JPS5812812B2 - Bosenden Ryuusokutei Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that can accurately and easily measure bus current.

Figure 1 is a system diagram showing a 15BC bus system, where 1 is the bus, 2 is the generator, 3 is the load, 4 is the bus connection line, and 5 is the generator 2 and bus connection line 4 or the load 3 and the bus connection line 4. 6 is a circuit breaker for the busbar connection line, 7 is a disconnector, and the connection point between the busbar connection line and the busbar divides the busbar into multiple busbar sections, and also the connection line and the busbar connection line. The connection points divide the bus line into three sections.

In Figure 1, depending on the load condition during system operation, a current exceeding the allowable bus current value may flow in only a specific bus section, leading to a dangerous situation, so it is necessary to monitor the current value in all bus sections. Ta.

Installing CTs in all busbar sections to directly measure current values for the above purpose only unnecessarily complicates the busbar components and is not desirable in terms of cost.

Conventionally, devices have been considered that calculate and measure the current value only from the active power flow, but in ultra-high voltage bus systems like the one shown in Figure 1, the power flow fluctuates greatly during operation, so it is difficult to maintain the power factor at a constant value. Accurate measurements could not be expected with the simple measurement method used.

This invention takes the above points into consideration and attempts to accurately measure the current in each bus section without directly measuring all the currents in each bus section.

FIG. 2 shows an embodiment of the present invention, which is applied to a single bus system for the sake of explanation.

Furthermore, the application can be easily extended to other bus system systems such as a double bus system.

In Figure 2, 8 is a potential current transformer (CT) installed on each connection line, and 9 is a potential transformer (PT) installed on the bus bar.
It is.

Both CT8 and PT9 that are normally installed in the bus system can be used.

10 and 11 are active power measuring instruments and reactive power waste detectors that measure from the output of PT9 and the output of CT8 for each connection line;
12 and 13 are an active power calculation device and a reactive power calculation device, respectively, B1 to B5 are bus sections divided by connection points between the bus and each connection line, and L1 to L6 are generator 2 and bus 1.
This is a power line that connects the load 3 and the bus 1 or a load line that connects the load 3 and the bus 1.

Reference numeral 14 denotes an effective current calculation device that calculates a current value from the outputs of the active power calculation device 12 and the reactive power calculation device 13.

In the following explanation, it is assumed that there is no power loss in the bus bar.

Let us now calculate the active power X2 and reactive power Y2 flowing through the bus section B2.

At the connection point between the connection line L2 and the bus bar, the following equation holds true according to Kirchhoff's law.

X2=X1-P2=P1-P2 (1)
Y2=Y1-TQ2-Q1-Q2 (2
) Here, X1, Y1 are the active power and reactive power of the bus section B1, and P1, Q1 are the active power and reactive power P2 of the connection line L1.
, Q2 are the active power and reactive power of the connection line L2.

Next, assuming that the active power and reactive power flowing into the bus bar are in the positive direction, and generalizing equations (1) and (2), X - ΣP
J ・・・・・・(3) K−J−1 YK= ΣQJ ・・・・・・(4) J=
1 is obtained.

PJ and QJ are the active power and reactive power of the j-th connection line counting from the end of the bus, and XK and YK are the active power and reactive power of the k-th bus section.

Equations (3) and (4) indicate that "the active power and reactive power of any bus section are the algebraic sum of the active power and reactive power of all connecting lines up to one end of that bus section." It means.

Therefore, the active power and reactive power of each busbar section can be calculated and measured by inputting the measured values of the active power and reactive power of each connection line to the above-mentioned active power calculation device and reactive power calculation device, without directly measuring them. I can do it.

Next, in FIG. 2, if it is a three-phase bus and the bus voltage is equal in all bus sections, the current IK in the k-th bus section is given by the following equation (5).

Here, ■ is the bus voltage.

With the above steps, the current value in each bus section can be determined.

According to this invention, since the current value is calculated by calculation from the active power flow and reactive power flow in each bus section, accurate values can always be measured even if fluctuations occur in the bus power flow during system operation.

Therefore, it can be applied to any bus in the power system.

This device is especially suitable for application to ultra-high pressure systems where busbar power flow fluctuates significantly.

As described above, in this invention, the active power and reactive power of each bus section are calculated based on the algebraic sum of the active power and reactive power of each connection line.
There is no need to install a T for direct measurement, and the current value in any busbar section can be measured without complicating the busbar configuration.

[Brief explanation of the drawing]

Figure 1 shows 1. 5 CB system diagram showing the bus system,
FIG. 2 is a system diagram showing an embodiment of the present invention. In the figure, 1 is a busbar, 2 is a generator, 3 is a load, 4 is a busbar connection line, 5 is a connection line, and 6 is for a busbar connection line. breaker, 7 is a disconnector, 8 is a current transformer (CT), 9 is a potential transformer (PT)
, 10 is an active power measuring device, 11 is a reactive power measuring device, 12
13 is an active power calculation device, 13 is a reactive power calculation device, 14 is an effective current calculation device, L1 to L6 are connection lines, and B1 to B5 are busbar sections. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1. The magnitude and direction of the active power flow and reactive power flow flowing through the connection lines that connect the bus and the power source or the bus and the load, the bus sections divided by the connection points between the bus and each of the above connection lines, and each of the above connection lines. Use the active power measuring device and reactive power measuring device to determine the algebraic sum of the active power in the section at one end of the above bus line and the active power of the connecting line at the other end of that section, and calculate the algebraic sum and the next power of the above bus section. An active power calculation device that calculates the algebraic sum of the active power of the connecting line at the other end of the bus section, and then sequentially calculates the algebraic sum of the active power of the connecting line at the other end of the next bus section, the section at one end of the bus bar. Take the algebraic sum of the reactive power of and the reactive power of the connecting line at the other end of that section, then take the algebraic sum of this algebraic sum and the reactive power of the connecting line at the other end of the next bus section of the above bus section, and then sequentially. A reactive power calculation device that calculates the algebraic sum of the reactive power of the connecting line at the other end of the next bus section, and an effective current calculation device that calculates the magnitude of the current value from the outputs of the above-mentioned active power calculation device and reactive power calculation device. A bus bar current measuring device that calculates and measures a current value in a predetermined bus section based on an algebraic sum of active power and an algebraic sum of reactive power of a connecting line up to one end of the bus bar section.