ES2420531T3 - Hybrid circuit breaker - Google Patents

Abstract

A hybrid circuit breaker that interrupts the fault currents comprising: - a mechanical switch (31) through which a normal current passes, the mechanical switch being arranged to open in case of being exposed to a fault current; and - a semiconductor breaker device (32) to which a fault current is switched, the semiconductor breaker device being arranged to interrupt said fault current, characterized in that - the mechanical switch has a cam (33) of the breaker with two contacts (33a-b) that rely on the seasonal contacts (34a-b) of a circuit when it is closed, the rotary switch cam being rotatable around a rotation axis35 to allow the two contacts of the breaker cam to withdraw of the stationary contacts so that the mechanical switch opens; - the two contacts of the cam of the breaker are located at different distances (x1, x2) from the axis of rotation so that the separations (z1, z2) between the two contacts of the cam of the breaker and the two stationary contacts are different when opened the mechanical switch; and - the semiconductor circuit breaker device is connected in parallel with the contact (33b) of the cam of the breaker and of the stationary contact (34b), which separates to the maximum when the mechanical switch is opened.

Description

Hybrid circuit breaker

Technical Field of the Invention

The present invention is generally related to hybrid circuit breakers.

Description of the related art and background of the invention

To overcome the most serious disadvantages of solid state circuit breakers, various hybrid circuit breakers have been proposed. The hybrid circuit breaker is a combination of a conventional mechanical circuit breaker and a solid state circuit breaker. In nominal operation the current flows through the mechanical circuit breaker and only the solid state circuit breaker is used during breakdowns. As in the case of solid state circuit breakers, unidirectional and bidirectional switches can be used depending on the requirements of the application.

A two-way hybrid circuit breaker including a conventional mechanical circuit breaker 11 and a solid state circuit breaker 12 during different stages of operation are shown in the schematic diagrams of the circuit.

During a pole-to-pole fault the current flows through the mechanical circuit breaker 11. In a moment of time the mechanical circuit breaker 11 is opened and the solid state circuit breaker 12 is connected. As the mechanical circuit breaker 11 is opened, an arc is initiated through the mechanical circuit breaker 11 and if the arc voltage is sufficient, the hybrid circuit breaker will switch the fault current to the solid state circuit breaker 12 as illustrated in Figure 1a. After the switching of the current and the extinction of the arc, the fault current flows through the solid state circuit breaker 12 as illustrated in Figure 1b. To avoid arc re-ignition, the conduction time must be long enough to allow the distance between contacts in the mechanical circuit breaker 11 to cool to prevent re-ignition. When the solid state circuit breaker 12 is disconnected, the energy stored in the loop inductance is absorbed with the surge protection element as illustrated in Figure 1c.

Figures 2a-b are diagrams of arc current and arc voltage, respectively, as a function of the operation time of the bi-directional hybrid circuit breaker of Figures 1a-c.

The hybrid circuit breaker requires the same amount of semiconductors as the complete solid state circuit breaker. However, for the hybrid circuit breaker, conduction losses are not a problem because the nominal operating current flows through the mechanical circuit breaker. In addition, for the same reason, cooling is not a crucial problem for the hybrid circuit breaker. However, heat sinks are required because the fault current is switched to the solid state circuit breaker during breakdowns.

WO2008 / 153575 discloses a device according to the preamble of claim 1.

Summary of the invention

However, the use of conventional mechanical circuit breakers in combination with a solid state circuit breaker is a challenge due to the limited capabilities of the solid state circuit breaker current specification. The mechanical circuit breaker can interrupt a fault current of a few tens of kiloamperes where controllable solid-state devices can only typically interrupt currents of some kiloamperes.

In addition, if the loop inductance is high, a long switching time is required. A long switching time has, however, an additional increase in the magnitude of the fault current and therefore the solid state circuit breaker has to interrupt very high currents.

Furthermore, the conduction time of the solid state circuit breaker is critical because (i) a long conduction time is required to completely switch the current from the mechanical circuit breaker to the solid state circuit breaker,

(ii) a long conduction time is required when the loop inductance is high, and (iii) a long conduction time is required to extinguish the arc voltage of the mechanical circuit breaker, that is to ensure that no current does not flow through of the mechanical circuit breaker. However, long driving times result in high conduction losses and, as a result, a heating of the device that can lead to device failures.

Accordingly, it is an object of the present invention to have a hybrid circuit breaker that addresses the above problems.

It is a particular object of the invention to have a hybrid circuit breaker, which has a lower peak current, a shorter switching time, and a shorter driving time.

It is a further object of the invention to have a hybrid circuit breaker, such that it has a rapid detection of

breakdowns, and a shorter downtime.

It is a further object of the invention to have a hybrid circuit breaker, such that it is compact, robust and reliable.

These objects among others are, according to the present invention, achieved by hybrid circuit breakers as claimed in the appended claims of the patent.

According to one aspect of the invention, a hybrid circuit breaker is provided that cuts the fault currents, where the circuit breaker comprises a mechanical switch through which a normal current passes, a mechanical switch being arranged to open in case of being exposed to a fault current, and a solid state or semiconductor circuit breaker device, to which the fault current is switched, the semiconductor circuit breaker device being arranged to interrupt the fault current. The mechanical switch has a breaker cam with two stationary contacts that impact with stationary contacts of a circuit when it closes, the rotary switch cam being around an axis of rotation to allow the two contacts of the breaker cam to withdraw of the stationary contacts so that the mechanical switch opens. The cam of the breaker is arranged asymmetrically, for example, the two contacts of the cam of the breaker are located at different distances from the axis of rotation, so that the separations between the two contacts of the cam of the breaker and the two stationary contacts They are different when the mechanical switch opens. The semiconductor circuit breaker device is connected in parallel with the breaker cam contact and with the stationary contact that are separated as much as possible when the mechanical switch opens.

It is obtained by such a hybrid circuit breaker, a faster interruption and a significantly lower cut-off current.

More in detail, the mechanical switch will be locked in an open position with a lower current and therefore the dead time will be shorter, implying a significantly lower cutting current. A lower cut-off current, in turn, results in a considerably lower energy dissipation in the semiconductor breaker device and therefore, the space occupied by the device can be reduced.

In addition, a control strategy is proposed in combination with the asymmetric hybrid circuit breaker.

In one embodiment, the inventive inventive semiconductor circuit breaker device accordingly comprises a control unit arranged to control the switching of the fault current to the semiconductor circuit breaker device as a function of time. The switching of the current is allowed to increase during the control of the fault in a controlled manner.

Preferably, the control unit is configured to completely switch the fault current to the semiconductor breaker device for a certain period of time, when the mechanical switch is fully opened and locked in the open position to ensure that the space between contacts cools. enough. When the determined period of time ends, the current is interrupted through the semiconductor circuit breaker device. Thus, it can be ensured that the current is interrupted without the risk of reignition in the separation between contacts.

In a particular implementation, the semiconductor circuit breaker device comprises a bipolar isolated gate transistor (IGBT) and the control unit, which can be a door control unit, is configured to control the fault current switching to the circuit breaker device. semiconductors with door voltage control means of the isolated bipolar door transistor.

The door control unit can measure the voltage through the semiconductor breaker device and when the voltage across the device increases and reaches a certain threshold level, this implies that a fault occurs, and the control of the switching of the fault current to the semiconductor circuit breaker device. The door tension then increases over time, preferably in a staggered manner, in a controlled manner.

The hybrid circuit breaker of the present invention may be a unidirectional device or a bidirectional device capable of interrupting a fault DC current in any direction or a fault AC current. The hybrid circuit breaker preferably has a nominal voltage of up to 1 kV.

Additional details of the invention are set forth in the dependent claims.

The advantages of the present invention may include:

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fast fault detection,

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a low fault current connection,

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a comparatively short dead time,

3

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a comparatively short switching time,

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a short driving time of the semiconductor breaker device,

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low cutting current,

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you just have to manipulate (dissipate) low energy using the semiconductor circuit breaker device,

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compact solution,

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Low temperature rise in the semiconductor breaker device due to the lower peak current.

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Ability to quickly interrupt and limit current and

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Use in both AC and DC power interruptions.

Other additional features of the invention, and advantages thereof, will be apparent from the following detailed description of the preferred embodiments of the present invention, provided below and by the accompanying Figures 1-5, which are provided by way of for illustration only, and therefore are not limiting of the present invention.

Brief description of the drawings

Figures 1a-c show in schematic circuit diagrams a bi-directional hybrid circuit breaker during different operating states, according to the prior art.

Figures 2a-b are diagrams of arc current and arc voltage, respectively, as a function of time during operation of the bi-directional hybrid circuit breaker of Figures 1a-c.

Figure 3 shows schematically, partially in a side view, partially in a circuit diagram, a hybrid circuit breaker according to an embodiment of the present invention.

Figure 4 is a diagram of the current versus time during operation of the hybrid circuit breaker of Figure 3.

Figures 5a-b illustrate how a bipolar gate transistor isolated from a semiconductor circuit breaker device of a hybrid circuit breaker of Figure 3 controls the current through the semiconductor circuit breaker device by introducing a variable resistor controlled by a gate voltage. of the isolated bipolar gate transistor. Figure 5a illustrates the variable resistance while Figure 5b is a diagram of the gate voltage and the variable resistance as a function of time, during operation of the hybrid circuit breaker.

Detailed description of the embodiments

A hybrid circuit breaker that interrupts fault currents according to an embodiment of the invention is illustrated in Figure 3. The hybrid circuit breaker comprises a mechanical switch 31 and has a nominal voltage of up to 1 kV.

During normal operating conditions the current is passed through the mechanical switch 31, but when exposed to a fault current, the mechanical switch 31 is arranged to be opened, thereby switching the current to the circuit breaker device 32 semiconductors The semiconductor circuit breaker device 32 is optionally arranged to interrupt the fault current.

The mechanical switch 31 has a cam 33 of the breaker with two contacts 33a-b that impact the stationary contacts 34a-b of a circuit when it is closed. The cam 33 of the breaker is rotatable about an axis 35 of rotation to allow the two contacts 33a-b of the cam 33 of the breaker to be removed from the stationary contacts 34a-b so that the mechanical switch 31 opens. Figure 3 illustrates the mechanical switch 31 in an open state.

Note that Figure 3 only illustrates mechanical switch 31 schematically. The exact shapes of the contacts may be different from those illustrated and in addition, the mechanical switch 31 is provided with a device to keep the mechanical switch 31 in an open state, and for subsequent closures of the mechanical switch 31 (when the fault has been controlled ).

The two contacts 33a-b of the cam 33 of the breaker are located at different distances x1, x2 of the rotation axis 35, so that the separations z1, z2 between the two contacts 33a-b of the cam 33 of the breaker and the two Stationary contacts 34a-b are different when mechanical switch 31 opens or is open. Such a mechanical switch 31 is called an asymmetric mechanical switch. Preferably, contacts 33a-b of cam 33 of the breaker are

placed on opposite sides of the rotation axis 35.

The semiconductor breaker device 32 is connected in parallel with the contact 33b of the cam 33 of the breaker and with the stationary contact 34b which are separated as much as possible when the mechanical switch 31 is opened.

Thus, the mechanical switch 31 can be locked in an open position with a lower current and therefore the dead time will be shorter implying a significantly lower cutting current.

The semiconductor circuit breaker device 32 comprises a bipolar insulated gate transistor 36 (IGBT), a diode bridge 37, and a door control unit 38. The diode bridge is commonly used in hybrid circuit breakers so that they are capable of interrupting a fault DC current in any direction or an AC fault current, see for example documents US 2005/146814 and US 6, 760, 202, the contents of which are incorporated herein by reference.

The door control unit 38 is configured to measure the voltage through the semiconductor circuit breaker device 32. When the voltage increases and reaches a certain threshold level, this implies that a fault occurs. As a result, rapid fault detection can be achieved.

Then, the door control unit 38 is arranged so that it controls the switching of the fault current to the semiconductor breaker device 32 by controlling the gate voltage of the isolated bipolar transistor 36 and the operation of the bipolar transistor 36 of insulated door in its linear region. Thus, the current can be restricted at different levels.

The door control unit 38 controls the switching of the fault current to the semiconductor breaker device as a function of time and the switching of the current is allowed to increase in a controlled manner, by means of gradual changes or step-by-step voltage of bipolar transistor door 36 of insulated door.

Figure 4 is a diagram of the fault current and the current through the semiconductor circuit breaker device, respectively, as a function of time during operation of the hybrid circuit breaker of the invention. The fault current is designated as 41 and the current through the semiconductor breaker device 32 is designated as 42. It can be seen that the bipolar insulated gate transistor 36 operates in the linear region such as 43. The interlock of the switch Mechanical 31 is indicated as 44.

The following parameters are indicated in Figure 4: ion is the level of the fault current where the current begins to switch to the semiconductor circuit breaker device 32 and ton the time at which the semiconductor circuit breaker device 32 is connected, ioff is the peak fault current and toff the instant of time in which the semiconductor circuit breaker 32 is disconnected, and R1, R2, R3, and Rce are resistors of the insulated gate bipolar transistor 36.

Figures 5a-b illustrate how the bipolar insulated gate transistor 36 controls the current through the semiconductor breaker device 32 by introducing a variable resistor controlled by a gate voltage of the insulated gate bipolar transistor 36. Figure 5a illustrates the variable resistance, while Figure 5b is a diagram of the gate voltage Vg and the variable resistance Rvar as a function of time during operation of the hybrid circuit breaker. The values Vg1, Vg2, Vg3, and Vgmax of the gate voltage provide the respective resistance values R1, R2, R3, and Rce.

As can be seen in Figures 4 and 5, at a certain time after the fault has been detected, the bipolar gate transistor 36 isolated from the semiconductor breaker device 32 is connected by applying the lowest voltage Vg1 on the gate of the same. This implies that the semiconductor circuit breaker device 32 has a high resistance and a small amount of the fault current flows through the semiconductor circuit breaker device 32. Then the gate voltage increases allowing a higher current to flow through the semiconductor breaker device. This is repeated, for example, the door voltage gradually increases, until the mechanical switch 31 is locked in a safe position in an open state. Therefore, the semiconductor circuit breaker device 32 functions as a linear regulator.

When the mechanical switch 31 is locked or locked in an open state, it is not possible for the contacts to return. Consequently, the gate voltage increases so that the semiconductor breaker device 32 completely switches the current of the mechanical switch 31. When the current is switched to the semiconductor breaker device 32, the semiconductor breaker device 32 will remain connected for a moment of time. determined to ensure the arc is extinguished. Finally, the semiconductor circuit breaker device is disconnected with a considerably lower peak current compared to the symmetric hybrid circuit breaker.

Claims (9)

1. A hybrid circuit breaker that interrupts fault currents comprising:

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a mechanical switch (31) through which a normal current passes, the mechanical switch being arranged to open in case of being exposed to a fault current; Y

5 -a semiconductor circuit breaker device (32) to which a fault current is switched, the semiconductor circuit breaker device being arranged to interrupt said fault current, characterized by that

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The mechanical switch has a cam (33) of the breaker with two contacts (33a-b) that rest on the stationary contacts (34a-b) of a circuit when it closes, the rotary switch cam being rotatable about an axis 10 35 rotation to allow the two contacts of the breaker cam to be removed from the stationary contacts

so that the mechanical switch opens;

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the two contacts of the cam of the breaker are located at different distances (x1, x2) from the axis of rotation so that the separations (z1, z2) between the two contacts of the cam of the breaker and the two stationary contacts are different when open the mechanical switch; Y

15 - The semiconductor circuit breaker device is connected in parallel with the contact (33b) of the breaker cam and the stationary contact (34b), which separates to the maximum when the mechanical switch is opened.

2.

The hybrid circuit breaker of claim 1 wherein the contacts of the breaker cam are located on opposite sides of the axis of rotation.

3.

The hybrid circuit breaker of claim 1 or 2 wherein the semiconductor circuit breaker device comprises a

20 control unit (38) arranged to control the switching of the fault current to the semiconductor circuit breaker device as a function of time.

Four.

The hybrid circuit breaker of claim 3 wherein the control unit is configured to control the switching of the fault current to the semiconductor circuit breaker device to increase linearly.

5.

The hybrid circuit breaker of claim 3 or 4 wherein the semiconductor circuit breaker device comprises a

25 bipolar insulated gate transistor (36) and the control unit is configured to control the switching of the fault current to the semiconductor breaker device by controlling the gate voltage of the insulated bipolar gate transistor, preferably controlling in steps Gate voltage of the bipolar gate transistor isolated. 6. The hybrid circuit breaker of any one of claims 3-5 wherein the control unit is configured for 30 completely switch the fault current to the semiconductor breaker device for a certain time when the mechanical switch has opened fully.

7.

The hybrid circuit breaker of claim 6 wherein the control unit is configured to interrupt the current through the semiconductor circuit breaker when the determined period of time ends.

8.

The hybrid circuit breaker of any one of claims 3-5 wherein the control unit is configured to

35 initiate control of the switching of the fault current to the semiconductor breaker device in response to the voltage through the semiconductor breaker device. 9. The hybrid circuit breaker of any one of claims 1-8 wherein the semiconductor circuit breaker device comprises a diode bridge (37) such that it is capable of interrupting a fault DC current in any direction or a fault AC current. The hybrid circuit breaker of any one of claims 1-8 wherein the hybrid circuit breaker has a nominal voltage of up to 1kV.