Program 4

Project 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.

  • delta primary three-phase padmount transformer
  • grounded-wye primary three-phase transformers having amorphous metal cores
  • grounded-wye primary three-phase transformers having five-leg stacked cores.
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Tagged: P1a-4, P4, Equipment Testing/Evaluation, Engineering Guidelines

Project 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.

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Tagged: P1b-4, P4, Equipment Testing/Evaluation, Engineering Guidelines

Project 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.

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Tagged: P1c-4, P4, Equipment Testing/Evaluation, Engineering Guidelines

Project 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
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Tagged: P2-4, P4, Equipment Testing/Evaluation, Engineering Guidelines

Project 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.

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Tagged: P3-4, P4, Equipment Testing/Evaluation, Engineering Guidelines