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.

Tagged: Equipment Testing/Evaluation, P1a-4, Engineering Guidelines, P4

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.

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.

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

Project 3 - 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

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

Project 5 - Minimizing the Impact of Secondary Surges on Distribution Transformers

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.

Tagged: Equipment Testing/Evaluation, Engineering Guidelines, P4, P5-4