107
Capacitance and DF Measurement on High-Voltage Bushings
General guidelines for evaluating the C
1
capacitance data are as follows:
7.9 References
Table 7-2 General guidelines for evaluating the C1 capacitance data
ΔC = C
measured
- C
ref
*
Evaluation:
ΔC < 5%
Acceptable
5% < ΔC < 10%
Should be investigated
ΔC > 10%
Critical
* with C
ref
= nameplate value or value for new bushing
Evaluation:
DF
meas
< 2 x DF
ref
Acceptable
DF
meas
< 3 x DF
ref
Should be investigated
DF
meas
> 3 x DF
ref
Critical
* with DF
ref
= nameplate value or value for new bushing
[4.1] ANSI Standard 62-1995: "IEEE Guide for Diagnostic Field
testing of Electric Power Apparatus - Part 1: Oil Filled Power
Transformers, Regulators, and Reactors", IEEE New York,
1995
[4.2] CIGRE-WG 12-05: An international survey on failures in large
power transformers in service, Electra No. 88 1983, S. 21-48
[4.3] US Bureau of Reclamation: "Testing and Maintenance of High
Voltage Bushings", Facility instructions, standards and
techniques - Vol. 3-2, Denver, 1991
[4.4] Schurman, D.: Testing and maintenance of high voltage
bushings, Western Area Power administration, Golden
(Colorado), 1999
[4.5] Sundermann, U.: "Transformer life cycle management"
1.Symposium Geriatrie des Transformators, Regensburg 2002
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