JPH04248314A - Protective relay for higher harmonics filter facility - Google Patents

Abstract

PURPOSE:To realize positive response to short circuit fault or ground fault by detecting current flowing into each higher harmonics shunt, extracting basic wave component and determining a differential current, and then detecting increase/decrease of current for each shunt. CONSTITUTION:Currents flowing through filter circuits 2a-2d comprising series circuits of capacitors, reactors, resistors and the like in respective higher harmonics shunts are detected through current transformers 3a-3d and fed to basic wave extracting circuits 1a-1d comprising higher harmonics damping filters 11a-11d, sampling circuits 12a-12d and effective value operating circuits 13a-13d. Increase/decrease of current in thus extracted basic wave component is decided according to a predetermined decision formula. The output is processed through a logic circuit 5 and a trip command signal is outputted according to a predetermined criterion. According to the invention, the protective relay responds accurately to any fault, including short circuit fault and disconnection, in capacitor elements and filter facilities.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmonic filter equipment protection relay provided for protecting harmonic filter equipment.

0002

2. Description of the Related Art In places where a large amount of harmonic current is generated, such as a frequency conversion station, harmonic filter equipment is installed in parallel with the ground in order to absorb the harmonic current.

[0003] Harmonic filter equipment is a combination of a dedicated filter for removing a single frequency and a dual-purpose filter for removing multiple harmonics at the same time. The 11th and 13th harmonics are removed by dedicated filters, and the higher harmonics are removed by a dual purpose filter. Note that the nth (n=5, 1
The shunt that flows the 1st, 13th) order harmonics is called the n-th shunt (this shunt is equipped with a dedicated filter), and the shunt that flows all the higher-order harmonics is called the HP shunt (this shunt is equipped with a dedicated filter). A dual-purpose filter is provided in the shunt).

[0004] Accident 1 in this harmonic filter equipment
One of these is the failure of capacitor elements and reactor elements that make up the harmonic filter equipment. There are several ways to detect these faults, including a method to detect impedance. The detection method has been adopted as an excellent method. The reason why we are looking at the same phase here is that if it is the same phase, it will not be affected by unbalanced phase voltages. Another reason is that the impedance method has the disadvantage of being affected by frequency fluctuations.

FIG. 5 shows a circuit diagram of a conventional analog protection relay for detecting the same-phase fundamental wave difference current (see Nissin Electric Technical Report Vol. 23. No. 2 (1978, 4)). In the figure, the fifth branch 5L and the first branch are high frequency branches.
1st branch 11L, 13th branch 13L, HP branch HPL 4
A protection relay is shown that monitors the differential current between each shunt. Below, 5th branch 5L and 11th branch 1
The protective relay that monitors the differential current between the shunt and the shunt 1L will be described, but the operation of the protective relay that monitors the differential current between the other shunts is also similar to that of this protective relay, so the explanation will be omitted.

As shown in FIG. 5, a filter circuit consisting of a capacitor C5, a reactor L5, a resistor R5, etc. is installed in the fifth branch 5L, and a filter circuit consisting of a capacitor C11, a reactor L11, a resistor R11, etc. is installed in the eleventh branch 11L. A filter circuit consisting of current transformers CT1 and CT is installed to detect currents i5 and i11 flowing through each shunt 5L and 11L.
2, CT3, CT4, CT5, and CT6 are installed. Output terminals of current transformers CT1 and CT5 are cross-connected to each other through compensation current transformers CCT1 and CCT2, and are detected by current transformers CT1 and CT5, and corrected by compensation current transformers CCT1 and CCT2. The difference current Δi between the currents is taken. Compensation current transformer CCT1,C
CT2 is for correcting the difference in fundamental wave rating values between the shunts at the time of initial adjustment. This difference current Δi is the fifth
Each harmonic component is absorbed by the harmonic pass filter F5 and the eleventh harmonic pass filter F11, and only the remaining fundamental wave component is introduced into the shunt failure detection relays 5A and 11B.

The shunt failure detection relay 5A is a relay that detects an increase in the current flowing through the fifth shunt based on an increase in the differential current Δi, with the current i5 flowing through the fifth shunt as a reference (ipol), The shunt failure detection relay 11B is the first
This relay detects an increase in the current flowing through the 11th branch based on the current i11 flowing through the 1st branch based on a decrease in the differential current Δi.

By configuring the protection relay as described above, it is possible to perform a protective operation against typical accidents such as element failure in a single branch or element failure in two branches of the same phase. For example, if the impedance decreases due to an element failure of the capacitor in the 5th shunt, the fundamental wave current passing through the 5th shunt will increase, and the 5th shunt side difference current between the 5th and 11th shunts will increase. When relay 5A operates, relay 5B installed between HP and fifth shunt operates due to the increase in the difference current between HP and fifth shunt, so the trip command is issued by the operation of these relays. I can put it out.

Furthermore, when an element failure occurs in the capacitors in the same phase of the two shunts, for example, in the same phase of the 5th shunt and the HP shunt, the current in the 5th shunt and the HP shunt increases. In order to increase the current, the relay 5A operates due to an increase in the fifth branch side difference current between the fifth and eleventh branches, and
Since the relay HPB operates due to an increase in the HP shunt side difference current between the 13th-HP shunt, a trip command can be issued under this condition.

[0010] Furthermore, a single shunt ground fault/disconnection fault, for example, a ground fault installed in the conductor section of reactor L5 of the fifth shunt,
Alternatively, if the resistor R5 is disconnected, the 5th shunt current decreases, and equivalently the 11th shunt current between the 5th and 11th shunts decreases.
The shunt side difference current increases and relay 11B operates, and the HP shunt side difference current between HP and the fifth shunt increases and relay HPA operates, so a trip command can be issued under this condition.

[0011]

[Problem to be Solved by the Invention] However, in the case of the above-mentioned capacitor internal element failure, the current in the faulty branch increases, but in the case of a ground fault or disconnection fault, as can be seen from the above explanation, the current in the faulty branch increases. The current in the path only increased equivalently, and the decrease in current could not be directly detected. Therefore, there was confusion in that the relays in the faulty branch did not operate, but the relays in the non-faulty branch did.

Therefore, in the present invention, when protecting harmonic filter equipment by detecting the same-phase fundamental wave difference current between shunts, a digital relay system is adopted, and the internal elements of the capacitor of the harmonic filter equipment are In addition to failures, it can also be used to prevent current reduction due to ground faults or disconnections in harmonic filter equipment, or short circuits, ground faults, or disconnections on the secondary side of current transformers, which are the current detection means in relays. The purpose of the present invention is to provide a protection relay for harmonic filter equipment that can reliably detect and respond to a faulty branch.

[0013]

[Means for Solving the Problems] To achieve the above object, the harmonic filter equipment protection relay of the present invention includes a current detecting means for detecting the current flowing into each shunt, and a current detecting means for detecting the current flowing into each shunt. fundamental wave extraction means for determining the fundamental wave current value based on the fundamental wave extraction means; a first determination means for determining an increase in the flowing current; and a first determination means provided for each shunt, which detects the shunt based on the change in the fundamental wave difference current between the shunt and other shunts calculated by the fundamental wave extraction means. a second determination means for determining a decrease in the current flowing through the first determination means; a first trip command output means for outputting a trip command signal based on a determination output of the first determination means;
a second trip command output means for outputting a trip command signal based on the determination output of the determination means;
The trip command output means and the second trip command output means both operate in a timed manner, and the judgment value for the judgment of the first judgment means is set to be smaller than the judgment value of the second judgment means. The operation time of the first trip command output means is set longer than the operation time of the second trip command output means.

[0014]

[Operation] According to the harmonic filter equipment protection relay configured as described above, first, the current flowing into each branch of the harmonic filter equipment is detected, and the fundamental wave component is extracted by the fundamental wave extracting means. Then, the difference current between the currents flowing between each shunt is determined based on the fundamental wave extracted by each fundamental wave extracting means.

Further, the first determining means detects an increase in the current in the shunt, and the second determining means detects a decrease in the current in the shunt. This makes it possible to directly detect faulty shunts even for faults where current decreases, such as ground faults and disconnection faults. In this case, in the case of a fault where the current increases, such as a capacitor element fault, the second determination means installed in the non-faulty shunt detects a decrease in the current in the shunt, and For a fault in which the current decreases, there is a possibility that the first determination means provided in the non-faulty shunt may detect an increase in the current in the shunt.

However, if the first trip command output means and the second trip command output means are made to operate in a timed manner,
The judgment value for the judgment of the first judgment means is made smaller than that of the second judgment means, and the operation time of the first trip command output means is made shorter than the operation time of the second trip command output means. By increasing the length (see Figure 2), the figure shows the operating range of the protective relay of the present invention.The change in the fundamental current rated value is used as a judgment value that is the operating sensitivity of the first judgment means and the second judgment means. The respective rates of change are shown as Pc and Pg, the operating time of the first trip command output means is shown as Tc, and the operating time of the second trip command output means is shown as Tg.), capacitor For faults where the current increases, such as internal element faults, the first determination means first detects the increase in current with high sensitivity and over a long period of time, and then detects faults where the current decreases, such as ground faults and disconnection faults. In contrast, since the second determining means detects the decrease in current in a short period of time, the possibility of double detection as described above can be avoided.

The reason why the operating sensitivity and operating time are changed in this way is that in the case of the above-mentioned open circuit faults and ground faults, the fault current will be large depending on the fault location, so it must be detected in a short time to prevent the fault from spreading. In contrast, the internal elements of a shunt capacitor are composed of many small-capacity capacitor elements connected in series and parallel, and the impedance decreases only slightly due to a failure of one element (short-circuit failure), so the current This is because the increase is small, it must be detected with high sensitivity, and it must be operated for a long time to avoid the influence of unnecessary operations due to transient phenomena in the system.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples will be explained in detail below with reference to the accompanying drawings showing examples. FIG. 1 shows the fifth branch 5L, the eleventh branch 11L,
It is a circuit diagram of filter circuits 2a-2d connected to 13th shunt 13L and HP shunt HPL, and a protection relay that protects each filter circuit 2a-2d.

Each of the filter circuits 2a to 2d is a series circuit consisting of a capacitor, a reactor, a resistor, and the like. The current flowing through the filter circuits 2a to 2d is connected to the current transformer 3.
a to 3d, each of which is detected by the fundamental wave extraction circuit 1a.
~1d is input. The fundamental wave extraction circuits 1a to 1d include a harmonic attenuation filter 11a that attenuates harmonic components of current.
~11d, and the time corresponding to one period of the fundamental wave is divided into equal intervals at fixed time intervals (in the example, it is divided into 12 equal parts.Of course, it is possible to divide the time into 12 equal parts.It goes without saying that it can be more or less than this) and sampled at each time point. Sampling circuits 12a to 12d, and an effective value calculation circuit that performs a square root calculation using a value obtained by adding the square value of the sampling value over a period of time to each sampling value acquired by the sampling circuits 12a to 12d. 13a to 13d.

The fundamental wave components obtained by the fundamental wave extraction circuits 1a to 1d are input to a judgment circuit 4 (operating as a difference current calculating means and a judgment means), and the judgment circuit 4 calculates the current flowing through each branch. An increase or decrease in the difference current of the fundamental wave component is determined according to a determination formula (described later). The output of the determination circuit 4 is processed by a logic circuit 5 (corresponding to trip command output means), and the logic circuit 5 outputs a trip command signal according to a certain standard.

The operation of the protection relay described above will be explained below. The sample values im sampled at each time point by the sampling circuits 12a to 12d enter the effective value calculation circuits 13a to 13d and are processed. To briefly explain the calculation processing method by the effective value calculation circuits 13a to 13d, at a certain point in time, past sampling values i0 to i
We take the sum of 11 squared, multiply it by 1/12, and take the square root. In other words, it is calculated using equation (1).

[0022]

[Math 1]

[0023] Using the effective value calculation of equation (1) above,
It is well known that when the current contains many fundamental wave components and few harmonic components, the magnitude of the fundamental wave I1 can be approximated with high accuracy by effective value calculation (for example, the fundamental wave and the fifth harmonic). Assuming that only harmonics exist, fundamental wave I1=1
00, 5th harmonic I5 = 3, the effective value is 100
．． 0450, which is almost equal to the fundamental wave component), so equation (1) can be regarded as an arithmetic expression for approximately extracting the magnitude of the fundamental wave component of the current.

[0024] Through this calculation, the fundamental wave component can be calculated using the values in one past cycle. below,
The fundamental wave component flowing through each branch path determined in this manner is expressed as I(i) (i=5, 11, 13, HP). The fundamental wave component flowing through each branch obtained in this way is
The signal is input to the determination circuit 4.

FIG. 3 is a block diagram of the determination circuit 4. The fundamental wave output I(5) of the fifth branch is the first judgment circuit 41, respectively.
a, enters the second judgment circuit 42a, and in both judgment circuits,
A comparison is made with the fundamental wave output I (11) of the 11th branch, the fundamental wave output I (13) of the 13th branch, and the fundamental wave output I (HP) of the HP branch. In this case, the determination formula in the first determination circuit 41a is the j-th branch (j = 5, 11, 13, HP)
Let Inj represent the fundamental wave current rating value in
= 11, 13, HP), then 〓ΔI5j≧I
It is n5×Pc/100. Here, In5 is the fundamental wave current rating value in the fifth branch as described above, and Pc is a value (%) corresponding to the rate of change of the fundamental wave current rating value for determining element failure. For example, if Pc = 5%, the above judgment formula indicates that the current in the fifth branch has increased by 5% or more of the fundamental wave current rating value of the fifth branch, with respect to the current in the j-th branch. It represents.

The results of the determination in the first determination circuit 41a are taken for the cases of j=11, j=13, and j=HP, so a total of three determination signals are output. Signals representing each judgment result are ↑511, ↑513, ↑5H
Display as P. Further, the determination formula in the second determination circuit 42a is ΔI5j≦−In5×Pg/100 (j=11
, 13, HP). Here, Pg is the value (%
), and Pg > Pc. For example, Pg
= 10%, the above judgment formula shows that the current in the fifth branch is
This indicates that the current in the jth branch is reduced by 10% or more of the rated value of the fundamental wave current in the fifth branch.

The results of the determination in the second determination circuit 42a are also taken for j=11, j=13, and j=HP, so a total of three determination signals are output. Signals representing each judgment result ↓511, ↓51
3.Display at ↓5HP. The above explanation was for the first judgment circuit 41a and the second judgment circuit 42a for judging the current of the fifth branch, but the fundamental wave output of the eleventh branch and the fundamental wave of the thirteenth branch are Also when determining the fundamental wave output of the output 13 and the HP branch, a first determination circuit and a second determination circuit are provided, respectively (not shown). The operating equations of each determination circuit can be expressed in the same way as in the above case, so their description will be omitted. Each judgment result is ↑115, ↑1113
,↑11HP,↓115 ,↓1113,↓11HP,
↑135, ↑1311, ↑13HP, ↓135, ↓
1311, ↓13HP, ↑HP5, ↑HP11, ↑H
Represented by P13, ↓HP5, ↓HP11, ↓HP13.

FIG. 4 is a detailed diagram of the logic circuit 5.
A combination of the circuit shown in (a) and the circuit shown in (b) of the same figure constitutes the logic circuit 5. Each judgment signal ↑511, ↑513, ↑5HP obtained as a result of the first judgment is as shown in Fig. 4(a).
3 and ↑5HP, and ↑5HP and ↑513, which form three pairs and input to AND circuits 50a, 51a, and 52a, respectively.
The outputs of the AND circuits 50a, 51a, 52a enter the OR circuit 53a, and the signal output from the OR circuit 53a is sent to the time limit T.
The signal is outputted to the outside as a capacitor internal element failure detection signal through a timer circuit 54a having a timer circuit 54a. In addition, other judgment signals ↑115, ↑1113, ↑11HP, ↑135
,↑1311,↑13HP,↑HP5 ,↑HP11,
↑HP13 also has AND circuits 50b to 52b, 50c
~52c, 50d~52d, OR circuit 53b~5
3d, it is outputted to the outside as a capacitor internal element failure detection signal through the timer circuits 54b to 54d. As a result,
The 5th shunt capacitor internal element failure detection signal, the 11th shunt capacitor internal element failure detection signal, the 13th shunt capacitor internal element failure detection signal, and the HP shunt capacitor internal element failure detection signal are output from the four timer circuits 54a to 54d, respectively. I get a signal.

[0029] Also, as shown in Fig. 4(b), the respective judgment signals ↓511, ↓513, ↓5HP obtained as a result of the second judgment are ↓511 and ↓513, ↓513 and ↓5HP, ↓5.
HP and ↓513 form three pairs and enter AND circuits 55a, 56a, 57a, respectively, and each AND circuit 55a,
The outputs of 56a and 57a enter the OR circuit 58a and
The signal output from circuit 58a is sent to time limit circuit 5 with time limit Tg.
It is outputted to the outside through 9a as a ground fault/disconnection failure detection signal within the filter equipment. Also, other judgment signals ↓115
,↓1113,↓11HP,↓135 ,↓1311
, ↓13HP, ↓HP5 , ↓HP11, ↓HP13 are similarly AND circuits 55b to 57b, 55c to 57c, 5
5d to 57d, and is output to the outside through OR circuits 58b to 58d and time limit circuits 59b to 59d as a ground fault/disconnection failure detection signal in the filter equipment. As a result, from the four timer circuits 59a to 59d, the fifth alley fault and
A disconnection fault detection signal, an 11th branch alley fault/disconnection fault detection signal, a 13th branch alley fault/disconnection fault detection signal, and a HP branch alley fault/disconnection fault detection signal are obtained.

To explain the operation of the above logic circuit, first, when the internal element of the capacitor in one shunt (referred to as the i-th shunt) fails, a determination signal ↑ij is output from the first determination circuit 41a of that shunt. Since three (j≠i) are output, the AND circuit of that branch is sure to operate, and the output of the OR circuit appears. Therefore, if the output continues for more than time Tc,
An output can be produced from a timed circuit.

At this time, the second judgment circuit 42a of the other branch may also operate and output the judgment signal ↓ji, but since the AND circuit of the other branch does not operate, there is no possibility of outputting an erroneous signal. do not have. In addition, when there is a ground fault or disconnection fault in one shunt (referred to as the i-branch), three determination signals ↓ij (j≠i) are output from the second determination circuit 42a of that shunt, so an AND circuit is used. always operates, and the output of the OR circuit appears. Therefore, if the output continues for the time Tg or longer, the output of the time limit circuit can be output. At this time, the first judgment circuit 41a of the other branch may also operate and output the judgment signal ↑ji, but since the AND circuit does not operate, no erroneous signal will be output, as in the case above. be.

Next, when the internal elements of the capacitors in the two branches (referred to as the i-th branch and the j-th branch) simultaneously fail, a judgment signal ↑ik (k≠i , k≠
Since two j) are output, the AND circuit operates and the output of the OR circuit appears. Also, two judgment signals ↑jk (k≠j, k≠i) are output from the first judgment circuit of the j-th branch, so
The AND circuit of the branch operates, and the output of the OR circuit appears. Therefore, both the i-th branch capacitor internal element failure detection signal and the j-th branch capacitor internal element failure detection signal are output, indicating that there is a failure in the capacitor internal elements of both branches.

[0033] Furthermore, the judgment signal ↓ki is also sent from the second judgment circuit.
(k≠i, k≠j), ↓kj (k≠i, k≠j)
will be output, and the AND circuit of the shunts other than i and j will be 2
However, since the rate of change Pg of the fundamental wave current rated value for detecting ground faults and disconnections is set larger than Pc, A capacitor internal element failure detection signal appears. therefore,
There is no risk of it being judged as a ground fault or disconnection.

Next, when there is a ground fault or disconnection fault in the two branches (referred to as the i-th branch and the j-th branch), the judgment signal ↓ik (k≠i , k≠j), the AND circuit always operates and the output of the OR circuit appears. In addition, the judgment signal ↓ is also output from the second judgment circuit of the j-th branch.
Since two jk (k≠j, k≠i) are output, the AND circuit of the branch always operates, and the output of the OR circuit appears. Therefore, both the first branch ground fault/disconnection fault detection signal and the j-th branch ground fault/disconnection fault detection signal are output, indicating that there is a ground fault/disconnection fault in both branches. At this time, the first judgment circuit also sends a judgment signal ↑ki (k≠i, k≠j
), ↑kj (k≠i, k≠j) will appear,
Two AND circuits for the shunts other than i and j will work, and a capacitor internal element failure signal for the shunts other than i and j will be output. Since the time limit is shorter than Tc, ground faults and
The disconnection detection signal appears first, and it is not determined that there is a failure in the capacitor's internal elements.

Tables 1 to 4 summarize the above results. Table 1 is for a capacitor internal element failure in 1 branch, Table 2 is for a 2 branch capacitor internal element failure, Table 3 is for a ground fault or disconnection failure in 1 branch, and Table 4 is for a 2 branch capacitor internal element failure. This shows the case of ground fault/disconnection fault. In the table, ◎ indicates the judgment output of the judgment circuit, × indicates the non-judgment output of the judgment circuit, and ○ indicates the judgment output of the judgment circuit, but as mentioned above, Pg >
Since Pc and Tg < Tc, this shows a case that does not actually appear as an output. Note that in Tables 1 to 4, a 1-shunt failure occurs only in the 5th branch, and a 2-shunt failure occurs between the 5th and 11th branches.
Failures in other shunts can be considered in exactly the same way.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

It should be noted that the present invention is not limited to the above-described embodiments; for example, instead of performing effective value calculation to obtain the fundamental wave component, the fundamental wave component may be obtained by Fourier integral method or the like. Various other design changes can be made without changing the gist of the present invention.

[0041]

As described above, according to the harmonic filter equipment protection relay of the present invention, the current flowing into each shunt of the harmonic filter equipment is detected, the fundamental wave component is determined, and then the shunt is By calculating the increase and decrease in the flowing current separately in the form of the difference from the current in other shunts, and applying different judgment values and time limits to each, it is possible to detect failures in internal elements of capacitors and ground faults in filter equipment. - It is possible to realize a protection relay that responds accurately to any failure such as disconnection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a specific configuration of a harmonic filter equipment protection relay.

FIG. 2 is a graph showing the operating range of a harmonic filter equipment protection relay.

FIG. 3 is a block diagram showing the internal configuration of a determination circuit.

FIG. 4 is a circuit diagram showing the internal configuration of a logic circuit.

FIG. 5 is a circuit diagram showing a conventional analog harmonic filter equipment protection relay.

[Explanation of symbols]

1a-1d Fundamental wave extraction circuit 2a-2d filter 3a-3d Current transformer 4 Judgment circuit 5 Logic circuit 11a-11d Harmonic attenuation circuit 12a-12d Sampling circuit 13a to 13d Effective value calculation circuit 41a First judgment circuit 41b Second judgment circuit

Claims (1)

[Claims] [Claim 1] A relay that protects harmonic filter equipment by detecting the same-phase fundamental wave difference current between harmonic shunts of harmonic filter equipment, which detects the current flowing into each shunt. A current detecting means, a fundamental wave extracting means for determining a fundamental wave current value based on the detected current of the current detecting means, and a means for connecting the shunt and other shunts, which are provided in each shunt and calculated by the fundamental wave extracting means. a first determination means for determining an increase in the current flowing through the shunt from a change in the fundamental wave difference current of the shunt; and a first trip command output that outputs a trip command signal based on the determination output of the first determination means. and a second trip command output means for outputting a trip command signal based on the determination output of the second determination means, the first trip command output means and the second trip command output means both having a time limit. The judgment value for the judgment of the first judgment means is set smaller than the judgment value of the second judgment means, and the operation time of the first trip command output means is set to be smaller than the judgment value of the second judgment means. A harmonic filter equipment protection relay characterized in that the operating time of the trip command output means of item 2 is set longer.