BPA Air Conditioner Test Results Tests on November 22nd and 28th, 2016

Key Takeaways Stalling Depends on many factors There is no single “correct” set of stall values to use These tests support the WECC phase 2 default values of Vstall=0.45 and Tstall=2 cycles as reasonable conservative values More optimistic values that are still within the realm of reason are: Vstall=0.45 and Tstall=5 cycles Vstall=0.40 and Tstall=3 cycles or even 5 cycles

Factors which impact air conditioner stalling Factors impacting AC stalling Voltage dip magnitude Voltage dip duration Time to ramp down from initial voltage to dip voltage Final voltage (recovery voltage) Time to ramp up from dip voltage to final voltage Ambient temperature Fault initiating on the positive crest, zero crossing, or negative crest of the voltage wave cycle With all of these factors, there is no single “correct” value to use for Tstall and Vstall

Voltage Dip Test Variables Vrecovery Vdip Tramp Trecovery Tdip t

Test Background These tests were conducted with a “Train” brand reciprocating compressor air conditioner Tests were conducted on Nov. 22nd with an ambient temperature in the mid 90s F, and Nov. 28th with an ambient temperature at about 100 F

Nov. 22nd BPA Lab Tests Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp 2 cycles 0.4 ramp 0.85 recovery 0.5 cycle ramp, crest yes 22-Nov mid 90's 0.45 no 3 cycles 0.5 4 cycles 5 cycles 6 cycles 9 cycles 12 cycles Tests assumed a 0.5 cycle ramp down to Vdip, ramp started at the crest, and an instantaneous recovery to 0.85 pu Key result here is that at Vdip=0.5 pu the air conditioner does not stall even for long dips (Tdip at 6 cycles, which is longer than 500 kV and 230 kV normal clearing times) The data here also supports Vstall=0.45 and Tstall=32 ms as conservative WECC default data May or may not stall for Vdip=0.45 and Tdip=3 cycles Note it did stall for V=0.45 and Tdip 3 cycles. Didn’t stall until 12 cycles for Vdip 0.5

Nov. 28th BPA Lab Tests Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp 2 cycles 0.45 ramp 0.85 recovery 0.5 cycle ramp, 0 xing no 28-Nov 100 3 cycles 99 0.4 yes 4 cycles Tests assumed a 0.5 cycle ramp down to Vdip, ramp started at the zero crossing, and an instantaneous recovery to 0.85 pu Temperature was slightly higher than the Nov. 22nd tests, also we applied the ramp starting a zero crossing instead of starting at the crest Key result here is that recommending Vstall=0.45 and Tstall=0.032 s is conservative. A sensitivity study can decrease Vstall to 0.40 and Tstall to 3 cycles and still be within the realm of reason. Results show the air conditioner may or may not stall at this point

Nov. 28th BPA Lab Tests (2) Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp comments 2 cycles 0.45 ramp 0.85 recovery 0.5 cycle ramp, 0 xing no 28-Nov 100 no recovery ramp 0.5 cycle recovery ramp 1 cycle recovery ramp 0.4 yes Tests assumed a 0.5 cycle ramp down to Vdip, ramp started at the zero crossing, and varied ramp up to recovery of 0.85 pu Temperature was slightly higher than the Nov. 22nd tests, also we applied the ramp starting a zero crossing instead of starting at the crest Key result here is that contactors consistently opened for Vdip=0.40 pu and consistently did not open for Vdip = 0.45 pu, regardless of whether recovery voltage was instantaneous or ramped over a cycle Another result is that adding a 1 cycle ramp to the recovery voltage did not necessarily make the air conditioner more prone to stalling, at least not for Tdip=2 cycles.

Nov. 28th BPA Lab Tests (3) Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp comments 4 cycles 0.45 ramp 0.85 recovery 0.5 cycle ramp, 0 xing no 28-Nov 99 no recovery ramp 0.5 cycle recovery ramp 1 cycle recovery ramp 5 cycles Tests assumed a 0.5 cycle ramp down to Vdip, ramp started at the zero crossing, and varied ramp up to recovery to 0.85 pu Temperature was slightly higher than the Nov. 22nd tests, also we applied the ramp starting a zero crossing instead of starting at the crest Key result here is that when doing sensitivity studies it is reasonable to set Vstall=0.45 and increase Tstall to 5 cycles. Also, assuming a 1 cycle ramp up to the recovery voltage of 0.85 does not necessarily increase likelihood of stalling

no recovery ramp, repeat test Nov. 28th BPA Lab Tests (4) Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp comments 3 cycles 0.4 ramp 0.85 recovery 0.5 cycle ramp, 0 xing yes 28-Nov 100 no recovery ramp no 99 no recovery ramp, repeat test 4 cycles 1 cycle ramp, 0 xing 5 cycles Key result here is that assuming a 1 cycle ramp down for Vdip instead of a 0.5 cycle ramp down significantly improves performance If a 1 cycle ramp is assumed, then Vstall=0.4 and Tstall=5 cycles is within the realm of reason For a 0.5 cycle ramp, the air conditioner may or may not stall for Vdip=0.40 and Tstall=3 cycles. This supports the WECC recommended Vstall=0.45 and Tstall=0.032 s as conservative parameters V=0.4 and Tdip=5 cycles in even more optimistic than what I put in the takeaway slide

Nov. 28th BPA Lab Tests (5) Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp 2 cycles 0.4 ramp 0.85 recovery 0.5 cycle ramp, 0 xing no yes 28-Nov 100 no ramp, 0 xing no ramp, crest Key result here is that assuming a 0.5 cycle ramp instead of no ramp has a significant impact on performance

Nov. 28th BPA Lab Tests (6) Tdip Vdip POW recovery ramp, starts at Stalled? Contactors opened? date temp 2 cycles 0.4 ramp 0.85 recovery no ramp, crest yes 28-Nov 100 no ramp, crest, negative no Key result here is assuming the dip starts on a negative crest gives a different result from assuming the dip starts on a positive crest This may be because the air conditioner has an auxiliary winding with an in-run capacitor, so the positive voltage crest looks different from the negative voltage crest to the motor If a 0.5 cycle ramp is assumed, then Vstall=0.4 and Tstall=2 cycles is within the realm of reason

Single Phase Motor Schematic Note the in-run capacitor on the aux winding Because of this, a positive voltage peak looks different than a negative voltage peak

Plots from Lab tests These plots are from Tests done November 22nd and November 28th, 2016 at BPA using a Train brand reciprocating AC Results are sorted in order of Vdip from highest to lowest (best to worst case) For a given Vdip, results are sorted by Tdip from lowest to highest (best to worst case)

Tdip POW to start ramp down on Recovery voltage Ramp duration Vdip (% of initial voltage) date Initial voltage

Main winding voltage Hi pressure chamber Aux winding voltage Main current Aux current

Zoomed out view of a stall

Zoomed in view of the same stall

This one stalled and then managed to restart on its own