EP4618122A1

EP4618122A1 - On-load tap changer for use at sea

Info

Publication number: EP4618122A1
Application number: EP24162823.9A
Authority: EP
Inventors: Jean Louis Gérard Mathae; Thomas Eriksson; Daniel FORSMAN
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2024-03-12
Filing date: 2024-03-12
Publication date: 2025-09-17
Also published as: WO2025190967A1

Abstract

An on-load tap changer OLTC comprising a housing, with a housing body and an upper body attached to the housing body (2) is provided. At least a portion of the upper body is provided with a surface inclined in relation to a first axis (Z) and oriented such that water flowing along the inclined surface by the force of gravity overflows an edge portion of the inclined surface or is directed to a drain system of the OLTC.

Description

TECHNICAL FIELD

The present disclosure relates generally to on-load tap changers (OLTC). Specifically, the disclosure relates to an improved OLTC design for use in moving working conditions, such as at sea.

BACKGROUND

On-load tap changers are typically employed in static installations in land applications. When OLTCs are to be employed in moving applications, such as sea based applications, the OLTCs need to withstand high mechanical fatigue and mechanical stress associated with high accelerations in different directions caused by waves and wind. Further, the aggressive environment at sea is a further challenge. Especially, a top portion of an OLTC will be exposed when at sea. The OLTC top portion faces the environment, carry the complete weight of the OLTC itself, and the weight and the forces added by cleats and leads coming from the transformer core of the transformer it serves.
An OLTC comprises a housing formed by a housing body with opposite open ends, each end being closed by a respective lid attached to the housing body. The housing body may be made from a rigid material, such as a fiber-reinforced plastic material, or a metal. A major portion of the housing body is however made of an electrically insulating material. When the OLTC is exerted to accelerations, different portions of the OLTC tend to wear and the risk of failure increases.
For static installations this is usually not a problem, but when employing the OLTC at sea, new problems arise. Further, when employed in a sea based application, the OLTC is exposed to difficult conditions like heavy wind, and the presence of salt, sand, and high humidity, thus further challenging proper functionality of the OLTC over time.
Accordingly, it is an object of the present disclosure to increase longevity of an OLTC used at sea.

SUMMARY

According to a first aspect, this object is achieved by an on-load tap changer according to claim 1, with alternative embodiments defined in the dependent claims. The OLTC comprises an upper body. At least a portion of the upper body is provided with surfaces inclined in relation to a first axis and oriented such that, when said first axis is vertically oriented, water flowing along the inclined surface by the force of gravity overflows an edge portion of the inclined surface or is directed to a drain system of the OLTC. The first axis is typically vertically oriented when the OLTC is in use but of course, is orientation varies over time due to motion by wind and waves. The inclined surfaces of the upper body enable gravity to force water, such as rainwater or sea water, to flow off the OLTC, either over the edge of the OLTC or towards conduits of a drain system of the OLTC. The drain system may for example connect one or more pockets of the upper body to drain conduits, leading water from the pockets through the OLTC and off the OLTC through one or more drain outlets. Typically, one tries to achieve a design without pockets.
A portion of the upper body may be provided with a slanted profile. A top portion of the upper body may alternatively be provided with a curved profile. At least a portion of the upper body may be provided with a curved profile.
In embodiments, the top portion of the upper body may be provided with a curved profile. In other embodiments, the top portion of the upper body may be provided with a spherical shape. In still other embodiments, the top portion of the upper body may be provided with a conical profile.
In embodiments, the upper body may comprise a lid configured to cover an open end of the housing body. In embodiments, at least a portion of the upper body may be provided with surfaces inclined in relation to the first axis.
In other embodiments, at least a portion of the periphery of the upper portion may be provided with a flange. The flange may be extending around substantially the whole periphery of the upper portion, and at least a portion of the flange may be inclined in relation to the first axis and oriented such that, when said first axis is vertically oriented, water flowing along the flange by the force of gravity overflows an edge portion of the flange or is directed to a drain system of the OLTC.
In embodiments, at least a portion of the on-load tap changer OLTC may be provided in stainless steel. In embodiments, the upper body may be provided in stainless steel. The lid may in embodiments be provided in stainless steel. In embodiments, the housing body may be provided in stainless steel. The upper portion may at least in portion is provided in stainless steel. The upper body may be provided in stainless steel, and/or the housing body may be provided in stainless steel.
In embodiments, the stainless steel may be of a steel quality with a pitting resistance equivalent number (PREN) equal to or above 40.

BRIEF DESCRIPTION OF DRAWINGS

All figures show schematic views not drawn to measure.

Fig. 1 shows an embodiment of an upper portion of an on-load tap changer.
Fig. 2 is a side view of an embodiment of an upper portion of an on-load tap changer.
Fig. 3 is an overview of an on-load tap changer according to embodiments herein.
Fig. 4 is a side view of an embodiment of an upper portion of an on-load tap changer similar to the embodiment shown in fig. 2, but further provided with a top recess forming a pocket, said pocket being connected to a drain system of the OLTC. The drain system comprises a fluid conduit adapted to enable water to flow from a bottom of the pocket to a drain outlet of the drain system.

DETAILED DESCRIPTION

Embodiments of the disclosure will hereinafter be described with reference to the appended drawings.
Fig. 1 shows an embodiment of an example of an upper portion of an on-load tap changer (OLTC) according to embodiments herein. The on-load tap changer 1 comprises a housing (not shown in Fig. 1). The housing comprises a housing body 2 and an upper body 3 attached to the housing body 2. At least a portion of the upper body 3 is provided with surfaces inclined in relation to a first axis Z. As an example, a portion of the upper body 3 may be provided with a slanted profile. The top portion 5 of the upper body 3 may alternatively be provided with a curved profile.
Thanks to the portions provided with such surfaces or profiles, moisture and water present on the upper body 3 will stream off, or drip off, from the upper body 3, thus enabling surfaces exposed to water to dry faster. Further, connections details 7 are also provided with slanted or curved upper surfaces, enabling water and moisture to drip off. When in use at sea, the tap changer is not only exposed to rain, but sea water may spray on the tap changer in heavy wind. Thus, if the upper portions more easily may be dried off, an OLTC with longer lifetime when exposed to the sea is provided.
Further, in the environment at sea, not only the salt water is salt but also any fog present as well as the rain. Corrosive elements, like salt, are present in the sea water, and the tap changer may due to the curved or slanted profile of the upper body 3 be exposed to such corrosive elements during a shorter period of time compared to a traditional tap changer where the upper portion is more or less flat and water and moisture tend to be present during a long time.
The top portion 5 of the upper body 3 may be provided with a spherical profile as shown in Fig. 2 which is a side view of an exemplified upper portion 5 of an on-load tap changer OLTC 1. The top portion of the upper body 3 may alternatively be provided with a conical profile.
The upper body 3 may comprise a lid configured to cover an open end of the housing body 2. As may be seen in several of the drawings, the periphery of the upper body 3 as a whole, or a portion thereof, may be provided with a flange 4. The whole or a portion of the flange 4 may be inclined in relation to the first axis Z. The flange 4 may alternatively be provided with slanted or curved surfaces, or portions of surfaces, enabling water and moisture to drip off. In the exemplified embodiment shown in the drawings, the flange 4 is extending around substantially the whole periphery of the upper body 3. The transition area 6 between the flange 4 and other portions is rounded providing a smooth transition preventing water from being trapped. Further, the upper surface of the flange 4 is inclined in relation to the first axis Z. Thereby, water and moisture is more easily transported away from the flange 4.
The upper portion may at least in portion be provided in stainless steel. Stainless steel is a superior material when it comes to withstand exposure to aggressive environment like present in sea applications. The lid or other small or large portions or details may be provided in stainless steel. The upper body 3 may be provided in stainless steel and/or the housing body 2 may be provided in stainless steel. The stainless steel used may be of a steel quality with a pitting resistance equivalent number (PREN) equal to or above 40.
It should be understood that the disclosure is not limited to the specific combination of features disclosed herein and illustrated in the examples of the appended figures.

Claims

An on-load tap changer (1) comprising an upper body (3), wherein at least a portion of the upper body (3) is provided with an inclined surface in relation to a first axis (Z) and oriented such that, when said first axis is vertically oriented, water flowing along the inclined surface by the force of gravity overflows an edge portion of the inclined surface or is directed to a drain system of the on-load tap changer (1).
An on-load tap changer (1) according to claim 1, wherein at least a portion of the upper body (3) is provided with a slanted profile.
An on-load tap changer (1) according to any one of claims 1 or 2, wherein at least a portion of the upper body (3) is provided with a curved profile.
An on-load tap changer (1) according to any one of the preceding claims, wherein a top portion (5) of the upper body (3) is provided with a curved profile.
An on-load tap changer (1) according to any one of claims 3 or 4, wherein the top portion (5) of the upper body (3) is provided with a spherical shape.
An on-load tap changer (1) according to any one of claims 3 or 4, wherein the top portion (5) of the upper body (3) is provided with a conical profile.
An on-load tap changer (1) according to any one of the preceding claims, wherein at least a portion of a periphery of the upper body (3) is provided with a flange (4).
An on-load tap changer (1) according to any one of the preceding claims, wherein said flange (4) is extending around substantially the whole periphery of the upper portion.
An on-load tap changer (1) according to any one of claims 7 or 8, wherein at least a portion of said flange (4) is inclined in relation to the first axis (Z) and oriented such that, when said first axis is vertically oriented, water flowing along the flange (4) by the force of gravity overflows an edge portion of the flange (4) or is directed to a drain system of the on-load tap changer (1).
An on-load tap changer OLTC (1) according to any one of the preceding claims, wherein the upper body (3) comprises or forms a lid configured to cover an open end of the housing body (2).
An on-load tap changer OLTC (1) according to any one of the preceding claims, wherein the lid is made of stainless steel.
An on-load tap changer OLTC (1) according to any one of the preceding claims, wherein the upper body (3) is made of stainless steel.
An on-load tap changer OLTC (1) according to any of the preceding claims, wherein the housing body (2) is made of stainless steel.
An on-load tap changer OLTC (1) according to any one of claims 11 - 13, wherein the stainless steel is of a steel quality with a pitting resistance equivalent number (PREN) equal to or above 40.