JPS5923167B2 - Digital protective relay device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital protection relay device that protects power transmission lines based on digital values.

A digital protective relay device that transmits the current and voltage values that are calibrated at the same time at electrical stations at both ends of a power transmission line through a microwave line, etc., and performs current differential or phase comparison at each terminal to protect power transmission lines. has already been proposed.

Conventionally, the equipment in this building has made protection decisions by extracting only the fundamental wave component of voltage and current through an analog filter, performing A/D conversion, and then executing the above-mentioned current differential and phase comparison calculations.

In this conventional method, as mentioned above, it is assumed that the input to the protective relay device is a fundamental wave component, and that the transmission line is a lumped constant circuit that mainly uses line inductance and resistance. Therefore, when a system fault occurs or a transient phenomenon occurs due to the operation of a switch, the protective relay device often malfunctions or malfunctions.

In order to avoid such a situation, conventional protective relay devices are provided with a custom-made time limit to prevent the protective relay device from malfunctioning.

This also creates the undesirable situation of prolonging the operating time of the protective relay device.

The present inventors abandoned the above-mentioned assumptions of conventional devices, always introduced values obtained by sampling the original waveforms of current and voltage, and realized the overhead power transmission line with a distributed constant circuit. A method for overcoming all the drawbacks of conventional devices was first invented and has already been proposed in Japanese Patent Application No. 52-84421 (Japanese Patent Laid-Open No. 54-19145).

Figure 1 shows an overhead power transmission line for deriving the basic principle of this proposed method. In Figure 1, pa, pb, and pc are the bus lines Qa of each phase of a, b, and c at terminal P.

Qb and QC represent the busbars of the a, b, and c phases at the terminal Q.

That is, according to the theory of distributed constant circuits, the three-phase voltage and three-phase current at any point on the power transmission line satisfy the following differential equation.

In reality, the old [20] can be used, so from now on we will deal with equation (3) instead of equation (2).

Here.

R/ is the self-resistance per unit length Rrr, / is the mutual resistance per unit length L s/ C is the self-inductance per unit length “rr/
is the mutual inductance per unit length C5/ is the ground capacitance per unit length Cml is the line capacitance per unit length 3-phase voltage and 3-phase current.

In a lossless transmission line, the resistance can be ignored and set to (,R)20, but in the proposal, since the target is a transmission line where the resistance cannot be ignored, it is treated as LR)\0.

Next, the mode conversion given by equation (4) is applied to the phase current and phase voltage.

Le, 1-Ls) [f) [1)=C8) [j) ...
...(4) Lf) is the mode voltage, [j] is the mode current,
[S] is a transformation matrix.

By the above conversion, equations (1) and (3) become (6), (
7) It becomes the formula.

At this time, (S)'CR) [8), [8)'LL) [8
).

(S)″(,C)(S) are the following diagonal matrices.

As is clear from equations (6) to (10), the above conversion eliminates the relationship between different modes for the mode voltage and mode current given by equation (5), and a relational expression independent of each mode is obtained. become.

Now, Fig. 2 shows a model in which distributed resistance (,5)-1LR) [8) is replaced with concentrated resistance at the midpoint of the power transmission line and at both terminals with equal constraints.

That is, let d be the transmission line length.

RO-(R3l+2Rrr/)・d mode O anti-anti・
・−・01) R'=”−”(Rs'−Rm'd mode 1 resistance −・・−・(12+), each with 1/2 at the midpoint of the transmission line and 1/4 at both terminals. That's what people do.

As a result, a power transmission line in the mode region is represented by a series connection of a lossless distributed constant circuit and a lumped resistor.

Next, a relational expression that holds true regarding the mode quantities of both terminals P and Q in FIG. 2 is derived as follows.

For simplicity, mode 1 will be described with reference to FIG. 3, but other modes can be similarly determined.

In the figure, (X2, X3. f2. f3. f,, f
5) represents the voltage at point X of the power transmission line.

In (X2'-X3).

In (X4-XS), In (X, ~X2), - In (X3-X4), In (pl-x2).

In (Ql~XS).

holds true.

By eliminating quantities other than the p 1 and Ql ends from equations (13) to (2), the following equation (22) is obtained.

Here, Zl Equation (22) always holds true unless there is an accident inside the power transmission line.

Therefore, let the right side of equation (22) be ε, and it can be determined that there is no accident when ε=0, and that there is an accident when ε\O.

The relational expressions for mode O and mode 2 are also obtained in the above manner.

When expressions related to all modes are expressed in a matrix, equation (24) is a relational expression in the mode domain, so it is returned to the phase domain.

The amount of phase region [ε (t)] corresponds to the amount of mode region [ε (t)]
ξ(t)], then similarly to equation (4), [ξ(t))=
Since [S)[ε (t)], from the left to equation (24), [
S] and (,f)-C8:r 1Le),
By substituting (j, 1=S)Li), a relational expression for the phase region can be obtained.

(ξp(t)) − [S) (theory (t)] Because it is, becomes.

Tatashi [D] = It is □.

Also, from equation (25), τ1 - τ2, so (27)
The second and third terms on the right side of the equation are obtained.

Here [I] = It is.

Similarly, the other terms on the right side of equation (27) are deformed, and the following relational expression for the phase region is obtained.

Here.

is each phase current at P end at time 1 It is.

The right side of equation (28) will be zero unless there is an accident inside the transmission line.

That is, the invariant ε in the mode domain derived from equation (24)
In order to express (1) in terms of voltage and current in each phase region (a phase, b phase, and c phase) that can actually be measured, the mode region → phase region is converted into equation (28). Therefore, the right side of equation (28) By calculating: = 0 → phase b is healthy\0 → phase b has an internal accident 20 → phase C is healthy\0 → internal accident exists for Cth phase, and an internal accident can be determined for each phase.

Now, based on the implementation results of the existing proposals by the present inventors, it has been confirmed that the previous proposal is superior as a digital protective relay device that can use the original current and voltage waveforms as they are, and by improving the existing proposals, It has been found that a more practical device can be provided.

First, as is clear from equation (28), a large number of measured values are required for a device installed, for example, at the a phase of terminal P to calculate ξ and (t).

Furthermore, τ0 and τ1 are close values (for example, the latter is 90% of the former)
Therefore, if it were to accurately detect the propagation of both, the device would be complicated and costly.

According to equation (28), time (1+τ0) and time (1+τ
Looking at the coefficients of the terms including the current value and voltage value sampled at 0), it can be seen that the signs are opposite and the magnitudes are equal.

Furthermore, looking at the coefficients of the terms including the zero-sequence current and zero-sequence voltage sampled at time t, since ho and hl are equal to zo, they are very small compared to other terms.

Therefore, in the previously proposed device that directly calculates equation (28),
ξ(t)], it is complicated and costly.

This invention is based on τ0=τ1, zO==z 1 , R
By setting O:l:R1, this was done with the aim of eliminating the expense and complexity of the previously proposed devices.

In equation (28), τ0 2 τ1 = τ, z0 = z' = z.

Let's say R02R1-R.

Here It is.

If we look at only one phase (for example, a phase).

It can be seen that only the a-phase data is required.

Furthermore, in cases where the resistance component can be considered to be almost 0, such as in ultra-high voltage overhead power transmission lines, h=1.

is further simplified.

The b-phase and C-phase are also determined in the same manner as the a-phase, and in equations (3o) and (31), the right-hand subscripts of i and e can be replaced with b or C.

. The digital protective relay device according to the present invention has the equation (28) already proposed as follows: τ0=τ1, zO=zl, R
(ξ (t) of equation (29) obtained when O= R1
] = 0 → phase a is healthy \O - + phase a has an internal fault = 0 → phase b is healthy \0 → phase b has an internal fault = Q - + phase C is healthy \0 → phase C has an internal fault, so each phase An internal accident determination is made every time.

Among the digital protective relay devices according to this invention, (29
) An example in which the equation is followed is shown in FIGS. 4 and 5.

In either case, it is assumed that the clock pulse for all-system synchronization Gumpling and the clock pulse for Gumpling generated after a certain period of time have already been supplied.

Also, both diagrams are drawn as single-phase diagrams for simplicity.

In the figure, P and Q are terminals, CB is a disconnector, PT is a potential transformer, CT is a potential current transformer, Ryl and RY2 are digital protective relay devices according to the present invention, and SHL and SH2 are gunp rings. Hold circuit, ADl, AD2 are analog-to-digital conversion circuits, MDP is a digital arithmetic unit, TR
is an information transmission device.

Now, at time t, when the clock for all-system synchronization is supplied to Ryl, the three-phase current and three-phase voltage are held at the terminal P in synchronization with the pump holding at SH1 and SH2, respectively.

The outputs of SHl and SH2 are both introduced into ADl and AD2, and after analog-to-digital conversion, are read into the MDP.

On the other hand, the 3-phase current and 3-phase voltage that are similarly pumped at the terminal Q at time t are read into the MDP at the terminal P via the TR.

Next, in synchronization with the sampling lock that occurs at time (t + τ) delayed by τ from the above time t, the 3-phase current and 3-phase voltage are sampled and held at SHI and SH2 at terminal P, and the analog and digital signals are output at ADl and AD2. After conversion, it is read into MDP.

In MDP, the digital data read in the above manner is based on equation (29), and ξa(t), ξb(t), ξ
0(t)wop p p Calculate 1ξa(1>δ ・・・・・・(
For the phase for which a "true" value is obtained as a result of the logical determination in step 32), it is determined that there is an internal fault, and if this is the case, a cutoff command is sent to the CB.

Similar to the previously proposed device, this embodiment eliminates the need for an analog filter, which was conventionally used in this type of device, and is based on the previously proposed universal formula (28), so internal accidents can be avoided compared to the conventional device. It is possible to perform detection more reliably, extremely safely without malfunction, and at an extremely high speed to the same extent as the previously proposed device.

Although this invention is based on a strict basic principle based on the law of conservation of traveling waves propagating in overhead transmission lines, in actual power systems there is a difference between two modes, zero-phase and positive-phase, which are unique to transmission lines. Because of the fact that the surge propagation time, signal impedance, and transmission line resistance value of each mode are equal, it is assumed that the surge propagation time, signal impedance, and resistance value of the transmission line are equal.

As a result, the amount of data required is significantly less than that of a device that strictly implements the basic principles.

It is possible to obtain a digital protective relay device that not only simplifies the device, facilitates maintenance, and reduces costs, but also can be expected to have the same level of effects in terms of name.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a three-phase power transmission line (phase area), where Pa. Pb and PC indicate phase buses at terminal P, Qa, Qb, and QC indicate phase buses at terminal Q, and arrows indicate interphase couplings. Figure 2 is a diagram showing a three-phase power transmission line after mode conversion, with PO,
PI, P2 are each mode bus at terminal P, QO, Ql
, Q2 is each mode bus at terminal Q, RO, R1, R
2 is the total resistance of the power transmission line in each mode. Figure 3 shows the transmission line for mode 1, (J' t J
2y J3t J4. J5. The product is the mode current, (f'p
, f2. fs t f+ , f5. fq) is the mode voltage, (τZ, Z is the distribution constant parameter of mode 1. Figs. 4 and 5 show an embodiment of the present invention, Fig. 4 is a system diagram, and Fig. 5 is a distribution constant parameter of mode 1. is a detailed view of a part of Fig. 4,
P and Q are terminals, CB is a breaker, PT is a potential transformer,
CT is a meter current transformer, RYl, RY2 are digital protective relay devices according to the present invention, SHI, SH2 are Gumpling hold circuits, ADl, AD2 are analog-to-digital conversion circuits, MDP is a digital arithmetic device, TR is an information transmission device It is.

Claims (1)

[Claims] 1. Two types of surge propagation times τ0. A protected power transmission line where τ1 is assumed to be τ, surge impedance zO, zl is Z, total resistance RO, and R1 is assumed to be R, and the time at one end P of this protected power transmission line and the three-phase current i'' which is gunned by t+τ. (t), io(t+τ). Three-phase voltage en(t), en(t+τ), (n==a,
b, c), and the three-phase current i” at the other end Q of the protected transmission line at time t.
(t), three-phase voltage e”(t)t (n=a, b,
c) to the P end;
Based on the outputs of the second means, (n=a, b, c) is calculated and 1ξ0(t)l exceeds the positive setting value δ. and third means for determining whether the relay is present.