W E C C O A W G C O N F E R E N C E C A L L . A P R I L 8 , 2 0 1 9

S L A V A M A S L E N N I K O V

S M A S L E N N I K O V @ I S O - N E . C O M

PMU-Based Forced Oscillation Source Localization

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PMU Infrastructure at ISO New England

• 86 PMUs at 45 locations

• Full observability of 345 kV

• Seven open PDCs at TOs and one at ISO

• Selected PMU data from NYISO, PJM and MISO

• Operational since 2012

• PhasorPoint by GE is the main PMU application

NYISO

PJM

MISO

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Observed Oscillations

40 MW

Characteristics of 1000+ oscillatory events (statistics since 2012)

Property Description

Frequency 0,05 … 2 Hz

Damping 0 … 10 %

Magnitude 2 … 70 MW, RMS

Observability Local and Wide-spread

Duration From few seconds to hours

Overwhelming majority of evens are

Forced Oscillations

0.25 Hz

January 11, 2019: Forced oscillations caused by governor control failure of a Florida generator. Entire Eastern Interconnection was oscillating 17 min

MW flow in NYISO – ISO-NE

tie-line 1100+ miles away

from the source of oscillations

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Why do we need to mitigate oscillations?

• Sustained oscillations (forced and natural) impose a threat

Potential uncontrolled cascading outages

Undesirable mechanical vibrations in equipment

• The key step in the mitigating of sustained oscillations is to find the Source of oscillations. The Source is typically a generator

• The capability to find the Source online means providing an actionable information for mitigation

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Catastrophic consequences of rotor’s vibration2009 Sayano–Shushenskaya hydro power station accident *

• 75 people were killed• Widespread blackout• 6,400 MW power plant was out of service for 3 years• Critical damage to a generator was caused by Forced Oscillations (FO)

Before the accident After the accident

* https://en.wikipedia.org/wiki/2009_Sayano%E2%80%93Shushenskaya_power_station_accident

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Online Oscillation Management

PMU

Open PDC

Phasor Point

Alarm Notification Service

Triggered by Alarm

….

Objectives:• Detect all significant oscillatory events• Estimate the Source of oscillations• Deliver results to the designated personnel

ISO personnel• Operation Engineers• Control Room

PMU

PMU

Alarms

Oscillation Source Locating (OSL)

DetectionFinding the Source Mitigation

• Email• SMS

Generator Owner

Fully automated process; operational since September 2017

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Oscillation Source Locating (OSL) is the key application

• The OSL calculates the rate of change of Dissipating Energy (DEi ) for any branch ij

monitored by PMU at bus i.

• DE coefficient can be viewed as a regular MW flow in terms of Source-Sink for a flow of the transient energy: flows from Source to Sink

• The direction and the value of DE in multiple branches allow tracing the source of oscillations

MW flow in a transmission line Flow of Dissipating Energy in that line

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Interpretation of DE pattern

• PMU measurement at the Point Of Interconnection allows to trance specific power plant or generator

• PMU measurements of tie-lines between control areas allow to identify which area contains the source

• Even limited system observability by PMU allows greatly localize the suspect area

Source

Area A

Area B

Area C

Source

Sub 1

Sub 2Sub 3 Suspect area

DE flow

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• February 6, 2018; a large ISO-NE generator creates multi-frequency oscillations with magnitude up to RMS=3MW during 5 min

Time domain data Results of the OSL for 0.6Hz mode

This example illustrates the ability to identify an individual generator if it is monitored by PMU

FO Caused by ISO-NE generator

Combination of 0.60Hz and 0.86Hz modes

DE pattern for 0.86Hz is practically the same

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FO Coming From Non-Observable Area

• December 7, 2017; 1.3 Hz oscillations with RMS=5MW magnitude coming from the ISO-NE area not observed by PMUs

Results of the OSL

Not observed by PMU suspect area

• This area contains only 3 generators

• SCADA data for these 3 generates helps to find the source - generator

SCADA data for 3 suspect generators

This example illustrates the ability to localize the suspect area non-observable by PMU

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• 0.25 Hz oscillations with up to 200 MW peak-to-peak magnitude propagated through Entire Eastern Interconnection during 17 min

• The source of oscillations was a Florida generator having problem with the governor control

• Resonance conditions of 0.25 Hz inter-area mode caused the propagation of oscillations across entire EI

January 11, 2019 oscillation event

MW flow in 345 KV tie-line between NYISO and ISO-NE

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Oscillation Alarm Notifications via E-mail

• Designated personnel including Operation support engineers have received multiple emails during the event

• Each email contains

Characteristics of oscillations: magnitude, frequency, damping, location

Estimated Source: DE table, DE visualization, results of Pattern Recognition

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The content of E-mail

Results of DE pattern recognition• PMU only from ISO-NE footprint are used• That allows to identify that the Source:

Is located outside and In NYISO direction

Parameters of oscillations

DE in tabular form

DE visualization on oneline diagram

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DE Visualization on Oneline Diagram

New BrunswickN

ew

Yo

rk IS

O

• Each black arrow is a calculated DE

• DE pattern clearly shows that oscillations are coming from NYISO direction

• All Alarms for 1/11/2019 event contain practically identical DE pattern

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Consequences of the 1/11/2019 Event

• Before 1/11/2019, Oscillation Alarm Notification emails were sent to Operation support engineers only.

• After the event, Operations has requested

o To add the Control Room Shift Supervisor to the list of email recipients

o For a possibility to send also text SMS with Alarm notification

• Both requests were implemented

• Online Oscillation Management process was enhanced by adding the capability to send Oscillation Alarm Notification emails to generator personnel

o Due to confidentiality of information, specific generator can receive email related to oscillations caused by that generator only

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Source Identification Results

• Results are available online and provide key actionable information for mitigation

• The first key question is the Source located inside or outside of control area? The answer defines different set of actions

o For internal source: localize, eliminate, prevent the future occurrences

o For external: facilitate the elimination of the source in a suspect control area

• For January 11 event, results of OSL mean:

o Any action within ISO-NE cannot mitigate oscillations. Tripping of tie-lines will stop oscillations within area but is unreasonable

o Control Room should not initiate any actions within ISO-NE footprint to mitigate oscillations

o The best action is to call NYISO (suspect area) to verify their observations

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Statistics and Lessons Learned

• Online OSL has automatically processed 1000+ oscillatory events since September 2017. Correctly identified the source-generator/area for practically all instances of known source location

Each utility, having “OSL-like tool”, would be capable to independently estimate the Source of oscillations and greatly reducing the need in coordination with other utilities for mitigation

• Automated procedure for filtering and correcting bad PMU data is a must for robust online application

OSL Software

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• Developed by ISO-NE

o Online version is integrated with ISO-NE infrastructure

o Offline version reads PMU data from file and can be used with PMU data of any utility.

Several PMU data formats are supported

The software can be used as a research or fully automated tool

• ISO-NE can share the offline OSL software free of charge on request. Details will be available soon

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