RU2797986C1 - Device for protecting rod polymer insulators from damage by partial surface discharges when the contaminated surface is moistened - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: rod polymer insulators of power lines and electrical apparatus, mainly medium and higher voltage classes.

The technical result is achieved through the use of a device for protecting rod polymer insulators from damage by partial surface discharges when the contaminated surface is moistened. The protection device is a removable electrode, which makes it possible to replace it, made in the form of two open rings lying in parallel and interconnected by a jumper. The ring of smaller diameter provides the possibility of fixing the device on the flange-terminator of the insulator close to the zone of contact between the flange and the insulating coating, and the ring of larger diameter - at the top of the expanded part of the insulating coating located above the flange protrusion.

EFFECT: increase of the reliability and durability of the rod polymer insulators.

1 cl, 3 dwg

Description

The invention relates to electrical engineering, in particular to rod polymer insulators for power lines and electrical apparatus, mainly medium and higher voltage classes.

The purpose of the proposed invention is to increase the service life and operational reliability of rod polymer insulators in difficult operating conditions, namely, in conditions of moistening of a contaminated surface at operating voltage, simplify the design, reduce metal consumption, and improve their manufacturing technology.

As you know, an outdoor insulator of medium and higher voltage classes operates in conditions of natural pollution and moisture. At the same time, in addition to variable mechanical impacts, the insulator is also affected by electrical (long-term nominal and short-term increased) loads under normal, sometimes extreme operating conditions, for example, salt marshes, tropical and subtropical climates, high humidity, etc. It is clear that the formation of an intermittent low-current arc on the surface of an insulator under conditions of moistening of its contaminated surface at operating voltage is inevitable. At the same time, the moistened surface heated by a low-power arc quickly dries up. As a result, the dried annular zone expands, which leads to an elongation of the arc, causing a further decrease in current and an increase in electrical resistance, which also causes a decrease in current. The heat release on the surface of the insulator decreases, the surface is moistened again, the current is restored through it, and the arc goes out. This mode of an intermittent low-current arc is normal for the operation of any external insulation in electrical networks and is observed when the operating voltage of industrial frequency is applied.

In the intermittent arc mode, the temperature in its channel reaches 4000°C and higher. In this case, one reference point of the arc, mainly on the surface of the metal electrode, remains stationary, as a result of which the metal is heated and, accordingly, the high-strength fiberglass rod is heated in the zone of its contact with the metal. Already when the temperature reaches 100-120°C on the body of the fiberglass rod, its mechanical stress state is weakened (relaxation process), the rod begins to crawl out of the flange, depressurization and destruction of the insulator. In particularly difficult operating conditions, the resulting high temperature contributes to the melting of the metal at its border with an insulating coating. This leads to the destruction of the flange, the fall of the phase wire to the ground with serious consequences. In this case, the second reference point of the arc moves on the surface of the insulating coating near the flange, destroying the insulation (thermo-oxidative process) in the form of a track (carbonization) or erosion (without soot release).

It should be noted that the destruction of the insulator occurs at the operating (nominal) voltage in the conditions of natural moistening of the contaminated surface. The dimensions of the specified low-current arc vary within 8-15 mm. Full overlap of the insulator under the above conditions usually does not occur.

An illustration of the destruction of the surface of the flange-terminator (hereinafter referred to as the flange), at the flange-silicone coating interface of existing standard polymer insulators, is shown in Fig. 1b (zone "K"). And in Fig. 1c and 1d show photographs of the melting of the insulator flanges: 1c - the flange is located under the insulating coating, 1d - the flange is above the coating.

Known rod polymer insulator [1], consisting of a high-strength fiberglass rod (profile) with tracking and weather-resistant silicone ribbed coating, reinforced at the ends with metal tips (flanges). Crimping flanges on the surface of the profile is carried out on a special machine under a certain force. On suspension/tension polymeric insulators, the flange-to-profile connection unit provides mechanical tensile strength of the structure, while the ribbed coating provides protection of the profile surface from atmospheric influences. The silicone coating on the profile, and partially on the flanges, is molded using a special injection machine in a suitable mold, where high-temperature vulcanization is carried out at the same time. The insulator is also equipped with screen and arc-removing fittings. Screen fittings in the form of a toroid are mounted on the surface of the metal flange of the insulator and serve to distribute the electric field strength in the absence of moistening of the contaminated surface and at the same time divert the short circuit arc to a safe distance from the surface of the insulator in case of overvoltages. Arc diverting fittings in the form of horns serve to divert the short circuit arc to a safe distance from the surface of the insulator.

The disadvantages of this design of the insulator. The combined screen/arc fittings fixed on the specified insulators cannot protect the junction of the fiberglass rod with metal flanges from heating and melting of the flanges due to the effect of surface partial arc discharges when the contaminated surface is moistened under operating voltage due to the small size of the specified arc (up to 15 mm ). The distance from the source of formation of a low-current arc (zone "K" in Fig. 1b) with a high temperature (the boundary between the insulating coating and the metal flange) to the screen/arc ring is at least 100-150 mm (not shown in Fig. 1), which is inaccessible for a low-current arc with a maximum size of up to 15 mm.

It should also be noted that the insulating coating of the flange surface, on the one hand, protects the joint from moisture ingress into the internal cavity of the structure, on the other hand, increases the concentration of the electric field strength at the insulation-metal interface, contributes to even faster heating and melting of the flange.

As can be seen in [1], the insulator does not provide protection against heating, flashing of the flange and destruction of the insulation in the vicinity of the flange space from a low-current partial discharge arc when its contaminated surface is moistened.

The problem identified by the authors was partially solved in [2] by installing a high-voltage rod insulator of a small toroidal disk on the reinforcement node. This disc contributes to the sealing of the junction of a high-strength insulating rod with a metal flange and, along with screen reinforcement, also contributes to an even greater decrease in the electric field strength along the axis of the high-voltage insulator to a safe level in dry weather.

The disadvantages of this design are the following factors:

- the source of high temperature is located directly on the contacting parts of the silicone-coated flange at a distance of no more than 2.5-3 mm from the high-strength fiberglass rod (the thickness of the silicone coating at the flange), which is the worst option for reliable operation of the insulator;

- non-removable small toroidal disk makes it impossible to replace it if damaged.

The purpose of the present invention is to eliminate the above disadvantages, namely, the removal of the heat source to the maximum safe distance and the possibility of replacing the specified protective agent if it is damaged.

The essence of the invention lies in the fact that the device for protecting rod polymer insulators from damage by partial surface discharges when a contaminated surface is moistened, is a removable electrode that makes it possible to replace it, made in the form of two open rings lying in parallel planes and interconnected at least at least one jumper, while the small ring provides the possibility of fixing the device on the flange-terminator of the insulator, close to the zone of contact between the flange and the insulating coating, and the large ring - on the top of the expanded part of the insulating coating located above the flange protrusion.

Thus, the technical result is achieved - increasing the reliability and durability of the rod polymer suspension / tension insulators of predominantly medium and higher voltage classes in difficult operating conditions, reducing the metal consumption of protective reinforcement, simplifying the design of insulators.

The drawings accompanying the description show:

Fig. 1a - rod polymer suspension / tension insulator of power transmission lines;

Fig. 1b - zone "K" - the place of melting of the metal flange at the border of the flange-insulating coating with alternating low-current arcs in the conditions of moistening the contaminated surface at operating voltage;

Fig. 1c - photograph of the thermal destruction of the flange located under the silicone coating;

Fig. 1d is a photo of the thermal destruction of the flange located above the silicone coating;

Fig. 2 - Design of a device for protecting rod polymer insulators from damage by partial surface discharges when a contaminated surface is moistened by diverting a high-temperature low-current arc from the surface of the insulator flange to a safe distance. The device is a removable electrode made in the form of two open rings interconnected by a jumper (hereinafter referred to as the removable electrode). In FIG. 2a and 2b show possible versions of removable electrodes.

Fig. 3 - An example of installing two types of removable electrodes (Fig. 3b and 3c) on the surface of the suspension / tension insulator of a power transmission line (Fig. 3a) and the transition of the reference point of the arc from the flange surface (see Fig. 1b, zone "K") to the top of the ring (Fig. 3d, zone "K").

The following symbols are used in the drawings:

1 - high-strength fiberglass rod;

2 - metal flange-terminator;

3 - tracking and weatherproof silicone coating;

4 - removable electrode.

In zone "K" there is a reference point of a high-temperature low-current arc.

d is the outer diameter of the flange;

D is the outer diameter of the expanded part of the silicone coating lying above the flange ledge;

d1 - inner diameter of the small ring of the removable electrode;

d2 is the diameter of the wire from which the removable electrode is made;

D1 - inner diameter of the large ring of the removable electrode;

h is the height of the removable electrode.

The rod polymer insulator (Figs. 1a, 3a) consists of a high-strength fiberglass rod 1, reinforced at the ends with metal flanges 2 and coated with tracking and weather-resistant silicone composite 3. The high-strength insulating fiberglass rod 1 serves to suspend the conductor on a power transmission line support. Metal flanges 2 are used as end fittings for high-strength fiberglass rod 1. The outer silicone shell 3 is used to protect high-strength fiberglass rod 1 from atmospheric influences, and in the reinforcement zone - to seal the junction of flanges 2 with high-strength fiberglass rod 1, weather protection , reduction of mechanical stresses under bending loads.

In the claimed technical solution, the specified insulator is provided with additional devices for protecting rod polymer insulators from damage by partial surface discharges when moistening a contaminated surface, which are removable electrodes 4 (Fig. 2), providing the possibility of their replacement in case of thermal damage. Removable electrodes 4 are used to divert the high-temperature arc to a safe distance, to reduce the electric field strength along the axis of the insulator.

Removable electrodes 4 are made in the form of two open rings lying in parallel planes and interconnected by at least one jumper. These rings can have different sizes, with the inner diameter of the small ring is indicated as d1, and the inner diameter of the large ring is D1. Removable electrode height - h.

The flange 2 of the insulator, having an outer diameter d, includes a protrusion covered with a silicone coating 3. The outer diameter of the expanded part of the silicone coating 3 lying above the protrusion of the flange 2 is designated as D.

The height h of the removable electrode 4 is determined by the distance along the axis of the insulator from the top of the expanded part of the silicone coating 3 to the boundary where this coating ends (Fig. 3).

Removable electrode 4 is fixed on the insulator so that the large ring is located near the top of the expanded part of the silicone coating 3 (a slight indentation is allowed from the flange 2), and the small ring is on the flange 2, close to the zone of contact between the flange and the insulating coating, while D and D1 can be equal, and d1 must meet the following relationship to ensure reliable fixation:

d1 = (0.90 ... 0.95) d

Removable electrode 4 can be made of elastic metal, for example, steel wire, the diameter of which is indicated as d2 (Fig. 2). Thus, due to the elasticity of the metal, a reliable electrical contact is provided between the removable electrode 4 and the flange 2.

The installation of the described electrodes 4 on the insulator facilitates the removal of a high-temperature arc that occurs when the contaminated surface is moistened under operating voltage from the surface of the flange 2 (Fig. 1b, zone "K") to the top of the large ring of electrode 4 (Fig. 3d, zone "K") .

In FIG. 2. 2 versions of the removable electrode 4 are presented to prevent the melting of metal flanges 2 at the flange-insulating coating boundary by alternating low-current arcs under conditions of moistening the contaminated surface at operating voltage: fig. 2a - single large ring; fig. 2b - double large ring. Other versions of the electrodes are also possible, realizing the claimed technical result. Removable electrodes 4 can be made, for example, from an elastic wire with a diameter of d2=3-4 mm.

The installation of the detachable electrode 4 proposed by us on the flanges 2 of polymer suspension/tension insulators reliably protects the surface of the flange 2 from heating by small-sized intermittent arcs at the metal-insulation boundary when its contaminated surface is moistened at operating voltage. The inevitable arc with its fixed base will heat and melt not the flanges 2 of the insulator, but the large ring of the removable electrode 4, while the electrode 4, if necessary, can be easily replaced with a new one.

Analogues:

1. 3FL Silicone Long Rod Insulators for Distribution and Transmission overhead Power Lines. Light white-strong performance.

2. Catalog 24 Insulators / KyungRuang Lee - Academia.edu, https://www.academia.edu/38602069/Catalog_24_İnsulators.

Claims (1)

A device for protecting rod polymer insulators from damage by partial surface discharges when a contaminated surface is moistened, which is a removable electrode that makes it possible to replace it, made in the form of two open rings lying in parallel planes and interconnected by at least one jumper, while the ring of a smaller diameter provides the possibility of fixing the device on the flange-end of the insulator close to the zone of contact between the flange and the insulating coating, and of a larger diameter - at the top of the expanded part of the insulating coating located above the flange protrusion.

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