JPS5812814B2 - Bus bar protection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to protecting busbars from accidents by digitally processing voltage and current information obtained from a power system using an electronic computer, and particularly relates to a busbar protection system using a double busbar configuration.

Figure 1 shows the well-known double busbar 4 bus tie system.
In Figure 1, 1.2 is the A bus line and the A b bus line, 3
, 4 are Otsu a bus line and Otsu b bus line, 5a, 5b,...
...5n is the power transmission line, 6a, 6b...6m is the current transformer installed on the power transmission line 5a, 5b...5m, 7a, 7b is A. 8 is a current transformer installed on the Otsu bus line, 9 is a current transformer installed on the Aotsu bus connecting line;
a, 9b are circuit breakers, 10a to 10n, 11a to 11n
is a disconnector.

Next, a conventional means for protecting the A bus 1 and the O A bus 3 of the double bus 4 bus tie system shown in FIG. 1 will be described.

The protection of the A bus 1 is based on the data of the current transformers 7a and 8, and as shown in FIG.
(when the disconnector 10a is closed and the disconnector 11a is open) is applied to the A bus bar protection relay 12a.

That is, based on the above data, a well-known current differential method is used to detect an accident that has occurred on the A bus 1, and to connect circuit breakers 9a, 9b shown in FIG. Protection is achieved by operating a circuit breaker to shut off the power.

Further, the protection of the Otsu-a bus 3 can be performed in the same manner as described above using the data of the current transformers 7b and 8 and the current transformer of the power transmission line connected to the Otsu-a bus.

In the above bus bar protection method, unless the current data to be used by the protective relay is changed according to the opening/closing conditions of the disconnect switch, it is not possible to immediately determine which bus bar (A) and (B) has an accident.

For this reason, busbar protection has the disadvantage that the reliability of protection is lower than that of power transmission line protection and the like.

The present invention eliminates the above-mentioned drawbacks and can improve the reliability of protection by determining in a short time which busbar of a double busbar an accident has occurred without using the opening/closing conditions of the disconnector. The purpose is to provide a busbar protection method.

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 4, the same parts as in FIG. 1 are designated by the same reference numerals.

Current transformers 6a to 6n arranged on power transmission lines 5a to 5n
The analog quantities obtained from the A-D converters 13a to 13n
is converted into a digital quantity and supplied to the batch difference current (ID1) calculation circuit 14.

This arithmetic circuit 14 also includes the analog quantities of the current transformers 7a and 7b arranged on the A/B bus 2.4 as well as the A-D converter 15a.
, 15b, it is converted into a digital quantity and supplied.

The arithmetic circuit 14 performs an arithmetic operation for collectively calculating the vector sum of the digital quantities of the A-D converters 13a to 13n and 15a, 15b.

The obtained calculation output is supplied to a calculation circuit which will be described later.

Reference numeral 16 denotes an A-D transformer that converts the analog quantity of the current transformer 8 into a digital quantity.
) is supplied to each input of the arithmetic circuit 18.

Both of these arithmetic circuits 17 and 18 include an A-D converter 15a.
, 15b are supplied separately.

19 is a circuit for changing the power transmission line connection state; this changing circuit 1
The outputs of the A/D converters 13a to 13n are supplied to the input of the circuit 9, and the outputs are input to the arithmetic circuits 17 and 18.

Note that the output of the change circuit 19 is controlled by a determination circuit described later.

The output of the ID1 arithmetic circuit 14 is calculated by the sum output of the ID2 and ID3 arithmetic circuits 17, 18 and the arithmetic circuit 20.

This addition is calculated to obtain the absolute value of ID1-(ID2+ID3).

A determination circuit 21 that determines whether the output calculated by this calculation circuit 3 is thicker or smaller than a predetermined set value Ko.
is supplied to

When this judgment circuit 21 judges that the output is larger than the set value Ko, it gives a change signal to the change circuit 19, and when it judges that it is smaller than the set value Ko, it gives an output to the comparison circuit 22.

Comparison circuit 22 compares ID2 and ID3, and if the comparison result is smaller than a predetermined value, it sends out an output to be given to a protection arithmetic unit (not shown).

The protection arithmetic unit starts a computation based on the output.

This calculation is performed, for example, on the differential principle of busbar protection relays.

Next, the operation of the above embodiment will be described.

A-B buses 1 to 4 and power transmission lines 5a, 5b...5
Current information of n is current transformers 6a, 5b...
6n, 7a, and 7b, and the information obtained is A-
D converters 13a, 13b...l5n and 15a, 1
5b, it is converted into a digital quantity and calculated by the collective difference current ID1 calculation circuit 14 to obtain a vector sum.

This vector sum (ID1) is given to the arithmetic circuit 20.

The digital values of the A-D converters 13a, 13b, .

The arithmetic circuits 17 and 18 are input with the current information of the current transformer 8 converted into digital quantities by the A-D converter 8, as well as the digital quantities of the A-D converters 18ap15b. Each item is entered separately.

Vector sum ID2 obtained by the above calculation circuits 17 and 18
;ID3 is calculated by the calculation circuit 20 as shown in the following equation.

|ID1-(ID2+ID3)|=|IDo|This|I
Do| That is, the determination circuit 21 determines whether the scalar amount IDo is larger or smaller than a predetermined set value Ko.

Here, if there is no accident on either bus A or B, ID
1 is almost zero, and ID2 and ID3 are also connected to the power transmission lines 5a and 5.
b...If the assumption of the first bus line to which 5n is connected is correct, it will be approximately zero.

Therefore, |IDO| becomes approximately zero, |IDO| becomes smaller than the set value Ko, and the determination output of the determination circuit 21 is input to the comparison circuit 22.

This comparison circuit 22 compares D2 and ID3, and the protection arithmetic unit starts an arithmetic operation based on the result.

If the assumption of connection of the power transmission lines 5a, 5b, .

Therefore, |IDO| becomes larger than Ko, and a change signal is supplied from the determination circuit 21 to the change circuit 19.

In the flowchart of FIG. 4, this is the "NO" signal side.

The modification circuit 19 assumes the connection state of the power transmission lines 5a, 5b, .

In other words, before calculating ID2 and ID3, the power transmission line is
1, L2, L1, L2 are connected to A bus 1, and the others are connected to O bus 3, ID2, ID
However, the assumption was incorrect based on the judgment result of the judgment circuit 21, so the assumption of L1 was corrected, and the calculation of L1 was started.
1 is determined to be the Otsu a bus line 3.

Here, the calculation of the 1.D21 calculation circuit 17 is redone, and if the result of the judgment circuit 21 is IDO<Ko, the judgment output is inputted to the comparison circuit 22.

However, when IDO>Ko, a judgment output is input to the change circuit 19, and the assumption that L1 is the bus 3 of Otsu is connected to the bus 1 of Aa, and that L2 is connected to the bus 3 of Otsu. Assuming that it is, the calculation circuit 17 starts calculation again.

If this result is correct, the output of the judgment circuit 21 is
2 is input.

Note that the power transmission lines 5a, 5b, 5c, and 5d are four lines L.
Consisting of 1, L2, L3, and L4, there are the following 7 combinations if they are warped, and a total of 7 x 2-14 connections including the case where the A bus line and the O bus line are reversed. There is a condition.

Therefore, in the worst case, the calculation from ID2 in the flowchart will be performed 14 times.

As a result of the calculation as described above, when the output of the determination circuit 21 is input to the comparison circuit 22, the power transmission lines 5a, 5b, .
This means that it has been determined which bus bar 5n is connected to.

Therefore, the processing time from the calculation of ID2 to the comparison circuit 22 (
Since the connection of two or more lines is not changed at the same time (in μS order), it is not known when the transmission line will be switched and connected, so the judgment circuit 21 always detects the judgment result and A change signal is given to the change circuit 19 to cause the circuit 17 to perform the calculation.

For example, in the case of the above-mentioned power transmission lines L1 to L4, if you perform calculations by reversing the connection of only L1, returning L, and reversing L2, and perform calculations up to L4, judgment will be made in four cases. The circuit 21 inputs the judgment output to the comparison circuit 22.

Thereafter, when a change signal is sent out, the output is input to the comparator circuit 22 by repeating the calculation for the maximum number of power transmission lines.

As described above, the comparison circuit 22 compares ID2 and ID3 and sends out a signal indicating whether to start the protection calculation device or temporarily stop the protection calculation.

In the flowchart of FIG. 4, when the comparison circuit 22 sends out a "NO" signal, the disconnectors 10a to 10n, 11
Both a to 11n may temporarily be in a closed circuit state, and if the calculation is started in such a case, a malfunction may occur. Therefore, the calculation is temporarily stopped when the answer is "NO".

In addition to the above, if an internal accident occurs, ID1tID
Although neither ID2 nor ID3 becomes zero, the determination circuit 21 inputs its output to the comparison circuit 22 even during an internal accident.

Therefore, the output of the comparator circuit 22 allows the safety error calculation device to sufficiently determine the accident on the A/B bus, so there is no problem.

In addition, the above calculation time is several tens of μ to find |IDO|
Since it is S, the data update interval of about 1 to 2 ms is sufficient, and the power transmission line, etc. is sufficiently The flowchart of FIG. 4 for determining which bus line is connected can be fully executed and does not affect the operating time of the protection relay.

In the above embodiment, the case where there are four power transmission lines has been described as an example, but when the number of lines increases, it is necessary to increase the assumption that the lines are connected to the Aa and Otsua buses.

For this reason, there is a possibility that it may become unfeasible in terms of computer processing power.

In this case, it is possible to carry out the process by introducing the initial condition 23 in advance as shown in the flowchart of FIG.

This case will be briefly described below.

In other words, how are power transmission lines, transformers, etc. connected to the busbar to be protected?
5, 1, 2, 4, 7, 8, 9, 10 are connected to the A bus, and the rest are connected to the O A bus. When the above conditions are known in advance, the above conditions are entered at the beginning of the flowchart of FIG. 4 as the initial conditions for operation, and operation is started.

If operation is started under such conditions, the determination circuit 21 will input the determination output to the comparison circuit 22 at the beginning of the operation.

After the judgment circuit 21 sends out one judgment output, the judgment circuit 21 repeats the judgment output as many times as the number of connected lines and transformers.
By sending a change signal from the line, busbar protection can be achieved even if the connection state of the line etc. does not always use the opening/closing conditions of the disconnector.

As described above, according to the present invention, it is possible to quickly determine to which side a power transmission line, etc. is connected to a double bus bar without using the opening/closing conditions of a constant disconnect switch, and the protection of the bus bar is ensured. We can provide a busbar protection system that can

[Brief explanation of drawings]

Figures 1 and 2 are for describing conventional protection methods.
Fig. 1 is a circuit diagram of the double bus system, Fig. 2 is an explanatory circuit diagram for switching data on a power transmission line, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is the same as Fig. 3. It is a flowchart for explaining an effect. 13a, 13b--13n, 15a, 15b, 16
...A-D converter, 14...Bulk difference current calculation circuit, 17.18...Base A bus difference current calculation circuit, 19...Change Circuit, 20...
Arithmetic circuit, 21... Judgment circuit, 22...
・Comparison circuit.

Claims (1)

[Scope of Claims] 1. A first circuit that calculates a vector sum of currents obtained from a current detector disposed on each bus bar of a double bus bar and a current detector disposed on a power transmission line, and the current detection circuit second and third circuits that calculate, for each bus, the vector sum of the currents obtained from the current detectors disposed on the bus and the current detectors installed on each bus line, and the sum of the calculation outputs of the second and third circuits. a fourth circuit that calculates the difference between the calculation outputs of the first circuit; a fifth circuit that determines whether the calculation output of the fourth circuit is larger or smaller than a predetermined value; and a judgment result of the sixth circuit that is larger. Sometimes, a sixth circuit is provided with an output to change the connection state of the power transmission line using a current from a current detector of the power transmission line until the calculation outputs of the second and third circuits reach a predetermined value, and the determination result of the fifth circuit is When the difference is small, the seventh circuit compares the difference between the calculation outputs of the second and third circuits.
A busbar protection system comprising a circuit, and determining whether an accident has occurred in one of the double busbars based on the comparison result of the seventh circuit. 2. A circuit that detects in advance information on which bus the power transmission line is connected to, and the output detected by this circuit is installed in the current detector installed on each bus of the double bus and the power transmission line. A first circuit that calculates the vector sum of current obtained from the current detector and the current detector disposed on the current detector and each bus connecting line for each bus. A second and third circuit that performs calculations, a fourth circuit that produces the difference between the sum of the calculation outputs of the second and third circuits and the calculation output of the first circuit, and a calculation output of the fourth circuit that is a predetermined value. 5th step to determine whether it is larger or smaller than
circuit, and when the determination result of this fifth circuit is large, a current from a current detector of the power transmission line is used to provide an output to change the power transmission line connection state until the calculation outputs of the second and third circuits reach a predetermined value. 6 circuits, and a seventh circuit that compares the difference between the calculation outputs of the second and third circuits when the judgment result of the fifth circuit is small.
A busbar protection system characterized by determining whether an accident has occurred on any of the heavy busbars.