4c TCC Finding and Observations.pdf
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- Solicitation number
- 36C25925Q0292
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This document is a Time-Current Curves (TCC) Findings and Observations report for electrical systems at various buildings, likely part of the Grand Junction VA Medical Center. The report identifies multiple electrical protection and coordination issues across different building sections, including E-1 Medium Voltage Distribution System, E-2 Building 1 North, E-3 Building 1 South, E-4 Buildings 1, 5, 6, 8, 12, 13, 33, 35, 36, 37, and E-5 Building 9. Key findings include: transformer primary fuses not completely protecting transformers in the thermal range, low voltage breakers failing to achieve selective coordination in the instantaneous region, and ground relay configuration problems that could potentially de-energize entire systems during downstream ground faults. The report recommends specific actions such as increasing transformer primary fuse sizes, adding ground fault relaying to feeder breakers, and further investigating protective device coordination to improve electrical system safety and reliability.
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Time-Current Curves (TCC) Finding and Observations
E-1 MV (Medium Voltage Distribution System)
TCC-1 – The Utility line fuse and VA’s ATO fuses do not obtain selectively coordinate.
In the event of a fault either set of fuses could open.
Transformer T-1 North primary fuses do not completely protect the transformer in the thermal range.
E-2 --- Bldg 1 North
TCC-1 thru 10- The transformer’s primary fuses do not completely protect the transformer in the thermal range.
The main breaker and the transformer’s primary fuses do not achieve selective coordination.
Low voltage breakers do not achieve selective coordination.
TCC-1G – Switchboard MSA main breaker is equipped with a ground relay. Typically the associated feeder breakers should be equipped with ground fault relaying too. In the present condition the main’s ground relay can trip for a downstream ground fault de-energizing everything fed by MSA. Feeder breakers with ground relaying would allow for a single feeder to be opened rather than the entire system.
E-3 --- Bldg 1 South, 20
TCC-1 thru 6 -- Low voltage breakers do not achieve selective coordination in the instantaneous region.
TCC-7 thru 10 – The transformer’s primary fuse do not completely protect the transformer in the thermal range.
Low voltage breakers do not achieve selective coordination in the instantaneous region.
E-4 --- Bldg 1, 39, 45
TCC-1 – The transformer’s primary fuses provide reasonable protection based on the thermal damage curve and selective coordinate with the secondary main breaker.
Low voltage breakers do not achieve selective coordination in the instantaneous region.
TCC-2 -- The transformer’s primary fuses provide reasonable protection based on the thermal damage curve and selective coordinate with the secondary main breaker.
TCC-3 --- Overall protective devices achieve reasonable selective coordination.
TCC-4 --- Consideration should be given to increasing the transformer’s primary fuse to a 65E. The present fuse does not coordinate with the secondary main breaker and encroaches on the instantaneous range of the low voltage breakers.
Low voltage breakers do not achieve selective coordination in the instantaneous region.
E-4 --- Bldg 5, 6, 8, 12, 13, 33, 35, 36, 37
TCC-1, 4, 5, and 6 – The transformer’s primary fuses do not completely protect the transformer in the thermal range.
Low voltage breakers do not achieve selective coordination in the instantaneous region.
TCC-2 – The transformer’s primary fuses do not completely protect the transformer in the thermal range.
TCC-3 - Overall protective devices achieve reasonable selective coordination.
E-5 --- Bldg 9
TCC-1 thru 6 - Low voltage breakers do not achieve selective coordination in the instantaneous region.
TCC-1G – Switchboard 9-ECP-2 main breaker is equipped with a ground relay.
Typically the associated feeder breakers should be equipped with ground fault relaying too. In the present condition the main’s ground relay can trip for a downstream ground fault de-energizing everything fed by 9-ECP-2. Feeder breakers with ground relaying would allow for a single feeder to be opened rather than the entire system.
File details come from the government source that posted it. Updated .