Procedure to Submit a RAS for AssessmentPage 1/16
Information Required to Assess the Reliability of a RAS
For all new or modified RAS, provide the following WECC RAS data base information as described in Attachment A of PRC-012 through 014 WECC-CRT-1 (also see Appendix A):
1)Reporting Party- San Diego Gas & Electric
2)Scheme Name- IV Gen DropRAS- TL50001, TL50003, TL50004 and TL50005
3)Classification: WAPS, LAPS, or SafetyNet- WAPS
a)Address whether failure of the RAS would violate the TPL-(001 thru 004) – WECC – 1 – CR System Performance Criteria (if it applies to the submitted RAS).
Failure to operatewould cause overloads in the CENACE 230kV system, and operation of CENACE RAS
b)Identify whether failure of the RAS would result in a maximum load loss ≥ 300 MW.
Failure to operatewould not result in a maximum load loss > 300 MW
c)Identify whether failure of the RAS would result in a maximum generation loss ≥ 1000 MW.
Failure to operate would not result in a maximum generation loss > 1000 MW.
4)Major WECC RAS (Yes or No, see WECC RAS data base or WECC PRC-003-1 Attachment B, Table 3)- No
5)Operating Procedure Name- TMC1505 – Protection Schemes
6)Design Objectives-When one of the two 500kV paths from Imperial Valley (IV) into San Diego is open, the RAS for the remaining 500kV path is enabled. For the loss of the remaining path, generation connected to the 230kV busses at IV is shed to prevent high flows through the CENACE 230kV system.
7)Operation-The open line path is detected, and instantaneous tripping of all connected generation is initiated.
8)Modeling-Under line-out conditions, the RAS is placed in service for the remaining line(s). For the loss of the remaining path, all connected generation is tripped via the RAS.
9)Proposed In-Service Date-TL50001 RAS has been in service since 2003. The TL50003 and TL50005 RAS were placed in service in Fall 2012. The TL50004 RASwas placed in service in June 2014.
Submitted by:Ahsan Mirza
System Protection and Control Engineering
San Diego Gas & Electric
8316 Century Park Ct
San Diego, CA 92123
858-541-5045
A.RAS PURPOSE AND OVERVIEW
1)Identify the ownership of the RAS (the Reporting Party).
San Diego Gas & Electric
2)Provide the name of the RAS, the purpose and the desired in-service date. Include the specific type of system problem(s) being solved, e.g. transient stability, thermal overload, voltage stability, etc.
TL50001, TL50003, TL50004 and TL50005 Gen Drop RAS, designed to limit flows through CENACE 230kV system, placed in service September 2003, Fall 2012 and June 2014.
3)Provide the owner’s classification of the RAS as a LAPS, WAPS, or SN.
WAPS
4)Provide the information required to populate the WECC RAS data base using the appropriate Excel spread sheet, PRC-013 template (available on the WECC web site). The specific data required is also listed in Appendix A.
Data Item / ExplanationReporting Party / San Diego Gas & Electric
Scheme Name / TL50001 Gen Drop RAS
TL50003 Gen Drop RAS
TL50004 Gen Drop RAS
TL50005 Gen Drop RAS
Classification / WAPS
Major WECC RAS / NA
Operating Procedure / TMC 1505
Design Objectives / Protect for high flows through CENACE 230kV system
Operation / If respective 500kV path opens, trip generation connected to the 230kV busses at IV.
Modeling / Generation shedding initiated when respective path opens.
Original In Service Year / 2003, 2012, 2014
Recent Assessment Group / SDG&E Transmission Grid Operations
Recent Assessment Date / 8/2017
RASRS Review Date / 3/2018
5)Provide the name(s) of person(s) within the owner’s organization who is(are) responsible for the operation and maintenance of the RAS.
Operation: John Baranowski, Manager Grid Control 619-725-8610
Maintenance: Tyge Legier, System Protection Maintenance Manager 858-541-5963
6)Provide a description of the RAS to give an overall understanding of the functionality and a map showing the location of the RAS. Identify other protection and control systems requiring coordination with the RAS. See “RAS Design”, below, for additional information.
The TL50001/TL50003/TL50004/TL50005 RAS monitors the two 500kV paths between Imperial Valley Substation and San Diego. When one path is open (either TL50001/TL50004 or TL50003/TL50005), the RAS’s for the remaining path are enabled. If the remaining path opens, the RAS detects the open path and initiates tripping of all generating sources connected to Imperial Valley Substation.
7)Provide a single line drawing(s) showing all sites involved. The drawing(s) should provide sufficient information to allow RASRS members to assess design reliability, and should include information such as the bus arrangement, circuit breakers, the associated switches, etc. For each site, indicate whether detection, logic, action, or a combination of these is present.
Schematic drawings are provided for:
- Drew 230kV Switchyard–(Logic)
- Silver Ridge DREW GEN 4Wind Plant- (Action)
8)Indicate the type of system reliability studies performed and a list of any that are in progress.
Power flow and voltage stability studies were performed to determine the requirements of the RAS.
9)Provide a discussion of the impact to the WECC power grid, including other protection and control systems that result from the actions taken by the proposed RAS and from its failure to operate as expected. Does a failure to operate or a misoperation impact an Intertie Path? If yes, what Intertie Path?
This RAS is provided for protection during the loss of the remaining 500kV path connected between SDG&E’s Imperial Valley 500/230kV Substation and the SDG&E load centers, when one path is out of service. The intent of this RAS is to prevent high flows through the CENACE East-West 230kV system for loss of the 500kV paths.
If this RAS fails to operate when required, the subsequent high flows through the CENACE system would operate existing RAS owned by CENACE. If there is a misoperation, generation would be dropped, but there will be no resultant impact outside of the SDG&E system.
B.RAS DESIGN
1)Describe the design philosophy (e.g. failure is to be a non-credible event).
A redundant System A/System B design is provided;the design philosophy is to establish that a failure of the respective RASis a non-credible event.
2)Describe the design criteria (e.g. failure of a single component, element or system will not jeopardize the successful operation of the RAS).
Failure of a single component, element or system will not jeopardize the successful operation of the RAS. Since geographic diversity is not provided for the communication circuits to the Gen Drop sites, a backup tripping strategy is employed to ensure that the generation is disconnected from the system during a RAS event.
3)RAS Logic - Provide a description of the RAS Logic in the form of written text, flow charts, matrix logic tables, timing tables, etc. as appropriate and identify the inputs and outputs. Provide appropriate diagrams and schematics.
When enabled, logic is provided to detect an open path condition (TL50001, TL50003, TL50004 or TL50005). When an open path is detected, generation shed outputs are provided to all generation sites that could add to the remaining flow through the CENACE 230kV system.
4)RAS Logic Hardware - Provide a description of the logic hardware (relay, digital computer, etc.) and describe how the RAS logic function is achieved.
At Imperial Valley 500/230kV Substation, for TL50004 and TL50005, 52b contacts and maintenance switches are used. For TL50001 and TL50003, SEL-311L and SEL-421 relays are used to process the open line indication.
Generation tripping outputs are provided from the SEL-3530 automation controller, and transmitted to the connected power plants. RFL-9745 teleprotection units are used to transmit output signals to TDM and CLR II plants, while SEL-3530 ports are used to transmit output signals to OCO GEN 1, DW GEN 1, DW GEN 2, DW GEN 3,DW GEN 4,IV GEN 3, ECO GEN 1, ECO GEN 2 and DU GEN 1. At TDM and CLR II, RFL-9745 teleprotection units receive the generation drop signals and provide inputs to SEL-351 relays, which serve as the RAS logic processors. At OCO GEN 1, DW GEN 1, DW GEN 2, DW GEN 3,DW GEN 4,IV GEN 3, ECO GEN 1, ECO GEN 2, BUE GEN 1 and DU GEN 1, SEL-2411 Automation Controllers are employed to receive the generation drop signals and issue the trip outputs.
5)Redundancy - Provide a discussion of the redundancy configuration and if appropriate, why redundancy is not provided. Include discussion of redundant:
a)Detection.
b)Power supplies, batteries and chargers.
c)Telecommunications (also mentioned in item 10d).
d)Logic controllers (if applicable).
e)RAS trip circuits.
Redundancy is provided by the use of two independent systems, designated A and B. Detection for each system is provided by line loss logic for TL50001, TL50003 (including 230kV TL23054 and TL23055), TL50004 and TL50005. There are two batteries at Imperial Valley, Suncrest,East County, Ocotillo and Drew Substations, with Battery #1 feeding System A and Battery #2 feeding System B. There are two SEL-3530 Automation Controllers at Imperial Valley, one for System A and one for System B. Redundant communication circuits are used for the Imperial Valley-Suncrest-Ocotillo-Sycamore Canyon circuits.
Redundant hardware is used to transmit gen drop signals from IV to the generating stations, but the communication circuits are not over geographically diverse paths. At each of the gen drop stations, redundant tripping hardware is provided. Where available, redundant trip coils are utilized, and breaker failure is provided. To mitigate for lack of redundancy,a scheme is provided to trip the associated line(s) at the source of the RAS signal in the event that the gen drop is not completed at the generating station.
6)Arming - Describe how the RAS is armed (i.e. remotely via SCADA, locally, automatic, etc.).
Local cutout switches are provided at Imperial Valley, Drew and Ocotillo Substations, and at the gen drop stations for System A and System B, and SCADA enable signals are provided via RTUs at Imperial Valley, East County, Drew and Ocotillo. For theRAS to be armed, the local cutout switch must be on AND the system must be enabled via SCADA. RTU status is provided for the enable/disable status of the systems, and for the state of the local cutout switches. There is no automatic arming for this RAS.
7)Detection - Define all inputs to the RAS for the scheme to perform its required purpose. Examples:
a)Devices needed to determine line-end-status such as circuit breaker (52 a/b contacts) and disconnect status.
b)Protective relay inputs.
c)Transducer and IED (intelligent electronic device) inputs (watts, vars, voltage, current).
d)Rate-of-change detectors (angle, power, current, voltage)
e)All other inputs (e.g. set points, time from a GPS clock and wide area measurements such as voltage angle between two stations).
f)Provide details of other remote data gathering or control equipment.
Line loss logic is provided via a combination of 52b breaker auxiliary switches, maintenance switches and breaker failure LOR contacts.
8)Coordination with Protection and Control Systems
Describe all protection and control systems interactions with the RAS, in addition to the RAS inputs described in (7) above.
a)System configuration changes due to RAS operation do not adversely affect protective relay functions such as distance relay overcurrent supervision, breaker failure pickup, switching of potential sources, overexcitation protection activation, or other functions pertinent to the specific relays or protection scheme.
b)If studies indicate that transient or sustained low voltages are expected in conjunction with elevated line flows during or after RAS operation, confirm that any protection settings on affected lines will not cause cascading outages related to the low system voltages.
c)Potential adverse interactions with any other protection or control systems.
The gen drop outputs will operate to remove generation that is connected radially from Imperial Valley, but this will not adversely affect protective relay functions for other facilities. Studies indicate that there will be no sustained low voltages during or after an operation of the RAS.
9)Multifunction Devices.
A multifunction device is a single device that is usedto perform the function of a RAS in addition to protective relaying and/or SCADA simultaneously. It is important that other applications in the multifunction device do not compromise the functionality of the RAS when the device is inservice or when is being maintained.
a)Describe how the multifunction device is applied in the RAS.
b)Show the general arrangement and describe how the multi-function device is labeled in the design and application, so as to identify the RAS and other device functions.
c)Describe the procedures used to isolate the RAS function from other functions in the device.
d)Describe the procedures used when each multifunction device is removed from service and whether any other coordination with other protection is required.
e)Describe how each multifunction device is tested, both for commissioning and during periodic maintenance testing, with regard to each function of the device.
f)Describe how overall periodic RAS functional and throughput tests are performed if multifunction devices are used for both local protection and RAS.
g)Describe how upgrades to the multifunction device, such as firmware upgrades, are accomplished. How is the RAS function taken into consideration?
There are two uses of multifunction devices in this RAS. At Suncrest, Ocotillo, East County and Imperial Valley Substations, the SEL-311L and SEL-421 relays used for line protection are also used to process and transmit open line detection for the RAS. The SEL-311L relays are used for System A, and the SEL-421 relays are used for System B. The second use of multifunction devices is the use of SEL-351 relays used for line protection of the radial lines to generation from Imperial Valley, Drew, Boulevard East and Ocotillo Substations. When a RAS signal is sent to radially connected generation, a timer is started in the associated line’s SEL-351 relay. If there is still incoming flow from generation when the timer cycle is completed, the SEL-351 issues a trip for the line.
For the first use noted above, there are only open-line detection outputs, and no associated generator trips. Therefore, there are no labeling or direct process outputs to discuss. For the second use with the SEL-351 relays, the tripping outputs and alarms are labeled.
10)Telecommunications.
a)Provide a graphical display or diagram for each telecom path used in the proposed RAS scheme, including extent of redundancy employed. See references. Indicate ownership of the circuits, paths, and segments. Indicate responsibility for maintenance. If a telecom circuit utilizes a public network, describemonitoring and maintenance agreements including repair response, details of availability, and how possible change of ownership is addressed. Describe maintenance agreements and response commitments when the RAS communication utilizes multiple private systems.
The SDG&E Enterprise Control Center (ECC) monitors the network communications equipment 24/7 and reports facility and equipment alarms to the respective operations and maintenance groups for restoration and repair services. The ECC monitors the circuits through the telecommunications multiplexer equipment status alarms. The RAS communicationsystem does not utilize multiple private systems.
b)Describe and list the telecommunications media and electronic equipment (e.g. microwave radio, optical fiber cable, multiplex node, power line carrier, wire pair, etc.) including redundancy employed in each telecom path. For each of the paths and segments ofthe RAS, identify the type of telecom equipment employed. For example, whether analog or digital licensed microwave radio, unlicensed spread spectrum radio, fiber optic SONET node, etc are applied.
Each A and B system communication circuit is connected to a TDM T1 multiplexer using a single 56k channel card, C37.94 interface adapter, and multimode fiber optic cable connection. The typical communication path utilizes TDM T1 and T2 multiplexers, DS-3/DS-1 DACS, and either fiber optic or licensed digital microwave radio equipment. Redundant equipment includes independent multiplexers at Imperial Valley, Ocotillo, Suncrest, Drew, Ocotillo, Dunaway, Boulevard East,TDM and CLR II.
c)Provide a description of common facilities used for each RAS telecom path and segment that are not specifically excluded from redundancy by the WECC critical communication circuit design guideline (e.g. towers, generators, batteries). Identify paths or segments routed through common equipment chassis such as Digital Cross-connect System, SONET node, or router. Identify physical media carried or supported by the same structure, such as a transmission line tower, pole structure, or duct bank. Discuss outside plant and inside plant routing diversity. See references.
Single OPGW fiber optic systems to CLR II, TDM, Drew, DW GEN 1, DW GEN 2, DW GEN 3,DW GEN 4,IV GEN 3, ECO GEN 1, ECO GEN 2, BUE GEN 1and DU GEN 1 support both RAS A and RAS B, although independent A and B hardware is used. To mitigate for single point of failure, a timer is started in the associated line’s SEL-351 relay whena RAS signal is sent to radially connected generation. If there is still incoming flow from generation when the timer cycle is completed, the SEL-351 issues a trip for the line.