JPH0728505B2 - Automatic control system for power distribution equipment - Google Patents

Description

The present invention relates to an automatic control system for power distribution equipment.

Conventionally, the decision on whether to switch the loop connected to power distribution equipment was made by the substation operator.Therefore, it is not an accurate judgment and the power is switched unnecessarily for safety reasons or the loop switching is forced. I was trying to do a power outage.

The present invention has been made in view of the above points, and a computer automatically and accurately determines whether or not to switch a loop in which a power distribution device is connected, and controls the power distribution device so that at least the power failure section is affected by the power failure period. The purpose is to provide an automatic control system of.

Prior to the description of the embodiments of the present invention, loop switching and power failure switching will be described below.

Loop switching means, for example, in FIG. 1 (a), the load of the feeder F ₁ is applied to the load of the feeder F ₂ to inspect the circuit breaker.
When power is to be exchanged from Fig. 2 (b), first connect interconnection switch VI to form a loop, and then open the breaker of feeder F ₁ as shown in Fig. 2 (c). It is a switching method that allows power to be exchanged from feeder F ₂ to feeder F ₁ . By doing this, the load on the feeder F ₁ can be switched without interruption. Where T is the transformer of the intermediate substation, VCB ₁ and VCB ₂ are circuit breakers, VI ₁ and VI ₂ are switchgear,
VI is the interconnection switch described above, and F ₁ and F ₂ are feeders.

On the other hand, the power failure switching method is a method in which the circuit breaker VCB ₁ of the feeder F ₁ is _first opened as shown in FIG. 4D, and then the interconnection switch VI is closed as shown in FIG. In this case, the load of the feeder F ₁ (customer) is temporarily cut off as shown in FIG. That is, the section indicated by the dotted line R has a power failure.

By the way, conditions are required for loop switching, and switching of distribution lines requires the active power reactive power to be changed by the voltage difference and voltage phase difference between the open devices that are closed or opened by opening the loop, as in the ultra-high voltage system. There is no significant sway, which does not impact the generator or cause any abnormalities in the equipment inside the power plant. However, for example, a voltage difference or a phase difference between both ends of the interconnection switch in FIG. 1 may cause a large current to flow when the loop is closed or open, which may cause the protection relay (overcurrent relay or the like) to malfunction. Therefore, the loop switching condition is that a large current that operates the protection relay does not flow when the loop is closed or opened. Conventionally, the operator determines the switching condition as described above, and FIG. 2 shows examples of various power distribution systems.

In the figure, T _A is the intermediate substation transformer, l is feeder (transmission line), Tg is distribution substation main transformer, g denotes the power distribution station, respectively.

In the case of the system configuration of FIG. 2 (a), normal loop switching is possible, and in the case of FIG. 2 (d), the system is independent,
Loop switching is not possible. In addition, FIG.
In the case of (c), it is determined that the loop switching is possible when a certain specific condition is satisfied. In that case, the loop switching condition is determined as follows.

That is, of the determination parameters for loop switching in the system,
Select the sum of the lengths of the distribution lines subject to looping and the larger pre-current of the distribution line to be looped, with the former as the horizontal axis and the larger pre-current flowing in the latter loop as the vertical axis,
The determination is made depending on whether or not the area is in a loop switchable area.

With the above method, it is impossible to predict the correct current after loop opening and loop opening. Therefore, if the switching is attempted for safety reasons, a power outage switching will be performed and the service to the customer will be deteriorated. In addition, if the circuit breaker is opened due to the protection relay operation after the switch is turned on due to a wrong prediction, a temporary power outage and temporary confusion will result.

The present invention is characterized by automatically determining whether or not loop switching is possible by a computer instead of the above-described determination method, and one embodiment thereof will be described below with reference to the accompanying drawings.

For example, if the voltage and current in each loop are as shown in FIG. 4 (a) by taking the system configuration shown in FIG. 2 (b) as an example, the distribution line as shown in FIG. 4 (b) is used. the current I flowing through the interconnection switch for loop-up when the loop is turned on I ₌ calculated as _{(V a -V B) / Z} ... (1). Here, Z is the impedance of the loop when the system is viewed from the input point.

Generally, it is difficult to find the voltage at the installation point of the interconnecting switch of the distribution line, but if the voltages V ₁ and V ₂ at the substation bus and the currents I ₁ and I ₂ flowing through the feeder before loop insertion are known, V
_A and V _B are respectively obtained from the following equations.

V _A = V ₁ −Z ₁ · I ₁ …… (2) V _B = V ₂ −Z ₂ · I ₂ …… (3) where Z ₁ and Z ₂ are the distribution lines from the point of view of the system. Impedance.

FIG. 5 shows a flow of the embodiment of the present invention, and this embodiment shows the condition judgment of the loop insertion in FIG. 4, and when the loop is opened from the state of FIG. when flexibility from the lower side of the bank is feeder, feeder current I becomes _{I = V 2 / (Z L} + Z 2) ...... (4). However, _{Z L} denotes a load impedance.

In addition, at the time of accommodation, more accurate prediction can be made by considering the impedance value on the upstream side of the substation, but in order to do so, it is necessary to grasp the upstream side system configuration, and it is assumed that it is a voltage source. You must enter the voltage value of the bus to be used. That is, it is necessary to transmit the open / closed state of the circuit breaker in the distant place, the substation bus voltage in the distant place, and the device configuration becomes extremely complicated.

In the above formula (4), V ₂ is not the voltage source, but V ₂
It is also assumed that the value of does not fluctuate significantly before and after the loop is opened, and by using the measured value of the bus voltage of the distribution substation before the loop is opened, the switching condition can be determined practically and accurately. .

That is, in FIG. 5, the substation bus voltage and the input feeder current are input as shown by 10 and the distribution line type, long load impedance, etc. are taken out from the data base as shown by 20, and shown by 30. Calculate the impedance of each distribution line and the impedance seen from the interconnection point, and calculate the current I after making it as shown in 40, and determine in 50 whether this current I does not exceed the set value K. If the current I does not exceed the settling value K, the loop switching is determined to be impossible and the loop switching is determined to be impossible, as indicated by 60.

When the loop is opened, the current at the time of opening the loop is calculated by the equation (4), and the judgment is made by 50.

Since the embodiment of the present invention is configured as described above, it has the following effects.

(1) Since the computer calculates and predicts the current after control using the voltage of the distribution substation bus, feeder current, distribution line impedance, and load impedance, the switching conditions can be accurately determined.

(2) As described in the item (1) above, the determination of the switching condition can be accurately performed, so that the chances of loop switching increase, the blackout section, that is, the blackout time is eliminated, and the service to the consumer is improved.

(3) Similarly, since the switching condition can be accurately determined as in the above item (1), it is possible to avoid unnecessary confusion such as a protection relay operation due to a prediction error.

(4) Workers do not directly go to the site where the switchgear is installed, and automatically control the power distribution equipment, so the control becomes quicker, the risk of overload is reduced, and power failure switching or distribution line work stoppage occurs. In this case, the power outage time can be reduced.

Although the above embodiment does not mention the case of overload of the distribution line or the bank, these cases also need to be considered practically. Further, the above-described switching embodiment has been described with reference to the case shown in FIG. 2B, but it is needless to say that the same determination can be made with respect to FIGS.

As described above, the automatic control method of the power distribution device according to the present invention is based on the distribution substation bus voltage, the corresponding feeder current, the corresponding distribution line impedance, and the corresponding load impedance. Since it is possible to predict whether or not the loop switching is possible by accurately calculating, it is possible to accurately determine the switching condition, and it is possible to increase the chances of the loop switching, so that it is possible to reduce the power failure section. .

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram showing loop switching and power failure switching, FIGS. 2 (a) to (d) show various system configuration examples, and FIG. 3 shows whether loop switching is possible or not. FIG. 4 (a) is a schematic circuit diagram showing calculation of the feeder current in the system configuration shown in FIG. 2 (b), and FIG. 4 (b) is a loop input. FIG. 4 (c) is an explanatory diagram showing a state when the loop is opened, and FIG. 5 is a flow of the automatic control system of the power distribution device according to the present invention. T _A …… Intermediate substation transformer, l …… Transmission line, Tg …… Distribution substation main transformer, g …… Distribution line.

Claims (1)

[Claims] 1. In a control method of a distribution device that performs loop opening and loop opening in a distribution system, when system switching is required due to work stoppage, accident, etc., the distribution substation bus voltage, corresponding feeder current, and corresponding Predictive calculation of the feeder current due to system switching when the loop is closed and when the loop is opened is calculated based on the impedance of the distribution line and the corresponding load impedance, and it is determined whether this current value does not exceed the preset value. An automatic control method for power distribution equipment, which sometimes performs loop switching.