1 Scope
This part of GB 20840 is applicable to newly manufactured instrument transformers with analogue or digital output for use with electrical measuring instruments or electrical protective devices having rated frequencies from 15 Hz to 100 Hz.
This part covers general requirements only. For each kind of instrument transformer the product standard is composed by this part and the relevant specific part.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of GB 20840. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this part of GB 20840. However parties to agreements based on this part of GB 20840 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
GB 311.1 Insulation co-ordination for high voltage transmission and distribution equipment (GB 311.1-1997; neq IEC 60071-1: 1993)
GB/T 2421.1 Environmental testing - General and guidance (GB/T 2421.1-2008; IEC 60068-1: 1988, IDT);
GB/T 2423.17 Envrionmental testing for electric and electronic products - Part 2: Test method - Test Ka: Salt mist (GB/T 2423.17-2008; IEC 60068-2-11: 1981, IDT)
GB/T 2423.23 Environmental testing for electric and electronic products Test Q: sealing (GB/T 2423.23-1995，idt IEC 60068-2-17: 1994)
GB/T 2423.55 Environmental testing for electric and electronic products - Part 2: Test methods - Test Eh: hammer tests (GB/T 2423.55-2006; IEC 60068-2-75: 1997, IDT)
GB 4208-2008 Degrees of protection provided by enclosure(IP code) (IEC 60529: 2001, IDT)
GB/T 4798.3 Environmental conditions existing in the application of electric and electronic products - Part 3: Stationary use at weather-protected locations (GB/T 4798.3-2007; IEC 60721-3-3: 2003, MOD)
GB/T 4798.4 Environmental conditions existing in the application of electric and electronic products - Part 4: Stationary use at non-weather-protected locations (GB/T 4798.4-2007; IEC 60721-3-4: 1995, MOD)
GB/T 5169.2 Fire hazard testing for electric and electronic products - Part 2: Guidance for assessing the fire hazard - General guidelines (GB/T 5169.2-2002; idt IEC 60695-1-1: 1999)
GB/T 5169.9 Fire hazard testing for electric and electronic products - Part 9: Guidance for assessing the fire hazard - Use of preselection testing procedures (GB/T 5169.9-2006; IEC 60695-1-30: 2002, IDT)
GB/T 5169.18 Fire hazard testing for electric and electronic products - Part 18: Guidance on the minimization of toxic hazards due to fire involving electric and electronic products - General (GB/T 5169.18-2005; IEC 60695-7-1: 1993, IDT)
GB/T 5465.2 Graphical symbols for use on electrical equipment - Part 2: Graphical symbols (GB/T 5465.2-2008; IEC 60417 DB: 2007, IDT)
GB/T 7354 Partial discharge measurements (GB/T 7354-2003; IEC 60270: 2000, IDT)
GB 7674 Gas-insulated metal-enclosed switchgear for rated voltages of 72.5kV and above (GB 7674-2008; IEC 62271-203: 2003, MOD)
GB/T 8905 Guide for management and measuring SF6 gas in electrical equipment (GB/T 8905-1996; neq IEC 60480: 1974)
GB/T 11021 Electrical insulation - Thermal classification (GB/T 11021-2007; IEC 60085: 2004, IDT)
GB/T 11022 Common specifications for high-voltage switchgear and controlgear standards (GB/T 11022-1999; eqv IEC 60694: 1996)
GB/T 11604 Testing procedure of radio interference generated by high voltage equipment (GB/T 11604-1989; eqv CISPR 18-1: 1982, CISPR 18-2: 1986)
GB/T 15022 (all parts) Resin based reactive compounds used for electrical insulation (IEC 60455, MOD)
GB/T 16927.1 High voltage test techniques - Part 1: General test requirements (GB/T 16927.1-1997, eqv IEC 60060-1: 1989)
GB/T 17623 Determination of componental contents of gases dissolved in insulating oil by gas chromatography method (GB/T 17623-1998; neq IEC 60567: 1992)
GB/T 20138-2006 Degrees of protection provided by enclosures for electrical equipment against external mechanical impacts (IK code) (IEC 62262: 2002, IDT)
GB/T 21221 Insulating liquids - Specifications for unused insulating liquids based on synthetic aromatic hydrocarbons (GB/T 21221-2007; IEC 60867: 1993, MOD)
GB/T 21429 Composite insulators - Hollow insulators for use in outdoor and indoor electrical equipment - Definitions test methods acceptance criteria and design recommendations (GB/T 21429-2008; IEC 61462: 1998, MOD)
JB/T 5895 Guide for the selection of insulators in respect of polluted conditions (JB/T 5895-1991; neq IEC 60815: 1986)
IEC 60296 Fluids for electrotechnical applications - Unused mineral insulating oils for transformers and switchgear
IEC 60376 Specification of technical grade sulphur hexafluoride (SF6) for use in electrical equipment
IEC 61634 High-voltage switchgear and controlgear - Use and handling of sulphur hexafluoride (SF6) in high-voltage switchgear and controlgear
IEC 62155 Hollow pressurized and unpressurized ceramic and glass insulators for use in electrical equipment with rated
voltages greater than 1,000 V
IEC 62271-2 High-voltage switchgear and controlgear - Part 2: Seismic qualification for rated voltages of 72.5 kV and above
IEC Guide 109 Environmental aspects - Inclusion in electrotechnical product standards
ISO 3231 Paints and varnishes - Determination of resistance to humid atmospheres containing sulfur dioxide
3 Terms and definitions
For the purposes of this part, the following terms and definitions apply.
3.1 General definitions
3.1.1
instrument transformer
transformer intended to transmit an information signal to measuring instruments, meters and protective or control devices or similar apparatus
3.1.2
enclosure
housing affording the type and degree of protection suitable for the intended application
3.1.3
primary terminals
terminals to which the voltage or current to be transformed is applied
3.1.4
secondary terminals
terminals which transmit an information signal to measuring instruments, meters and protective or control devices or similar apparatus
3.1.5
secondary circuit
external circuit receiving the information signals supplied by the secondary terminals of an instrument transformer
3.1.6
section
electrically conductive part of an instrument transformer insulated from other similar parts and equipped with terminals
3.2 Definitions related to dielectric ratings
3.2.1
highest voltage for a system
Usys
highest value of the phase-to-phase operating voltage (r.m.s. value) which occurs under normal operating conditions at any time and at any point in the system
3.2.2
highest voltage for equipment
Um
highest r.m.s. value of phase-to-phase voltage for which the equipment is designed in respect of its insulation as well as other characteristics which relate to this voltage in the relevant equipment standards
?
3.2.3
rated insulation level
combination of voltage values which characterizes the insulation of a transformer with regard to its capability to withstand dielectric stresses
3.2.4
isolated neutral system
system where the neutral point is not intentionally connected to earth, except for high impedance connections for protection or measurement purposes
3.2.5
resonant earthed system (a system earthed through an arc-suppression coil)
system in which one or more neutral points are connected to earth through reactances which approximately compensate the capacitive component of a single-phase-to-earth fault current
Note: With resonant earthing of a system, the residual current in the fault is limited to such an extent that an arcing fault in air is self-extinguishing.
3.2.6
earth fault factor
at a given location of a three-phase system, and for a given system configuration, the ratio of the highest r.m.s. phase-to-earth power frequency voltage on a healthy phase during a fault to earth affecting one or more phases at any point on the system to the r.m.s. value of phase-to-earth power frequency voltage which would be obtained at the given location in the absence of any such fault
Foreword i
Introduction iii
1 Scope
2 Normative references
3 Terms and definitions
3.1 General definitions
3.2 Definitions related to dielectric ratings
3.3 Definitions related to current or voltage ratings
3.4 Definitions related to accuracy
3.5 Definitions related to other ratings
3.6 Definitions related to gas insulation
3.7 Symbols and names
4 Normal and special service conditions
4.1 General
4.2 Normal service conditions
4.3 Special service conditions
4.4 System earthing
5 Ratings
5.1 General
5.2 Highest voltage for equipment
5.3 Rated insulation levels
5.4 Rated frequency
5.5 Rated output
5.6 Rated accuracy class
6 Design and construction
6.1 Requirements for liquids used in equipment
6.2 Requirements for gases used in equipment
6.3 Requirements for solid materials used in equipment
6.4 Requirements for temperature rise of parts and components
6.5 Requirements for earthing of equipment
6.6 Requirements for the external insulation
6.7 Mechanical strength requirements
6.8 Multiple chopped impulse on primary terminals
6.9 Internal arc fault protection requirements
6.10 Degrees of protection by enclosures
6.11 Electromagnetic compatibility (EMC)
6.12 Corrosion
6.13 Markings
6.14 Fire hazard
7 Tests
7.1 General
7.2 Type tests
7.3 Routine tests
7.4 Special tests
7.5 Sample tests
8 Rules for transport, storage, erection, operation and maintenance
9 Safety
10 Influence of products on the natural environment
Annex A (Informative) Comparison between this part and IEC 61869-1: 2007 in clause/subclause No.
Annex B (Informative) Technical deviations between this part and IEC 61869-1: 2007 and their justifications
Annex C (Informative) Rated primary terminal insulation level and altitude in standard IEC 61869-1: 2007
C.1 Highest voltage for equipment
C.2 Rated primary terminal insulation level
C.3 Chopped lightning impulse voltage
C.4 Rated frequency
C.5 Altitude
C.6 Mechanical strength requirements
Annex D (Informative) Fire hazard
D.1 Fire hazard
D.2 Fire hazard test
Annex E (Normative) Identification of test specimen
E.1 Data
E.2 Drawings
Annex F (Informative) Sample test
F.1 Sample test definition
F.2 Sample tests
Annex G (Informative) Rules for transport, storage, installation, operation and maintenance
G.1 General
G.2 Conditions during transport, storage and installation
G.3 Installation
G.4 Operation
G.5 Maintenance
G.6 Failure report
Bibliography
