EP4075466A1

EP4075466A1 - Generator circuit breaker, gcb

Info

Publication number: EP4075466A1
Application number: EP21168247.1A
Authority: EP
Inventors: Francesco Agostini; Peter Frei
Original assignee: Hitachi Energy Switzerland AG
Current assignee: Hitachi Energy Ltd
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2022-10-19

Abstract

The invention relates to a generator circuit breaker, GCB, , comprising an interrupting chamber (1) and an infrared heater (2) configured for emitting infrared radiation, whereby the interrupting chamber (1) comprises a base (3) for mounting the interrupting chamber (1) on a support structure (4), a fixed contact housing (8) comprising arranged therein a fixed contact, a moving contact housing (6) comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator (7) arranged between the fixed contact housing (8) and the moving contact housing (6), and a ground insulator (5) arranged between the base (3) and the moving contact housing (6), and the infrared heater (2) is configured for emitting the infrared radiation onto the fixed contact housing (8), onto the moving contact housing (6), and/or onto the base (3).

Description

Technical Field

The invention relates to a generator circuit breaker, GCB, comprising an interrupting chamber having a base for mounting the interrupting chamber on a support structure, a fixed contact housing comprising arranged therein a fixed contact, a moving contact housing comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator arranged between the fixed contact housing and the moving contact housing, and a ground insulator arranged between the base and the moving contact housing. The invention also relates to a method for heating an interrupting chamber of a generator circuit breaker, GCB, whereby the interrupting chamber comprises a base for mounting the interrupting chamber on a support structure, a fixed contact housing comprising arranged therein a fixed contact, a moving contact housing comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator arranged between the fixed contact housing and the moving contact housing, and a ground insulator arranged between the base and the moving contact housing.

Background Art

Operation at low temperature represents a challenge in the design of generator circuit breakers, GCBs. Specifically, according to standards IEC 62271-100:2017 and IEC/IEEE 62271-37-013:2015, clause 6.101.3 "Low and high temperature tests", the generator circuit breaker is requested to operate at a minimum temperature after at least a two-hour shut down of a respective cooling system. If temperature is too low, switching fluid inside an interrupting chamber of the GCB changes from a gaseous to a liquid state, which causes a reduction of switching fluid insulating properties required for proper operation of the GCB. To avoid this, heating is applied to the interrupting chamber at very low ambient temperatures. Standard cartridge heater heating represents the common, state-of-the-art solution for heating GCBs, however, may not guarantee compliance to the standards at very harsh environment conditions.

Summary of invention

It is therefore an object of the invention to provide an alternative solution with improved design flexibility to operate a GCB at low ambient temperatures, in particular for better avoiding such switching fluid liquefaction.
The object of the invention is solved by the features of the independent claims. Modified implementations are detailed in the dependent claims.
Thus, the object is solved by a generator circuit breaker, GCB, in particular for connecting a generator to a step-up transformer, comprising an interrupting chamber and an infrared heater configured for emitting infrared radiation, whereby

the interrupting chamber comprises a base for mounting the interrupting chamber on a support structure, a fixed contact housing comprising arranged therein a fixed contact, a moving contact housing comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator arranged between the fixed contact housing and the moving contact housing, and a ground insulator arranged between the base and the moving contact housing, and
the infrared heater is configured for emitting the infrared radiation onto the fixed contact housing, onto the moving contact housing, and/or onto the base.

A key point of the proposed solution is therefore that at least one part of the interrupting chamber such as the fixed contact housing, the moving contact housing, and/or the base is heated by infrared radiation to guarantee a gaseous condition of a switching fluid inside the interrupting chamber at any environmental condition. Such way an even more uniform temperature distribution across the interrupting chamber is reached, therefore avoiding possible local switching fluid liquefaction due to low local temperatures and material stress due to high local temperatures. It thus becomes possible to operate the GCB at extremely harsh environmental conditions, such as for example below -40°C or even -50 °C. Further, the proposed solution reduces thermal stresses across insulating parts such as the chamber insulator and/or the horizontal ground insulator Even further, using the proposed infrared heater, possibly in addition to cartridge heaters, provides an increased flexibility in heating capabilities and such a wide applicability to different geometries and operating conditions, as it becomes possible to apply heat to parts on potential without having galvanic connections. In sum, the proposed solution is compliant with standards such as for example IEC 62271-100 2017 and IEC/IEEE 62271-37-013 2015, clause 6.101.3 "Low and high temperature tests" , allowing the generator circuit breaker to operate at a minimum temperature after at least a two-hour shut down of a respective cooling system.
Using infrared heaters instead or in addition to cartridge heaters allow irradiating parts of the interrupting chamber which are on high voltage potential during operation of the GCB, as the heat is contactless applied onto the fixed contact housing, onto the moving contact housing, and/or onto the base. Thereby the design limitation of cartridge heaters to few parts of the chamber that are on ground potential becomes void. Further, even that the insulators separating different electrical potentials of the interrupting chamber have low thermal conductivity, heat emitted by the infrared heaters can be spread effectively to main parts of the interrupting chamber such as the fixed contact housing, the moving contact housing, and/or the base.
The GCB, in particular parts of the GCB such as the base, the fixed contact housing, the fixed contact, the moving contact housing, the moving contact, the chamber insulator and/or the ground insulator, can be provided as any GCB known from prior art and are thus not discussed in detail as known to the person skilled in the art. The GCB may thus comprise additional parts such as a drive, an enclosure, earthing switches, surge capacitors, current transformers, voltage transformers, surge arresters, and more, which are not described in the present application but known to the person skilled in the art. The support structure can be ground.
Generally, generator circuit breakers are power plant devices located between the generator, which typically produces electricity at a voltage of around 15-30 kV, and the step-up transformer, which typically increases this voltage up to the grid transmission voltage, for example 200 kV to 800 kV. GCBs play a key role in the protection of the transformer and the generator in case of fault, such as a short circuit on the power transmission system, while their major function in normal operation is to connect and disconnect the generator to and from the grid with high availability and reliability, by means of moving the moving contact in respect to the fixed contact. GCBs typically fulfill generator ratings ranging from 50 MVA to 1,400 MVA, short circuit ratings from 63 kA to 300 kA and nominal currents from 6,300 A to over 50,000. Conventionally, sulphur hexafluoride (SF6) has been used as an insulation medium or quenching gas, respectively, also referred to as switching fluid. SF6 is known for its high dielectric strength and thermal interruption capability and thus typically provided in the preferably closed interrupting chamber defined by the fixed contact housing and the moving contact housing
The infrared heater emits the infrared heating radiation by means of electromagnetic radiation, whereby a wavelength of a peak of the infrared radiation can range from 780 nm to 1 mm. The infrared heater may comprise tungsten as filament material, which is preferably coiled to increase surface area. Besides tungsten carbon, alloys of iron, chromium, and aluminum can be used. The infrared heater is preferably arranged distant but close to the fixed contact housing, thereby not touching the fixed contact housing, for fulfilling dielectric requirements when heating the fixed contact housing being under voltage. The distance may be 10cm, 20cm, 40cm, 50cm or 1m, or in a range of these figures. For example, the infrared heater can be attached to ground and/or configured for only emitting the infrared heating radiation onto the fixed contact housing and/or only on the fixed contact housing and also on the moving contact housing. Further, a plurality of heaters may be present, for example arranged radially around the fixed contact housing.
The infrared heater may consume 250W, 500W or 1000W, and thereby configured for heating the switching fluid present in the interrupting chamber so to remain in gaseous state. Emitting infrared heating radiation onto the target parts means that preferably all or the majority of the infrared heating radiation is emitted in direction respectively onto the fixed contact housing, onto the moving contact housing, and/or onto the base. The fixed contact housing and/or the moving contact housing, when connected together via the chamber insulator, preferably form a cylinder, a tube and/or ring-like tube with front side surfaces as terminals for the fixed contact and moving contact and lateral surfaces between the front side surfaces. The infrared heater is preferably arranged and/or configured to emit the infrared heating radiation on the lateral surface, onto the bottom side, onto the top side and/or onto the front side and possibly also in addition partly on the front side surface of the fixed contact housing.
According to a preferred implementation, the GCB comprises a cartridge heater configured for heating the interrupting chamber and in particular at the base. The cartridge heater is preferably provided as a tube-shaped Joule heating element that is inserted and/or attached to the base. Preferably both the infrared heater and the cartridge heater are used together for heating the switching fluid.
According to a further preferred implementation, the GCB comprises an uninterruptible power supply, UPS, configured for providing electrical energy to at least the infrared heater. The UPS in particular allows for starting and/or continuous operation of the infrared heater at low temperature in absence of regular electrical power. Preferably, both the infrared heater and the cartridge heater are supplied by the UPS for at least one, two or four hours. In this respect, according to another preferred implementation, the UPS comprises an energy storage configured for providing electrical energy to at least the infrared heater for at least one, two or four hours. The energy storage can be provided as battery and/or as capacitor.
Generally, the proposed solution comprises that the infrared heater emits the infrared radiation on the fixed contact housing. According to a preferred implementation, the infrared heater is configured for emitting the infrared heating radiation onto the interrupting chamber, in particular onto a lateral side, onto a bottom side, onto a top side and/or onto a front side of the interrupting chamber. Therefore, the infrared heater can be arranged beneath or at least partly beneath the fixed contact housing. More preferably the infrared heater is arranged underneath the lateral surface of the fixed contact housing emitting the infrared heating radiation onto the lateral surface, and in addition preferably at least partly on the front side surface.
According to a preferred implementation, the GCB comprises three interrupting chambers with respective infrared heaters as described before.
The object is even further solved by a method for heating an interrupting chamber of a generator circuit breaker, GCB, in particular for connecting a generator to a step-up transformer, whereby
the interrupting chamber comprises a base for mounting the interrupting chamber on a support structure, a fixed contact housing comprising arranged therein a fixed contact, a moving contact housing comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator arranged between the fixed contact housing and the moving contact housing, and a ground insulator arranged between the base and the fixed contact housing, and comprising the step of:
Emitting infrared radiation onto the fixed contact housing, onto the moving contact housing, and/or onto the base by an infrared heater.
In a preferred implementation, the method comprises the step of:
Heating the interrupting chamber in particular at the base by a cartridge heater.
In another preferred implementation the method comprises the step of:
Providing electrical energy to at least the infrared heater by an uninterruptible power supply, UPS.
According to a further preferred implementation, the UPS comprises an energy storage configured for providing electrical energy to at least the infrared heater for at least two hours.
In another preferred implementation the method comprises the step of:
Emitting infrared radiation onto a lateral side, a bottom side, onto a top side and/or onto a front side of the interrupting chamber by the infrared heater.
According to a further preferred implementation, the method comprises three interrupting chambers with infrared heaters
In another preferred implementation, the method comprises the steps of:

Measuring a temperature of a part of the interrupting chamber, of a switching fluid inside the fixed contact housing and/or inside the moving contact housing, and
Controlling the emitting infrared heating radiation based on the measured temperature for reaching a target temperature.

With such implementation the temperature respectively state of the switching fluid inside the fixed contact housing and/or the moving contact housing can be controlled, for ensuring that the switching fluid remains in the gaseous state. For example, if the temperature decreases below a threshold, more infrared radiation can be applied onto the interrupting chamber parts.
Further implementations and advantages of the method are directly and unambiguously derivable by the person skilled in the art from the GCB as described before.

Brief description of the drawings

These and other aspects of the invention will be apparent from and elucidated with reference to the implementations described hereinafter.
In the drawings:
Fig. 1 shows in a sectional view an interrupting chamber of a generator circuit breaker, GCB, according to an exemplary implementation.

Detailed Description of exemplary implementations

Fig. 1 shows in a sectional view an interrupting chamber 9 of a generator circuit breaker, GCB, 1 for connecting a generator to a step-up transformer, not shown, according to an exemplary implementation.
The GCB 1 comprises an interrupting chamber 9 and an infrared heater 2. While Fig. 1 shows only one interrupting chamber 9, the GCB 1 comprises three interrupting chambers 9 with respective infrared heaters 2. The interrupting chamber 9 comprises a base 3, which is installed on a support structure 4 such as for example ground for mounting the interrupting chamber 9 via the base 3 thereon. On top of the base 3 a horizontally extending ground insulator 5 is provided, which is arranged between the base 3 and a 'L-shaped' moving contact housing 6. In another not depicted implementation the moving contact housing 6 can be straight and thus not 'L-shaped'. A vertically extending vertical chamber insulator 7 is attached to the other end of the moving contact housing 6 thereby connecting to a fixed contact housing 8.
A fixed contact, not shown, is arranged in the fixed contact housing 8, while a moving contact, not shown, for contacting the fixed contact is arranged in the moving contact housing 6. Together the fixed contact housing 8 and the moving contact housing 6 define a cylinder respectively tube-like interrupting chamber 9 of the GCB 1, as known from prior art, whereby both ring-like ground insulator 5 and chamber insulator 7 separate different electrical potentials of the interrupting chamber 9. Both the fixed contact housing 8 and the moving contact housing 6 are made of Aluminium and have respective electrodes on the lateral surface areas connecting to the inner fixed contact and moving contact.
The infrared heater 2 emits electromagnetic infrared heating radiation directed onto a bottom side of the fixed contact housing 8 facing ground 4, as can be seen from Fig. 1. With a given heating energy of for example 500W, the switching fluid such as SF6 gas (depicted as particles) 10 in the interrupting chamber remains in a gaseous state and does not liquefy, even at low ambient temperatures such as for example -45°C. Optionally in addition, a cartridge heater 11 can be present, for additional heating, arranged at the base 3.
The GCB arrangement further comprises an uninterruptible power supply, UPS, 13, which is connected to both the infrared heater 2 and the cartridge heater 11 for supplying electrical energy in case of a power loss. The UPS 13 thereby acts as auxiliary power source for the infrared heater 2 and the cartridge heater 11 for minimum of two hours operation. The UPS 13 comprises a respective battery dimensioned accordingly. Within the interrupting chamber 9 a temperature can be measured of a part of the interrupting chamber 9 and/or of the switching fluid 10 and heating radiation, of the infrared heater 2 and/or the cartridge heater 11, can be adjusted accordingly for reaching a desired target temperature such that the switching fluid 10 remains gaseous.
In a further exemplary implementation, not shown, an arrangement comprises three, four or more interrupting chambers 9, in particular one for each phase, with respective infrared heaters 2.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed implementations. Other variations to be disclosed implementations can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

Reference signs list

1: generator circuit breaker, GCB
2: infrared heater
3: base
4: support structure
5: ground insulator
6: moving contact housing
7: chamber insulator
8: fixed contact housing
9: interrupting chamber
10: switching fluid
11: cartridge heater
13: uninterruptible power supply, UPS

Claims

Generator circuit breaker, GCB, (1) comprising an interrupting chamber (9) and an infrared heater (2) configured for emitting infrared radiation, whereby
the interrupting chamber (9) comprises a base (3) for mounting the interrupting chamber (1) on a support structure (4), a fixed contact housing (8) comprising arranged therein a fixed contact, a moving contact housing (6) comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator (7) arranged between the fixed contact housing (8) and the moving contact housing (6), and a ground insulator (5) arranged between the base (3) and the moving contact housing (6), and

the infrared heater (2) is configured for emitting the infrared radiation onto the fixed contact housing (8), onto the moving contact housing (6), and/or onto the base (3).
The GCB (1) according to the previous claim, comprising a cartridge heater (11) configured for heating the interrupting chamber (9) and in particular at the base (3).
The GCB (1) according to any of the previous claims, comprising an uninterruptible power supply, UPS, (13) configured for providing electrical energy to at least the infrared heater (2).
The GCB (1) according to the previous claim, whereby the UPS (13) comprises an energy storage configured for providing electrical energy to at least the infrared heater (2) for at least two hours.
The GCB (1) according to any of the previous claims, whereby the infrared heater (2) is configured for emitting the infrared radiation onto a lateral side, onto a bottom side, onto a top side and/or onto a front side of the interrupting chamber (9).
The GCB (1) according to any of the previous claims, comprising three interrupting chambers (9) with respective the infrared heaters (2).
Method for heating an interrupting chamber (9) of a generator circuit breaker, GCB, (1), whereby
the interrupting chamber (9) comprises a base (3) for mounting the interrupting chamber (9) on a support structure (4), a fixed contact housing (8) comprising arranged therein a fixed contact, a moving contact housing (6) comprising arranged therein a moving contact for contacting the fixed contact, a chamber insulator (7) arranged between the fixed contact housing (8) and the moving contact housing (6), and a ground insulator (5) arranged between the base (3) and the moving contact housing (6), and comprising the step of:
Emitting infrared radiation onto the fixed contact housing (8), onto the moving contact housing (6), and/or onto the base (3) by an infrared heater (2).
The method according to the previous method claim, comprising the step of:
Heating the base (3) by a cartridge heater (11).
The method according to any of the previous method claims, comprising the step of:
Providing electrical energy to at least the infrared heater (2) by an uninterruptible power supply, UPS (13).
The method according to the previous method claim, whereby the UPS (13) comprises an energy storage configured for providing electrical energy to at least the infrared heater (2) for at least two hours.
The method according to any of the previous method claims, comprising the step of:
Emitting infrared radiation onto the interrupting chamber (9), in particular onto a lateral side, onto a bottom side, onto a top side and/or onto a front side of the interrupting chamber (9) by the infrared heater (2).
The method according to any of the previous method claims, comprising three interrupting chambers (9) with infrared heaters (2).
The method according to any of the previous method claims, comprising the steps of:
Measuring a temperature of a part of the interrupting chamber (9), of a switching fluid inside the fixed contact housing (8) and/or inside the moving contact housing (6), and

Controlling the emitting infrared heating radiation based on the measured temperature for reaching a target temperature.