JPH0386018A - Load selective circuit breaker - Google Patents

Abstract

PURPOSE:To improve the system reliability by inputting output frequency element and load current element of a generator into an arithmetic unit and tripping a suitable switch, upon droppage of generator output due to overload and the like, with an alarm being provided prior to the trip operation. CONSTITUTION:An arithmetic unit 13 is provided with an output frequency element of a generator 1 detected through a metering transformer 2 arranged at the output side of the generator, respective load currents detected through metering current transformers 3-7 arranged on the feeders for respective loads 8-12, and a unit time predetermined through a unit time setting circuit. When the frequency drop within the unit time exceeds over a predetermined level, the arithmetic unit 13 judges that subsequent frequency drop with same falling rate may cause interruption of load and thereby provides an alarm through an alarm unit 20 prior to trip operation of a switch. Since the load to be tripped can be minimized, high availability can be maintained in a factory and the like and the system reliability is improved.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a load selective cutoff device.

(Conventional technology) Conventionally, in a load selection breaker for a power distribution system connected to a generator in a factory, etc., a frequency relay detects a drop in the generator output frequency and trips a predetermined switch. Therefore, the importance level must be determined for all loads, and there is a problem in that the switches are tripped in descending order of importance level, regardless of the state of the load (large or small).

(Problems to be Solved by the Invention) As described above, the prior art has a drawback in that the order of the switches to be tripped is determined in advance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a load selection breaker capable of selecting the most appropriate switch to be tripped and issuing an alarm before the switch is tripped.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides an instrument transformer installed to detect the output frequency of a generator, an instrument current transformer installed to detect a load current, and the above-described instrument transformer installed to detect the output frequency of a generator. A load selection breaker device consisting of a calculation device that calculates various quantities detected by the system, an alarm device that issues an alarm when the calculation device determines that an abnormality has occurred, and a tripping signal output device that trips the switchgear. It is.

(Function) The output frequency element and load current element of the generator are input into the calculation device, and when the generator output decreases due to overload, etc., the appropriate switch is tripped and an alarm is issued before tripping. emanate.

(Embodiment) Fig. 1 is a block diagram showing an embodiment of the present invention, and shows an instrument transformer 2 installed to detect the output frequency element of a generator 1, and a transformer 2 installed to detect the load current. The installed instrument current transformers 3 to 7 and a calculation device 13 that calculates the various quantities detected as described above.

An alarm device I20 that issues an alarm when this calculation device determines that there is an abnormality, and a trip signal 1 that trips the switches 14 to l&
The trip signal output device 21 outputs a signal 9.

Generator output frequency element F detected by instrument transformer 2 installed on the output side of generator 1 and each load current detected by instrument current transformers 3 to 7 installed at the feeder of each load 8 to 12 ■. ~ engineering, yo and pre-unit time setting circuit 13
The unit time T determined in A is input to the arithmetic unit 113.

First, the output frequency determination circuit 13B detects F when the output frequency F starts to decrease and sets it as Fl, and F after unit time T.
&F□, the frequency drop ΔF in unit time ゛T
When =F1-F2 exceeds a predetermined value, the calculation device 13 determines that if the frequency decreases at the same rate of decrease in the future, the load will be cut off, and the alarm device 20
An alarm is issued to the outside via the

Furthermore, if the external cause of the frequency drop is not removed even after issuing the above-mentioned alarm, a load selective cutoff operation is performed.

For example, if the load importance is set as Load 8>Load 9=Load 10>Load 11=Load 12, the load current is in the relationship I, > 11°, I,1)I, and the output frequency is cut off. When the first stage frequency Fl at which the load current is to be performed is reached, the arithmetic unit 13 compares and calculates the sum of all load currents and the load 12 according to the preset function by If it is determined that it is possible to recover the output frequency by tripping the switch,
The switch 18 is tripped, while the load 11 with a large load current
If it is determined that it is necessary to trip the load 11, then the load 11 is tripped, and if it is determined that both the load 11 and the load 12 need to be tripped, the load 11. Both loads 12 are removed.

If the output frequency does not recover with the above first stage operation and drops to the second stage frequency F4, first trip the load 11 or load 12 if it remains, and then remove the load 9. Comparisons, calculations, and operations similar to those in the second stage are performed for the load IO.

Similar control is sequentially performed for loads with high importance.

〔Effect of the invention〕

According to the present invention, it is possible to minimize the load to be tripped in order to restore the generator output frequency.
Maintaining high operating rates in factories, etc., increasing system reliability, and setting the importance of loads.

Since the frequency F can be easily set, and devices installed in normal power distribution equipment such as instrument transformers and instrument current transformers can be used, it is possible to supply an inexpensive load selection breaker.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a load selection and disconnection device showing one embodiment of the present invention. 210. Instrument transformers, 3-7...Current transformers. 13... Arithmetic device, 20... Alarm device, 21...
Tripping signal output device. death

Claims (1)

[Claims] An instrument transformer that detects the output frequency of the generator, a plurality of current transformers that detects load current, and an arithmetic device that computes various quantities detected by these current transformers and the instrument transformer; A load selection and disconnection device comprising an alarm device that issues an alarm when this calculation device determines that an abnormality has occurred, and a tripping signal output device that trips the switch.