JPH0716288B2 - Static overcurrent relay - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static overcurrent relay, and more particularly to improvement of a driving power supply for supplying current to operating element circuits in the relay.

B. Conventional technology An overcurrent relay for a three-phase power supply takes the secondary current of a current transformer provided in two of the three phases into a signal transformer built in the relay and uses this signal for this signal. An overcurrent is detected by the detection current of the transformer to perform an instantaneous operation or a timed operation.

Especially in static overcurrent relays, the operating element circuit is IC
Since it is composed of an electronic circuit such as, a driving power source for operating the electronic circuit is required, and it is built in the relay. FIG. 2 is a circuit configuration diagram of such a conventional static overcurrent relay. R, S, T are power circuits of R phase, S phase, T phase, CT1 is a current transformer provided in T phase, CT2. Indicates a current transformer provided in the R phase.

This type of static overcurrent relay has the circuit configuration shown by the chain line in the figure. That is, the current flowing in the distribution line is detected by the current transformers CT1 and CT2 provided in the distribution line D to be monitored, and this is input to the overcurrent relay OCR to reach the overcurrent value set by the overcurrent relay OCR. Then, the circuit breaker CB provided on the power distribution line D is cut off according to the operation time characteristic determined at this time to cut off the power supply to the load L.
This overcurrent relay OCR has input terminals K1, L1 and K2, L2 for inputting the signals from the above-mentioned current transformers CT1, CT2, and these input terminals K1, L1 and K2, L2 are respectively incorporated in the relay. The power source transformers 20 and 22 and the signal transformers 21 and 23 are connected. The outputs of the power supply transformers 20 and 22 are rectified by each other.
It is rectified by 11 and 12 and input to the power supply circuit 13, which is used as a power supply for driving the operating element circuit OE in the relay when an overcurrent occurs, and the outputs of the signal transformers 21, 23 are also rectified by the rectifier circuits 14, 15. Input to the maximum value detection circuit 16 and the detection circuit 16 detects a signal proportional to the maximum value of the input signal to detect a timed current setting circuit.
Enter in 17. Here, the operation reference according to the load current is settled. Then, when the load current reaches the settling value, a signal is sent to the super-reverse time characteristic circuit 18, and the level detection circuit, the square characteristic circuit, and the time circuit, which are internally provided in the super-reverse time characteristic circuit 18, operate and the current flows. Depending on the magnitude of the value, the breaking relay X operates after a predetermined time period to close the contact x and break the breaker CB.

C. Problem to be Solved by the Invention As described above, the static overcurrent relay uses the semiconductor element circuit for the operating element circuit OE, so unlike the induction relay, each circuit in the operating element circuit functions. A driving power supply is required to drive the power. This drive power source is generally obtained by incorporating a power source transformer in a relay and rectifying its output. This transformer has a JIS standard of 200% of the rated current as an overload withstand test (100A when the rated current is 5A). 2
50ms, instantaneous element tap (60A as 20 times the timed element 3A)
There is a test that flows 200% (120A) 50ms, and this must be cleared.

On the other hand, the operating element circuit has become possible to be formed in a very small circuit configuration due to the progress of semiconductor technology, particularly semiconductor integrated circuits. However, as mentioned above, the static relay requires a transformer for the power supply, and this transformer has a limitation in miniaturization in order to satisfy the linearity of the current characteristics and the standards as described above, and Two pieces are required, which is a bottleneck for miniaturization of this type of relay.

Therefore, one transformer for the power supply is used, two input windings and one output winding are provided, and the transformer CT1 is connected to one input winding.
It has been attempted to connect the current transformer CT2 to the other input winding and rectify the output of the output winding to use it as the drive power source. The T phase provided with the CT1 device and the R phase provided with CT2 are the second
When a short-circuit accident as shown in E of the figure occurs, the short-circuit current becomes the same as that in single phase, and currents in the opposite directions to the current transformers CT1 and CT2 flow, and the two transformers for the power supply are connected. There is a problem that currents of opposite polarities also flow in the input windings and the magnetic fluxes cancel each other out, or there is a mistake in the connection between the input winding and the terminals in the relay, or incorrect wiring of the terminals during installation work at the site. In such a case, there is a danger that the magnetic fluxes created by the two input windings cancel each other out and the power supply voltage cannot be obtained, and it has been regarded as difficult to realize.

The present invention has been made in view of the above points, and provides a power supply transformer that uses one drive power supply transformer and that does not lose the function of the drive power supply even in the event of the above-mentioned accident. It is intended to provide a relay of this kind that it has.

D. Means for Solving the Problem In a static overcurrent relay provided with an operating element circuit, a signal transformer for current detection, and a power source transformer of the operating element circuit, The transformer is a transformer with an output winding and two input windings, and the number of turns of the two input windings is different.

E. Action When an overcurrent flows through the load, the overcurrent is detected by the signal transformer and given to the operating element circuit OE, as in the conventional case.
At the same time, a current proportional to the load current also flows in the two input windings of the power transformer, and a voltage is induced in the output winding. This output voltage is rectified and applied as a driving power supply for each circuit in the operating element circuit. Therefore, each circuit in the operating element circuit becomes operable, and when the load current reaches the set value, the breaking relay operates after a predetermined time to break the breaker.

Next, for example, when an accident occurs in which the R and T phases are short-circuited, the short-circuit current flows from the R phase to T
Current transformer CT1 that flows in the phase and is provided in the R and T phases
And the currents in opposite directions flow in the primary side of CT2.
If the terminals are connected incorrectly, currents of opposite polarities, that is, currents of mutually canceling magnetic flux, also flow in the two input windings of the power transformer connected to the secondary winding. However, since there is a difference in the number of turns of the two input windings, a magnetic flux is generated due to the difference in ampere-turns (number of turns x current) of both windings, and a voltage as a drive power source is generated in the output winding, which causes the operation. The power supply voltage required for the operation of the element circuits is secured.

F. Example Hereinafter, the present invention will be described based on an example shown in FIG.

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. Portions having the same functions and portions having the same names as those in FIG. 2 are designated by the same symbols as those in FIG. 2 and their explanations are omitted.

The present invention, however, is characterized in that the number of turns is different by using one power transformer and two input windings. That is, in FIG. 1, reference numeral 1 is the power transformer, which has two input windings IP1 and IP2 and an output winding IS. The input winding IP1 is connected to the T-phase current transformer CT1 via the input terminals L1 and K1, and the input winding IP2 is connected to the input terminals K2 and L.
It is connected via 2 to the R-phase current transformer CT2. Also output winding
The output side of IS is rectified by the rectifier 2 and used as a power source for driving the operating element circuit OE via the power source circuit 3.

The number of turns of each winding of the power transformer 1 is an operation element circuit when a current equal to or larger than a set current value flows in the distribution line D.
The OE is designed to supply a current capable of operating, but in the present embodiment, one input winding IP1 is connected to the polarity shown in the figure as 10 turns, and the other input winding IP2 is connected to 7 turns. The difference is 3 turns, and the output winding IS is formed with 280 turns with an intermediate tap. And as a result of the measurement, when a current of 1.68A flows in the input winding of 3 turns,
A voltage was obtained on the output winding side that could reliably operate the operating element circuit.

Generally, in the current transformer attached to the distribution line D, the rated primary current is standardized, and the secondary current is often 5 A at the rated current value. The overcurrent relay is required to operate at 60% of the minimum rated current, but when 60% of the rated current flows, 5A of 60
%, That is, it should be operated when the current flows 3A.

Therefore, it suffices for the power transformer to output an output that allows the operating element circuit OE to operate when 3 A flows in the input winding.

In the above-described embodiment of the present invention, there is no problem because the voltage required for circuit operation is obtained at 1.68A.

Actually, it is extremely rare to operate the overcurrent relay at 60% of the rated current, and in general, it will operate when the rated current is greatly exceeded, so in the event of an accident, the output of the power transformer will Since a higher output voltage can be obtained, there is no problem at all.

It should be noted that the input current of the power transformer 1 is set as one and the number of turns is changed, and the input current for obtaining the operable output of the operating element circuit is measured at the output winding.
It was 0.5A, 1.0A for 5 turns, 1.7A for 3 turns, 2.5A for 2 turns, and 5A for 1 turn.

As the number of turns of each input winding of the power transformer increases, the load impedance of the current transformer installed on the line increases, and the linearity of the secondary current characteristic with respect to the primary current deteriorates. The amount of heat generated under the conditions of the overload withstand test described above increases, so it is better to minimize it, but if it is too small, an output voltage that can operate the operating element circuit with a current of 60% of the above-mentioned minimum rated current will be obtained. I will not be able to. From the above experimental example, at least 2 turns are required.

The above object can be achieved if the difference in the number of turns between the two input windings is 2 to 3 turns.

G. Effect of the Invention Since the present invention has one power transformer as described above,
Coupled with the miniaturization of circuit components using semiconductor integrated circuits, this type of relay can be miniaturized, and the short-circuit accident between the R phase and T phase where the current transformer is installed, which was previously feared, or the terminal Even if a connection error occurs, the power supply required for operation is secured and the relay operates reliably due to the difference in the number of turns of the two input windings of the power supply transformer.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 2 is a circuit configuration diagram of a conventional static overcurrent relay. 1 ... Power transformer, IP1, IP2 ... Input winding, IS ... Output winding, 2 ... Rectifier circuit, 3 ... Power supply circuit, OCR ... Operating element circuit.

Claims (1)

[Claims] 1. An operating element circuit in a static overcurrent relay,
In a device provided with a signal transformer for detecting current and a power transformer for the operating element circuit, the power transformer is a single transformer including an output winding and two input windings. A static overcurrent relay which is not a transformer and has a difference in the number of turns of these two input windings.