JPH061938B2 - Transmission line failure detection relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Use of the Invention) The present invention relates to a relay capable of quickly and reliably detecting a failure that has occurred in a power transmission line due to a lightning stroke or the like.

(Prior art and its problems) Most of the accidents that occur in power transmission lines are ground faults, and the main cause is the arc generated between the power transmission line and the ground due to lightning. In most cases, such a ground fault is extinguished at the initial stage of arc generation due to flashover by cutting off the power transmission line having a ground fault at both ends to leave no voltage. Therefore, as in the reclosing method, for example, after a short time after the occurrence of a failure is detected, that is, before the voltage phase difference angle between the transmitting and receiving ends does not open greatly, the circuit breaker is operated to make the transmission line voltageless, and then the arc is extinguished. The reclosing method, in which the circuit breaker is reclosed after the required time, is effective in improving transient stability.To this end, the circuit breaker operates at high speed and the failure detection relay ensures high speed and reliable operation. Detection is required.

However, the FM current differential relay or the PCM current differential relay, which has been mainly used in the super high voltage system in the past,
It is difficult to hope for higher speeds than at present. That is, as shown in FIG. ₁ , the current differential relays RY ₁ and RY ₂ use the currents _s and i _R flowing through the self-end S and the opposite end R to obtain ξ (t) = i _s (t) + i _R (t) …………………… (1) is used to detect a failure, for example, as shown in FIG. ₁ , due to a failure F ₁ that has occurred in the transmission line L ₁ , currents _s , i in the direction of the solid line arrow in the figure. _{When R} flows, when ξ (t) ≠ 0, an internal fault (protection range), and when a fault F ₂ of the transmission line L ₂ causes currents _s and i _{R in the} directions of dotted arrows in the figure to flow, ξ (t) From 0, it is judged as an external failure (outside the protection range).

However, as is well known, since this conventional relay is operated by the fundamental wave component extruded from the current flowing at the time of failure by filtering, it is necessary to remove the transient harmonics in the current generated at the time of failure. Therefore, an operation delay is caused by filtering. Therefore, it is impossible in principle to expect the fault detection speed by the conventional relay to be higher than the present fault detection speed, and it is impossible to expect the transient stability higher than the present time.

Therefore, research has been conducted in the past to improve the fault detection speed. For example, the well-known wave equation Here, e: voltage, i: current, x: distance, t: time, L: inductance per unit length, C: capacitance per unit length, which is derived from the well-known Bergeron relational expression. Is proposed.

That is, the solution of this wave equation is known as the solution of D'Alembert and is given by the following equation.

here f, g: If g is deleted from the arbitrary function (3), which is determined by the environmental conditions, i (t) + 1 / Ze (t) = 2f (tX / V) ………… (4) The end (X = 0) is S, the other end (X = d)
Assuming that R is the traveling wave from S to R, equation (4) at each end is Here i _s: local end current, i _R: remote end current, e _s: local end voltage, e _R: mating end voltage, and becomes. Therefore, instead of t in the equation at the S end of equation (4), t
By substituting −d / V and subtracting the R-end equation from the S-end equation, we obtain the Bergeran relational expression shown in Eq. (6) (the − sign at the R-end represents the current flowing from the bus to the line direction). This is because it was positive.) Where τ = d / V (surge propagation time) The condition for failure detection shown in Eq. (7) Equation (8) showing the discriminant function with Is the basic operation of the relay. This method is intended to determine an internal or external fault by using a distorted wave that contains a harmonic component such as a surge in addition to the fundamental wave component, and extracts the fundamental wave component by filtering like a conventional relay. The purpose of this is to eliminate the need, eliminate the delay in the detection of the current based on the extraction, and perform the fault detection at high speed.

However, since the relay based on this basic formula basically uses the magnitude of ξ (t) determined by the magnitude of voltage and current, it is not certain to judge internal and external failures. That is, there are various modes in the surge propagation time τ and the surge impedance Z in the equation (8), and when various frequency components such as voltage and current at the time of failure are included, τ and Z are uniquely defined. It is difficult to determine. In addition to this, Eq. (8) focuses on the forward wave, that is, the wave that goes from the S end to the R end, and furthermore, due to the influence of the reflected wave at the failure point or measurement point, that is, the relay installation point, the differential of the surge component wave In addition to the complete failure of the principle, due to the effects of hardware errors and noise from converters,
When an external failure occurs, ξ (t) ≈0 does not hold and there is a problem in application to a protection relay in terms of failure determination accuracy.

The present invention provides a relay capable of reliably identifying internal and external faults at a high speed so that transient stability can be further improved. Next, the details will be described with reference to the drawings.

[Structure of Invention]

(Means for Solving Problems) In the present invention, the integral value of ξ (t) in the equation (8) before internal failure does not matter whether the type of failure, the failure point, the failure occurrence phase, the line length, or the resistance of the failure point. On the other hand, in the sound phase, the change increases and decreases after the occurrence of the failure, but stays below a certain level, whereas in the failure phase, it increases monotonically until a certain time after the occurrence of the failure and becomes a large value, and the integral value of ξ (t) is There is a marked difference between before failure and after failure. Therefore, ξ before and after the failure
The present invention has been made in view of the fact that an internal failure (protection range) can be detected based on the magnitude relationship of the integrated value of (t), and the features of the present invention are as follows.

That current voltage i _s the local end S detected from the grid, e _s
And ξ (t) obtained from the equation (8) based on the current voltages i _R and e _{R of} the other end R, for example, as shown in FIG. i _s, of e _s 1 /
The value corresponds to a value obtained by integrating the respective sampling values between 4 ^{_{cycles) S 1 = ▲ ∫ t t}} -m ▼ ξ (t) dt ............ (9), the predetermined period n (For example, 1 cycle from point A in the figure)
The value corresponding to the integrated value of each sampling value during the detection target time m in the previous detection S ₂ = ▲ ∫ ^t-n _t-n-m ▼ ξ (t) dt ………… (10) and By comparison, the magnitude relationship of the integrated value S ₁ at the present time with respect to the integrated value S ₂ before the predetermined period n, for example, the ratio of the two, η (t) = S ₂ (t) / S ₁ (t ₁ ) ... (11 ) Or the difference η (t) = S ₂ (t) / S ₁ (t) ………… (12), and when η (t) after the failure exceeds a certain threshold, internal failure Therefore, the failure is detected without performing the filtering that causes the operation delay.

In view (effect of the action) the 3 (a) (b) is 2 lines model system shown in FIG. 5, 2 line ground fault, # 1L transmission line F ₂ points between A-B substation (internal In the RS phase of (fault), the fault point resistance is 0
Ω, the change in the ratio η (t) of the area S ₂ (t) to S ₁ (t) at the A substation in the protection section when the failure occurs at phase 0 ° # 2L is obtained for each RST phase. Fig. 4
(a) and (b) show the changes in η (t) at the B substation outside the protection section at the time of the above failure, with the failure line # 1L and the healthy line #
2L and 2L, respectively. In Fig. 3 and Fig. 4, the plot interval of η (t) is 1
Every 0 μsec.

As is clear from this, at the time of an internal failure, it increases or decreases after the failure occurs in the sound phase T of # 1L as shown in FIG. 3 (a), but it is close to the level before η (t) = 1. On the other hand, the values of the R and S phases, which are the failure phases, show a tendency to increase monotonically until a certain time after the occurrence of the failure, and have large values. Also, η (t) of R, S, and T phases of # 2L, which is a healthy line
Also falls below a certain level close to η (t) = 1 before the failure.

Therefore, for example, if the judgment value is set to 10 as shown by the dotted line in FIG. 3, it can be judged as an internal failure if η (t) of the R and S phases exceeds this, and 5 msec after the failure occurs.
It can be seen that the failure can be detected with a certain degree.

For the above failure, # 1 between B and C outside the section
In the relays set to L and # 2L, η (t) of each phase of # 1L and # 2L falls within the level below the judgment value 10 as shown in FIGS. 4 (a) and (b). Therefore, from now on, sections # 1L and #B of section B-C
The relay set to 2L does not work and is judged to be an external failure.
In the above, the failure point is F _{1 to} F _{6 of} Line 1 in FIG. 5, the type of failure is the R phase 1 wire ground fault of the # 1L line, and the R and S phase 2 of the # 1L.
Similar results are obtained when a line ground fault, a two-phase ground fault that spans the R phase of # 1L and an S phase of # 2L, or a fault occurrence phase is 0 to 90 °, and the fault point resistance is set to 50Ω and 100Ω. It didn't change even if.

(Example of Implementation Circuit) In FIG. 6, L is a transmission line, DV ₁ , DI ₁ and DV.
₂ , DI ₂ are both phase voltages at both ends, S and R ends, phase currents _es ,
The detectors i _s and e _R , i _R , and RY ₁ and RY ₂ are the relays of the present invention, and are composed of the following parts. IR ₁ , I
R ₂ is an input converter that converts each phase voltage / current into a level suitable for operation calculation of the relay. SH ₁ and SH ₂ are sampling and holding circuits, and detectors DV ₁ , DV ₂ and D are detected by a signal from the sampling synchronization signal generating circuit SS.
For example, A / D conversion of each phase voltage / current by I ₁ and DI ₂
This circuit holds each data in order to sample every 10 μsec. A / D ₁ and A / D ₂ are analog
The digital converters PU ₁ and PU ₂ are arithmetic processing units, which include a central arithmetic processing unit, a ROM storing programs such as the relay logic, trip sequence, and automatic monitoring function of the present invention, and relay arithmetic processing. It is composed of a RAM for temporarily storing the intermediate results and the like. P / S ₁ , P / S
₂ is a parallel / serial conversion circuit, PI ₁ and PI ₂ are optical interface circuits, and S / P ₁ and S / P ₂ are serial
In the parallel conversion circuit, the analog / digital converters A / D ₁ and A / D ₂ convert an analog signal of the sampled voltage and current into a digital signal to operate the processing unit P.
In addition to U ₁ and PU ₂ , parallel / serial conversion circuits P / S ₁ and P / S ₂ and an optical interface circuit, PI
₁ and PI ₂ and the optical transmission circuit PL to the respective relays RY ₁ and RY ₂ respectively. Then, the received series signals such as e _s , i _s or e _R , i _{R of} each phase are converted into parallel signals by the serial / parallel conversion circuits S / P ₁ and S / P ₂ , and the arithmetic processing unit PU ₁ , In addition to PU ₂ ,
The integral of ξ (t), the storage of the intermediate result, and the calculation of η (t) are performed. IO ₁ and IO ₂ are input / output interface circuits, which perform input / output processing such as relay calculation results, and circuit breaker trip commands and switching circuit commands based on the results.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a conventional relay, FIG. 2 is a waveform diagram for explaining the principle of the present invention, FIGS. 3 and 4 are explanatory diagrams of the determination operation of the present invention by a model system, and FIG. 5 is a model. A system diagram, FIG. 6 is an example circuit diagram of an embodiment of the relay of the present invention. S ... local end, R ... remote end, e _s, e _R ... voltage, i _s, i _R ... current, _{L 1, L} 2 _... transmission line, # 1L, # 2L ... 1 No. and Line 2, _DV 1, DV ₂ ... Voltage detector, DI ₁ , DI ₂
... Current detectors, RY ₁ , RY ₂ ... Relays, IR ₁ , IR
₂ ... Input-input converter, SH ₁ , SH ₂ ... Sampling / holding circuit, A / D ₁ , A / D ₂ ... Analog / digital converter, SS ... Sampling synchronization signal generating circuit, P
U ₁ , PU ₂ ... Arithmetic processing unit, P / S ₁ , P / S ₂ ... Parallel / serial conversion circuit, PI ₁ , PI ₂ ... Optical interface circuit, S / P ₁ , S / P ₂ ... Serial / parallel Conversion circuit, IO ₁ , IO _2, ... Input / output interface circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Otsuki 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (72) Tadashi Ogawa 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc. (56) Reference JP-A-53-109142 (JP, A)

Claims (1)

[Claims] 1. A value of a discriminant function ξ (t based on a Bergerand's relational expression derived from a wave equation using a current i _s and a voltage e _s at its own end and a current i _R voltage e _R at the other end in a transmission line. ) = i _s (t-τ) + i _R (t) + 1 / Z {e _s (t-τ) -e _R (t)} (where t is time, τ is surge propagation time, and Z is surge impedance ) For a predetermined time m, a comparison circuit for comparing the current integration value S ₁ by the integration circuit with the integration value S ₂ before the predetermined integer multiple cycle n, and this comparison circuit A failure detection relay for a power transmission line, comprising: a determination circuit that determines that a failure has occurred in the internal power transmission line when the comparison result of 1 exceeds a predetermined threshold value.