CN214314526U - Leakage protection device - Google Patents
Leakage protection device Download PDFInfo
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- CN214314526U CN214314526U CN202120358057.4U CN202120358057U CN214314526U CN 214314526 U CN214314526 U CN 214314526U CN 202120358057 U CN202120358057 U CN 202120358057U CN 214314526 U CN214314526 U CN 214314526U
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Abstract
The leakage protection device comprises a neutral point grounding wire of a transformer of a low-voltage power supply system, and is characterized by further comprising a switching-on/off unit and a control unit, wherein the switching-on/off unit is connected in series in the neutral point grounding wire, the control unit is used for collecting leakage current of the power supply system, and the control unit is connected with the switching-on/off unit and used for controlling the switching-on/off of the switching-on/off unit. The leakage protection circuit has the advantages that when leakage current exists, the neutral point grounding wire of the transformer is disconnected, the current loop of the leakage current is cut off, and the purpose of leakage protection is achieved.
Description
Technical Field
The utility model belongs to the earth leakage protection field among the low pressure power supply system, in particular to utilize and cut off the device that electric leakage protection was realized in electric leakage circuit.
Background
In a power supply system with a neutral point of a 10KV/0.4KV transformer grounded, the output mode of the transformer is three-phase four-wire or three-phase five-wire, and in any mode, when earth leakage exists at any position of a load and a transmission line of the power supply system, leakage current flows back to the neutral point of the transformer through the ground and a ground wire.
In a low-voltage power supply system, a distribution box is usually installed near a transformer, and a leakage protector is installed on a main incoming line or each outgoing line of the distribution box, so that when a line has leakage, the leakage protector is used for performing leakage protection by adopting a mode of disconnecting power supply (power failure) after detecting leakage current. However, in view of the current situation, the leakage protector in the distribution box basically cannot play a role, and the main reason is that frequent tripping can be caused if the preset breaking fixed value of the leakage protector is too small, the power failure area after tripping is large, and the power utilization of users is greatly influenced by frequent tripping and large-area power failure; if the preset breaking fixed value of the leakage protector is set to be overlarge, although the problem of frequent tripping can be solved, people with small leakage current can not be judged due to electric shock, and the electric shock protection effect cannot be achieved.
Disclosure of Invention
The utility model discloses according to the principle of the electric leakage of the power supply system of neutral point ground connection, a leakage protection device is provided for solve power supply system load side and transmission line's electric leakage problem.
The utility model provides a pair of leakage protection device, including the neutral point earth connection, divide-shut brake unit and the control unit of low pressure power supply system's transformer, divide-shut brake unit concatenates in the neutral point earth connection, and the control unit is used for gathering this power supply system's leakage current, and the control unit still has the relation of connection with the divide-shut brake unit simultaneously for switch on and break off of control divide-shut brake unit.
The auxiliary grounding wire is connected in parallel with the neutral point grounding wire, and the auxiliary grounding wire is connected with the auxiliary opening and closing unit and the resistor in series; the auxiliary opening and closing unit and the control unit have a connection relation, and the control unit controls the opening and closing of the auxiliary opening and closing unit.
Meanwhile, the control unit operates the switching-on and switching-off unit according to the following process:
step a 1: the control unit sets the initial state of the opening and closing unit to be a closed state, namely the neutral point of the transformer and the ground are in a conducting state;
step a 2: in a conducting state, the control unit collects leakage current of the power supply system;
step a 3: the control unit analyzes and judges the collected leakage current: when the leakage current reaches a preset breaking fixed value, the method enters a step a4, and if the leakage current does not reach the preset breaking fixed value, the method returns to the step a2 to continue to collect the leakage current of the power supply system;
step a 4: the control unit performs disconnection processing on the switch-on and switch-off unit, so that the neutral point of the transformer and the ground are in a disconnected state.
When the neutral point of the transformer is disconnected with the ground, the current loop of the leakage current is cut off, so that the leakage current cannot be generated by the leakage fault point in the power supply system, and the purpose of leakage protection is realized.
Further, the control unit operates the auxiliary opening and closing unit according to the following process:
step b 1: the control unit carries out time delay closing on the auxiliary opening and closing unit, namely, a neutral point of the transformer is conducted with the ground through an auxiliary grounding wire;
step b 2: the control unit acquires the total leakage current of the power supply system in the closed state of the auxiliary grounding wire;
step b 3: the control unit analyzes and judges the total leakage current of the auxiliary grounding wire in a closed state: when the total leakage current of the auxiliary grounding wire in the closed state reaches a preset closing fixed value, the step b4 is entered, and if the total leakage current does not reach the preset closing fixed value, the step b2 is returned to continue to collect the total leakage current of the power supply system;
step b 4: the control unit carries out closing processing on the shunt closing unit, so that the neutral point grounding wire is in a conducting state, namely the neutral point of the transformer is conducted with the ground through the neutral point grounding wire;
step b 5: and after the switching-on and switching-off unit is closed, the control unit performs switching-off processing on the auxiliary switching-on and switching-off unit.
When the power supply system has leakage current and reaches a preset breaking fixed value, the opening and closing unit is subjected to breaking treatment, so that a current loop of the leakage current is cut off. It should be understood that the current is rather than the voltage, which causes the electric shock injury to the human body, so if the ground fault is the electric shock of the person, the current loop is cut off, the person cannot be injured, and the purpose of electric shock protection is achieved.
The utility model has the advantages that,
when leakage current exists, the neutral point grounding wire of the transformer is disconnected, the current loop of the leakage current is cut off, and the purpose of leakage protection is achieved.
Drawings
Fig. 1 shows an implementation principle of the earth leakage protection device (initial state).
Fig. 2 shows the implementation principle of the earth leakage protection device (protection after-start state).
Fig. 3 is a schematic diagram of the process for controlling the disconnection of the neutral point ground wire according to the present invention.
FIG. 4: the utility model discloses a closed flow schematic diagram of control neutral point earth connection.
Description of the figures
1. The device comprises a transformer, a switching-on and switching-off unit 2, a control unit 3, an auxiliary switching-on and switching-off unit 4, a resistor 5, a resistor 6, an isolating switch 7 and a protection element.
Detailed Description
Referring to fig. 1, the utility model provides a pair of leakage protection device, including transformer 1 of low pressure power supply system and the neutral point earth connection PE1 of transformer, divide-shut brake unit 2 and the control unit 3, divide-shut brake unit 2 concatenates in neutral point earth connection PE1, and the control unit 3 is used for gathering this power supply system's leakage current I delta n, still has the relation of connection with divide-shut brake unit 2 simultaneously for control switch on and break off of divide-shut brake unit 2.
The opening and closing unit 2 may be a circuit breaker with opening and closing functions, or a combination of parts in the circuit breaker, such as a combination of a contact system, a tripping driving device, and a closing driving device in the circuit breaker, or may be a relay or an electronic switch; and can use mature technical scheme to realize the function of combination.
The utility model provides an among the technical scheme, utilize current transformer to gather power supply system's leakage current, and we know and gather the leakage current with current transformer, it is the application most extensive, the most mature scheme, preferably, install current transformer CT1 on neutral point grounding PE1, current transformer CT 1's output is connected with the control unit 3, make the control unit 3 can gather the electric current that flows through on neutral point grounding PE1, this electric current is power supply system's total leakage current.
Optionally, the current transformer CT5 is installed at the output end of the transformer, that is, the output phase line A, B, C and the neutral line N of the transformer simultaneously pass through the current transformer CT5, and the output end of the current transformer CT5 is connected to the control unit 3, so that the control unit 3 can collect the leakage current at the output end of the transformer, which is the total leakage current of the power supply system.
Optionally, the current transformer is installed on the output branch to collect the branch leakage current, in the technical scheme, 3 branches are taken as an example for description, and the current transformer CT2 is installed on the first branch, that is, the phase line A, B, C and the zero line N of the first branch simultaneously pass through the current transformer CT 2; the current transformer CT3 is installed on the second branch, that is, the phase line A, B, C and the neutral line N of the second branch simultaneously pass through the current transformer CT 3; the current transformer CT4 is mounted on the third branch, i.e., the phase line A, B, C and the neutral line N of the third branch simultaneously pass through the current transformer CT 4.
When there is leakage in the load side and the transmission line of the power supply system, as illustrated in fig. 1, when a of the third branch has a ground fault with respect to ground, a leakage current I Δ n is generated, which flows back to the neutral point O of the transformer via the ground (dashed connection in fig. 1) and the neutral grounding line PE 1.
At this time, the control unit 3 can acquire the leakage current I Δ n through the current transformers CT1, CT4, and CT5, and the values are all the same, and it is conceivable that if the leakage current exists in the second branch, the control unit 3 can acquire the same leakage current through the current transformers CT1, CT3, and CT 5. Therefore, in the scheme of collecting the leakage current, the current on the neutral point grounding wire PE1, the leakage current at the output end of the transformer and the leakage current of the collecting branch are collected, and these three schemes are equivalent, and any one scheme, or any combination of two schemes, or any combination of three schemes may be selected.
No matter which leakage current collection scheme is selected, when the leakage current collected by the control unit 3 reaches a preset breaking fixed value, the opening and closing unit 2 is disconnected, and a current loop of the leakage current is cut off. Because of the basic knowledge of the circuit, there is only voltage and no current when the circuit is opened, and therefore, the leakage current disappears after the neutral point grounding wire PE1 is opened. It should be understood that the current is rather than the voltage, which causes the electric shock injury to the human body, so if the ground fault is the electric shock of the person, the current loop is cut off, the person cannot be injured, and the purpose of electric shock protection is achieved.
Similarly, it can be seen that after the leakage current loop is cut off, the output of the transformer is not cut off, and therefore, the load connected to the output end of the transformer can still work normally, and therefore, the power failure of a user can not be caused while the leakage current protection is realized.
Furthermore, an auxiliary grounding wire PE2 is connected to the neutral grounding wire PE1 in parallel, and an auxiliary opening and closing unit 4 and a resistor 5 are connected in series to the auxiliary grounding wire PE 2; the auxiliary opening and closing unit 4 and the control unit 3 have a connection relation, and the control unit 3 controls the opening and closing of the auxiliary opening and closing unit 4.
Referring to fig. 2, after the control unit 3 performs the opening process on the switching unit 2 on the neutral grounding line PE1, the control unit 3 controls the auxiliary switching unit 4 to close (its initial state is open), and at this time, it can be considered that the leakage current leakage loop is turned on again, and a leakage current I Δ n1 is regenerated, but there is a difference from the leakage loop when the neutral grounding line PE1 is turned on, because the resistor 5 is connected in series in the auxiliary grounding line PE2, the generated leakage current I Δ n1 is smaller than the leakage current I Δ n when the neutral grounding line PE1 is turned on; if we select the resistance of the resistor 5 in the auxiliary ground line PE2 to be 20K Ω, the original leakage current I Δ n is the leakage current caused by the electric shock of the human being, and the leakage current can be calculated as follows:
i Δ n =220V/2000 Ω (resistance of human body) = 0.11A.
The leakage current after the auxiliary ground line PE2 is turned on may be calculated as follows:
i Δ n1= 220V/(2000 Ω +20000 Ω) =0.01A, which indicates that the leakage current still exists, and the leakage current collection is continued and maintained in this state; it is known that a current of 0.01A does not cause any harm to the human body.
Further, a protection grounding wire PE3 is provided between the transformer neutral point O and the ground, and an overvoltage protection element 7, such as a surge protector, a lightning arrester, a varistor or a gas discharge tube, is connected in series with the protection grounding wire PE 3. When the neutral point grounding wire PE1 is disconnected, the neutral point grounding wire PE1 can be used as a discharge channel of overvoltage when the power supply system is struck by lightning or other surge impact, so that the safety and the reliability of the power supply system are protected.
Further, a disconnecting switch 6 is also connected in series in the neutral point grounding wire PE 1. The purpose of this setting is that if when carrying out the uninterrupted operation to power supply system, to break neutral point earth connection PE1, just can very convenient break off, simultaneously, also be an obvious, visual breakpoint, the live working that lets the operating personnel more reassure.
Further, the control unit 3 further comprises a zero ground resistance measuring circuit, the measuring circuit mainly comprises a control switch and a power supply, the zero ground resistance measuring circuit is connected between the neutral point O of the transformer and the ground, after the switching-on/off unit 2 is switched off, a measuring voltage is applied between the neutral point O of the transformer and the ground by using the power supply, then the current flowing back to the power supply is collected, and the grounding resistance between the zero line at the output end of the transformer and the ground can be calculated, so that whether grounding fault exists on the zero line is judged, when the current flowing back to the power supply is zero, it indicates that no grounding exists between the zero line and the ground, and if the current exists, it indicates that grounding exists.
Conceivably, if set up a communication unit again in the control unit 3, just can communicate fault information and corresponding equipment, inform maintenance or relevant managers with fault information, of course, the communication unit who sets up can also be with above-mentioned the utility model discloses any other data and relevant equipment carry out the communication in the technical scheme.
Referring to fig. 3, the utility model provides a pair of earth leakage protection device's control process as follows:
step a 1: the control unit 3 sets the initial state of the opening and closing unit 2 to be a closed state, namely, the neutral point O of the transformer is in a conducting state with the ground;
step a 2: in a conducting state, the control unit collects leakage current of the power supply system;
step a 3: the control unit 3 analyzes and judges the collected leakage current: when the leakage current reaches a preset breaking fixed value, the method enters a step a4, and if the leakage current does not reach the preset breaking fixed value, the method returns to the step a2 to continue to collect the leakage current of the power supply system;
step a 4: the control unit 3 performs disconnection processing on the switching-on/off unit 2 so that the neutral point O of the transformer is disconnected from the ground.
Further, after the neutral point grounding wire is disconnected, the control process is as follows:
step b 1: the control unit 3 carries out time delay closing on the auxiliary opening and closing unit 4, namely, a neutral point of the transformer is conducted with the ground through an auxiliary grounding wire;
step b 2: the control unit 3 collects the total leakage current of the power supply system in the closed state of the auxiliary grounding wire;
step b 3: the control unit 3 analyzes and judges the total leakage current of the auxiliary grounding wire in a closed state: when the total leakage current of the auxiliary grounding wire in the closed state reaches a preset closing fixed value, the step b4 is entered, and if the total leakage current does not reach the preset closing fixed value, the step b2 is returned to continue to collect the total leakage current of the power supply system;
step b 4: the control unit 3 carries out closing processing on the shunt and close unit 2, so that the neutral point grounding wire is in a conducting state, namely the neutral point of the transformer is conducted with the ground through the neutral point grounding wire;
step b 5: after the switching-on/off unit 2 is closed, the control unit 3 performs switching-off processing on the auxiliary switching-on/off unit 4.
In order to better understand the utility model, assuming that the preset breaking constant value is set to 30mA, when the neutral point grounding wire is conducted, the power supply system generates a human body electric shock leakage current, we can roughly estimate the leakage current I Δ n =220V/2000 Ω (human body resistance) =0.11A at the moment, collect the value of the leakage current, which exceeds the preset breaking constant value 30mA, at the moment, break the neutral point grounding wire, and close the auxiliary grounding wire after breaking, assuming that the resistance value of the resistance R in the auxiliary grounding wire is 20K Ω, after the auxiliary grounding wire is conducted, if the leakage current of the power supply system still exists, at the moment, the leakage current I Δ n1= 220V/(2000 Ω +20000 Ω) =0.01A, then it is determined that the switch-on cannot be performed, then the collection is continued, if the collected leakage current I Δ n1 is zero, then the control unit can control the switch-on and switch-off unit to be closed, and then the auxiliary opening and closing unit is disconnected, and the initial state recovery is completed.
Finally, it should be noted that the above-disclosed embodiments of the present invention are only provided to help illustrate the present invention. The preferred embodiments are not exhaustive and do not limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best understand the invention for and utilize the invention. It is obvious that all other embodiments obtained by a person skilled in the art without making creative efforts belong to the protection scope of the present invention.
Claims (9)
1. The leakage protection device comprises a neutral point grounding wire of a transformer of a low-voltage power supply system, and is characterized by further comprising a switching-on/off unit and a control unit, wherein the switching-on/off unit is connected in series in the neutral point grounding wire, the control unit is used for collecting leakage current of the power supply system, and the control unit is also connected with the switching-on/off unit and used for controlling the switching-on/off of the switching-on/off unit.
2. A leakage protection device according to claim 1, wherein said control unit collects leakage current of the power supply system by using a current transformer, said current transformer being installed in: the neutral point earth wire, or the output end of the transformer, or the branch circuit of the power supply system.
3. A leakage protection device according to claim 1, further comprising an auxiliary ground line connected in parallel to the neutral ground line, wherein the auxiliary ground line is connected in series with an auxiliary switching unit and a resistor; the auxiliary opening and closing unit and the control unit are in a connection relation, and the control unit controls the opening and closing of the auxiliary opening and closing unit.
4. A leakage protection device according to claim 1, further comprising a ground protection line connected in parallel to the neutral ground, wherein the ground protection line is connected in series with an overvoltage protection device.
5. A leakage protection device according to claim 4, wherein said overvoltage protection element is any one or any combination of a surge protector, an arrester, a varistor or a gas discharge tube.
6. The earth leakage protection device of claim 1, further comprising a zero-ground resistance measuring circuit, wherein the zero-ground resistance measuring circuit is connected in parallel to the neutral point earth, and after the switching unit is turned off, a measuring voltage is applied between the neutral point of the transformer and the ground to measure the ground resistance between the zero line and the ground at the output end of the transformer, thereby determining whether the zero line has a ground fault.
7. A residual current device as claimed in claim 1, characterized in that a disconnecting switch is connected in series with the neutral grounding.
8. An electric leakage protection device according to claim 1, wherein the switching unit is a circuit breaker with breaking and closing functions, or a combination of parts and components inside the circuit breaker, or one or any combination of a relay or an electronic switch; the combination of partial components in the circuit breaker at least comprises a contact system, a tripping driving device and a closing driving device of the circuit breaker.
9. A leakage protection device according to claim 1, further comprising a communication unit, the communication unit being connected to the control unit for interacting data with the corresponding device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120358057.4U CN214314526U (en) | 2021-02-09 | 2021-02-09 | Leakage protection device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120358057.4U CN214314526U (en) | 2021-02-09 | 2021-02-09 | Leakage protection device |
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| Publication Number | Publication Date |
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| CN214314526U true CN214314526U (en) | 2021-09-28 |
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| CN202120358057.4U Active CN214314526U (en) | 2021-02-09 | 2021-02-09 | Leakage protection device |
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- 2021-02-09 CN CN202120358057.4U patent/CN214314526U/en active Active
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