Solar Impact Case Study. Trishia Swayne, P.E. Leidos

Transcription

1 Solar Impact Case Study Trishia Swayne, P.E. Leidos

2 Introduction Clean Energy Outlook

3 Agenda Case study profile Load scenarios determined Base case model established Analysis and results Summary and

4 Case Study Profile 298 kw of proposed PV Two primary points of through transformers Four step down transformers within camp Two 23 kw inverters and nine 28 kw inverters total Primary voltage of 13.2 kv; only one circuit served from the transformer Site is 3.4 miles from the There is 5,135 feet of secondary overhead within the camp to interconnect the inverters The circuit has 8.1 kw of rooqop, solar

5 Case Study Profile PV Site Substa'on

6 Load Scenarios One year of hourly circuit data provided (MW, MVAR)- Filter to hours only PEAK MIN

7 Base Case Model Regulator and capacitor Pole # Phase Size Layout Hold Voltage Bandwidth Compensa'on (R) Compensa'on (X) Time Delay K45399 A 219 Pole K44869 A 50 Pole K44867 B 100 Pole K44868 C 100 Pole A 219 Pla\orm B 219 Pla\orm C 219 Pla\orm K45291 C 100 Pole Pole # KVAR Total Type Control Phase Can Size(s) Voltage Fixed K Fixed K Time Controlled A K Fixed

8 Base Case Model Add PV to model Pole Interconnected? Type kw Yes as of 12/11/2012 PV K45473 Yes as of 10/8/2014 PV 4

9 Analysis Reverse power flow problem Voltage and capacity review Voltage flicker analysis Short circuit analysis Risk of islanding assessment

10 Analysis - Reverse Power Flow Load dura@on curve at substa@on transformer (day@me hours only) MW

11 Analysis Voltage and Capacity Pre and post project load flows conducted Primary feeder voltage remains within planning criteria (126 V 118 V) Conductor capacity issues were not iden@fied High voltage was iden@fied on the secondary side of the project site, as high 146 V Bank of single- phase line regulators will experience reverse power flow

12 Analysis Voltage and Capacity

13 Analysis Voltage Flicker Analysis Criteria for this is IEEE 519; all PV in the model is studied in on/off format

14 Analysis Voltage Flicker Analysis Allowable Primary System Min Load Flicker (%) Max Load Flicker (%) Secondary System Min Load Flicker (%) Max Load Flicker (%) 2% 0.23% 1.03% 15.94% 16.46%

15 Analysis Short Circuit The primary transformers at the two points of are grounded wye on both windings The four new transformers within the camp are also grounded wye on both windings The inverters are able to the neutral of the step- transformers, a solidly grounded system

16 Analysis Short Circuit grounding indicate the system is grounded with the project online, based on IEEE < X0 < 3 X1 0 < < 1 R0 X1

17 Analysis Short Circuit Analysis was conducted to confirm if overvoltages on unfaulted phases at the point of would be of concern Use fault flow in WindMil to evaluate

18 Analysis Short Circuit Run fault current and determine if fault currents on the feeder exceed GEN Status Fault Loca'on LG LG LLL LLL Maximum % Fault (Amps) (MVA) (Amps) (MVA) Current Contribu'on OFF 13 kv Bus Substa@on 3, , ON 13 kv Bus Substa@on 3, , OFF 69 kv Bus Substa@on 4,346 5,193 4, ON 69 kv Bus Substa@on 4,347 5,195 4, % 0.04%

19 Analysis Risk of Islanding Four- step analysis was conducted based on the November 2012 Sandia Suggested Guidelines for Assessment of DG Islanding Risk report

20 Analysis Risk of Islanding Step 1: Determine whether the aggregate AC of all DG exceeds 2/3 of the minimum feeder loading. If Yes, proceed to Step 2. If No, there is minimal risk of islanding and analysis is complete. Step 2: Determine whether QPV + Qload is within 1% of the total aggregate capacitor ra@ng within the island, or alterna@vely, use real and reac@ve power flow measurements or simula@ons at the point at which the island can form to determine whether the feeder power factor is ever higher than 0.99 (lag or lead) at that point for an extended period If Yes to either evalua@on, a detailed islanding analysis should be considered. If No, proceed to Step 3. Step 3: Determine whether the poten@al island contains both rota@ng and inverter- based DG, and the sum of the AC ra@ngs of the rota@ng DG is more than 25% of the total AC ra@ng of all DG in the poten@al island. If Yes, a detailed islanding analysis should be considered. If No, proceed to Step 4. Step 4: Sort the inverters by manufacturer, sum up the total AC ra@ng of each manufacturer s product within the poten@al island, and determine each manufacturer s percentage of the total DG. If no single manufacturer s product makes up at least 2/3 of the total DG in the poten@al island, then further study may be prudent. If the situa@on is such that more than 2/3 of the total DG is from a single manufacturer, then the risk of uninten@onal islanding can be considered negligible.

21 Analysis Risk of Islanding Y indicates risk Poten'al Island Step 1 (Y/N) Step 2 (Y/N) Step 3 (Y/N) Step 4 (Y/N) Circuit 3096 Y Y N N

22 Analysis Summary & Viola'on Reverse power flow at Excessive voltage flicker at site secondary Excessive steady state voltage at inverters Reverse power flow at bank of line regulators Risk of islanding Mi'ga'on Replace regulator controls Construct primary to site instead of ~1 mile of secondary Replace regulator controls Direct Transfer Trip (DTT)

23 Trishia Swayne, P.E. Leidos Director Studies Phone: