JPS6022414A - Method of protecting small capacity power load system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for protecting a small-capacity power load system in a power receiving system in which a small-capacity power load system and a large-capacity power transmission system are connected in parallel.

The small-capacity power load system according to the present invention is a power generation system using a small generator such as a private power generation facility in a factory, and the power generation amount thereof is generally several thousand kW to several hundred thousand kW.

On the other hand, a large-capacity power transmission system is, for example, a power transmission system from an electric power company or the like, and the amount of power generated by these systems is generally several tens to hundreds of times that of a small-capacity power load system.

Generally, in factories that have in-house power generation equipment, about half of the electricity used (power required for the cup) is often covered by the in-house generated power due to the convenience of the process.

However, from Kotobuki, in order to ensure the minimum amount of power necessary for the factory group even in emergencies such as problems with private power generation equipment, or for economic reasons, a dedicated power transmission line was installed within the private power generation (small capacity power load) system. The system is installed and connected to a large-capacity power transmission system from an electric power company, etc., and is operated in a 4v1 array.

In a power receiving system that uses both a small-capacity power load system and a large-capacity power transmission system, there are generally system protection circuit breakers connected in series to protect each power system on the large-capacity power transmission system (transmission) side. After passing through the power transmission line, it is installed on the small capacity power load system (power receiving) side.

Traditionally, in large-capacity power transmission systems, large generators suddenly stop due to various accidents, or power transmission-side circuit breakers are cut off due to man-made or disasters, which occur approximately several times every seven years. Sometimes. In such a case, depending on the status of the system constants at the time of the accident, power will flow from the Kokichi i'flL power load system to the Jingyo power load system, and therefore the (private) generator of the small capacity power load system will In some cases, overload occurred, and due to a drop in frequency, differential vibrations occurred in the final stage rotor blades (rotating body) of the generator's turbine.

Therefore, as a method to prevent such accidents, power directional relays are generally installed in power transmission lines to detect reverse power in the event of an accident such as the one described above, and open the receiving side circuit breaker based on the detection signal. (cut off), and further operate the power demand adjustment device of the power demand group based on the cutoff signal to maintain the balance of power supply and demand. However, according to the above method, when the load power decreases due to a sudden accident on the factory load side, the amount of power is reduced during the power decrease on the transmission system side rather than during the power decrease on the small capacity power load system. As the power becomes larger, power may be sent back from the small-capacity power load system to the large-capacity power transmission system, and in this case, the power receiving circuit breaker shuts off due to the frequency and voltage within the small-capacity power load system. This is not preferable because it causes disturbances such as

As another method to prevent the above accident, a wired or wireless signal circuit is installed between the power transmission circuit breaker and the power reception circuit breaker. It is conceivable to shut off the circuit breaker and then maintain the A balance between the supply and demand of power in the power demand group using a method similar to the above. However, in the above method, the distance from the power transmission circuit breaker to the power reception circuit breaker is generally several kilometers through the city.
Due to the distance, if a wired system is used, there are many accidents where the connection line is cut due to typhoons, traffic accidents, etc.If a wireless system is used, malfunctions may occur due to radio wave induction interference, etc. It is difficult to obtain it reliably and economically.

As a result of studying methods to solve the above-mentioned problems, the inventors of the present invention discovered a method of shutting off the power receiving circuit breaker only when the frequency of the large-capacity power transmission system drops abnormally and the receiving current drops abnormally. , we have now provided the present invention.

That is, the present invention provides a power receiving system in which a large-capacity power transmission system is connected to a small-capacity power load system in parallel via a power-receiving power transmission line via a circuit breaker for each system. Frequency relays that emit a signal due to a drop in frequency and insufficient + that emit a signal due to a drop in receiving current
kL#r, a relay is installed, and when the signals of the frequency relay and the undercurrent relay occur simultaneously and overlappingly, the signal interrupts the small-capacity power load system side breaker, and the disconnection signal also interrupts the power demand adjustment device. This is a method for maintaining a small-capacity power load system, which is characterized by operating a small-capacity power load system.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 7 is an explanatory diagram showing a representative/aspect of the present invention.

That is, this is a power receiving system in which a large-capacity power transmission system 4 is connected to a part of a small-capacity power load system 2 through a power reception-only power transmission line 8 as the power used in the power demand (factory) tI+1 in FIG. Such a power receiving system generally includes a power transmitting-side breaker 5 and a power-receiving-side breaker 6 (and?) as grid-protecting circuit breakers for protecting each power system.

As shown in FIG. 1, as long as the small-capacity power load system 2 and the large-capacity power transmission system 4 are operated in parallel, the frequency of each system is the same at any point. Therefore, for example, if some of the generators (G) in the large-capacity power transmission system 4 come to an emergency stop due to an accident or the like, the width of the decrease in frequency in the large-capacity power transmission system 4 and the small-capacity power load system 2 will be the same. It is determined by the power frequency characteristic constant (system constant) of the large-capacity power transmission system 4, and for several seconds after an accident, the power and frequency flowing from the large-capacity power transmission system 4 to the small-capacity power load system 2 decrease, and in some cases, Electric power flows from the capacity power load system 2 to the large capacity power transmission system 4. In the present invention, changes in current and frequency at that time are detected by a frequency relay 9 and an undercurrent relay 10 installed in the transmission line 8 from the large-capacity power transmission system 4, and these signal contacts are used in series. Only when both signals fall below preset values, the power receiving circuit breaker 6 is automatically shut off by this signal. Furthermore, by operating the demand power adjustment device #ll of factory group 1 based on this signal, the demand power corresponding to the decrease in transmitted power is reduced, thereby preventing an abnormal decrease in the frequency of power demand factory group 1, and at the same time, the in-house power generator protect.

Furthermore, according to the method of the present invention, even if the power transmission circuit breaker 5 is cut off for some reason, the receiving current and frequency will drop, so the above-mentioned mechanism will be used to protect the private power generation small capacity system 2. You can.

In the method of the present invention, it is necessary to interrupt the power receiving side circuit breaker 6 by the signals only when the signals of the frequency relay 9 and the undercurrent relay IO installed in the power receiving power transmission line 3 overlap and occur at the same time. In other words, if the signal is only 0 (undercurrent relay), the receiving current may be adjusted to zero (KH) due to reasons such as reducing the power load in the factory, so at this time the power receiving circuit breaker 6
If the power is turned off, it will actually interfere with operation.Furthermore, the signal from the frequency relay 9 alone will not be used when receiving current is required, such as when transmitting power to the factory group 1 when the generator of the small-capacity power system 2 is stopped. Since the power receiving circuit breaker 6 is also turned off, no cutoff signal is issued.

In addition, if relay 9 or 10 breaks down for some reason,
This is effective in preventing power receiving malfunction and cut-off when an erroneous signal is output. At this time, the type and capacity of the frequency relay 9 and the undercurrent relay 10 used in the present invention may be appropriately selected from standard products that match the received power, and the installation location on the power transmission line 8 is not particularly limited. Generally, power receiving circuit breaker 6
Installed on the secondary side (load side) of the Further, when connecting, an instrument transformer 12 and an instrument current transformer 18 are used. The method of breaking the circuit breaker 6 on the power receiving side using the above-mentioned duplicate signals is not particularly limited, and any known method may be used.

The power demand adjustment device 11 used in the present invention is not particularly limited and any known device may be used, but in general, a selective load shedding device is preferably used. The selective load shedding device sorts the power-demanding factory group into "important loads" and "non-important loads" in advance, and detects this signal in the case of an emergency power outage in the large-capacity power system 4, for example. This is a device that is configured to shut off "non-critical loads" almost simultaneously in conjunction with the "Cd accident shutoff" installed in a group of factories.This device reduces the power demand of the factory and reduces the remaining "important loads." , the supply can be continued within the capacity of the private power generator 14, and damage to the factory operation side will be greatly reduced.

As for the connection method between the power receiving circuit breaker 6 and the power demand adjustment device @1.1, any known method can be used without any particular restriction.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the system of the present invention. In the figure, the lti power demand group, the two-digit small capacity power system,
8Fi power receiving power transmission line, 411- to large capacity power system, 5
is a system protection breaker (transmission side or disconnector), 6.7 is a power receiving side breaker, 8ke Anzu, Yosagi system, generator inside, 9Fi
Frequency relay, 10it undercurrent relay, 11 demand power adjustment device, 121j instrument transformer, 18 instrument current transformer, 14 private power generation 3i 1, Patent applicant Tokuyama Soda Co., Ltd. Figure 1

Claims (1)

[Claims] +11 Adding a large-capacity power transmission system to a small-capacity power load system,
In a power receiving system that is connected in parallel via a power receiving transmission line via a protective circuit breaker for each system, a frequency relay that emits a signal due to a drop in frequency in the power receiving dedicated power transmission line and an undercurrent relay that emits a signal due to a decrease in receiving current. A small-capacity power supply system characterized in that a circuit breaker on the small-capacity power load system side is cut off when each of the above-mentioned signals occurs simultaneously and redundantly, and the demand power adjustment equipment is further operated based on the cut-off signal. How to protect power load system