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Flashcards in NERC Prep Deck (233):

Area control error

An instantaneous difference between a balancing authorities net actual and scheduled interchange , taking into account the effects of frequency bias and correction for meter error.


Contingency reserves

The provision of capacity deployed to meet the disturbance control standard and other nerc and regional reliability organization contingency requirements.


Disturbance control standard

The reliabity standard that sets the time limit following a disturbance within which a balancing authority must return its area control error to within a specified range


Operating reserve

That capability above firm system demand required to provide for regulation, load forecasting error, equipment forced and scheduled outages and local area protection. It consists of spinning and non spinning reserves


Reportable disturbance

Any event that causes an ace change greater than or equal to 80% of a balancing authorities or reserve sharing groups most severe contingency


Reserve sharing group

A group whose members consist of two or more balancing authorizes that collectively maintain allocate and supply operating reserves required for each balancing authority's use in recovering from contingencies with the group



Nerc required time error to be fixed within 15 mins following a disturbance


Contingency reserves

Non spinning or supplemental and spinning reserves


Operating reserve

Non spinning , spinning reserves, and regulating reserves


Operating reserves contributors

Controllable load reserves, adjustments to interchange schedule, generation


Contingency reserve

Covers most servers single contingency , more that 80% - reportable. More than 100% of most severe contingency reportable event but no penalties apply for failure to meet DCS


Reportable contingency time

Within 15 mins recover from reportable disturbance, within 90 mins shall fully restore . 90 mins begins at end of 15 min period


Balancing authorities shall review contingencies how often to determine single worst contingency?



Contingencies occurring with in how long considered 1 event?

60 seconds


A sudden change in balancing authority's demand supply balance following loss of generation results in sudden change in



What group can approve a change in the disturbance recovery period for an interconnection?

Nerc operating committee


Contingency reserve restoration period begins at?

The end of disturbance recovery period


Frequency bias setting

A value in mw/.1hz set into balancing authorities agc equipment to represent a balancing authorities response to a frequency deviation


Pseudo tie

A telemetered reading or value that is updated in real time and used as a tie line flow in the agc ace equation but for which no physical tie or energy metering actually exists


1% change in frequency =

2% load change in same direction - primarily of induction motors not heaters ( resistive ) this is used to determine BETA for ace equation


Generator response to governor droop

200mw/3hz x (60hz-59.95hz)=3.33mw


Frequency response charachteristic

Decrease load/decrease frequency+ generator output


Frequency bias = frequency response



Actual interchange + frequency bias =0 ACE



Bias setting

Reported to nerc yearly, must be at least 1% of the balancing authorities estimated yearly peak demand per .1hz change as described in the frequency response charachteristic survey training document for a native load serving balancing authority


Tie line frequency bias controls

Fixed frequency bias - based on a fixed straight line function of tie line deviation versus frequency deviation. Variable bias- based on a variable function of tie line deviation to frequency deviation


Balancing authorities- overlap regulation

ba that are performing overlap regulation service will increase its frequency bias setting to match the frequency response of the entire area being controlled


Balancing authorities- supplemental regulation

bA performing supplemental reg service shall not hangs its frequency bias setting


Jointly owned units

Frequnecy bias setting is included in the area in which the unit is located only


Frequency bias setting

Must be close to areas frequency response. If it is not and is set to low and an external loss of generation occurs, ace will become positive and agc will lower generation , screwing things up even more


Tie line frequency bias

Each BA shall operate its AGC on tie line frequency bias


Minimum frequency bias setting for generation only balancing authority

1% of its estimated maximum generation level in the coming year per .1 hz change


Determining fixed frequency bias

By averaging the frequency response for several disturbances during on peak hours


Dynamic schedules

When jointly owned units - each BA shall account for the unit by including their respective share of units governor response charachteristics when calculating frequency bias . Used for the value for interchange accounting purposes


Time error correction

Adjust frequency by .02 hz so if it was fast it would be 59.980 or slow is 60.020 or adjust schedule frequency bias setting to + or - 20% of bias setting and take that off of NIs so for example if area had bias setting of 100mw it would add or subtract 20 me to NIs from ace equation



Automatically adjusts a balancing authorities generation from a central location to maintain its interchange schedule plus frequency bias.. Limits change in ACE to maintain a good cOS



Measures a balancing authorities impact on interconnection frequency



Measures the ability of a balancing authority to manage unscheduleed flows


Regulating reserve

The part of the operating reserve used to keep ace within a reasonable value to comply with CPS standards


Flat frequency control

Only used when area is islanded includes only 10b(Fa-Fs) part of ACE equation


Ace calculated every

6 seconds


Supplemental regulation service

Is a method of providing regulation service in which the balancing authority providing regulation service recieved a signal representing all or a portion of the other balancing authorities ACE


Overlap regulation service

A method of providing regulation service in which the balancing authority providing the regulation service incorporates all of the other balancing authorities tie lines, frequency response, and schedules into its own AGC/ ACE


Factors contributing to inadvertent interchange

Frequency support , load changes with in balancing authority, generator lag, metering errors, unilateral inadvertent interchange payback, human error



Algebraic sum of all the tie lines with adjoining balancing authorities



Scheduled flow of MW with all of the adjoining balancing authorities



Contribution to interconnection frequency control based on its frequency response charachtertics


Secondary/ good inadvertent interchange

Frequency support , regulation, governor support


Unilateral payback

Inadvertent interchange accumulations paid back unilaterally to a target of non zero ace, limited to balancing authorities L10 , cannot burden interconnection


Inadvertent interchange summaries

Must include at least the previous accumulation , net accumulation for the month, and final net accumulation for both the on peak and off peak periods


Frame relay

Data transmission technique used to send digitial info quickly to many destinations from one point of origin


Information assets

Proccessed or unproccessed data using nerc net


Nerc net

WAN used for exchanging power system info over frame relayit supports intergal security network, interchange distribution calculator, and reliability coordinator information system


Alternate pathways for communication

Looping a microwave system.. Redundant paths using different equipent such as protective relaying for transmission line carriers use microwave for one set or relays and power carrier for 2nd set of relays


Balancing authority

Integrates recourse plans ahead of time. Maintains load interchange generation with in a balancing authority area and supports frequency in real time


Reliability coordinator

The highest level of authority responsible for the reliable operation of the BES


Emergency load reduction plans

Must mitigate iROL violation within 30 mins


Balancing authority experiencing emergency

Shall only used assistance of interconnections frequency bias for the time needed to implement corrective actions


Balancing authority not experiencing trouble

Shall not unilaterally adjust generation to correct frequency problem while outside balancing authority is correcting its problem- it will strain the system plus add unshschuedulrd interchange


5% reduction in voltage

Equals overall 3% reduction in inductive and resistive loads


2nd steps for balancing authority

Manually shed firm load then request reliability coordinator to declare energy emergency


Enery emergency type

1- all available recourses are in use , foresees problems, all sources curtailed2- load management procedures are in effect , designated energy difficient, public appeals, dropping load, 3- firm load is being shed , must complete report and send within 2 business days to reliability coordinator


DOE loss of load reporting

Customer load lost,efforts to reduce load, deliberate acts of sabotag, vandalism, cyber attacks initial report due within 60 mins, final done within 48hours with all Events and remedies


NERC loss of load report

Same as DoE report but includes , unusual event that occurred to bulk system

Subject to regional reliability organization apprival,Preliminary due within 24 hours, final within 60 days


Role of regional reliability organization following a report/ disturbance

Shall make a representative available for preparation and investigation of final report, track and review status of final report recommendations, this should happen twice per year to make sure reccomendations are being acted upon, if any recommendation has not been acted on within 2 years, RRI shall notify Nercplanning committee. -SOS-notes/#sthash.11jXj9fk.dpuf


Transmission operators responsible for

Reliability of local transmission system, operates or directs operations of the transmission facilities, provides maintainence schedules, maintains voltage profiles , defines operating limits, develops contingency plans, coordinates load shedding


87 relay

Differential relay


21 relay

Distance relay


67 relay

Directional over current relay


Transfer trip signal

Form of pilot relaying, can be sent over fiber optics, microwave etc


Distance relays

3 zones of protection


System operating limits based on

Facility ratings, transient stability ratings, voltage stability ratings , system voltage limits


Voltage collapse

Lack of reactive power, voltage down by 10-20%, not enough mvars to serve power system and loads


Getting ahead of voltage

Putting capacitor banks in service before planned outage


Other actions to get ahead of voltage

Take shunt reactors out of service, raise generator voltage,raise tap positions on transformers, return lines and generators to service, curtail interchange transactions, curtail or shed load


Prevent voltage collapse by

Carrying dynamic reactive reserves close to the load, if mvars are not available shed load, ideally heavy inductive loads



Trans system does not have reserve transmission capacity mw or mvar reserves to handle the loss of a major electrical component such as line or generator


Uncontrolled separation

Instability when the power angle between two sections grows to large and the magnetic bond between the two sections is not sufficient to keep generators from losing sychronism



Operating the system to satisfy the most severe single contingency is also referred to as operating to satisfy the most severe N-1


TOs operate to protect against

Instability, uncontrolled separation, cascading outages from multiple outages



Must return system to within normal operating limits within 30 mins, transmission operator must take immediate action such as curtailing loads, energy service etc


Operational reliability info that balancing authorities provide reliability coordinators with

To be updated every 10 mins.. Example tie lines flows, operating reserves, mw reserve available within 10 minutes


Power angle

Difference in voltage angles between two locations in the power system


More capacitive circuit

Current will lead voltage which will tend to raise voltage


As power angle increases power transfer increases



Torque angle

Difference in voltage angles between generator internal or excitation voltage and the system voltage


Real power flows from

Higher voltage angle to lower voltage angle


Real power transfer

The higher the voltage the lower the power angle required for a given power transfer


When iROL or sol exceeded for more than 30 mins

Notify nerc and rro


Transformers rated in?



Shunt capacitor banks

Supply reactive power to the inductive load, reduce current between generator and load, reduce mvar losses


Shunt reactors

Absorb excessive reactive power locally



Element that stores energy in the form of electrical charge and introduces capacitance into a circuit . The stored energy creates an electrical field


Capacitive reactance

Measure of how a capacitor affects the flow of ac current . It describes the reaction of a circuit to the fluctuating electric fields of ac voltage. A capacitor that is places into an ac circuit builds up a charge that opposes change in voltage



The property of an electrical circuit that produxes an electromotive force by induction when the current is changing. Inductance opposes current changes


Reactive power

The product of voltage and out of phase current , measured in volt ampheres reactive or var.



Consists of 2 different types of power, megawatts and mvar, mw does the actual work or real power... Mvar produces the magnetic field that enables the power to do the work


Angular separation or phase angle

Angular seperatipn between current and voltage capacitive circuit. Current leads voltage . Inductive circuit is opposite


How to raise voltage on a system

Capacitive reactance must me increased or inductive reactance lowered


Placing capacitor near inductive load

Reduces current flow and line losses


Dynamic sources of reactive power

Transmission lines and generators w auto voltage regulators


Knee of pv curve

Once this point is reached . Any increase in mw will cause voltage collapse , to avoid this , redid patch generation or place capacitors inservce closer to the load


Ace DCS violation restore time

15 minutes


If a transmission operator is in unknown state

He has 30 minutes to restore


AGC control types

Pulse control or set point contro


Agc pulse contro

Units recieve raise or lower controls every few seconds this pulse acts on a speed changer motor to change its load reference settings in small increments


Set point control for agc

Set desired mega watts fed directly to turbine controls- once through fossil units use this



Must be redundant such as looping a microwave system or using redundant paths with different equipment


Facilities management

All operators who may need to use backup system should practice with it monthly ,



Coordinated communications include nerc hotline, weccnet, and reliability coordinator information system .. Must have procedures for backup communications


Nerc net

A WAN that supports interregional security network, interchange distribution calculator and the reliability coordinator information system


Communications and coordination

Each TO and BA shall notify its RC and all other potentially affected TO and BA through pre determined communication paths of any condition that could impact reliability or which could require firm load shedding


Voltage reduction customer demand

A 5% reduction in voltage will drop load by 3%


Emergency operating agreements between adjacent BAs

1. Provisions for emergency assistance 2. Provisions to obtain emergency assistance from remote BAs


If a BA loses its largest generating source

A neighboring BA can change the NIs part of its ace equation to make up for the generation


Reserve sharing group

Agreements for emergency assistance minimize the amount of time a bA has to rely on the interconnection for bias support - should only be used to evaluate options and resolve emergencyreturning ACE to normal values as soon as possible is primary objective


Transmission operators emergency load reduction plan

Shall have load reduction plan for all IROL that includes facilities in its area. Shall include details of amount of load shedding to be done to mitigate iROL violation before system separation or collapse occurs. Must be done within 30 minutes .


Each TO and BA shall develop 4 plans

1.'mitigateoperating emergencies for insufficient generating capacity. 2) mitigate operating emergencies on the transmission system 3) implementation of load shedding when nessasary 4) system restoration


TO and BA emergency plans to mitigate operating emergencies

1)communications protocols to be used during emergencies , including assignments to communicate within and external to the organization 2)a list of controlling actions such as starting offline generators etc 3) tasks to be coordinated with other entities such as providing reActive power, voltage control at interconnection 4) staffing levels for emergency. It is important to note that one of the controlling actions shall be load reduction in sufficient quantities to resolve emergency within established nerc guidelines


TO and BA emergency plan review

To be done once a year


BA anticipating operating emergency

Bring on all avail generation, postpone equipment maintainence , schedule interchange purchases in advance, be prepared to she'd firm load


BA not experiencing emergency

Shall not unilaterally adjust frequency during emergency. Will cause overloading of transmission lines and will develop excessive inadvertent interchange accumulation


If a BA needs to declare energy emergency

This is done through its RC


BA not complying with DCS or CPS

Shall remedy by , loading all available generation , deploying all available operating reserve, interrupting interrupt able loads and exports, requesting emergency assistance through other BAs , declaring an energy emergency though its RC , reducing load through such procedures as voltage reduction, publicappealsand curtailment of interrupt able and firm loads


Energy emergency alert levels

Eea1) when a BA or lse foresees a problem sustaining its load eea2) when a BA is no longer able to provide its customers energy requirements , eea3 when firm load shedding is imminent or in progress


Load shedding plans

Shall be coordinated with interconnected BAs and TOs to shed load for under frequency and under voltage . Load shed should be done before generation is shed. Under voltage load shedding occurs in pre selected blocks


A BA or TO or LSE experiencing a disturbance

Shall submit a preliminary written report within 24 hours to RRO and NERC and DOE of the disturbance .. If weather does not permit the writing of the report then they should verbally notify the rro and nerc


DOE reporting

Initial reporting done within60 mins ,final report done within 48 hours


DOE disturbances

Uncontrolled loss of 300mw for more than 15 mins from single incident, load shedding of 100mw during emergency plan, voltage reductions of 3% or more,public appeals to reduce use of electricity, actual or suspected attacks , fuel supply emergencies, loss of electric service to 50k customers for more than am hour, complete operational shutdown of transmission or electrical system


Nerc disturbance reporting

Loss of component that affects integrity of the interconnection, interconnection islanding, loss of generation (200mw or more in eastern and 1k I'm ercot), equipment failures that result In firm load loss for 15 mins or more, firm load shedding of 100mw or more to maintain continuity of BES,a violation of IROL , any disturbance that the operating committee wants to submit to the dawg


Final report due to nerc

Within 60 days


RRO responsibilities during emergency

Make representatives of the nerc operating committee and the dawg available to assist in final report. Track and review status pf reccomendations of report. This should occur at least twice that year


TO restoration plan requirements

Personel identified, reliable black start units, contingency plans, synchronizing areas, load restoration including critical loads , procedures for simulating and where practical testing every 3 years, training records showing restoration excersizes, functions to be coordinated with and among RC and neighbors , notifications to operating entities as steps are completed


TOP system restoration plans must be

Updated as nessasary to reflect changes and correct deficiencies , reviewed annually, developed w intent to restore interconnection , coordinated w neighboring systems , periodically testing of telecommunications equipent


TOP emergency plans as it relates to generation

Emergency power should be available to shutdown safely, operate turning gears, minimize damage to units, maintain communications , expedite restart


TO and BA must coordinate restoration actions with



How to proceed after islanding or collapse

Determine extent and condition of area, contact other BAs and TOs to determine circumstances in their areas, start taking nessasary actions to restore system frequency by matching generation to load, begin reviewing interchange schedules , reschyronoze the isolated area to surrounding areas only after RC gives their approval, use strongest transmission lines and restore offsite power to nuclear station ASAP


Open circuit breakers

On distribution side of blacked out area to control power levels, also disable automatic reclosing relays.


Reschyronize with interconnection

Only done at power plant w scope, the phase angle should be less than 10 degrees, frequency should be the same and voltage magnitude close too. If differences are to large, operator can re dispatch generation to reduce differences


Self certification

Every year each TO shall self certify to the RRO compliance standard . Shall include : operating instructions for restoring loads , set of procedures for annual review and of possible simulation , documentation of personnel training records to verify training , reporting of any significant changes to restoration plan to the RRO


RC has highest level of authority

It is responsible for the coordination of system restoration


During restoration RC shall

Establish communications with other RCs the RRO and Nerc via the nerc hotline and the RC'S


Each RC is required to sign nerc standards of conduct

Nerc standards of conduct address ...independence , emergency actions, reporting deviations, rules governing employee conduct, books and records,rules governing maintainence of written procedures


During restoration

Nominal voltages shall be maintained between 90-110%


Shunt capacitor banks during restoration

Should be taken out of service while restoring the system


Static var compensators and synchronous condensers during restoration

Should be placed in service as soon as practical


Synchronizing of islands

Shall be approved, coordinated, communicated by the RC as to not burden surrounding areas.


Back up control centers

Reliability entities are not required to have back up control centers but procedures must be in place if primary control center goes down. Must not burden interconnection


Loss of control center contingency plans

Must address .. Ability for instantaneous tie line mw and mvar telemetry.. Ability for instantaneous generating unit telemetry.. Ability to read mw hour accumulators for all tie lines and generating units.. Ability to collect system frequency and time error measurements.. Data links to send generation control signals to generator control centers.. Lost of critical facilities of applicable entities


Loss of control center cont.

Must contain procedures for maintaining basic voice communications .. Conduction of annual testing of plan.. Annual training. Review of plan annually.. And updating plan annually


Indications of lightening fault

Ground relay operation ( relay 64) or directional current relay (67)


Phase to phase fault

Protected by distance relay (21)


2 different types of zones for relaying

Open and closed .. Differential protection is example of closed zone.. Distance relay example of open zone


Differential relaying

Closed protective zone.. Measures current entering and leaving zone


Distance relaying

Open zone... Looks at impudence of line for a specific distance..have quality known as Reach. This tells how far down the line it will detect a fault. If it is set to high it will detect faults to far down line which will cause excess tripping


Over current relaying

Used as a backup to distance relaying and differential relaying . Can be directional or non directional ( will only trip of current is flowing 1 way) -


Pilot relaying

Protective relaying where relays communicate with each other to allow for faster and more accurate clearing of faults within line segment


Transfer trip relaying

Form of pilot relaying.. Initiated at one location and sent via communications channel to trip another breaker or trip auxiliary relay which will trip multiple circuits


Misoperation procedures

Each GO TO or anyone that owns a transmission protection system shall provide its RROwith it's misoperation analysis and corrective action according to RRo procedures


Operating emergencies

Line overloading .. Loss of transmission line..loss of generation..shortage of reactive power


Actions TO takes during energy emergency

Curtailing transmission service.. Curtailing energy schedules. Operating equipment such as reactive sources.. Shedding firm load


A system with a generating deficiency

Must reduce its load to restore ace to an acceptable value if they cannot balance generation and load in a timely manner


Being prepared for a large system disturbance or pending voltage collapse

Areas must have a program in place to arrest these conditions..should address levels of voltage and frequency at which manual action should be taken.. Also to prevent abnormalities such as over voltage or generation instability caused by automatic load shedding


All BAs are required by nerc

To maintain operating reserves


Exceptions for burdening neighboring systems

Generator outages- must coordinate with TP...transmission facilities- must coordinate with RC


Elevating transmission service priority of an interchange transaction

You can change the priorities of interchange transactions and interrupt power if it will help the energy deficient area the LSE must have RC declare an EEA which must be posted on NERC website and include the expected level of the transmission service priority declaration


Daily load forecast is determined by tools such as

Load forecast..unit commitment.. Power flow simulation programs


SOLs are based on

Facility ratings ..transient stability ratings.. Voltage stability ratings.. System voltage limits


Economic dispatch

Point where all generation is operating at the same incremental cost while serving the demand


Transfer capability studies

Should be done between operating entities annually or whenever a change in facilities warrants a new study. All entities should use uniform line identifiers to not get confused


Transfer capability issues include

Voltage limits.. Reactive limits.. Thermal limits .. Stability limits


GO must provide info on outages for the following day

To TO for any generator greater than 50mw.. TO must provide info daily to RC if generator over 50mw or line over 100kv.. Outage info posted by 1200 cst


N-1 contingency

single worst contingency on the system


Voltage control equipment outages

Shall be coordinated between entities for AVRs..shunt capacitors etc


Voltage collapse

When there is lack of reactive power .. Voltage levels down 10-20%


Getting ahead of voltage

When you Know you are going to have a voltage decline. Place capacitors in service, take reactors out.. Raise gen voltage.. Raise transformer tap positions .. Curtail transactions.. Curtail or shed load.


When reactive recourses are limited

Limit mw transfers - this prevents power angle increases.. Keep voltage high- this reduces current and angle.. Redid patch generation .. Shift generation patterns to unload heavy loaded lines .. Request neighbor reactive support . Shed load


RC is responsible for

Scheduling of potential reliability conflicts


Uncontrolled separation can occur as the result of

When power angle gets too large between two sections and the magnetic bond breaks and they loose synchronisim


TOs must operate in anticipation of worst contingency

This night be loss of largest unit or large interchange purchase


Following a contingency or other event which results in SOL violation

TO must return limits within 30 mins.they must make every effort to stay connected to interconnection but of they deem they are in danger of sol or iROL they can disconnect


If TO enters unknown operating status

Must restore system to proven reliable operating status within 30 mins


TOs must coordinate with other TOs

Maintain develop and implement procedures to provide for transmission reliability


Transmission line capacity is determined by

Thermal limits


Transmission line inductive reactance

Dependent upon spacing between strands within each conductor and distance between each conductor


Transmission line capacitive reactance

Dependent upon size and spacing of conductors


All transmission equipment rated by

Transmission owner..these ratings are used to establish SOLs for system


TOs and BAs provide monitoring data to RC

This helps RC to perform reliability assessments .. Coordinate reliable operations within RCa and with other RCs


Electric system reliability data is updated

Every 10 mins.. Includes tie line flows generator mw output.. Etc


Torque angle

Angular difference between the rotor magnetic field and the magnetic field of the stator of the generator


Power angle

The voltage angle difference between 2 locations in the power system


Phase angle

The angular separation or difference in phase between the current and the voltage waves


RCs publish BA data and system operating assesnements

On the nerc isn or rcis.. BAs provide electric systems reliability data to the RCs via the rcis



Shall have access to all info nessasary to balance generation and load including .. Status of generators and transmission recourses.. Protective relay status.. Weather forecast and past loads.. System frequency


Sufficient metering and monitoring equipment

Shall be provided to all RC TO and RC


3 types of stability

Steady state- no significant changes ... Transient- a sudden large change..... Oscillating - constantly changing voltage frequency and angles


Avoid excessive transmission line loading

This results in large power angles.


The more transmission lines that are in service

The more power can be transferred at a given torque angle


Verify generator voltage regulators are in service

If they are in automatic the higher the voltage the lower the power angle that is required for given power transfer


Records must be kept to show

Evidence that TOinformed RC when iROL or sol was exceeded.. There were actions to return system to within limits .. The TO returned system to within an IROL -


Each iROL or sol exceeding 30 min

Shall be reported to the RRO and nerc within 72 hours.. Using nerc iROL report


Transformers are rated in

MVA..usually have several ratings associated with the stages of cooling


Shunt reactor banks

Absorb excess reactive power , usually lightly loaded lines


Priority to alleviate violations

Redispatch generation.. Curtain interchange transactions.. Disconnect overloaded equipment.. Shed load


Circuit breakers

Usually not limiting component in power transfers due to high continuous rating.. If a CB fault clearing time is too great it can limit power transfers by need for creating stability limit


Disconnect switches

Not used to interrupt fault current


Air break switches

Limited ability to interrupt load . Limited to small current ineruption such as transformer charging current


Shunt capacitor banks

When energized. Produce reactive power.


Interchange transactions and schedules may contribute to sol and iROL

Because of parallel flows


Increased current cause

Increased loading and larger power angles


When TO takes action to alleviate sol or iROL

Must notify RC and effected TOs.. If possible notify before you take action


Priority to alleviate violations

Redispatch .. Curtail interchange .. Disconnect overloaded equip.. Shed load


Benefits of being connected to interconnection

System inertia from stored energy in rotating generators.. Ability of affected system to resist changes in frequency .. Access to reserves, not only mw but also dynamic reactive reserves.. Instant assistance from tie line bias


Synchronizing relays

Need 20 percent power angle or less to tie busses together



Low frequency .. Low voltage.. High currents


Apparent power MVA

Consists of both active and reactive power


Increased loading causes

Circuits to be more inductive


Voltage control is

Control or reactive power flow


When generator AVR is in service

It is considered a dynamic source of reactive power


Nerc standard for maintaining reactive reserves

Each TO shall have adequate reactive resources within its area to protect voltage levels under normal and contingency conditions


A strong bus

One that has 1 or more generators attached at the closed end of a line that has the ability to absord mvar


Responsibility of development of emergency load reduction plan to respond to iROL

Transmission operator.. Plan must be able to be implemented within 30 mins


An emegency Alert is a

Emergency procedure


Nerc has how many emergency alert levels



Rro final reports are due within

60 days


A reportable incident shall be reported to

Nerc and rro


Doe reports are aimed at

Customer load loss, sabotage, and efforts to reduce load


Rescynchronising of major system islands should only be attempted after approval by the

Reliability coordinator


Audit of loss of primary control center plan is conducted

Every 3 years


Loss of primary control center plan must be implemented within

1 hour


Distribution providers and load serving entities take reliability directives from

Transmission operator


Balancing authority is required to maintain

Operating reserves


Angle instability

Is the inability for system to maintain magnetic bonds