JPH0582132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a protective relay device for protecting busbars in an electric power system.

[Prior art]

The busbar is the key to the power system configuration, and power is transported from the busbar side to the load side by a plurality of power transmission lines branch-connected to the busbar. Therefore, interruption of power at the bus bar immediately has a serious impact on a wide range of loads, and bus bar protection is extremely important.

In this way, protective relay devices for protecting power systems from internal accidents that occur on busbars were developed, for example, in the Showa era.
It is shown in "Chapter 9 of the Institute of Electrical Engineers of Japan University Course Protective Relay Engineering" published by the Institute of Electrical Engineers of Japan on July 20, 1956, and Figures 5 and 6 show the circuit diagrams of the protective relay device. There is.

These protective relay devices connect multiple power transmission lines 5,
The protection operation is based on the basic principle that Kirchhoff's law is established at the position where each of the currents 6 and 7 flows into the bus bar 1. In both devices, if no fault occurs in bus 1 and transmission lines 5, 6, 7, the vector composite value of the secondary currents of current transformers 2, 3, 4 will be zero, but if a fault occurs In this case, the value corresponds to the fault current. Therefore, an accident can be detected by detecting this vector composite value.

FIG. 5 shows a high impedance type protective relay device, in which power transmission lines 5, 6, and 7 are branch-connected to a bus 1. Also, current transformers 2, 3, 4 are provided corresponding to each power transmission line 5, 6, 7.
Each is connected in parallel. A series circuit of a fundamental wave filter 9 and an overvoltage relay 10 is connected to the current transformers 2, 3, and 4 connected in parallel, and a nonlinear resistor 8 is connected in parallel to this series circuit.

In the event of an internal accident, the secondary currents of each current transformer 2, 3, and 4 will all be in the same direction and will no longer be able to circulate with each other.
The voltage across the series circuit of the fundamental wave filter 9 and the overvoltage relay 10 of the differential circuit 20 consisting of the nonlinear resistor 8 connected in parallel to the series circuit of the fundamental wave filter 9 and the overvoltage relay 10 increases, and the overvoltage relay 1
0 detects that voltage and performs a protective operation. At this time, the nonlinear resistor 8 prevents the voltage of the differential circuit 20 from becoming excessive. On the other hand, accidents that occurred on power transmission lines,
In other words, in the case of an external fault, the current transformer installed on the relevant power transmission line becomes magnetically saturated, but the current of other non-magnetically saturated current transformers is transferred to current transformers whose excitation impedance has decreased due to magnetic saturation caused by the fault current. and does not flow to the differential circuit 20, the voltage of the differential circuit 20 does not rise, and no external fault is detected.

Figure 6 shows a low-impedance protective relay device, in which power transmission lines 5, 6, and 7 are branch-connected to a bus 1, and current transformers 2 and 2 are connected to each power transmission line 5, 6, and 7. , 3 and 4 are provided. These current transformers 2,
The respective outputs of 3 and 4 are input to converters 11, 12, 1
3 are each input. Each input converter 11, 12,
13 indicates secondary AC voltages V _O1 , V O2 , V _Oo , which are the AC components of the secondary currents of the current transformers 2, 3, _{and 4} , and the current transformers 2,
Secondary DC voltage V _R1 obtained by rectifying the secondary currents of 3 and 4,
Output V _R2 and V _Ro . and input converter 11,
The AC operating voltage V _O is a vector combination of the secondary AC voltages V _O1 , V _O2 , V _Oo of 12 and 13, and the DC suppression voltage V _R is a scalar combination of the secondary DC voltages V _R1 , V _R2 , V _Ro . It is input to the ratio differential relay 14.

Then, the differential relay 14 operates at an AC operating voltage V _O
= (sum of V _O1 , V _O2 , V _Oo ) and DC suppression voltage V _R =
(sum of V _R1 , V _R2 , and V _Ro ).

In the event of an internal fault, each current flowing into bus 1 will flow in the same direction, and the AC operating voltage V _O will rise.
The AC operating voltage V _O is proportional to the DC suppression voltage V _R as a proportional constant K.
When the value exceeds KV _R multiplied by , the differential relay 14 performs a protective operation. On the other hand, in the event of an external accident,
The error current of the magnetically saturated current transformers 2, 3, and 4 flows into a differential circuit with low circuit impedance that vector-synthesizes the secondary _AC voltage. Since it obtains a DC suppression voltage V _R and performs ratio differential operation, it does not detect external faults.

[Problems to be solved by the invention] By the way, when considering the application of optical current transformers that utilize the Faraday effect, which has emerged due to the recent development of optical technology, for the protection of such power systems, each It is not possible to detect the voltage rise in the differential circuit using the optical output of the optical current transformer, or to vector synthesize the optical outputs of each optical current transformer, so it is necessary to replace the current transformer used in the past. I can't. It is also conceivable to use an optical fiber in the optical path, but in that case there is a problem that measurement errors occur due to attenuation of the light intensity due to the optical rotation of the optical fiber.

In view of the above-mentioned problems, an object of the present invention is to provide a protective relay device that can detect internal faults with high precision and perform stable protective operation without detecting external faults using optical current transformers. do.

[Means for solving problems]

The protective relay device of the present invention has the following features:
a plurality of optical current transformers arranged so that the rotation direction of the plane of polarization is the same as the direction of the magnetic field at each position; a first optical fiber that sequentially transmits light to each of the optical current transformers; A second optical fiber installed in parallel along the first optical fiber.
an optical fiber, first and second optical transmitters that input light into one ends of the first and second optical fibers, respectively, and first and second optical transmitters that each receive the light transmitted through the first and second optical fibers. first and second optical receivers;
an attenuation factor calculation unit that calculates an output ratio between the optical receiver and the second optical transmitter; and an output of a value obtained by multiplying the outputs of the first optical receiver and the first optical transmitter by the output ratio. It is configured to include an output difference calculation unit that calculates a difference, and a division unit that divides the calculated output difference by the calculated output ratio.

[Effect]

The light emitted by the first and second optical transmitters is
are incident on one end of each optical fiber. 1st, 2nd
The light incident on the optical fiber is transmitted through the optical fiber. The magnetic fields of a plurality of currents flowing into one point on the bus bar act on each optical current transformer, and due to the Faraday effect, the polarization plane rotation angle of the optical current transformer rotates in accordance with the magnetic field, that is, the current. That is, each time light passes through an optical current transformer, it is polarized. The light polarized by each optical current transformer enters the first optical receiver from the other end of the first optical fiber so as to obtain a light intensity corresponding to the rotation angle of the plane of polarization. The light incident on the second optical fiber is incident on the second optical receiver from the other end of the second optical fiber so as to obtain a light intensity corresponding to the angle of rotation of the plane of polarization due to the optical rotation of the optical fiber. Then, the output ratio between the second optical receiver and the second optical transmitter and the output difference between the outputs of the first optical transmitter and the first optical receiver multiplied by the output ratio are calculated. Then, the calculated output difference is divided by the output ratio to correct the rotation angle of the polarization plane obtained from the first optical fiber, thereby obtaining the rotation angle of the polarization plane polarized and synthesized by each optical current transformer.

This eliminates the error in the rotation angle of the polarization plane due to the optical rotation of the optical fiber, and enables highly accurate detection of busbar accidents.

〔Example〕

The present invention will be described in detail below with reference to drawings showing embodiments thereof. FIG. 1 is a configuration diagram of a protective relay device according to the present invention. In the figure, power transmission lines 5, 6, and 7 are branch-connected to a bus 1 that constitutes a power system.
Optical current transformers 21, 22, and 23 each having a built-in magneto-optical element 38, which will be described later, are located close to the power transmission lines 5, 6, and 7 near the bus line 1, respectively. It is provided.

The orientation of each optical current transformer 21, 22, and 23 is selected so that the plane of polarization rotates in the same direction with respect to the direction of the magnetic field at each installation position. The direction of the magnetic field caused by the current is matched. An optical path is formed in the first optical fiber 24 so that the light passes through each of the optical current transformers 21, 22, and 23 in sequence. One end of the first optical fiber 24 is connected to an optical transmitter 26 that includes a polarizer 28 and a light source (not shown), and the output light from the light source is linearly polarized by the polarizer 28 and then converted into the first optical fiber. The light is made incident on one end of the optical fiber 24. On the other hand, the other end of the first optical fiber 24 is connected to a first optical receiver 30 incorporating an analyzer 32 and a photoelectric conversion element (not shown).
The light that has traveled inside is incident on the first optical receiver 30 and is polarized according to the polarization plane of the analyzer 32, and the polarized light is photoelectrically converted to obtain an electrical signal corresponding to the light intensity. It's getting old. Further, a second optical fiber 25 having approximately the same length is arranged parallel to the first optical fiber 24, and both the first and second optical fibers 24, 25 have the same shape and are made of the same material. ing. One end of the second optical fiber 25 is connected to a second optical transmitter 27 containing an analyzer 29 and a light source (not shown), and the output light from the light source of the second optical transmitter 27 is transmitted to a polarizer 29. After being polarized at , the light enters one end of the second optical fiber 25 .

The other end of the second optical fiber 25 is connected to the analyzer 3.
3 and a second optical receiver 31 incorporating a photoelectric conversion element (not shown), and the light traveling through the second optical fiber 25 enters the second optical receiver 31 and is detected. The photons 33 are polarized according to the polarization plane, and the polarized light is photoelectrically converted to obtain an electrical signal corresponding to the light intensity.

The output of the first optical receiver 30 is input to the output calculation section 35, and the output of the first optical receiver 31 is inputted to the output calculation section 35.
The output of is input to the attenuation rate calculation section 34. The optical output signal of the first optical transmitter 26 is input to the output difference calculating section 35, and the signal of the optical output of the first optical transmitter 26
The optical output signal is input to the attenuation rate calculation section 34.

The attenuation rate calculation unit 34 connects the second optical receiver 31 and the second
The optical transmitter 27 calculates the output ratio of the second optical fiber 25 to obtain the attenuation rate of light within the second optical fiber 25. The output difference calculation unit 35 is input with the output ratio signal calculated by the attenuation rate calculation unit 34, and multiplies the output of the first optical transmitter 26 by the output ratio to calculate the output of the first optical receiver 30. An operation is performed to calculate the output difference between the output and the multiplied output, and the light intensity difference between one end and the other end of the first optical fiber 24 is obtained. Both the output ratio signal calculated by the attenuation rate calculation unit 34 and the output difference signal calculated by the output difference calculation unit 35 are input to the division unit 36. Division section 36
is designed to perform an operation of dividing the output difference by the output ratio, and by the division, the rotation angle of the polarization plane is obtained by correcting the rotation angle of the polarization plane due to the optical rotation of the optical fiber. The output signal _xO of the dividing unit 36 is input to the comparing unit 37, and the comparing unit 37 compares the magnitude of the input signal with a predetermined value set in advance to determine a bus accident. A protection command signal is output based on the comparison result.

Next, the current detection operation by the optical current transformer will be explained.
FIG. 2 is an explanatory diagram of the operating principle of optical current transformers 21, 22, and 23 that utilize the Faraday effect. The rotation angle φ of the polarization plane of the magneto-optical element 38 built into each optical current transformer is φ=V〓・H...(1) where V〓 is the Verdet constant of the magneto-optical element, H is the length of the magnetic field, Becomes strength.

By the way, if the facing distance between the power transmission line provided with the optical current transformer and the magneto-optical element 38 is constant, the strength H of the magnetic field is proportional to the current I flowing through the power transmission line, so φ=V〓・I ...(2), and the polarization plane rotation angle φ is proportional to the current I. Therefore, the optical current transformers 21, 22, 23 shown in FIG.
Polarization plane rotation angles φ ₁ , φ ₂ , φ ₃ corresponding to the currents I ₁ , I ₂ , I ₃ flowing through the terminals 6 and 7 are obtained. Since such a rotation angle of the polarization plane of light is caused by the magnetic field, that is, the current, detected by the optical current transformer, Kirchhoff's law holds true.

Now, if there is no fault on bus 1, the vector sum ΣI of the current flowing into bus 1 from Kirchhoff's law is ΣI=I ₁ +I ₂ +I ₃ =0...(3), and the sum of the currents is The polarization plane rotation angle Iφ is Iφ=φ ₁ +φ ₂ +φ ₃ =0...(4) However, φ ₁ , φ ₂ , φ ₃ are optical current transformers 21, 22, 2
This is the polarization plane rotation angle at 3.

However, if an accident occurs on bus 1, each transmission line 5,
The sum of currents ΣI of 6 and 7 is ΣI=I _F ...(5) However, I _F is the fault current, and the entire polarization plane rotation angle Iφ of each optical current transformer 21, 22, 23 is Iφ=φ _F ...(6), and an accident is detected based on the magnitude of the rotation angle that is the sum of the rotation angles of each plane of polarization.

For this reason, the output light from the first optical transmitter 26 is transferred to the optical current transformer 2 by the first optical fiber 24.
1, 22, and 23, the light is polarized in each optical current transformer 21, 22, and 23 by a polarization plane that rotates in the same direction with respect to the direction of the magnetic field at each installation position. and the light is transmitted to the first optical receiver 30
The light is incident on the power source, is polarized by the analyzer 32, and its light intensity is detected, resulting in a light intensity corresponding to the current obtained by combining the currents of the respective power transmission lines 5, 6, and 7.

Incidentally, the optical fiber has a slight optical rotation, which causes an error in the intensity of the received light and reduces the accuracy of detecting a busbar accident. However, in the present invention, the second optical fiber 25 is They are arranged in parallel along one optical fiber 24, and correct the intensity of the received light according to the rotation angle of the plane of polarization caused by the optical rotation of the optical fiber, thereby increasing the accuracy of detecting busbar accidents.

That is, the output lights P ₀ and P ₀ of the first and second optical transmitters 26 and 27 are linearly polarized by polarizers 28 and 29, respectively, and enter the first and second optical fibers 24 and 25, respectively.

In the second optical fiber 25, due to its length and optical rotation, on the light-receiving end side, PL'=ηPL<δ (however, η
is the attenuation rate due to transmission loss of the optical fiber, and δ is the rotation angle due to optical rotation). On the light-receiving end side of the first optical fiber 24, P ₁ '=ηP ₁ <(δ+φ) due to the polarization plane rotation angle φ caused by the alternating magnetic field. When these lights pass through the analyzers 32 and 33 separately, the inner product value corresponding to the phase of each rotation angle θ of the analyzers 32 and 33 and the polarization plane rotation angle φ becomes the optical output, and the second optical fiber 25 PL ₀ =ηP ₀ cos(θ−δ) In the first optical fiber 24, P ₁₀ =ηP ₀ cos(θ−δ−φ).

Then, the attenuation rate, that is, the output ratio ξ by the attenuation rate calculation unit 34 becomes ξ=PL ₀ /P ₀ , so ξ=ηcos(θ−δ).

Further, the output difference x by the output calculation unit 35 is x=P ₁₀ −ξP ₀ to x=ηP ₀ {cos(θ−δ±φ)−cos(θ−δ)}.

Then, dividing the output difference x by the output ratio ξ, we get x ₀ = x/ξP ₀ = cos(θ-δ±φ)-cos(θ-δ)/co
s(θ−δ)=cos(θ−δ±φ)/cos(θ−δ)−1
=cosφ〓tan(θ−δ)sinφ−1 Here, the polarization plane rotation angle θ of the analyzed light is about 45°.The rotation angle δ due to optical rotation is small and θ−δ≒45°, so tan(θ −δ)≒1, and x ₀ ≒cosφ±sinφ−1. In addition, since each rotation of the plane of polarization due to the alternating magnetic field φ is small (φ<<1), cosφ≒1, sinφ≒(rad), so x ₀ ≒cosφ〓sinφ−1≒φ(rad), and the dividing unit 36 The output obtained by this method detects the strength of the alternating magnetic field without errors due to the optical rotation of the optical fiber, that is, the true alternating current.

As a result, the decrease in light intensity caused by the optical rotation of the optical fiber itself is corrected, and the current obtained by combining the currents of the power transmission lines 5, 6, and 7 can be detected with high precision. Therefore, the output of the division section 36 is input to the comparison section 37 and compared with a predetermined value for determining an accident, and a protection command signal is output based on the comparison result. Therefore, busbar accidents can be detected with high accuracy without being affected by the optical rotation of the optical fiber.

FIG. 3 shows another embodiment of the present invention, in which the output signal of the second optical receiver 31 is input to the output control section 39, and the output signal of this output control section 39 is input to the output control section 39. The signal is applied to the first and second optical transmitters 26 and 27. By doing this, when the output of the second optical receiver 31 becomes less than a predetermined value, the output value is multiplied by a predetermined coefficient and the output is transmitted to the first and second optical transmitter 2.
The reduction in light intensity is corrected by increasing the light emission outputs of 6 and 27. The other configurations in FIG. 3 are similar to those in FIG. 1.

FIG. 4 shows still another embodiment of the present invention, in which the output of the second optical receiver 31 is monitored by the monitoring section 4.
It is entered as 0. In other words, when the output of the second optical receiver 31 falls below a predetermined value, a signal is output indicating that the accident detection operation is malfunctioning, so that malfunctions in accident detection can be monitored.

The other components in FIG. 4 are the same as those in FIG. 1.

Note that such an output control section 39 and monitoring section 4
A similar effect can be obtained by using a configuration in which the output of the first optical receiver 30 is input to the optical receiver 30.

In addition, in this example, the output of the optical receiver was treated as an analog quantity, but the output of the optical receiver was converted into a digital quantity.
It goes without saying that the same effect can be obtained even when applied to a digital protection system in which a converted digital signal is transmitted to a remote location and arithmetic operations are performed by digital arithmetic means.

〔effect〕

As detailed above, according to the present invention, there is a first optical fiber that sequentially transmits light to a plurality of optical current transformers, and a second optical fiber that simply transmits light along the first optical fiber. By arranging optical fibers in parallel, the intensity of the light transmitted through the second optical fiber is obtained, and the output ratio between the second optical receiver and the second optical transmitter is calculated. Obtain the intensity of the light that has passed through, calculate the output difference between the output of the first optical receiver and the output obtained by multiplying the output of the first optical transmitter by the output ratio, and calculate the calculated output difference. By dividing by the output ratio, the polarization plane rotation angle due to the optical rotation of the first optical fiber is corrected.

Therefore, the true light intensity polarized only by the rotation angle of the plane of polarization obtained by each of the plurality of currents flowing into one point can be obtained, and internal faults in the power system can be detected with high precision. Therefore, the present invention can provide a highly reliable protective relay device by utilizing the Faraday effect, and greatly contributes to the protection of the power system.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the protective relay device of the present invention, Figure 2 is a block diagram of the protective relay device of the present invention;
The figure is an explanatory diagram of the operating principle of an optical current transformer, Figures 3 and 4 are block diagrams of a protective relay device showing other embodiments of the present invention, and Figures 5 and 6 are conventional protective relays. FIG. 2 is a configuration diagram of an electrical device. 1... Bus bar, 5, 6, 7... Power line, 21, 2
2, 23... Optical current transformer, 24... First optical fiber, 25... Second optical fiber, 26... First optical transmitter, 27... Second optical transmitter, 30... ...First optical receiver, 31... Second optical receiver, 34...
...Attenuation rate calculation section, 35...Output difference calculation section, 36...
. . . division section, 37 . . . comparison section. In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A plurality of optical current transformers are installed at each position where the magnetic field of each of the plurality of currents flowing into one point of the power system acts, with the rotation direction of the plane of polarization being the same with respect to the direction of the respective magnetic field. , a first optical fiber that sequentially transmits light to each of the optical current transformers; a second optical fiber arranged in parallel along the first optical fiber;
and a first for injecting light into one end of the second optical fiber.
and a second optical transmitter, first and second optical receivers that separately receive the light transmitted through the optical fibers at the other ends of the first and second optical fibers, and a second optical fiber. an attenuation rate calculation unit that calculates an output ratio between the receiver and the second optical transmitter; and an output ratio calculated by the attenuation rate calculation unit between the output of the first optical receiver and the output of the first optical transmitter. A protective relay device comprising: an output difference calculation unit that calculates an output difference with a value multiplied by the output ratio; and a division unit that divides the output difference by the output ratio.