Small Generator Interconnection Completed For Q0047 Proposed Interconnection PacifiCorp s Existing Goshen Rigby 69 kv Line March 7, 2005
1.0 Description of the Generation Facility Q0047 ( Interconnection Customer ) Project is located approximately 11 miles northeast of Idaho Falls Idaho. The project consists of twelve 575 volt, 1.5 MW wind turbine generators, connected to a 14.4 kv distribution system ( Project ). Each generator is connected to the distribution circuit via a.575 14.4 kv transformer. A single, 3-phase, 69 / 14.4 kv, 15/20/25 MVA transformer is used to step up the voltage of the project to 69 kv. A 3.6 mile, 4/0 ACSR "Penguin" 69 kv conductor transmission line will connect the project to the PacifiCorp ( Transmission Provider ) 31.4 mile, Sugar Mill/Goshen Rigby 69 kv line. The Point of Interconnection will be located about 3 miles south of the Ucon substation tap and three miles north of the Sandcreek substation tap. Interconnection Customer will own the 3.6 mile, 69 kv line to the Point of Interconnection. 2.0 Scope of Study The study was conducted to discover any voltage or other transmission impacts from the integration of this Project to Transmission Provider's transmission system in the Goshen/Rigby area as a small generation interconnection project. In addition, any existing outage limitations were studied. The study investigated transmission system impacts under two different loading conditions: Peak summer load conditions and spring load conditions. Both the existing transmission system and the proposed system with the Interconnection Customer s Generation Project added were studied. Transmission Provider determined that stability studies were not required due to the size of the project. This study addresses the proposed 19.5 MW output of the planned wind project per the customers interconnect request. Additionally, although this study considered deliverability of the power in the local area, the Interconnection Customer, or its agent, must apply for transmission service according the Transmission Provider s tariff in order to deliver energy from the project. Another deliverability study, and potential modifications to the transmission system, may be required at that time. 3.0 Type of Interconnection Service This section is not applicable to the interconnect request or the study. 4.0 Interconnection 4.1 Modifications and Additions to Facilities at Transmission Provider s Interconnection Location A facility will be built at the point of interconnection of the new 69kV line to the wind power project with the existing Transmission Provider s 69 kv line. The point of interconnection will consist of 3 three phase motor operated 69kV pole mounted disconnect switches, one switch in each of the three lines connected at that location. The Q0047 Page 2 4/28/2006
motor operators will be controlled remotely by the Transmission Provider s dispatcher via SCADA through a remote terminal unit (RTU) at that location. A single phase line to ground potential device will be connected at the point of interconnection and the secondary of the potential device will be connected to an analog point on the RTU. A communication link will be needed between the RTU and Transmission Provider s Salt Lake City control center. There is an existing communication system between Salt Lake City and Transmission Provider s major facilities in southeastern Idaho. For this project communication will be needed between the RTU and one of these existing facilities. 4.2 Additions Needed at the Interconnection Customer s Project Substation At the wind power project collector substation the 69kV line will be terminated into current transformers and potential transformer for interchange metering and a 69kV circuit breaker. The following one line diagram on the next page shows the interconnection. Q0047 Page 3 4/28/2006
Transmission Provider will design and build a panel with protective relays to detect faults on the 69kV system and to monitor the voltage and frequency at this location. If a line fault is detected the 69kV circuit breaker would be tripped. If the voltage or frequency of the system is outside of the normal range of operation a signal will be provided to trip the 14.4kV feeder breakers. Q0047 Page 4 4/28/2006
An RTU will be installed at the collector substation to monitor the following quantities: Status of the following: 69kV circuit breaker 14.4kV main transformer circuit breaker 14.4kV feeder circuit breakers Capacitor bank switch for each capacitor increment (if shunt capacitor banks are needed for voltage support) Trouble alarms from the 69kV line protection package Analog signals from the following: MWatts delivered at 69kV MVar delivered at 69kV Voltage at 69kV MWatts of each of the 14.4 kv feeders MVar of each of the 14.4 kv feeders MVar of shunt capacitor bank (if shunt capacitor bank is needed) Wind speed indicator at the site Energy pulse signals from the following: KWH delivered to the 69kV line KWH at each of the 14.4 kv feeders Telemetering equipment will be needed to send data to Transmission Provider s energy control center. Transmission Provider will need the ability to remotely access the fault data records that will be produced by the line protection relays. These records will be accessed via a dialup modem. A communication link will be needed from the collector substation to an existing Transmission Provider communication site. This communication link will carry signals for the RTU, telemetering transmitter, and the dialup modem for accessing relay fault records. 4.3 Power Flow Study The system configurations were studied with all lines in service (N-0) to determine if any normal loading problems are encountered for peak or minimum load conditions Several N-1 conditions (single line out of service) were studied to determine if any system problems exist due to outages. These conditions were evaluated for peak summer load conditions and for light load conditions. The following outages were conducted to determine any deficiencies in system performance: Q0047 Page 5 4/28/2006
Goshen Rigby 161 kv Line Outage Goshen - Sugarmill 161 kv Line Outage Rigby Sugarmill 161 kv Line Outage Rigby Jefferson 161 kv Line Outage Goshen Jefferson 161 kv Line Outage Goshen Eagle Rock 161 kv line Outage Westside Sugarmill 161 kv line Outage The Interconnection Customer s Project was modeled to the representation as shown on the next page. Q0047 Page 6 4/28/2006
Interconnection Schwendiman Wind Customer Project Area facilities Map Project Area Facilities Map 3-75 MVA Rigby 161 kv 69 kv 4.2 miles Ririe Southfork Ucon 2.1 miles 6.7 miles 1.3 miles 1.0 mile 3.0 miles Sugarmill 40 MVA 138 kv 69 kv Sandcreek 1.6 miles 3.2 miles 3.6 miles 3.0 miles Windfarm.95 mile Ammon 14.9 miles 75 MVA 69 kv Area Planning Wind.cdr 01204/05 Goshen 161 kv Q0047 Page 7 4/28/2006
The study assumed that the normal system open points for the 69 kv transmission system between Goshen, Rigby and Sugarmill would be maintained. This means that the new Wind Project would be served by a 12.6 mile radial feed from the Rigby substation. Heavy summer peak load conditions were modeled using the Transmission Provider B2003WSCC base case, with the Idaho area loads modified to reflect the 2004 heavy summer conditions. Spring load conditions were modeled by scaling the summer loads to 50%. The Wind Project was modeled as one large machine with various levels of VAR compensation, reflecting the range of reactive capabilities the GE machines are capable of. The equivalent model of the turbine involves modeling the generator as a fixed MW and MVAR device. Since Transmission Provider s interconnection requirements stipulate that the Interconnection Customer generation will maintain a power factor of +/- 95%, that range was assumed for these studies. The GE machines are capable of maintaining this power factor, so no additional capacitors were included in the model. 4.3.1 Existing System (Pre-Interconnection Customer Generation) No N-0 problems were identified under either Heavy or Light loading conditions. Area of lowest voltage during heavy load conditions was at Ucon sub (.971 pu). Areas of Highest voltage during light loading conditions were at the Rigby and Goshen 69 kv buses (1.041 pu). One N-1 problem was identified for the existing system. Since the Goshen - Rigby - Sugarmill 69 kv system is operated as three radial line taps, a line fault to the system on any one segment of line will cause an outage to all customers on that line segment. Manual switching will restore power to the out of service customers by utilizing the other two sources. Looping the three sources together has not been considered, due to the fact that the system does not have sectionalizing circuit breakers. With a paralleled system, any line fault to the combined, (much longer) looped transmission system would cause an outage to many more customers on the system. It would also take much longer to restore service, because of the need to patrol all three line segments to find the problem. 4.3.2 Post-Interconnection Customer Generation N-0 Heavy Summer conditions: Assuming a generation output of 19.5 MW, and a maximum power factor of 85% lagging (the maximum capability of the GE machine), no thermal or capacity limits were reached on any transmission line or substation transformer. Assuming summer peak loading conditions, the voltage at the Wind Project 69 kv bus, with no MW or MV generation was estimated to be.981 pu. Assuming a power factor Q0047 Page 8 4/28/2006
of +/- 95%, the voltage range of the Wind Project 69 kv bus moved from.992 pu to 1.026 pu. This means that there is the potential of a 4.5% voltage change to the Wind Project bus from maximum generation to no generation. The study shows Ucon, the closest Transmission Provider s load, has a maximum voltage change of 2.8%. N-0 Light Summer conditions: Assuming a generation output of 19.5 MW, and a maximum power factor of 85% lagging (the maximum capability of the GE machine), no thermal or capacity limits were reached on any transmission line or substation transformer. Assuming summer light loading conditions, the voltage at the Wind Project 69 kv bus, with no MW or MV generation was estimated to be 1.035 pu. At generation levels of 19.5 MW and assuming a power factor of +/- 95%, the voltage range of the Wind Project 69 kv bus moved from 1.041 pu to 1.075 pu. This means that there is the potential of a 4.0% voltage change to the Wind Project bus from maximum generation to no generation. The study shows Ucon, the closest Transmission Provider s load, has a maximum voltage change of 2.8% N-1 Heavy Summer conditions: As was mentioned above, since this Wind Project will be run on radial 69 kv transmission line, a line outage will drop the generation. A group of studies were also run by transferring the Wind Project to the 11.4 mile Sugarmill Sandcreek 69 kv source. Assuming a generation output of 19.5 MW, and a maximum power factor of 85% lagging (the maximum capability of the GE machine), no thermal or capacity limits were reached on any transmission line or substation transformer from this source. Assuming summer peak loading conditions, the voltage at the Wind Project 69 kv bus, with no MW or MV generation was estimated to be.981 pu. At generation levels of 19.5 MW and assuming a power factor of +/- 95%, the voltage range of the Wind Project 69 kv bus moved from.987 pu to 1.033 pu. This means that there is the potential of a 5.3% voltage change to the Wind Project bus from maximum generation to no generation. The study shows Sandcreek, the closest Transmission Provider load, has a maximum voltage change of 1.9%. N-1 Light Summer conditions: Since this Wind Project will be run on radial 69 kv transmission line, a line outage will drop the generation. A group of studies were also run by transferring the Wind Project to the 11.4 mile Sugarmill Sandcreek 69 kv source. Assuming a generation output of 19.5 MW, and a maximum power factor of 85% lagging (the maximum capability of the GE machine), no thermal or capacity limits were reached on any transmission line or substation transformer. Assuming summer light loading conditions, the voltage at the Wind Project 69 kv bus, with no MW or MV generation was estimated to be 1.014 pu. At generation levels of 19.5 MW and assuming a power factor of +/- 95%, the voltage range of the Wind Project 69 kv bus moved from 1.019 pu to 1.054 pu. This means that there is the potential of a 4.0% voltage change to the Wind Project bus from maximum Q0047 Page 9 4/28/2006
generation to no generation. The study shows Sandcreek, the closest Transmission Provider load, has a maximum voltage change of 1.3%. 4.4 Transmission Modifications 4.4.1 Existing Breaker Modifications Short-Circuit A fault analysis was performed using the computer software Aspen. 12 - GE 1.5 MW wind turbines connected through the 14.4kV collector system was added to the latest Aspen One-liner Base Case. The 14.4kV collector system was modeled using the information supplied by the developer which included a 69 14.4kV 15/20/25MVA transformer with an impedance of 8.0% on 15MVA base. Classical faults were simulated at several key locations. These faults were simulated to determine if the existing breakers had sufficient interrupting capacity. The following table lists the in fault duty on buses in the vicinity of the new generation facility. Interconnection Customer Generation Addition Substation Bus 3 phase fault Single line to ground fault Ammon 69kV 4170 A 3135 A Goshen 69kV 8736 A 10,586 A Rigby 69kV 10,361 A 12,506 A Ririe 69kV 2390 A 1825 A Sand Creek 69kV 3900 A 4215 A The study showed that no equipment will need to be replaced due to increased fault duty caused by the addition of the generation facility. 4.4.2 Protection Requirements The protection relay settings at Goshen Substation Circuit Breaker 78, Sugar Mill Substation Circuit Breaker 81, and Rigby Substation Circuit Breaker 72 will need to be reviewed to determine if the current protection provided is adequate with the addition of the tap line to the new wind power project. This review will be completed in the design phase of the project to determine any required relay settings changes at these locations. 4.4.3 Communication Requirements At the point of interconnection a pole mounted RTU including MAS remote radio and antenna will be installed to interface with the existing MAS master at the Mennan Butte site, and a RTU installed at the Customers switchyard. A microwave tower using T1 fractional wireless equipment is proposed for the Q0047 Page 10 4/28/2006
Customer s switchyard to carry the RTU, meter phone line, and telemetry signals to Transmission Provider s dispatch centers. 4.4.4 Revenue Metering Bi-directional revenue metering will be installed at the wind plant end of the 69 kv line. See one-line diagram on Page 4 of 12. The metering will use CTs that will be capable of accurately measuring the wide range of bi-directional power flows from max generation to no generation. The meter readings will be adjusted for losses back to the Point of Interconnection. 5.0 Voltage Fluctuations for Capacitor Switching This study assumed that any VAR needs would be supplied by the GE machines. As a result, no remote capacitor switching studies were included. 6.0 Transient Stability Studies No transient stability studies were required for this study and none were investigated due to the size of the project. 7.0 Conclusions: Based on the results of this study, the following recommendations are noted: During light loading conditions the Wind Project 69 kv bus could see voltage fluctuations that will exceed the Transmission Provider allowable voltage fluctuation maximum of 3.0%, if the Wind Project were to trip off at maximum generation levels. However, no Transmission Provider load bus would experience a violation of this flicker guideline, so no remediation is necessary. There were conditions discovered during light loading that could drive the Wind Project 69 kv bus to voltage levels as high as 107.5 pu, depending of the settings of their generators. It would be prudent for the Customer to consider tight voltage control settings to hold down the voltage. No Transmission Provider busses exceeded voltage levels of 1.05 pu. During a line outage of the Rigby - Sandcreek 69 kv line, all loads and generation will be lost. It is feasible by manual switching to temporarily transfer loads and generation to the Sugarmill Sandcreek 69 kv line. The wind plant must be designed to deliver power to the point of interconnection within the range of +/-95% power factor, with voltage control. The short circuit analysis did not find any existing breakers in the area that would require upgrading due to the additional short circuit duty caused by the wind plant. The configuration at the Point of Interconnection will include a pole-mounted three-way motor-operated switch and RTU, for remote operation. The 69 kv radial interconnecting line from the wind plant must include a 69 kv breaker at the wind plant end of the line. Transmission Provider will design and procure a relay Q0047 Page 11 4/28/2006
panel to be installed at the wind plant end of the line, to detect faults on the 69 kv system. Transmission Provider will design, procure and install an RTU at the wind plant to collect data which will be delivered to Transmission Provider s control center, via SCADA. The Customer will be required to deliver the data, listed in III.B to the RTU. At the point of interconnection a pole mounted RTU including MAS remote radio and antenna will be installed. A microwave tower using T1 fractional wireless equipment will be installed at the customer s collector station to communicate with Transmission Provider s control centers. Bi-directional revenue metering will be installed at the wind plant substation using 69 kv instruments. The meter will be adjusted for line losses back to the Point of Interconnection with Transmission Provider. Q0047 Page 12 4/28/2006