JPS5944857B2 - Demand power monitoring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power demand monitoring device that performs various calculations and displays in order to monitor power demand at a power consumer.

Conventional power demand monitoring devices, for example, count the transmitted pulses of a power meter with a transmitting device, calculate and display a predicted power demand when the demand time limit has elapsed based on this counted value, and display this value. There was a device that generated an alarm signal based on the

The operating principle of such a device will be explained with reference to FIG. In the diagram, the horizontal axis is the elapsed time of the demand time limit, and T is the demand time limit.

Also, the vertical axis is the power demand. 1 is a curve showing the increase in power demand.If the current power demand at the time when the demand has elapsed is p, and the increment in power demand from this point back by a certain short time interval △ is △p, then the demand Demand power in time period T, that is, predicted power demand R is given by the following formula (1) Δp R2 P+−×(T−) (1) Δ.

Note that the demand time limit T is usually 30 minutes, and Δ is 1 minute. The predicted power demand according to the above equation (1) is calculated at Δ time intervals. However, in the past, the time △ was limited to a relatively small value (for example, 1 minute), so for example, in a customer with a load such as a steel rolling facility, the predicted power demand R fluctuates greatly due to severe load fluctuations. It was hot. Therefore, in order to eliminate such drawbacks, a device has been proposed in which the time interval Δ for measuring the increment Δp in the power demand is increased, thereby reducing the influence of load fluctuations. The operating principle of this device will be explained with reference to FIG. In Figure 2, the elapsed time tl of the demand time limit is 2
, take a time interval △T, and let the increment of power demand in this time be △P1, △P2, △P3, and △T
is larger than △ in FIG. 1, for example, △ is taken as an integer multiple of △.

In other words, if n is any natural number, then the following formula ΔT=n×
Δt (n is 2 or more) ...{2) The following relationship should be satisfied.

From this relationship, the predicted power demand R can be expressed by the following equation (3).

Here, as can be seen from Fig. 2, if ΔT is larger than △t, ΔPl, ΔP2, △P
The values of 3 are averaged and can reduce the effects of load fluctuations. As described above, although the device based on the pulse principle shown in FIG. 2 reduces fluctuations in predicted power demand due to load fluctuations, it has the following drawbacks. In other words, the problem is the inability to follow load fluctuations or the insensitivity, which is the opposite of the above-mentioned characteristics. This drawback will be explained with reference to FIG.

In FIG. 3, the predicted power demands at the elapsed times Tl, t2, and t3 of the demand time limit are Rl, R2, and R3, respectively, and the target power demand to be managed is Q. Here, if the power demand increases rapidly from the time point t1, the predicted power demand R1, R2 at T1, t2 will exceed the target power demand Q. In this case, some conventional devices have the function of generating an alarm or shedding the load.
For example, assume that this alarm causes load shedding at time T2. Then, the increase in power demand becomes slower as shown at T3 in FIG. However, since the predicted power demand R3 at T3 still exceeds the target power demand Q, load shedding is further performed, resulting in the drawback that the load is cut too much. When load shedding is performed, in order to see the effect of load shedding, it is appropriate to measure the increment ΔP in power demand in calculating the predicted power demand R from the time when load shedding is performed. In other words, at the time T, it is preferable to calculate the predicted power demand R by taking Δt instead of ΔT and using Δ4 as the increment of the power demand. In this way, the predicted power demand of ζ2 becomes RΔ, which falls below the target power demand Q, and the effect of load shedding is clearly seen. The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology, and in calculating predicted power demand, the time interval for measuring increments in power demand is usually lengthened, so that the predicted power demand is exceeded. In this case, by shortening the time interval for measuring the increment of the above-mentioned power demand,
The present invention aims to provide a power demand monitoring device that can clearly monitor the state of power demand.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 4, reference numeral 1 denotes a power meter that measures the amount of power in the circuit via PT and CT and emits a pulse proportional to the amount of power used. 2 is a demand power counter that counts these pulses; 3
, 4 are counters that measure the increment in power demand at fixed time intervals, and when n=2 in equation (2),
This is a configuration example in the case of the relationship ΔT=2·Δt.

In other words, if we explain using FIG. 3, the incremental counter 3 is Tl.
, t, ...... Increase in power demand ΔPl, ΔP, ・
...Count △P2l-1, and the increment counter 4 is T
2, t4...Increments in power demand ΔP2, ΔP4
. . . A counter that counts ΔP2l. Reference numeral 5 denotes a clock unit that measures the demand time limit T and resets the count value of the demand power counter 2 to zero at every demand time limit T interval.

Further, the demand power increment counters 3 and 4 are returned to zero alternately with a time difference Δt at every time interval ΔT or Δt. Furthermore, at the same time, the remaining time of the demand time limit (T-t)
Also measured. The time intervals ΔT and Δt are switched by the switching circuit 12. Reference numeral 6 denotes a gate circuit, which alternately switches the counted values of the power demand increment counters 3 and 4 every Δt according to a signal from the clock section 5 and inputs them to the arithmetic circuit 7.

7 is based on the measured values of the remaining time Tt of the demand time limit of the demand power counter 2, the gate circuit 6, and the clock section 5 (3)
This is a circuit that calculates predicted power demand at each time interval Δt using a formula, and the calculation results are displayed on a display circuit 8.

Reference numeral 9 denotes a target power demand setting device, which sets a target value for the predicted power demand.

A comparison circuit 10 compares the predicted power demand with the target power demand, and generates an alarm signal when the former exceeds the latter.

Reference numeral 11 denotes an alarm circuit, which is activated by the above-mentioned alarm signal and uses a lamp, a buzzer, or a contact signal to inform the outside that the power demand may exceed the target power demand, thereby calling the administrator's attention.

Now, when an alarm signal is generated from the comparator circuit 10, this signal causes the switching circuit 12 to switch the interval of the zero return signal of the demand power increment counter from ΔT to Δt, and from that point on, starts counting ΔP anew. At the same time, the configuration of the arithmetic circuit is switched so that the predicted power demand is calculated by the arithmetic expression (1) while the alarm signal is being output. Although the embodiment of the present invention has the above-described configuration, the power demand increment counters 3 and 4 are not limited to two circuits at all, and can be provided with three or four circuits. Further, by using a changeover switch, for example, even if five circuits are provided, only three of them can be used. Also, considering that the circuit becomes more complex when the number of circuits is increased, it may be advantageous to use a microcomputer to configure arithmetic circuits, gate circuits, power demand counters, comparison circuits, etc. . Further, in the description of the present invention, the calculation of predicted power demand has been explained, but it is also possible to apply the principle of the present invention to calculation of adjusted power, which is the amount of adjustment of load. As described above, according to the present invention, the time interval for measuring the increment in power demand can be made shorter when the predicted power demand exceeds the target value than when it does not exceed the target value. The effect can be immediately determined, and the power demand can be appropriately monitored without problems such as excessive load cutting, and the effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing the operating principle of one embodiment of the conventional device, FIG. 2 is a time chart showing the operating principle of another embodiment of the conventional device, and FIG. 3 is an embodiment of the device according to the present invention. FIG. 4 is a time chart illustrating the principle of operation of an example; and FIG. 4 is a block diagram of an embodiment of the apparatus according to the invention. In the figure, 1 is a power meter with a transmitter, 2 is a demand power counter, 3 and 4 are demand power increment counters, 5 is a clock unit,
6 is a gate circuit, 7 is an arithmetic circuit, 8 is a display, 9 is a target power demand setting device, 10 is a comparison circuit, 11 is an alarm circuit, 1
2 is a switching circuit.

Claims (1)

[Claims] 1. A counting means for counting the transmitted pulses of a power consumption meter with a transmitting device, and determining the amount of increase in the counted value within a certain set time, and calculating the said counted value as the product of the amount of increase within the same time and the remaining time of the demand time limit. In a power demand monitoring device comprising means for calculating predicted power demand by adding , and means for comparing the predicted power demand with a target power demand, the condition is that the predicted power demand exceeds the target power demand. and means for shortening the set time to a predetermined value.