Insulated bushings for alternating voltages above 1 000 V
1 Scope
This standard specifies the characteristics and tests for insulated bushings (hereafter referred to as bushings).
This standard is applicable to bushings, as defined in Clause 3, intended for use in electrical apparatus, machinery, transformers, switchgear and installations for three-phase alternating current systems, having highest voltage for equipment above 1000 V and power frequencies of 15 Hz up to and including 60 Hz.
Subject to special agreement between purchaser and supplier, this standard may be applied, in part or as a whole, to the following:
- bushings used in other than three-phase systems;
- bushings for high-voltage direct current systems;
- bushings for testing transformers;
- bushings for capacitors.
Special requirements and tests for transformer bushings in this standard apply also to reactor bushings.
This standard is applicable to bushings made and sold separately. Bushings which are a part of an apparatus and which cannot be tested according to this standard shall be tested with the apparatus of which they form part.
2 Normative references
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 156-2017 Standard voltages (IEC 60038:2009, MOD)
GB 311.1-2012 Insulation co-ordination - Part 1: Definitions, principles and rules (IEC 60071-1:2006, MOD)
GB 762-2002 Standard current ratings (eqv IEC 60059:1999)
GB 1094.1-2013 Power transformers - Part 1: General (IEC 60076-1:2011, MOD)
GB/T 1094.2-2013 Power transformers - Part 2: Temperature rise for liquid-immersed transformers (IEC 60076-2:2011, MOD)
GB/T 1094.3-2017 Power transformers - Part 3: Insulation levels, dielectric tests and external clearances in air (IEC 60076-3:2013, MOD)
GB 1094.5-2008 Power transformers - Part 5: Ability to withstand short circuit (IEC 60076-5:2006, MOD)
GB/T 1094.7-2008 Power transformers - Part 7: Loading guide for oil-immersed power transformers (IEC 60076-7, 2005, MOD)
GB/Z 1094.14-2011 Power transformers - Part 14: Design and application of liquid-immersed transformers using high-temperature insulation material (IEC/TS 60076-14: 2009, IDT)
GB/T 2423.23-2013 Environmental testing - Part 2: Test methods - Test Q: Sealing (IEC 60068-2-17: 1994, IDT)
GB 2536-2011 Fluids for electrotechnical applications - Unused mineral insulating oils for transformers and switchgear (IEC 60296:2003, MOD)
GB/T 2900.5 Electrotechnical terminology - Electrical insulating solids,liquids and gases (GB/T 2900.5-2013, IEC 60050-212:2010, IDT)
GB/T 2900.5-2013 Electrotechnical terminology - Electrical insulating solids, liquids and gases (IEC 60050-212: 2010, IDT)
GB/T 2900.8-2009 Electrotechnical terminology - Insulators (IEC 60050-471: 2007, IDT)
GB/T 4585 Artificial pollution tests on high-voltage insulators to be used on a.c. systems (GB/T 4585-2004, IEC 60507:1991, IDT)
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3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 2900.5-2013 and GB/T 2900.8-2009 as well as the following apply.
3.1
bushing
device that enables one or several conductors to pass through a partition such as a wall or a tank, and insulates the conductors from it
Note 1: the conductor may form an integral part of the bushing or be drawn into the central tube of the bushing.
Note 2: the means of attachment (flange or fixing device) to the partition forms part of the bushing.
3.2
liquid-filled bushing
bushing in which the space between the inside surface of the insulating envelope and the solid major insulation is filled with mineral oil or other insulating liquid
3.3
compound-filled bushing
bushing in which the space between the inside surface of the insulating envelope and the solid major insulation is filled with an insulating compound
3.4
liquid-insulated bushing
bushing in which the major insulation consists of mineral oil or another insulating liquid, enclosed by an insulating envelope
Note: these bushings are often of an open design which require proper processing after installation in order to avoid trapped air and subsequent partial discharges during testing or in service.
3.5
gas-filled bushing
bushing in which the space between the inside surface of the insulating envelope and the solid major insulation is filled with gas (other than ambient air) at atmospheric pressure or higher
Note: this definition includes bushings which are intended to form an integral part of gas-insulated equipment, the gas of the equipment being in communication with that of the bushing.
3.6
gas-insulated bushing
bushing in which the major insulation consists of gas (other than ambient air) at atmospheric pressure or higher
Note 1: this definition includes bushings which are intended to form an integral part of gas-insulated equipment, the gas of the equipment being in communication with that of the bushing. Such bushing is not immersed bushing (see 3.19 and 3.20).
Note 2: a bushing which contains solid insulating materials other than the envelope containing the gas (e.g. support for conducting layers or insulating cylinder), is a combined insulation bushing (see 3.1 4).
Note 3: a bushing in which the desired voltage grading is obtained by an arrangement of conducting or semi-conducting layers incorporated in an insulating material (e.g. plastic film) is referred to as a gas insulated capacitance graded bushing.
3.7
gas-impregnated bushing
bushing in which the major insulation consists of a core wound from paper or plastic film (GIF) and subsequently treated and impregnated with gas (other than ambient air) at atmospheric pressure or higher
Note: the space between the core and the insulating envelope being filled with the same gas as used for the impregnation.
3.8
oil-impregnated paper bushing; OIP
bushing in which the major insulation consists of a core wound from paper and subsequently treated and impregnated with an insulating liquid, generally mineral oil
Note: the space between the core and the insulating envelope being filled with the same insulating liquid as that used for impregnation.
3.9
lipa-covered film bushing; LCF
bushing in which the major insulation consists of a core wound from film covered with lipa insulating medium (e.g. silicone oil)
3.10
resin-impregnated paper bushing; RIP
bushing in which the major insulation consists of a core wound from untreated paper and subsequently impregnated with a curable resin
Note: a resin-impregnated paper bushing can be provided with an insulating envelope, in which case the intervening space can be filled with an insulating liquid or another insulating medium.
3.11 Resin-impregnated synthetics bushing
3.11.1
resin-impregnated synthetics bushing; RIS
bushing in which the major insulation consists of a core wound from synthetics subsequently impregnated with a curable resin
Note: a resin-impregnated synthetics bushing can be provided with an insulating envelope, in which case the intervening space can be filled with an insulating liquid or another insulating medium.
3.11.2
resin-impregnated fiber bushing; RIF
bushing in which the major insulation consists of a core wound from resin-impregnated fiber
3.12
ceramic or analogous material bushing
bushing in which the major insulation consists of a ceramic or analogous inorganic material
3.13
cast or moulded resin-insulated bushing
bushing in which the major insulation consists of a cast or moulded organic material with or without an inorganic filler
3.14
combined insulation bushing
bushing in which the major insulation consists of a combination of at least two different insulating materials
3.15
capacitance graded bushing
bushing, in which a desired voltage grading is obtained by an arrangement of conducting or semiconducting layers incorporated into the insulating material
