JPS5812811B2 - 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 double bus system. 1 is the bus, 2 is the generator, 3 is the load, 4 is the bus connection line, and 5 is the connection connecting the generator 2 and bus 1 or the load 3 and bus 1. line, 6 is a breaker, 7 is a disconnector, and the connection point between each connection line 5 and bus 1 is bus 1
is divided into multiple bus sections.

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

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 current values only from active power flow, but in bus systems where power flow fluctuates greatly during system operation, a simple measurement method with a constant power factor cannot provide accurate measurements. I couldn't wait.

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 FIG. 2, 8 is a current transformer CT installed on each connection line, and 9 is a voltage transformer PT installed on the bus bar.

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

10 is a power factor measuring device that measures from the output of PT9 and the output of CT8 for each connection line, 11 is an active power measuring device that measures from the output of PT9 and the output of CT8 for each connection line, and 12 is an active power A reactive power conversion device that calculates reactive power from the output of the measuring device 11 and the output of the power factor measuring device 10, 13 and 14 are active power calculation devices and reactive power calculation devices, respectively, B1 to B
Reference numeral 3 denotes each bus bar section divided by connection points between the bus bar and each connection line, and L1 to L4 are power lines connecting the generator 2 and the bus bar 1 or load lines connecting the load 3 and the bus line 1.

Reference numeral 15 denotes an effective current calculation device that calculates a current value from the outputs of the active power calculation device 13 and the reactive power calculation device 14.

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.

The reactive power Q2 of the connection line L2 is the active power P2 of that connection line.
From the power factor cosθ2, Q2=P2√1−coc2θ2/COSθ2...
...Calculated using (1).

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

X2-X1-P2=P1-P2...
(2) Y2=YI-Q2=Q1=Q2...
(3) Here, X1 and X1 are the active power and reactive power of the bus section B1, P1 and Q1 are the active power and reactive power of the connection line L1, and P2 and Q2 are the active power of the connection line L2. No, it is effective power.

The above Q1 is calculated from P1 and cos θ1 according to equation (1).

Next is the active power flowing into the bus. Considering reactive power as positive direction and generalizing equations (2) and (3), XK= Σ PJ...
・(4) J21 YK= Σ QJ ・・・・・
・(5) J=l QJ−=PJ 1−cos”&J cosθJ ・−
...-(6) is obtained.

PJ, QJ are the active power and reactive power of the j-th connection line counting from the end of the bus, XK, YK are the active power and reactive power of the K-th bus section, and cos θJ is the force of the j-th connection line. rate.

Equations (4) and (5) mean that "the active power and reactive power of any bus section are all the power up to one end of that bus section? They are the algebraic sum of the active power and reactive power of the connecting line." It means.

Therefore, the active power and reactive power of each busbar section should not be measured directly, but the measured values of the active power and power factor of each connection line should be input to the above-mentioned reactive power converter, active power calculation device, and reactive power calculation device. It can be calculated and measured by

Next, in FIG. 2, if it is a Sanwa 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 (6).

J “F-cho〒1T IK=・・・・・・(6) J'W Here ■ is the bus voltage.

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

According to this invention, since the current value is calculated by calculation from the active power and reactive power of each bus section, it is possible to always accurately measure the current value for any bus power flow during system operation.

Since an active power measuring device and a power factor measuring device are often installed on each of the above-mentioned connection lines, the present invention is highly effective in terms of cost.

As explained above, in this invention, the active power and reactive power of each bus section are calculated based on the active power of each connection line and the algebraic sum of the reactive power calculated from the active power and power factor. There is no need to install a CT in each busbar section to directly measure the current value, and the current value in any busbar section can be measured without complicating the busbar configuration.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a double bus system, and Fig. 2 is a system diagram showing an embodiment of the present invention.
2 is a generator, 3 is a load, 6 is a breaker, 8 is a current transformer (C
T), 9 is a potential transformer (PT), 10 is a power factor measuring device,
11 is an active power measuring device, 12 is a reactive power converter, 13
14 is an active power calculation device, 14 is a reactive power calculation device, 15 is an effective current calculation device, L1 to L4 are connection lines, and B1 to B3 are busbar sections. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Claims] 1 Active power measurement that measures the size and direction of the power flow flowing through the connection lines that connect the bus and the power supply or the bus and the load, the bus section divided by the connection points between the bus and each of the above connection lines, and each of the above connection lines. A power factor measuring device that measures the power factor of the power flow flowing through each of the above connection lines, and a reactive power that calculates the magnitude and direction of the reactive power flowing through each connection line from the outputs of the above active power measurement device and power factor measurement device. The converter calculates the algebraic sum of the active power of the section at one end of the bus bar and the active power of the connecting line at the other end of that section, and calculates the algebraic sum and the effective power of the connecting line at the other end of the next bus section of the bus bar section. An active power calculation device that calculates the algebraic sum of the power and then sequentially calculates the algebraic sum of the active power of the connection line at the other end of the next bus section, and the reactive power of the section of one end of the bus bar and the active power of the other end of that section. Calculate the algebraic sum of the reactive power of the connecting line, and calculate 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 calculate the connection at the other end of the next bus section. It is equipped with a reactive power calculation device that takes an algebraic sum with the reactive power of the line, and an effective current calculation device that calculates the magnitude of the current from the outputs of the above-mentioned active power calculation device and reactive power calculation device, and calculates the current value in a predetermined bus section. A bus current measuring device that performs calculation and measurement based on the algebraic sum of active power and the algebraic sum of reactive power of a connecting line up to one end of the section.