JP6338078B1 - Energy meter inspection device - Google Patents

Abstract

An electric energy meter inspection device having a simple configuration, high versatility and safety, and capable of performing inspection relatively easily. An watt-hour meter inspection apparatus for inspecting an installed watt-hour meter, wherein the plug is electrically connected to an outlet and an outlet. The main body 11 having a male connector, the terminal connector 12 configured to be able to electrically connect the male connector of the main body 11 and the load side terminal 101 of the watt hour meter 100, and terminal connection when the watt hour meter 100 is inspected A suspension tool 16 configured to be able to suspend the main body 11 so that tension due to the weight of the main body 11 is not applied to the tool 12, and the main body 11 is provided between the outlets 23 and 24 and the male connector. An earth leakage circuit breaker 22 with neutral wire phase loss protection is provided. [Selection] Figure 2

Description

  The present invention relates to a watt-hour meter inspection device that performs operation check and simple inspection of an installed watt-hour meter.

  When a meter failure of a watt hour meter already installed in a house or the like is suspected, an inspection device or the like is appropriately connected to the load side terminal of the watt hour meter to perform an operation check of the watt hour meter and a simple inspection. Such a watt-hour meter inspection device is a dedicated inspection device and has a low production volume and low availability. Moreover, in the inspection by the conventional inspection apparatus, it was necessary to bring a stopwatch and a calculator for conversion calculation of the instrument constant separately.

  In addition, the applicant has already filed an application for a watt-hour meter inspection device capable of performing a series of inspections such as a wiring method, voltage, phase rotation, and operation confirmation associated with installation of a watt-hour meter (Patent Document) 1). The watt hour meter inspection device is configured such that the terminals are arranged in accordance with the arrangement and pitch of the watt hour terminals, and the inspection can be performed simply by being inserted into the terminal portion of the watt hour meter.

JP 2007-225881 A

  According to the watt-hour meter inspection device described in Patent Document 1, it is not necessary to separately prepare a stopwatch or a calculator for conversion calculation of meter constants when the watt-hour meter is inspected. Moreover, it is possible to perform an inspection simply by inserting it into the terminal portion of the watt hour meter, and it is possible to reliably prevent erroneous connection.

  However, the watt-hour inspection device described in Patent Document 1 becomes a dedicated inspection device according to the arrangement and pitch of the terminals of each watt-hour meter, and remains a problem in terms of availability and versatility. There is no need to prepare a stopwatch or a calculator for conversion calculation of meter constants, but it is necessary to prepare a plurality of inspection devices according to the number of watt-hour meters having different terminal arrangements and pitches.

  Moreover, in the conventional inspection device and the watt-hour meter inspection device described in Patent Document 1, there is a risk of being damaged by an electric shock or the like when a short circuit or leakage occurs.

  An object of the present invention is to provide a watt-hour tester having a simple configuration, high versatility and safety, and capable of performing a test relatively easily.

  The present invention is a watt-hour meter inspection device for inspecting an installed watt-hour meter, and a main body having an outlet capable of electrically connecting an insertion plug and a connector electrically connected to the outlet; A terminal connector configured to be electrically connectable to the connector of the main body and a load side terminal of the watt hour meter, and tension due to the weight of the main body is applied to the terminal connector during inspection of the watt hour meter. A suspending tool configured to be able to suspend the main body so that the main body is provided with a circuit breaker between the outlet and the connector. Inspection equipment.

  Further, in the watt-hour test apparatus according to the present invention, the hanging tool includes a gripping tool that grips the gripped portion, a string that is attached to the gripping tool and the main body and suspends the main body from the gripped portion, An adjustment tool capable of adjusting the length of the string from the gripped portion to the main body, and in the state where the gripped portion is gripped by the gripping tool, the terminal connection tool is The length of the string from the gripped portion to the main body is adjustable so that tension due to the weight of the main body is not applied.

  The watt-hour tester of the present invention further includes a current measuring tool connectable to the outlet of the main body, and the current measuring tool is provided at one end of the electric wire and the electric wire and can be electrically connected to the outlet. And a plug receiver provided at the other end of the electric wire, and a loop portion that enables current measurement by a clamp meter is provided in the middle of the electric wire.

  In addition, the watt-hour meter inspection device of the present invention further includes an outlet connector that enables the terminal connector to be connected to a load-side outlet connected to the load-side terminal of the watt-hour meter, and the outlet connector Has an electric wire, an insertion plug provided at one end of the electric wire and electrically connectable to the load-side outlet, and a terminal provided at the other end of the electric wire and capable of electrically connecting the terminal connector. The terminal connector is capable of electrically connecting the connector of the main body and the load side terminal of the watt hour meter via the outlet connector and the load side outlet.

  In the watt-hour meter inspection device of the present invention, the main body includes a plurality of outlets, and the plurality of outlets are configured to be able to connect different types of plugs to each other. .

  According to the watt-hour meter inspection device of the present invention, the configuration is simple, and no special measuring device is required for the operation check and the simple inspection of the watt-hour meter. Moreover, it is applicable not only to the terminal arrangement and pitch but also to the operation check and simple inspection of a plurality of watt-hour meters having different ratings, and is highly versatile. Furthermore, since the main body is equipped with an earth leakage breaker, it is possible to suppress damage due to overcurrent and electric leakage due to a short circuit, and safety is high.

It is a perspective view of the main body 11 and the terminal connection tools 12 and 13 of the watt-hour meter test | inspection apparatus 1 of 1st Embodiment of this invention. It is a front view which shows a part of watt-hour meter test | inspection apparatus 1 of 1st Embodiment of this invention of the state connected to the watt-hour meter. It is a front view which shows the state which connected the dryer 110 to the watt-hour meter test | inspection apparatus 1 of 1st Embodiment of this invention. It is a side view of the electric current measurement tool 14 of the watt-hour test | inspection apparatus 1 of 1st Embodiment of this invention. It is a front view which shows the state which connected the dryer 110 to the watt-hour test | inspection apparatus 2 of 2nd Embodiment of this invention. It is a front view which shows the state which connected the dryer 110 to the watt-hour meter test | inspection apparatus 3 of 3rd Embodiment of this invention.

  FIG. 1 is a perspective view of a main body 11 and terminal connectors 12 and 13 of a watt-hour meter inspection device 1 according to a first embodiment of the present invention. FIG. 2 is a front view showing a part of the watt-hour meter inspection device 1 according to the first embodiment of the present invention in a state connected to the watt-hour meter 100. FIG. 3 is a front view showing a state in which the dryer 110 is connected to the watt-hour meter inspection apparatus 1 according to the first embodiment of the present invention. FIG. 4 is a side view of the current measuring tool 14 of the watt-hour testing device 1 according to the first embodiment of the present invention. In FIG. 1, the hanging tool 16 is omitted.

  The watt-hour meter inspection device 1 of the present embodiment includes a main body 11 capable of connecting an arbitrary load (electric device) such as a dryer 110 to the watt-hour meter 100, a load-side terminal 101 of the watt-hour meter 100, and the main body 11. Terminal connecting tools 12 and 13 for connecting terminals, current measuring loop sections 54 and 55 for current measurement, a current measuring instrument 14 for connecting an arbitrary load and the main body 11, and a current measuring instrument via the loop sections 54 and 55. 14 is provided with a clamp meter 15 for measuring the current flowing through 14 and a hanging tool 16 for suspending the main body 11 on the watt hour meter 100 or the like, and an arbitrary load is applied to the watt hour meter 100 via the watt hour meter inspection device 1. The operation check of the watt hour meter 100 is performed by connecting and operating, and the power consumption measured by the watt hour meter 100 and the power consumption (amount) based on the measured value of the current flowing through the current measuring tool 14 are collated. By the amount of power 100 perform a simple test of. In this description, the connection basically means an electrical connection.

  The main body 11 includes a rectangular parallelepiped casing 21, a neutral circuit breaker 22 with a phase failure protection, a 100 V outlet 23, a 200 V outlet 24, and an upper surface of the casing 21. And a male connector 25 for connecting the terminal connectors 12 and 13. As shown by an imaginary line in FIG. 1, the earth leakage circuit breaker 22 with neutral wire phase loss protection, the 100V outlet 23, the 200V outlet 24 and the male connector 25 are connected to each other through the wiring 27 inside the housing 21. Has been.

  The neutral circuit breaker with neutral phase open circuit protection 22 is a single-phase three-wire neutral circuit breaker with neutral phase open phase protection, and the male connector 25 is connected to the power supply side (upper side in FIG. 1) via the wiring 27. The 100V outlet 23 and the 200V outlet 24 are connected to the load side (lower side in FIG. 1) via the wiring 27. Note that, for example, a circuit breaker for wiring may be used instead of the leakage breaker 22 with neutral wire phase loss protection, but it is preferable to use a circuit breaker in consideration of safety. It is more preferable to use a circuit breaker with neutral wire phase loss protection that instantaneously cuts off even when 12 is misconnected and 200 V is applied.

  The 100V outlet 23 and the 200V outlet 24 are a well-known single-phase 100V outlet and a single-phase 200V outlet, respectively. Is wired so that is applied.

  The male connector 25 has three terminals 28a, 28b, and 28c, and is a connector in which female connectors 42 and 43 of the terminal connectors 12 and 13 described later can be attached and detached. The shape of the male connector 25 is not limited to a specific shape, but by making it a trapezoid as shown in FIG. 1, the female connectors 42 and 43 can be connected only in one direction, and reverse connection can be prevented. Further, the male connector 25 and the female connectors 42 and 43 of the terminal connectors 12 and 13 may be provided with protrusions, grooves (not shown) or the like that restrict the direction in which they can be connected to each other.

  The terminal connectors 12 and 13 are for 100V and 200V, respectively, and have female connectors 42 and 43 at one end (the lower end in FIG. 1) of the electric wire 41 and a conductive clip 44 at the other end (the upper end in FIG. 1). ing. The terminal connector 12 for 100 V is configured such that the terminals 45 b and 45 c of the female connector 42 are connected to the terminals 28 b and 28 c (center and right side in FIG. 1) of the male connector 25 of the main body 11. The terminal connector 13 for 200 V is configured so that the terminals 45 a and 45 c of the female connector 43 are connected to the terminals 28 a and 28 c (left and right sides in FIG. 1) of the male connector 25 of the main body 11.

  The conductive clip 44 is a so-called crocodile clip, but is not limited to this, and may be conductive as long as it has conductivity and can be attached to and detached from the load-side terminal 101 of the watt-hour meter 100. The 100V terminal connector 12 and the 200V terminal connector 13 use conductive clips 44 having different color combinations so that they can be distinguished from each other. However, when the terminal connector 12 for 100V and the terminal connector 13 for 200V are identified by another method, for example, a tape or the like, the color of the conductive clip 44 may not be changed.

  The current measuring tool 14 has a plug 52 at one end (the upper end in FIGS. 3 and 4) of the electric wire 51 and a plug receiver 53 at the other end (the lower end in FIGS. 3 and 4). One loop portion 54 and 55 for current measurement is provided in the middle of the two electric wires 51. The current measuring tool 14 shown in FIGS. 3 and 4 is for 100V. The 200V current measurement tool (not shown) is configured by replacing the plug 52 and plug receptacle 53 of the 100V current measurement tool 14 with those for 200V.

  The plug 52 is basically connected to the 100V outlet 23 of the main body 11, and the plug receiver 53 is basically connected to an arbitrary load such as the dryer 110.

  The clamp meter 15 is a known clamp meter for current measurement, and the current flowing through the loop portions 54 and 55 is measured by inserting one of the loop portions 54 and 55 of the current measuring tool 14 into the measurement portion 61.

  The hanging tool 16 includes a ring-shaped string 31 inserted into two through holes 29 penetrating from the left and right upper parts of the front surface of the housing 21 of the main body 11 to the back surface, and a laundry scissors that suspends the main body 11 via the string 31. And the three adjusting tools 33 for adjusting the length of the portion of the string 31 that suspends the main body 11.

  The gripping tool 32 can grip at least a part of the watt-hour meter 100 including the case 102 that houses the main body of the watt-hour meter 100, and holds the part of the watt-hour meter 100 via the string 31. The main body 11 only needs to be configured to be hangable, and is not limited to a specific configuration. However, the gripping tool 32 needs a gripping force that does not fall off the wattmeter 100 due to the weight of the main body 11 when the main body 11 is suspended via the string 31 while a part of the wattmeter 100 is gripped. .

  Further, on the assumption that the watt hour meter 100 does not fall off, instead of the gripping tool 32, for example, a suction tool (not shown) sucked on a part of the watt hour meter 100, a part of the watt hour meter 100, etc. You may make it hang | hang the main body 11 using the latching tool (illustration omitted) etc. which stop.

  The adjustment tool 33 is a so-called cord stopper configured to be slidable on the string 31 while being pinched with a finger. The adjustment tool 33 is not limited to this, and an arbitrary configuration that can be easily moved and fixed on the string 31 can be used. In addition, the number of adjustment tools 33 may be one, two, or four or more. Furthermore, you may adjust the length of the part which hangs the main body 11 in the string 31 by providing a knot in the arbitrary positions on the string 31 without using the adjustment tool 33.

  Next, an operation check and a simple inspection method of the watt-hour meter 100 by the watt-hour meter inspection device 1 of the present embodiment will be described. First, the neutral breaker 22 with the phase failure protection of the main body 11 is turned off, and the terminal connector 12 is connected to the male connector 25. In this description, the terminal connector 12 for 100V is used, but the terminal connectors 12 and 13 may be properly used according to the rated voltage of the watt-hour meter 100 to be inspected.

  Next, the front side (not shown) of the case 102 of the watt-hour meter 100 is removed, and the hanging tool 16 is gripped in order to prevent the main body 11 from dropping by the string 31 and the gripping tool 32 of the hanging tool 16. The tool 32 is attached to the upper edge of the back side of the case 102 of the watt hour meter 100, the adjustment tool 33 of the hanging tool 16 is slid on the string 31, and the conductive clip 44 is connected to the load side terminal 101 of the watt hour meter 100. The position of the main body 11 is determined by adjusting so that tension is not applied to the conductive clip 44 and the gripping tool 32 when connected.

  After the position of the main body 11 is determined, a terminal cover (not shown) covering the load side terminal 101 of the watt hour meter 100 is removed, and then the conductive clip 44 is connected to the load side terminal 101 of the watt hour meter 100. When the procedure so far is executed, the state shown in FIG. 2 is obtained.

  Next, the plug 52 of the current measuring tool 14 is connected to the 100V outlet 23 of the main body 11, and an arbitrary load such as the dryer 110 is connected to the plug receiver 53 of the current measuring tool 14. The measuring unit 61 of the clamp meter 15 is attached to one loop unit 54 of the current measuring tool 14. When the procedure so far is performed, the state shown in FIG. 3 is obtained. At this time, the dryer 110 is appropriately placed on a shelf or a stand (not shown), and the operator holds only the clamp meter 15.

  Next, after turning on the switch of the dryer 110, the neutral breaker 22 with the phase failure protection of the main body 11 is turned on, the dryer 110 is operated, and the operation of the watt hour meter 100 is confirmed. The power consumption (amount) based on the current measurement value of the clamp meter 15 and the power consumption amount measured by the watt hour meter 100 are collated. The power consumption (kW) based on the current measurement value of the clamp meter 15 is obtained by the current measurement value (A) × 100 (V) of one of the loop portions 54 and 55 in the case of the single-phase two-wire 100V.

In addition, the power consumption amount W (kWh) measured by the watt hour meter 100 is expressed by Expression (1) in the case of the induction type watt hour meter 100 having the disk 103.
W = r / (t × A) × 3600 (sec) (1)
Here, the variable t is the measurement time (sec), the variable r is the rotation speed (rev) of the disk 103 during the measurement time, and the constant A is the rotation speed (rev / kWh) of the disk 103 per kWh.

  As an example, when t = 60 (sec) and A = 600 (rev / kWh), it can be obtained by W = r / 10. The operator measures the rotational speed r of the disk 103 for 60 seconds using a stopwatch, a timer, etc., calculates the measured rotational speed r / 10, and calculates the power consumption measured by the watt-hour meter 100. By checking this with the power consumption based on the current measurement value of the clamp meter 15, the watt-hour meter 100 can be simply inspected.

  As described above, the watt-hour meter inspection device 1 of the present embodiment has a simple configuration, and does not require a special measuring device for the operation check and the simple inspection of the watt-hour meter 100, and the availability of the constituent members is low. good. Further, it is applicable not only to the terminal arrangement and pitch but also to the operation confirmation and simple inspection of a plurality of watt-hour meters 100 having different ratings, and the versatility of the device itself is high. Further, the current can be directly measured safely by the clamp meter 15 using the current measuring tool 14. Furthermore, since the main body 11 is equipped with the ground fault circuit breaker 22 with neutral wire phase loss protection, it is possible to suppress secondary damage due to overcurrent due to a short circuit or current leakage, and safety is high.

  Moreover, since the main body 11 can be supported by the hanging tool 16, the operator does not need to support the main body 11, and workability is improved. Furthermore, since the hanging tool 16 can be fixed to not only the watt hour meter 100 but also various structures by the gripping tool 32, the versatility is high. Moreover, the suspending tool 16 can adjust the length of the string 31 easily with the adjusting tool 33, and is convenient.

  FIG. 5 is a front view showing a state in which the dryer 110 is connected to the watt-hour tester 2 according to the second embodiment of the present invention. The same code | symbol is attached | subjected to the structure same as the watt-hour meter test | inspection apparatus 1 of 1st Embodiment shown in FIGS. 1-4, and description is abbreviate | omitted. The watt-hour meter inspection device 2 of the present embodiment has the same basic configuration as the watt-hour meter inspection device 1 of the first embodiment, but instead of the current measuring tool 14 and the clamp meter 15, a power meter 71 is provided. I have.

  The power meter 71 is a so-called watt hour meter, watt checker, or watt monitor, and is a device that can be connected between an outlet and an arbitrary load (electrical device) to measure power consumption. An insertion plug (not shown) that can be connected to the 200V outlet 24 and a plug receptacle (not shown) that can connect an arbitrary load are provided. In FIG. 5, the 100V outlet 23 of the main body 11 and the dryer 110 are connected to each other. Connected between.

  In the watt-hour meter inspection device 2 of the present embodiment, the operation check of the watt-hour meter 100 is performed by comparing the power consumption (amount) measured by the power meter 71 with the power consumption amount measured by the watt-hour meter 100. Since simple inspection can be performed and complicated calculation such as conversion of instrument constants is not required, calculation according to equation (1) is not required, and a calculator such as a stopwatch or timer is not required.

  FIG. 6 is a front view illustrating a state in which the dryer 110 is connected to the watt-hour meter inspection device 3 according to the third embodiment of the present invention. In FIG. 6, the hanging tool 16 is omitted. The same components as those of the watt-hour inspection device 2 of the second embodiment shown in FIG. The watt-hour meter inspection device 3 of the present embodiment has the same basic configuration as the watt-hour meter inspection device 2 of the second embodiment, but the terminal connector 12 is connected to the load-side terminal 101 of the watt-hour meter 100. An outlet connector 81 for connecting to the load-side outlet 120 is provided. The watt-hour meter inspection device 3 of the present embodiment performs an operation check and a simple inspection of the watt-hour meter 100 via the load-side outlet 120. For convenience of explanation, the load-side outlet 120 is used, but the load-side outlet 120 is a general outlet.

  The outlet connector 81 includes an insertion plug 83 at one end of the electric wire 82 and a terminal 84 for connecting the conductive clip 44 of the terminal connector 12 to the other end. At the time of operation check and simple inspection of the watt-hour meter 100 in the watt-hour inspection device 3 of the present embodiment, the plug 83 of the outlet connector 81 is inserted into the load-side outlet 120 and the terminal 84 is held by the conductive clip 44. To do.

  Each of the terminals 84 has a spherical insulator 85 at the base end thereof, and the conductive clips 44 connected to the respective terminals 84 are in contact with each other in a state where the insulators 85 are in contact with each other so as not to be short-circuited. A spherical diameter of 85 is determined (see FIG. 6).

  According to the watt-hour meter inspection device 3 of the present embodiment, the operation check and simple inspection of the watt-hour meter 100 through the load-side outlet 120 can be performed by using the outlet connector 81. In addition, in order to check the operation of the watt-hour meter 100 and perform a simple inspection, it is also possible to educate and conduct training on the inspection implementation method using the outlet power source installed at the office etc. It becomes. The plug 83 of the outlet connector 81 can be appropriately changed according to the rated voltage of the watt-hour meter 100 and / or the load-side outlet 120, and the terminal 84 is also appropriately changed according to the type of the conductive clip 44. It can be changed.

  As mentioned above, although the watt-hour meter test | inspection apparatus of this invention was demonstrated using the watt-hour meter test | inspection apparatus 1,2,3 of 1st to 3rd embodiment, the watt-hour meter test | inspection apparatus of this invention is the said embodiment. However, the present invention is not limited to the above and can be modified without changing the gist. For example, the shape of the housing 21 of the main body 11 is not limited to a rectangular parallelepiped.

  Moreover, in the watt-hour meter inspection apparatus of the present invention, the embodiment has been described by dividing it into three. However, in consideration of actual operation, as the watt-hour meter inspection apparatus, the main body 11, the terminal connectors 12, 13 and the current measuring tool. 14, a clamp meter 15, a hanging tool 16, a power measuring instrument 71 and a set of outlet connector 81 are accommodated in a storage case (not shown) and carried, and matched to a watt hour meter that is subject to operation check and simple inspection. Then, the operation check and the simple inspection may be performed using what is necessary. At this time, an arbitrary load such as a stopwatch or dryer 110, a multi-tap, or the like may be stored in the storage case as appropriate.

  In addition, the watt-hour meter inspection device of the present invention is not only for operation confirmation and simple inspection for the induction-type watt-hour meter 100 having the disk 103, but also for other types of watt-hour meters, such as electronic watt-hour meters and smart meters. It can also be applied to operation confirmation and simple inspection.

  As described above, the preferred embodiments have been described with reference to the drawings. However, those skilled in the art will readily understand various changes and modifications within the obvious scope by looking at the present specification. Therefore, such changes and modifications are interpreted as being within the scope of the invention defined by the claims.

1, 2, 3 Electricity meter inspection device 11 Main body 12, 13 Terminal connection tool 14 Current measurement tool 15 Clamp meter 16 Hanging tool 22 Leakage circuit breaker with neutral wire phase failure protection 23 Outlet for 100V 24 Outlet for 200V 25 Male Connector 27 Wiring 31 String 32 Gripping tool 33 Adjusting tool 42, 43 Female connector 44 Conductive clip 51, 82 Electric wire 52, 83 Plug plug 53 Plug receiver 54, 55 Loop part 71 Power measuring device 81 Connector for outlet 84 Terminal 85 Insulation Body 100 Energy meter 101 Load side terminal 103 Disc 110 Dryer 120 Load side outlet

Claims (5)

An watt-hour meter inspection device for inspecting an installed watt-hour meter,
A main body having an outlet capable of electrically connecting the plug and a connector electrically connected to the outlet;
A terminal connector configured to be electrically connectable to the connector of the main body and the load side terminal of the watt-hour meter;
A hanging tool configured to be able to suspend the main body so that tension due to the weight of the main body is not applied to the terminal connector during inspection of the watt-hour meter,
With
The power meter inspection device according to claim 1, wherein the main body includes a circuit breaker between the outlet and the connector.   The hanging tool includes a gripping tool for gripping a gripped portion, a string attached to the gripping tool and the main body, and a strap for suspending the main body from the gripped portion, and the string from the gripped portion to the main body. An adjustment tool capable of adjusting the length, and in a state where the gripped part is gripped by the gripping tool, the terminal connection tool is not subjected to tension due to the weight of the main body when the watt-hour meter is inspected. The watt-hour meter inspection device according to claim 1, wherein the length of the string from the gripped portion to the main body is adjustable. Furthermore, a current measuring tool that can be connected to the outlet of the main body,
The current measuring tool includes an electric wire, an insertion plug provided at one end of the electric wire and electrically connectable to the outlet, and a plug receiver provided at the other end of the electric wire, and measures current with a clamp meter. The watt-hour meter inspection device according to claim 1, wherein a loop portion that can be provided is provided in the middle of the electric wire. Furthermore, it comprises a connection tool for an outlet that enables the terminal connection tool to be connected to a load-side outlet connected to the load-side terminal of the watt-hour meter,
The outlet connector is an electric wire, an insertion plug provided at one end of the electric wire and electrically connectable to the load-side outlet, and the terminal connector provided at the other end of the electric wire. Have the terminals
2. The terminal connector is capable of electrically connecting the connector of the main body and a load side terminal of the watt hour meter via the outlet connector and the load outlet. 4. The watt-hour meter inspection device according to any one of items 1 to 3. The main body includes a plurality of the outlets,
The watt-hour inspection device according to any one of claims 1 to 4, wherein the plurality of outlets are configured so that different types of plugs can be connected to each other.

Images