Pair of electrical connectors and method for determining a connection status of the pair of electrical connectors

Abstract

A pair of electrical connectors 20 having a first and second housing portions 22, 24, wherein at least a first and a second electrical contact pin element 21a, b is provided in the first housing porti

Description

Field of the invention The invention concerns a pair of electrical connectors having a first housing portion and a second housing portion which can be connected to the first housing portion for establishing an electrical connection as well as a method for determining a connection status of the pair of electrical connectors. Background Undesired or unintended electric arcing can have detrimental effects on electric power transmission, distribution systems and electronic equipment. Devices which may cause arcing include switches, circuit breakers, relay contacts and DC connectors. When an inductive circuit is switched off, the current cannot instantaneously jump to zero: a transient arc will be formed across the separating contacts. If a circuit has enough current and voltage to sustain an arc formed outside of a switching device, the arc can cause damage to equipment such as melting of conductors, destruction of insulation, and fire. An arc flash describes an explosive electrical event that presents a hazard to people and equipment. In particular DC connectors when disconnected under load can produce a dangerous electric arc. Active DC connectors for so-called hot-plug applications are usually equipped with a semiconductor switch connected in parallel and directly built into the connector, actively quenching the electric arc. However, determination of a connection status of the pair of electrical connectors with active arc quenching has to be known to enable a safe and reliable function of the active arc quenching. Known connectors have a complex design and generate high production costs. Such DC connectors are larger than conventional connectors without active arc quenching and therefore impose special requirements with regard to installation space. Active DC connectors also require more maintenance. Against this background, the problem to be solved by the invention is to further develop a pair of electrical connectors for improved determination of the connection status during coupling and decoupling to ensure reliable extinguishing of a lightning arc by having minimum manufacturing complexity in the pair of electrical connectors. Summary The problem is solved by a pair of electrical connectors according to claim 1 and a method for determining a connection status of the pair of electrical connectors according to claim 15. Preferred embodiments of the invention are subject of the dependent claims. The problem is solved in particular by an pair of electrical connectors having a first housing portion and a second housing portion which can be connected to the first housing portion, wherein at least a first and a second electrical contact element is provided in the first housing portion for connection to a respective first and a second plug-in receptacle provided in the second housing portion for establishing an electrically conductive connection between a load side and an voltage source side, wherein a detection means for detecting a signal indicative for a connection status of the pair of electrical connectors is provided, with the detection means being connected to a control unit for analysing the indicative signal received from the detection means and to, depending on the connection status of the pair of electrical connectors, activating or deactivating a switching device to control an electrical current during coupling and decoupling of the pair of electrical connectors. This configuration allows for a simple and efficient determination of the connection status and the control of the switching device to control or shortcut a voltage supply during coupling and decoupling of the pair of electrical connectors based on the indicative signal to avoid formation of a lightning arc during either of coupling and decoupling of the pair of electrical connectors. In some embodiments a first power supply unit for powering the detection means, the control unit and the switching device is provided in the first or second housing portion. This allows the respective units to be operated independently of or decoupled from the main power source. In some embodiments the detection means are positioned on an extension provided in the first portion of the housing and a recess for inserting the extension in the second portion of the housing. This allows for a compact configuration and stable guidance of the detection means within the pair of electrical connectors thus avoiding misalignment and malfunction of the detection means. In some embodiments the detection means comprise optical means, wherein the optical means have at least one light source and at least one photosensor for a detection of a light signal emitted by the light source. This allows for the provision of a stable and well detectable signal independent of external influences and environmental conditions. In some embodiments the optical means are arranged on the extension and / or in the recess and the signal indicative for a connection status of the pair of electrical connectors is derived from one of the detection of the light signal by the at least one photosensor or an interruption of the detection of the light signal by the at least one photosensor. This allows for efficient signal emission and detection during coupling and decoupling of the pair of electrical connectors and avoids misalignment and malfunction of the detection means. In some embodiments the light source and the at least one photosensor are arranged in the recess with the extension having guiding means for guiding the light signal from the light source to the at least one photosensor or with the extension being designed to interrupt the light signal. This allows for a compact implementation of the detection means with in the pair of electrical connectors thus reducing manufacturing efforts and costs. In some embodiments the guiding means are designed as optical conductors, in particular as a fibre optic light guide or a reflective means, in particular a mirror. The invention advantages are thereby achieved when light is guided by means of the guiding means to a photodetector and adaption of the emitted light signal as well as the detection is enabled depending on the configuration of the pair of electrical connectors as well as of the nature of intended signal to be detected. In some embodiments the detection means is configured as a mechanical detection means, in particular a push-button or a switch wherein the detection means is arranged in the recess and the extension is designed to actuate the push-button or switch, wherein a signal indicative for a connection status of the plug connector is derived from the detection of a switch or push-button actuation. This allows for a configuration of the pair of electrical connectors and the detection means with low complexity thus reducing the manufacturing efforts and costs by nevertheless ensuring stable and reliable function. In some embodiments a second power supply unit is provided in the housing to supply power to the light source. This provides the advantages that a second independent power supply is provided for a light source thus increasing the adaptability of the pair of electrical connectors to various requirements and configurations. In some embodiments the switching device is arranged in parallel or in series with a voltage source. This allows for adaption of the detection and switching means to various use cases and the respective configuration of the elements provided in the pair of electrical connectors. In some embodiments the switching device is configured as a semiconductor switch, wherein the semiconductor switch comprises in some embodiments a MOSFET and a relay in parallel connection or a MOSFET and a resistor in series connection. This allows for the adaption of the pair of electrical connectors and provides various options for stable and efficient quenching or avoidance of lightning arc formation while coupling or decoupling the pair of electrical connectors. In some embodiments a voltage limiting device is provided in at least one portion of the housing. This allows for ana adaption of the pair of electrical connectors to the type of load. The voltage limiting device provided in the pair of electrical connectors can be configured in particular as a Z-diode with series resistor. This prevents the occurrence of a high voltage at the contact elements of the electrical contact elements, particularly with inductive loads. In some embodiments the first or the second portion of the housing is connected to the voltage source. This allows for adaption of the pair of electrical connectors depending on position with respect to the load and voltage source side. In order to make the pair of electrical connectors compatible in both directions, in a particular embodiment a two-part configuration of the electrical contact elements is provided with a power supply unit being connected to a first section of the contact element to ensure powering the detection means and providing full functionality as outlined above. The invention further provides a method for determining a connection status of the pair of electrical connectors, comprising the steps of: Contacting at least one of the electrical contact elements provided in the first portion of the housing with the corresponding plug-in receptacles provided in the second portion of the housing, emitting a signal indicative for the connection status of the pair of electrical connectors during positioning of the electrical contact elements, analysing the signal by the control unit, emitting a control signal by the control unit to control switching of a switching device for one of establishing or interrupting a voltage supply depending on the connection status of the pair of electrical connectors. In some embodiments of the method the switching device establishes a shortcut depending on the connection status of the pair of electrical connectors thereby quenching a light arc formation during coupling or decoupling of the pair of electrical connectors. This allows for a safe operation of the pair of electrical connectors during coupling and decoupling and eliminates the risk of damage to equipment such as melting of conductors, destruction of insulation, and fire. In some embodiments of the method the switching device is configured as hybrid switch comprising a MOSFET and a relay in parallel connection, wherein the control unit emits a control signal to the hybrid switch to switch on when a completed coupling of the pair of electrical connectors is detected and to switch off when a decoupling of the pair of electrical connectors is detected. This allows for adaption of the configuration of the pair of electrical connectors to various use cases and requirements set out thereby. In some embodiments of the method the switching device is configured as hybrid switch comprising a MOSFET and a resistor in series connection, wherein the control unit emits a control signal to the hybrid switch to switch on when a signal for decoupling of the pair of electrical connectors is detected and to switch off when a signal for the complete coupling of the pair of electrical connectors is detected by the control unit. This allows for adaption of the configuration of the pair of electrical connectors to particular use cases and requirements set out thereby. In some embodiments of the method the signal indicative for a connection status of the pair of electrical connectors is a mechanically or optically induced signal. This allows for an adaptation of the configuration of the pair of electrical connectors depending on the complexity and requirements defined by the intended operation and operational environment. Brief description of the drawings Examples of embodiments of the invention are shown in the drawings and are explained in more detail below. It shows: Fig. 1 a schematic view of a pair of electrical connectors according to an embodiment of the present invention; Fig. 2a, b schematic views of a pair of electrical connectors according to another embodiment of the present invention; Fig. 3a, b schematic views of a pair of electrical connectors according to another embodiment of the present invention; Fig. 4a - c schematic views of a pair of electrical connectors according to another embodiment of the present invention; and Fig. 5 a schematic view of a pair of electrical connectors according to another embodiment of the present invention. The figures contain partially simplified, schematic representations. In some cases, identical reference numerals are used for identical, but possibly not identical, elements. Different views of the same elements may be scaled differently. Directional indications such as "left", "right", "top" and "bottom" are to be understood with reference to the respective figure and may vary in the individual representations with respect to the object shown. Detailed description of embodiments Fig. 1 shows a schematic view of a pair of electrical connectors 20 according to an embodiment of the present invention. The pair of electrical connectors 20 is shown in the uncoupled state. The pair of electrical connectors 20 comprises a first housing portion 22 with electrical contact elements 21a, b being provided as contact pins and a second housing portion 24 connectable to the first housing portion 22. To establish an electric connection the electrical contact elements 21a, b are inserted into the plug-in receptables 23a, b provided in the second housing portion 24. The electrical contact elements 21a, b project from the first housing portion 22 towards the second housing portion 24. The electrical contact elements 21a, b are connected to a load 25, whereas the plug-in receptables 23a, b are connected to a voltage source 26. Within the second portion, a first power supply unit 27 and a control unit 28 is provided, wherein the first power supply unit 27 is connected to the voltage source 26 and configured to power the control unit 28 in the uncoupled state of the pair of electrical connectors 20. The control unit 28 is configured to analyse the connection status of the pair of electrical connectors 20 and to control an electrical current during coupling and decoupling of the pair of electrical connectors 20 depending on the connection status of the pair of electrical connectors 20. The first housing portion 22 comprises a central extension 29 protruding from the first housing portion 22 while in the second housing portion 24 a recess 30 is provided for inserting the extension 29 during coupling. In the embodiment of Fig. 1, the detections means are configured as a push-button 31 provided at an end face 32 of the recess 30 provided in the second housing portion 24. The control unit 28 is in contact with the pushbutton 31 for detecting the end position of the extension 29 when inserted into the recess 30 during coupling. The switching status of the push-button 31 is evaluated by the control unit 28. As soon as the extension 29 touches the push-button 31 during coupling the pair of electrical connectors 20, the control unit 28 receives the indicative signal that the coupled state has been reached. The extension 29 or the push-button 31 are arranged in such a way that the electrical contact elements 21a, b are in contact with the plug-in receptables 23a, b before the push-button 31 is pressed. If during decoupling or unplugging of the pair of electrical connectors 20 the extension 29 at some point no longer touches the push-button 31 the control unit 28 receives the indicative signal that the coupled or plugged-in state has been exited. The extension 29 is arranged in such a way that the electrical contact elements 21a, b remain in contact with the plug-in receptables 23a, b for a certain distance after the push-button is not touched thereby avoiding formation of a lightning arc within the pair of electrical connectors 20 during decoupling or unplugging. Fig. 2a and Fig. 2b show pairs of electrical connectors 20 according to other embodiments of the invention. The elements described in connection with Fig. 1 are not described anew and reference is made to the embodiment described above. In the embodiment of Fig. 2a detection means are provided that comprise a light source 33 configured as a LED positioned in the extension 29 of the first housing portion 22 and a corresponding photosensor 34 provided in the recess 30 of the second housing portion 24. In this embodiment a second power supply unit 35 is provided to power the light source 33 during coupling. Power is supplied to the light source 33 as soon as the electrical contact elements 21a, b of the first housing portion 22 contact the plug-in receptables 23a, b of the second housing portion and a light signal is emitted during further insertion of the extension 29 in the course of coupling. In this embodiment the first power supply unit 27 in the second housing portion 24 supplies the control unit 28 as well as the photosensor 34 with power. The control unit 28 interacts with the photosensor 34 and analyses its signal. As soon as the electrical contact elements 21a, b of the first housing portion 22 come into contact with the plug-in receptables 23a, b of the second housing portion 24, the light source 33 is supplied with power via the second power supply unit 35 and emits a light signal light. As soon as the light source 33 is aligned with the photosensor 34, the control unit 28 analyses the signal and derives that the pair of electrical connectors 20 is in the fully coupled or plugged-in state. The photosensor 34, the light source 33 and the electrical contact elements 21a, b are positioned accordingly to enable this functionality. Upon decoupling the pair of electrical connectors 20 the light source 33 is no longer aligned with the photosensor 34 and indicates that the coupled state is exited. However, the light source 33 continues to be supplied with power until the electrical contacts 21a, b are no longer in contact with the plug-in receptables 23a, b. In the embodiment of Fig. 2b the light source 33 and the photosensor 34 are both positioned in the second housing portion 24 adjacent to the recess 30. The first power supply unit 27 therein supplies the control unit 28, the light source 33 and also the photosensor 34 with power. The control unit 28 interacts with the photosensor 34 and analyses its signal. In this embodiment the extension 33 of the first housing portion 22 acts as a light barrier. When the extension 29 is fully inserted into the recess 30 the photosensor 34 receives no signal from the light source 33 as the signal is blocked by the extension 29. The control unit 28 hence derives the signal that the fully inserted or coupled state of the pair of electrical connectors 20 is reached. The electrical contact elements 21a, b in the first housing portion 22 are in contact with the plug-in receptables 23a, b of the second housing portion 24 for a certain distance, regardless of whether the plug connector is fully coupled. Fig. 3a and Fig. 3b show pairs of electrical connectors 20 according to other embodiments of the invention. The elements described in connection with the previous figures are not described anew and reference is made to the embodiment described above. Fig. 3a depicts an embodiment with a reflective element 36 arranged in the extension 29 of the first housing portion 22. During coupling of the pair of electrical connectors 20 the reflective element 36, configured e.g. as a mirror but without limiting the invention thereto, is brought in a position to reflect light emitted by the light source 33 towards the photosensor 34. Once the light signal is received by the photosensor 34 the control unit 28 analyses the signal and derives that the pair of electrical connectors 20 is in the fully coupled state. When decoupling the pair of electrical connectors 20 the light signal is no longer reflected to the photosensor 34 by the reflective element 36 and hence indicates that the pair of electrical connectors is decoupled. The reflective element 36 can also be configured as a prism. Due to the configuration and position of the reflective element 36 and the contact elements 21a, b electrical contact already exists before the fully coupled state is detected. The signal received by the control unit 28 thus indicates that the fully coupled state is about to be reached or exited. Fig. 3b depicts a further option of the embodiment of Fig. 3a with the difference that two photosensors 34'and 34” are provided in the recess 30 to allow for detection of an intermediate position of the extension 29 in the recess 30. The electrical contact elements 21a, b thereby can be arranged so that an electrical contact is established before the first photosensor 34' emits a signal. The signal that the pair of electrical connectors 20 is in the fully coupled state is received once the first photosensor 34'receives a light signal whereas the second photosensor 34” always receives a light signal only as long as the pair of electrical connectors 20 is fully coupled. Fig. 4a to c schematically depict views of pair of electrical connectors 20 according to further embodiments of the present invention. Elements described in connection with the previous figures are not described anew and reference is made to the embodiment described above. In the embodiment of Fig. 4a a fibre optic arrangement is provided in the extension 29 having a first fibre path 37a and a second fibre path 37b. The light source 33 and the respective photosensors 34', 34” are positioned in the recess 30. During coupling the first photosensor 34' receives the light signal emitted by the light source 33, as the first fibre path 37a forwards the light signal. Once the electrical contact elements 21a, b are fully inserted into the plug-in receptables 23a, b, the second photosensor 34” receives the light signal emitted by the light source 33 and transmitted by the second fibre path 37b to the second photosensor 34”. The control unit 28 analysing the signals received from the photosensors 34'and 34” can hence determines the connection status and detects when the pair of electrical connectors 20 is in the fully coupled state. When uncoupling the pair of electrical connectors 20 the control unit 28 at some point will no longer receive a signal from the second photosensors 34” and detect, that the pair of electrical connectors 20 has left the fully coupled state. If the first photosensor 34' receives a light signal, it can be derived that the pair of electrical connectors 20 is nearly fully decoupled hence allowing for an improved tracking of the connection status i.e. also of a half-coupled state. The electrical contact elements 21a, b can be arranged so that an electrical contact is established before the first photosensor 34' emits a signal or that the electrical contact is only established after the first photosensor 34' receives a light signal. The second photosensor 34” always receives a light signal when the pair of electrical connectors 20 is fully coupled. Fig. 4b schematically depicts a further embodiment of the pair of electrical connectors 20 having the elements of the embodiment of Fig.4a. In addition there to, a first switching device 38a is provided in the second housing portion 24 that is controlled by the control unit 38 and a voltage limiting device 39 comprising a Z-diode 40 and a resistor 41, is provided in the first housing portion 22. Depending on the type of load 25, it may be necessary to provide such a voltage limiting device 39 in the first housing portion 22. This voltage limiting device 39 prevents the occurrence of a high voltage at the contact elements 21a, b, particularly, but not limiting with inductive loads 25. The first switching device 38a is provided in the second housing portion 24 and arranged in series with the voltage source 26. In this embodiment the first switching device 38a is configured as a hybrid switch comprising a MOSFET and a relay in parallel connection, but without limiting the invention thereto. The first switching device 38a is switched on by first switching the MOSFET and then the relay with a slight time delay when the pair of electrical connectors 20 is fully coupled, and switched off by first switching the relay and then the MOSFET with a time delay when the pair of electrical connectors 20 is decoupled. During operation, the entire current can be conducted via the relay and the MOSFET is de-energized. This arrangement can prevent arcing both when switching on and when switching off, i.e. during coupling and decoupling of the pair of electrical connectors 20. The first switching device 38a is controlled by the control unit 28 based upon analysis of the signals received from the detection means configured as described in connection with Fig. 4a. The electrical contact elements 21a, b are arranged so that contact is made before the first photosensor 34' receives a light signal. When coupled, as soon as the first photosensor 34' receives a light signal and transmits a status signal to the control unit 28 the first switching device 38a is operated. The control unit 28 upon receiving this signal switches on the MOSFET of the first switching device 38a. If the electrical contact elements 21 a, b are inserted further and once the second photosensor 34” receives a light signal, the relay in the first switching device 38a is switched on and the MOSFET is switched to the nonswitching state shortly afterwards thus bringing the pair of electrical connectors 20 into a conductive condition. When decoupling, as soon as the second photosensor 34” does not receive a light signal, the control unit 28 switches on the MOSFET of the first switching device 38a. When decoupling continues the first photosensor 34' receives a light signal that triggers switching-off of the relay of the first switching device 38a. If the first photosensor 34' does not longer receive a light signal either, the MOSFET is switched to the non-conductive state. In the embodiment of Fig. 4c the control unit 28 controls a second switching device 38b connected in parallel to the voltage source 26. The second switching device 38b is therein configured as a semiconductor switch comprising e.g. a MOSFET in series with a resistor, but without limiting the invention thereto. This arrangement can prevent arcing both when coupling and decoupling the pair of electrical connectors 20. The electrical contact elements 21a, b are arranged so that there is no contact before the first photosensor 34' receives a light signal. When coupling, as soon as the first photosensor 34' receives a light signal, the control unit switches on the second switching device 38b bringing it into a conductive state. If the electrical contact elements 21a, b are further inserted, the electrical contact elements 21a, b contact the plug-in receptables 23a, b and the second photosensor 34” receives a light signal so that the control unit 28 brings the second switching device 38b into a non-conductive state after analysing the respective signals. When decoupling, as soon as second photosensor 34” does not receive a light signal, the control unit 28 switches on the second switching device 38b after analysing the respective signals. If the electrical contact elements 21a, b are led out further, the electrical contact elements 21a, b lose contact with the plug-in receptables 23a, b and the first photosensor 34' receives a light signal, so that the second switching device 38b is brought into a non-conductive state again. This arrangement can prevent arcing both when switching on and when switching off, i.e. during coupling and decoupling of the pair of electrical connectors 20. In conjunction with the parallel connected second switching device 38b, the detection of a connection status as outlined above only indicates the presence or absence of the end position, i.e. the fully coupled state of the pair of electrical connectors 20. In consequence of this a lightning arc occurring when decoupling could not be fully prevented since in particular when decoupling with a slow pulling motion, the second switching device 38b would have to remain switched on for a certain amount of time, while it is not certain whether the electrical contact elements 21a, b have already fully lost contact. To circumvent this a current measuring device (not shown) can be provided that detects or measures a current flow at the contact elements 21a, b or plug-in receptables 23a, b and issues a signal to the control unit to leave the second switching device 38b switched on or to switch it on if current is still flowing. Fig. 5 depicts a schematic view of a pair of electrical connectors 20 according to another embodiment of the present invention. Elements described in connection with the previous figures are not described anew and reference is made to the embodiment described above. While in the previous embodiments the load 25 was assigned to the first housing portion 22 and the voltage source 26 to the second housing portion 22 of the pair of electrical connectors 20 the embodiment of Fig. 5 depicts a configuration that allows making the pair of electrical connectors 20 compatible in both directions. Therefore, one of the plug in receptables 23a, b has a two-part configuration having a first section 23a' and a second section 23a”, wherein the power supply unit 27 is connected to the first section 23a'. The embodiment can be provided with a first or a second switching device 28a, b connected either in series or in parallel. The sequence of switching operations differs depending on the position of the load 25 or the voltage source 26 and depending on the signals received from the photosensors 34'and 34” during coupling and decoupling of the pair of electrical connectors 20. Apart from the before described embodiment other embodiments not covered by the present invention are possible: Providing a switching device 38a, b configured as a relay and / or a MOSFET that is open in non-operating state. With contacting one of the electrical contact elements 21a, b and a first section of the plug-in receptable 23a the switching device 38a, b is closed and load is routed through switching device 38a, b. Once one of the electrical contact elements 21a, b contacts a second section of the plug-in receptable 23a then switching device 38a, b is opened and load is routed only through the second section of the plug-in receptable 23a. In another embodiment not covered by the present invention the switching device 38a, b e.g. comprising a relay and / or a MOSFET is open in then non-operating state. One of the electrical contact elements 21a, b is provided with a branched-off contact element that can be received by a branched-off and reset arranged additional plug-in receptable 23a, b. Once one of the electrical contact elements 21a, b is received by the corresponding plug-in receptable 23a, b the switching device 38a, b is closed and load controlled by switching device 38a, b. As soon as the branched-off contact element is received in the branched-off and reset arranged additional plug-in receptable the switching device 38a, b is opened and load routed only through the branched-off and reset arranged additional plug-in receptable. Also in this embodiment determination of the connection status is made by light signals emitted by light source 33, received by photosensors 34 and after the signals are evaluated in the control unit 28. Applicant: HARTING International Innovation AG Title: Pair of electrical connectors and method for determining a connection status of the pair of electrical connectors Reference numerals 20 pair of electrical connectors 21a, b electrical contact element 22 first housing portion 23a, b plug-in receptable 24 second housing portion 25 load 26 voltage source 27 first power supply 28 control unit 29 extension 30 recess 31 push-button 32 end face 33 light source 34 photosensor 35 second power supply 36 reflective element 37a, b fiber path 38a, b switching device 39 voltage limiting device 40 Z-diode 41 resistor Applicant: HARTING International Innovation AG Title: Pair of electrical connectors and method for determining a connection status of the pair of electrical connectors

Claims

1. Pair of electrical connectors (20) having a first housing portion (22) and a second housing portion (24) which can be connected to the first housing portion (22), wherein at least a first and a second electrical contact element (21a, b) is provided in the first housing portion (22) for connection to a respective first and a second plugin receptacle (23a, b) provided in the second housing portion (24) for establishing an electrically conductive connection between a load (25) side and an voltage source (26) side, characterised by a detection means for detecting a signal indicative for a connection status of the pair of electrical connectors (20), with the detection means being connected to a control unit (28) for analysing the indicative signal received from the detection means and for, depending on the connection status of the pair of electrical connectors (20), activating or deactivating a switching device (38a, b) to control an electrical current during coupling and decoupling of the pair of electrical connectors (20).

2. Pair of electrical connectors (20) according to claim 1, characterized in that a first power supply unit (27) for powering the detection means, the control unit (28) and the switching device (38a, b) is provided in the first or second housing portion (22, 24).

3. Pair of electrical connectors (20) according to claim 1 or 2, characterized in that the detection means are positioned on an extension (29) provided in the first housing portion (22) and arecess (30) for inserting the extension (29) in the second housing portion (24).

4. Pair of electrical connectors (20) according to any of claims 1 to 3, characterized in that the detection means comprises optical means, wherein the optical means have at least one light source (33) and at least one photosensor (34, 34', 34”) for a detection of a light signal emitted by the light source (33).

5. Pair of electrical connectors (20) according to claim 4, characterized in that the optical means are arranged on the extension (29) and / or in the recess (30) and the signal indicative for a connection status is derived from one of the detection of the light signal by the at least one photosensor (34, 34', 34”) or an interruption of the detection of the light signal by the at least one photosensor (34, 34', 34”).

6. Pair of electrical connectors (20) according to claim 4 or 5, characterized in that the light source (33) and the at least one photosensor (34, 34', 34”) are arranged in the recess (30) with the extension (29) having guiding means for guiding the light signal from the light source (33) to the at least one photosensor (34, 34', 34”) or with the extension (29) being designed to interrupt the light signal.

7. Pair of electrical connectors (20) according to claim 6, characterized in that the guiding means are designed as optical conductors, in particular as a fibre optic light guide or a reflective element (36), in particular a mirror.

8. Pair of electrical connectors (20) according to any of claims 1 to 3, characterized in that the detection means is configured as a mechanical detection means, in particular a push-button (31) ora switch wherein the detection means is arranged in the recess (30) and the extension (29) is designed to actuate the push-button (31) or switch, wherein a signal indicative for a connection status is derived from the detection of a push-button (31) or switch actuation.

9. Pair of electrical connectors (20) according to any of claims 4 to 7, characterized in that a second power supply unit (35) is provided in the housing to supply power to the light source (33).

10. Pair of electrical connectors (20) according to any of claims 1 to 8, characterized in that the switching device (38a, b) is arranged in parallel or in series with a voltage source (26).

11. Pair of electrical connectors (20) according to any of claims 1 to 10, characterized in that the switching device (38a, b) is configured as a semiconductor switch.

12. Pair of electrical connectors (20) according to claim 11, characterized in that the semiconductor switch comprises a MOSFET and a relay in parallel connection or a MOSFET and a resistor in series connection.

13. Pair of electrical connectors (20) according to any of claims 1 to 12, characterized in that a voltage limiting device (39) is provided in at least one of the housing portions (22, 24).

14. Pair of electrical connectors (20) according to any of claims 1 to 12, characterized in that the first or the second portion (22, 24) of the housing is connected to the voltage source (26).

15. Method for determining a connection status of the pair of electrical connectors (20) according to any one of claims 1 to 14, comprising the steps of:• Contacting at least one of the electrical contact elements (21a, b) provided in the first portion (22) of the housing with the corresponding plug-in receptacles (23a, b) provided in the second portion (24) of the housing,• Emitting a signal indicative for the connection status of the pair of electrical connectors (20),• Analysing the signal by the control unit (28),• Emitting a control signal by the control unit (28) to control switching of a switching device (38a, b) for one of establishing or interrupting a voltage supply depending on the connection status of the pair of electrical connectors (20).

16. Method according to claim 15, characterised in that the switching device (38a, b) establishes a shortcut depending on the connection status of the pair of electrical connectors (20) thereby quenching a light arc formation during coupling or decoupling of the pair of electrical connectors (20).

17. Method according to claim 15 or 16, characterised in that the switching device (38a, b) is configured as hybrid switch comprising a MOSFET and a relay in parallel connection, wherein the control unit (28) emits a control signal to the hybrid switch to switch on when a completed coupling of the pair of electrical connectors (20)is detected and to switch off when a decoupling of the pair of electrical connectors (20) is detected.

18. Method according to claim 15 or 16, characterised in that the switching device is configured as hybrid switch comprising a MOSFET and a resistor in series connection, wherein the control unit (28) emits a control signal to the hybrid switch to switch on when a signal for decoupling of the pair of electrical connectors (20) is detected and to switch off when a signal for the complete coupling of the pair of electrical connectors (20) is detected by the control unit (28).

19. Method according to any of claims 15 to 18, characterized in that the signal indicative for a connection status of the pair of electrical connectors (20) is a mechanically or optically induced signal.

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