LRGBJ Dry Type Current Transformer
In early 2020 RHM International signed a long term supply agreement with a major North American utility for the design, manufacturing and delivery of dry type HV current transformers for the utility’s 72.5 kV, 145 kV, 170 kV, 245 kV and 330 kV power grid requirements. The supply agreement included an extensive homologation testing program that required the following type tests to be performed over the whole range of specifications:
- Lightning impulse voltage test on the primary terminals (performed on all ratings)
- Switching impulse voltage test (performed on 330 kV rating)
- Wet power frequency withstand test (performed on all ratings)
- Radio interference voltage (RIV) test (performed on 245 kV and 330 kV ratings)
- Temperature rise (performed on all ratings)
- Short-time current withstand test (performed on all ratings)
- Multiple chopped impulse test on the primary terminals (performed on 330 kV rating)
- Transient performance direct test verification of TPY class (performed on 170 kV, 245 kV and 330 kV ratings)
- 25 cycle (+20°C to -50°C) thermal endurance test (performed on 145 kV rating)
- 50 kA internal arc fault test (performed on 245 kV rating)
- Mechanical test (performed on all ratings)
- Silicone rubber UV resistance and flammability material tests
In addition, seismic dynamic analysis qualification reports for representative current transformers from each voltage class were also required to be submitted.
Seven representative designs were chosen for the homologation testing program. These included:
| Model | Voltage Rating (kV) | Primary Current (A) | Secondary Current (A) | Accuracy Class |
|---|---|---|---|---|
| LRGBJ-72.5 | 72.5 | 1000 x 2000 | 2 cores | C400/0.6B1.8 x C800/0.6B1.8 |
| 5/5 | ||||
| LRGBJ-145 | 145 | 1000 x 2000 | 4 cores | C400/0.6B1.8 x C800/0.6B1.8 |
| 5/5/5/5 | ||||
| LRGBJ-170 | 170 | 2000 x 4000 | 5 cores | 4 TPY - 10%, 5 x 10 VA |
| 1/1/1/1/5 | 1 metering - 0.5, 50 x 50 VA | |||
| LRGBJ-245 | 245 | 2000 x 4000 | 5 cores | 4 TPY - 10%, 5 x 10 VA |
| 1/1/1/1/5 | 1 metering - 0.5, 50 x 50 VA | |||
| LRGBJ-245 | 245 | 2000 x 4000 | 4 cores | C400/0.6B1.8 x C800/0.6B1.8 |
| 5/5/5/5 | ||||
| LRGBJ-330 | 330 | 2000 x 4000 | 5 cores | 4 TPY - 10%, 5 x 10 VA |
| 1/1/1/1/5 | 1 metering - 0.5, 50 x 50 VA | |||
| LRGBJ-330 | 330 | 2000 x 4000 | 4 cores | C400/0.6B1.8 x C800/0.6B1 |
| 5/5/5/5 |
Testing contracts were awarded to three test labs: Manitoba Hydro’s High Voltage Test Lab in Winnipeg, Manitoba, Canada, Powertech Labs in Surrey, British Columbia, Canada and KEMA Labs in Arnhem, the Netherlands. This was a highly complex project that required collaborative project management services with the owner utility, the three test labs and RHM’s facilities over a 2-year period.
The successful completion of the homologation test program provided the performance assurances the utility was seeking for their long-term commitment to this product.
The HV DryShield® dry type current transformer has been in operation over the past 25 years in all types of regions and climates. These successful very large scope tests confirm the unique reliability, safety and toughness of the technology and its ability to reliably replace oil and gas insulated designs to meet the environment protection objectives set for utilities.
