Transcript optimum specifications for current transformers

OPTIMUM SPECIFICATIONS
FOR
CURRENT
TRANSFORMERS
S.K.SHARMA, CEO
NORTEX MARKETING
POWER
INSTRUMENT
MEASUREMENT: Tremendous value of electrical power calls for
accurate measurement to ensure fair transaction.
PROTECTION:
Precious equipments and installations are to be
safeguarded against environmental/operational
hazards.
»
»
ACCURACY – as per need
RELIABILITY- 100%
Current transformers
• Low value / high significance
• Key component in metering/protective
schemes
CT
RELEY
EQUIPMENT
FUNCTIONS
• Range extension of instruments
• Standardization of instruments
• Instrument security
• Electrical isolation
• Realization of special
functions like; summation,
zero-sequencing etc.
AIMING AT MAXIMUM VALUE
COST
VALUE = ------------------------PERFORMANCE
OPTIMUM PERFORMANCE
Stated by the customer
Implied needs
Statutory/regulatory
manufacturers expertise
DESIGN SPECS
OPTIMUM COST
WHO
can do
PURCHASER
DESIGNER
PRODUCER
-
WHAT ?
OPTIMUM PARAMETERS
OPTIMUM PERFORMANCE
OPTIMUM OPERATIONAL COSTS
FIT – TO – USE PRODUCT
Popular short cut - Over specifying ???
Margins get cascaded
User
Purchaser
Designer
Producer
Lack of application
knowledge;
•Instrument charecterstics
•Environment
•Prospective fault
•Primary conductor size
Cost dynamics
PARAMETER
COST LAW
DISADVANTAGE
CONTROL
MAESURE
VA
POOR ACC & ISF
Actual VA
ID
Poor acc
Geometry of primary bar
ACC
System acc
Is
5A normal, 1A (dist. Mtg.)
Bulky & Heavy
ALF/
Vk
Fault level at spot
STC
Max. fault level
FINISH
ENVIRONMENT
TW
100
Normal
POLY
120
Corosive/humid
EPOXY
160
High temp.
BURDEN GUIDE
INSTRUMENT
INDUCTIVE
ELECTRONIC
AMMETER
3.0
0.5
CURRENT COIL
KWH/PF/KW
5.0
0.5
RECORDING
METERS
3.0
0.5
ACCURACY GUIDE
APPLICATION
DESIRED ACC. CLASS
Std. for Lab. testing
0.1
High acc. testing
0.2
Industrial metering
Commercial metering
Phase
not important
0.5 or 1.0
1.0
3, or 5
FURTHER READING
B. Hague
E.W.Golding
IS:2705-1993
IS:3156-1992
IS:4201-1983
IS:4146-1983
Instrument Transformers
Electrical measurements
and measuring instruments
Current Transformer-Specification
Voltage Transformer-Specification
Application Guide-CT
Application Guide-VT
Pitman-1936
Wheeler 1993
BIS
BIS
BIS
BIS
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