JPS5923173B2 - Cutoff load selection method in power safety equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cutoff load selection method in a power safety device.

More specifically, at least one
In a power system that supplies power from a power source to a load by commonly connecting one power source end and at least one load end connected to two loads, an accident such as a power source end falling off may occur, causing the power supply to fail.
. The present invention relates to a load cutoff selection method in a power safety system that selectively cuts off excessive loads when the load decreases, thereby stabilizing the operation of the remaining system.
Generally, in such a case, such a power safety system balances power supply and demand by selecting and cutting off the minimum necessary load from unimportant loads or loads that would have a negative impact on others if they remain. A recovery function is required, and conventionally, a shutoff selection method has been put into practical use in which loads are sequentially selected according to a preset order and shutoff is shut off until the supply-demand balance is restored.

However, the method of shedding loads uniformly according to a preset order of shedding does not cause many problems when dealing with stable loads with little load fluctuation, but when dealing with intermittent loads such as rolling motor loads in steel plants, When there is a load that fluctuates widely, if you execute control calculations based on the data when the load was in an idle state and selectively shut off the load,
There is a risk that the supply-demand balance will be disrupted again due to the subsequent rise in the load, which has been a drawback of the above-mentioned system. Also, some loads, such as electric motor loads on rolling lines,
For loads that are operated in a mutual relationship as a single group, there are cases where even if one of the loads stops, there is little point in continuing to operate the other loads in the group. . In this way, in the conventional cutoff load selection method, individual cutoff processing or group batch processing has been carried out according to the order of cutoff, so depending on how the cutoff order is set or the power balance situation, unnecessary loads may be left behind. Conditions could arise that would cause the load to be cut off. This invention was made to overcome the drawbacks of the conventional selective cutoff method as described above, and therefore, the purpose of this invention is to:
Loads that fluctuate intermittently (hereinafter sometimes simply referred to as intermittent loads) and loads in which several loads are operated as a group and interact with each other (hereinafter simply referred to as group loads) ), etc., to provide a cutoff load selection method in a power safety device that does not leave unnecessary loads, cut off excess loads, or cause the supply-demand balance to collapse again later. be.

The outline of the configuration of this invention is as follows.

That is, it can be said that the cutoff load selection method according to the present invention has the following three functions. (
1) For intermittent loads, their operating status is monitored and those in an idle state (almost equivalent to a no-load state) are selected as priority targets for shedding, regardless of the set load order for shedding. .

(2) For group loads that perform group operations (1
Even if any one of the groups is selected as a target to be shut off in the process of item ), all loads belonging to that group are preferentially selected as targets to be shut off, regardless of the operating state or the order of shutoff.

(3) After performing the processing in (1) and (2) above, take the data into account and execute the cutoff load selection calculation, and select from the remaining loads according to the preset order. and select the load to be cut off.

That is,. By prioritizing the terms (1), (2), and (3) above in numerical order, even if intermittent loads are included,
If it is in an idle state, it is prioritized to be cut off, so that the load is prevented from rising after the cutoff control.

Further, due to the operating characteristics of the group loads, if one of them is cut off, continuous operation of the whole group becomes impossible, and the remaining loads are forced to become idle after a certain time limit. In such a case, by prioritized shedding of loads for which there is little point in continuing operation through the processing in item 2 above, it is possible to survive even loads with a high set shutdown order (priority). The load to be cut off can be limited to the minimum necessary. In addition, if the number of interrupted loads is insufficient even after processing in (1), (2), and above, or if there is no processing in (1), (2), and above, the normal setting order in (3) will be applied. It goes without saying that the selection cutoff is executed in accordance with this, and at that time, the processing results of terms (1), (2), and terms are reflected in the calculation process of term (3). Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a power system, and FIG. 2 is a characteristic diagram showing an example of power flow in each part within the system.

Please refer to FIGS. 1 and 2. WR indicates the power received through the transformer Tr, and the received power changes reflecting changes in the load. WG indicates the power generated by the generator G, and the generator G continues constant output operation regardless of load fluctuations. WL, to WLn indicate the power consumption of individual loads (L, to Ln), and each has a characteristic behavior. WLl represents the power consumption of the stable load Ll that continues to operate at a fairly constant rate, WL2 represents the intermittent load L2 that fluctuates significantly, WL3 represents the intermediate load L3 that fluctuates gently, and WLO represents the power consumption of the load Ln that fluctuates rapidly. show. In the illustrated power system, the relationship of the following equation always holds true for the power flow in each part: N WR + WG = ΣWLi (however, the sign of the power flow is 1 = 1
3A is a schematic diagram of a rolling line shown as an example of a group load, and FIG.

See Figure 3. The workpiece S to be rolled is sequentially rolled by rolling rolls R1 to R4 as it progresses in the direction of the arrow. Rolls R1 to R4 are loads of motors M1 to M4, and W and W4 indicate power consumption of motors M1 to M4. F1 to F4 are load ends, respectively.
This rolling line is composed of four sets of rolls R1 to R4 as one group, and if even one of the load ends F1 to F4 is turned off, the rolling line will lose its function as a line. It is something. In other words, in such a case, continuous rolling is impossible, so not only the motors and rolls belonging to the load end that has been turned off, but also the motors and rolls belonging to other load ends will eventually stop or become idle. It is inevitable. In addition, with the cap in Figure 3,
I indicates an idle state (equal to a no-load state), and L indicates a loaded state. FIG. 4 is a diagram showing a comparison of the conventional method and the present invention for selecting a cutoff load when the power supply terminal falls off.

It is assumed that the power supply terminal power is composed of WP1 to WP3, the load terminal power is composed of WL1 to WL15, and the load terminal power suffix (item 15) corresponds to the set cutoff order. Also, (1) indicates the idle state load, and LG
indicates group load. During normal times, ΣWPi=ΣWL
i holds 1=11-1, and the supply and demand of electricity is balanced.

If a power supply terminal disconnection accident occurs and, for example, WPl is lost, a load equivalent to WPl will be transferred from WLLl to WLLl.
If you select from 5 and shut it off, the remaining power at the power supply end (
Only the load commensurate with WP2+WP3) remains, and the supply-demand balance is restored again. The load end power (1) shows the conventional method of selecting from the top according to the set order, and W
If Pl falls off, this indicates that WLl to WL7 will be selectively shut off, but the remaining loads include loads WL8, WL, . . When rises, WP2 + WP3 + WL8
+WL, +... +WLl5, and there is a risk that the supply and demand balance will collapse again.

On the other hand, the load end power (2) shows the cutoff load selection method based on the present invention, and when WPI is dropped,
First, the loads WLl, WPl, WL8, which are in the idle state,
Wlll is preferentially selected, and the group loads WLlO-WLl3 including the idle load WLll are selected preferentially, and finally,
WL2 is selected from the top according to the set order. in the end,
WLl, WL2, WL4FWL8 due to dropout of WPl
Since WLl, WLll} WLl2 and WLl3 are cut off, there is little risk that the remaining load will increase after the cutoff control, and the supply and demand balance is stable. Figure 5 is a diagram that simulates this situation. be.

1 indicates the sum of the load end powers (sum of power end powers) before the power supply terminal dropout accident, and 2 indicates the load limit value (power supply capacity of the remaining power supply end) after the power supply terminal dropout accident occurs.

When selective load shedding is executed (cutting off the load amount of the WT) at the time when the power supply end disconnection accident occurs, the sum of the load end powers 1 shifts to a curve 3 or 4. 3 shows the result of selective cutoff according to the present invention, and there is almost no possibility that the load limit value of 2 will be exceeded.

4 shows the results of the conventional method, and shows in a simulated manner that the load limit value may be exceeded as shown in the shaded area due to the rise of the idle load.

FIG. 6 is a block diagram of essential parts of an embodiment of the present invention.

In FIG. 6, the arithmetic unit 1 is a power safety device, and
This is a computing unit that receives power flow data and performs selection calculations to select the appropriate load to be cut off when the power grid's power coupling capacity is reduced due to a power supply terminal disconnection accident, etc. . 2 is an intermittent load monitoring means for monitoring the operating status of the intermittent load, and 3 is a group load monitoring unit for monitoring the operating status of the group load.

In the method according to the present invention, the computing unit 1 not only receives power flow data but also receives each monitoring data from the intermittent load monitoring means 2 and the group load monitoring means 3. When the power supply capacity is reduced due to an accident such as a power supply terminal falling off, intermittent loads and group loads in an idle state can be prioritized as targets for selective cutoff. As explained above, according to the present invention, an intermittent load in an idle state and a group including the intermittent load are selected as loads to be selectively cut off when the power supply capacity is reduced due to an accident or the like in the power system. Since loads are selectively and selectively cut off with priority, there is no risk that the power supply and demand balance will be disrupted again due to the rise of idle loads later, and there is no need to leave unnecessary loads or cut off excess loads. In other words, there is an advantage that the cutoff load selection can be rationalized.

Although this invention has been explained using the case of a power supply terminal disconnection accident as an example, it is particularly effective for a single generator system where there is a limit on back power, and when there is a need for load limitation due to a drop in overload frequency, etc. It can also be effectively applied in other cases.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a power system, and FIG. 2 is a characteristic diagram showing an example of power flow in each part within the system.

Claims (1)

[Claims] 1. In a power system in which power is supplied from the power source to the load by commonly connecting at least one power source end that is a terminal connected to the power source and at least one load end that is a terminal that is connected to a load, accidents such as power source end disconnection, etc. Therefore, when the power supply capacity decreases, a corresponding load is determined by a predetermined calculation and is selectively cut off.This is a cutoff load selection method in a power safety system, and the operating status monitoring monitors the operating status according to the nature of the load. and an arithmetic unit for determining the load to be cut off by calculation, and the operating condition monitoring means selects and cuts off the intermittent load in the idle state, mutually The operating loads that belong to one group of loads that operate in conjunction with each other and which include intermittent loads in that group, and the operating continuous loads are respectively identified, and the identification data is input to the arithmetic unit. The arithmetic unit determines the selection priority in the order in which the loads are listed above, giving priority to the order fixed in advance for each load, and selects the cutoff load based on predetermined data including the identification data. A cutoff load selection method in a power safety device, characterized in that the calculation is performed.