| JP2003098215 | EARTH DETECTION METHOD AND DEVICE IN POWER CONVERSION SYSTEM |
| JP60097279 | PHASE DETECTING METHOD |
| JP61091572 | GROUND CHARGE CURRENT MONITOR |
YANG, Wenguang (Room 17-3-401, Runxingjiayuan Jiugong, Daxing District, Beijing 6, 100076, CN)
JIANG, Wei (Room 361, No. 29 QimingxingyuanYunjing South Street, Tongzhou District, Beijing 1, 100121, CN)
ZHU, Panfeng (Room 1-1-1002, No. 30 Majiapu West Road Fengtai District, Beijing 8, 100068, CN)
YANG, Wenguang (Room 17-3-401, Runxingjiayuan Jiugong, Daxing District, Beijing 6, 100076, CN)
JIANG, Wei (Room 361, No. 29 QimingxingyuanYunjing South Street, Tongzhou District, Beijing 1, 100121, CN)
| CLAIMS 1 . A residual current protection device, wherein said device comprises: a sensor configured to detect the current on the circuit, and output a leakage signal when having detected the residual current; a leakage signal processing unit configured to accumulate the time of said leakage signal, and output the accumulated leakage signal; a comparison unit configured to compare said accumulated leakage signal with preset threshold, and output a shut-off controlling signal when said accumulated leakage signal is bigger than said preset threshold; and a circuit disconnection mechanism configured to shut off said circuit after receiving said shut-off controlling signal. 2. The residual current protection device according to claim 1 , wherein said leakage signal processing unit comprises: an absolute value processing unit configured to perform the absolute value calculation based on said leakage signal, and output absolute value processing leakage signal; an integral processing unit configured to perform time integral of said absolute value processing leakage signal, and output the accumulated leakage signal. 3. The residual current protection device according to claim 1 or 2, wherein further comprises: a delay unit configured to receive the accumulated leakage signal from the leakage signal processing unit, and transmit the signal to said comparison unit after preset delay cycles. 4. The residual current protection device according to claim 3, wherein said delay unit constituted by RC circuit can regulate the delay cycle by setting the parameters of capacitor and resistor. 5. The residual current protection device according to claim 1 or 2, wherein said sensor is a zero sequence instrument transformer which can detect pulsating DC residual current and AC residual current. 6. The residual current protection device according to claim 1 or 2, wherein said circuit disconnection mechanism is an electromagnetic mechanism. 7. The residual current protection device according to claim 1 , wherein further comprises: a filter unit configured between the sensor and the leakage signal processing unit to filter high frequency signal, and only allow the component with leakage characteristics to pass through; a protection unit configured between the filter unit and the sensor to limit the voltage value of leakage signal outputted by the sensor in a preset range; bipolar amplifier unit configured to proportionally amplify the positive and negative signals of the leakage signal filtered by the filter unit, and output the signal to the leakage signal processing unit. 8. A circuit breaker with the residual current protection function, wherein comprises said residual current protection device according to any one of previous claims. |
FIELD OF THE INVENTION
The invention relates to a residual current protection device and a circuit breaker thereof, and more particularly to a residual current protection device and circuit breaker simultaneously detecting alternating current (AC) and direct current (DC) residual faults.
BACKGROUND OF THE INVENTION
Miniature circuit breaker is configured to connect, carry and disconnect the circuit connection in the normal condition or abnormal condition. As a terminal protection device, miniature circuit breakers are widely adopted in the distribution system of various constructions. In order to supply electrical protection for the terminal devices, miniature circuit breakers shut off the connection between the terminals and power supply in the occurrence of abnormal condition, and re-transfer current into the terminal devices until the operation condition gets right.
The residual protection module embedded in the circuit breaker can effectively avoid the danger of electric shock and current leakage. When electrical devices or cables generate current leakage, the residual current generally takes on a sine AC wave; while electrical devices controlled by a rectifier, inverter or clipper generate the current leakage, components such as diodes or thyristor (SCR) etc. in electrical devices vary the current wave, and corresponding signal wave of the current leakage is a pulsating DC wave. As described above, according to the residual current characteristics induced by current leakage, the residual current contains two types: pulsating DC residual current and AC residual current. Curves A and B respectively show the characteristics of two types residual current in figure 1 . As to the pulsating DC residual current, the signal characteristics generally include multiple DC narrow pluses. Due to different characteristics of the residual current, the circuit breakers in prior arts can not utilize general residual current protection device, but adopt different detecting technologies for residual current protection based on different characteristics of residual currents. In prior arts, specific integrated chips are used to perform the pulsating DC residual current protection. The advantages of integrated chips lie in integrated functions such as signal processing, comparison and latching etc. But the disadvantages of specific integrated chips lie in higher power consumption, unsuitable application in the condition of wide voltage range for power supply, difficult to realize anti-time protection for residual current, difficult to realize anti-time protection for residual current, and more complicated periphery circuit.
The voltage transmitted on transmission lines is not stable, and interference signals will occur at any moment. In most cases, the interference signal presents the form of single peak pulse shown as the curve C in Figure 1 . This type of interference signal pulse is similar to the curve of the DC pulsating residual current signal being checked and protected. Hence existing DC pulsating residual current protection breaker is often affected by the interference signal and can not effectively identify the interference signals and real pulsating DC residual current signal, furthermore results in the mis-operation of the breaker.
In addition, due to higher cost of the specific pulsating DC residual current protection devices, the pulsating DC residual current protection devices are seldom adopted in the dedicated condition of AC residual current protection. The object of the present invention is to provide a low-cost protection device with higher anti-interference performance, and such protection device can simultaneously detect AC and pulsating DC residual current so as to meet the market requirement. SUMMARY OF THE INVENTION
An object of the present invention is to overcome above mentioned shortcomings of prior arts, and provide a protection device detecting positive and negative residual current. Such device detects not only AC residual current but also DC residual current.
According to an aspect of the present invention, a residual current protection device is provided. The device comprises: a sensor configured to detect the current on the circuit, and output a leakage signal when having detected the residual current; a leakage signal processing unit configured to accumulate the time of said leakage signal, and output the accumulated leakage signal; a comparison unit configured to compare said accumulated leakage signal with preset threshold, and output a shut-off controlling signal when said accumulated leakage signal is bigger than said preset threshold; and a circuit disconnection mechanism configured to shut off said circuit after receiving said shut-off controlling signal.
According to a preferred embodiment of the present invention, the leakage signal processing unit comprises: an absolute value processing unit configured to perform the absolute value calculation based on said leakage signal, and output absolute value processing leakage signal; an integral processing unit configured to perform time integral of said absolute value processing leakage signal, and output the accumulated leakage signal.
According to another preferred embodiment of the present invention, the residual current protection device further comprises: a delay unit configured to receive the accumulated leakage signal from the leakage signal processing unit, and transmit the signal to said comparison unit after preset delay cycles.
According to another preferred embodiment of the present invention, the delay unit constituted by RC circuit can regulate the delay cycle by setting the parameters of capacitor and resistor. According to another preferred embodiment of the present invention, the sensor is a zero sequence instrument transformer which can detect pulsating DC residual current and AC residual current.
According to another preferred embodiment of the present invention, the circuit disconnection mechanism is an electromagnetic mechanism.
According to another preferred embodiment of the present invention, the residual current protection device further comprises: a filter unit configured between the sensor and the leakage signal processing unit to filter high frequency signal, and only allow the component with leakage characteristics to pass through; a protection unit configured between the filter unit and the sensor to limit the voltage value of leakage signal outputted by the sensor in a preset range; bipolar amplifier unit configured to proportionally amplify the positive and negative signals of the leakage signal filtered by the filter unit, and output the signal to the leakage signal processing unit.
According to another aspect of the present invention, a circuit breaker with the residual current protection function is provided, in which comprises the residual current protection device mentioned above. The new type residual current protection device provided by the present invention utilizes general operational amplifier, takes advantage of less power consumption and adaptively provides the residual current protection in the condition of broad voltage input. The periphery circuit required by the new type residual current protection device takes advantages of a simple configuration, rather excellent performance on Interference Immunity for differential mode and common mode The residual current protection device can effectively detect pulsating DC and AC residual current, and possesses the same identification ability whether the positive or negative wave of the pulsating DC residual current. Meanwhile, the residual current protection solution has good consistency as to the waves of pulsating DC residual current and DC residual current, even with nearly the same sensitivity, and achieves a complete residual current protection function by matching the instrument transformer with Permalloy cores.
BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter of the invention will be explained in more details in the following description with reference to preferred exemplary embodiments which are illustrated in the drawings, in which:
Fig.1 respectively illustrates waves of AC residual current signal, DC residual current signal and interference current signal; Fig.2 illustrates a residual current protection device according to a preferred embodiment of the present invention; and
Fig.3 respectively illustrates the amplified waves of AC residual current signal, DC residual current signal and interference current signal.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig.2 illustrates a detecting circuit of the residual protection device according to a preferred embodiment of the present invention. As shown in Fig.2, the detecting circuit of the protection device mainly comprises a sensor unit 1 , a filter unit 2, an amplifier unit 3, a signal processing unit (4, 5), a comparison unit 7 and a circuit operation unit 8. Alternatively, in another preferred embodiment, the protection device further comprises a delay unit 6 for modulating the delay cycles.
The function of the individual units will be explained in the following description. The sensor unit 1 is configured to detect whether there is residual current on the distribution lines (L, N) for transmission current to electrical devices (load), and output a leakage signal (Sleak) when having detected the residual current. The sensor may be a zero sequence instrument transformer which can detect pulsating DC residual current and AC residual current.
The filter unit 2 is configured between the sensor and the leakage signal processing unit to filter high component, and only allow the component with leakage characteristics to pass through. Preferred, only the component with leakage current characteristics may pass through the filter. Optionally, a voltage protection module is set in the filter unit, which is configured to limit the voltage value of leakage signal outputted by the sensor unit in a preset range so that various electrical components of the whole current protection device would not be damaged by an instantaneous high signal. In a preferred embodiment, the voltage protection module may be constituted by a couple conversely parallel-connected diodes connected to the sensor unit in parallel. By mean of the protection module, the leakage indicator voltage can be limited in the range of turn-on voltage of the diode.
The first amplifier module 3 with bipolar amplifying factor is configured to amplify the leakage voltage signal Sieak and output the first amplified leakage signal SAMP-1 - The bipolar amplifying factor of the first amplifier module 3 means to proportionally amplify the signal based on the previous polarity whether the leakage indictor signal is positive or negative.
A leakage signal processing unit (4, 5) is configured to accumulate the leakage signal. The processing unit comprises two parts, one of which is an absolute value processing unit 4, configured to perform the absolute value calculation; the other of which is an integral processing unit 5 configured to perform time integral. The first amplified leakage signal SAMP-I is input into the absolute value processing unit 4, and the second amplified leakage signal SAMP-2 is output after performing the absolute value processing. Then the second amplified leakage signal SAMP-2 is input into the integral processing unit 5, and the third amplified leakage signal SAMP-3 is output after performing the integral.
After the integral, the third amplified leakage signal SAMP-3 is input into a comparison unit 7. The comparison unit is configured to compare the input third amplified leakage signal SAMP-3 with a preset threshold V T hreshoid- When the third amplified leakage signal is greater than the threshold V T hreshoid, the comparison unit determines that a leakage fault occurs in lines and outputs a shut-off indicator signal. When the third amplified leakage signal is less than the threshold V T hreshoid, the comparison unit determines that no leakage fault occurs in lines and does not output a shut-off indicator signal. Specifically the threshold V T hreshoid is obtained from a division on power voltage through a variable resistor, and the divided voltage can be changed by regulating the resistance value of the variable resistor so as to conveniently set the required threshold.
According to another preferred embodiment of the present invention, a delay unit 6 is arranged between the leakage signal processing unit (4, 5) and the comparison unit 7. The delay unit is configured to transmit the leakage signal after a certain delay cycles. The delay unit can be constructed in any suitable mode, such as a RC delay unit constituted by a low-temperature drifting and high precision resistor and capacitor. More details about the relay unit will be explained as below.
The shut-off indicator signal S con ti output from the comparison unit 7 is input into a circuitry operation component 8, which shuts off the connection between the electrical devices and their power supply through the switch of the circuit breaker to achieve the protection function after it receives a controlling signal. In an embodiment, the circuitry operation component may be a electromagnetic operation mechanism, while other suitable components can be utilized in the solution of the present invention. According to a preferred embodiment of the present invention, the sensor 1 may be a zero sequence instrument transformer which can detect both the pulsating DC residual current and AC residual current. Hence the zero sequence instrument transformer is suitable to simultaneously provide circuitry protection for such two kinds of leakage current. According to a preferred embodiment of the present invention, the amplifier unit and absolute value processing unit may be realized by using a bi-power operational amplifier. In which the integral processing unit 5 is constituted by the amplifier, resistor and capacitor, and the RC relay unit 6 is constituted by the resistor and capacitor.
Alternating Current
When people encounter an electric shock or the external shell of electrical device occurs the ground fault, the sensor 1 constituted by a zero sequence instrument transformer detects a unbalanced leakage current, and outputs a AC leakage signal Sieak- The leakage signal Sieak is transferred to the amplifier unit 3 via the filter 2.
The amplifier unit 3 comprises a bi-power operational amplifier, so the amplified signal SAMP-I amplified via the leakage signal Sieak may be a saturation level close to the power supply. The signal SAMP-I is input into the absolute value processing unit 4 after filtered by the capacitor in the amplifier unit. The absolute processing unit converts the negative value of the AC signal into a positive value, and no action will be taken on the positive value of the AC signal so that the signal input into the integral processing unit 5 is positive value or zero. The integral processing unit 5 performs the time integral of the signal, and outputs the signal SAMP-3- The signal after integral is input into the comparison unit 7, and compared with the preset threshold.
The threshold V T hreshoid internally set in the comparison unit 7 is a positive stable state detection threshold. If the leakage signal output by the integral unit is greater than the stable state threshold, the comparison unit determines that a leakage occurs in the line and outputs a high level leakage indication signal (for example, +5V); otherwise, no leakage occurs in the line and outputs a low level leakage indication signal (for example, -5V). The leakage indication signal output by the comparison unit 7 is input into the circuitry operation mechanism 8. After receiving the high level leakage indication signal, the circuitry operation mechanism 8 drives the switch of the MCB to shut off the connection between the electrical devices and power supply so as to avoid the occurrence of the leakage danger. Because the processing unit with the function of absolute value is adopted by the present invention, either positive or negative leakage signal may be used to trigger the circuitry operation mechanism to shut off the circuit connection. In a common circuitry protection device, two types of devices are involved, the delay protection device and an instantaneous protection, ie. the S type residual current protection and common type residual current protection device of national standard (GB). Once detecting the occurrence of line fault in circuitry, the common type protection device immediately breaks the power supply to guarantee the users and the safety of the electrical devices. The delay protection device has a feature of delay protection. After detecting the occurrence of the line fault, it does not function immediately but delay the signal to determine whether the protected line should be broken due to the occurrence of the fault. Such delay cycle is called non-driving time in national standard (GB). The national standard requires: even through a lager continuous leakage occurs, as long as the duration is not more than the non-driving time, the leakage device should not function. This delayed type of protection breaker may reduce unnecessary shutting-off, minimize the power shutting-off range and avoid the effect on the electrical devices due to frequent tripping. For example, as to the general switch of the multiple power lines, the power line will delay and wait for a moment instead of being shut-off immediately in response to detecting the occurrence of the leakage current in a power line. If the sub-switch of the failed line can be shut off normally, the general switch will not be shut off; if the sub-switch of the failed line can not be shut off as required, the general switch will be performed the shut-off operation.
In an embodiment of the present invention, the integral signal is input into the delay circuitry 6, and re-input into the comparison unit 7 to compare with the threshold after a certain delay. When the integral indication signal still exists after a preset delay period (eg 10ms), the delayed integral signal is input into the comparison unit.
Pulsating DC leakage current
The curve B in figure 1 illustrates the wave of the DC leakage signal. The DC leakage current signal looks like a series of positive or negative DC narrow pulses. Similar as the detecting procedure of AC leakage signal, sensor 1 detects the leakage signal, and output leakage indication signal Sieak- The leakage indication signal is input into the filter 2, filter the high component, and limit the voltage of the indication signal in the safe range by means of the voltage-limited component so as to guarantee the safety operation of the rear circuit parts.
The leakage indication signal respectively is input into the amplifier unit 3 and the leakage signal processing units (4, 5) in order to perform amplification, absolute value and integral calculation in turn. Subsequently, the processed leakage indication signal enters the comparison unit 7 configured to identify whether a leakage fault occurs.
In another embodiment, the integral leakage indication signal is firstly input into the delay unit 6, and then input into the comparison unit to identify whether a leakage fault occurs after certain cycles delay.
As to the pulsating DC leakage fault, each of narrow pulses does not last a long period, but due to more pulses are contained in the whole leakage lasting period, so the integral voltage will go up much higher after the integral procedure. When the value of the integral signal exceeds the preset threshold, the operation on the leakage issue will be triggered.
According to the present invention, the residual current protection device can not only detect and handle the AC and DC leakage fault simultaneously, but also resist the interference occurring in the lines. Generally speaking, the interference signal is caused by the unstable factors in lines, and includes less peak pulses or the ones with a shorter lasting time shown as the curve C in figure 1 .
In the existing structure of the current protection unit, the interference signal's peak is generally used to compare with the detecting threshold. If the interference signal's peak exceeds the threshold V T hreshoid, the circuit breaker will be mis-tripped. In the protected device provided in the present invention, due to the integral unit, the criterion to identify whether the leakage fault occurs has been replaced by the criterion to identify whether the integral value of the detecting signal exceeds the detecting threshold. Hence, even occurrence of higher peak voltage of the interference signal, as long as the higher peak voltage lasts a shorter period, the integral value after the integral will be less than the detecting threshold. Consequently, the protection device based on above design styles can effectively prevent the electromagnetic interference.
In an embodiment of the present invention, the integral timing constant of the signal integral unit 4 is obtained by configuring the parameters of the capacitors and resistors comprised by the integral unit. Likely the modification for the delay period of the delay unit can be performed and achieved by configuring the parameters of the capacitors and resistors. As to the different residual current integral period, the threshold can be modified by configuring the variable voltage-division resistor in the comparison unit.
In an embodiment of the present invention, various units such as the amplifier, the integral unit, the delay unit and the comparison unit are independent each other and have no effect among them, which make the residual protection device possess the good abilities on anti-interference and replacement. As described above, as long as the resistors and capacitors used in the delay unit are configured, the transient action protection unit or the delay action protection unit can be individually achieved in the same protection device.
In the functional units provided by the present invention, the operation amplifier is preferred to be used to perform the amplification, integral for absolute value etc. Due to the lower power consumption and good temperature characteristics of the operation amplifier, the residual current protection device presents the advantages comprising low power consumption, a wide temperature range of utilization, a wide voltage range, little periphery circuit, strong anti-interference ability and high reliability. Optimized, such protection device may be applied in various circuit breakers. It will be appreciated that the scope of the present invention is not limited by above embodiments, and the scope described by the claims shall prevail. Those skilled in the art should appreciate that those embodiments should by no means limit the scope of the present invention. Without departing from the spirit and concept of the present invention, any variations and modifications to the embodiments should be within the apprehension of those with ordinary knowledge and skills in the art, and therefore the scope of the present invention concludes all the variations similar to the solutions defined in the claims.