JPS5983531A - Distance relay - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to measures against distorted waves in a distance relay that is applied to and protects a power system.

A conventional device of this type is shown in FIG.

In the figure, (1) is the generator of the power system, (2) is the impedance behind the relay installation point P, and (3) is the reactor between the relay installation point P and the fault point F, which has a size L s
(4) is a resistance with a size R, (51 is a current transformer (hereinafter C
(abbreviated as T), (6) is a voltage transformer (hereinafter abbreviated as PT)
, (7) is a transformer with a gap, (8) is a resistor, (9)
, Ql) is a filter that passes the fundamental wave (hereinafter referred to as B
PF), Qn is an arithmetic circuit, (2), (13 is a rectangular wave conversion circuit, α4 is an AND circuit, θ5J is an on-delay timer, (11 is an off-delay timer, and Qη is a distance relay. Ruru.

Next, the operation will be explained. When a fault occurs at point F, a fault current flows, is detected by the CT (5), and the fault current flows through the primary winding of the gapped transformer (7). This current is induced as a voltage in the secondary winding of the gapped transformer (7), and in a parallel circuit with the resistor (8), the distance relay αη
produces a phase shift corresponding to the maximum sensitivity angle of . on the other hand,
The voltage across the reactor (3) and resistor (4) is PT (6
) to detect. These two voltages are respectively B P F
' (9) , pass the fundamental wave at α0, and the arithmetic circuit QX
l and the square wave conversion circuit (2). The arithmetic circuit α calculates the distance to the accident point and outputs an output V, which is applied to another rectangular wave conversion circuit (b). The rectangular waves of Vl and V from the respective rectangular wave conversion circuits (2) and (2) are logically multiplied by an AND circuit Q4, and the on-delay timer θ is
Check the time width of the logical product in 5). When this time width is longer than the time of one on-delay timer (+6),
This signal is then extended by the next off-delay timer, T2, which is more than the time equivalent to one cycle of the fundamental wave, and then the distance relay Q? An output signal is obtained from the O terminal of ).

Figure 2 is a time chart for explaining Figure 1.
), (a), and (b) are respectively arithmetic circuits (b)
(c) and (d) show the output V of B P F H and the output v2 of B P F H, (c) and (d) are
) is applied to the rectangular wave conversion circuit (2), and the outputs are vt and vt. (e) is the output of the AND circuit, and (if) is the one whose startup time is delayed by +1. by the off-delay timer (151);
) is the fall time delayed by T2 by the off-delay timer Q, and this waveform (g) becomes the output of the O terminal of the distance relay Q.

Conventional equipment is configured as described above, and when an accident occurs, even if harmonics other than the fundamental wave are included, the BPF (9
) Due to the effect of tαO, the fundamental wave was selected, resulting in a distance relay that reduced the influence of harmonics. When harmonics are included, the times at which Vl and v2 in FIG. Since v2 no longer has the length of a half cycle, but becomes longer or shorter, the output signal width of the AND circuit changes, and the measurement by the on-delay timer T+ includes an error.

In order to reduce the influence of such high frequencies, conventional distance relays are equipped with a BPF to remove harmonics.

However, as modern power systems have become longer distances, static capacitors have been inserted to stabilize power transmission, and cable transmission lines have been introduced in urban areas, capacitance has rapidly increased. It is increasing. Therefore, the frequency of harmonics at the time of an accident tends to approach 2 to 8 times the frequency of the fundamental wave, and it is becoming extremely difficult for BPF to separate the fundamental wave and harmonics. In order to improve the separation, it is possible to make the characteristics of the BPF steeper, but if the characteristics are made too steep, the operation time of the distance relay will be significantly delayed, and the P13PF itself will be damaged due to variations in parts, temperature changes, etc. It has become difficult to maintain these characteristics, making it impossible to put them into practical use.

As mentioned above, in conventional distance relays, when harmonics close to the fundamental wave are mixed in, they cannot attenuate the harmonics sufficiently, resulting in very poor characteristics, such as the situation shown in Figure 3. It had become. FIG. 8 shows the phase characteristics of the distance relay when the harmonic frequency is eight times the frequency of eight waves and the magnitude is 800% of the fundamental wave. The dotted line shows the characteristics when only the fundamental wave is used; however, when a large amount of harmonics are included, the operating range almost disappears, as shown by the solid line.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and the system current introduced into the distance relay is transferred to a simulated impedance such as a series circuit of a reactor and a resistor similar to the configuration of a power transmission line, or The voltage is converted by passing it through a simulated impedance with the same transfer function, and this is calculated and multiplied. From the result, only the DC component is obtained, and by determining the distance, countermeasures against harmonic contamination can be taken. The purpose is to provide a distance relay that has been applied.

An embodiment of the present invention will be described below with reference to the drawings. Fourth
In the figure, Q81 is a simulated reactor, (I9) is a simulated resistance, (Company) is a simulated impedance @D is a memory circuit, (2
) is a multiplier circuit, (2) is a low frequency pass filter (hereinafter L
(abbreviated as PF) (Incorporated) is a level detection circuit, and □□□ is a distance relay. When an accident occurs at point F and the fault current flows as shown in the figure, both ends of a simulated impedance consisting of a reactor θ with an inductance value of LR and a resistance of 0 with a resistance value of is \Rat + (
A voltage of a+LH)"-・I-ZR・■ is obtained. Due to this current, the phase is delayed by θ.

Input the voltage of zR and the voltage E obtained from PT (6) into the arithmetic circuit αη, and calculate (ZR-I-E).
The following calculation is carried out, and the output is set as Ml.

A voltage E is applied to the memory circuit (21) to store the voltage value from several cycles ago, and the output is set to v2.
The voltages v1 and v2 are applied to the multiplier circuit as BM.
= EM to perform multiplication of vIXV2.

The output of this multiplier circuit (incorporated) is introduced into the LPF @ to obtain only the DC component, and the level judgment circuit (241) detects when the voltage becomes positive, and the output is connected to the distance relay (incorporated). 0 of
Get it from the terminal.

In FIG. 5, the explanation is based on vectors, where the horizontal axis represents the faulty electric current, and ZR-■ is taken at the point delayed by θ.

The output voltage of P T (6) was E until the accident occurred.
However, after the accident occurred, 1. Therefore, the calculation circuit (1
The output of 1) is from v1=ZRIE, V11==
Changes to ZRI-E. However, the memory circuit (211
The voltage v2 is constant before and after the accident, and v2 = E =
It is BM.

Therefore, the angle between vl and v2 was greater than 90° before the accident, but became less than 90″ after the accident.

The angle αc is an angle determined by the reactor (3) and the resistor (4), and is expressed as -1ωL α=tan]r, which is the power factor angle between the fault current I and the voltage E.

Figure 6 is an explanation using a time chart, (a) is P
(b) shows the output voltage v1 of the arithmetic circuit 04), which becomes vts after the accident. When the waveforms (a) and (b) are multiplied by the multiplier circuit -, a waveform with twice the frequency as shown in (C) is obtained.

Before the accident, the average value was below zero level, but after the accident,
The average value is above the zero level. Therefore, LPF(trans))
The output waveform averaged through the filters is as shown in (d), and at the point exceeding the zero level, the output of the level detection circuit (241) is obtained as shown in (e).

The operating time is calculated from the double frequency of the fundamental wave in (c) to (d)
There is only a delay in LPF'[ to obtain the DC component of has the advantage of being easy to make.

In this way, according to the configuration shown in FIG. 4, if the two voltages v1 and v2 are 90 degrees, the output of the LPFM is not equal to the zero level, which is the operating limit point, so as shown in FIG. A distance relay with a mho characteristic such as O can be realized.The above relationship will be expressed by a mathematical formula.

v, (t)-Jr 'Zty ・l5in (ω is 10-
JTEstn(art→−(E) −°“−■v2
(t) = JT EM si! 1 (or 10α)
・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・■, so the output of the multiplier circuit is V2v(t)X v2(t) -ZRIE, (Colt (θ-α)- cm('l
, ωi + θ ten α))-Ii', EM (1-cos
(2a + t + 2a )), and the output of LPF (231) is ZR-I (θ-α)-E if we focus only on the DC component, and in the level detection circuit (foundation), it is ZR-I (θ-α). )-E≧0 Therefore, since E/E is the impedance up to the accident point F, it can be obtained. Equation 0 is the equation of a circle with zR as the diameter, and Fig. 6 is obtained. Become.

Next, consider the characteristics when a fundamental wave current and a harmonic current flow in a superimposed manner in the fault current i.

Let the current flowing into the fault point be the following equation 0, i2JiNI
s=ωt +JTkIsin(mωt+β)・・・・・・
・・・・・・・・・・・・・・・・・・■■Two fundamental wave current β: The harmonic superimposed phase PT voltage is = Jfj, RIstnωt +JE k RIM
(mrot+β)+JT ωLIanat +JTkm
ωLIcos (mωt+β)==JTZIs+n(a
+t+α)+JTkZrnIsin(mωt+β+αm
) -■zN"6" The voltage across RR and LR of the simulated impedance (a) of the distance relay is 1 eRY = I (Ri + LR- t = 5ZHIjin (ω is 10) - 1TkZ1mIs
in(ma+t+β+θRm)...■. Therefore, the output of the multiplier circuit (2) is V = MI X Vl = (eRy - ePT) X errM"! 5Z
B l5tn(ωt+θ)+ffkzR, nl5in
(+nωt+β+θRm >-JTz Engineering=(ω=1α)
-K kZm Isin(mcDt+β+am))xH
EMsin(ωt+α) = 2BMI(ZRgirl(alt+θ)”(a+t
+a) +kZRmsm(rnωt+β+θHm) sin
(ωt+a)-Isin2(ωt+α)-kZmst
n(mart+β+αm)sin(ωt+α))=EM
I(ZR(cIy&(θ−a) −cos (2tu
t+θ10α))+kZRm(αs(mω1ω10β+
θRm-α)-αi (mωt+ω to 1β+θRm+α)
)−z(1−■(2ωt+2α)) −k Zm (cas(ma+t −a+t+β+am
-(Z)-crys(mωt+a+t+β+am+α)
)] If only the DC component is taken out and only the positive is operated, then
ZR■(θ-α)−Z≧0 Therefore, the formula ■ is obtained.

Z≦ZRal18(θ−α)・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・
・■This ■formula is exactly the same as the 0 formula found for only the fundamental wave, and has the same characteristics as shown in Figure 5.

Therefore, no matter how high the harmonic order m is or how high the harmonic content k is, the characteristics obtained when only the fundamental wave is present can be obtained.

The time required to store the voltage of the PT circuit is only for a few cycles during which the distance relay operates, opens a circuit breaker (not shown), and eliminates the fault, and no longer is necessary. If the configuration of the memory circuit is analogous,
This can be achieved with a resonant circuit, or in the digital case, with a memory circuit.

In addition, in the above embodiment, a case where an inductance and a resistor are connected in series is shown as the simulated impedance, but other methods may be used as long as the transfer function is the same. For example, the operational amplifier shown in FIG. It may be a combination of a resistor and a capacitor.

The simulated impedance in this case is a resistor that generates a voltage vIN proportional to the current I, a capacitor C and a resistor R.
1 (c) Resistor R1 and operational amplifier == Kl
(S + K) WIN Therefore, the transfer function G(s)
is G(sl = S 0. This is equal to the transfer function of a series circuit of resistance and inductance.Also, in the above example, the block diagram of an analog circuit is shown, but it can be implemented using a digital processing circuit. has the same effect.

As described above, according to the present invention, the system current is converted into voltage by flowing it through a series circuit of a reactor and a resistor or a simulated impedance of the same transfer function, and this is calculated and multiplied by the voltage before the accident. By determining the distance by obtaining only the DC component from the results, it is possible to realize a distance relay that does not change its characteristics at all when harmonics are mixed in and has a high operating time.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional distance relay, and Fig. 2 is a block diagram of a conventional distance relay.
An operation time chart, FIG. 8 is a phase characteristic diagram when harmonics are mixed, FIG. 4 is a block diagram of a distance relay according to an embodiment of the present invention, and FIG. 6 is an explanatory diagram showing that the Moh characteristic is obtained. FIG. 6 is an operation time chart, and FIG. 7 shows another method of realizing simulated impedance. (1)... Generator, (2)... Rear impedance, (3)... Reactor, (4)... Resistance, (5)...
...CT, (e)...P T , (7)...Transformer with gap, (8)...Resistor, (9), α1...
・BPF. 0p... Arithmetic circuit, (2), α3... Rectangular wave conversion circuit, a4... AND circuit, (151... On delay timer, αQ... Off delay timer, Q7
)...Distance relay, θ Enoki...Simulated reactor, 09)
...Simulated resistance, wire...Simulated impedance (2+1
...Memory circuit, Q2...Multiplication circuit, (b)...L
PF, (foundation)...level detection circuit, (to)...distance relay, spider, w, 4...resistor, Qη...capacitor, -...operational amplifier. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Makoto Kuzuno - Figure 1 Shi-1, -1 Figure 2 □t 1 Figure 3 Figure 5 Figure 4 Figure 6

Claims (1)

[Claims] A distance relay that calculates and determines the distance to a fault point by introducing the system voltage and current of the power system, and is configured with a series circuit of a resistor and a reactor, and whose power factor angle is A first calculated voltage obtained by adding a simulated impedance equal to the maximum sensitivity angle of the distance relay, the system, and a simulated voltage obtained by applying the current to the simulated impedance to the system voltage, and the system voltage. a multiplier circuit that multiplies a second calculated voltage obtained by holding a value from a predetermined time before; a filter that extracts a DC component from the multiplied voltage of the multiplier circuit; 1. A distance relay comprising: a level determination circuit that detects and outputs that the output voltage of the filter is a predetermined value. (2) Claim 1 is characterized in that, when F(s) is a transfer relationship of simulated impedance, S is a complex number component, and K is a real number component, F(s) = S 0. Distance relay as stated.