JPH06101267B2 - Relay circuit for overcurrent lock of automatic switch - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an overcurrent lock relay circuit for an automatic switch, which can suppress the opening time delay of the switch and facilitate adjustment of the overcurrent lock current value.

[Conventional technology]

As an overcurrent lock circuit used in a conventional automatic switch, there is, for example, one shown in FIG. This circuit is a switch 1 that opens and closes the main circuit consisting of R phase, S phase and T phase,
Current transformers CT ₁ and CT ₂ (hereinafter,
Simply referred to as CT ₁ and CT ₂ ), variable resistors 2 and 3 and bridge rectifiers 4,5 connected in parallel to CT ₁ and CT ₂ , respectively, and switch 1 for switching in parallel connected to bridge rectifiers 4,5. A magnet coil CC (hereinafter simply referred to as CC), a holding coil HC that is disconnected from the circuit when the switch 6 is closed, and is connected in series with CC when the switch 6 is open, and a switch operating power supply 7 that receives power from the main circuit. And a bridge rectifier 8 arranged between the power source 7 and CC and HC. CC is always excited by CT ₁ and CT ₂ . FIG. 3B shows the plunger 10 for closing the switch 1. The closing plunger 10 is configured to project in the arrow direction (closing direction) by the magnetic force when the CC is excited to close the switch 1. That is, when the switch is closed, a large magnetic force is generated in the CC by energizing only CC with the switch 6 closed, and after the switch is opened, the exciting current is reduced by opening the switch 6 and connecting CC and HC in series. This reduces power consumption. Reference numeral 11 is a thin non-ferrous metal gap adjustment washer arranged between the plunger 10 and the fixed iron core 12, and the suction force of the CC is slightly adjusted by adjusting the number or thickness of the inserted washers 11. It is configured to be adjustable. By inserting a washer, the CC locking force (opening prohibition force) is weakened. Further, if the resistance value of the variable resistors 2 and 3 is reduced, the current flowing to CC decreases, and if the resistance value is increased, the current flowing to CC increases, so that the attraction force can be adjusted by adjusting the resistance value. Therefore, the suction force is adjusted by adjusting the variable resistors 2 and 3 and the washer 11 so that the load of the mechanism section for making and releasing the opening is adjusted by this adjustment.

In the above configuration, when a short-circuit accident occurs on the load side, the voltage of the power supply 7 decreases and the switch 1 that was in the closed state tries to open. However, according to the overcurrent value based on the short-circuit accident, CT ₁ or A current is generated in CT ₂ based on the current transformation ratio, and that current excites CC, so the switch can be held closed until the substation trips.

[Problems to be solved by the invention]

However, in the overcurrent lock circuit used in the conventional automatic switch, even if an attempt is made to open the switch, the counter electromotive force flows through the bridge rectifiers 8, 4 and 5 so that the attractive force based on the residual magnetism is generated. It acts in the closing direction, and as a result, the opening of the switch 1 may be delayed, and when load current is flowing in the main circuit, electric power is supplied from CT ₁ and CT ₂ , and this becomes even larger. In addition, CC is always excited by CT ₁ and CT ₂ , and the lock value is adjusted by adjusting the resistors 2 and 3 and the washer 11 for the gap connected in parallel to CT ₁ and CT ₂ . However, it also has the following drawbacks.

(A) When an attempt is made to open the switch when there is no load current in the switch main circuit, the counter electromotive force generated in the magnet flows through the bridge rectifier 8, so that the magnetic force remains in the magnet and the opening is delayed.

(B) When trying to open the switch when a non-accident occurs, if a load current less than the lock current value is flowing, the opening force of the switch will be delayed due to the attractive force of the CC excited by the exciting current according to the load current .

(C) Since the washer for the gap is used, the minimum holding voltage for holding the switch 1 in the closed state becomes high.

(D) Since there are two current transformers, CT ₁ and CT ₂ ,
The lock current setting has a bandwidth due to the difference in the number of phases in which the overcurrent flows.

(E) Since the lock current value is set by the adjustment with the gap washer 11, the adjustment is very difficult.

(F) Since the lock value is set by using the parallel resistors 2 and 3 and the gap washer 11 together, the power consumption becomes large and the capacity of the current transformer becomes large.

[Means and Actions for Solving Problems]

The present invention has been made in view of the above, and eliminates the delay of the opening time of the switch that occurs when an attempt is made to open regardless of the presence or absence of the load current flowing in the switch main circuit, and simultaneously In order to facilitate the adjustment and to eliminate the fluctuation of the lock current value bandwidth caused by the difference in the number of CTs where overcurrent flows, a current transformer and a current transformer that generate a current at a level according to the main circuit current. A relay that is set when the current level reaches a predetermined first value and that is reset when the current level drops to a predetermined second value, and a predetermined distribution of current in the current transformer during the setting of the relay. A circuit means for giving a current of a value to the closing coil of the switch and a power supply for operating the switch and the closing coil are provided in series and open / close in conjunction with the switch of the operating power supply to open the switch. Is commanded When open, there is provided an overcurrent lock relay circuit of an automatic switch provided with a switching means for current based on the counter electromotive force is cut off to pass through the charged coil of the closing coil.

〔Example〕

Hereinafter, the relay circuit for overcurrent lock of the automatic switch according to the present invention will be described.

FIGS. 1 (a) and 1 (b) show an embodiment of the present invention.
The same parts as those in the figure are denoted by the same reference numerals, and the duplicated description will be omitted. A switch 25 connected in series between the bridge rectifier 8 and the CC (magnet coil) prevents a current based on the back electromotive force of CC from flowing through the bridge rectifier 8 when the switch operating power supply 7 is turned off. This is for the purpose of interlocking with a switch (not shown) of the switch operating power supply 7. The operating voltage of the relay X ₁ (X ₂ ) that turns on and off based on the current generated in the current transformers CT ₁ and CT ₂ is the variable resistor R
Set by ₁ (R ₂ ). For example, when the rated load current is flowing in the main circuit, relay X ₁ (X ₂ )
It is set so that a voltage of 1 V or less is applied, and it keeps the off state (b contact), for example, 360 to 450 in the main circuit.
The resistor R ₁ (R ₂ ) is set so that the relay X ₁ (X ₂ ) is turned on (a contact) by applying a voltage of 7 V or more when the short-circuit current of A flows. Relay X ₁ (X ₂₎ is interlocked with the contact 30 (31) and contacts 26 (27), the relay X ₁
When (X ₂ ) is on, contact 30 (31) is on and contact 26 (2
7) turns on to contact X ₁ a (X ₂ a), when relay X ₁ (X ₂ ) is off, contact 30 (31) is off, contact 26 (27) is contact X ₁ b (X
It is configured to turn on the ₂ b). The resistance R ₁ (R ₂₎ to be a series resistance R ₃ when the contact 26 is turned on to a contact
(R ₄ ) is provided (resistance R ₃ (R ₄ ) is relay X
₁ to set the off-voltage (X _2)), in series with the diode 20 (21) is provided with a relay X ₁ (X _2). On the other hand, contact
A diode 24 is provided which forms a circulation circuit in series with the magnet coil CC when the 30 (31) is turned on. Further, when the contact 26 (27) is turned on to the a contact, an exciting current is passed through the magnet coil CC. Turn on diode 22
(23) is provided.

With the above configuration, relay X ₁ (X ₂ ) does not operate when the rated current is flowing in the main circuit, so contact 26 (27) is on to contact X ₁ b (X ₂ b) and CT ₁ The current from (CT ₂ ) forms a loop as shown by arrow I ₁ . Therefore, CT ₁ (C
CC is not excited by T ₂ ) and switch 1
No magnetomotive force is generated to delay the opening of the. Next, when an overcurrent of a predetermined level (for example, 360 to 450 A) flows in the main circuit, a predetermined operating voltage is applied to the relay X ₁ or X ₂ (depending on the phase in which the overcurrent flows) to make contact 26 or 27. X ₁ a
Alternatively, the contact 30 or 31 is turned on at the same time when X ₂ a is turned on. Therefore, a current according to the current generated in CT ₁ or CT ₂ based on the overcurrent can be made to flow in CC, and the closed state of the switch 1 can be maintained even if the voltage of the power supply 7 drops. In this case, since the loop including the CC and the diode 24 is formed, it is possible to circulate the current based on the counter electromotive force generated in the CC, thereby ensuring the stable operation of the CC. At the same time, the resistors R ₃ and R ₄ are inserted in series in the relay X ₁ or X ₂ . When the substation trips during this time and the voltage applied to the relay X ₁ or X ₂ falls below a predetermined value (for example, 1V), the relay X ₁ or X ₂ returns to the non-operation state. Therefore, the contact 26 or 27 is turned on to the contact X ₁ b or X ₂ b, and at the same time, the switch 30 or 31 is turned off, the excitation of CC is released, and the switch 1 is opened.

Next, the voltage waveforms shown in FIGS. 2 (a) and 2 (b) are synchroscopes obtained by observing the voltage waveforms on the anode side (P ₁ ) and the cathode side (P ₂ ) of the diode 20 (21) before and after the relay operation. It was observed by. Here, FIG. 2 (a) shows the voltage waveform before the relay X ₁ (X ₂ ) operates, and the waveform A shows the diode 20 (21) when the forward voltage is applied to the diode 20 (21). ) Shows that the voltage rises at P _{1 and} stops, becoming flat. That is, when the voltage rises to the threshold value of the diode 20 (21), the diode 20 (21) becomes conductive, a current flows, and the voltage becomes flat. Further, the waveform B shows that when a reverse voltage is applied to the diode 20 (21), the diode 20 does not conduct, and the contact 26 (2
It shows that current does not flow because the X ₁ a (X ₂ a) contact in 7) is off, and therefore the voltage waveform rises to the maximum value at P ₂ . Next, FIG. 2 (b) shows the voltage waveform after the relay operation, and the waveform A shows that when the forward voltage is applied to the diode 20 (21), the diode 20 ( 21) conducts, showing that the voltage rise at P ₁ stops and becomes flat, and waveform B shows that when a reverse voltage is applied to diode 20 (21),
The X ₁ a (X ₂ a) contact of contact 26 (27) is turned on to form a closed circuit containing CC, causing diode 22 (23) to conduct and the voltage at P _{2 to} be diode 22 (23). It shows that the value rises only up to the threshold value of.

In the above embodiment, since the switch 25 that is turned off when the power supply 7 is turned off is provided, when the power supply 7 is turned off to open the switch when a non-accident occurs, the main circuit is less than the lock current value. Even if the load current of is flowing, the switch 25 interlocking with the power supply 7 is also turned off, so that the bridge rectifier 8 is disconnected and the current due to the counter electromotive force does not flow, so that the delay of the opening of the switch 1 is prevented. can do.

〔The invention's effect〕

As described above, according to the overcurrent locking relay circuit of the automatic switch of the present invention, when the overcurrent reaches a predetermined level, the current generated in the current transformer according to the overcurrent is applied to the closing coil. When a command is issued to open the switch, the switch provided in series between the operating power supply and the closing coil is opened, and the current based on the back electromotive force of the closing coil is changed. Since the passage through the closing coil is blocked, it eliminates the delay in the opening time of the switch that opens after the substation trips due to the occurrence of a short-circuit accident, and simplifies the adjustment of the overcurrent lock current value. Further, it is possible to eliminate the fluctuation of the lock current value bandwidth caused by the difference in the number of CTs through which the overcurrent flows.

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are explanatory views showing the circuit of one embodiment of the present invention and the relationship between the making coil and the plunger, and FIG.
FIGS. 3A and 3B are explanatory views showing voltage waveforms on the diode anode side and cathode side before and after the relay operation in the present invention, and FIGS. 3A and 3B are conventional overcurrent lock circuits. Explanatory drawing of. Code 1 …… Switch, 2,3 …… Variable resistor 4,5,8 …… Bridge rectifier 6 …… Switch, 7 …… Switch operating power supply 10 …… Plunger, 11 …… Gap washer 12 ...... Fixed iron core 20,21,23,24 ...... Rectifier, 25 ...... Switch 26,27 ...... Switch, 30 ...... Switch

Claims (1)

[Claims] 1. A current transformer for generating a current at a level according to a main circuit current in a distribution line for closing or opening a switch provided in a main circuit based on a command for making or breaking the current, and the current transformer. A relay that is set when the current level of the transformer reaches a predetermined first value and reset when the current level drops to a predetermined second value; and the current of the current transformer throughout the setting of the relay. Circuit means for applying a current of a predetermined distribution value to the closing coil of the switch, and is provided in series between the operating power supply of the switch and the closing coil, and is interlocked with the switch of the operating power supply. Switch means for opening and closing, opening when the opening of the switch is instructed, and blocking a current based on the back electromotive force of the closing coil from passing through the closing coil. Automatic opening Relay circuit for closed circuit overcurrent lock.