Procedure to Submit a RAS for AssessmentPage 1/15
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- Imperial Valley Bank 80RAS
3)Classification: WAPS, LAPS, or SafetyNet- LAPS
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 notviolate TPL-(001 thru 004) – WECC-1-CR
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 500/230kV Bank 81 or Bank 82 is out of service at Imperial Valley (IV) Substation, the loss of the remaining Bank 81 or Bank 82can overload 500/230kV Bank 80. ARAS output is initiated to trip generation connected out of Imperial Valley Substation, reducing the loading on Bank 80 to a value less than 95% of the emergency rating.
7)Operation-The open bank/subsequent overload is detected, and sequential tripping of connected generation is initiated. When the overload drops out, RAS tripping is suspended.
8)Modeling-This RAS will normally be enabled. For the loss of Bank 81 and Bank 82 at Imperial Valley, and load exceeding 855 MVA on Bank 80, connected generation at DW GEN 1, DW GEN 2, DW GEN 3, DW GEN 4and IV GEN 3 is sequentially tripped via the RAS.
9)Proposed In-Service Date-This RASwas placed in service in November 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.
Imperial Valley Bank 80RASwasplaced in service in 2014.
3)Provide the owner’s classification of the RAS as a LAPS, WAPS, or SN.
LAPS
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 / IV Bank 80RAS
Classification / LAPS
Major WECC RAS / NA
Operating Procedure / TMC 1505
Design Objectives / Protect for 500/230kV Bank 80 overload at IV following the loss of 500/230kV Bank 81 and Bank 82
Operation / If Bank 81 and Bank 82 are open at IV, and Bank 80 overloads, generator tripping is initiated.
Modeling / Generation shedding initiated when remaining bank overloads.
Original In Service Year / 2014
Recent Assessment Group / SDG&E Transmission Grid Operations
Recent Assessment Date / 6/2014
RASRS Review Date / 7/2014, 11/2014 and 03/2018
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 IV Bank 80RAS monitors the 500/230kV transformers at Imperial Valley Substation. When armed, the RAS will detect Bank 81 and Bank 82 open and Bank 80 overloaded, and will initiate sequential tripping of generation in the Imperial Valley.
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.
Single line drawings are provided for:
- Imperial Valley500/230kV Substation- Detection and logic
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 one of the two 500/230kV banks at Imperial Valley, resulting in an overload of Bank 80. The intent of this RAS is to prevent high flows through Bank 80 at Imperial Valley Substation.
If this RAS fails to operate when required, the subsequent high flows through the remaining bank would persist until operator action is initiated to reduce bank loading. 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 500/230kV banks out of service condition at Imperial Valley(Bank 81and Bank 82). When a bank out condition is detected, and the remaining bank (Bank 80) is overloaded, sequential generation shed outputs are provided to all generation sites that could add to the remaining flow through the remaining bank.
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 Substation, SEL-387transformer differential relays are provided to providebank out and overload detection outputs. The bank outindications for Bank 81 and Bank 82are developed locally at Imperial Valley using 500kV and 230kV bank breaker 52b contactsand CB maintenance switches.
Also at Imperial Valley 500/230kV Substation, SEL-3530 and SEL-2440 Automation Controllers are provided to process the received RAS inputs. Generation sequential 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-2411 and SEL-2506 I/O modules are used to transmit output signals toDU GEN 1, DW GEN 1, DW GEN 2, DW GEN 3, DW GEN 4and IV GEN 3. 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 DW GEN 1, DW GEN 2, DW GEN 3, DW GEN 4 and IV GEN 3, 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. There are two batteries at Imperial Valley, 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 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 Miguel, Imperial Valley, Drew and Ocotillo. For theRAS to be armed, the local cutout switch must be on. RTU status is provided for the enable/disable status of the systems. 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.
Bank out logic is provided via a combination of 52b breaker auxiliary switches and maintenance switches.
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?
SEL-387 relays used for transformer bank protection are also used to detect overload conditions.
SEL-351 relays used for line protection of the radial lines to generation from Imperial Valley, Drew 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. The tripping outputs and alarms are labeled according to their RAS function.
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 public network lease 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 and Drew.
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 DU, DW and IV GEN 3 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.
d)Provide a discussion of communications system performance including, circuit or path quality in terms of availability. Provide details of reliability (e.g., availability of 99.95%), and other supporting reliability information such as equipment age, history, maintenance, etc. Telecommunication reliability information is the average overall percentage, and not point-to-point information. See references.
e)Provide a discussion about performance of any non-deterministic communication systems used (such as Ethernet). If RAS performance is dependent upon successful operation through a non-deterministic communications system or path, then describe how timing and latency issues will be addressed and verified. Include timing and latency planning or management and verification for initial commissioning and in the event of network modifications or additions. Identify which industry standard is applied.
Non-deterministic communication systems are not employed on this RAS.
f)Acknowledge provision of appropriate high voltage entrance protection if wire pairs are used.
High voltage protection equipment is not required for the communications associated with this RAS.
11)Transfer Trip Equipment - Identify the manufacturer and type (FSK audio tone, FS carrier, digital, etc.), and provide the logic configuration (dual channel, pilot tone, etc.). Identify whether internal device medium is used; e.g. “Relay-to-Relay” communication.
SEL mirrored bits are used for the gen drop signals to DU GEN 1, DW GEN 1, DW GEN 2, DW GEN 3, DW GEN 4 and IV GEN 3, processed via SEL-2411 automation controllers and SEL-2506 I/O controllers.
12)Remedial Actions Initiated - Provide a functional description of the action(s) produced by the scheme and include a simplified one-line diagram of the RAS output to the end-device operated by the scheme.
At the action substations, where gen drop is initiated, the total generation is dropped via the operation of three LOR relays on the RAS panels. At TDM and CLR II, the respective steam turbine or combustion turbines are dropped by the tripping of their associated circuit breakers. At DU GEN 1,DW GEN 1, DW GEN 2, DW GEN 3,DW GEN 4,and IV GEN 3, three RAS LOR relays each trip one-third of the solar inverters by operating the associated 34kV feeder breakers.
13)Remedial Action Schemes may have elements such as engineering access, routable protocols, and sensitive design documentation included in the design that require compliance with the NERC CIP Standards. Utilities may handle CIP compliance differently. Please providea high level overview of how your company’s CIP Compliance Program requirements are incorporated into this RAS design.