- A Smart Grid is a power generation and distribution network based on two-way communication among all entities involved in the power market. It integrates large, centralized generation units and small, decentralized ones, along with consumers, into an overall structure. Advanced sensors that expand the automation structure, and a decentralized information and communications structure, are two of the factors that make this possible. These requirements enable the Smart Grid to increase the efficiency, reliability and security of the power supply chain. Another critical aspect of the Smart Grid system is that it allows end consumers to actively participate in the energy market and thus make a contribution to climate protection (from Siemens Website).
- SMART GRID is the transmission and distribution power grid of the future. Electrical grids need to deliver more energy, with greater flexibility, and in a more complex environment - but with the same infrastructure - going from today's one-way centralized electricity network towards a dynamic and bidirectional flow of energy and data (from Areva's Website).
- Why do you need a Smart Grid?
- The world has to face unprecedented energy challenges: climate change, population growth, and a rising demand for energy. And the world is increasingly looking to the electric power industry for solutions. Regulation policies are put in place to meet demanding climate protection aims. On the other hand, the existing grid structure is aging and often already being strained to the limit. Liberalized markets and increasing energy trade is putting further stress on the grids, particularly where power systems meet at national borders. Above that, the further increase of fluctuating infeed from distributed, small-scale renewable generation makes it more difficult to keep grids stable. In short, today’s grids, a 20th century infrastructure, have to cope with the challenges of the 21st century. To master these challenges successfully, it is time for these grids to turn smart.
- A true smart grid will integrate advanced intelligence from the customer to the generator and everywhere in between
- A smart will be:
o Largely self healing
o More flexible
o More reliable
o Safer - A smart grid will integrate thousands of IEDs sending and analyzing millions of pieces of data per minute to produce actionable information – and using that information to control the electric system
- The self healing grid:
o A self healing smart grid will prevent large scale regional outages by responding much more quickly than humans
o The integrated and interconnected IEDs of the smart grid will:
§ Identify
§ Analyze
§ Isolate
§ Remediate § Report - The flexible grid:
o By adding much more sophisticated intelligence and control, the smart grid will allow:
§ Higher transmission transfer capacity
§ Integration of more renewable/intermittent resources
§ More efficient and effective maintenance practices
§ Faster restoration when outages are unavoidable
§ More customer choice and energy self-determination. - The reliable grid:
o The smart grid will improve reliability by:
§ Reconfiguring the system within cycles
§ Isolating unavoidable outages to smaller areas
§ Enabling repair crews to precisely identify and geographically target problems quickly and efficiently. - The Safer Grid:
o The smart grid will be safer for workers and the public by:
§ Detecting many problems before catastrophic failure
§ Replacing oil-filled equipment with solid dielectric (trafo) or vaccum-operated components (fault interrupters)
§ Preventing equipment overloads (eg. Fault current limiters)
§ Placing more failure prone equipment above ground
§ Better equipping workers to avoid danger
- Links on Smart Grid and Related Terms:
- Power Systems Engineering Research Center (this link has various papers from UIUC and Carnegie Mellon Univ. http://www.pserc.org/ecow/get/publicatio/2009public/
- Paper1: When Grids Get Smart http://www.abb.com/search.aspx?q=smart%20grid&abbcontext=products
- Smart Grid http://en.wikipedia.org/wiki/Smart_grid
- Micro combined heat and power or microCHP is an extension of the idea of cogeneration to the single / multi family or small office building. http://en.wikipedia.org/wiki/Micro_combined_heat_and_power
- The second law of thermodynamics is an expression of the universal principle of increasing entropy, stating that the entropy of an isolated system which is not an equilibrium will tend to increase over time, approaching a maximum value at equilibrium. http://en.wikipedia.org/wiki/Second_law_of_thermodynamics
- http://intelligrid.epri.com/technical_results.html
- http://www.smartgrids.eu/ (November 2007)
- Smart Grid Solutions from IBM http://www.ibm.com/ibm/ideasfromibm/us/smartplanet/topics/utilities/20081124/index.shtml?ca=agus_aosbrsp-20090225&me=psearch&met=google&re=smart_grid_mkwid_lb060109a25106_3591611777&s_tact=usswk001&cm_mmc=agus_aosbrsp-20090225-usswk001-_-psearch-_-google-_-smart_grid_mkwid_lb060109a25106_3591611777
- http://www.oe.energy.gov/smartgrid.htm
- Smart Grid Information
https://www.energy.siemens.com/cms/00000105/en/smart_grid_information/Pages/Default.aspx - HMI Report Smart Grid
https://www.energy.siemens.com/cms/00000105/en/smart_grid_information/Pages/hmi_smart_grid_en.aspx - Bridges to the Future, Part I: The Smart Grid http://www.youtube.com/watch?v=wzFGLCRMdCU&feature=PlayList&p=4A2955A2DC5E4767&index=1
- Augmented Reality: See How It Works http://ge.ecomagination.com/smartgrid/?c_id=googsmartgrid#/augmented_reality
- Scarecrow - a GE ad Focuses on Smart Grid Technology http://www.youtube.com/watch?v=m1XqLPa9BoA
- A Smart Grid for Intelligent Energy Use http://www.youtube.com/watch?v=YrcqA_cqRD8&feature=PlayList&p=4A2955A2DC5E4767&index=0&playnext=1
- The Electric Grid of the Future (Presenation by James A. Kelly, Vice President, Engineering and Technical Services in the T&D Business unit of Southern California Edison (SCE) http://www.youtube.com/watch?v=e0P8Q4bKIc4&feature=related
- What Exactly is a Smart Grid? President Obama has been talking about the need for a smart grid to help keep America sustainable and competitive and in fact, the current proposed economic stimulus package ... http://www.youtube.com/watch?v=aDUmcvg3AZE&feature=fvw
- Killers Apps for the Smart Grid http://www.youtube.com/watch?v=M8WuHjLPz2U&feature=related
- 2 Time-delay
- 12 Overspeed
- 14 Underspeed/ Locked Rotor Protection
- 21 Distance
- 21N Distance Protection, Earth
- 21FL FaultLocator
- 25 Synchronism-check
- 26 Overtemperature
- 27 Undervoltage
- 30 Annunciator
- 32 Directional power
- 37 Undercurrent or underpower
- 38 Bearing
- 40 Field
- 46 Reverse-phase or Negative Sequence
- 47 Phase-sequence voltage or Negative sequence voltage
- 49 Thermal
- 50 Instantaneous overcurrent
- 51 AC time overcurrent or Inverse time overcurrent
- 51G Inverse time earth fault overcurrent
- 51N Definite time earth fault overcurrent
- 51V Voltage restrained/controlled overcurrent
- 55 Power factor
- 59 Overvoltage
- 59N Neutral Point Displacement
- 60 Voltage balance
- 63 Pressure
- 64 Apparatus ground or Earth-Fault
- 67 AC directional overcurrent
- 67N Directional Earth Fault
- 68 Blocking
- 69 Permissive
- 74 Alarm
- 76 DC overcurrent
- 78 Out-of-step or Phase angle
- 79 AC reclosing or Autoreclose
- 81 Frequency
- 81U Underfrequency
- 81O Overfrequency
- 85 Carrier or pilot-wire
- 86 Lock out
- 87 Differential
- 94 Tripping
Question Bank # 2:
- 3 things affect the selection and application of Overcurrent protective devices:
a. Current path
b. Current magnitude
c. Current type - Types of current:
a. Normal current
b. Overload current
c. Short-circuit current
d. Ground-fault current - Normal Current:
a. Normal Current or Load is defined as current drawn by a load under normal, operating conditions. Depending upon the nature of the load, current may vary from low values to full load values (also known as full load ampere FLA values or maximum load current).
b. Normal current flows only in the normal circuit path. The normal circuit path includes the phase and neutral conductors. It does not include equipment grounding conductors.
c. e.g. Motor. Normal motor current varies from low values (under light loading) to medium values (under medium loading) to high values (under maximum loading). - Overload Current:
a. Greater in magnitude then normal current but less then LRA (locked rotor amperes / current) and flows in normal circuit path.
b. Commonly caused by overloaded equipment, single-phasing, or low line voltages
c. E.g. Motor starting current. - Locked Rotor Current:
a. Motor starting current is called locked-rotor current and is included on the motor nameplate as LRA (Locked-Rotor-Amperes).
b. Motor starting current is a function of the motor design and can be as high as 20 times FLA. - Short Circuit Current:
a. Greater than Locked Rotor Current and may range upwards of thousands of amperes.
b. Maximum value is limited by the maximum short-circuit current available on the system at the fault point.
c. Includes two or more phase conductors; line-to-line faults of two-phase conductors (A-B, B-C, C-A) or 3 phase faults (A-B-C).
d. Classified further as:
-Bolted Short circuit current
-Arcing Short circuit current - Bolted Short circuit current:
Phase to phase faults, phase conductors becoming solidly connected together. - Arcing Short circuit current
a. Results from loose connections or insulation failure.
b. Current flows through loose connections
c. Arc presents impedance to the flow of current, smaller current will flow into an arcing fault compared to bolted fault. - Ground Fault Current:
a. any current which flows outside the normal circuit path.
b. In low voltages: current flow in the equipment grounding conductor. Detecting is a problem because of low level arcing ground faults.
c. In medium / high voltages: ground fault current may return to the source through the earth. Ground current relays are used for detection.
d. Classified further as:
-Leakage Ground Fault Current
-Bolted Ground Fault Current
- Arcing Ground Fault Current - Leakage Ground Fault Current:
a. Low magnitude current (mA range) associated with portable tools and appliances.
b. Caused by insulation failure and is a serious shock hazard.
c. Protection by using ground-fault circuit interrupter (GFCI). - Bolted Ground Fault Current:
a. When phase conductors become solidly connected to ground i.e. Ph-G, 2Ph-G, 2Ph-G.
b. If solidly grounded system, bolted ground fault current exceeds 3Ph bolted short circuit current.
c. Protection by using standard phase and ground Overcurrent devices. - Arcing Ground Fault Current
a. Depending upon the arc impedance, arcing ground-fault current may be as low as several amperes or as high as 20-38% of three phase, bolted short circuit current on a 480V system.
b. Due to ionization of the air, arcing ground faults may escalate into Phase-to-phase or three-phase faults.
c. Protection by using ground-fault protective (GFP) devices. - Sources of Short Circuit Current:
a. Synchronous generator
b. Synchronous motor
c. Induction motor
d. Supply transformers - Synchronous generator
a. When a Short Circuit occurs downstream of a synchronous generator, the generator may continue to produce output voltage and current if the field excitation is maintained and the prime mover continues turning the generator at synchronous speed.
b. The flow of SCC from the generator into the fault is limited only by the generator impedance and downstream circuit impedances.
c. The magnitude of generator fault current depends on the armature and field characteristics, the time duration of the fault and the load on the generator.
d. The ability of a generator to supply current during a fault is a function of the excitation system. - Synchronous motor (SM)
a. When a Short Circuit occurs upstream of a synchronous motor, the system voltage goes to zero, and motor begins losing speed.
b. As the motor slows down, the inertia of the load is actually turning the motor and causing it to act like a generator.
c. The synchronous motor has a dc field winding and delivers a SCC into the fault until the motor completely stops.
d. SCC is limited by SM impedance and the circuit impedance between the motor and the fault. - Induction motor (IM):
a. When a Short Circuit occurs upstream of an induction motor, produces same effect as SM.
b. Since the IM has no dc field winding, there is no sustained field current in the rotor to provide flux as is the case with a SM.
c. SCC decays very quickly. - Supply Transformers:
a. Not sources of SCC
b. Trafo impedances limit the amount of SCC. - Standard tolerance on impedance is ±7.5% for two winding trafo and ±10% for 3 winding trafo.
a. Minus tolerance is used for SCC studies
b. Plus tolerance is used for load flow and voltage regulation studies. - 3 values of reactances are assigned to rotating machines for the purpose of calculating short-circuit current at three specified times following the occurrence of fault. Because SCC from rotating machines varies with time.
These three values are:
a. Subtransient reactance
b. Transient reactance
c. Synchronous reactance - Subtransient reactance (Xd’’)
a. Is a value used to determine the SCC during the first few cycles after a SCC occurs.
b. This is the SCC value to be used in all Short Circuit Studies. - Transient reactance(Xd’)
a. Is a value used to determine the SCC from the first few cycles up to about 30 cycles after the SCC occurs.
b. This value is often used in voltage regulation studies. - Synchronous reactance(Xd)
a. Is a valued used to determine the SCC when the steady state condition has been reached and may take several seconds.
b. This value is often used to determine the setting of generator backup Overcurrent relays. - Totally Symmetrical SCC:
If short-circuit occurs in an inductive reactive circuit at the peak of the voltage wave-form, the resulting SCC will be totally symmetrical. - Totally Asymmetrical SCC:
If short-circuit occurs in an inductive reactive circuit occurs at the zero of the voltage waveform, the resulting SCC will be totally asymmetrical. - Partially Asymmetrical SCC:
If short-circuit occurs in an inductive reactive circuit occurs at some time between the zero and peak of the voltage waveform, the resulting SCC will be partially asymmetrical. - The rate of decay of the DC component:
- The X/R ratio (ratio of inductive reactance to resistance looking upstream from the fault point) will determine the rate of decay of the DC component.
- As X/R increases, the rate of decay decreases. - Momentary rating is the Short Circuit Duty during the first cycle after a fault and defines the equipment’s ability to close and latch against worst-case mechanical stresses.
- Interrupting rating is the Short Circuit duty as the equipment contacts part and is expressed in symmetrical amperes or MVA.
- Draw the curve for Assymetrical / Symmetrical / SCC.
- Alstom Power http://www.alstom.com/home/index.EN.php?languageId=EN&dir=/home/
- A. Eberle GmbH for measuring, controlling and recording tasks for transformers and arc suppression coils.
- Areva – Energy
- Areva – T&D (Transmission and Distribution)
- Asea Brown Boveri (ABB)
- BASLER
- Bechtel
- Chiyoda Corporation
- GE
- Hyundai
- Mott MacDonald
- PJM Interconnection -- regional transmission organization that coordinates the movement of wholesale electricity in some parts of 13 American states.
- Samsung
- SEL
- Siemens – Energy and Automation
- Siemens – PTD (Power Transmission and Distribution)
- Schneider
- Toshiba
- VATECH
- Utility Integration Solutions, Inc. (UISOL) -Smart Grid Solutions
- List of United States electric companies
http://en.wikipedia.org/wiki/List_of_United_States_electric_companies - List of renewable energy companies by stock exchange
http://en.wikipedia.org/wiki/List_of_renewable_energy_companies_by_stock_exchange - Energy and Utilities Industry Companies
http://www.plunkettresearch.com/Industries/EnergyUtilities/EnergyUtilitiesIndustryIndex/tabid/189/Default.aspx - Electrical and Electronic Engineering Consultants
http://www.kompass.com/guide/technical-services-training/electrical-electronic-engineering-consultants/GSENWW600610_C84700.html
Question Bank :
- Electrical power system consist of 4 major categories:
a. Generation System
b. Transmission System
c. Distribution System
d. Utility System - Majority of electricity (65-70%) is produced by steam turbine plants and fuel is Coal or Nuclear.
- Hydro electric generation (25-30%) forms the 2nd largest means of generating electricity.
- Renewable sources of energy fall in a very small range (2-5%).
- Renewable sources of energy – solar, wind, ocean, bio gas, geothermal, etc.
- Gas Turbines are used during short periods of high demand for Peaking.
- Large generators voltage rating or generation is @ 13.8kV to 24kV voltage levels.
- Generator voltage is stepped up to transmission voltage level using transformers.
(Because …
a. Generation and Distribution stations are far away.
b. There will be huge I2R losses (transmission losses or copper losses) if the voltage level is low.
c. Transformers can transform this energy to higher voltage levels, without much loss.) - Transmission voltage levels in the range from 115kV to 765kV.
- Standard transmission voltages are 115kV, 138kV, 230kV, 345kV, 500kV and 765kV.
- At distribution station, the transformer steps down the voltages.
- Low voltage ranges from 34.5kV to 138kV at distribution station.
- Distribution standard voltages are 4.16kV, 12.47kV, 13.2kV, 13.8kV and 34.5kV i.e. range is from 5kV to 34.5kV.
Why we cannot use higher voltages directly?
a. Difficult to have equipments with such a high insulation rating.
b. Not economical. - Distribution transformers are used to further step down to utilization voltage levels, usually at 600V.
- Standard utilization voltages are 480Y/277V, 460V, 208Y/120V, 240V, and 120V.
- Higher utilization voltages – 6.9kV and 4.16kV are standard voltages for supplying large industrial motor loads.
