JPS61177120A - Protective relaying having protection area on impedance plane - 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] [Field of Application of the Invention] The present invention relates to a protective relay method having a protection area on an impedance plane, and in particular, devises measures to prevent synchronization phenomenon and malfunction when turning on a transformer. The present invention relates to a protective relaying method.

[Background of the invention]

As a protective relay having a protection area on an impedance plane, there is, for example, a distance relay with a Moh characteristic, and it is well known that this type of distance relay can malfunction due to a tax adjustment phenomenon or when a transformer is turned on.

A distance relay outputs the presence of system impedance within its protection characteristic, but in the event of a step-out phenomenon, the step-out impedance enters and passes through this protection characteristic.
Distance relay malfunctions.

To counter this, in Japanese Patent Application Laid-Open No. 48-57143 "Tax Adjustment Lock Relay System", in addition to the original distance relay M1, M
Distance relay M2 for out-of-step detection over a wider range than the maintenance characteristic of l
If the state in which M2 is activated and Ml is not activated continues for a predetermined period of time or more, it is determined that synchronization has occurred and the output of Ml is blocked. It has a timer T.

This method distinguishes between accidents and tax adjustments based on the magnitude of the impedance change rate, since accident impedance changes instantaneously, while tax adjustment impedance changes slowly. Incidentally, the system impedance changes due to the inrush current when the transformer is turned on, causing the distance relay to malfunction, but since the change is slow, malfunction can be prevented by the above-mentioned known method.

As described above, the above-mentioned known system is effective in preventing synchronization or malfunction when the transformer is turned on, but there is a problem in that the device is complicated. For accident detection, only Ml is required, but Ml and T are also required. At least two distance relays and a step-out determination circuit are required. Recently, computers are being introduced to protect power systems, but adding the above-mentioned step-out lock function means doubling the amount of programs, and it is necessary to do so within a specified sampling period. This may lead to the inability to complete necessary processing, or the necessity to lengthen the sampling period, albeit with lower accuracy.

[Purpose of the invention]

From the above, in the present invention, when realizing a protective relay having a protection area on the impedance plane using a digital method, it is possible to obtain a protective relay that does not respond to tax regulations with a slight increase in the amount of programming. The purpose is to provide a protective relaying method.

[Summary of the invention]

In the present invention, the sum of two amounts of electricity obtained directly or by synthesis from the current and voltage of the power system is calculated for a certain period,
Based on the polarity of this product value, it is determined whether the rainbow fault point is within the protection area, and it is determined that the transformer has been turned on or a tax adjustment has occurred, depending on the magnitude of the difference between the previous and current product values.

[Embodiments of the invention]

Examples of the present invention will be described in detail below, but before that,
The difference between a companion protection relay constructed using a digital computer and a conventional electromagnetic or transistor type so-called analog protection relay will be explained.

To explain this, taking a distance relay with Moh characteristics as an example,
In either case, from the voltage t, the current I, and the settling impedance for determining the protection area, the electrical quantity tiz−v+, which is generally called the distance measurement quantity, and the electrical quantity iψ, which is called the polarity quantity, are obtained.
to synthesize. In the case of an electromagnetic type, these two amounts of electricity are applied to the coil, and at this time, it is determined whether the accident is within the protection range or not based on the rotational torque produced by the coil. In many cases, with the transistor type, attention is paid to the phase difference between two quantities of electricity, and if this is greater than a predetermined angle, it is determined that the accident is within the protection range. On the other hand, in the digital format, the sum of the two quantities over a certain period of time is calculated, the product is determined, and the determination is made based on the polarity.

In this way, in the digital format, it is possible to derive the sum of two quantities over a certain period of time and directly determine the magnitude of the product, but it is possible to directly determine the magnitude of the product, but it is also possible to derive the sum of two quantities over a certain period of time and directly determine the magnitude of the product. Judgment is made by phase difference. but,
In the digital format, only one product is focused on, and the size itself is not used to determine whether it is inside or outside the protected area. In the present invention, attention was paid to the fact that size is required. This magnitude corresponds to the position of the load point or fault point on the known impedance plane. For this reason, in the present invention, the rate of change in the magnitude of the product value is monitored, and when the rate of change is smaller than a predetermined rate, the operation of the distance relay is prevented.

An embodiment of the present invention will be described below. In the embodiment shown in FIG. 1, the processing up to the third step is the same as that of Japanese Patent Application Laid-Open No. 50-74148, and only a part of the fourth step is changed according to the present invention.

First, conventional processing from the first to third steps will be explained. However, here, a protection relay with a Moh characteristic will be explained as an example of a protection relay having a protection area on an impedance plane. First, the first step is actually often provided outside the computer, and the system current i = I sin ωt and system voltage v necessary for deriving the Moh characteristics are
=Vsin(ωt+ψ) is sampled simultaneously.

Here, i and v are instantaneous values, I and V are maximum values, ω is the angular velocity obtained, t is time, ψ is current, and is a positive phase difference. Then, ω=2πf (f is frequency), and sampling is performed periodically at a frequency fs that is, for example, four times the system frequency f. Then, an AD converter converts it into digital quantities proportional to the instantaneous value at the time of sampling at time tn, i.e., 1(tn), v(tnl), and then imports it into a computer.

If time [f is used as a reference, any sample time t n
(rx), if the period of the system frequency is 2π (rad), then it is performed at an interval of 1. (rad), so t
n=t-)-□・n ・・・・・・・・・
...α)2ω However, n can be expressed as a positive or negative integer (tn=t when n=0). Therefore, i (tnl , v(tn) is
It can be expressed as below.

The box shown as the second step in FIG. 1 is a step related to the vector synthesis process to obtain the above-mentioned Moh characteristic, and in this embodiment, the polarity amount VAC-1n) and the The distance amount Vm(tn) is respectively derived.

VA(tnl= v(tn) +++++++
**+m(a)V++(tn)=i(tnlZ−v(t
n) - (4) Here, the impedance is an impedance of magnitude and phase angle corresponding to the settling impedance for defining the protected area. The process of determining Va(tn) Vm(tn) f is executed each time each sampling is performed based on the input at that time.

In the box shown as the third step in FIG. 1, the VA (tn
Equations (5) and (6) are executed based on ``l, Vi (tn)t''.

Vt= I VA (tO) I+IV* (t-1)
I +-...+ l Vl(t k) 1...
・・・・・・・・・(5) Vz” I Vm (tel I+l Vm (t l
) 1+-...+I Sb (t kl 1...
(6) Here, vA(to) means the current sampling value of Vl, and Vl(t-k) means the value of V before sampling. This is the sum of the absolute values of continuously obtained flek+1 sampling values for VA and V, and if Δatt-sampling period, then (k+1
(k+1) is selected so that 1XΔt corresponds to a half cycle of the fundamental frequency of the voltage/current of the system or an integral multiple thereof. As is clear from this, (5), (6)
The formula is to calculate the area of the sine wave using the so-called piecewise multiplication method after taking the absolute value, and if the sine wave is constant, Vl,
V2 becomes a constant value. Based on this value, equation (7) is subsequently performed.

Wo (t) = Vl(tlXVz (t)
・“−・” (7) This value corresponds to equation (8) for realizing the Moh characteristic distance relay, and the value of Wo(tl represents the position on the impedance plane.

Wo(tl= (1(tnlZ−v(tnl) v(t
nl (8) Next, step 4 will be explained. First, the conventional accident determination part will be described, and after that, measures to prevent malfunctions such as when stepping out will be explained.

In the fourth step, first, the output Wo of the fourth step is
(Wo(t)>K between t l and the reference value
・・・・・・・・・・・・・・・If we proceed assuming that the relationship is such that when (9) is determined as an accident, l), the functions necessary for the fourth step As shown in Fig. 1, first, it is determined in B3 whether or not formula (9) holds true, and when it is determined that formula (9) holds true, the number of times formula (9) holds true, that is, the number of accident detections. In order to add 1 to the counter B4 that is continuously accumulated at the time of every mi judgment, check in B6 whether it has reached the preset specified number of times mQ corresponding to the relay judgment time, and when it is late, A cut-off command is issued to the corresponding breaker CB (not shown), and if the reverse has not been reached, the process returns to the first step without issuing a cut-off command.From the next sample time, the first step is started again. From step to step, configure it to work in exactly the same steps as above. Also,
If it is determined at the beginning of the fifth step that equation (9) does not hold, the contents of the accident detection counter accumulated up to that point in the BS are cleared and the process returns to the first step.

In the present invention, the fourth step includes simple processing Bl.

Add B2 and only 9 and get rid of i! 11c1-tsuku function. Here, to briefly explain the phenomenon of step-out using Fig. 3, the area is the normal load band, and in the event of an accident, the impedance is the point PI within the load voltage.
Therefore, it instantly moves to 22 points within the protection area of the Moh characteristic. On the other hand, the impedance at the time of synchronization moves upward along the trajectory.

By the way, the output Wo (t) of the third step
varies in magnitude depending on the location of these impedance points. In the case of Tsumashi and Mo characteristics, Wo (t) >
.

As is clear from the fact that is the operating region, the area inside the circle in Fig. 3 is Wo(t L > 0, and the area outside the circle is wo(tK).

, and the circumferential portion is Wo(t)=O. The center of the circle is positive infinity, and the further away from 1 circle, the larger the negative value. As is clear from these explanations,
In the case of an accident, Wo(t) changes instantaneously from negative to positive as shown in Figure 4a, and when the tax adjustment is on the trajectory t, We(t) changes at each sampling point as shown in Figure 4a. The value gradually changes from a large negative value to a small negative value, then from a small positive value to a large positive value, and then decreases to a negative value. Note that the impedance seen by the distance relay also changes when the breaker of the transformer is turned on. The impedance locus at this time is expressed as shown in FIG. 3 rl when no load is applied, and as shown in FIG. 3 r2 when a load is applied.

Similarly, the magnitude of Wo is as shown in FIG. 4C when rl is %, as shown in FIG. 4D when r2.

From the above, in the present invention, the rate of change ΔWo of Wo(t)
(t) t-monitors and prevents the distance relay output from tripping the breaker when it is changing;

In step 4, first, with respect to the output W, (tl) of the third step in Bl, the difference ΔWo(t) is determined as the difference between the current value Wo (t) and the previous value νVo(t11.Next, At B2, it is confirmed that the magnitude of ΔWo(t) is in the range of Kl≦ΔWO (mouth≦1).

Here, the value of K1 is assumed to be relatively small, and FIG. 5 illustrates the relationship between the deviation ΔWo(t) and ±1 in FIG. 4. Assuming that Kl is close to zero, Figure 4 shows c.
, d, the condition B2 does not hold, and the condition B2 holds only before or after the accident occurs in case a. Therefore, when Kxk is selected to be small, when the condition of B2 is satisfied (yes side), the process moves to B3 as in the conventional case, and it is determined whether there is an internal or external fault in the distance relay. Condition B2 is not satisfied (N
o side), the breaker is prevented from being tripped by the output of the distance relay, but there are various ways to do this.
Method (2) moves to the BS and clears the accident detection count mf to zero, and moves to the IIHBs and passes the process of B4. B4 processing is done by accident detection circuit m
f is to be updated, and 1 is not updated, so the allowable number of trips mQ is not reached. There are many other possible methods for trip-locking the circuit breaker, but any method that can substantially trip-lock may be used, and various methods can be used. In addition, in the characteristic d' of FIG. 5, for example, ΔWo(t) between time t=4 and t=5 is very small, and the above relational expression - may be satisfied with ≦ΔWo(11≦1). However, once it is determined that synchronization has occurred, by storing the determination result of synchronization for an appropriate period of time, it is possible to prevent erroneous shutoff during this period. Erroneous disconnection can also be prevented by setting the set value mot to a sufficiently large value.When configured as shown in Figure 1, before and after the accident occurs, the BI B2-83 route in the fourth step If an accident occurs, the accident can be stopped.

However, only immediately after the accident occurs (at time t=4 in Figure 8, L
Processing is performed on the Bx-B2 Bs route. When the impedance changes due to tax adjustment or changer input, B
The I Bz Bs route is processed and the trip is locked.

Although the above description has been made regarding the Moh characteristic relay shown in FIG. 3, it goes without saying that this can be realized using a reactance relay shown in FIG. When using a reactance relay, (HtlX.

-V[t)) and I(tlXo) can be obtained by vector synthesis, and then the process of step 3 can be performed.

As described in detail above, according to the present invention, when configuring a mining relay having a protection area on an impedance plane by a digital method, tax adjustment and breaker insertion can be performed by adding a small amount of programming. A lock operation can be performed to prevent malfunctions.

〔Effect of the invention〕

In Japan, maintenance WII of ultra-high voltage system busbars, transformers, and power transmission lines
Fi is multi-layered protection consisting of main protection and back-up protection, and most of the back-up protection consists of distance relays. Much of the protection for lower voltage systems comes from distance relays.

A step-out locking means is indispensable for these distance relays, and if the present invention can be used to lock out-of-step with the addition of a very small program to conventional distance relays, the industrial benefits of the present invention will be extremely large. It is said that there is no coffin.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the characteristics of a relay having a protection area on an impedance plane, and a detailed explanatory diagram of the second and third steps. This is a diagram showing how the product value vVo(tl) obtained in the third step changes in various situations,
FIG. 5 is a diagram showing changes in the time differential value ΔWe(t) of Wo(tl).B!...Time derivative ΔWo(t) derivation step, B
2...30th 48th

Claims (1)

[Claims] 1. Deriving the measured distance and polarity from the sampled values of current and voltage introduced from the power system, finding the sum of absolute values for each over a certain period, and determining internal and external faults based on the sign or negative of the product of the sums. A protective relaying method having a protection area on an impedance plane, characterized in that output of an internal accident determination is blocked according to the magnitude of a time change in a product value.