JPH04317511A - Overload controller for transmission line - Google Patents

Abstract

PURPOSE:To prevent overinfluence onto consumers by operating the conductor temperature based on the current of transmission line and the ambient temperature, deciding an overload state of the transmission line based on thus operated temperature and outputting a requisite load interruption command thereby performing a highly accurate and rational control for releasing overload. CONSTITUTION:An operation controller 16 receives detection values from a current detector 11 and an ambient temperature detector 12 for a transmission line and set values from a continuous allowable temperature setter 13, a short time allowable temperature setter 14 and an allowable current constant setter 15. The operation controller 16 operates the conductor temperature and when thus operated temperature exceeds an allowable temperature limit, a requisite load interruption is set and a signal is fed to a load interruption commander 17. Consequently, a highly accurate and rational overload control satisfying practical operating conditions is realized resulting in suppression of the influence of load interruption onto consumers.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for eliminating overload on power transmission lines of an electric power system.

0002

[Prior Art] First, a conventional power transmission line overload control device is described, for example, in "Power System Protection Control System" published by Denkishoin May 1975, P. The methods described in Nos. 171 to 184 will be explained. Figure 3 is a power system diagram that is the object of control. In the diagram, 31 is the generator of power plant A, 32 and 3
Reference numeral 3 indicates a power transmission line that connects power station A to substation B and substation C, respectively, and reference numeral 34 indicates a power transmission line that connects substation B and substation C. 35 and 36 are load groups of substation B and substation C, respectively.

[0003] Now, each power transmission line 32, 33 and 3
Assume that the power transmission line 33 is cut off for some reason while currents IA, IB, and IC are flowing through the power lines 4 and 4, respectively. Immediately after the above-mentioned interruption is performed, the current in the power transmission line 32 is IA + IB, and the current in the power transmission line 34 is IC + IB.
become. Here, if the current IA+IB of the power transmission line 32 exceeds a certain specified value and becomes overloaded, it is necessary to cut off part of the load group 35 to suppress the current of the power transmission line 32 below the specified value, for example. Similarly, when the current IC+IB of the power transmission line 34 exceeds a certain specified value and becomes overloaded, it is necessary to cut off part of the load group 36 to suppress the current of the power transmission line 34 below the specified value.

FIG. 4 is a block diagram showing a conventional device that performs the above-mentioned overload control. The device in the figure is installed for each power transmission line, and in the figure, 41, 43, and 45 input the current of the transmission line, and the overload rate is x% and y%, respectively.
and an overcurrent relay that detects z% or more, 4
2, 44 and 46 are overcurrent relays 41 and 43, respectively.
and a timer operated by the output signal from 45;
47 is a setting device for setting which load group is to be cut off to eliminate overload based on the output signals from each timer 42, 44, and 46; 48 is a setting device for setting each load group to be cut off in order to eliminate overload based on the output signal from each timer 42, 44, 46; This is a load shedding command device that sends a shedding command to the equipment.

FIG. 5 is a time chart for explaining the situation in which the above-mentioned device operates and the overload on the power transmission line is eliminated. This will be explained below in conjunction with FIG. 4. First, time t
When the current in the power transmission line increases rapidly at 0, and the overload rate exceeds x%, the overcurrent relay 41 detects this and the timer 42 starts counting. When this state continues for T1 seconds, the timer 42 times up and sends its output signal to the setting device 47. Thereby, the setting device 47 sets the load group to be cut off,
The setting output is sent to the load shedding command device 48, and the load shedding command device 48 sends a break command signal to the specified circuit breaker to partially open the load group. Although the above operations reduce the overload rate of the transmission line, the overload rate still remains
%, the timer 44 will time out when T2 seconds have elapsed, and based on this, the setting device 47 will set a new load shedding. Thereafter, similar operations are performed to adjust the load until the overload rate becomes z% or less, and the overloaded state of the power transmission line is resolved.

[0006]

[Problem to be Solved by the Invention] Since the conventional power transmission line overload control device is configured as described above, it sequentially performs load shedding in steps of a fixed time period set in advance, so that the overload control device for transmission lines is configured as described above. There is a problem in that the electricity tends to be cut off rapidly, and the impact on electricity consumers becomes correspondingly large. This invention was made in order to solve the above-mentioned problems, and by taking into consideration individual conditions, rational and highly accurate overload cancellation control is performed to prevent excessive impact on electricity consumers. The purpose is to obtain a power transmission line overload control device that can

[0007]

[Means for Solving the Problems] A power transmission line overload control device according to the present invention includes a current detector that detects the current flowing in the power transmission line, a temperature detector that detects the ambient temperature of the power transmission line, and a current detector that detects the current flowing in the power transmission line. The system is equipped with an arithmetic and control device that calculates the conductor temperature of the power transmission line from the ambient temperature and outputs a shutdown command when the temperature exceeds a predetermined set value.

[0008]

[Operation] In the present invention, the conductor temperature is calculated from the current in the power transmission line and the ambient temperature, the overload condition of the power transmission line is determined from this temperature, and necessary load shedding is commanded.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a power transmission line overload control device according to an embodiment of the present invention. However, in this example, instead of calculating the conductor temperature directly from the current of the power transmission line and the ambient temperature, first, the continuous allowable current of the power line is determined from the ambient temperature, and this continuous allowable current and the current current of the power line are calculated. Calculate the conductor temperature from . Then, a method is adopted in which the conductor temperature is compared with an allowable temperature limit determined from the continuous allowable temperature and the short-time allowable temperature, and a cutoff command is output. The contents of FIG. 1 will be sequentially explained below.

In FIG. 1, 11 is a current detector that detects the current flowing through the power transmission line to be controlled; 12 is the ambient temperature of the power transmission line (detected at multiple appropriate locations when the transmission line is long, etc.); Temperature detectors 13 and 14 are respectively a continuous permissible temperature setter and a short time permissible temperature setter, which detect the average value or maximum value, etc.). A value is selected. For example, for heat-resistant aluminum alloy wire, the continuous allowable temperature is 1
The temperature is set at 50℃, and the short-term allowable temperature is set at about 180℃. Reference numeral 15 denotes an allowable current constant setter for setting a constant when calculating a continuous allowable current using a formula to be described later. 16
is the detected value from 11 and 12 and 13, 14 and 15
This is an arithmetic control device that calculates the conductor temperature by inputting the set value from the conductor, and when the conductor temperature exceeds a separately calculated allowable temperature limit, sets the necessary load shedding and sends the signal to the load shedding command device 17. .

Next, in particular, the operation of the arithmetic and control unit 16 is shown in FIG.
This will be explained according to the flowchart. Note that the process of the flow shown in FIG. 2 is constantly repeatedly executed at a fixed period (for example, 10 seconds). First, in step 21, the continuous allowable current In is calculated using the following equation. In=A・(Tn−Ta)+B
(1) However, Tn is a continuous allowable temperature and is input from the continuous allowable temperature setting device 13. Moreover, the value detected by the temperature detector 12 at the ambient temperature is adopted as Ta. Furthermore, A,
B is a constant and is input by the allowable current constant setter 15. Note that equation (1) is an approximation equation that is applied within a certain range, and although it is complicated, the accuracy can be improved by using a more detailed calculation equation.

Next, in step 22, the allowable temperature limit M is calculated using the following equation. M=(Ts-Ta)/(Tn-Ta) (2
) However, Ts is a short-time permissible temperature and is input from the short-time permissible temperature setting device 14. Next, in step 23, the conductor temperature increase θ(t) is calculated. The following formula is the calculation formula, and is expressed as a ratio to the continuous allowable temperature rise θn.

[Equation 1] Here, θ(t): Conductor temperature rise at the current moment (current calculation step) θ(t-1): Conductor temperature rise at the calculation step one cycle before θn: Continuous allowable conductor temperature rise (Tn -Ta)
Ia: The current power transmission line current is input from the current detector 11. △t: Time width for one calculation cycle τ: Thermal time constant of the conductor

Next, the process proceeds to step 24, where a comparison calculation is made between the conductor temperature increase θ(t)/θn and the allowable temperature limit M. Here, if the former is less than the latter, the flow is NO, and it is determined that there is no overload, and the calculation in that cycle is ended without outputting a command for load shedding. If the flow is YES in step 24, the process proceeds to step 25, where the necessary load shedding capacity is calculated based on the difference between the current transmission line current Ia and the continuous allowable current In, and a command signal is output to the load shedding command unit 17. (Step 26).

[0014] In the above embodiment, the overload is eliminated by load cutoff control, but it may be done by generator cutoff control, or both may be used in combination. In addition, the method of calculating the conductor temperature is not limited to the one explained in the above embodiment, and in addition to the control system from the temperature aspect described above, there is also a control system that operates by determining overload from the current value itself. A system may also be provided.

[0015]

[Effects of the Invention] As described above, since this invention is equipped with a predetermined current detector, temperature detector, and arithmetic control device, it can perform rational and highly accurate overload control in accordance with actual and specific usage conditions. This makes it possible to reduce the impact on electricity consumers due to load shedding, etc.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a power transmission line overload control device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating the operation of the power transmission line overload control device in FIG. 1;

FIG. 3 is a diagram showing a power system to be controlled.

FIG. 4 is a configuration diagram showing a conventional power transmission line overload control device.

FIG. 5 is a time chart showing operation control characteristics by the power transmission line overload control device of FIG. 4;

[Explanation of symbols]

11 Current detector 12 Temperature detector 16 Arithmetic control unit 17 Load shedding command device

Claims (1)

[Claims] [Claim 1] A power transmission line overload control device that disconnects a generator or a load from a system according to a load state of a power transmission line to eliminate an overload on the power transmission line, wherein a current flowing through the power transmission line is detected. A current detector, a temperature detector that detects the ambient temperature of the power transmission line, and calculates the conductor temperature of the power transmission line from the current and the ambient temperature, and issues the shutdown command when this temperature exceeds a predetermined set value. A power transmission line overload control device comprising an arithmetic and control device that outputs an output.