Control Brad Calhoun Consultant Sr Trainer Spring 2016 Introduction Voltage control in an electrical power system is important for proper operation of electrical power equipment to prevent damage such as overheating of generators and motors to reduce transmission losses and to maintai ID: 539373
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Slide1
Voltage
Control
Brad
Calhoun
Consultant, Sr.
Trainer
Spring 2016Slide2
Introduction
Voltage control in an electrical power system is important for proper operation of electrical power equipment, to prevent damage such as overheating of generators and motors, to reduce transmission losses, and to maintain the ability of the system to withstand and prevent voltage collapse. In general terms, decreasing reactive power causes voltage to fall while increasing it causes voltage to rise. A voltage collapse occurs when the system try's to serve much more load than the voltage can support.
2Slide3
3
Objectives
Identify the coordination of efforts between TOPs and QSEs necessary to maintain the voltage profile within established limits ensuring reliable operations.
Given a list of reactive and voltage control devices, identify each as a dynamic or static device and state its purpose in maintaining an adequate supply of reactive reserve.
Identify the NERC Reliability Standards, ERCOT Protocols, and ERCOT Guides requirements governing activities that ensure an adequate supply of reactive reserves ensuring reliable operations.Slide4
Dynamic Reactive
ReservesGenerators are the only true sources of reactive power4Slide5
5
Dynamic Reactive Reserves
Static reactive devices will be managed to ensure that adequate dynamic reactive reserves are maintained at all times.
Nodal Operating Guides 2.7.2 Maintaining Voltage Profile
ERCOT, in coordination with TSPs, shall deploy static Reactive Power Resources as required to continuously maintain dynamic reactive reserves from QSEs, both leading and lagging, adequate to meet ERCOT System requirements.
3.15.1 ERCOT Responsibilities Related to Voltage Support
Each TSP, under ERCOT’s direction, is responsible for monitoring and ensuring that all Generation Resources required to provide VSS dynamic reactive sources in a local area are deployed in approximate proportion to their respective installed Reactive Power capability requirements.
6.5.7.7 Voltage Support Service Slide6
6
Automatic Voltage RegulatorSlide7
7
Automatic Voltage Regulator
Dynamic
reactive device
The automatic voltage regulator (AVR) senses the voltage level at the generator terminals via a potential transformer (PT).
If the measured voltage is lower than the set point, the AVR will cause the excitation system to increase the DC excitation current. This DC current is applied to the generator's rotor field winding. If the voltage measured is higher than the set point, the excitation system will lower the DC excitation current applied to the field winding
.Slide8
8
Synchronous CondenserSlide9
9
Synchronous Condenser
Dynamic
reactive device
A synchronous condenser is very similar to a synchronous generator with the exception that it is not capable of producing any active power. It produces only reactive power. Synchronous condensers do not need a prime mover (steam or water turbine) as they are operated like a motor. The power system supplies the active power to turn the rotor. An excitation system is used to control the amount of MVAR produced by the synchronous condenser. Slide10
10
Static VAR CompensatorsSlide11
11
Static VAR Compensators
Dynamic
reactive device
A power quality device, which employs power electronics to control the reactive power flow of the system where it is connected. As a result, it is able to provide fast-acting reactive power compensation on electrical systems. In other words, static VAR compensators have their output adjusted to exchange inductive or capacitive current in order to control a power system variable such as the bus voltage.
Flexible AC Transmission Systems (FACTS) improve transmission quality and efficiency of power transmission by supplying inductive or reactive power to the grid.Slide12
Static
Reactive ReservesExtending the range of dynamic reactive resource response
12Slide13
13
CapacitorsSlide14
14
Capacitors
Static
reactive device
Capacitors are defined as two conductors separated by an insulating medium. These devices store, and later return, electrical energy to the system.
Since capacitors store reactive power, they may be viewed as sources of reactive power. Capacitors can be connected to the power system in either a shunt or a series connection. Shunt capacitors are used to supply reactive power to the system. Series capacitors are used to reduce the impedance of the path in which they are inserted
.Slide15
15
Correcting the Power FactorSlide16
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Capacitor Application
Restores dynamic reactive reserves
Coordinate with resources
Unloads transmission facilities
Location of CapacitorsSlide17
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ReactorsSlide18
18
Reactors
Static
reactive device
a coil or other component that provides inductive reactance in a circuit.
Reactors can be viewed as absorbers or sinks of reactive power. Reactors can be connected to the power system in either a shunt or a series connection. Shunt reactors are used to absorb reactive power from the system. Series reactors are used to increase the reactance of the path in which they are inserted
.Slide19
19
Transmission LinesSlide20
20
Transmission Lines
Surge Impedance Level (SIL)
Ferranti Rise
Line SwitchingSlide21
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CREZ
Reactive Compensation Requirements (cover wind output from 1979MW to 12036MW from CREZ)
Nine 345kV 50% series compensated lines
~1400MVAr dynamic reactive devices
~900MVAr shunt capacitor
~3000MVAr shunt reactorSlide22
Coordination of Efforts
Reliable Operations
22Slide23
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Participation
Each TSP, under ERCOT’s direction, is responsible for monitoring and ensuring that all Generation Resources required to provide VSS dynamic reactive sources in a local area are deployed in approximate proportion to their respective installed Reactive Power capability requirements.
6.5.7.7 Voltage Support Service
Power
FactorSlide24
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Voltage Profile
ERCOT in coordination with the Transmission Service Providers (TSPs) shall establish and update, as necessary, the ERCOT System Voltage Profile for all Electrical Buses used for Voltage Support in the ERCOT System and shall post all Voltage Profiles on the Market Information System (MIS) Secure Area. ERCOT may temporarily modify its requirements based on current system conditions.
3.15 Voltage
SupportSlide25
25
TSP versus QSE/GO lingo barrier
Boost or Buck
Lead or Lag
Positive or Negative
Voltage Set Point
Keep it Simple
Dispatch Instructions
Raise the voltage by XXX volts
Lower the voltage by XXX voltsSlide26
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Benefits of Healthy Voltage Profile
Reduces transmission lo
$$
es
Improves system security
Reduces system loading
MVA
TransformerSlide27
Regulatory Requirements
The Rules of the Road
27Slide28
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Voltage Ride-Through
Generation Resources
must be designed
and generation voltage relays must be set
to remain connected
to the transmission system during the following operating conditions:
Generator terminal
voltage deviations
exceed 5% but are within 10% of the rated design voltage and persist for less than ten seconds;
Generator
volts per hertz
conditions are less than 116% of generator rated
design voltage and frequency
and last for less than 1.5 seconds;
A
transmission system fault
(three-phase, single-phase or phase-to-phase), but not a generator bus fault, is cleared by the protection scheme coordinated between the Generation Entity and the Transmission Service Provider (TSP) on any line connected to the generator’s transmission interconnect bus, provided such lines are not connected to induction generators described in paragraph (9) of Protocol Section 3.15, Voltage Support;Slide29
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NERC PRC Standards
PRC-025-1— Generator Relay
Loadability
–
During the recoverable phase of a disturbance
, the disturbance may exhibit a “voltage disturbance” behavior pattern, where
system voltage may be widely depressed and may fluctuate
.
To
prevent unnecessary tripping
of generators during a system disturbance
for conditions that do not pose a risk of damage
to the associated equipment
Apply settings
that are in accordance with PRC-025-1 – Attachment 1: Relay Settings,
on each load-responsive protective relay
while maintaining reliable fault protection.Slide30
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NERC VAR Standards
VAR-001-4 — Voltage and Reactive Control
R1. …specify a system voltage schedule
R2. …schedule sufficient reactive resources
R3. …operate or direct the operation
R4. …specify the criteria that will exempt generators
R5. …specify a voltage or Reactive Power schedule
R6, …necessary step-up transformer tap changes and the implementation scheduleSlide31
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NERC VAR Standards
VAR-002-4 Generator Operation for Maintaining Network Voltage Schedules
R1. …operate each generator in the automatic voltage control mode
R2. …maintain the generator voltage or Reactive Power schedule
R3. …notify its status change on the AVR, power system stabilizer, or alternative voltage controlling device
R4. …notify its change in reactive capability
R5. …provide tap settings, fixed tap ranges, and impedance data
R6. …ensure that transformer tap positions are changed according to the specificationsSlide32
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ERCOT Guides
in order to prevent one Entity from
being a burden
to another
The operation of all Reactive Power devices under the control of a TO or a Qualified Scheduling Entity (QSE) will be coordinated under the direction of ERCOT to maintain transmission voltage levels within normal limits and post-contingency voltages within post contingency limits.
Static reactive devices will be managed to ensure that adequate dynamic reactive reserves are maintained at all times
.
the response (within the operating Reactive Power capability of the Generation Resource) must be sufficient to
initiate response in no more than one minute and return the measurement within the required range in no more than five minutes
within
2%
of the voltage profileSlide33
33
Summary
Healthy Voltage Profile
Coordinated Effort
Active Participation
Communication Slide34
34
Resources
NERC Reliability Standards
ERCOT Protocols
Nodal Operating Guides
Siemens USA
Electrical Engineering Portal
All About Circuits
How Stuff Works