JPS6364135B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an indicator line protection relay system, which has ratio differential characteristics suitable for application to multi-terminal power transmission lines in particular, and which aims to reduce the number of indicator lines used. Regarding the relay method.

The basic configuration of the display line protection relay system, as shown in Figure 1, is to introduce current from current transformers CTA and CTB installed at both ends of the transmission line to be protected, and to transmit current information at both ends through display line PW. internal fault detection is performed comprehensively using indicator wire relays RYA and RYB. 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 incorporates a 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 _Rs is a variable resistor, and if both ends are set so that R _p + _Rs = R _b (1), the secondary currents i _A and i _B of each end CT are respectively The current is divided into the R _s circuit and the R _b circuit at a ratio of 1:3.

In the figure, the CT secondary current arrow indicates the current direction, and each CT is configured to generate a CT secondary current in the direction shown in the diagram in response to an external fault or normal passing current in the transmission line protection section. ing.
Therefore, if the currents flowing through R _b and R _s at the A end and R _b and R _s at the B end are respectively i _Ab , i _As , i _Bb , and i _Bs , then when the current passes through the transmission line, 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, assuming the operating current of the display line relay as I ₀ ,
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, A-terminal relay I ₀ = (i _Ab −i _As ) = 1/2 (i _A + i _B ) ...(6) I _R = i _As = 1/4 (i _A - i _B ) ... (7) B-end relay I ₀ = (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 ₀ ≫ I _R , and if the operating amount I ₀ 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 ₀ << 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, protected area A,
Let the reciprocating resistance from B and C to the branch end of the display line be R _pA , R _pB , and R _pC , respectively, and set the balance resistance R _s explained in Figure 2 as follows for ends A, B, and C. Settling.

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

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) , (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 compared to 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 three-terminal system with a three-line configuration as shown in Figure 6, the current flowing out from the branch end (terminal B) in the middle of an internal fault increases, and the conditions become synergistically severe, making it difficult to prevent an internal fault from occurring. There will be cases where it will work.

In order to solve the problems of the conventional method described above, the present invention transmits the current conditions at each end using the minimum necessary number of display lines, and extracts the current at the other end at each end. The terminal current conditions are derived independently to achieve ratio differential characteristics that are optimal for protecting multi-terminal systems. The details of the present invention will be explained below.

FIG. 7 shows a basic configuration example in which the present invention is applied to a three-terminal system. Here, the configuration is such that three terminals are combined with two terminals facing each other. Also, the base resistance
R _b and balance resistance R _s are adjusted based on equation (1). To explain the details of the present invention regarding the A end, first, transformers T ₁ , T ₄ and T ₇ perform insulation processing and self-end current derivation processing for two terminals facing each other. In addition, the opposite display line circuit with the B end
By the transformers T ₂ and T ₃ (described later in Fig. 9, resistance voltage division is also possible), the self-end current 〓 I _A ′ and the display line circulating current 1/4 (I 〓 _A ′−I 〓 _B ′) 1 of the other end (B end) by taking out, exchanging levels, and calculating the difference.
A current i _B proportional to the next current can be extracted. Similarly, by facing the C end, transformers T ₅ and T ₆ ,
i Derive _C.

By the above method, the self-terminal current at the A terminal is
i _A and the other end currents i _B and i _C can be derived independently.
Furthermore, in the example of opposing ends between A and B, as explained above, the B end current for the A end is
i _B transmission, can be used as an independent extraction means, and also B
Regarding the end, the current _iA at the A end is used as a means for transmission and independent extraction.

In this way, if the current conditions at each end can be derived independently, the amount of operation for all ends I ₀ = |i _A +i _B +i _C | ...(19) The amount of suppression I _R = |i _A |+|i _B | ＋｜i _C ｜
...(20) Operation determination formula I ₀ −kI _R K ...(21) (where k: suppression coefficient, K: sensitivity constant), obtain the so-called ideal ratio differential characteristic as shown in Figure 8. Unlike the conventional method, this characteristic does not become uneven with respect to current conditions, and by appropriately selecting the suppression coefficient k and the sensitivity constant K, the necessary ratio characteristic can be obtained. Furthermore, the display line can also be used as a means for transmitting current at one end to the other end and from the other end to the other end, so that the display line can be used effectively.

FIG. 9 shows a specific embodiment (for one terminal) according to the present invention. First, the self-terminal current I _A is input to the input terminal C1,
It is introduced from C2, and the transformers T _A , T _B , and T _C perform self-end current derivation, insulation treatment for two terminals facing each other, and level conversion. Also, R _BB , R _BC , R _sB ,
R _sC are the base resistance and balance resistance in the opposing circuits to the B and C ends, respectively. Further, the circulating current of the display line (corresponding to 1/4 ( _I〓A' - _I〓B ') of Fig. 7) is derived using the base conversions _{RBB and RsC} . Furthermore, the necessary self-end current is derived from the voltage dividing resistors R _AB , R _AC , and R _A . Adders 2B and 2C calculate currents i B _and i _C at the opposite ends B and C from the display line circulating current and self-end current derived from each of these resistances, respectively.
Current at each end of the protection zone obtained as above
For i _A , i _B , and i _C , the vector addition circuit 3 and the scalar addition circuit 4 calculate the operation amount I _0p and the suppression amount I _Rl shown in equations (19) and (20), respectively, and the determination circuit 5 calculates The operation judgment shown in equation (21) is performed and an operation output is output from the output terminal 6.

As explained above, according to the present invention, unlike the conventional system, the current conditions do not become uneven, and it is possible to obtain ratio differential characteristics that are optimal for protecting a multi-terminal system. In addition, the display wires serving as current information exchange means can be used in pairs to transmit current at one end to the other end and to transmit current at the other end to the other end, allowing efficient application of the display wires. In the above explanation, the use as a protective relay device is shown, but it goes without saying that it can also be used as a signal transmission device that transmits the analog value from the other end to the own end and outputs or displays it. .

[Brief explanation of drawings]

Figure 1 is a diagram to explain the basic configuration of the display line relay system, Figure 2 is a diagram to explain the principle of the conventional system, and Figure 3 is an explanatory diagram when the conventional system is applied to a three-terminal system. , FIGS. 4 and 5 are ratio differential characteristics for explaining the problems of the conventional method, FIG. 6 is the system configuration for explaining the problems of the conventional method, and FIG. 7 is a diagram explaining the principle of the present invention. FIG. 8 is a ratio differential characteristic diagram that can be realized by the present invention, and FIG. 9 is a specific embodiment of the present invention. CTA...Current transformer at the A end, CTB...Current transformer at the B end, CBA...Cut breaker at the A end, CBB...Cut breaker at the B end, RYA...Display line at the A end Relay, RYB
...Display wire relay at B end, PW...Display wire, T ₁ ~
T ₇ ... Transformer, C ₁ , C ₂ ... Current input terminal, T _A ,
T _B , T _C ... Transformer, R _BA , R _BB , R _BC ... Base resistance, R _sA , R _sB , R _sC ... Balance resistance, R _A ,
R _AB , R _AC ...Voltage dividing resistor, 2B, 2C... Addition circuit, 3... Vector addition circuit, 4... Scalar addition circuit, 5... Operation determination circuit, 6... Operation output terminal.

Claims (1)

[Claims] 1. In an indicator line protection relay system for an n-terminal power transmission line (n>2) branched from a part of the transmission line, n sets of independent indicator lines are arranged between all two terminals, A composite current of the current detected at the two terminals is circulated through these display lines, and at each terminal, the other end current is derived from the circulating current of each display line and the own end current, and the own end current and this other end current are derived from the circulating current of each display line and the own end current. An indicator line protection relay system that protects power transmission lines from terminal currents.