System Voltage Control Generator Set Point Normal voltage operation Capacitor These are the primary sources for voltage control Maintain Reserves SVC Reactors In many cases this is sufficient to ID: 771048
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System Voltage Control Generator Set Point
Normal voltage operation Capacitor These are the primary sources for voltage control Maintain Reserves SVC Reactors In many cases, this is sufficient to maintain voltage as the load changes
Capacitor SVC Reactors At other times, these resources are not enough to address all voltage conditions
Requires Additional Resources Key Factor: Maintain reserves on Generators In most cases, the final option is Autotransformer LTCs High Load Conditions These may vary in order based on system conditions and location Light Loads Conditions
Maintaining voltage within limits across the system during heavy load times may require maintaining voltage at the remote generator POI at 1.04 P.U. voltage Voltage 1.04 Voltage 1.04 Voltage 1.00 or less This requires units to be .95 PF Lagging to maintain this voltage level Managing System Voltage System voltage extends past the generator POI High Load Conditions
Maintaining voltage within limits across the system during light load times may require maintaining voltage at the remote generator POI at .98 P.U. voltage Voltage .98 PU Voltage .98 PU Voltages 1.04-1.05 This has requires units to be .95 PF Leading to maintain this voltage level Low Loads Conditions Managing System Voltage System voltage extends past the generator POI
Low Remote Voltage @ High Load Example
8 To Compensate for Increased Voltage Drop, Every Possible VAR Resource Across the Odessa Area was Used to Raise Voltage (Even Ones Far Away )
9 One Local Plant Happened to Be in the Right Grid Location to Raise Sagging Voltages West Texas Since we added all these VAR Resources, voltage is HIGH across the whole area. EXCEPT around North Andrews, where voltage sags.
10 System Conditions Required No Trees Plant to Be Operated at 1.04 pu Voltage to Maintain Area Voltages Within V SOLs North Andrews system voltage (red) 132 135 136 132 .96 PF .96 PF 1.04 pu Set Point No Trees Plant Set Point (blue) No Trees Reactive Output
11 Transmission Operator Responsibility NERC VAR‐001‐4 — Voltage and Reactive Control R3. Each Transmission Operator shall operate or direct the Real‐time operation of devices to regulate transmission voltage and reactive flow as necessary. It doesn’t say – e xcept every once in a while (it means 24/7/365) except in the parts of the grid that periodically have voltage problems except under worst system conditions
High Remote Voltage @ Light Load Example
System Conditions and Actions Taken 13 System Conditions at the Time : Lightest loads in the off-peak load season Load power factors minimum or injecting VARs Lightly loaded 345 kV lines ( miles) injecting large VARs into Northeast Texas area CREZ lines injecting 400 additional MVARs 3 AM Northeast Texas Generation OFF: Lamar , Tenaska Paris, Valley, Kiamichi and Panda ShermanMonticello 1-2 units out on Suspended Operation, Unit 3 on-lineDC Tie filter capacitors injecting 200 MVARs Sulphur Springs Reactor out on Forced Outage Voltage Control Actions Taken : Turned Capacitors OFF : Anna Sw., Krum West, Valley, Payne Sw., Monticello, even Dallas caps Turned Reactors ON : Krum West, Collin SES, Carrollton Northwest, Welsh Monticello, Paris Sw. Lowered Brown SVC voltage set point Requested DC Tie lower voltage Auto Taps do not help for this problem Lowered multiple Generators voltage set points in adjacent areas (even ones located far away) LAST- Removed Lines from Service : Kiamichi – Kiawa #2 345 kV Line Monticello – Farmersville #1 345 kV Line Northeast Texas Area
14 HIGH Voltages Across the Whole Area Remote Generator used to lower sagging voltages Highest voltage at Anna Sw.
15 At 2 AM, Anna Sw. Area Voltages are Approaching 362 kV and Outlying Generators are Asked To Lower Set Points .98 PF 1.005 pu Set Point Monticello Plant Set Point (blue) Anna Sw. system voltage (red)
16 At 3 PM, Lufkin Sw. Area Voltages are Approaching 362 kV and Outlying Generators Are Asked To Lower Set Points .96 PF 1.02 pu Set Point Tenaska Gateway Plant Set Point (blue) Lufkin Sw. system voltage (red) Freestone Plant Set Point (green)
Summary Generators shall be capable of providing .95 power factor for both leading and lagging, to maintain voltage within the set points between 1.04 and .98 PU for normal operation.