JPH0150167B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a display line protection relay system, and in particular has a highly sensitive ratio differential characteristic that compensates for the influence of line constants that are distributed over the display line. The present invention also relates to a display line protection relay device that reduces the number of display lines used.

[Background of the invention]

The basic configuration of the conventional display line protection relay system is the first
As shown in the figure, current is introduced from the current transformers CTA and CTB installed at both ends of the transmission line to be protected, and current information at both ends is exchanged through the display line PW. This system detects internal accidents. Note that A and B are busbars, and CBA and CBB are beams and disconnectors. Various types of display line protection relay systems have been proposed in the past, and in order to explain the problems of these conventional systems, the principle of a typical example will be explained.

FIG. 2 is a diagram explaining the principle of a typical example. In this example, the display line relay has a built-in base resistor R _b and a balance resistor _Rs , which are connected through the display line (the one-way resistance of the display line is R _p ) as shown in FIG. 2. Here, the balance resistor R _s is a variable resistor, and if both ends are set so that R _p + P _s + R _b (1), the secondary currents i _A and i _B of each end CT are R The current will be divided into _{the s} circuit and the R _b circuit at a ratio of 1:3.

In the figure, the current arrow indicates the current direction, and each CT is configured to generate a CT secondary current in the direction shown in response to the inflow currents i _pA and i _pB at the time of an internal fault in the transmission line protection section. has been done. Therefore, the currents flowing through R _b and R _s of the A terminal and R _b and R _s of the B terminal are respectively defined as i _Ab , i _As , i _Bb , i _Bs with the direction of the inflow current of the own terminal being positive. Then, for the transmission line internal fault currents i _pA and i _pB , i _Ab = 3/4i _A + 1/4i _B ………(2) i _As = 1/4i _A −1/4i _B ………(3) i _Bb = 3/4i _B + 1/4i _A (4) i _Bs = 1/4i _A - 1/4i _B (5).

Here, the operating current of the display line relay is I _O ,
The difference between the currents flowing through R _b and R _s , i.e. (i _Ab −i _As )
and (i _Bb −i _Bs ), and assuming that the suppression current is I _R and the current flowing through R _s is derived, for the A-terminal relay, I _O (i _Ab −i _As ) = 1/2 (i _A + i _B ) ………(6) I _R = i _As = 1/4 (i _A − i _B ) ………(7) For the B-terminal relay, I _O = (i _Bb − i _Bs ) = 1 /2 (i _A + i _B ) ......(8) I _R = i _Bs = 1/4 (i _B - i _A ) ......(9).

Based on the above principle, if the fault is inside the protected area, the fault current will flow from both ends or one end, so I _O ≫ I _R , and if the operating amount I _O is equal to the suppression amount I _R , the operation will be performed reliably. do. On the other hand, in the case of a fault outside the protected area, the fault current simply passes through.
i _A = -i _B , and even if the error of the current transformers at both ends is taken into account, I _O << I _R , and once the amount of suppression is exceeded, it will no longer operate properly.

The above principle can also be applied to a three-terminal system, an example of which is shown in FIG. In this case, the security section A,
Let the reciprocating resistances from B and C to the branch ends of the display line be R _pA , R _pB , and R _PC , respectively, and the balance resistance R _S explained in Figure 2 for the A, B, and S ends should be considered as follows. Settling.

R _b = R _sA + R _pA ………(10) R _b = R _sB + R _pB ………(11) R _b = R _sC + R _pC ………(12) When setting as above, the Operation amount I ₀ ,
The amount of suppression I _R is _IO = 1/3 (i _A + i _B + i _C ) (13) I _R = 1/6 (2i _A −i _B −i _C ) at the A terminal with respect to the passing current. ………(14) At the B end, I _O = 1/3 (i _A + i _B + i _C ) ……… (15) I _R = 1/6 (2i _B −i _C −i _A ) ………(16 ) At the C end, I _O = 1/3 (i _A + i _B + i _C ) ...... (17) I _R = 1/6 (2i _C - i _A - i _B ) ...... (18), and there are two terminals. It can be seen that it can be applied in the same way as in the case of .

However, when applied to a three-terminal system, equation (13) ~
As shown in (18), the operating amount I ₀ is the same at each end, but
Since the suppression amounts I _R are not the same, the following problems arise in application.

That is, as shown in Figure 4a, one end inflow (A
In the case of one end flowing out (C end) and one end having no current (B end), the amount of suppression at the B end, which is the no current end, is smaller than the other end (I _R equations (14), (16) , in (18),
At the A and C ends, i _B = 0, while at the B end, 2i _B =
It becomes 0. ), the ratio differential characteristics do not match at all ends, and the operating range of the ratio differential characteristics at the A and C ends becomes narrower than that at the B end as shown in FIG. Also, the fifth
As shown in figure a, two ends inflow (AC end), one end outflow (B
In the example of the end), contrary to the example of FIG. 4, the suppression amount I _R at the B end is larger than the other end, as shown in FIG. 5b,
The operating range of the ratio differential characteristic at the B end becomes narrower.

As explained above, when the conventional method is applied to a three-terminal system, the ratio differential characteristics at each end are uneven depending on the fault current condition, and the operating range on the ratio differential characteristics becomes narrow. In many cases, sufficient protection performance cannot be ensured. Furthermore, in the case of a 3-terminal system with 3 lines as shown in Figure 6, and some ends are out of service, the current flowing out from the branch end (B end) in the middle of an internal fault increases, and the conditions become synergistically severe. As a result, there are cases where the system becomes inoperable due to an internal accident.

Furthermore, although the current flowing through the display line is adjusted by the base resistor R _b and the balance resistor R _s , the detection performance deteriorates when the display line becomes long and line constants other than the resistance cannot be ignored. A method of adding the same characteristic impedance as the display line instead of the base resistance, taking into account the compensation of line constants (e.g. Japanese Patent Application Laid-Open No. 1987-50
-151347), but because it deals with circuit configurations that include display lines, there are multiple mounting methods for dielectric strength and multi-terminal systems (for example, the constant of the display line may differ from the branch point). be.

[Purpose of the invention]

In view of the above, it is an object of the present invention to provide a display protection relay system that can correctly derive the other end current at each terminal and match the performance.

[Summary of the invention]

In order to ensure the protection of multi-terminal branched power transmission lines, the present invention uses a pair of display wires between each two opposing terminals to transmit current signals transmitted by display wires. As a means of extracting only the information of the other terminal from the transmitted signal, a compensation circuit with simulated line constants of the transmission display line is provided, and the passing current signal of each terminal is independently and faithfully derived, and the ratio differential characteristic is This provides a display line protection relay system using current differential relays.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to FIG. The figure targets transmission line protection for a two-terminal system, but even if a multi-terminal branch power transmission line is protected, the number of opposing terminals will only increase, and it will basically be an application of Figure 7. Therefore, the explanation will be simplified using a two-terminal system.

The symbols and operation details in FIG. 7 will be described below. 1 is the power transmission line to be protected, CBA, CBB
Use chopsticks or disconnectors to connect the A terminal side to CBA and the B terminal side to CBA.
Indicated by CBB. CTA and CTB are current transformers,
CTA is the transmission line passing current waveform at terminal A, and CTB
is a relay device that protects the transmission line current waveform at terminal B.
Used for input to RYA and RYB.
The output current of CTA is denoted by i _A and the output current of CTB is denoted by i _B. As already mentioned, the polarities of i _A and i _B are set to be positive based on the internal fault current when currents i _pA and i _pB of the same phase flow in. CT1A, CT2A, CT1B,
Each CT2B is an auxiliary current generator and a kind of isolation transformer.

In addition, regarding the contents of RYA and RYB, in order to explain the operation of the A terminal as a representative example,
The contents of terminal RYB will be omitted as appropriate. P.W.
is a display line and is a transmission line for transmitting signals of i _A and i _B to each other. γ, L, G, and C shown in PW are
Distribution constant of PW, resistance per unit Km, respectively
Symbols representing inductance, conductance, and capacitance. R is a terminating resistor. _ITr is an isolation transformer for insulating the display line PW and the protective relay device RY. Current transformer CT1A with both terminals,
The impedance seen from CT1B to each other terminal is configured to be symmetrical, and a value i _A2 i _B2 proportional to the signals of i _A and i _B is set to each protective relay device RY terminal by a pair of display lines PW. Send each other from However, the distribution constants γ, L, G of the display line PW,
Due to the influence of C, the signals that reach the respective terminals become i _A3 and i _B3 , and signals proportional to i _A and i _B , respectively, are energized to the terminal terminal resistance R of the terminal. Note that all current transformers will be explained as ideal current sources.

By the way, in the protective relay devices RYA and RYB, the i _A and i _B signals are equivalently extracted as independent values, and, for example, the well-known ratio differential characteristic by scalar sum suppression |i _A +i _B |- K _R (｜i _A ｜＋｜i _B ｜)＞K _s
The aim is to make a judgment that satisfies (19). However, K _R is a suppression coefficient, and K _s is a level judgment integer value. However, when looking at the protective relay device RYA at the A end, the current passing through the terminating resistor R is i _A1 and i _B3
So, i _A1 is a value proportional to own terminal input signal i _A , i _A1 = i _A
−i _A2 . The same is true for RYB, and the currents flowing through its terminal resistor R are i _B1 and i _A3 , i _B1 = i _B −
i _B2 . In this way, originally i _A and i _B or i _A1
and i _B1 or i _A3 and i _B3 should be compared, but in conventional display line protection relay devices, the determination using equation (19) is made using different combinations of signals. Here, each signal can be defined as follows.

i _A1 =K ₁ i _A i _A2 =K ₂ i _A i _A3 =K ₃ i _A i _B1 =K ₁ i _B i _B2 =K ₂ i _B i _B3 =K ₃ i _B ……(20) However, K ₁ , K ₂ , and K ₃ are each proportionality constants,
It has the content of a complex number. As is clear from this, among the signals obtained at the A terminal, the value proportional to the B terminal current i _B is i _B3 , and in order to extract only this, the current passing through the terminal resistor R of the A terminal must be Just subtract i _A1 from i _A1 + i _B3 . To do this, we need to know the value of i _A1 . Since i _A1 changes depending on the influence of the distribution constant of the display line PW, it is necessary to calculate it including the terminating resistance R and the distribution constant. In the present invention,
A simulation circuit is provided that simulates the distribution constant of the display line PW and applies a self-terminal current.

In RYA, CT2A is an auxiliary current transformer used for a simulated circuit, Z _AB is a simulated line constant of PW, and R is a terminating resistor. Z _AB is determined according to the length of PW, and for simplification, it can be a T-type equivalent circuit consisting of a resistor and a capacitor, or a π-type equivalent circuit. A self-end current i _A is applied from CT2A to Z _AB , and as a _result , values i _{A1 ′} , i _{A2 ′} ,
i _A3 ′ can be obtained without including the i _B term. Therefore, from the secondary side signals of CT1A and CT2A,
By using the difference circuit D _A , a value corresponding to i _B3 = i _A1 + i _B3 − i _A1 ′ (21) can be obtained. Also, CT2
Since i _A3 ′ of A is equivalent to i _A3 generated by CT1A, by i _B3 and i _A3 ′ obtained from equation (21),
It is possible to make a determination with ratio characteristics equivalent to equation (19) using signals proportional to i _B and i _A.

In other words, i _B3 = K ₃ i _B i _A3 ′=K ₃ i _A (22), the operating condition of the protective relay device RYA is |A _A3 ′+i _B3 | −K _R (|i _A3 ′|+ ｜i _R3 ｜)＞K _s ………(23) Then, ｜i _A +i _B ｜−K _R (｜i _A ｜+｜i _B ｜)＞ ^Ks _K3 ……( ₂₄ ) By correcting by division by a constant K ₃ , a determination formula equivalent to formula (19) can be obtained.
DT _A in FIG. 7 is an arithmetic unit corresponding to equation (24).
The arithmetic unit of DT _A may decide whether or not to output an operation output based on the result of calculating the instantaneous values of i _A and i _{B ;}
It is also possible to determine i _B using an amount corresponding to an effective value and a vector amount that takes into account the phase angle. Also, RYB is similar to RYA, with D _A and RYA respectively.
It has arithmetic units D _B and DT _B corresponding to DT _A. In addition, as an example of the present invention, a two-terminal system is shown in which an internal accident is determined at each terminal, but at least one terminal is determined, and depending on the result, an internal accident is determined at the other terminal. It can also be applied to a protection method that sends a forwarding and disconnection command.

In addition, when protecting not only two-terminal systems but also multi-terminal branch transmission lines with three or more terminals, current information at each opposing end can be obtained between opposing ends according to the content explained in Figure 7. Therefore, a ratio differential relay for a multi-terminal system can be realized.

However, in a multi-terminal system, there are multiple opposing ends, and the display line PW to each opposing end
Since the length of the
In order to match the PW constants to the length of the longest opposing end, additional line constants are connected to PW, and the circuit corresponding to the simulated line constant Z _AB is connected to the longest opposite end.
Each opposing line constant may be added to match PW.

FIG. 8 shows an embodiment in a three-terminal configuration. The symbols in this figure that are the same as those in FIG. 7 indicate equivalents. In the figure, Z _PAB , Z _pAC , and Z _pBC are the line constants of the display line PW between terminals A and B, between terminals A and C, and between terminals B and C, respectively, and Z _pAB ′, Z _pAC ′,
Z _pBC ′ is the line constant compensation circuit for each of the above sections so that the line constant of PW becomes Z _pAB + Z _pAB ′ = Z _pAC + Z _pAC ′ = Z _pBC + Z _pBC ′ = Z _p (25) It is for adjustment. However, Z _p is a line constant simulation circuit similar to Z _AB in FIG.

To explain the operation of this circuit in Fig. 8 using the A-terminal protective relay device RYA as an example, the current i _B3 taken into RYA from the B-terminal via the isolation transformer _I.Tr and the current transformer C. The A-end current i _A1 from T·1A is combined to obtain current i _A1 +B _B3 . Further, the current i _C3 taken into the RYA from the C terminal via the isolation transformer _I.Tr and the current from the current transformer CT2A are combined to obtain the current i _A1 +i _C3 . On the other hand, the parallel circuit between the line constant simulation circuit Z _p and the terminating resistor R is a current transformer.
An A-terminal current _iA is applied via CT3A.
Here, the line constants Z _pAB , Z _pAC and the compensation constant
Since Z' _pAB , Z' _pAC and the simulated constant Z _p are selected so that the relationship of equation (25) holds, the current i' _A1 flowing through the termination resistor R1 is equal to i in the composite current. Equal to _A1 . The current i′ _A3 flowing through the terminating resistor R2 is equal to the current value i _A3 when the own end current i _A is received by the other end via the display line PW. The difference circuits DA1 and DA2 derive the difference between i _A1 +i _B3 and i' _A1 and the difference between i _A1 + i _C3 and i' _A1 , respectively, to obtain i _B3 and i _C3 . The three sets of currents i' _A3 , i _B3 , and i _C3 input to the calculation unit D _A are all "signals equivalent to the signals received at the other end via the display line PW." B-end and C-end protection relay device RYB and
In RYC, the same processing as that at the A terminal described above is performed to derive "a signal equivalent to the signal received at the other end" for each terminal current. Therefore, by performing ratio differential calculation in the calculation unit DT at each end, the operating characteristics of each end can be made to match, and the display line protection relay system is suitable for application to multi-terminals of three or more terminal systems. can.

The present invention can also be realized in the following manner. In the embodiment shown in Figure 8, the protective relay device RY at each end is equipped with a circuit that simulates the line constant, but this is only applied to one terminal (terminal A in the example) as shown in Figure 9. Protective relay device with the same configuration as Figure 8
It is also possible to use a method (transfer trip method) in which an RY is provided and a final judgment signal regarding the disconnection tripping is sent to the other end.

Furthermore, in this embodiment, a detection method focusing on the current signal passing through the terminating resistor is shown, but in FIG. 10, the signals sent to the PW of each terminal, i _A2 , i _B3 ,
and i′ _A2 of the simulated circuit to find i _B3 = i _A2 + i _B3 − i′ _A2 (26), and perform the ratio calculation corresponding to equation (19) with i _B3 and i′ _A3 . Good too.

In addition to simply scalar sum suppression, since the current at each terminal is obtained as independent information, it is also possible to compare the phase of each terminal current, use a maximum current suppression method, and identify non-power terminals, etc. It is also possible to identify the distribution of , which widens the range of applications for accident detection.

Furthermore, the line constant simulating circuit for Z′ _pAB , Z′ _pAC , and Z _p shown in equation (25) does not necessarily simulate the distributed constants accurately; It may be implemented using a T-type circuit using capacitance or the like, or an approximate constant circuit such as a π-type circuit.

〔Effect of the invention〕

As described above, a multi-terminal branch power transmission line can be protected by a device having a ratio characteristic using one pair of display lines per opposing terminal.

Further, the adjustment of the device can be performed for each pair of opposing terminals that transmit signals, which simplifies the adjustment work and improves the accuracy of adjustment.

In addition, the number of display lines is small, which has an economical effect, and since each terminal current film is detected individually, it has the effect of enabling high-sensitivity setting.

[Brief explanation of drawings]

Figure 1 is a basic configuration diagram of the display line relay device, Figure 2 is an explanatory diagram of a conventional 2-terminal configuration, Figure 3 is an explanatory diagram of a conventional 3-terminal configuration, and Figures 4 and 5 are conventional diagrams. Fig. 6 is a diagram showing an example of dividing fault current inside a 3-terminal system, Fig. 7 is an example of the present invention, and Figs. 8 and 9 are examples of applying the present invention to a 3-terminal system. FIG. 10 is a diagram of another embodiment. CT...Current transformer, PW...Display line, RY...Protective relay device, R...Terminal resistor, DA...Difference circuit, Z _P
...Line constant simulation circuit, DT...Arithmetic circuit.

Claims (1)

[Claims] 1. A two-terminal power transmission line, a current transformer provided at each terminal of a two-terminal power transmission line to detect passing current, and a current transformer provided for each terminal to detect the secondary current thereof. a first auxiliary current transformer that receives as input, an indicator wire connected between the secondary windings of the first auxiliary current transformer at each terminal, and a secondary winding of the first auxiliary current transformer of the indicator wires. terminating resistors for the display lines provided in parallel on the line side, a second auxiliary current transformer provided for each current transformer at each terminal and receiving the secondary current of the current transformer at its own end; a simulating circuit connected to the secondary winding of the second auxiliary current transformer and simulating the impedance of the display line; a simulating circuit provided between the secondary winding of the second auxiliary current transformer and the simulating circuit; A terminating resistor for the own terminal, a terminating resistor for the other terminal installed on the opposite side of the terminating resistor for the own terminal across the simulated circuit, and a terminating resistor for the other terminal installed for each terminal of the power transmission line, Find the difference current between the current flowing through the terminating resistor at the end and the current flowing through the terminating resistor for the own terminal of the simulated circuit at the own end, and use this difference current and the current flowing through the terminating resistor for the other terminal of the simulated circuit at the own end. An indicator line protection relay device comprising an arithmetic circuit that detects an accident on the power transmission line by differential arithmetic operation. 2. In the display line protection relay device according to claim 1, instead of the differential current used in the arithmetic circuit, a current flowing toward the display line side from the own end of the display line or the terminating resistor of the specific terminal. A display line protection relay device characterized by using a difference current between the current flowing into the simulated circuit of its own end or a specific terminal. 3. A power transmission line with n terminals (n≧3), a current transformer installed at each terminal of the transmission line to detect the passing current, and a current transformer installed at each terminal, whose secondary current is input. A first auxiliary current transformer, n sets of display wires connected between the secondary winding of the first auxiliary current transformer and the secondary winding of the first auxiliary current transformer at the opposite end, n sets of display lines in which impedance of each display line is made equal; a terminating resistor for the display lines provided in parallel on the secondary winding side of the first auxiliary current transformer of the n sets of display lines; and each terminal. A second auxiliary current transformer is provided for each current transformer, and receives the secondary current of the current transformer at its own end, and is connected to the secondary winding of the second auxiliary current transformer, and A simulated circuit that simulates the impedance of the line, a terminating resistor for the own terminal of the simulated circuit provided between the secondary winding of the second auxiliary current transformer and the simulated circuit, and a terminal resistor for the own terminal of the simulated circuit provided between the secondary winding of the second auxiliary current transformer and the simulated circuit; A terminating resistor for a mating terminal installed at a position opposite to the terminating resistor, a terminating resistor for the own end of the (n-1) set of display wires provided for each terminal of the power transmission line and connected to the own end. The difference current between the (n-1) flowing currents and the current flowing through the terminal resistor of the simulation circuit at the own end is calculated, and the difference current between the (n-1) currents and the current flowing through the terminal resistor of the simulation circuit at the own end is calculated. An indicator line protection relay device comprising an arithmetic circuit that detects an accident in the power transmission line by differential calculation using a current flowing through a terminating resistor for a mating terminal. 4. In the display line protection relay device according to claim 3, instead of the differential current used in the arithmetic circuit, a current flowing toward the display line side from the own end of the display line or the terminating resistor of the specific terminal. A display line protection relay device characterized by using a difference current between the current flowing into the simulated circuit of its own end or a specific terminal. 5. A power transmission line with n terminals (n≧3), a current transformer installed at each terminal of the transmission line to detect the passing current, and a current transformer installed at each terminal, whose secondary current is input. The secondary winding of the first auxiliary current transformer at a specific terminal of the first auxiliary current transformer and the first terminal at the other end.
connected between the secondary windings of the auxiliary current transformer (n-
1) (n-1) sets of display lines in which the impedance of each display line is made equal; and a first auxiliary current transformer secondary winding of the (n-1) sets of display lines. terminating resistors for display lines installed in parallel on the line side,
a second auxiliary current transformer inputting the secondary current of the current transformer of the specific terminal; a simulating circuit connected to the secondary winding of the second auxiliary current transformer and simulating the impedance of the display line; , a terminating resistor for the own terminal of the simulated circuit provided between the secondary winding of the second auxiliary current transformer and the simulated circuit, and a terminating resistor for the own terminal of the simulated circuit provided at a position opposite to the terminating resistor for the own terminal across the simulated circuit; The installed terminating resistor for the other terminal is provided only at the specific terminal of the power transmission line, and the (n-1) number of terminals flowing through the terminating resistor at the own end of the (n-1) set of display wires connected to the specific terminal. The difference current between the current and the current flowing through the terminating resistor for the own terminal of the simulated circuit is determined, and the (n-1) difference currents and the current flowing through the terminating resistor for the other terminal of the simulated circuit are used. A display line protection relay device comprising an arithmetic circuit that detects an accident on the power transmission line by differential arithmetic operation, and a transmission means that transmits the arithmetic result of the arithmetic circuit to the other end. 6. In the display line protection relay device according to claim 5, instead of the differential current used in the arithmetic circuit, a current flowing toward the display line side from the own end of the display line or the terminating resistor of the specific terminal. A display line protection relay device characterized by using a difference current between the current flowing into the simulated circuit at its own end or a specific terminal.