Generator Interconnection Impact Study Report Pamlico County, NC 200 MW Wind Farm Queue #281 June 6, 2012, Inc.
PURPOSE The purpose of this impact study is to assess the impacts of a wind farm interconnection request on the reliability of the Progress Energy Carolina, Inc. (PEC) transmission system with respect to power-flow, short circuit and stability issues. The CUSTOMER requested that the proposed project be considered and studied as a Network Resource Interconnection. Estimates of the cost and time required to interconnect the generation as well as to resolve the issued identified in this impact analysis are also included. The PEC internal system analysis consists of an evaluation of the internal PEC transmission system utilizing documented transmission planning criteria. The request is described in Table 1 below. Table 1: Request PEC Generator Interconnection Queue No. MW In-Service Date Queue #281 200 10/31/14 County Pamlico County, NC Facility Bayboro 230 kv Substation The 200 MW total is comprised of 111 individual 1.8 MW wind turbine generators. Interconnection to PEC s substation is via a 34.5 kv collector system and a 34.5/230 kv transformer. ASSUMPTIONS The following impact study results are from the PEC internal power-flow models that reflect specific conditions of the PEC system at points in time consistent with the generator interconnection requests being evaluated. The cases include the most recent information for load, generation additions, transmission additions, interchange, and other pertinent data necessary for analysis. Future years may include transmission, generation, and interchange modifications that are not budgeted and for which no firm commitments have been made. Further, PEC retains the right to make modifications to power-flow cases as needed if additional information is available or if specific scenarios necessitate changes. For the systems surrounding PEC, data is based on the ERAG MMWG model. The suitability of the model for use by others is the sole responsibility of the user. Higher queued generator interconnection requests were considered in this analysis. Specifically, Q#277, a 900 MW block of offshore wind generation was assumed to be connected at Morehead Wildwood 230 kv substation in 2017, along with transmission upgrades identified in the Q#277 impact study dated January 6, 2011, but is no longer included since Q#277 has now been withdrawn. The results of this analysis are based on Interconnection Customer s queue requests including generation equipment data provided. If the facilities technical data or interconnection points to the transmission system change, the results of this analysis may need to be reevaluated. This study was based on the following assumptions: CUSTOMER would have one interconnection point to PEC s Bayboro 230 kv Substation off the Aurora - New Bern 230 kv Line. CUSTOMER would construct, own and operate the electrical infrastructure that would connect their generation to the PEC s existing Bayboro 230 kv substation, - 2 -
RESULTS including any step up transformers and lines from the wind farm, but excluding the 230 kv circuit breaker in the Bayboro 230 kv substation. Higher queued request (Q#277) had been assumed to come on-line in 2017, but has subsequently been withdrawn. Power-flow Analysis Results (Network Resource Interconnection) Facilities that may require upgrade within the first three to five years following the in-service date are identified. Based on projected load growth on the PEC transmission system, facilities of concern are those with post-contingency loadings of 95% or greater of their thermal rating or low voltage of 0.92 pu and below, for the requested in-service year or the in-service year of a higher queued request. The identification of these facilities is crucial due to the construction lead times necessary for certain system upgrades. This process will ensure that appropriate focus is given to these problem areas to investigate whether construction of upgrade projects is achievable to accommodate the requested interconnection service. As requested, the 200 MW wind farm was studied interconnected to PEC s Bayboro 230 kv substation. Contingency analysis study results show that interconnection of this generation facility results in the following thermal issues on the PEC system. Based on study results for 2014, Table 2 shows thermal facility loadings for this request: Table 2: Power-flow Thermal Results Transmission Facility Loading % Contingency Bayboro 230 kv Tap 121% Base Case Additionally, it will be necessary to install a transfer trip protection scheme to separate this generation facility from the PEC system for faults on the Aurora -New Bern 230 kv line. Estimate of Resolutions for Power-flow Impacts The following are PEC s current best estimates for resolution of impacts identified in Table 2 and the addition of transfer trip protection. Solutions, cost estimates and implementation schedules will be refined in the Customer s Generator Interconnection Facility Study Report. The Wave Trap on the Bayboro Tap limits the existing rating to 400 amps. The existing Wave Trap in the tap will be removed and a Wave Trap will be added at Grantsboro POD and Bayboro 230 kv substation. Facility Upgrades Required in 2014 Bayboro 230 k V Tap (Two(2) New Wave Traps) Potential Solution: Install One (1) 230 kv Wave Trap at Tideland EMC Grantsboro POD and One(1) 230 kv Wave Trap at Bayboro 230 kv substation. See Figure 1. - 3 -
Distance: N/A Estimated Cost: $200,000 Estimated Schedule: 10/31/2014 Bayboro, New Bern and Aurora 230 kv Substations (Install Transfer Trip Scheme) Potential Solution: Install protection system and transfer trip for coordination between the Aurora-New Bern 230 kv line and proposed generation facility. See Figure 1. Distance: N/A Estimated Cost: $100,000 Estimated Schedule: 10/31/2014 Total Power-flow Cost Estimate: $300,000 (total) Stability Analysis Results A stability analysis was performed to determine the impact of the proposed generation addition on the PEC transmission system and other nearby generation. The proposed 200 MW wind farm generation is comprised of 111 Vestas V100, 1.8 MW wind turbine generators. The wind turbine collector branches are connected to a single 34.5 kv collector bus and a single 34.5/230 kv step-up transformer. For the dynamics analysis, all wind turbines and collector branches were represented by one lumped equivalent including a generator, a step-up transformer, and a collector system impedance. The interconnection of the equivalent wind farm system to PEC s Bayboro 230 kv substation is via one 34.5/230 kv transformer and one short (less than 500 feet) 230 kv line, each modeled explicitly. These wind machines were modeled using the Customer supplied Vestas Generic PSS/E Model Version 7.2 and Customer supplied model parameters, including those for the voltage and frequency protection settings. The collector system configuration and impedances were also provided by the Customer. A number of normally clearing and delayed clearing faults were simulated to assess the stability and voltage ride-through capabilities of the proposed wind generation. Both summer peak and off-peak conditions were simulated for each fault. The proposed wind farm generation was stable with acceptable voltage ride-through for all faults simulated. No adverse impact to other area generation was noted as a result of the proposed wind farm. If the Customer provided data changes from that provided, these results will need to be reevaluated. LGIP Power Factor Requirements PEC s Large Generator Interconnection Procedure (LGIP) requires the proposed generating units to be capable of delivering the power to the point of interconnection (POI) at a 0.95 lagging power factor. The POI is the Bayboro 230 kv substation. The Customer provided data indicates a wind farm total capacity of 200 MW. Since the wind generators themselves - 4 -
may not be capable of supplying an appreciable amount of MVARs, a separate dynamic var source, such as a static var compensator or similar FACTS device, may need to be installed by the Customer to meet this requirement. As additional design plans and details becomes available, PEC will work with the Customer to determine the adequacy of the wind generators themselves to provide the required dynamic var capability requirements at the point of interconnection. Estimate to Meet LGIP Power Factor Requirements The majority of the costs to meet the LGIP Power Factor requirement will be associated with the design and installation of Customer owned equipment. Since these costs will be incurred by the Customer, they are not included in this estimate. Short Circuit Analysis Results A short circuit analysis was performed to assess the impact of the proposed wind farm generation addition on transmission system equipment capabilities. The analysis conservatively modeled the proposed wind generation as an equivalent amount of classical generating units for short circuit purposes. The analysis indicates that no short circuit equipment capabilities will be exceeded as result from the proposed generation addition and associated transmission upgrades. The results of the short circuit study are based on Customer provided generation equipment data and location. Also, the prudent use of engineering assumptions and typical values for some data were used. If the units technical data or interconnection points to the transmission system changes, the results of this analysis may need to be reevaluated. Interconnection of Customer s Generation The point of interconnection (POI) for Queue #281 is at PEC s Bayboro 230 kv substation. See Figure 1. The costs of expanding the Bayboro 230 kv substation to install a new 230 kv circuit breaker and associated equipment, including protection system, are summarized below. Estimated Costs: $1, 200, 000 Estimated Schedule: 10/31/2014 Also, the customer should verify that the MVA ratings of their lines are sufficient to accommodate delivering the total wind farm MVA output to the point of interconnection at the required 0.95 power factor. SUMMARY This Generator Interconnection Impact Study assesses the impact of interconnecting a new generation facility consisting with a total NET summer/winter rating of 200 MW. Studies - 5 -
indicate that thermal and interconnection upgrades are necessary to the PEC Transmission System to accommodate this queue request. Current estimates are that the proposed upgrades can be completed to meet the Customer s schedule. This is based on an assumption that PEC would have a firm commitment from the customer no later than 24 months in advance of the request in-service date. The additional cost for telecommunications and metering can be estimated as a monthly charge of $3,000/month. Network Resource Interconnection Estimate Cost: Power-flow (2014) $300, 000 Stability $0 Short Circuit $0 Power Factor * $0 Interconnection (2014) $1, 200,000 Total Estimate $1, 500,000 *Not including any cost the for Customer installed/owned equipment (such as a static var compensator) that may be required to meet the Power Factor requirement. - 6 -
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