PRC-019-AB-2 Coordination of Generating Unit or Plant Capabilities, Voltage

Regulating Controls and Protection

Technical Workshop May 29th,2018 Presented by: Pravin Koshti

Agenda for PRC-019 Technical Workshop

• Housekeeping

• Introductions

• Presentation on PRC-019 by Pravin Koshti – Review of standard

– Provide technical clarification on the requirements and measures, including some examples

– Discussion on questions submitted by stakeholders

• Q & A session

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Housekeeping

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• Women

M W

You are Here

Reception

Access Card or Code

EMERGENCY EXIT Then follow facilitators

instructions

• Emergencies - Use cell: 911 or room phone: 9-911

• BP Centre: 6th Floor, 2nd St. SW and 4th Ave. SW

• Muster Point – Livingston Place

Purpose of PRC-019 Technical Workshop

• Review draft PRC-019 standard

• Provide technical clarification on the requirements and measures

• Discussion on questions submitted by the stakeholders

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Why PRC-019-AB-2 is introduced ?

“To ensure that Generators will not trip off-line as a result of improper coordination between generator protective relays and generator voltage regulator controls & limit functions”

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PRC-019-AB-2 : Purpose

• The purpose of this reliability standard is to verify coordination of generating unit facility or synchronous condenser voltage regulating controls, limit functions, equipment capabilities and protection system settings.

• This draft standard requires Generator and Synch Condenser (SC) owners to demonstrate that Generator / SC voltage regulator controls and limit functions are coordinated with the Generator/SC capabilities and protective relays.

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PRC-019-AB-2 : Applicability

• Transmission connected , – Synchronous condenser gross nameplate rating > 20 MVA

– Generating unit with maximum authorized real power rating > 18 MW

– Generating unit with maximum authorized real power rating > 18 MW and part of an industrial complex

– Power plant that has a combined maximum authorized real power rating > 67.5 MW (Cluster of generating units)

– AGF that has a maximum authorized real power rating > 67.5 MW, where voltage regulating control for the facility is performed solely at the individual generating units

• Generating unit is a black start resource

• Generating unit / Aggregated generating facility / Synchronous Condenser which is material to reliability standard / Interconnected electric system as determined by the AESO

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PRC-019-AB-2 : Requirements

• R1 : Each GFO/TFO must, by the effective date of this reliability standard and at a maximum of every five (5) calendar years, coordinate the voltage regulating system controls, including in-service limiters and protection functions, with the applicable equipment capabilities and settings of the applicable protection system devices and functions, assuming normal automatic voltage regulator control loop and steady-state system operating conditions, by verifying the following coordination items for each applicable facility:

– (a) the in-service limiters are set to operate before the protection system of the applicable facility in order to avoid disconnecting the generating unit or synchronous condenser unnecessarily; and

– (b)the applicable in-service protection system devices are set to operate to isolate or de-energize equipment in order to limit the extent of damage when operating conditions exceed equipment capabilities or stability limits.

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Coordination

• Standard requires coordination among ;

1. Generator / Synchronous Condenser (SC) Capability

2. Protective Relays’ settings

3. Generator /SC Voltage Regulating System Controls & Limiters

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1.Synchronous machine’s Capability Curve

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2.Typical Generator Protections

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3.Excitation System Functional diagram

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- Major function is to control and supply DC current to Generator field windings

- Automatic Voltage regulator (AVR) adjusts the excitation to maintain AC terminal voltage

- Responds to system disturbances by rapidly boosting or reducing the current applied to the rotor with a speed and forcing capability consistent with generator capabilities and system requirements.

Excitation Limiters

• Voltage regulating system controls are the control functions of the Automatic Voltage Regulator (AVR) mainly;

– Over Excitation Limiter (OEL): Prevents over heating of the

field winding, OEL reduces field current during an over excitation events.

– Under Excitation Limiter (UEL) : Ensures Generator maintains minimum field current, remains in a stable operating zone and does not enter in the Loss of excitation zone .

– Voltage per Frequency Limiter (V/Hz) : Reduces the terminal voltage when the frequency is decreasing, prevents Generator and Generator step up transformer from Over fluxing.

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Synchronous Machine details

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Over Excitation Capability Coordination

• Field Winding Thermal Capability

– Generator field windings are designed to carry rated current for a continuous period so that it can support Generator to produce rated MVA at rated power factor and voltage.

– Per ANSI C50.13 , The generator field winding shall be capable of operating at a field current of 125 percent of rated-load field current for at least 1 minute starting from stabilized temperatures at rated conditions.

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Field Winding Thermal Capability and OEL

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Time (seconds) 10 30 60 120

Field Current (%) 209 146 125 112

Generator Field current curve per ANSI C50.13

Field Winding Thermal Capability Coordination – Example

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Over Excitation Capability Coordination –Example

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Over Excitation Capability Coordination –Example

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Synchronous machine limits in Under excited Zone

• Core end overheating limit : Core end overheating can occur in the under excited region with increase in the armature end leakage flux. This flux enters and leaves in a direction perpendicular to the stator laminations causing eddy currents in the laminations, and hence heating. OEM of the Synchronous machine will provide this limit.

• Steady State Stability Limit: This is the limit which Synchronous machine OEM will calculates and provides to the owner, operation beyond this limit will result in a loss of synchronism and will result in loss of unit.

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Limiter and Protection for Under excited Zone

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• Under Excitation Limiter (UEL/MEL) : Under Excitation limiter will boost the excitation through increase in field current in the event when the excitation level is determined to be too low. UEL will ensures that minimum excitation is maintained through out the operation of Synchronous machine.

• Loss of Excitation (LOE) Protection : LOE protection has been provided by a mho-type distance relay with the circle centered on the negative reactance axis. The unit will trip if the generator's apparent impedance remains within the characteristic for a selected period of time.

Under Excitation Zone Coordination – Example

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Under Excitation Zone Coordination – Example

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Loss of Excitation Protection & D curve

Under Excitation Zone Coordination – Example

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Loss of Excitation Protection & D curve

Mho impedance relays with reverse offset

Under Excitation Zone Coordination – Example

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Under Excitation Zone Coordination – Example

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Under Excitation Zone Coordination – Example

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V/Hz Limiter & Protection Coordination

• OEMs of the Synchronous machines and Transformers will provide over fluxing limit to prevent damage to Generators / SCs and connected Transformers that may occur when the excitation (V/Hz) exceeds the equipment capability.

• Per ANSI C50.13 & 67 , Generator shall operate continuously at rated MVA, frequency and power factor for voltages not more than 5% above or below rated voltage.

• A typical recommended voltage-frequency boundary for operation of large cylindrical rotor generators at rated output is area between 95% and 105% voltage, and 98% and 102% frequency.

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ANSI C50.13 -Typical V/Hz Limits

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V/Hz Limiter & Protection Coordination

• Typical example of V/Hz Protection and Limiter Coordination – If V/Hz > 1.05 pu give an alarm, manual action to reduce

Voltage

– V/Hz limiter action setting between 1.05 -1.10 pu ( in AVR)

– V/Hz setting in the relay initiating at 1.10 pu with definite time or inverse time characteristics, say 1.10 pu with Td= 60 sec

– For Higher V/Hz ,say 1.18pu with Td= 6 sec

• The V/Hz capability of Step up Transformer connected to the terminals of the generator must also be considered during the review of coordination.

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Example: Capability, Controls & Protection

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• Exciter V/Hz Limiter

• Exciter V/Hz Trip (In case Limiter fails)

• Relay 24 definite time trips (1) 110% for 60 Sec (2) 118% for 6 Sec

• Generator rating is lower than Generator Step up Transformer

Example : Overall Coordination

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Coordination Summary Table - example

PRC-019-AB-2 : Requirements

• R2 Each legal owner of a transmission facility, legal owner of a generating unit and legal owner of an aggregated generating facility must perform the coordination described in requirement R1 :

– (a) by the later of either the effective date of this reliability standard or within 90 days following the identification of unplanned systems, equipment or setting changes that will affect the coordination described in requirement R1; or

– (b) prior to electrically connecting to the transmission system: a generating unit or a synchronous condenser or a generating unit that is part of AGF; any of which are impacted by planned systems, equipment or setting changes that will affect the coordination as described in requirement R1.

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Planned Changes

• R1 protection coordination required to be completed before first synchronization with the transmission system; in the case where the systems modification , equipment change or settings changes are carried out in a planned manner. Few examples:

– Voltage regulating settings or equipment changes

– Protection System settings or component changes

– Generating or synchronous condenser equipment capability changes

– Generator or synchronous condenser step-up transformer changes

– Modifications effecting excitation controls & limiters

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Evidences to support R1 completion

• Following documents with dates can be submitted to support completion of R1 of PRC-019 (for each Generator / SC );

1. Coordination Summary table (slide#32)

2. Generator capability curve highlighting MW limit / MARP,OEL,UEL and Overall protection coordination (slide#31)

3. Field Winding Thermal Capability coordination (slide#16)

4. Loss of excitation / field protective relay characteristics with P-Q Diagrams or R-X Diagrams (slide #22,23,24)

5. Volts-per-hertz protection relay settings including volts-per-hertz limiters in the automatic voltage regulator, Inverse Time Diagrams (slide#30)

6. Relay settings

7. Only upon request from the AESO : Supporting documents such as Engineering study , Relay protection settings calculation sheets (with specific references)

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Evidences to support R2 completion

• Following documents can be submitted to support completion of R2 of PRC-019;

– Operator’s log book / equivalent documents identifying first

synchronization of Generator / SC with the transmission system

– Evidences mentioned as the supporting documents for R1

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Timelines –Cheat sheet !

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• Once approved by the AUC ; • 8 full calendar quarters – grace period to become compliant

• Say hypothetically, PRC-019 approved on Dec31,2018, MPs have until Dec 31,2020 to complete R1

• Periodic Verification at every 5 Calendar Years • Say hypothetically, R1 performed/completed on Dec20,2020 –

next due is Dec31,2025

• 90 Calendar days to fix, if discrepancies found for protection & limiters • Say hypothetically, discrepancy found on Jan1,2021,MPs have

(Jan1 + 90 days) to complete R2

• If planned changes – before first unit synchronization

Q & A

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Stakeholder’s Questions

Questions - ARCDG

• Does WECC testing cover the requirements of this standard? [AESO] :

– PRC-019’s requirements are not fully covered by the WECC testing

– Majority of the WECC testing contractors are checking the functionality of V/Hz limiter, UEL and OEL by changing their limiter set point to lower value and applying a step change test.

– Some of the contractors are highlighting (unsure about verifying) Loss of excitation on the D curve while others are not.

– Unsure about coordination of Generator protection relays settings with the Exciter limiters- V/Hz limiter and Field current thermal limiter.

– Unsure about verification of loss of excitation relays coordination

– PRC-019’s verification can be combined with the WECC testing

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Questions - ARCDG

• How does the standard apply to wind generation resources? [AESO]:

– Per current ISO rule 502.1, In the Wind Farm facilities’ Voltage regulation is required to be carried at the collector bus level . Dynamic & steady state Reactive resources along with Wind Farm Generators are responsible (under Voltage Regulation System) for managing collector bus voltages. PRC-019 is NOT applicable to Wind Farms.

– proposed PRC-019 is applicable to those AGFs where voltage regulating control for the facility is performed solely at the individual generating units.

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Questions - ARCDG

• How does the standard apply to dispersed power producing resources?

• [AESO] : For dispersed Generators , if voltage regulation for the facility is carried out at the individual generator level , PRC-019 would be applicable.

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PRC-019 & Dispersed Generation

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Voltage regulation is done at the individual Generator level.

Questions - ARCDG

• Do we need to perform field testing to comply with the PRC-019 standard? Outage coordination & availability of testing contractors could be limiting factors.

[AESO] :

– PRC-019 standard requires engineering exercise / study. Relay calculations, relay settings ,AVR settings and OEM Engineering documents will be used to verify protection coordination.

– PRC-019 can be coordinated with the WECC testing activities.

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Questions - ARCDG

• Does back-up protection come into scope ? – [AESO] :Yes, Back up protection relays are also required to

coordinated with the Exciter Limiters and equipment capability. e.g. If GFO has Relay#1 from Beckwith and Relay#2 from SEL, both Relay#1 and Relay#2 protections are required to align with Exciter Limiters and equipment capability.

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Questions - ARCDG

• Does this standard apply to the primary protection for system transformers where there is not a GSU ?

[AESO] :

– No, this proposed standard is not applicable to other System Transformers ( i.e auto transformers like 500kV / 240kV or 240 kV / 138KV).

– The purpose of this standard is to coordinate Generator / SC capability with the excitation system limiters and protection relays.

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Questions - MPs

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• For Applicability section , For (a), and (f), what is the AESO’s plan to provide a list of, and notify those, generating facilities to which this standard will apply, or only those applicable under (f)?

[AESO] :

– Upon approval of PRC-019 by the AUC, market participants will be notified through AESO newsletter. No individual notification will be provided.

– In case of (f), the AESO will notify the legal owner in writing and will include their asset in the Appendix 1 of PRC-019.

Questions - MPs

• Applicability: MP would like additional clarification on paragraph (d): if there is voltage regulating control at the substation as well as at the generator level, does this mean that this standard does not apply (for example a tap changer on the generator step up transformer)?

– [AESO] : This standard is applicable to the Voltage Regulating System (VRS / AVR) of the Synchronous Generators and Synchronous Condensers. Voltage Regulation with On Load Tap Changer (OLTC) at the Step up Transformer is out of scope for this standard.

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Questions - MPs

• It would be helpful if the AESO can provide examples of types of applicable protection system devices at the technical work group session; as well as those not applicable devices.

[AESO] :

– An example of type of protections (ANSI Codes) covered under PRC-019 standard is shown on Slide #9 in red boxes. Depending upon type of excitation system , DC Overvoltage relays (59F) , DC Overcurrent relays (76) and Excitation Transformer Overcurrent (50/51ET) relay should also be coordinated with the limiters.

– MPs are expected to do engineering due diligence at their end to identify and report other protections which can be coordinated with the Voltage regulator/AVR limiters.

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Questions - MPs

• Request to add examples in the standard or via and Information Document to provide information similar to that communicated by NERC and IEEE.

– [AESO]: The AESO generally support NERC PRC-019-2 Section G. Reference “Examples of Coordination”. Additionally documents referenced on slide # 51 can also be referred to for PRC-019.

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Questions - MPs

• MP requests that the AESO provides further clarification regarding acceptable evidence. For instance, will the coordination be confirmed through a specific type of study, or documented evidence of verifying settings at a specific site?

– [AESO] : please refer slide # 35 of this presentation for the list of documents which can be submitted as evidence for the PRC-019 standard .

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Questions - MPs

• For 2(a): MP would like to request that the standard incorporates a longer interval to allow for coordination checks and implementation of any settings changes identified. We recommend the timing to be one year, or the next planned outage, whichever is sooner.

[AESO] :

– allow longer interval for coordination checks ;To be discussed !

– Improper coordination between protection and AVR’s Limiter can lead to tripping of the Generator during system disturbances (say tripping of Generator on a protection before a limiter gets a chance to act) and could create system reliability issues. Considering the criticality and potential impacts on the AIES, along with the NERC the AESO believes that such issues are to be attended to within 90 calendar days.

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Q & A’s

Additional Questions?

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References

• NERC Standard PRC-019-2 — Coordination of Generating Unit or Plant Capabilities, Voltage Regulating Controls, and Protection (https://www.nerc.com/pa/Stand/Reliability%20Standards/PRC-019-2.pdf)

• NERC Project 2007-09 Generator verification https://www.nerc.com/pa/Stand/Pages/Project2007-09-Generator-Verification.aspx

• IEEE Recommended Practice for Excitation System Models for Power System Stability Studies, IEEE Std 421.5.

• Requirements for Cylindrical-Rotor 50 and 60 Hz Synchronous Generators Rated 10 MVA and Above, ANSI/IEEE Std. C50.13.

• IEEE Guide for AC Generator Protection, IEEE Standard C37.102.

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Thank you