1 Description of Methodology for Volt / Var Optimization

Transcription

1 Methodology for Volt / Var Optimization on a Substation Basis May 13th, 2011 Version Methodology for Volt / Var Optimization (VVO) on a Substation Basis This use case discusses how the utility will implement VVO on a substation basis. This implementation requires the development of rules to narrow feeder voltage profile to operate within a specific voltage range. Once the voltage band has been sufficiently narrowed; a decision could then be made to implement Conservation Voltage Reduction (CVR) for the substation. 1.1 Narrative The Utility s Pilot Project will expand upon its Distribution Automation Project to include automatic voltage control capability on specific substations on a pilot and test basis. At a limited number of substations, the project will implement the coordinated operation of transformer load tap changer (LTC) controls, line voltage regulator controls (where already needed for operating reasons) and line capacitor bank controls to narrow feeder voltage ranges, and control distribution system voltage to within specific tolerances. The project will evaluate the feasibility of implementing real-time operational control capabilities regarding maintenance of system operating voltage and response to customer voltage variances. The project will also facilitate the experimental evaluation of CVR as a potential demand and energy conservation measure. The first Use Case associated with this project will develop a Methodology for VVO on a Substation Basis, establishing the functional requirements for an automated controller to meet the objectives outlined in the preceding paragraph. This use case has two scenarios. Scenario 1 discusses the Methodology for Voltage Narrowing on a Substation Basis. Scenario 2 discusses the Methodology for Conservation Voltage Reduction (CVR). VVO Substation V1.7.doc 1

2 Operations Substation Advanced Distribution Management System (Doesn t exist yet, but will in the future) 9 1 Load Tap Changer (LTC) Feeder Circuit Breaker Protective Relay Distribution Automation (DAC) Volt-VAR Optimization 7 RTU Field 5 6 Mid-Point Or Tie Recloser Line Capacitor Line Regulator Line Voltage Sensor Figure 1-1 Utility VVO Communications Diagram 1.2 Actor (Stakeholder) Roles Actor Name Actor Type (person, device, system etc.) Actor Description Interface Points Volt/Var Optimization (VVO) Line Capacitor Device Device Volt/Var Optimization is a device controlled and managed by D- and it interacts with RTUs and Field Devices. Responds to On/Off commands from the and reports status information, power system measurements, and alarms back to the. RTU Device Remote Terminal Unit. A microprocessor controlled device that interfaces field devices to 1) 9) DAC 4) 2) 7) LTC 8) Feeder VVO Substation V1.7.doc 2

3 Actor Name Actor Type (person, device, system etc.) Actor Description Interface Points Circuit Breaker Protective Relay Line Regulator Device Responds to set point commands from the and reports status information, power system measurements, and alarms back to the. 5) Midpoint or Tie Recloser Device A programmable circuit breaker designed to clear transient faults by opening on overcurrent and attempting one or more times to close, each time delaying for progressively longer. The programmed delays are a balance between minimizing outages and providing adequate time for the fault path to reacquire adequate dialectic strength, thus the progressive nature. 3) Load Tap Changer (LTC) Device Responds to set point commands from the and reports status information (tap position), power system measurements, and alarms back to the 7) RTU Line Voltage Sensor Device Device that measures loading of feeder line in specific T & D grid sectors of the utility 6) Feeder Circuit Breaker Protection Relay (Readings) Device Class of IED that responds to faults by tripping a breaker according to control logic, based on the monitoring of current and voltage values, and on communications with other Protective Relays. 8) RTU VVO Substation V1.7.doc 3

4 Actor Name Actor Type (person, device, system etc.) Actor Description Interface Points System Supervisory Control and Data Acquisition system The System retrieves data from the power system equipment, devices, and systems, and is used by operators and authorized applications to issue commands to power system equipment, devices, and systems. 1) VVO 9) DAC 3) Mid-Point or Tie Recloser 4) Line Capacitor 5) Line Regulator 6) Line Voltage Sensor 2) RTU DCO Operator Person An entity which carries the responsibility of operating an electricity distribution system 1.3 Object Name Object Description Format Poll of RTUs Poll of the RTUs DNP/IP DNP serial Feeder Circuit Breaker MW 3-Phase Protective Relay Feeder MVAR 3-Phase Readings Volts Amps Mid-Point or Tie Recloser Open/Close VVO Substation V1.7.doc 4

5 Object Name Object Description Format Status Volts Amps Block Automatic Operation Blocks automatic operation of a LTC or Line Regulator 2 Step by Step Analysis of Methodology for Voltage Narrowing on a Substation Basis Preconditions and Assumptions Actor/System//Contract Communications VVO LTC s, Line Regulator s, Line Capacitor s Line Regulator s and LTC s VVO Control Algorithms Field Devices Field Devices RTU Preconditions or Assumptions Communications are functioning normally Includes voltage narrowing and CVR Local control will be in place for the controllers when communications go down. Band center is 123 volts and the bandwidth is 3volts in non- CVR mode. (The bandwidth is volts to volts.) VVO Control Algorithms are trustworthy Field Devices are working properly Voltage measurement accuracy of Field Devices meets the minimum accuracy for which the voltage bands will be controlled. RTUs are scanned every 6-8 seconds Analogs are delivered every 20 seconds RTU is scanning the substation and feeder devices Cap Banks is polling RTUs Verification of Capacitor Bank operation is determined by measuring MVAR change following a command to open or close a bank. VVO Substation V1.7.doc 5

6 2.1.2 Steps Methodology for Voltage Narrowing on a Substation Basis Step # Additional Notes 1.1 An operational decision is made to implement Voltage Narrowing DCO initiates VVO for voltage narrowing polls RTU for Feeder Circuit Breaker Protective Relay Feeder Readings DCO VVO Initiate Voltage Narrowing RTU Feeder Circuit Breaker Protective Relay Feeder Readings Periodic Poll of field devices or Could be an alarm that triggers a poll RTU returns Feeder Circuit Breaker Protection Relay Feeder Readings to polls Mid- Point or Tie Recloser s to establish circuit topology returns Mid- Point or Tie Recloser Status to establish circuit topology RTU Feeder Circuit Breaker Protective Relay Feeder Readings Mid-Point or Tie Recloser s Mid-Point or Tie Recloser Status RTU Mid-Point or Tie Recloser s Status Periodic Poll of field devices or Could be an alarm that triggers a poll VVO Substation V1.7.doc 6

7 Step # Additional Notes 1.3 Blocks LTC s and Line Regulator s from automatic operation LTC s Line Regulator s Block Automatic Operation LTC s and Line Regulator s are blocked to prevent unnecessary operation (buck/boost) while the Power Factor is being corrected 1.4 Blocks Automatic Operation Line Cap Bank s to Remote Control Line Cap Bank s Block Automatic Operation 2.1 Perform Feeder PF correction based on feeder vars. Start with feeder 3 phase total MVAR and Voltage measurements from Capacitor Bank s Correcting PF to as close to unity as possible with capacitor bank controllers based on lowest voltage on the feeder 2.1A.1 If start of feeder 3 phase total MVAR is lagging greater than 50% of KVAR rating of the cap bank with the lowest operating voltage among those that are currently off, then turn it on if it has been off for greater than 5 minutes (via VVO control). VVO Substation V1.7.doc 7

8 Step # Additional Notes 2.1A.2 If Line Capacitor change command was initiated, wait 30 seconds and verify feeder MVAR have changed to determine if a capacitor bank operation occurred 2.1A.3 Repeat step until all Line Capacitor s are On or PF is met on the feeder 2.1A.4 Do not enable Automatic Operation of Capacitor Bank s 2.1B.1 or If start of feeder 3 phase total MVAR is leading greater than 50% of KVAR rating of the cap bank with the highest operating voltage among those that are currently closed, then turn it Off. (via VVO control). 2.1B.2 If cap bank change command was initiated, wait 30 seconds and verify feeder MVAR have changed to determine if a cap bank operation occurred 2.1B.3 Repeat previous two steps until all Line Capacitor s are Off or PF is met on the feeder Change Command Open/Close 30 second wait allows time to detect MVAR change following change command 30 second wait allows time to detect MVAR change following change command VVO Substation V1.7.doc 8

9 Step # Additional Notes 2.1B.4 2.2C.1 or Do not enable Automatic Operation of Capacitor Bank s If PF is OK, go to step Perform LTC Bus Voltage correction Unblock LTC s to allow Automatic Operation to drive substation bus voltage to setpoint Line Drop Compensation (LDC) is disabled on the LTCs 3.2A.1 3.2B.1 or LTC steps up if the voltage is low LTC steps down if the voltage is high 3.3 Wait 30 seconds to allow LTC to operate 3.4 Leave LTC controller in Automatic Operation mode. 4.1 Perform Voltage regulation via Line Regulator s for feeder voltage correction VVO Substation V1.7.doc 9

10 Step # Additional Notes Sequentially unblock Line Regulators s from Automatic Operation, starting at the head of the feeder and let them automatically correct the voltage 4.2A.1 4.2B.1 or Line Regulator steps up if the voltage is low Line Regulator steps down if the voltage is high 4. 3 Wait 30 seconds (at each Line Regulator ) to allow the Line Regulators s to operate Wait 30 seconds to allow Line Regulator controllers to perform step functions 4. 4 Leave Line Regulator s in Automatic Operation mode. 5.1 Perform Line Regulator operation based on local voltage requirements Allow RTU/ to update VVO Substation V1.7.doc 10

11 Step # Additional Notes If any of the scanned voltages on the secondary side are still low and If the effected regulator setpoint is between 121.5v and 123v, place effected Line Regulator in Remote Operation 5.13 Raise the Line Regulator 1 step Each regulator step will raise the voltage.75v Wait 30 seconds to allow the Line Regulator s to operate If any of the scanned voltages on the secondary side are still low and If the effected Line Regulator is setpoint s between 121.5v and 123v, raise the Line Regulator 1 step Wait 30 seconds to allow the Line Regulator to operate 5.3 Voltage conditions lower than desired range after previous adjustments lead to design work on the feeder. VVO Substation V1.7.doc 11

12 Step # Additional Notes 5.4 Place Line Regulator in Automatic Post-conditions and Significant Results Actor/Activity VVO Control Post-conditions Description and Results VVO Control can implement voltage narrowing on a substation level. 3 Step by Step Analysis of Methodology for CVR on a Substation Basis Preconditions and Assumptions Actor/System//Contract Communications VVO LTC s, Line Regulator s, Line Capacitor s Line Regulator s and LTC s VVO Control Algorithms Field Devices Field Devices RTU Preconditions or Assumptions Communications are functioning normally Includes voltage narrowing and CVR Local control will be in place for the controllers when communications go down. Band center is 123 volts and the bandwidth is 3volts in non- CVR mode. (The bandwidth is volts to volts.) VVO Control Algorithms are trustworthy Field Devices are working properly Voltage measurement accuracy of Field Devices meets the minimum accuracy for which the voltage bands will be controlled. RTUs are scanned every 6-8 seconds Analogs are delivered every 20 seconds RTU is scanning the substation and feeder devices VVO Substation V1.7.doc 12

13 Actor/System//Contract Cap Banks Preconditions or Assumptions is polling RTUs Verification of Capacitor Bank operation is determined by measuring MVAR change following a command to open or close a bank Steps Methodology for CVR on a Substation Basis Step # Additional Notes 6.0 An operational decision is made to implement Conservation Voltage Reduction Upon completion of Scenario Drop the setpoint by.5 volts Volt/Var Volt/Var Internal VVO Function Volt/Var sends new setpoints to LTC s and Line Regulator s Volt/Var LTC s and Line Regulator s New Setpoints Go through Scenario 1 (Voltage Narrowing) with new setpoints Wait for next readings to update Normal Poll Check for violations of minimum voltage criteria. Possible Voltage Alarms from If all voltage criteria are met move to VVO Substation V1.7.doc 13

14 Step # Additional Notes Drop the setpoint by.5 volts Volt/Var Volt/Var Internal VVO Function Volt/Var sends new setpoints to LTC s and Line Regulator s Volt/Var LTC s and Line Regulator s New Setpoints Go through Scenario 1 (Voltage Narrowing) with new setpoints Wait for next readings to update Normal Poll Check for violations of minimum voltage criteria. Possible Voltage Alarms from If all voltage criteria are met move to Drop the setpoint by.5 volts Volt/Var Volt/Var Internal VVO Function Volt/Var sends new setpoints to LTC s and Line Regulator s Volt/Var LTC s and Line Regulator s New Setpoints Go through Scenario 1 (Voltage Narrowing) with new setpoints Wait for next readings to update Normal Poll VVO Substation V1.7.doc 14

15 Step # Additional Notes Check for violations of minimum voltage criteria. Possible Voltage Alarms from If all voltage criteria are met move to Repeat cycle as desired for CVR Post-conditions and Significant Results Actor/Activity VVO Control Post-conditions Description and Results VVO Control can implement CVR on a substation level. VVO Substation V1.7.doc 15

16 4 Diagrams Scenario 1 Voltage Narrowing Sequence Diagram VVO Substation V1.7.doc 16

17 Scenario 2 Conservation Voltage Reduction Sequence Diagram 5 Auxiliary Issues 5.1 Parking Lot Items No Description 1 What protocol are the controllers talking? DNP? 2 What data/protocol does send to the VVO? DNP? 3 VVO must talk the same protocol as the controllers/. DNP? 4 How do I know what field devices are incorporated on the circuit? Does the VVO have an accurate system model to load? Do I scan the feeders and look for an open recloser? 5 What is the accuracy of the measurements coming back from? 6 How long does the condition need to exist? VVO Substation V1.7.doc 17

18 5.2 Revision History No Date Author Description B.D. Green Original Use Case B.D. Green Incorporate team input B.D. Green Add EPRI team notes B.D. Green Add new communications diagram and team comments B.D. Green Add team comments B.D. Green Add Diagrams B.D. Green Prepare for use case repository B.D. Green Clarification in Notes VVO Substation V1.7.doc 18