JPH09180560A - Insulator device with built-in protection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fracture of a current limiting element and an insulator main body even when a short circuit is caused by the deterioration of the current limiting element, to flow a dynamic current arc, and miniaturize the whole insulator device. SOLUTION: Upper and lower spaces 2m and 2n are formed on an insulator body 2. A metallic housing member 3b and a current limiting element 9 are housed in the upper space 2m and the housing member 3b respectively. A leading out electrode 12, connected to the lower end of the element 9, is protruded in the space 2n, and the outer surfaces of the element 9 and the electrode 12 are covered with an insulating member 16. One end of the element 9 is connected to an insulated wire 7, arranged in the head part of the insulator body 2, to connect the tip of the electrode 12 to a base metallic fitting 20 connected to an crossarm metal 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an insulator device with a built-in protective device, which can reliably prevent unbalanced breakdown of the insulator due to a follower current arc at the time of a flashover and melting accident of an insulated wire. The present invention relates to an insulator device with a built-in protective device having a compact overall structure.

[0002]

2. Description of the Related Art In recent years, a protective device having a lightning protection function has been provided for an insulator device supporting an insulated wire in a high-voltage distribution line. The type of this protection device is a so-called current limiting arc horn type in which a current limiting element is arranged in an arc horn,
There are an insulator built-in type in which the current limiting element is built in the main body insulator, and an external insulator type in which a current limiting element unit is preassembled and attached to the insulator body.

In these protective devices, when a lightning strike occurs somewhere on the high-voltage power distribution line, and an abnormally high voltage such as lightning surge propagates through the distribution line (insulated wire) and enters. The serge is quickly released to the ground through a protective device provided in the insulator device, which is a weak point in terms of insulation, and the current limiting element of the protective device interrupts the follow-up arc caused by the flashover. This is intended to prevent the accidental breakdown of the insulator body and the blowout accident of the insulated wire due to the generation of the follow current arc.

[0004]

By the way, in the above-mentioned conventional protection device, when the current limiting element deteriorates due to long-term use or a lightning surge exceeding the performance is intruded, the current limiting element flashes ( It may be destroyed due to an accident such as short circuit), but in such a case, not only destruction of the current limiting element but also the main body insulator (insulating container) is damaged, resulting in stoppage of use or function stoppage. There's a problem.

Further, in the type in which the protective device is attached, there is a problem that the size and weight of the entire insulator device cannot be avoided. Further, in the case of the conventional external discharge gear-up type, there is a problem in operation such that the discharge starting voltage is varied and the discharge characteristics are not stable and sufficient protection characteristics cannot be exhibited because it is easily affected by the surroundings.

Further, particularly in the case of the current limiting arc horn type, the discharge starting voltage varies and the device is mounted in a state that it greatly protrudes to the side, so that it is mounted on the column, aesthetically,
There is also a problem with insulation.

[0007]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned various problems, and the first invention is an insulator body (2) in which an upper space (2m) and a lower space (2n) are formed in the body. )
A base metal fitting (20) for fixing the lower part of the insulator body (2) to the armrest (27), and a cap fitting provided on the head of the insulator body (2) and electrically connected to the insulated wire (7). (3)
A metal housing member (36) housed in the upper space (2 m), a current limiting element (9) housed in the housing member (36), and a current limiting element (9). A lead-out electrode (12) connected to one end and protruding into the lower space (2 m)
And a current limiting element unit (8) consisting of the current limiting element (9) and an insulating member (16) such as rubber covering the outer peripheral surface of the lead-out electrode (12). (9)
Of the lead-out electrode (12) electrically connected to the cap fitting (3) on the opposite side to the lead-out electrode (12).
2) A device with a built-in protection device, characterized in that the tip of the protruding side of 2) is electrically connected to the base metal fitting (20) directly or through a discharge gap (G) of a predetermined length.

The second invention is that the upper space (2
i) and an insulator body (2) forming a lower space (2h), a base metal fitting (20) for fixing the lower portion of the insulator body (2) to the arm member (27), and a head portion of the insulator body (2). The cap metal fitting (3) provided and electrically connected to the insulated wire (7), the metal storage member (20d) stored in the lower space (2h), and the storage member (20d). The contained current limiting element (9) and the lead-out electrode (12) connected to one end of the current limiting element (9) and protruding into the upper space (2i).
And a current limiting element unit (8) consisting of the current limiting element (9) and an insulating member (16) such as rubber covering the outer peripheral surface of the lead-out electrode (12). (9)
Of the lead-out electrode (12) electrically connected to the base metal fitting (20).
2) An insulator device with a built-in protection device, characterized in that the tip of the protruding side of 2) is electrically connected to the cap metal fitting (3) directly or through a discharge gap (G) of a predetermined length.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below based on the embodiments shown in the drawings. FIG. 1 shows a first embodiment of an insulator device with a built-in protective device of a gear-up type.

Reference numeral 1 denotes an insulator device having a built-in protective device. A cap metal member 3 made of iron, stainless steel, or the like is attached to a head 2a of an insulator body 2 made of a deep groove insulator, and a cement-based or synthetic resin-based adhesive 4 is used. It is fixed by. Reference numeral 6 denotes a clamp portion for fixing the insulated electric wire 7 which is fixedly attached to the upper outer surface 3a of the cap metal fitting 3 by a welding metal fitting 18 described later or is integrally assembled with the cap metal fitting 3 to be sandwiched and connected. . The clamp portion 6 includes a receiving metal fitting 6a including a wire recess 6b and an inwardly projecting bladed electrode portion 6c provided in the recess 6b, and a tightening tool 6 including a bolt and a nut.
6d, and a metal fitting 6g made up of an electric wire recess 6e that is slid toward the receiving fitting 6a side or the opposite side by the tightening tool 6d and an inwardly projecting blade-equipped electrode portion 6f provided in the recess 6d. Etc.

Reference numeral 3b is a metal storage member made of iron or stainless steel plate, and in this embodiment, it is also used as the cap fitting 3 and is integrally formed as a part of the fitting 3. The storage member 3b is formed in the shape of a bag having a bottom with an open upper end. The storage member 3b is immersed in the upper space 2m formed on the upper side of the insulator body 2, and the storage member 3b is further retracted. The current limiting element unit 8 is housed from the upper end opening 3c side of the member 3b. It should be noted that the storage member 3b may be formed separately from the cap fitting 3 and may be built in the upper space 3m.

The current limiting element unit 8 includes a current limiting element 9 having ZnO (zinc oxide) as a main component, which is excellent in voltage non-linearity, and a charging side connected to an upper end of the current limiting element 9. The electrode 10, the ground-side electrode 11 arranged to be connected to the lower end of the current limiting element 9, and the one end 12a connected to the ground-side electrode 11 and the other end 12b through the lower space 2n on the lower side to the lower end side. A lead-out electrode 12 which is a charge-side discharge electrode extended downwardly until reaching (positioning) the base metal fitting 20, and a hemispherical discharge portion 13 formed at a lower end of the lead-out electrode 12. It is composed of an insulating member 16 such as EP rubber or EPR rubber integrally covering the outer peripheral surface of the lead-out electrode 12 excluding the discharge portion 13 and the outer peripheral surface of the current limiting element 9 excluding the upper surface 10a of the charging side electrode 10. ing.

In the current limiting element unit 8, the extended rod-shaped or lead-line-shaped lead-out electrode 12 is inserted into the opening 3e formed in the lower portion of the housing member 3b from above and the current limiting element is formed. Nine parts are stored and installed in the storage member 3b. With this storage, the discharge portion 13 at the lower end of the lead-out electrode 12 is positioned inside the vessel-shaped base metal fitting 20 fixed to the lower end of the insulator body 2 in the completed storage state.

Reference numeral 10 denotes a charging side electrode connected to the upper end 9a side of the current limiting element 9. After the current limiting element unit 8 is housed as described above, the closing metal fitting 18 and the pressure release plate 19 are placed on the charging side electrode 10. Is installed, and the current limiting element 9 is electrically connected to the cap fitting 3 via these. And
Filling a filling material 35 such as silicone resin, the filling material 3
The upper end opening 3c is closed by 5 and the closing metal member 18.

The current limiting element unit 8 is fixed by adhering the outer peripheral surface of the insulating member 16 to the inner peripheral surface of the accommodating member 3b with an adhesive 17 during the storage. In addition, from the opening 3e at the lower end of the storage member 3b to the lower space 2
A large number of pleats 16a are integrally formed on the insulating member 16 on the outer peripheral portion of the lead-out electrode 12 that protrudes downwards through n to increase the creepage distance between the discharge unit 13 and the opening 3e at the lower end of the storage member 3b. In this way, the insulation performance (withstand voltage characteristic) of the same area is improved.

Reference numeral 16b is a guide portion which abuts on the inner peripheral surface 2P of the lower space portion 2n, which is integrally formed with the insulating member 16 at the center of the group of folds 16a formed continuously.
The diameter is formed larger than the diameter of the pleats 16a.

Reference numeral 20 denotes a base metal fitting, which is formed in a bottomed cylindrical shape with an upper opening, is fitted around the lower portion of the body portion 2c of the insulator 2, and is made of cement or synthetic resin adhesive 22 to form a body portion. It is fixed to 2c. Further, a space D is formed between the bottom plate 20A of the base metal fitting 20 and the lower end 2j of the body portion 2c.

A partition plate 24 is fixed to the lower surface of the lower end 2j of the body portion 2c, and a through hole 24a is formed in the center thereof. Then, the lower portion 1 of the lead-out electrode 12
2b penetrates the through hole 24a with a slight distance to electrically insulate the partition plate 24, and the lower end of the lead-out electrode 12 projects into the space D. A discharge portion 13 having a hemispherical lower end is integrally formed with the protruding end (lower end).

Reference numeral 23 denotes a closing plate, which is located slightly above the discharge portion 13 and is fixedly provided on the lower portion 12b of the lead-out electrode 12 in a state of being slightly separated from the partition plate 24 so as to be electrically insulated. . In addition, the diameter of the closing plate 23 is equal to
The diameter is set larger than a.

Reference numeral 25 is a base auxiliary metal fitting formed in a bottomed cylindrical shape having an opening at the top, and the bottom plate thereof is the base metal fitting 2 described above.
It is placed on the bottom plate 20A of No. 0, and is concentrically provided in the space D with the upper end abutting the partition plate 24. A bolt 21 is fixedly provided vertically at the center of the base metal fitting 20, and the bolt 21 is attached to the attachment hole 27a of the arm 27.
The protection device-embedded insulator device 1 including the insulator body 2, the base metal 20 and the like is erected on the armor 27 by penetrating the same and tightening the mounting nut 28.

Reference numeral 21a denotes a discharge part having a hemispherical upper end, which is fixed to the central part of the base auxiliary metal fitting 25, that is, concentrically with the discharge part 13 and fixed to the upper surface of the bottom plate of the base auxiliary metal fitting 25, and The discharge unit 13 is opposed to the discharge unit 13 via a predetermined discharge gap G (preferably a short gap G).

Reference numeral 20c is a pressure release port formed in the space D of the base metal fitting 20, and reference numeral 25a is a pressure release port formed in the base auxiliary metal fitting 25 at a position facing the pressure release opening 20c.

Numeral 26 is a seal material which is attached to the pressure release port 20c as necessary and comprises a plug type, a lid type, a sealing plate, etc., and prevents rainwater from entering the metal fitting 20 through the pressure release port 20c. In addition, the seal material 26 is broken and scattered when the internal pressure rises when a follow-up arc occurs, and the pressure release port 20c is secured. It is also possible to form a mechanical weak point such as a notch in the base metal fitting 20 itself and to break that portion when the internal pressure rises so that the pressure is released from the portion.

In the insulator device 1 with a built-in protective device having the above construction, the bolt portion 21 on the side of the base metal fitting 20 is inserted into the mounting hole 27a of the arm member 27 of the electric pole, and the arm nut 27 is tightened by the mounting nut 28. It is attached.

With the insulated wire 7 interposed between the receiving metal fitting 6a and the pressing metal fitting 6g in the clamp part 6 of the cap fitting 3 on the head side, the tightening tool 6d is turned to gradually tighten the insulated wire 7. And clamp it in the clamp part 6. At this time, the bladed electrode portions 6c and 6f protruding inward cut the coating 7a of the insulated electric wire 7 or pierce it,
Since the core wire 7b contacts the core wire 7b, the core wire 7b of the insulated wire 7 and the cap 3 are mechanically and electrically connected. Then, after connecting the insulated wire 7, an insulating cover 29 is attached to the head portion 2a to cover the charging portion such as the cap fitting 3.

Next, the insulator device 1 with a built-in protective device having the above-mentioned configuration
Will be described. During normal times, the air insulation of the discharge part 13 of the lead-out electrode 12 and the ground-side base metal fitting 20, that is, the discharge gap G is sufficiently secured, and the protective device side does not operate at all.

In such a state, a lightning strike occurs somewhere, and the thunder serge propagates through the high-voltage distribution line (insulated wire), and if it is an abnormally high voltage, it is a weak point in insulation. A flashover occurs in the discharge gap G. The lightning surge includes insulated wire 7-clamp part 6, cap metal fitting 3-charge side electrode 10, current limiting element 9-ground side electrode 11, lead-out electrode 12, discharge part 13, discharge gap G-discharge part 21a. The base metal fitting 20-the arm 27 discharges quickly to the ground. In this case, since the current limiting element 9 and the discharge gap G are interposed in series in the discharge path as described above, the follow-up arc is interrupted, so that the insulation of the discharge gap G is restored and the discharge gap G returns to the normal state.

In some cases, the current limiting element 9 may deteriorate due to some reason such as long-term use, infiltration of moisture, or intrusion of lightning surge beyond its performance, and normal operation may not be expected in the protective device. In that case, the current limiting element 9 flashes outside the element or inside the element, and accordingly, a follow current arc flows in the discharge path. Since this follow-up arc naturally flows also in the discharge gearup G, the internal pressure in the base metal fitting 20 rapidly rises, which causes the pressure release port 20c.
After that, or the seal material 26 attached to the port 20c is immediately broken to secure the pressure release port 20c, and the raised pressure and arc are immediately released to the outside of the base metal fitting 20.

Further, in this case, since the closing plate 23 made of a thin plate member is bent upward due to the pressure increase, the insulator 2
It is possible to prevent the arc and the gas from flowing into the upper space 2m and the lower space 2n, so that the insulator body is prevented from being damaged or destroyed as much as possible, and the pressure is released safely. In this case, on the cap metal 3 side, the pressure relief plate 19 is reversed outward due to the pressure increase and is detached together with the filler 35, and the pressure is safely released upward from the detached portion through the gap with the clamp portion 6. .

FIG. 2 shows a second embodiment of the insulator-equipped insulator device with a gearup. Compared to the first embodiment shown in FIG. 1, the metal storage member 20d is integrally formed with the base metal fitting 20 fixed to the lower end side of the insulator body 2, and the storage member 20d is also provided on the lower side accordingly. It is largely different from the fact that it is arranged in the lower space 2h and the discharge gearup (G) is located on the upper end side of the cap fitting 3 side.

In the current limiting element unit 8, the lead-out electrode 12 is formed in the opening 20 formed in the upper portion of the housing member 20d.
It is stored in the storage member 20d in a state of protruding upward from g. After the storage, the lower end opening 20f is closed by the lid fitting 33 fixed to the bolt portion 21 by means such as welding and the sealing material 26 similar to the above.

In addition, a pressure-release plate 30 also serving as a sealing member, which is made of a thin metal such as a copper plate or a stainless plate for air-tightly closing the opening 3c on the upper end side of the cap member 3, is provided. A discharging portion 30a on the charging portion side that protrudes downward is provided in the central portion of the discharging portion 30.
In a, a predetermined discharge gap G (preferably a short gearup) is formed by the discharge portion 13 at the upper end 12c of the lead-out electrode 12 extending upward through the space 2i.

Reference numeral 31 denotes a filler such as silicone resin. Further, reference numeral 32 is a cap connecting metal fitting for connecting and connecting the cap metal fitting 3 and the clamp portion 6, and the above-mentioned discharge gear G is arranged so as to be located in the metal fitting 32.
Further, a pressure release port 32a is formed in a part of the side peripheral surface of the metal fitting 32. Further, if necessary, the pressure release port 32a is provided with a seal member 26 for preventing intrusion of rainwater or the like. The seal member 26 is a sheet-shaped, plug-shaped or lid-shaped member attached to the pressure release port. In addition, without providing the pressure release port 32a and the sealing material 26, a mechanical weak point such as a kerf is formed in the metal fitting 32, and the weak point is broken when the internal pressure rises by using this as a guide to release the pressure. But good.

The storage member 20d is a base metal fitting 2
It does not matter if it is made separately from 0 and built in the space 2h. Next, the operation of the insulator device 1 with the protective device having the configuration shown in FIG. 2 will be described.

In normal times, the air insulation of the discharge part 30a on the charging part side and the discharge part 13 on the ground side (lead-out electrode), that is, the discharge gap G is sufficiently secured, and the protective device side does not operate at all. .

In such a state, a lightning strike occurs somewhere, and the thunder serge propagates through the high-voltage distribution line (insulated wire), and if it is an abnormally high voltage, it is a weak point in insulation. A flashover occurs in the discharge gap G. The lightning surge includes insulated wire 7-clamp part 6, connecting fitting 32, cap fitting 3, pressure release plate 30, discharge gap G-discharge part 13,
The lead-out electrode 12-charge side electrode 36-current limiting element 9-ground side electrode 37-base metal fitting 20, bolt 21, and arm 27 are quickly discharged to the ground through the discharge path. In this case, since the current limiting element 9 and the discharge gap G are interposed in series in the discharge path as described above, the follow-up arc is interrupted, so that the insulation of the discharge gap G is restored and the discharge gap G returns to the normal state.

In some cases, the current limiting element 9 may deteriorate due to some reason such as long-term use, infiltration of moisture, or intrusion of lightning surge exceeding its performance, and normal operation of the protective device cannot be expected. In that case, the current limiting element 9 flashes outside the element or inside the element, and accordingly, a follow current arc flows in the discharge path. Since this follow-up arc naturally flows also in the discharge gearup G, the internal pressure of the insulator body near the pressure release plate 30 of the cap metal 3 rapidly rises, and this internal pressure causes the discharge part 30a to reverse and the pressure release plate due to arc heat. The upper portion of 30 and the discharge portion 30a are melted to form a pressure release port, and the pressure is safely released to the outside through the pressure release port 32a of the connecting fitting 32.

On the side of the base metal fitting 20, the internal pressure in the storage member 20d is released from the small hole 33a of the lid metal fitting 33. Therefore, the released pressure is released through the gap s previously formed between the bottom surface of the base metal fitting 20 and the arm 27.

FIG. 3 shows a third embodiment of the present invention. The third embodiment is a case of a so-called gear press structure in which the discharge gear (G) is omitted in the first embodiment, and compared with the first embodiment, the opening 3 of the storage member 3b is formed.
The lead-out electrode 12 led out from e
And the storage member 3b is greatly extended downward, and the current limiting element 9 is connected in series within the extended storage member 3b by increasing the number of the current limiting element 9 by one from the first embodiment. The difference is that they are stored in a state and the limit voltage value is increased accordingly. In addition, when a follow-up arc occurs, such as an external element accident (short circuit accident) due to deterioration, etc., the space 2 m
The increased internal pressure is rapidly released from the pressure release port 20p formed on the bottom surface 20b side of the cap 20 (or this part when the mechanical weak point is formed as in the above embodiment) to the outside of the cap 20. Reduces damage to the insulator.

Reference numeral s denotes a pressure release gap formed between the bottom surface 20b and the arm 27, and reference numeral 26 denotes a seal material provided as necessary to close the pressure release port 20p. Since the other structure is the same as that of the first embodiment, the same parts are designated by the same reference numerals and the description thereof will be omitted.

FIG. 4 shows a fourth embodiment of the present invention. The fourth embodiment is a case where the discharge gap (G) is not formed in the second embodiment, and the tip of the lead-out electrode 12 that is led out upward from the opening 20g of the housing member 20d on the base metal fitting 20 side. 12d is directly connected to the cap fitting 3, and the storage member 20d is greatly extended upward,
The difference is that the current limiting element 9 is accommodated in the extended housing member 20d in series connection by increasing the number of the current limiting element 9 by one, as compared with the second embodiment, and thereby increasing the limiting voltage value accordingly.

Further, the pressure release at the time of occurrence of the follow-up arc is performed by the lid fitting 3 fixed to the bottom end opening 20f of the bottom fitting 20 of the base fitting 20.
Pressure is released to the outside of the metal fitting through the pressure release port 33a formed in 3 (or the mechanical weak point if it is provided as described above) and the gap s. Opening 2
The pressure released from 0 g is released from the space 2h through the hole 20h. Reference numeral 26 indicates a seal material provided as necessary.

Since the other structure is the same as that of the second embodiment, the same reference numerals are given to the same portions and the description thereof will be omitted.

[0044]

According to the present invention having the above-mentioned constitution, by any chance,
Even if the current limiting element is short-circuited and the follow current arc flows due to deterioration, the current limiting element is prevented from being destroyed because it is inside the metal housing member having high mechanical strength. Of course, it becomes possible to prevent the insulator body from being damaged.

Further, in the case of an existing insulator having a space formed in the main body or having a space, the space is utilized and a metal storage member is arranged in the space to limit the current limiting element unit ( Since the current limiting element is incorporated, the shape of the entire insulator device is not so large and compact despite the fact that the protective device is incorporated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a geared type in a first embodiment of an insulator device with a built-in protective device of the present invention.

FIG. 2 is a cross-sectional view of a type with a gearup according to a second embodiment of an insulator device with a built-in protective device of the present invention.

FIG. 3 is a sectional view of a third embodiment of an insulator device with a built-in protection device of the present invention, which is an example in which the structure of the first embodiment is applied to a gear press type.

FIG. 4 is a cross-sectional view of a fourth embodiment of an insulator device with a built-in protection device of the present invention, which is an example in which the structure of the second embodiment is applied to a gear press type.

[Explanation of symbols]

 1 Insulator body device 2 with built-in protective device 2 Insulator body 2a Head 2m, 2n, 2h, 2i Space part 3 Cap metal fitting 3b Storage member 6 Clamp part 8 Current limiting element unit 9 Current limiting element 10 Charge side electrode (electrode) 11 Ground Side electrode 12 Derivation electrode 12b Tip 12d Tip 13 Discharge part 16 Insulation member 20 Base metal fitting 20b Storage member 24 Armband 36 Charge side electrode (electrode) 37 Ground side electrode G Discharge gap

Claims (2)

[Claims] 1. An upper space (2 m) and a lower space (2) inside the body.
n), an insulator body (2), a base metal member (20) for fixing the lower part of the insulator body (2) to a armrest (27), and an insulated wire (7) provided on the head of the insulator body (2). ), A cap metal fitting (3) electrically connected to the above), a metal storage member (36) stored in the upper space (2 m), and a current limiting element stored in the storage member (36). (9)
And a lead-out electrode (12) connected to one end of the current limiting element (9) and protruding into the lower space (2m), and outer peripheral surfaces of the current limiting element (9) and the lead-out electrode (12). A current limiting element unit (8) consisting of a coated insulating member (16) such as rubber, and an end portion of the current limiting element (9) opposite to the lead-out electrode (12) is provided with the cap fitting. (3) is electrically connected, and the protruding side tip of the lead-out electrode (12) is electrically connected to the base metal fitting (20) directly or through a discharge gap (G) of a predetermined length. Equipment with built-in protective device. 2. An upper space (2i) and a lower space (2) inside the body.
h) the insulator body (2), the base metal fitting (20) for fixing the lower part of the insulator body (2) to the armrest (27), and the insulated wire (7) provided on the head of the insulator body (2). ), A cap metal fitting (3) electrically connected to the housing, a metal housing member (20d) housed in the lower space (2h), and a current limiting element housed in the housing member (20d). (9)
A lead-out electrode (12) connected to one end of the current limiting element (9) and protruding into the upper space (2i); and outer peripheral surfaces of the current limiting element (9) and the lead-out electrode (12). A current limiting element unit (8) consisting of a coated rubber or other insulating member (16), and an end portion of the current limiting element (9) opposite to the lead-out electrode (12) is provided with the base metal fitting. (20) is electrically connected, and the protruding side tip of the lead-out electrode (12) is electrically connected to the cap fitting (3) directly or through a discharge gap (G) of a predetermined length. Insulator device with built-in protective device.