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Program
4
4-1a Ferroresonance Guidelines for Additional
Padmount Transformer Types
Create guidelines specifying the maximum cable length which
can be switched for the following types of transformers without excessive overvoltage.
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delta primary three-phase padmount transformer
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grounded-wye primary three-phase transformers having
amorphous metal cores
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grounded-wye primary three-phase transformers having
five-leg stacked cores.
Deliverables: Ferroresonance Guidelines
for Additional Padmount Transformer Types final report 5/94 and diskette containing
Critical Cable Length Guidelines.
4-1b Survivability of MOV Arresters Subjected to
Ferroresonance Overvoltages
Determine the capability of metal-oxide surge arresters to
survive exposure to ferroresonant overvoltage caused by the interaction of three-phase
grounded-wye padmount transformers and URD cable capacitance. Create guidelines indicating
the maximum cable length which can be switched with a transformer, in terms of the
arrester type, arrester voltage rating, and system voltage class.
Deliverable: Survivability of MOV
Arresters Subjected to Ferroresonance Overvoltages” final report 11/94.
4-1c Ferroresonance Survivability of Under-Oil
Arresters
Extend the research performed in Phase 1B to perform a more
in-depth evaluation of arrester survivability when exposed to amorphous-core three-phase
transformer ferroresonance, and in particular to assess the performance of under-oil
arresters in this condition. Create guidelines indicating the range of application
parameters for which an under-oil arrester can be expected to survive extended exposure to
amorphous transformer ferroresonance.
Deliverable: Ferroresonance Survivability
of Under-oil Arresters, final report 11/96.
4-2
Distribution Transformer Harmonic Derating Guidelines
Measure the resistance of a diverse group of single and
three phase distribution transformers from 60 Hz to 1500 Hz. Develop tables which indicate
permissible harmonic loads for the folloowing load combinations:
- 60 Hz and 6 pulse drives
- 60 Hz and 12 pulse drives
- 60 Hz and switch mode power supplies
- 60 Hz and compact fluorescent lighting
Deliverable: Distribution Transformer
Harmonic Derating, final report 12/94.
4-3
Secondary Surge Guidelines
Develop Analytic Models to investigate lightning-induced
surges on distribution secondaries. Determine which system parameters have the greatest
effect on the first layer voltage in distribution transformers. Develop a spreadsheet
which calculates the overvoltage performance of 10 and 25 kVA transformers for rural and
residential circuits over a range of pole ground resistances.
Deliverables: Minimizing the Impact of Secondary Surges on
Distribution Transformers, final report 2/96 and diskette containing Evaluation of
Secondary Surges, 7/96.
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