9A of the transmission line protection device 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. And 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 devices 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-side control cable 8A is insulated by the input transformer 21, converted into a predetermined size, and then input to the analog / digital converter 22. Here, it is converted into digital data. The digital data is input to the determination unit 24 as the determination data IA, and is transmitted to the terminal B, which is the opposite end, via the transmission control unit 23.
[0025]
On the other hand, the current information Ib transmitted from the terminal B to the terminal A is received via the transmission control unit 23 and is input to the determination unit 24 as the 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 the two terminals by calculation. For example, the following determination expression (1) is obtained. It is determined whether or not the accident is caused by the transmission line TL depending on whether or not the case is satisfied.
[0026]
Iop = │IA + IB│
Ires = | IA | + | IB |
Judgment formula: Iop−kIres ≧ ko (1)
(However, k and ko are constants)
[0027]
This determination expression (1) is merely an example, and the determination unit 24 may add the following conditional expression (2) to this expression (1) under an AND condition.
Iop ≧ k1 (2)
(However, k1 is a constant)
In this case, when the formulas (1) and (2) are satisfied at the same time, the determining unit 24 determines that the transmission line TL has an accident.
[0028]
Next, the details of the cable line differential protection relay (87C) 12 will be described with reference to FIG. In FIG. 3, 6 to 8 are the same as the components 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 electric signal. The light source 14, the optical sensor 13, the optical sensor 6, and the photoelectric converter 15 are cascaded 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 is input, and the optical signal is converted into an electric signal and output.
[0029]
As described above, a photocurrent measuring device that connects the light source 14, the optical sensor 13, and the photoelectric converter 15 with the optical cable 7 is known, for example, from Japanese Patent Application Laid-Open No. 7-191061.
[0030]
Reference numeral 16 denotes a determination unit for inputting the difference current ID output from the photoelectric converter 15 to determine an accident of the cable line 2, and is constituted by a digital operation element such as a microcomputer. The determination unit 16 determines, for example, whether or not the cable line has an accident by the following equation (3).
Judgment formula: ID ≧ ko (3)
(However, ko is a constant)
[0031]
Reference numeral 17 denotes an input / output unit for passing the judgment output of the judgment unit 16 to the transmission line differential protection relay (87) 11A to form various sequences.
As described above, according to the present embodiment, no control power supply is required on the intermediate connection side between the overhead line and the cable line to detect an accident on the cable line, and there is no need to provide an insulating transformer, which is extremely simple. 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 according to the differential protection relay protection system of the present invention.
[0033]
The present embodiment is characterized in that the determination unit 16 and the input / output unit 17 of the cable line differential protection relay (87C) 12 described with reference to FIG. It is configured to be shared with the determination unit 24 and the input / output unit 25 of the electric wire protection device (87) 11.
[0034]
That is, the transmission line protection device 18A inputs the own-end determination data IA, the opposite-end determination data IB, and the difference current ID of the cable line to the determination unit 24, respectively, and determines the transmission line accident by the following determination formulas (4) and (5). And a determination of a 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. Can not expect. However, by making the operation amount ID of the differential protection relay for cable line (87C) 12 have a ratio characteristic by using the electric quantities IA and IB at its own end and the opposite end as a suppression amount, the detection sensitivity can be made high. it can. It should be noted that each of the determination formulas shows an example, 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 line accident) ... 87C judgment Iop = ID
Ires = | IA | + | IB |
Judgment formula: Iop−kIres ≧ ko (5)
(However, 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 the judging formula (5) is satisfied, a cutoff command from the input / output unit 25 to the circuit breaker does not perform a reclose. It becomes the final cutoff output. However, when the determination formula (4) is satisfied but the determination formula (5) is not satisfied, it can be considered that the overhead line 1 has an accident, so that a break command to the circuit breaker in consideration of the reclosing is performed.
[0037]
As described above, according to the present embodiment, in addition to the effects of the first embodiment, the fault detection determination unit for the cable line is built in the transmission line protection device, and the transmission line fault is determined by one determination unit. Since the judgment (87 judgment) and the cable line accident judgment (87C judgment) are performed, the relay device can be downsized as compared with a case where a differential protection relay is separately provided.
[0038]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a configuration in which an optical sensor 6 'is attached so as to go around the body of the cable line 2 which is the main circuit of the transmission line, thereby omitting the current transformer 5c installed on the intermediate connection portion C side in FIG. is there. Further, the determination formula of the cable line differential protection relay in this embodiment is the same as that in FIG. In FIG. 5, the transmission line differential protection relay 11 is not shown because it is complicated to draw.
[0039]
As described above, according to the present embodiment, in addition to the effects of the first embodiment, the current transformation is performed by directly attaching the optical sensor 6 ′ directly to the body of the cable line 2 at the intermediate connection portion C. The equipment can be omitted, and equipment costs can be reduced accordingly.
[0040]
(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
In the description of the above embodiments, the current of the three-phase power system is not particularly defined. However, in general, the transmission line differential protection relay uses the terminal current (Ir) of each phase (R phase, S phase, T phase). , Is, It), the present embodiment employs a differential protection for a cable line using a sample amount in order to reduce equipment including a display line and a protection relay. It constitutes a relay.
[0041]
As is well known, one-phase or two-phase electrical quantities are created as necessary from three-phase electrical quantities, and a typical example is a zero-zero value dedicated to a ground fault as shown in the following equation (1). It is a phase electricity quantity.
(1) (Ir + Is + It = 3Io) (for ground fault only)
If this sample amount dedicated to ground fault is applied to FIG. 1, three optical sensors 6 are required for each phase (R phase, S phase, and T phase), but three optical sensors 6 are required. There is an advantage that a single optical sensor can be used as a whole by winding all around the phase conductor.
[0042]
The following equation (2) is a method for sharing the detection of a short circuit and a ground fault by adding the current of the T phase to the current obtained by doubling the current of the R phase.
(2) 2Ir + It (short circuit, ground fault shared)
In this case, specifically, for example, an optical sensor may be wound around the R-phase conductor for two turns, and an optical sensor may be wound around the T-phase conductor for one turn, and the outputs of these two optical sensors may be combined. .
[0043]
Equation (3) is a method in which short-circuit detection is performed by subtracting the S-phase and T-phase currents from the value obtained by doubling 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 two turns, and the optical sensor is wound around the S-phase and T-phase conductors one turn each in the reverse direction, and these three light beams are wound. What is necessary is just to synthesize the output of a 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 the amount of equipment including a display line and a protection relay is reduced by introducing a sample amount of electricity. Can be.
[0045]
(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a diagram showing an example of processing the output of the transmission line protection device 9A, in which the operating conditions of the transmission line differential protection relay (87) 11 are added to the output of the cable line differential protection relay (87C) 12. FIG. 6A shows an example in which the condition of the differential protection relay (87) 11 for the transmission line is added to the indication / alarm of the reclosing lock and the cable accident, and FIG. An example is shown in which the display / alarm is performed by the output of the cable line differential protection relay (87C) 12 alone.
[0046]
(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to FIG.
The feature of this embodiment is that, as shown in FIG. 7, an optical sensor 13 for converting the secondary current Ia into an optical signal as shown in FIG. The optical sensor 6 is installed only at the intermediate connection portion C of the overhead line and the cable line without installing the optical signal, the optical signal is input to the transmission line protection device 18A 'via the optical cable 7, and the optical signal is A signal is converted into an electric quantity, 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 transmission line protection device, and the differential protection operation is performed. It was done.
[0047]
In FIG. 7, the determination unit 27 receives the own-end current Ia, the opposing-end current Ib, and the current Ic of the intermediate connection part C, and determines a transmission line accident and a cable line accident by the following judgment formulas (6) and (7). Identify. Although the determination unit 27 and the determination unit 24 of the second embodiment (FIG. 4) are similar in configuration, the difference between them is obtained at both ends of the cable line in the case of the second embodiment. In contrast to introducing the current difference ID, the present embodiment is different from the first embodiment in that the electric quantity Ic obtained at the intermediate connection portion C is introduced. As a result, as shown in (6) and (7), the determination formulas of the present embodiment are slightly different from the determination formulas (3) and (4) of the second embodiment.
[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)
It should be noted that each of the above determination formulas is an example, and there is no problem as long as the gist of the invention is satisfied.
[0049]
As described above, according to the present embodiment, as compared with the second embodiment, the terminal current is introduced into the differential relay for the cable line of the own terminal. Sensors 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 and does not need to provide an isolation transformer on the connection point side of an overhead line and a cable line as an accident detection of a cable line. A system can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first embodiment according to a differential protection relay protection system of the present invention.
FIG. 2 is a configuration diagram of a transmission line differential protection relay.
FIG. 3 is a configuration example diagram 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 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 structural example of a conventional differential protection relay for cable lines.
FIG. 9 is a diagram illustrating a configuration example of a conventional cable accident detection method.
[Explanation of symbols]
A, B: terminal of electric station, TL: transmission line, 1: overhead line, 2 ... cable line, 3A, 3B ... bus, 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: For transmission line Differential protection relay, 12: Differential protection relay for cable line, 13: Optical sensor, 14: Light source, 15: Photoelectric converter, 16: Judgment unit, 17: Input / output unit, 18, 18 ': Transmission line protection device , 21: input transformer, 22: analog-to-digital converter, 23: transmission control unit, 24: determination unit, 25: input / output unit, 27: determination unit.

Claims (7)

In a differential protection relay system that protects a 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 each of the two terminals of the transmission line to obtain a differential amount, and protecting the transmission line;
An optical sensor that converts the current signal obtained from each of the cable line terminals and the intermediate connection portion of the overhead line and the cable line into an optical signal and outputs the optical signal,
An optical transmission line for transmitting the output of the optical sensor in a cascade,
Photoelectric conversion means for outputting a differential amount of an electric signal from an optical signal transmitted through the optical transmission path;
A second differential protection relay that protects the cable line by introducing a differential amount output from the photoelectric conversion unit;
A differential protection relay system characterized by comprising: In a differential protection relay system that protects a 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 from a current transformer provided at both ends of the transmission line to determine a differential amount, and protecting the transmission line;
An optical sensor that converts a current signal obtained from a current transformer provided in each of the cable line terminal and the intermediate connection portion of the overhead line and the cable line into an optical signal and outputs the optical signal,
An optical transmission line for transmitting the output of the optical sensor in a cascade,
Photoelectric conversion means for outputting a differential amount of an electric signal from an optical signal transmitted through the optical transmission path;
A second differential protection relay that protects the cable line by introducing a differential amount output from the photoelectric conversion unit;
A differential protection relay system characterized by comprising: The optical sensor that converts the current signal obtained from the intermediate connection portion of the overhead line and the cable line into an optical signal and outputs the optical signal is an optical sensor provided so as to go around a main circuit conductor that forms a transmission line. The differential protection relay system according to claim 1, wherein: The difference according to any one of claims 1 to 3, wherein the amount of suppression of the second differential protection relay is created by a current signal of each terminal introduced to the first differential protection relay. Dynamic protection relay system. The differential protection relay according to any one of claims 1 to 3, wherein the electric signal to be introduced into the second differential protection relay is a sample current obtained by synthesizing each phase current. system. In a differential protection relay system that protects a 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 each of the two terminals of the transmission line to obtain a differential amount, and protecting the transmission line;
An optical sensor that converts the current signal obtained from each of the cable line terminals and the intermediate connection portion of the overhead line and the cable line into an optical signal and outputs the optical signal,
An optical transmission line for transmitting the output of the optical sensor in a cascade,
Photoelectric conversion means for outputting a differential amount of an electric signal from an optical signal transmitted through the optical transmission path;
And a second differential protection relay for introducing the differential amount output from the photoelectric conversion means to protect the cable line.
When the first differential protection relay is operated, a shutoff command is given to the circuit breaker, and when the second differential protection relay is operated, the reclosing circuit by the first protection relay operation is locked. Differential protection relay system. In a differential protection relay system that protects a 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 each of the two terminals of the transmission line to obtain a differential amount, and protecting the transmission line;
An optical sensor that converts the current signal obtained from each of the cable line terminals and the intermediate connection portion of the overhead line and the cable line into an optical signal and outputs the optical signal,
An optical transmission line for transmitting the output of the optical sensor;
Photoelectric conversion means for converting an optical signal transmitted through the optical transmission path into an electric signal and outputting the electric signal,
A differential protection relay for introducing the electric signal output from the photoelectric conversion means and the electric signal obtained from the cable line terminal to protect the cable line. Relay system.

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