Mechatronic circuit-breaker device

Abstract

The disclosure relates to a mechatronic circuit-breaker device adapted to break an electrical current flowing through electrical power transmission means, the device including a main branch comprising at least one electromechanical switch-disconnector connected in series with at least one breaker cell itself electrically in parallel with a snubber and a first voltage surge limiter; an auxiliary branch electrically in parallel with the main branch and comprising at least one power electronic switch, connected in series with at least one capacitor, itself electrically in parallel with its discharge resistance and a second voltage surge limiter. The first voltage surge limiter has a sharper voltage-current characteristic and offering a much steeper slope at low currents than the second surge limiter.

Claims

1. A mechatronic circuit-breaker device adapted to break an electrical current flowing through electrical power transmission means, the mechatronic circuit-breaker device comprising: a main branch comprising at least one electromechanical switch-disconnectorconnected in series with at least one breaker cell that is electrically in parallel with a snubber and a first voltage surge limiter; and an auxiliary branch electrically in parallel with the main branch and comprising at least one power electronic switch, connected in series with at least one capacitor, that is electrically in parallel with its discharge resistance and a second voltage surge limiter, the first voltage surge limiter having a sharper voltage-current characteristic and a steeper slope at low currents than the second voltage surge limiter.

2. The mechatronic circuit-breaker device according to claim 1, wherein the first voltage surge limiter has a voltage-current characteristic that is approximated, in a first operating area, with a first relation: $\frac{U_{103}}{U_{\mathrm{a\_p}}}=\sqrt[\mathrm{alpha\_p}]{\frac{I_{103}}{I_{\mathrm{a\_p}}}}$ $\mathrm{For}{I}_{103}>0$ $\mathrm{And}$ $\frac{U_{103}}{U_{\mathrm{a\_n}}}=-\left[\sqrt[\mathrm{alpha\_n}]{\frac{-I_{103}}{I_{\mathrm{a\_n}}}}\right]$ $\mathrm{For}{I}_{103}<0$ where alpha_p, alpha_n, U.sub.a_p, U.sub.a_n, I.sub.a_p and I.sub.a_n are positive characteristic values for the first voltage surge limiter, wherein the second voltage surge limiter has a voltage-current characteristic that is approximated, in a second operating area, with a second relation: $\frac{U_{1124}}{U_{\mathrm{b\_p}}}=\sqrt[\mathrm{béta\_p}]{\frac{I_{1124}}{I_{\mathrm{b\_p}}}}$ $\mathrm{For}{I}_{1124}>0$ $\mathrm{And}$ $\frac{U_{1124}}{U_{\mathrm{b\_n}}}=-\left[\sqrt[\mathrm{béta\_n}]{\frac{-I_{1124}}{I_{\mathrm{b\_n}}}}\right]$ $\mathrm{For}{I}_{1124}<0$ where béta_p, béta_n, U.sub.b_p, U.sub.b_n, I.sub.b_p and I.sub.b_n are positive characteristic values for the second voltage surge limiter, and wherein alpha _p is greater than béta_p and béta_n.

3. The mechatronic circuit-breaker device according to claim 2, wherein at least one ofalpha_p and alpha_n are greater than 30.

4. The mechatronic circuit-breaker device according to claim 2, wherein at least one of béta_p and béta_n are in a range of 10 to 20.

5. The mechatronic circuit-breaker device according to claim 2, wherein alpha_p and alpha_n have the same value.

6. The mechatronic circuit-breaker device according to claim 2 wherein alpha_p and alpha_n have different values.

7. The mechatronic circuit-breaker device according to claim 2, wherein at least one of U.sub.a_p and U.sub.a_n have the same value, and the constants I.sub.a_p and I.sub.a_n n have the same value.

8. The mechatronic circuit-breaker device according to claim 2, wherein at least one of U.sub.a_p and U.sub.a_n have different values and the constants I.sub.a_p and I.sub.a_n have different values.

9. The mechatronic circuit-breaker device according to claim 2 wherein béta_p and béta_n have the same value.

10. The mechatronic circuit-breaker device according to claim 2, wherein béta_p and béta_n have different values.

11. The mechatronic circuit-breaker device according to claim 2, wherein a least one of U.sub.b_p and U.sub.b_n have the same value, and the constants I.sub.b_p and I.sub.b_n have the same value.

12. The mechatronic circuit-breaker device according to claim 2, wherein at least one of U.sub.b_p and U.sub.b_n have different values, and the constants I.sub.b_p and I.sub.b_n have different values.

13. The mechatronic circuit-breaker device according to claim 1, wherein the first voltage surge limiter is a semiconductor component of a type of power Zener diode and the second voltage surge limiter is a ZnO-type component.

14. The mechatronic circuit-breaker device according to claim 1, wherein the first voltage surge limiter is a set of one or more semiconductor components of a type of Transil diodes and the second voltage surge limiter is a set of one or more ZnO-type components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other advantages and features of the invention become more clearly apparent on reading the detailed description given with reference to the following figures, in which:

(2) FIG. 1 shows an electrical architecture of a sub-part of a mechatronic circuit-breaker device according to an embodiment of the invention, with emphasis on the main and auxiliary branches;

(3) FIG. 2 shows curves representing the currents flowing respectively in main and auxiliary branches of the mechatronic circuit-breaker according to an embodiment of the invention, as functions of time;

(4) FIG. 3 shows the characteristic curves of the voltage in voltage surge limiters of the mechatronic circuit-breaker according to an embodiment of the invention, as a function of the current.

DETAILED DESCRIPTION

(5) FIG. 1 shows an electrical architecture of a sub-part of a mechatronic circuit-breaker device 1 according to an embodiment of the invention intended to break high direct currents in transmission networks L in a peak-to-peak voltage range up to 320 kV DC or more, with emphasis on the main and auxiliary branches.

(6) Such a circuit-breaker device is well known of the person skilled in the art. Consequently, only components essential to the present invention are described here.

(7) Such a device 1 comprises firstly a main branch 10 in which the primary current flows under steady conditions.

(8) In parallel with the main branch 10 there is provided an auxiliary branch 11.

(9) The main branch 10 comprises an electromechanical switch-disconnector 100 consisting of two vacuum interrupters (vacuum bottles), electrically in series with a breaker cell 101. This breaker cell 101 comprises at least one power electronic switch as for example an insulated gate bipolar transistor (IGBT) 1010. The main branch can comprise more than one electromechanical switch-disconnector, connected in series or in parallel, and more than one power electronic switch, connected in series or in parallel. Similarly, the electromechanical switch-disconnector 100 can be designed with a various number of vacuum interrupters, ore even with a various type of interrupters like gas interrupters.

(10) Electrically in parallel with the breaker cell 101 is a snubber 102, limiting the rate of rise of voltage. The snubber is constituted of a diode 1020 electrically in series with a capacitor 1021, itself electrically in parallel with its discharge resistor 1022. The capacitor 1021 controls the rate of rise of the voltage at its terminals when the transistor 1010 is switched to the OFF state. The diode 1020 prevents violent discharging of the capacitor 1021 when the transistor 1010 begins to conduct. Finally, the resistor 1022 enables slow discharging of the capacitor 1021. Optionally, a resistor can be connected in parallel with the diode 1020, whenever a transient backward current is needed during the commutation. In other words, this voltage snubber 102 associated with the IGBT transistor 1010 protects the IGBT by controlling the rate at which the voltage across its terminals increases when it switches from the conducting (ON) state to the non-conducting (OFF) state.

(11) Also electrically in parallel with the breaker cell 101 is a voltage surge limiter 103. It is designed to limit the voltage to a value less than the withstand voltage of the IGBT transistor 101. FIG. 1 and the description refer to one voltage surge limiter 103, but the invention is not limited to this case and also concerns a set of voltage surge limiters.

(12) The voltage surge limiter 103 will be detailed with reference to FIG. 3 in the following.

(13) The auxiliary branch 11 comprises a thyristor 111 or a plurality of power thyristors in cascade. FIG. 1 and the description refer to one thyristor 111, but the invention is not limited to this case and also concerns several power electronics components from other technologies connected in cascade.

(14) The auxiliary branch 11 also comprises, electrically in series with the thyristor 111, a capacitor 1120, itself electrically in parallel with its discharge resistor 1125.

(15) The capacitor 1120 may be associated with one or more inductors in series, as well as one or more resistors in series. These components are not shown in FIG. 1.

(16) The capacitor 1120 and its discharge resistor 1125 are protected by an auxiliary voltage surge limiter 1124 connected electrically in parallel with them. This surge limiter 1124 is used as well as defining and limiting the voltage that appears at the terminals of the auxiliary branch 11 when the primary current flows.

(17) In a preferred embodiment, the voltage surge limiter 1124 is a ZnO-type voltage surge limiter or is constituted of a set of ZnO-type surge limiters. FIG. 1 and the description refer to one voltage surge limiter 1124, but the invention is not limited to this case and also concerns a set of voltage surge limiters.

(18) Note that FIG. 1 shows only a single electromechanical switch-disconnector 100 but in fact there may be a plurality of electromechanical switch-disconnectors connected in series or in parallel.

(19) Note also that a power transistor as such is merely symbolically represented without showing its associated transfer capacitors and gate control device. The same holds for the power thyristor.

(20) The operation of the mechatronic circuit-breaker device 1 is the following.

(21) Under steady conditions, i.e. in normal operation of the network L, the transistor 1010 of the main branch is in the ON (conducting) state, and a current I.sub.main passes through it and in the main branch 10. The value of the current I.sub.main depends on a load R.sub.load.

(22) In the event of a fault occurring in the network L and being reflected by a current surge, the monitoring and control system (not shown) switches the transistor 1010 from its ON state to its OFF state. The current is then switched from the transistor 1010 to the diode 1020 and the capacitor 1021. The voltage across the capacitor 1021 rises until it reaches the threshold voltage of the voltage surge limiters 103 that becomes conducting and prevents further voltage rise.

(23) FIG. 2 shows curves of the currents I.sub.main and I.sub.aux respectively in the main and auxiliary branches of the mechatronic circuit-breaker 1 as a function of time.

(24) In case of a fault occurring at time t0, the current steadily increases. The current first flows in the main branch as indicated by the curve I.sub.main which increases between times t0 and t1. The current I.sub.aux remains zero until time t1.

(25) When the transistor 1010 is switched into its OFF state, a fast increase in the voltage occurs at the terminals of the main branch 10 and the auxiliary branch 11. The value of the voltage is limited by the voltage surge limiter 103 indicating that the capacitor 1021 is charged.

(26) Subsequently, driving energy is supplied to the gate control module of the power thyristor 111. This energy enables conduction to be started in the power thyristor 111. The current then commutates in the auxiliary branch 11 as indicated by the crossing of the curves I.sub.main and I.sub.aux at time t1. At this time, current I.sub.main becomes substantially zero and current I.sub.aux grows.

(27) Synchronously the electromechanical switch-disconnectors 100 start opening.

(28) Gradually, as the voltage increases in the capacitor 1120 of the auxiliary branch 11 and therefore across the main branch 10, a residual current flows through the voltage surge limiter 103 and therefore through the electromechanical switch-disconnectors 100.

(29) If the residual current is too large, an electric arc will be generated across the contacts of vacuum bottles 100 during its opening operation. This could erode the bottles' contacts and this decreases their service life.

(30) The voltage surge limiter 103 and the auxiliary voltage surge limiter 1124 are respectively rated so that, when the current I.sub.aux is well-established in the auxiliary branch 11, the magnitude of the residual current I.sub.main in the main branch 10 is substantially zero, typically much less than 1 A, so as to enable the vacuum interrupters of the electromechanical switch-disconnector 100 to open without significant electrical erosion, because of the virtual absence of electrical arcing.

(31) The mechatronic circuit-breaker device 1 stays in this state until the contacts of the switch-disconnectors 100 are sufficiently separated from each other to support a high voltage. Meanwhile the current to be interrupted may reach values of several kilo amps.

(32) Beyond time t2, the current is commutated into another branch (not shown or discussed in this document) connected in parallel to the main and auxiliary branches. Consequently, no current flows neither in the main branch 10 nor in the auxiliary branch 11, apart from capacitive currents and residual leakage currents caused by imperfections of the components. These currents are if necessary eliminated by conventional isolation means electrically in series with the mechatronic circuit-breaker.

(33) Beyond time t2, currents I.sub.main and I.sub.aux are substantially zero. FIG. 3 shows curves of the voltages U.sub.103 and U.sub.1124 respectively in the voltage surge limiters 103 and 1124 as a function of the current.

(34) The voltage surge limiter 103 has a sharper voltage-current characteristic and offering a much steeper slope at low currents than the surge limiter 1124.

(35) For example, the voltage surge limiter 103 is a semiconductor component of the type “Transil diode” or of a similar type. The voltage surge limiter 1124 may be a ZnO-type component.

(36) The idea is to use a voltage surge limiter 103 with highly nonlinear characteristics to set the voltage of the main branch 10 before opening the switch-disconnectors 100.

(37) Thus, during this commutation sequence, the voltage required to force even a very low current through the main branch 10 is always higher than the voltage developed across the auxiliary branch 11 conducting a high current.

(38) This avoids the commutation of current from the auxiliary branch 11 back into the main branch 10, while the value of the current can vary over a wide range and reach values of several kilo amps.

(39) A given voltage U corresponds to a current value I.sub.r for the voltage-current characteristic of the voltage surge limiter 103 and to a current value I.sub.2 for the voltage-current characteristic of the voltage surge limiter 1124. For the given voltage U, the value I.sub.r of the residual current in the vacuum bottles 100 is very low, which ensures an opening of the contacts of vacuum bottles 100 with minimum arc levels.

(40) This avoids the appearance of excessive arc in the vacuum bottles of the electromechanical switch-disconnector 100, causing their contact to deteriorate too quickly.

(41) The minimum voltage on the auxiliary branch 11 is sufficient to be able to perform subsequent switching into other branches that are not shown in this document.

(42) The voltage-current characteristic U.sub.103(I.sub.103) of the voltage surge limiter 103 of the main branch 10 can be approximated, in the operating area through:

(43) $\frac{U_{103}}{U_{\mathrm{a\_p}}}=\sqrt[\mathrm{alpha\_p}]{\frac{I_{103}}{I_{\mathrm{a\_p}}}}$$\mathrm{For}{I}_{103}>0$$\mathrm{And}$$\frac{U_{103}}{U_{\mathrm{a\_n}}}=-\left[\sqrt[\mathrm{alpha\_n}]{\frac{-I_{103}}{I_{\mathrm{a\_n}}}}\right]$$\mathrm{For}{I}_{103}<0$

(44) Where alpha_p, alpha_n, U.sub.a_p, U.sub.a_n, I.sub.a_p and I.sub.a_n are positive characteristic values for the first voltage surge limiter 103.

(45) The voltage current characteristic U.sub.1124(I.sub.1124) of the voltage surge limiter 1124 of the auxiliary branch 11 can be approximated, in the operating area through:

(46) $\frac{U_{1124}}{U_{\mathrm{b\_p}}}=\sqrt[\mathrm{béta\_p}]{\frac{I_{1124}}{I_{\mathrm{b\_p}}}}$$\mathrm{For}{I}_{1124}>0$$\mathrm{And}$$\frac{U_{1124}}{U_{\mathrm{b\_n}}}=-\left[\sqrt[\mathrm{béta\_n}]{\frac{-I_{1124}}{I_{\mathrm{b\_n}}}}\right]$$\mathrm{For}{I}_{1124}<0$

(47) Where béta_p, béta_n, U.sub.b_p, U.sub.b_n, I.sub.b_p and I.sub.b_n are positive characteristic values for the second voltage surge limiter 1124.

(48) The constant alpha_p is greater than the constants béta_p and béta_n.

(49) Thus, the first voltage surge limiter, used in the main branch, has a voltage-current characteristic of much steeper slope and a sharper transition at low currents than the second surge limiter.

(50) According to different embodiments, the constants alpha_p and alpha_n can be different, as similarly and respectively for béta_p and béta_n, U.sub.a_p and U.sub.a_n, I.sub.a_p and I.sub.a_n, U.sub.b_p and U.sub.b_n, I.sub.b_p, and I.sub.b_n.

(51) According to different embodiments, the constants beta_p and beta_n could be equal, as similarly and respectively for U.sub.b_p and U.sub.b_n, I.sub.b_p and I.sub.b_n, as this is the case for usual Z.sub.nO surge arrestors.

(52) According to different embodiments, the constants alpha_p and/or alpha_n are greater than 30 or greater than 50 or greater than 100.

(53) According to different embodiments, the constants béta_p and/or béta_n are in the range of 10 to 20 or in the range of 13 to 19 or are substantially equal to 17.